Aluminum vs Wood vs Hybrid fuselage

[steveukman]

I would appreciate the experience of this group in helping with a
design issue. I am looking for a strong, light fuselage that is easy
to fabricate for a 2 seater tandem biplane.

Constraints:
Easy means no complex activities for a newbie like me (i.e. welding
complex structures).
Available tools will work Al and wood, but not large quantities of
steel.

Option 1. Wood.
Plenty of wood plans around, easy to build, but heavy (when you
consider the plywood, stiffeners &c.) and I am not sure of the ultimate
strength.

Option 2. Aluminum tube.
Aluminum tubing, riveted ... like the Murphy Renegade, Challenger.
Light, string and easy to work, except ..... bending the tubes.

Option 3. Hybrid
A rectangular Aliminum tube 'cage' for a strong firewall-cockpit. Tail
longerons made of wood for ease of manufacture.

Question 1.
How easy is it to bend 1" Al tube to form longerons? It looks like it
would be much harder than with wood. Can it be done around wood
fuselage jigs? Is getting a well aligned fuse going to be a pain?

Question 2.
How could I join wood longeron to Al tube? At first glance I could
'splice' by insering the wood into the tube to a sufficient depth and
then drill & bolt ... and/or use Al gussets to clamp the wood outside
the tube. Is gluing wood to Al an acceptable practice?

I have read the Bingelis tomes, searched high and low for suitable
techniques to no avail.
I would appreciate any ideas / gotchas / "don't do it"s / experiences
on the feasibility of the above, given the constraints stated.
Many Thanks
Steve

[[email protected]]

steveukman wrote:
>
> ...
> Option 1. Wood.
> Plenty of wood plans around, easy to build, but heavy (when you
> consider the plywood, stiffeners &c.) and I am not sure of the ultimate
> strength.

The ulitmate strength is whatever is designed into the plane. There is
more variation in wood than in metals, you need to carefully inspect
every stick for defects, runout in the grain and so onl

Wood rots, that is a consideration if the plane is not going ot be
hangered.

....

> Question 2.
> How could I join wood longeron to Al tube? At first glance I could
> 'splice' by insering the wood into the tube to a sufficient depth and
> then drill & bolt ... and/or use Al gussets to clamp the wood outside
> the tube. Is gluing wood to Al an acceptable practice?

Wood expands and contracts with changes in ambient humidity,
even when it is varnished. FIlm finishes are permeable to water vapor,
they slow the transpiration rate, but do not stop it. Aluminum
expands and contrants with changes in temperature.

Those differences spell trouble for a glue bond between wood
and aluminum.

In general any permanent joint between wood and metal should
be mechanical. Glue in addition to the mechanical fastening
would be fine, but never glue alone.

I've done woodworking and stress analysis so there are my two
decibucks. Others will comment on working with metals
and specifics to airplanes.

--

FF

[[email protected]]

Part of the joy of homebuilding is the learning of new skills.
Pick a proven design and go for it. To try to mix media in order to use
what limited skills one already has just ends up in frustration, money
spent and no flyable airplane in most cases.
It helps to choose a design that's being built in your area by
a friendly homebuilder who can show you how to do some of it. It also
helps to be building an airplane for which materials are readily
available. Be aware that suitable wood is increasingly rare and
expensive and needs hangaring if it's to last any time at all. I own a
wooden airplane, and the next will be aluminum.

Dan