Metal vs Wood or T2 vs VP (Part II)

On Mar 29, 12:54*pm, Bob Hoover wrote:
On Mar 29, 9:17*am, Copperhead wrote:

Oddly enough I've had more fun researching and experimenting with
plans and parts building then I'd ever have thought possible and have
spent very little money so far. Mostly this has been due to the fact I
already have most of my woodworking power tools as well as a lot of
metal cutting and bending tools.

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Dear Joe,

Normally, when you have the option of building from either aluminum or
wood, you would opt for metal but there are a few cases where wood may
prove to be the better choice. *In the mid-1930's Virginias Clark, the
fellow who gave us the Clark-Y airfoil, patented a process of making
plywood called 'Duramold' that was superior to aluminum in several
ways, but especially with regard to compound curves. *Howard Hughes
acquired the rights to the process (I believe through Fairchild
Camera) and used it to produce the HK-1 'Hercules' *-- *which we
generally know as 'the Spruce Goose,' even though it is mostly birch.
The 'K' part of 'HK' referred to Henry J. Kaiser, who was supposed to
assemble the giant flying boat, Hughes to fabricate the parts.

One reason we've never heard much about Dura-mold is because of
fiberglas.... and a small Swiss company that came up with epoxy.
Combine the two and even a back-yard craftsman has the ability to
produce complex parts stronger than steel but weighing as much as two-
thirds less.

-Bob

PS -- I've got a hunch that threads such as this often turn into
something useful.

Bob,

I’d read about the composite construction techniques of the ill named
“Spruce Goose”, but never made a correlation with respect current
fiberglass composite aircraft. Merely at a guess, it would appear that
one would need to make they’re own “duramold” ply (glass) wood while
constructing an airframe.

I certainly agree that such a practice would eliminate the need for
applying fiberglass to foam for panels or coverings. Current vacuum
bagging practices used on KR’s with hand made mold would most
certainly work. Now I’m going to have to do some research and
experimentation to see what epoxy and wood veneer bond together best.

For this, I believe the local boat builder’s and marine plywood supply
distributors are going to be a good information source. I think your
right about the weight savings coupled with enhanced strength of such
a project. It also looks like it would eliminate a lot of glass cloth
as well as grinding and sanding. Very interesting and informational,
thanks.

Regards

Joe S.

On Mar 29, 11:45*am, Copperhead wrote:

I’d read about the composite construction techniques of the ill named
“Spruce Goose”, but never made a correlation with respect current
fiberglass composite aircraft. Merely at a guess, it would appear that
one would need to make they’re own “duramold” ply (glass) wood while
constructing an airframe.
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Dura-mold used a 'resin' similar to Plastic Resin Resorcinol in
APPEARANCE (or so I'm told; second-hand information coming at you
here). That is, there was a powder and a liquid which had to be mixed
according to a critical ratio. The wood was then impregnated with the
resin using a lay-up process similar to doing a boat hull. cabin tops
or what-have-you... with one critical exception. It was a CLOSED mold
-- you had to get the lid on the thing -- and the cure was done using
HEAT. In this case, steam or hot water.

The molds could be concrete & hot water -- and most of them were --
but some parts used ALUMINUM molds and electrical or steam heat.

Hughes ponied up an incredible amount of cash to resolve a lot of
unforseen problems relating to serial production, producing panels of
larger size, attaching panels together ...ever heard of FPL-16a
(HUGHES GLUE) ? Once all the bugs were out of the production process
you start popping HK-1's out of ship yards on both coasts at a
guesstimated rate of thirty PER DAY. And of those eight humongous
engines, it took only FOUR to FLY the thing... but all EIGHT were
needed for a fully-laden take-off

The deal with fiberglas & epoxy was that it weighed less and was
stronger than Dura-mold, plus you could formulate it for room-
temperature curing. All of that development work -- and all of that
MONEY -- had been overtaken by events.

(So what was the big flap between Hughes and the government? Hughes
had a piece of paper signed by 'the government' that said they would
pay ALL COSTS incidental to production of the HK-1, which the Hughes
lawyers read to mean all those bucks spent in development work. The
Government disagreed, saying they meant the cost of setting up
production facilities, NOT costs associated with basic research. Plus
there were more than a few Congressmen who kept pointing out that the
thing had not actually FLOWN... that it might be nothing more than a
bogus scheme to screw the American tax payer, yada yada yada...

Hughes won, by the way. But it was often said that he spent more on
legal fees than he recovered.)

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I certainly agree that such a practice would eliminate the need for
applying fiberglass to foam for panels or coverings.

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

I'm not sure why it is, but a lot of people seem to think that mold-
less composite work was something new; that Kenny had come up with a
better mouse trap. In fact, that method of fabrication has been in
use for literally THOUSANDS of years. Although I wasn't around back
then (despite what you may have heard...) they have found numerous
examples of PLYWOOD in Egyptian tombs and the re-curve bow used by
Genghis Khan's mounted troops was of mold-less composite structure.
Closer to home, when tasked with producing 1200 sets of Roman-era
armor for the movie 'Ben Hur,' the set designers cranked them out
using paper mache. But of more practical use, it was fairly common
for fishermen to re-enforce spars and booms using canvas & varnish.

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Current vacuum
bagging practices used on KR’s with hand made mold would most
certainly work. Now I’m going to have to do some research and
experimentation to see what epoxy and wood veneer bond together best.

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

Homebuilders could turn out some damn good airplanes on the cheap if
we can come up with a mini-production line for vacuum bagging leading-
edge sections for a couple of standard airfoils, such as 4412, 4415 or
the M6, in lengths of about 48 inches. Properly done, the section
gets peel-ply'd on the interior and the edges get stepped. It locks
you into a rectangular plan-form but you can come up with a good D-
cell, allowing you to produce a really good wing.

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

For this, I believe the local boat builder’s and marine plywood supply
distributors are going to be a good information source. I think your
right about the weight savings coupled with enhanced strength of such
a project. It also looks like it would eliminate a lot of glass cloth
as well as grinding and sanding.

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

The information everybody wants is out there but it's fragmented.
Unfortunately the only body that claims to speak for the lowest level
of aviation in America -- logically the organization that should
concern itself with such matters -- has not.

-Bob

On Mar 29, 7:04*pm, Bob Hoover wrote:

Homebuilders could turn out some damn good airplanes on the cheap if
we can come up with a mini-production line for vacuum bagging leading-
edge sections for a couple of standard airfoils, such as 4412, 4415 or
the M6, in lengths of about 48 inches. *Properly done, the section
gets peel-ply'd on the interior and the edges get stepped. *It locks
you into a rectangular plan-form but you can come up with a good D-
cell, allowing you to produce a really good wing.

I've had similar thoughts and have done some small experiments with
the TPG process. Haven't yet found the right core material. High
density PVC foam looks promising in place of Taylors paper. I have
some to play with but started projects must be completed first.

As for being "locked" into a rectangular plan-form, I'm not so sure.
There seems to be enough flexibility in the formed leading edges to
squish them down a bit after cure. The leading edge radius stays
larger then a full scaling down but that might work out to be an
advantage when it comes to tip stall?

While I'm thinking about it - vacuum sources. Mine is a water bed
drain tool. Works great and cost little. Set it up on the lid of a
Rubbermaid type tub of water with a small recirculating pump and you
have an inexpensive and reliable source of vacuum. When your finished
everything stores in the tub for the next use. Just remember to put a
check valve on the outlet or you risk sucking in water if the power or
pumps prime gets interrupted. A good source of check valves ... power
brake hose from about any salvage auto. For vacuum control a fish
tank air valve works well enough.
==============================
Leon McAtee

On Sat, 28 Mar 2009 12:59:11 -0700 (PDT), "
wrote:

snip

As for the airframe, the selection is based on the availability of the
required TOOLS and before we get into the issue of tools too deeply it
must be understood that regardless of your choice SOME tools will be
required.

Bob...I wish it were that simple. I do well with metal, but I am the
world's worst carpenter. I'd need a shop full of precision tools just
to cut a board straight.

I had to route one 3/4" groove 1/8" deep and three 1/2" wide by 1/8"
deep. It took three pieces of good Oak plywood to get it right...OK,
there apparently isn't any such thing as good plywood any more, but it
still took 3 pieces.

All of the METAL airframes mentioned mentioned above can be built
using ONLY hand tools, whereas for the 'wooden' airframes, a table saw
is a virtual necessity.

Using a fence and guide carefully set to square and I'm still off by
over an 1/8" in 16"

Fortunately a portable electric saw may be
pressed into service as a TABLE SAW at a very small price, allowing
accurate production of the required longerons and, in the case of a

If I'm off by an 1/8" in 16" with a table saw you can imagine what
happens with a portable...:-)) OTOH, the wandering back and forth
might "average out" to much less.

'Chugger' type wing, of the sticks needed for ribs.

Performance on the whole is left for future posts but one aspect of
performance must be addressed at the outset and that is the
relationship between flying and safety. To be a good airman, in my
opinion, DEMANDS a given number of landings per month. Ideally, a
group of airmen would keep one or more airframes available to all.
I'm not strong on clubs, having found most degenerate fairly quickly
by non-flying types who see the club as a SOCIAL activity and who tend
to lean their financial shoulder rather heavily on those who are
primarily interested in FLYING rather then dunking their donuts. Yet
it's difficult to define the needed group without making it sound like
a club.

In the two groups I've been in as well as on other locally the non
flying members end up footing a good portion of the bill so the more
we have who don't fly the cheaper it is for those of us who do. IOW
there is a Membership charge, monthly charge, and hourly charge with
the occasional special charge. These were all "up front" so any who
join are made well aware of what they will be asked to support.


As for doing all of the flying in just one or two airframes, this
reflects the COST of hangars and tie-downs. All of the airplanes
discussed here can be road-towable but in a growing number of cases
the folks running our airports are AGAINST someone flying out of
'their' field unless they pay certain fees. I've nothing against
that; we've all got to eat. But I AM against being forced to pay
hundreds of dollars a month simply to maintain my proficiency. My
suggested solution is to base one or two airplanes at such airport but
to allow those airplanes to be flown by OTHER-THAN their registered
owner.

A couple of people have said it sounds as if I am AGAINST the social
aspects of grass roots aviation. Actually, I'm just the opposite.
What I'm against is some ground hog trying to run us through the
financial wringer simply because we happen to own an airplane.

But what I'm also against is the pilot whose only flight experience is
gained to and from an airshow. Or having them look like duffers when
they are told to land long, or to put it on the green or whatever.

You just listed about 90% of the private pilots. Of course I've not
been flying for the past two years (do hope to get the medical back
soon and flying even sooner), but when my flying was only 20 hours a
year for a couple of years, all of that 20 hours was spent in
practice. To me, proficient means "flexible". As you say, being able
to spot land with what ever I'm flying, or fly an "Oshkosh pattern"
where they tell you what to do, when and where as well as to be able
to "keep the speed up" following the G-III or S-turn behind a Cub
while close to minimum *safe* airspeed.

I have to admit that I like to practice "hanging on the edge" be it
stall, MCA, 60 degree steep turns, turns on, or around a point, or
having some one tell me "turn base now and land on a specific spot be
it the numbers, or where ever.

Actually I have to admit there's a bit of ego in landing a Bo in way
less space than the other guys use for 172s, 150's, and Cherokees.
OTOH I don't add 10 MPH for a cushion, another 10 for mother and the
kids, and maybe another 10 for what ever reason. The ASF made us
calculate the speed for every landing based on weight and we were
given IIRC +/- 2 MPH.

Toward that end I would like to see them practicing precision landings
at some low-traffic field... or at ANY field, when it comes right down
to it. (It is the organization needed for this type of practice that
leads to the 'club-like' definition.)

I do them just for personal satisfaction.


While none of the planes mentioned here are especially hot STOL
performers, neither do they need a mile of concrete. Without
exception, all can do a full-stop in less than a thousand feet... and
the touch-and-go needed for a spot landing can be done in much less.

You can do that in a Bonanza as long as you don't try to pull the
power and glide in. It takes a lot more runway when you do that. BUT
all that practice paid off when the old Deb had a complete engine
failure on climb out. Bout 50 feet or so and 100 MPH when it got real
quiet. On a 3800 foot runway I barely had enough energy left in the
old gal to make the turn off at the terminal building and there was
1200 feet of runway left. If you have the power, come in steep, don't
drag it in. The F33s and Debs and easily land over the 50 foot
obstacle in less than 1000. Actually if there is any breeze at all
it'll be less than 900 feet. That big wing has the same loading as a
Cherokee 180 and more drag with those big flaps. Actually with gear
and flaps down it flies like a big, heavy, expensive Cherokee 180 that
uses a lot of gas. Well, it's not nearly as forgiving with stalls in
that configuration either. :-))

BTW I *enjoy* practicing and doing all those maneuvers, but I may have
to start looking for something that uses a bit less gas for just
playing.sigh





The point here is that your decision to build a 'wooden' or a metal
airplane depends largely on what TOOLS you have. But the wood vs

For me, lack of skill might have to be factored in when it comes to
wood.

Which reminds me, it's time to get back to the router out there in the
shop.
metal argument has no merit because because when it comes to tools --
and that's what it boils down to -- the ENGINE requires more tools
than either type of airframe.

Tools, I can use...but you use tools other than wrenches on an engine?
:-))


-R.S.Hoover