jw637362

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I am trying to design 12 foot wings for a Soarcraft Magnum fuse I have. I have all of the plans but I designed a concept and want to know if it is feasible.
Combining a Foam wing with rib structure at the root.
The reason being is I do not trust, tubing for strength inside the foam alone and have no way of alligning them from the fuse. They are permanently installed in the fuse.
This will be Hi-Start launched and winch launched in the future.

I will be utilizing Kevlar wrapped spars up to the foam and the spars will continue thorughout the length of wing obviously THe spars will be Carbon fiber capped as well.
Please take a look at my sketch and tell me what you think. Opinions accepted and dealt with accordingly

Thankyou, Jeff

FlyingTyger

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I've seen a couple of warbird wings built this way to support landing gear that is mounted in the wing. I believe that since most of the strength of the wing comes from the sheeting and spars, the ribs and foam core are simply there to maintain the shape (airfoil). Therefore if you sheet the structure (foam and built-up frame) as a whole, the wing should be plenty strong.

SoCal GliderGuider

You need to tie the wing wires to the spars and the spars to the foam. Use a full foam wing and inset a partial ply rib at the outer ends of the wing wire tubes (brass) besides a full profile (sans the sheeting thickness) rib at the root.

All of this can be pre assembled to match the wing wires then inset into the foam routing and cuttng the necessary grooves. Need lots of glue contact area.

jim2

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Are you worried about folding the wings a the fuse,or the tubes with steel rods going through them into the wing and getting the alignment right?
Confused--Jim

jw637362

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Thanks everyone for the replies:

@ warbird_pilot - it does seem to be a reasonable design as I too have seen it on scale aircraft.

@ SoCal GliderGuider - I am a little confused as to your comment of "You need to tie the wing wires to the spars" I am not familier with the term Wing Wires.
I believe I understand what you are reffering too as to filling the areas after the ribs are made with the rods in place and cuttin the foam to shape.

@ jim2 - Yes to both of your questions, as you can see from the image, the rods are permanantly installed in the fuse and I do not have the option of letting them set after the wings are plugged in, I have too build from preexcisting conditions.

Let me add that this will most likely be vacumn bagged for final glueing. they are four foot main sections (2) then I will build up the outer sections.
Thus not wanting too mess it up by not getting the spar tubes right to start!!

Thanks again, jeff

SoCal GliderGuider

I need to find some time to do a quick Acad sketch.

jw637362

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Ok, here is my concept - I whipped together a mockup wing, foam cut and just used balsa ribs for reference. Brass tubing is placed and it is mounted on the fuse, So you can get the idea.

Rib construction will be double 5 ply on root and two seperate ply sections to foam as is the balsa placed now. Spar voids where tubing is will be filled with epoxy for rigidity. and spars capped with carbon fiber out 1.5 feet, I want a little flexibilty as the wing needs to give to compensate for the strain of the forces on launch. It will be solid sheeting from root out approx 1.5 feet as in drawing, Just left it open in the mockup for viewing.

Too me it seems feasible and it was very easy to align the rod tubes.
Let me add that the original wing for this model is built up ribs the whole length of wing and the root design is the same as the original design by Soarcraft less the spoiler configuration. That will come later. I am also debating ailerons as this plane has a very slow turn radius I am told.
I just want to add foam instead of building the whole wing with ribs.

Thanks for your input.

Love too see your reference material SoCal GliderGuider, I am still in the learning phase of large gliders and wing designs.

SoCal GliderGuider

Should have as much glue contact with the foam as possible. The tubing has to be in plywood not balsa. The root and sub root ribs can be full cord. The outer ribs should not. Spars should be spruce. The tubing needs to be boxed in with ply mainly for the glue contact to the foam.

Attached is a pdf of the quick acad file I just threw together.

SoCal GliderGuider

Here is a jpeg. Changed it to a gif.

Noticed That you have the main wire into the main spar. Same idea as I've shown.

jw637362

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Thanks SoCal GliderGuider - as you can see from my initial drawing, I have two sets of " Spars" One in the front of the wing and one toward the back as in your drawing. This was a mockup wing, about an hour to make for reference only and will be utilizing ply, not balsa, it is only 14 inches long but you can't tell that from the picture.
It seems that your drawing is roughly the same layout as mine so I am under the impression that this is a doable / workable project, I will utilize your thought on the ply and spruce and will definately box in and epoxy the "wing wire" tubes.

One other question, this wing will incorporate spoilers, Should I put Ailerons on it as well??
The trailing edge is very thin, but I do not know if that matters.

Thanks again, Jeff

SoCal GliderGuider

Notice that I keep the floating sections of foam between the ribs. This is to bind the spars and the sheeting. Also maintains the shape of the wire cut wing.

For a scale look and thus flat wings I would use ailerons. About 25% of the cord and about half the length of the wing. You can keep the ailerons short of the tip by the cord of the tip. The TE does not have to be knife sharp. 1/16" squared off as in my sketches (not to scale) is sufficient. Do not round it off. Keep it square cut.

I prefer flaps over spoilers. As long as the flaps can deflect to almost 90 degrees. Same as ailerons 25% of cord. Tape hinge the ailerons on the top and the flaps on the bottom. I coat the balsa sheeting with thinned white glue where the tape would be on the plastic covering. This keeps the plastic covering from pulling off of the sheeting.

Ailerons will deflect up three times more than down. Differential.

jw637362

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Moved question to silplanes section............