compound curves in plywood

[BA-100]

I'm considering building a replica of a 30's glider that was originally
built in two halves, like a plastic model, but with pressed plywood halves.
Duplicating this has been outside the reach of a homebuilder without some
sort of press, and any made since have either been made out of fiberglass
or segments of scarfed plywood as were the prototypes. Here's a pic of one
here. The fuselage on the production originals was, as I say, made of
molded plywood in two halves and assembled over formers and stringers.
some of you might be familiar with the Bowlus Baby albatross.

http://www.fiddlersgreen.net/AC/aircraft/Bowlus-Sailplane/info/info.htm

My question is, would it be possible to laminate your own shell using
vacuum bagging? Seems to me even the wettest veneers would split if you
tried to force them into or around a male or female mold. to date, the only
sort of manipulation I've done with ply is to wrap 1/16 leading edge pieces
over a hot pipe. I just don't see how Hawley Bowlus got the compound
curves..


Any insights?

[Bob Kuykendall]

Earlier, BA-100 wrote:

> My question is, would it be possible to laminate
> your own shell using vacuum bagging? Seems to me
> even the wettest veneers would split if you tried
> to force them into or around a male or female mold.

Well, it's pretty easy to try it and see. Get some strips of thin
veneers (I'm thinking 1/64" to 1/32" or so) and try it out. For a test
part you can use any compound curved surface of about the curvature of
your porposed surface. I'd be inclined to try it out using VW beetle
(the old ones) fenders or roof sections from a junkyard. That'll give
you both internal and external test curve surfaces. If you can make
that work, it should give you enough experience and confidence to
proceed.

There are still folks around who know exactly how Bowlus made his
fuselage pods, it shouldn't be too hard to explore that. I believe that
Jeff Byard even has photos of the Bowlus tooling. There are also a
multitude of photos of the Lockheed Vega tools that used (I belive)
concrete molds and pressurized rubber bladders.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

[W P Dixon]

Luthiers commonly steam wood and form it over jigs, clamps hold it in place
until it drys out. May be the same kind of construction used to build this
sailplane. Just a thought and maybe something to check out.

Patrick
student SPL
aircraft structural mech

[BA-100]

"Bob Kuykendall" >
egroups.com:

> Earlier, BA-100 wrote:
>
>> My question is, would it be possible to laminate
>> your own shell using vacuum bagging? Seems to me
>> even the wettest veneers would split if you tried
>> to force them into or around a male or female mold.
>
> Well, it's pretty easy to try it and see. Get some strips of thin
> veneers (I'm thinking 1/64" to 1/32" or so) and try it out. For a test
> part you can use any compound curved surface of about the curvature of
> your porposed surface. I'd be inclined to try it out using VW beetle
> (the old ones) fenders or roof sections from a junkyard. That'll give
> you both internal and external test curve surfaces. If you can make
> that work, it should give you enough experience and confidence to
> proceed.

Sounds like a plan! I've located a place that sells bags for vacuum forming
that would certainly be big enough and I think Icould get an old compressor
to do the honors if I mess it around enough.
>
> There are still folks around who know exactly how Bowlus made his
> fuselage pods, it shouldn't be too hard to explore that. I believe that
> Jeff Byard even has photos of the Bowlus tooling. There are also a
> multitude of photos of the Lockheed Vega tools that used (I belive)
> concrete molds and pressurized rubber bladders.
>
> Thanks, and best regards to all

Yes, that's right, that's exactly how Bowlus did it. I did a lot of
research on it years ago when i started the project the first time around,
(even talked to the funder of a lot of Hawley Bowlus' creations, Steven
DuPont) but making a molded pod was pretty much out of the question at the
time. the preferable option was to do like they did with the protottypes
and pretty much every other glider of the period and make a series of
scarfed rings (why did i think this would be less work?) but when I found
out about vacuum bagging, I saw it as a possible way around this. A male
mold would be the easiest to build of course. I figure a series of ply
formers, filled in with foam and sanded to shape, then maybe a layer of
resin and voila, a half a fuselage. Has the aded advantage of being easily
replicated left and right.
If that didn't work, I suppose I could use that as a plug to make a female
mold out of concrete. (yipes, what would I do with it afterewards? ) and
use vacuum bagging on that.
Might actually give it a try...

[BA-100]

"W P Dixon" >
:

> Luthiers commonly steam wood and form it over jigs, clamps hold it in
> place until it drys out. May be the same kind of construction used to
> build this sailplane. Just a thought and maybe something to check out.
>

Yes, I've done this in fact. Have a guitar and a violin under my belt, but
no compound curves. Most flattop guitars have a small radius which is
compound, but nothing like what I'm talking about (a complete teardrop)
This sort of technology realy died out when fibreglass hit the scene,
though i'm sure there are some masters still around.Most likely source of
info are boatbuilders, of course, but their curves wouldn't even appraoch
the radius I'm talking about.....

[[email protected]]

I would guess that the construction techniques used
were similar to those used in boatbuilding.

http://www.albacore.org/USA/members/public/identifying_albacore.asp
http://www.boats.com/content/default_detail.jsp?contentid=1184
http://www.albacore.org/USA/members/public/identifying_albacore.asp
May help.

There is a remarkable wooden flying boat hull in the RAF Museum
at Hendon that was built in the early 1920s. It has a 'moulded'
hull which appears to have been constructed using boatbuilding
techniques of the time.

http://www.rafmuseum.org.uk/supermarine-southampton.htm

With its varnished finish it is simply stunning to
look at.

[BA-100]

egroups.com:

> I would guess that the construction techniques used
> were similar to those used in boatbuilding.
>
> http://www.albacore.org/USA/members/public/identifying_albacore.asp
> http://www.boats.com/content/default_detail.jsp?contentid=1184
> http://www.albacore.org/USA/members/public/identifying_albacore.asp
> May help.
>
> There is a remarkable wooden flying boat hull in the RAF Museum
> at Hendon that was built in the early 1920s. It has a 'moulded'
> hull which appears to have been constructed using boatbuilding
> techniques of the time.
>
> http://www.rafmuseum.org.uk/supermarine-southampton.htm
>
> With its varnished finish it is simply stunning to
> look at.
>
>

All good stuff, but not what I realy need to know. Rummaging around, I
found this, which is a bit enlightening..
http://personal.eunet.fi/pp/gsahv/torture/torture.htm

[Nafod40]

BA-100 wrote:
>
> My question is, would it be possible to laminate your own shell using

> vacuum bagging?

I would do some googling on "cold molding" and boatbuilding. Very
common method for building hulls. It's also how the SPruce Goose and
Mosquito bombers were built. You'd find...

http://www.nwmarinedesign.com/coldmold.htm

You can build up a structure as strong as fiberglass but lighter with
this technology.

http://www.glen-l.com/weblettr/webletters-6/webletter52.html#notebook

[Nafod40]

BA-100 wrote:
>
> My question is, would it be possible to laminate your own shell using

> vacuum bagging?

I would do some googling on "cold molding" and boatbuilding. Very
common method for building hulls. It's also how the SPruce Goose and
Mosquito bombers were built. You'd find...

http://www.nwmarinedesign.com/coldmold.htm

You can build up a structure as strong as fiberglass but lighter with
this technology.

http://www.glen-l.com/weblettr/webletters-6/webletter52.html#notebook

[Alan Baker]

In article . com>,
wrote:

> I would guess that the construction techniques used
> were similar to those used in boatbuilding.
>
> http://www.albacore.org/USA/members/public/identifying_albacore.asp
> http://www.boats.com/content/default_detail.jsp?contentid=1184
> http://www.albacore.org/USA/members/public/identifying_albacore.asp
> May help.
>
> There is a remarkable wooden flying boat hull in the RAF Museum
> at Hendon that was built in the early 1920s. It has a 'moulded'
> hull which appears to have been constructed using boatbuilding
> techniques of the time.
>
> http://www.rafmuseum.org.uk/supermarine-southampton.htm
>
> With its varnished finish it is simply stunning to
> look at.

Is everyone forgetting the deHavilland Mosquito? Constructed almost
entirely of cold-moulded plywood.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

[Morgans]

"BA-100" > wrote in message ...
> "W P Dixon" >
> :
>
> > Luthiers commonly steam wood and form it over jigs, clamps hold it in
> > place until it drys out. May be the same kind of construction used to
> > build this sailplane. Just a thought and maybe something to check out.
> >
>
> Yes, I've done this in fact. Have a guitar and a violin under my belt, but
> no compound curves. Most flattop guitars have a small radius which is
> compound, but nothing like what I'm talking about (a complete teardrop)
> This sort of technology realy died out when fibreglass hit the scene,
> though i'm sure there are some masters still around.Most likely source of
> info are boatbuilders, of course, but their curves wouldn't even appraoch
> the radius I'm talking about.....

The key to bending wood with steam is how hot it is. Superheated steam is
best, which takes a re-heater after the water is boiled. Make sure the
plywood is made with water proof glue, which is anything of A grade or
better, or marked withEXT after the grade. It might be B grade, but I don't
remember, right off.

For testing, that type of plywood is fine, but for building a plane, use at
least marine grade, and best is aircraft grade.
--
Jim in NC

[Morgans]

"Alan Baker" > wrote

> Is everyone forgetting the deHavilland Mosquito? Constructed almost
> entirely of cold-moulded plywood.
>
Isn't cold molding done using layers of wood, with glue applied as the wood
is bent in the mold, with the glue setting up in the new shape?
--
Jim in NC

[[email protected]]

BA-100 wrote:
>
> My question is, would it be possible to laminate your own shell using

> vacuum bagging?
------------------------------------------------------

Yes. But with a bit of fore-thought. My first effort at vacuum
bagging leading-edge skins ended up crushing my mold :-)

---------------------------------------------------

>Seems to me even the wettest veneers would split if you
> tried to force them into or around a male or female mold.

--------------------------------------------------------

Forming a compound curve, the plywood is usually HOT as well as wet,
and is remarkably plastic.

A standard technique in the repair of such structures offers a bit of
insight into fabricating such a hull from scratch. The general
procedure is as follows:

A mold is taken from the opposite side of the structure. (The
assumption here is for a symmetrical form). The mold is usually made
of plaster, stiffened with burlap or jute fiber and is a few inches
larger than the section to be replaced.

The plaster mold is used create a pair of re-enforced concrete molds,
much thicker than the plaster mold and usually in a frame of welded
steel angle-iron that has been previously drilled for bolts.

The concrete is wet-cured for about a week then air-dried in a warm
hangar for about ten days.

The plywood or veneer is boiled or steamed then laid into the mold,
which has been pre-heated to about 170*. If veneer, the usually
adhesive is a urea-formaldehyde type such as Weldwood 'Plastic Resin'
or resorcinol (the concrete mold must be protected). The upper part of
the mold is put in place and drawn down with bolts. The closed mold is
then returned to the oven or hot box and allowed to cure for 24 hours.

The resulting part is then scarfed to match the area to be repaired.

---------------------------

The point often overlooked is that this method may also be used for
scratch-building the entire pod. This is because the pod is
symmetrical. Other than the nose, which is usually carved from balsa,
you need only five or six molds to duplicate a longitudinal SLICE from
the pod. The builder simply makes eight copies of each panel then
scarfs them onto a frame.

It should also be apparent that this method works even better using
composite materials and vacuum-bagging, since you need only a few
pounds per square inch to cause the fiber & resin to conform to the
shape of the female mold (the male part is not required). Prior to
WWII there was considerable effort devoted to composite structures
including a few that actually flew (circa 1940) but they tended to be
heavier than their aluminum counterparts. I know the glider people,
but here (ie, Sandy Eggo) and Santa Monica had considerable success
using linen fabric, balsa cores and urea-formaldehyde 'resins.'

-------------------------------------

Although the Loughead brothers are often cited as the first to use the
laminated ply fuselage, there were some earlier airframes that
pioneered the process. I can't recall the details but 'LMB' comes to
mind; some outfit on the east coast, shortly after WWI. (I'm old. I
forget things and fart a lot.) This eventually lead to the patented
Duramold process which Howard used on the HK-1.

-R.S.Hoover

[Alan Baker]

In article >,
"Morgans" > wrote:

> "Alan Baker" > wrote
>
> > Is everyone forgetting the deHavilland Mosquito? Constructed almost
> > entirely of cold-moulded plywood.
> >
> Isn't cold molding done using layers of wood, with glue applied as the wood
> is bent in the mold, with the glue setting up in the new shape?

Yup. And the original post was talking about just that, ISTM.

"Seems to me even the wettest veneers would split if you
tried to force them into or around a male or female mold. to date,"

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

[Montblack]

("Morgans" wrote)
> For testing, that type of plywood is fine, but for building a plane, use
> at least marine grade, and best is aircraft grade.


"...and best is aircraft grade"

I know about marine grade plywood, but aircraft grade?

Speaking of marine grade plywood (I paid $77 w/tax for a sheet of 3/4" last
year) is there such a thing as marine grade + green treated that they sell?
That's what I wanted, couldn't find any. Something about varnish + green
preservative doesn't do well together I was told. (???)

It was for a carpeted-over floor in a 16 ft boat. We ended up spar
varnishing our sheet a number of times.


Montblack

[BA-100]

"Nafod40" >
egroups.com:

> BA-100 wrote:
>>
>> My question is, would it be possible to laminate your own shell using
>
>> vacuum bagging?
>
> I would do some googling on "cold molding" and boatbuilding. Very
> common method for building hulls. It's also how the SPruce Goose and
> Mosquito bombers were built. You'd find...

Yeah, knew that, though I'm not so sure it's suitable for this particular
airplane. Unfortunately, I've never seen one of the molded ones, only the
one in the NASM and that was built using scarfed rings. If I'm not
mistaken, the molded ones were made of single sheets of veneer made into a
ply in the mold, but I may be wrong about that.
>
> http://www.nwmarinedesign.com/coldmold.htm
>
> You can build up a structure as strong as fiberglass but lighter with
> this technology.

Mmm, that's the idea! Plus it just looks beautiful. I don't think they were
made in quite the same way as the cold molded boats are though.

[BA-100]

egroups.com:

>
> BA-100 wrote:
>>
>> My question is, would it be possible to laminate your own shell using
>
>> vacuum bagging?
> ------------------------------------------------------
>
> Yes. But with a bit of fore-thought. My first effort at vacuum
> bagging leading-edge skins ended up crushing my mold :-)
>
> ---------------------------------------------------
>
>>Seems to me even the wettest veneers would split if you
>> tried to force them into or around a male or female mold.
>
> --------------------------------------------------------
>
> Forming a compound curve, the plywood is usually HOT as well as wet,
> and is remarkably plastic.
>
> A standard technique in the repair of such structures offers a bit of
> insight into fabricating such a hull from scratch. The general
> procedure is as follows:
>
> A mold is taken from the opposite side of the structure. (The
> assumption here is for a symmetrical form). The mold is usually made
> of plaster, stiffened with burlap or jute fiber and is a few inches
> larger than the section to be replaced.
>
> The plaster mold is used create a pair of re-enforced concrete molds,
> much thicker than the plaster mold and usually in a frame of welded
> steel angle-iron that has been previously drilled for bolts.
>
> The concrete is wet-cured for about a week then air-dried in a warm
> hangar for about ten days.
>
> The plywood or veneer is boiled or steamed then laid into the mold,
> which has been pre-heated to about 170*. If veneer, the usually
> adhesive is a urea-formaldehyde type such as Weldwood 'Plastic Resin'
> or resorcinol (the concrete mold must be protected). The upper part of
> the mold is put in place and drawn down with bolts. The closed mold is
> then returned to the oven or hot box and allowed to cure for 24 hours.
>
> The resulting part is then scarfed to match the area to be repaired.
>
> ---------------------------
>
> The point often overlooked is that this method may also be used for
> scratch-building the entire pod. This is because the pod is
> symmetrical. Other than the nose, which is usually carved from balsa,
> you need only five or six molds to duplicate a longitudinal SLICE from
> the pod. The builder simply makes eight copies of each panel then
> scarfs them onto a frame.
>
> It should also be apparent that this method works even better using
> composite materials and vacuum-bagging, since you need only a few
> pounds per square inch to cause the fiber & resin to conform to the
> shape of the female mold (the male part is not required). Prior to
> WWII there was considerable effort devoted to composite structures
> including a few that actually flew (circa 1940) but they tended to be
> heavier than their aluminum counterparts. I know the glider people,
> but here (ie, Sandy Eggo) and Santa Monica had considerable success
> using linen fabric, balsa cores and urea-formaldehyde 'resins.'
>
>

Yipes. Getting complicated. Here was my plan:
Get a couple of 4x8 sheets of the thinnest stuff I could get, and lay them
over a male mold soaking wet but cold with a bit of ammonia thrown in for
good measure. Get a good coating of glue on the sheets and slip the whole
lot into the vac-bag. I-m pretty sure the original came in two halves, but
now you have me thinking it might be do-able if it was quartered
longitudanally.
just to give you all another look at one of these contraptions,
http://www.museumofflight.org/collections/craftdisplay.html?ID=32
as you can see, this one is also made of segmented, scarfed cones, but most
were made of two halved sides.
(at least i think they were halved, I have an original assembly manual for
one and that's the way the kit came)
unrealistic?

[Morgans]

"Montblack" > wrote in message

> Speaking of marine grade plywood (I paid $77 w/tax for a sheet of 3/4"
last
> year) is there such a thing as marine grade + green treated that they
sell?
> That's what I wanted, couldn't find any. Something about varnish + green
> preservative doesn't do well together I was told. (???)
>
> It was for a carpeted-over floor in a 16 ft boat. We ended up spar
> varnishing our sheet a number of times.
>
>
> Montblack

Yea, I know what you mean.

A friend wanted to do the same thing. We found a place that treats wood,
and got him to throw in some sheets of marine grade into his treating
thingy, the next time he was running a load. We then (after waiting for it
to dry out some) put it down and put a layer of fiberglass cloth and epoxy
over it all, before laying the carpet. It looks like new, about 5 years
later.
--
Jim in NC

[Highflyer]

> My question is, would it be possible to laminate your own shell using
> vacuum bagging? Seems to me even the wettest veneers would split if you
> tried to force them into or around a male or female mold. to date, the
> only
> sort of manipulation I've done with ply is to wrap 1/16 leading edge
> pieces
> over a hot pipe. I just don't see how Hawley Bowlus got the compound
> curves..
>

They used a boatbuilding and canoemaking technique that used bands of thin
veneer laminated over a male mould. The process is called "Cold Moulding"
and there are a couple of books about it in the "boatbuilding" section of
the library.

Essentially you build up a male plug with plywood formers covered with
fairly closely spaced strips of lath. The veneer thickness is selected to
give you an odd number of laminations, 3, 5, 7, etc. The bottom layer goes
on about forty five degrees to the lathing. Staple it down here and there
to hold it in place. It is wise to use heavy cardboard tags under the
staples because you are going to pull them out when you put the next layer
in place.

Brush the first layer with glue and cross it with the second layer at
something approximating 90 degrees. Aerolite glue works well. Brush the
cream component onto the first layer and then brush the hardener onto the
bottom of the second layer. Pull the staples as you go and restaple through
both layers.

The third layer goes on like the second, but aligned with the airflow so the
finished grain will be pretty! :-) Pull staples and staple it down as you
go.

After all the layers are down pull you vinyl over the whole banana and turn
on the vacuum pump to pull it all tight and hold it down.

If you want more than three layers of veneer repeat layers 1 and 2,
finishing with the top layer aligned with the airflow.

After the glue is hardened, remove the bag and sand the whole thing with a
random orbital sander to contour.

Standard industrial veneer for veneering furniture, etc. is 1/28 inches
thick. That is just under a millimeter for you continental folks. A three
layer veneer would be close to 3mm thick or a stout 1/8 inch. Be gentle
sanding because it is really easy to sand completely through a veneer layer
and get real embarassed!

Any stringers or frames are glued inside after the skin is finished. This
CAN be done without expensive or bulky tooling. The Dutch made fighters
using this technology in WWI.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

[Highflyer]

"Morgans" > wrote in message
...
>
> "Alan Baker" > wrote
>
>> Is everyone forgetting the deHavilland Mosquito? Constructed almost
>> entirely of cold-moulded plywood.
>>
> Isn't cold molding done using layers of wood, with glue applied as the
> wood
> is bent in the mold, with the glue setting up in the new shape?
> --
> Jim in NC
>

Exactly. Plywood is nothing but thin veneers of wood glued together face to
face with the grain running at different angles, generally ninety degrees,
but sometimes other angles for special applications. Plywood is normally
laminated on a flat plate making a flat sheet of wood that is very hard to
bend into anything other than a conical curve because the laminated layers
are glued together so they can't slide.

Cold Moulding is merely a low temperature process using ordinary waterproof
glues, for makeing you own plywood from thin veneers that is formed over
something other than a flat plate, so that it comes out with the shape of
the mould it was laminated in or on, as the case may be.

No reason in the world you can't make compound curved plywood by laminating
it up over a male plug and useing a vacuum bagging process to apply the
requisite clamping pressure. Ideally pick a good waterproof glue that gives
you a rather long working time and bonds well with a fairly low clamping
pressure. Say 5 to 10 pounds per square inch clamping pressure that you can
easily obtain with simple vacuum equipment. Working time of fifteen or
twenty minutes should allow time to build up thin laminations and get
clamping pressure onto them. This can be stretched a lot by using staples
with a pull pad under them to apply temporary clamping pressure as you build
up the lamination.

I have only done this using older glues like resorcinol and aerolite and
urea resin. I would think it would work very well with some of the more
modern epoxy based wood glues like T-88, etc. If it works for canoes, it
oughtta work for a Bowlus. :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

[flybynightkarmarepair]

As a naval architect, and at one time, a budding yacht designer, I've
got a lot of familiarity with "Cold Molding", which is the amateur's
version of the Lockheed process for making molded plywood shells.

The best book on the subject is "The Gougeon Brothers On Boat
Construction"
http://www.westsystem.com/webpages/productinfo/guide/index.htm#publications
http://www.amazon.com/exec/obidos/ASIN/0878121668/102-3874798-1028916

It's available in many libraries near the water, so you don't have to
run off and buy it yet. And you shouldn't, for once you realize how
much work this method will be for a One-off, you may, you should, think
twice.

Due to the small sized, and compond curves on the Baby Bowlus fuselage,
cutting and trimming the veneers is going to be your key challenge.
Each piece of veneer will need to be fitted to it's mate PRIOR to
gluing it up. All this hand work is why I don't think vacuum bagging
is going to buy you much on this project. You would have to vacuum bag
EACH piece of veneer seperately, clean up the glue squeze - out at the
free edge, and then fit the next piece of veneer. At least using this
method, you won't have to pull all the damn staples!!

I can easily see spending upwards of a 1000 hours just on the fuselage
alone, between building the male form, spiling (fitting) the veneers,
glue up (you need 3 layers), fairing, etc.

Some respondents have mentioned steam bending plywood. I've tried
that, and it's a non-starter, for the most part:
http://users.lmi.net/~ryoung/Sonerai/MySonIIL.html Scroll down to find
my tale of woe.

Note the mention of special "bending plywood". I got the stuff from
Woodline - The Japanese Woodworker in Alameda, California, it was
Italian Poplar, and was extremely easy to bend. This may offer you a
way out of a lot of labor, albeit at a high price in matierals. You
may be able to use ONE layer of this stuff, cut into "gores" and faced
inside and out with the lightest weight fiberglass and epoxy you can
manage. There is a similar product out of Gabon made with some
tropical hardwood, and a Hoop Pine product from Oz.

http://www.marineply.com/stagflex.htm
http://www.australply.com.au/pr_bendy.html
http://www.tapeease.com/plywood_panels.htm
http://www.lumberproducts.com/Products/Plywood/bendingplywood.htm

Good Luck,

[BA-100]

"flybynightkarmarepair" >
groups.com:

> As a naval architect, and at one time, a budding yacht designer, I've
> got a lot of familiarity with "Cold Molding", which is the amateur's
> version of the Lockheed process for making molded plywood shells.
>
> The best book on the subject is "The Gougeon Brothers On Boat
> Construction"
> http://www.westsystem.com/webpages/productinfo/guide/index.htm#publicat
> ions
> http://www.amazon.com/exec/obidos/ASIN/0878121668/102-3874798-1028916
>
> It's available in many libraries near the water, so you don't have to
> run off and buy it yet. And you shouldn't, for once you realize how
> much work this method will be for a One-off, you may, you should,
> think twice.
>
> Due to the small sized, and compond curves on the Baby Bowlus
> fuselage, cutting and trimming the veneers is going to be your key
> challenge. Each piece of veneer will need to be fitted to it's mate
> PRIOR to gluing it up. All this hand work is why I don't think vacuum
> bagging is going to buy you much on this project. You would have to
> vacuum bag EACH piece of veneer seperately, clean up the glue squeze -
> out at the free edge, and then fit the next piece of veneer. At least
> using this method, you won't have to pull all the damn staples!!



OK, I've never done anythng like that before (aside form planking models
when I was a kid) but it's close to what I reckoned was involved. I only
imagined that each srip might have to be trimmed to match it's neighbor,
and was hoping that it might not be so, and that someone here would tell me
some magic secret that would sail me right past that problem!
Oh well!

I can easily see spending upwards of a 1000 hours just on the fuselage
> alone, between building the male form, spiling (fitting) the veneers,
> glue up (you need 3 layers), fairing, etc.
>
> Some respondents have mentioned steam bending plywood. I've tried
> that, and it's a non-starter, for the most part:
> http://users.lmi.net/~ryoung/Sonerai/MySonIIL.html Scroll down to
> find my tale of woe.

Oh dear.
>
> Note the mention of special "bending plywood". I got the stuff from
> Woodline - The Japanese Woodworker in Alameda, California, it was
> Italian Poplar, and was extremely easy to bend. This may offer you a
> way out of a lot of labor, albeit at a high price in matierals. You
> may be able to use ONE layer of this stuff, cut into "gores" and faced
> inside and out with the lightest weight fiberglass and epoxy you can
> manage. There is a similar product out of Gabon made with some
> tropical hardwood, and a Hoop Pine product from Oz.
>
> http://www.marineply.com/stagflex.htm
> http://www.australply.com.au/pr_bendy.html
> http://www.tapeease.com/plywood_panels.htm
> http://www.lumberproducts.com/Products/Plywood/bendingplywood.htm
>
> Good Luck,
>

Thanks. I'm thinking if I get around to the Bowlus it'll have to be with
the scarfed pod,though!

[Bob Kuykendall]

Earlier, flybynightkarmarepair wrote:

> Due to the small sized, and compond curves on the Baby Bowlus
fuselage,
> cutting and trimming the veneers is going to be your key challenge.
> Each piece of veneer will need to be fitted to it's mate PRIOR to
> gluing it up...

I dunno about that, Ryan, I think you're making it a lot harder than it
was. Hawley and his crew weren't foolish, and they didn't have tons of
time to spare, and they stomped out dozens if not hundreds of Baby pods
in a relatively few short years. And they did it starting in the
Depression, so I think you'll find that they didn't have a lot of money
to throw at it.

I'm thinking that it doesn't necessarily take finely crafted and fitted
strips of veneer, and that the thing can be done with relatively wide
swaths of thin veneer if you've got enough pressure. Note that the Baby
pod has the very nose portion crafted in formed aluminum, and that the
compound curvature of the fuselage aft of that is relatively modest.

I agree that the pressures required to press the veneers into curvature
are probably greater than you can get with vacuum bagging, but at a
guess I'd say not hugely so. If I hankered for a Baby like the one I
watched rot away at Sky Sailing in the early 1980s, here's what I'd do:

I'd start by making a fuselage plug as I did for the HP-24 kit
sailplane (see http://www.hpaircraft.com/hp-24 specifically the 2001
Updates), or perhaps by planking a set of bulkheads. Then I'd dress it
with parting flange features and make right and left female molds of it
in the back yard using regular old concrete. After the concrete cures,
I'd pull the plug out, and then lay up Freeman tooling wax in the
female molds to the thickness of the expected plywood layup. And then,
I'd pour concrete into the tooling-waxed tubs to make male molds of the
inside of the fuselage.

To make the fuselage pod skin, I'd laminate relatively large swaths of
veneer with +/- 45 degree grain and press them between the male and
female mold parts. I'd press the male plug down using nuts on threaded
rods set into the flange of the female mold.

Sure, that plan is relatively time intensive, but the basic materials
are pretty cheap, and once you get the process figured out you can
bring your fellow Baby enthusiasts over to make their own pods before
you turn the tubs into planters or backyard barbecues. Just a thought.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

[nafod40]

Montblack wrote:
>
> Speaking of marine grade plywood

I just finished up a stitch-n-glue (4 mm plywood with single layer
fiberglass inside and out) kayak yesterday, and took it out for it's
maiden run at the local lake. It's 17' long, single seater sea kayak.
Weighs about 35 LBs, but can take an ocean entry driving out through
heavy surf, so it's not a frail structure.

While paddling around, I got to thinking about this thread, and
imagining wings either side of me, tail feathers behind...

A bright finished plywood glider would be a true thing of beauty.

[COLIN LAMB]

I have built a number of cedar strip canoes and kayaks, and the process is
simple and beautiful. Basically, thin cedar strips can be easily bent into
almost any shape, then glued together. Once the shape is completed, the
inside and outside is dovered with cloth and epoxy resin. In essence, the
cedar is simply the core (replacing foam). The strength is the inner and
outer layers of epoxy multiplied by the thickness of the cedar strips. The
epoxy is almost clear, so the beauty of the cedar shows through nicely. By
mixing up grains, patterns and colors, gorgeous boats result. They are very
light and strong. A cedar strip canoe properly built will weigh 50 pounds.

The same technique could be use for aircraft. I have taken my canoe through
rapids, over small water falls and survived collisions with rocks. The same
technique should work for a lightweight aircraft.

Colin

[COLIN LAMB]

I just looked at the fueslage of the Bowlus and it would be easily
duplicated using cedar strip techniques. Assembly is very quick with almost
no tools required, except for a saw to cut the wood strips. I did use some
mahogany in one of my canoes, just to try it, and it works fine. Because
the inside of the fuselage does not require the transparancy that the
outside does, you could even use one of the lighter and stronger cloths
(such as carbon fiber). This would result in increased strength and lighter
weight.

Now I may have to build one. The tube from front to rear could be
constructed easily using carbon fiber cloth rolled into a tube, or a
commercial tube purchased.

Colin

[Rich S.]

One of the Emeraude builders has constructed his gull-wing canopy using the
strip method. He has also built canoes in the past. There are some photos at
the Yahoo Emerauder's site http://asia.groups.yahoo.com/group/Emerauders/,
but you do have to sign up to see them. Look under "Photos" --->
"Construction projects" ---> "Canopy".

Rich S.

[BA-100]

"COLIN LAMB" >
thlink.net:

> I just looked at the fueslage of the Bowlus and it would be easily
> duplicated using cedar strip techniques. Assembly is very quick with
> almost no tools required, except for a saw to cut the wood strips. I
> did use some mahogany in one of my canoes, just to try it, and it
> works fine. Because the inside of the fuselage does not require the
> transparancy that the outside does, you could even use one of the
> lighter and stronger cloths (such as carbon fiber). This would result
> in increased strength and lighter weight.
>
> Now I may have to build one. The tube from front to rear could be
> constructed easily using carbon fiber cloth rolled into a tube, or a
> commercial tube purchased.
>

I sourced a tube for it years ago. Not a problem. If you really want one of
these beauties, the plans are available from the Vintage Soaring
Association! to the best of my knowledge, noone has yet finished a replica,
though.
The rest of the glider is pretty simple. It has a D-tube leading edge which
takes up most of the loads and a diagonal sub spar. The stab is all flying
and also is a D-tube structure. The original kit had a variety of ali
castings for wing fixing and such, but they're easily replaced with either
machined replacements or welded up 4130. The shell version would be
stronger and lighter as far as I can see, not to mention prettier!
Does the cedar strip technique you mention use multiple layers of veneer?
Presumably you need a form to wrap this around. Does it have to be solid or
can you just use formers, say, every 9 inches or so? How do you clamp to
get a good bond between layers?

[nafod40]

BA-100 wrote:
> Does the cedar strip technique you mention use multiple layers of veneer?
> Presumably you need a form to wrap this around. Does it have to be solid or
> can you just use formers, say, every 9 inches or so? How do you clamp to
> get a good bond between layers?

A different build method from cold moulding. Does not use veneers.
Here's a great site on the strip-built approach.

http://www.guillemot-kayaks.com/Building/StripBuilt/index.html

[Rich S.]

"BA-100" > wrote in message ...
<snip>
> Does the cedar strip technique you mention use multiple layers of veneer?
> Presumably you need a form to wrap this around. Does it have to be solid
> or
> can you just use formers, say, every 9 inches or so? How do you clamp to
> get a good bond between layers?

Years ago (1930's & 40's), my dad sponsored neighborhood kids for the Soap
Box Derby.

He had them use a form of this construction for the shell of their racers. A
couple of planks formed the bottom of the car and formers were fastened on -
the main ones being the "dash" to hold the steering column, and the seat
back. Then thin strips of cedar were tack-nailed on the plank and run up and
across the formers at a 45° angle (or so) and nailed to the plank on the
other side.

When one layer was complete, the wood was covered with strips of thin
canvas, saturated with glue. Then a second layer of wood was added, run in
the opposite direction.

The end result was a smooth, compound-curved, thin, light, streamlined shell
of a body.

Every racer who had my dad as a sponsor won the Pacific NW championship. But
that's another story. My dad discovered the secret to honestly and fairly
blow the doors off all the other racers. It involved a four-foot long
micrometer. . .

Rich S.

[Rich S.]

"Rich S." > wrote in message
...

> The end result was a smooth, compound-curved, thin, light, streamlined
> shell of a body.

Hah! I thought I had one - just one - picture around here someplace. You can
see it at http://tinyurl.com/4xqyw

Rich S.

[BA-100]

nafod40 > :

> BA-100 wrote:
>> Does the cedar strip technique you mention use multiple layers of
>> veneer? Presumably you need a form to wrap this around. Does it have
>> to be solid or can you just use formers, say, every 9 inches or so?
>> How do you clamp to get a good bond between layers?
>
> A different build method from cold moulding. Does not use veneers.
> Here's a great site on the strip-built approach.
>
> http://www.guillemot-kayaks.com/Building/StripBuilt/index.html
>

OK, now i'm totally confused! Most canoes i've seen seem to have their wood
running at about 45 deg. This looks pretty much just like strip planking
any boat!
I used to build models like this, using strips of balsa from nose to tail.
I've never seen a full sized aircraft using anything like this. Most seem
to use either sheets planked on formers, like many thirties glider like the
Minamoa or other european high performance saillanes of the thirties as
well as the Albatross of WW1, or the Lockheed method. (And BTW, the guy who
says the dutch built stressed ply airplanes for the Germans is a bit off
course, Tony Fokker only built those things under duress, he hated them and
didn't design them, rather, he and his chief dsigner, Rheinhold Platz,
developed the steel tube fuse we all came to know and love, but I digress)
There were a few inthe late thirties, notably the Timm aircraft and one
odball little twin, the Langley which used something called the "Vidal"
method of contstruction which apparently involved about 5,000 sq feet of
veneer and god knows how much resin to make one airplane. Pretty litle
thing

http://www.aerofiles.com/langley-twin.jpg
http://www.aerofiles.com/langley-twins.jpg

As you can see, the unpainted versions clearly show a 45 on all the wood
visible. Presumably, the underlying layers al go 90 deg to each other.
You gotta love the way the did the cowls out of wood as well!

http://www.aerofiles.com/langley-twins.jpg There's little doubt but that
this airplane would be nigh on impossible to build at home, but surely one
of these must be able to produce the simple teardrop that is the Baby's
pod. By the way, on the original, the teardrop is pure. That is, the fillet
between the teardrop pod and the wing was not all one piece. That fairing
is added on afterwards and is non-structural, which,it seems to me, would
simplify molding the pod no end.

[Alan Baker]

In article et>,
"COLIN LAMB" > wrote:

> I just looked at the fueslage of the Bowlus and it would be easily
> duplicated using cedar strip techniques. Assembly is very quick with almost
> no tools required, except for a saw to cut the wood strips. I did use some
> mahogany in one of my canoes, just to try it, and it works fine. Because
> the inside of the fuselage does not require the transparancy that the
> outside does, you could even use one of the lighter and stronger cloths
> (such as carbon fiber). This would result in increased strength and lighter
> weight.
>
> Now I may have to build one. The tube from front to rear could be
> constructed easily using carbon fiber cloth rolled into a tube, or a
> commercial tube purchased.
>
> Colin

You might want to explore this site:

<http://single-handedskiffs.com/pages/453349/index.htm>

That is a sailboat constructed along the lines being discussed. What's
interesting and germane to note is the *loads* on such a boat created by
the rigging. Typical standing rigging (that which holds up the mast) is
tensioned to hundreds of pounds, so you can get some idea of the loads
created between the rigging pulling upward and the mast pushing down.

There are some notes about the resin system used (from West, IIRC) and
some strength testing done on sample panels.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

[Alan Baker]

In article >,
"Rich S." > wrote:

> "Rich S." > wrote in message
> ...
>
> > The end result was a smooth, compound-curved, thin, light, streamlined
> > shell of a body.
>
> Hah! I thought I had one - just one - picture around here someplace. You can
> see it at http://tinyurl.com/4xqyw
>
> Rich S.

Forget that. I want the four-foot long micrometer secret!

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

[Rich S.]

"Alan Baker" > wrote in message
...
> In article >,
> "Rich S." > wrote:
>> Hah! I thought I had one - just one - picture around here someplace. You
>> can
>> see it at http://tinyurl.com/4xqyw
>>
>> Rich S.
>
> Forget that. I want the four-foot long micrometer secret!

How much energy is wasted while coasting over a thousand foot downhill
course if one (of four) wheels is one-thousandth inch out of alignment with
the other three?

Instead of expressing the loss in some esoteric unit of measurement, express
it in terms of "equivalent to pulling the racer X inches sideways".

How many builders align their wheels using a micrometer?

Rich S.

[UltraJohn]

BA-100 wrote:

> Does the cedar strip technique you mention use multiple layers of veneer?
> Presumably you need a form to wrap this around. Does it have to be solid
> or can you just use formers, say, every 9 inches or so? How do you clamp
> to get a good bond between layers?


http://www.oneoceankayaks.com/Kayaks.htm

The web site I was looking at for a kayak.

Yes to your question of formers Their plans give you full size former
layouts that you cut out put on the plywood and cut the formers from there.
They then attach the formers to a central beam and proceed to lay up the
wood strips using whatever wood to get the design they want mostly cedar
with mahogany for designs. after they do the top half they cover with
fiberglass and epoxy. They then remove from the formers (you did use
waxpaper on the formers right?) and fiberglass and epoxy the inside.
They then repeat with the bottom side. Then you fit the two sides together
and apply fiberglass tape and epoxy to both inside and outside of the
joint.
Basically instead of using foam for a core they use wood strips.

As soon as I finish this KR-2 in my garage (about another 10 years) I'm
going to start on my Cape Ann Double Kayak!

John

[UltraJohn]

COLIN LAMB wrote:

> I have taken my canoe through
> rapids, over small water falls and survived collisions with rocks. The
> same technique should work for a lightweight aircraft.
>
> Colin

Dang your brave I wouldn't want to do that in my airplane<G>!!

[COLIN LAMB]

Question: Does the cedar strip technique you mention use multiple layers of
veneer? Presumably you need a form to wrap this around. Does it have to be
solid or can you just use formers, say, every 9 inches or so? How do you
clamp to get a good bond between layers?

Response: Some of the cedar strip boats that I built were made from 1" x 6"
cedar planks, which means they were about 3/4" thick. Then I ripped those
planks on a saw (table saw, band saw or radial arm saw - whatever is handy).
This will give you long strips that are about 3/4" wide and 1/4" thick.
Cedar is used because it bends easily, looks good and is light. Stations
are built conforming to the curved shape you want. Each station is about
12" to 16" apart. Wax paper or tape are put over the plywood forms. The
first strip is installed, and following strips are glued adjacent to the
first step. The strips are stapled onto each form. Alignment between
stations can be assured by clamps over the strips you are gluing. The glue
does not matter, becase no strength comes from it. You can butt joint each
piece. Although some perfectionists angle the edges of the strips going
around a curve, it is not necessary. If there is a slight opening, epoxy
will seep in and make the structure stronger. The cedar simply replaces
foam, and the strength comes from the layers of cloth and epoxy resin.
Carbon fiber is stronger and lighter, but would cover up the beautiful cedar
strip finish, but could be used on the inside. Obviously, the application
and strength of the epoxy will control the strength of the overall
structure, but it can be quite high. The strength requirements for the
fuselage of something like a Bowlus would be quite low - but there would
obviously need to be some method of attaching the wings to the fuselage and
spreading out the stress of the lifting point.

However, the pod itself could be created similar to a cedar strip kayak. My
17 foot cedar strip kayak weighs about 50 pounds and I made no effort to
save weight.

One other process, which could be used is a process developed for the HK-1
Hughes "Spruce Goose" It is built of laminated birch. As I understand the
process, the it was plywood made in the shape required for the aircraft and
known as Duramold. The aircraft companies made a number of small boats
using the same process to perfect it. The Evergreen museum no doubt has
some information on the process.

The inventive can replace the Molt Taylor Aerocar of yesteryear with a
Glider/kayak. When making an outlanding, simply land by a lake ro river,
remove and store the wings and tail, and paddle home.

Colin N12HS

[Morgans]

"COLIN LAMB" > wrote

> I have built a number of cedar strip canoes and kayaks, and the process is
> simple and beautiful.

> The same technique could be use for aircraft. I have taken my canoe
through
> rapids, over small water falls and survived collisions with rocks. The
same
> technique should work for a lightweight aircraft.

One problem is that for an airplane, there are bunches of point loads, like
the spar, engine, and landing gear. There are also some wicked bending
moments involved. If you canoe breaks, you go swimming. If you airplane
breaks, you......
--
Jim in NC

[COLIN LAMB]

"One problem is that for an airplane, there are bunches of point loads, like
the spar, engine, and landing gear. There are also some wicked bending
moments involved. If you canoe breaks, you go swimming. If you airplane
breaks, you......"

No question the point loads are a big issue. However, it is the same issue
for those who build epoxy airplanes - because that is what a cedar strip
boat is really, an epoxy boat with a cedar core, instead of foam. All of
the cautions against cedar strip aircraft would apply to foam/epoxy
airplanes - yet there are a number of successful creations flying around.
The main difference is that you have to paint a foam/epoxy job because foam
is not intrisically beautiful - wood is.

I am not sure I advocate building a twin engined cedar strip fighter, but
the original query was regarding a Bowlus. It has no engine and the
strength demands are not nearly as great as a 10 G fighter.

Colin

[Morgans]

"COLIN LAMB" > wrote

>
> No question the point loads are a big issue. However, it is the same
issue
> for those who build epoxy airplanes - because that is what a cedar strip
> boat is really, an epoxy boat with a cedar core, instead of foam. All of
> the cautions against cedar strip aircraft would apply to foam/epoxy
> airplanes - yet there are a number of successful creations flying around.
> The main difference is that you have to paint a foam/epoxy job because
foam
> is not intrisically beautiful - wood is.

My concern is the fact that there is only one layer, or ply of wood. It
will have way less than 1/4 the strength than a craft with 2 plies of wood,
unless many more plies of fiberglass and epoxy are used. There is also no
resistance to twisting loads, without much more fiberglass. Another layer
of wood at between 90 and 45 degrees would make it much stronger in that
regard, also

The point loads in fiberglass airplanes are carried through strong
bulkheads, bonded very well to the body. I don't think what your describing
has that.

If the use of a single layer of wood is used to be the core, instead of
foam, and the same thickness of fiberglass is applied, as it would be in the
fiberglass and foam plane, there should not be a problem. Is this the
intent?
--
Jim in NC

[flybynightkarmarepair]

Bob Kuykendall wrote:
> Earlier, flybynightkarmarepair wrote:
>
> > Due to the small sized, and compond curves on the Baby Bowlus
> fuselage,
> > cutting and trimming the veneers is going to be your key challenge.
> > Each piece of veneer will need to be fitted to it's mate PRIOR to
> > gluing it up...
>
> I dunno about that, Ryan, I think you're making it a lot harder than
it
> was. Hawley and his crew weren't foolish, and they didn't have tons
of
> time to spare, and they stomped out dozens if not hundreds of Baby
pods
> in a relatively few short years. And they did it starting in the
> Depression, so I think you'll find that they didn't have a lot of
money
> to throw at it.

Well, they had some duPont money at least ;-)

Once you get the first one ship-set spiled out, you can use a router or
a shaper to chew out as many as you want, likety-split. And they had
the prototype to use as a full-size "tailer's dummy" to get a first
approximation of the shape of the veneers for the molded version -
neither advantage will apply to a one-off.

[flybynightkarmarepair]

OK, since there have been a LOT of questions about boatbuilding
technigues, I'll try and take them on.

* Angle of wood - old "wood and canvas" canooes DID have often have a
diagonal layer. "Strip Plank" canoes genearally do not, as they are
fiberglassed inside and out.
* Strip plank, general comment - this is a very labor intensive, and
relatively heavy way to build a canoe. The curvature in the bilge
areas is comparable to the Baby Bowlus, but the longitudinal curvaure
is greater, plus the substantial taper at both ends with drive you
bat**** trying to wrap the strips around that shape.
* Stitch and Glue is a GREAT idea for this project. Lightweight ply is
spiled over molds, and either tacked in place to the molds, or pulled
off the molds and stiched to the piece next to it, then taped along the
seams with fiberglass. It is even possible to "torture" a fair amount
of compound curve into the "gores" by cunning means describe in the
Gougeon book I mentioned previously. Lighter, quicker and cheaper than
the other methods, but not quite perfectly fair in all directions like
the molded alternatives.

I will NEVER build another strip plank boat, but I enjoy stich and
glue. YMMV....

[Dan, U.S. Air Force, retired]

COLIN LAMB wrote:

> Question: Does the cedar strip technique you mention use multiple layers of
> veneer? Presumably you need a form to wrap this around. Does it have to be
> solid or can you just use formers, say, every 9 inches or so? How do you
> clamp to get a good bond between layers?
>
> Response: Some of the cedar strip boats that I built were made from 1" x 6"
> cedar planks, which means they were about 3/4" thick. Then I ripped those
> planks on a saw (table saw, band saw or radial arm saw - whatever is handy).
> This will give you long strips that are about 3/4" wide and 1/4" thick.
> Cedar is used because it bends easily, looks good and is light. Stations
> are built conforming to the curved shape you want. Each station is about
> 12" to 16" apart. Wax paper or tape are put over the plywood forms. The
> first strip is installed, and following strips are glued adjacent to the
> first step. The strips are stapled onto each form. Alignment between
> stations can be assured by clamps over the strips you are gluing. The glue
> does not matter, becase no strength comes from it. You can butt joint each
> piece. Although some perfectionists angle the edges of the strips going
> around a curve, it is not necessary. If there is a slight opening, epoxy
> will seep in and make the structure stronger. The cedar simply replaces
> foam, and the strength comes from the layers of cloth and epoxy resin.
> Carbon fiber is stronger and lighter, but would cover up the beautiful cedar
> strip finish, but could be used on the inside. Obviously, the application
> and strength of the epoxy will control the strength of the overall
> structure, but it can be quite high. The strength requirements for the
> fuselage of something like a Bowlus would be quite low - but there would
> obviously need to be some method of attaching the wings to the fuselage and
> spreading out the stress of the lifting point.
>
> However, the pod itself could be created similar to a cedar strip kayak. My
> 17 foot cedar strip kayak weighs about 50 pounds and I made no effort to
> save weight.
>
> One other process, which could be used is a process developed for the HK-1
> Hughes "Spruce Goose" It is built of laminated birch. As I understand the
> process, the it was plywood made in the shape required for the aircraft and
> known as Duramold. The aircraft companies made a number of small boats
> using the same process to perfect it. The Evergreen museum no doubt has
> some information on the process.
>
> The inventive can replace the Molt Taylor Aerocar of yesteryear with a
> Glider/kayak. When making an outlanding, simply land by a lake ro river,
> remove and store the wings and tail, and paddle home.
>
> Colin N12HS
>
>
Sounds like some of the early Curtis flying boats. I think they'd be fun.

Dan, U.S. Air Force, retired

[COLIN LAMB]

"The point loads in fiberglass airplanes are carried through strong
bulkheads, bonded very well to the body. I don't think what your describing
has that.

If the use of a single layer of wood is used to be the core, instead of
foam, and the same thickness of fiberglass is applied, as it would be in the
fiberglass and foam plane, there should not be a problem. Is this the
intent?"

Yes! The cedar strips are simply space, rather than strength. The rigidity
comes from the 1/4" thickness of the cedar strips, plus the thickness of the
multi-layer epoxy coverings. My kayak has 3 layers of cloth on the
exterior, plus epoxy resin..The cedar strip is used for beauty and the
"plastic" ability to conform to compound curves. The strength comes for the
thickness of the cedar times the layers of epoxy - really like a foam
aircraft. Although additional strength could be gained by cross laminating
2 layers of cedar strips, it would also add to the weight - and the change
of delamination between layers may increase. Just as in foam airplanes,
bulkheads of other means of transferring stress from a single point to a
much larger area are necessary.

I have built a stitch-n-glue boat, also, but could never get the beautiful
compound curves that I could get from the cedar strips. There is a limit to
the bending.

I do think, though, that it would not be difficult to simply make a mold of
the shape desired and take very thin skins and make your own plywood,
conforming directly to the desired shape, much like the paper mache ugly
animals we made in grade school. Compound curves allow great strength with
thin materials.

Colin

[nafod40]

Rich S. wrote:
>
> How many builders align their wheels using a micrometer?
>

I do. I place the micrometer on the wheels, then get out the wheel
alignment tool (sledgehammer) and adjust...

[BA-100]

"Morgans" >
:

>
> "COLIN LAMB" > wrote
>
>> I have built a number of cedar strip canoes and kayaks, and the
>> process is simple and beautiful.
>
>> The same technique could be use for aircraft. I have taken my canoe
> through
>> rapids, over small water falls and survived collisions with rocks.
>> The
> same
>> technique should work for a lightweight aircraft.
>
> One problem is that for an airplane, there are bunches of point loads,
> like the spar, engine, and landing gear. There are also some wicked
> bending moments involved. If you canoe breaks, you go swimming. If
> you airplane breaks, you......


Well, in this case, there's no engine, of course, unless you count the
mounting of the pilot as a gravity engine.

The loads for the gear, strut points, wing attach and boom are all
distributed through formers, which are in turn held in place by the skin.
The alternative is 1/16 ply wrapped between each adjacent set of formers
and scarfed to it's neighbor, which doesn't appear to be any stronger than
a planked setup which basically amounts to a whole lot of stringers. They'd
have to be kept thin to keep the weight down, of course.

[Rich S.]

"nafod40" > wrote in message
...
> Rich S. wrote:
>>
>> How many builders align their wheels using a micrometer?
>>
>
> I do. I place the micrometer on the wheels, then get out the wheel
> alignment tool (sledgehammer) and adjust...

Remember - the micrometer has all those number thingys on the handle. The
C-clamp doesn't!

Rich S.
&-)

[BA-100]

"COLIN LAMB" >
thlink.net:

> "The point loads in fiberglass airplanes are carried through strong
> bulkheads, bonded very well to the body. I don't think what your
> describing has that.
>
> If the use of a single layer of wood is used to be the core, instead
> of foam, and the same thickness of fiberglass is applied, as it would
> be in the fiberglass and foam plane, there should not be a problem.
> Is this the intent?"
>
> Yes! The cedar strips are simply space, rather than strength. The
> rigidity comes from the 1/4" thickness of the cedar strips, plus the
> thickness of the multi-layer epoxy coverings. My kayak has 3 layers
> of cloth on the exterior, plus epoxy resin..The cedar strip is used
> for beauty and the "plastic" ability to conform to compound curves.
> The strength comes for the thickness of the cedar times the layers of
> epoxy - really like a foam aircraft. Although additional strength
> could be gained by cross laminating 2 layers of cedar strips, it would
> also add to the weight - and the change of delamination between layers
> may increase. Just as in foam airplanes, bulkheads of other means of
> transferring stress from a single point to a much larger area are
> necessary.
>

Ouch! 1/4 inch? All covered with resin this would be fairly heavy,
methinks. What does one canoe weigh? The fuselage would probably be roughly
double that, plus formers., hardware, ....

[BA-100]

"COLIN LAMB" >
thlink.net:

> Question: Does the cedar strip technique you mention use multiple
> layers of veneer? Presumably you need a form to wrap this around. Does
> it have to be solid or can you just use formers, say, every 9 inches
> or so? How do you clamp to get a good bond between layers?
>
> Response: Some of the cedar strip boats that I built were made from
> 1" x 6" cedar planks, which means they were about 3/4" thick. Then I
> ripped those planks on a saw (table saw, band saw or radial arm saw -
> whatever is handy). This will give you long strips that are about 3/4"
> wide and 1/4" thick. Cedar is used because it bends easily, looks good
> and is light. Stations are built conforming to the curved shape you
> want. Each station is about 12" to 16" apart. Wax paper or tape are
> put over the plywood forms. The first strip is installed, and
> following strips are glued adjacent to the first step. The strips are
> stapled onto each form. Alignment between stations can be assured by
> clamps over the strips you are gluing. The glue does not matter,
> becase no strength comes from it. You can butt joint each piece.
> Although some perfectionists angle the edges of the strips going
> around a curve, it is not necessary. If there is a slight opening,
> epoxy will seep in and make the structure stronger. The cedar simply
> replaces foam, and the strength comes from the layers of cloth and
> epoxy resin. Carbon fiber is stronger and lighter, but would cover up
> the beautiful cedar strip finish, but could be used on the inside.
> Obviously, the application and strength of the epoxy will control the
> strength of the overall structure, but it can be quite high. The
> strength requirements for the fuselage of something like a Bowlus
> would be quite low - but there would obviously need to be some method
> of attaching the wings to the fuselage and spreading out the stress of
> the lifting point.
>
> However, the pod itself could be created similar to a cedar strip
> kayak. My 17 foot cedar strip kayak weighs about 50 pounds and I made
> no effort to save weight.

I'm pretty sure that the process would be to heavy for the strength it
would provide, unless it were modified to provide several very thin
crossing layers, all of which woul have to be tightly glued to each other
to have any real strenght.
But an idea has just popped into my so-called mind..
If I were to make three mold of each side freehand over a male mold, each
90 deg to the last, and then take them and stack them over the same mold
and vacuum bag the whole lot together....

Hmm.

>
> One other process, which could be used is a process developed for the
> HK-1 Hughes "Spruce Goose" It is built of laminated birch. As I
> understand the process, the it was plywood made in the shape required
> for the aircraft and known as Duramold. The aircraft companies made a
> number of small boats using the same process to perfect it. The
> Evergreen museum no doubt has some information on the process.

This isn't to far off the original method of manufacture for the Baby as i
understand it.

>
> The inventive can replace the Molt Taylor Aerocar of yesteryear with a
> Glider/kayak. When making an outlanding, simply land by a lake ro
> river, remove and store the wings and tail, and paddle home.
>

Would have come in handy at least once in my gliding career when I left a
waterline on a 2-33!

[COLIN LAMB]

"Ouch! 1/4 inch? All covered with resin this would be fairly heavy,
methinks. What does one canoe weigh? The fuselage would probably be roughly
double that, plus formers., hardware, ...."

A 16 foot cedar strip canoe, with seats and all the trimming is under 50
pounds. Remember the resin is not just slopped on. The strength is from
the cross grains of the fabric used. This is very light. Just enough resin
is used to cover the fabric.

A one person kayak ought to have about the same total material as the Bowlus
fuselage and it would be about 40 pounds. The inside of the fuselage could
use carbon fiber or other cloth material, which is stronger and lighter (it
is opaque, so you would not want to use that on the outside). You could
probably use Kevlar on the inside, if you thought someone might be shooting
at your Bowlus. Attachment points would add weight, but the total weight
would still be reasonable.

My cedar strip canoe gets abused regularly. I have dragged it 1/4 mile over
a gravel bar. Once, when removing it from the top of my vehicle, a gust of
wind caught it and ripped it out of my helper's hands. The canoe came
crashing down on my vehicle, leaving a large dent in the vehicle, then
crashed to the asphalt. I inspected it and found no problems. We then
launched it and went 85 miles on a week long canoe trip. I do not abuse my
aircraft like I do my canoe.

Refinishing is easy. I once bet my neighbor I could refinish my 16 foot
canoe in less than 10 minutes. I sanded for 3 minutes, whisked off with an
old t shirt, then put an old white sock over a rubber glove and dipped it in
spar varnish, covering the entire canoe in about 4 minutes. I made the 10
minutes easily and, while not perfect, it looked good from 10 feet - and
ready to get abused again. And, I got a beer from my neighbor.

Colin

[UltraJohn]

>
> I'm pretty sure that the process would be to heavy for the strength it
> would provide, unless it were modified to provide several very thin
> crossing layers, all of which woul have to be tightly glued to each other

I'm no expert in (or any field) but several people have mentioned about the
lack of strength a single layer plywood would have and you'd need several
layers (ad various angles) etc etc. Yet the most common new "core"
constructions uses styrofoam for a core, I'd think the plywood at almost
any thickness would be stronger. The reason for use the plywood would be for
the looks (at least that's my guess).
John

[BA-100]

UltraJohn >
thlink.net:

>
>>
>> I'm pretty sure that the process would be to heavy for the strength
>> it would provide, unless it were modified to provide several very
>> thin crossing layers, all of which woul have to be tightly glued to
>> each other
>
> I'm no expert in (or any field) but several people have mentioned
> about the lack of strength a single layer plywood would have and you'd
> need several layers (ad various angles) etc etc. Yet the most common
> new "core" constructions uses styrofoam for a core, I'd think the
> plywood at almost any thickness would be stronger. The reason for use
> the plywood would be for the looks (at least that's my guess).

Well, ultimately the wood would be for looks. I could easily make a strong
fuse for this using plywood. While i was at it I could clean up the
aerodynamics and use carbon fibre for the wing spars. The added strength
would enable a longer, thinner wing and I could probably delete the struts
into the bargain! Thing is, it wouldn't be a Baby Albatross anymore. Ithink
you're confused about what is meant by single layer. A single layer
wouldn't be plywood, it'd be one layer of a sheet of plywood. It' be a ply
after layers were glued together. I can't see foam being used succesfully
as a core in this design either. Either I have to use the built up scarfed
panels method or figure a way to make a thin plywood teardrop with a farily
tight radius. Seems possible to make a three or four ply lamination using
single veneers set at angles to each other wrapping four inch or so veneer
strips over a male mold one at a time and trimming to match it's neighbor.

[BA-100]

"COLIN LAMB" >
thlink.net:

> "Ouch! 1/4 inch? All covered with resin this would be fairly heavy,
> methinks. What does one canoe weigh? The fuselage would probably be
> roughly double that, plus formers., hardware, ...."
>
> A 16 foot cedar strip canoe, with seats and all the trimming is under
> 50 pounds. Remember the resin is not just slopped on. The strength
> is from the cross grains of the fabric used. This is very light.
> Just enough resin is used to cover the fabric.
>
> A one person kayak ought to have about the same total material as the
> Bowlus fuselage and it would be about 40 pounds. The inside of the
> fuselage could use carbon fiber or other cloth material, which is
> stronger and lighter (it is opaque, so you would not want to use that
> on the outside). You could probably use Kevlar on the inside, if you
> thought someone might be shooting at your Bowlus. Attachment points
> would add weight, but the total weight would still be reasonable.
>
> My cedar strip canoe gets abused regularly. I have dragged it 1/4
> mile over a gravel bar. Once, when removing it from the top of my
> vehicle, a gust of wind caught it and ripped it out of my helper's
> hands. The canoe came crashing down on my vehicle, leaving a large
> dent in the vehicle, then crashed to the asphalt. I inspected it and
> found no problems. We then launched it and went 85 miles on a week
> long canoe trip. I do not abuse my aircraft like I do my canoe.
>
> Refinishing is easy. I once bet my neighbor I could refinish my 16
> foot canoe in less than 10 minutes. I sanded for 3 minutes, whisked
> off with an old t shirt, then put an old white sock over a rubber
> glove and dipped it in spar varnish, covering the entire canoe in
> about 4 minutes. I made the 10 minutes easily and, while not perfect,
> it looked good from 10 feet - and ready to get abused again. And, I
> got a beer from my neighbor.


Hmm, i'd have to experiment with that one a bit.
It doesn't sound right to me, but I'm prepared to be amazed! God knows it's
happened to me plenty of times before...

[Ed Sullivan]

On Mon, 11 Apr 2005 23:47:53 -0400, "Morgans"
> wrote:

>

>> is not intrisically beautiful - wood is.
>

How about a normal composite layup with a mahogany veneer on the next
to last layer covered by fiberglas for pretty.

Ed Sullivan

[LCT Paintball]

> How about a normal composite layup with a mahogany veneer on the next
> to last layer covered by fiberglas for pretty.
>
> Ed Sullivan
>

That's interesting.
I've read that most composites must be painted white to reflect heat that
could damage the foam. Do you think you could get by without the white
paint?

[Bob Kuykendall]

Earlier, LCT Paintball wrote:

> That's interesting.
> I've read that most composites must be painted
> white to reflect heat that could damage the foam.
> Do you think you could get by without the white
> paint?

Well, there are resins available that will take the heat. The trouble
is that they're not commonly used in the home workshop environment.
High-temp epoxies tend to require special high-temp curing. I think
there are also vinylesters that take high temps okay, although I
understand they can be tricky to work with. They also eat styrofoam, so
you can't use them on Rutan-type construction.

And, like you say, styrofoam also has a fairly low service temperature.
But other core foams like Divynicell (rigid PVC) does come in
high-temperature formulations, and is compatible with vinylester.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

[COLIN LAMB]

The greatness of the Wright Brothers was that they were not limited by what
they did not know.

The Bowlus was a unique approach to flight, The design lends itself to
learning skills to make a modern replacement using either rekindled or
entirely new process.

Colin

[BA-100]

"COLIN LAMB" >
thlink.net:

> The greatness of the Wright Brothers was that they were not limited by
> what they did not know.
>
> The Bowlus was a unique approach to flight, The design lends itself
> to learning skills to make a modern replacement using either rekindled
> or entirely new process.
>

True, vbut it wasn't exactly groundbreaking technology in 1938, either. A
modern replacement's been done. I want a fairly close replica.. When i
talked to Steven DuPont abou tit, he said "What do you want to build a
piece of **** like that for? I'm building an HP18! Build one of those."