Wooden Fuselage Gussets

[......... :-\)\)]

There are many homebuilts that have open truss type wooden fuselages built
from square spruce sticks joined with plywood gussets. Typically the gussets
are 1/8" plywood. Aircraft such as the Cavalier, Termite, Pietenpol.
Somethings bugging me ....

When it comes time to cover the fuselage what is the normal method used to
fair the plywood gussets so that they arn't visible through the fabric. I
have consulted the plans for a number of these aircraft and they don't say
what to do .....

Has anyone built a fuselage like this who can tell me how to deal with this
?

[Ed Sullivan]

On Sat, 6 Aug 2005 22:32:38 +1000, "......... :-\)\)"
> wrote:

>There are many homebuilts that have open truss type wooden fuselages built
>from square spruce sticks joined with plywood gussets. Typically the gussets
>are 1/8" plywood. Aircraft such as the Cavalier, Termite, Pietenpol.
>Somethings bugging me ....
>
>When it comes time to cover the fuselage what is the normal method used to
>fair the plywood gussets so that they arn't visible through the fabric. I
>have consulted the plans for a number of these aircraft and they don't say
>what to do .....
>
>Has anyone built a fuselage like this who can tell me how to deal with this
>?

Most have a couple of fairing strips on edge along the sides and
bottom in a couple of places.. In the case of mine there was also a
1/8 thick strip of spruce about a half inch wide added to the side and
bottom of the longerons between the gussets. They and the gussets are
then sanded to a slightly rounded profile so the fabric lies smoothly
over them.

Ed Sullivan, Jungster II

[Rich S.]

"......... :-))" > wrote in message
u...
> There are many homebuilts that have open truss type wooden fuselages built
> from square spruce sticks joined with plywood gussets. Typically the
> gussets
> are 1/8" plywood. Aircraft such as the Cavalier, Termite, Pietenpol.
> Somethings bugging me ....
>
> When it comes time to cover the fuselage what is the normal method used to
> fair the plywood gussets so that they arn't visible through the fabric. I
> have consulted the plans for a number of these aircraft and they don't say
> what to do .....
>
> Has anyone built a fuselage like this who can tell me how to deal with
> this

When building a vooden airplane, there is always the problem of left-over
glue in the bottom of the cup. It is foolish to mix to little glue and try
to stretch it, so you end up mixing too much.

The solution is to have pre-cut strips of scrap plywood at hand. To use up
the glue, cut a strip of plywood to length to fit between two gussets and
glue it in place.

Oh, 1/8"?? What are you building, a DeHavallind Mosquito? Planes the size of
an Emeraude or Cavalier use 2 mm plywood if it's Okume or 1.5 mm Finnish
Birch.

BTW, the Emeraude plans say to taper the edges of the gussets, but it does
look better to my eye to add the filler strips.

Rich S.

[UltraJohn]

> The solution is to have pre-cut strips of scrap plywood at hand. To use up
> the glue, cut a strip of plywood to length to fit between two gussets and
> glue it in place.
>
> Oh, 1/8"?? What are you building, a DeHavallind Mosquito? Planes the size
> of an Emeraude or Cavalier use 2 mm plywood if it's Okume or 1.5 mm
> Finnish Birch.
>
> BTW, the Emeraude plans say to taper the edges of the gussets, but it does
> look better to my eye to add the filler strips.
>
> Rich S.


An extra oz. here and and extra oz. there and oh yeah this addition would be
nice! All of a sudden the plane weighs 20% over design empty weight! ;-)
If the plans say taper your probably best tapering.

John
(just 2 cents worth!)

[Rich S.]

"UltraJohn" > wrote in message
ink.net...
>
> An extra oz. here and and extra oz. there and oh yeah this addition would
> be
> nice! All of a sudden the plane weighs 20% over design empty weight! ;-)
> If the plans say taper your probably best tapering.

I agree 100%, John. In my particular case, because of engine selection, the
longerons needed a skosh more thickness. My aero design engineer pal
suggested that the gap fillers would do the job. I still ended up below
average weight for the genre.

Rich S.

[Ed Sullivan]

On Sat, 06 Aug 2005 16:23:09 GMT, UltraJohn >
wrote:


>An extra oz. here and and extra oz. there and oh yeah this addition would be
>nice! All of a sudden the plane weighs 20% over design empty weight! ;-)
>If the plans say taper your probably best tapering.
>
>John
>(just 2 cents worth!)
>
Actually all the measures I described in my post were according to
plans and the aircraft is quite light.

Ed Sullivan

[Lou]

For another 2cents worth, my plans called for the wooden gussets only
on one side. The other side is to be covered with plywood instead of
fabric.
Lou

[Richard Lamb]

Drifting - slightly - I'm currious about the following...
I was thinking about routing off the sharp edges of exposed vertical
and diagional
members. Now this would be for edges not in contact with skin or
gussets.
Maybe 1/8 or 3/16 radius router.

And I'd not try it on longerons (chicken).

But rounding off the square edges of the wood seems like a reasonable
weight reduction idea.

Ok, maybe it's just a few ounces involved, but -
1) reducing is mo better than adding
2) the squared off edges don't carry much - if any - load.
3) rounded edges are less susceptible to damage (splinters?)

Comments?

Richard

[[email protected]]

This was a standard procedure on many early Fokker & de Haviland-type
fuselages (ie, plywood shear-web & wooden structural members), although
most were chamfered rather than routed. While there is some reduction
in weight, knocking off the corners reduces the surface area of the
exposed portion of the structural member, requiring less varnish.
Elimination of the corners also reduces the tendency for brashness or
splintering common to Douglas Fir.

In a similar vein, that odd green tint seen in the varnish on the
inside of early wooden airframes came from an anti-fungal agent, added
to the varnish to prevent the biological degradation of the
casein-based glue.

-R.S.Hoover

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

wrote:
> This was a standard procedure on many early Fokker & de Haviland-type
> fuselages (ie, plywood shear-web & wooden structural members), although
> most were chamfered rather than routed. While there is some reduction
> in weight, knocking off the corners reduces the surface area of the
> exposed portion of the structural member, requiring less varnish.
> Elimination of the corners also reduces the tendency for brashness or
> splintering common to Douglas Fir.
>
> In a similar vein, that odd green tint seen in the varnish on the
> inside of early wooden airframes came from an anti-fungal agent, added
> to the varnish to prevent the biological degradation of the
> casein-based glue.
>
> -R.S.Hoover
>
Aresenic or copper?

Dan, U.S. Air Force, retired

[Ed Sullivan]

On Tue, 09 Aug 2005 21:27:29 -0500, "Dan, U.S. Air Force, retired"
> wrote:

wrote:
>> This was a standard procedure on many early Fokker & de Haviland-type
>> fuselages (ie, plywood shear-web & wooden structural members), although
>> most were chamfered rather than routed. While there is some reduction
>> in weight, knocking off the corners reduces the surface area of the
>> exposed portion of the structural member, requiring less varnish.
>> Elimination of the corners also reduces the tendency for brashness or
>> splintering common to Douglas Fir.
>>
>> In a similar vein, that odd green tint seen in the varnish on the
>> inside of early wooden airframes came from an anti-fungal agent, added
>> to the varnish to prevent the biological degradation of the
>> casein-based glue.
>>
>> -R.S.Hoover
>>
>Aresenic or copper?
>
>Dan, U.S. Air Force, retired

Copper

[Richard Lamb]

"Chamfered"! Couldn't think of the right word there.

[Morgans]

"Richard Lamb" > wrote in message
oups.com...
> "Chamfered"! Couldn't think of the right word there.
>

I'll bet that you would be just as satisfied with hitting the corners with a
piece of rough grit (80) sandpaper, on a block, then a finer grit (120) in
your hand, all -after- it is assembled.

The reason I say that, is that if you chamfer before you assemble, you will
be reducing the glue surface area, where the wood has already been removed.
It will also give you the chance for one more close inspection, looking for
bad joints, split wood, and so on.

All just my opinion, of course. <g>
--
Jim in NC

[Richard Lamb]

Not necessarily, Jim.

I was thinking to route out the areas NOT in contact with skin and
gussets, leaving the areas where other parts will be in contact.

On the Flybaby, for instance, one might be able to do the routing
after assembling the framework. But my origonal thought was to
lay out the pieces, mark off the areas to be routed off (sorry -
chamfered!) then assemble and glue together.

But the 80 grit grinder is probably as good an approach as what I was
thinking. Take less fore-thought anyway.

Having said all this, I'll point out that the only wood airplanes I've
ever built used 1/16" balsa sticks. Probably not feasible there...

Thinking too much?

RIchard

[Ed Sullivan]

WwOn 10 Aug 2005 12:44:02 -0700, "Richard Lamb" >
wrote:

>Not necessarily, Jim.
>
>I was thinking to route out the areas NOT in contact with skin and
>gussets, leaving the areas where other parts will be in contact.
>
>On the Flybaby, for instance, one might be able to do the routing
>after assembling the framework. But my origonal thought was to
>lay out the pieces, mark off the areas to be routed off (sorry -
>chamfered!) then assemble and glue together.
>
>But the 80 grit grinder is probably as good an approach as what I was
>thinking. Take less fore-thought anyway.
>
>Having said all this, I'll point out that the only wood airplanes I've
>ever built used 1/16" balsa sticks. Probably not feasible there...
>
>Thinking too much?
>
>RIchard
>
Way too much!

[CB]

Sounds like a lot of effort for a few ounces savings, and think of the
the potential damage if the power tool slips... A few swipes with
medium sandpaper to take the sharp edge off seems good enough for me.
Maybe round off the corners a bit (1/16" radius) in the cockpit near
the knees and elbows, but that's about all I'd do.

[[email protected]]

CB wrote:
> Sounds like a lot of effort for a few ounces savings, and think of the
> the potential damage if the power tool slips... A few swipes with
> medium sandpaper to take the sharp edge off seems good enough for me.
> Maybe round off the corners a bit (1/16" radius) in the cockpit near
> the knees and elbows, but that's about all I'd do.

Sounds like a job for a block plane, chamfering plane, spokeshave,
or card scraper any of which will be neater and faster than sandpaper.

--

FF

[Richard Lamb]

Well, at least the goal is worthy.
It's HARD WORK to reduce weight.
A lot easier to add some.

Having said that, I'll give it a rest.

Richard

[Morgans]

"Richard Lamb" > wrote in message
oups.com...
> Not necessarily, Jim.
>
> I was thinking to route out the areas NOT in contact with skin and
> gussets, leaving the areas where other parts will be in contact.

Gotcha

> On the Flybaby, for instance, one might be able to do the routing
> after assembling the framework.

Yes, but there will be stuff in the way, a lot of the time.

> But my origonal thought was to
> lay out the pieces, mark off the areas to be routed off (sorry -
> chamfered!) then assemble and glue together.

Wow, that sounds like a lot of work!

Good woodworkers almost always round (ease) the sharp corners of exposed
wood. That is all I will do, most likely.
--
Jim in NC