Fabric Take Off

[David Weber]

Can someone tell me roughly how many yards of fabric I need? I have calculated 30 yards.

[whee]

Quote I got from Stewart's was for 33yrds.

[Battson]

If you plan to do much work on gravel, on or off airport - HD fabric under the belly and under the tail wings is a very good idea.
I also used fabric for the interior.

I bought the following quantities (rolls 72" wide):
13 yards of heavy
23 yards of medium (had plenty of spare, includes interior)
4 yards of light (for the headliner, I used the medium for the sides, still had too much medium)

You are also going to want approximately:
25 yards of 1" tape
150 yards of 2" tape
25 yards of 3" tape
​25 yards of 3" bias tape
25 yards of 4" tape

[Flyingmike]

Still in the preliminary processes of planning a build, but I'm curious (I searched the forums but couldn't find anything) if anyone has fabric covered the wings rather than skin them with aluminum?

Are there any drawbacks (other than time and labor, and having to replace the wing fabric)? I'd think a fabric wing would create a lighter aircraft giving more useable gross weight.

[whee]

Mike, that is a question for Bob. I'd venture to guess that by the time you braced the wing structure to make up for not having metal skin then you'd be working a few pounds of a metal wing. And remember a metal wing holds a truer shaped so is a little more efficient.

Example: I used to own a Luscombe 8E with a metal wing. I was wanting to lighted it up and heard that the fabric wings on earlier Luscombes were 40lbs lighter. I talked to a few guys and did some looking myself and determined the weight difference was negligible and that the metal wing was slightly faster. But keep in mind a Luscombe metal wing doesn't have any ribs so there is a bunch of weight saved there.

[Chris In Milwaukee]

All of Bob's planes are single-strut designs. The wing skin is integral to the strength of the wing, which allows one strut. As soon as you go with fabric, you have to put an aft lift strut in, like Cubs, Stinsons, and similar fabric-winged aircraft do.

[Battson]

I have asked Bob about the number of nut plates on inspection hole covers and the tank, which form part of the wing skin. Bob told me that the skin and those covers are all a structural element for the wing, and it's important to have the correct number (as a minimum) of nut plates on those holes. So that makes it pretty clear that a fabric skin isn't an option with the current design.

Not to mention all the reinforcing you would need to do for the nose ribs, and all the sharp edges which would somehow need to be padded out - but it's a moot point. A fabric wing would require a total re-design, that is for sure.

It would probably be easier to modify the fuselage to accept a set of fabric covered wings from some other aircraft, rather than try to modify a semi-monocoque design. But it might be even easier again to buy and modify a Piper Pacer instead.

[James]

Hi Jonathan,
I'm glad you mentioned this in passing - the inspection ports on my wings were made up by the previous builder, but the threaded section of each nutplate is resting above a 3/8" hole, as if he's drilled out the doubler to accept a different type of nutplate body. I might remanufacture the doubler, with the same number of nutplates.
James

[EricP]

If you wanted to skin the wings in fabric it would require a whole new wing. The wing Bob has designed is metal skinned but also semi-monocoque. The skin actually provides a LOT of the strength of the wing. This is really a more efficient wing than the fabric covered wing. So I am not sure why you would be interested in a fabric wing but in this case I can only say it would be a big move backward. Huge amount of engineering to put a different wing on the plane and you most likely would gain nothing.

A fabric wing has internal bracing that is pretty complex so fabric is not as easy as it looks! The skin of the Bearhawk wing provides that bracing so it is doing three jobs! - 1. Cover wing 2. Brace wing from bending 3. Provide strength to assist spar in carrying wing load

If you really want a fabric wing plane I would look at something vintage like a Stinson Voyager, Piper Pacer, etc.

Bob has designed a GREAT wing here. It is actually relatively easy to build with a very flat structure and has a very good airfoil for the intended use. I don't think I would mess with any of it!

[Battson]

I think FlyingMike was interested in fabric from a weight savings perspective?

I always hit aft CG before I hit gross weight. It may be the benefits for a lighter wing aren't there for the Bearhawk?

[EricP]

Even IF the fabric was lighter weight it just isn't possible to use fabric in place of the metal for skinning the wing. You would have to re-engineer the whole wing. The skin is totally integral to the structural integrity of the wing. The metal wing might be lighter anyway. It is certainly more aerodynamic than fabric. At any rate, you cannot just replace the metal skin on the wing with fabric. You would have to replace the entire wing and that just isn't worth it.

Bob is VERY aware of weight on his designs. He used metal wings on the LSA Patrol. Trust me, he would use fabric if there were an advantage. He uses fabric where it makes sense such as the flight control surfaces (ailerons, elevators, flaps, rudder). The fact that Bob uses metal skinned wings on his designs pretty much tells me it is the superior material for his type of design. He would not hesitate to use fabric if it made more sense.

[Flyingmike]

Wow! I didn't expect this kind of response! Thanks... I wasn't trying to question Bob's design or anything, I was merely interested in weight savings on the design. I'm not an engineer, so I have zero idea of what differentiates a metal from a fabric covered wing.

Lol, 12k+ hours of flying and I'm still learning things. I think I'll just stick to the plans when I finally get my ducks in a row and order them to start my build.