I would consider myself novice in building RC planes and need some help with covering open bays. I believe I may have made a dire mistake in designing these wings and might have to redesign them entirely. Open to all suggestions. I have woven fiberglass and monokote. Open to buying anything else that may work better. I realized my dire mistake when covering the controll surfaces, so I added balsa skin to the leading edges which helped a bit, but I don't see it being feasible with the wing leading edges. I covered 3 of the control surfaces and theres still some wrinkles I cant seem to eliminate without the ribs bending. Any thoughts to redesigns or different techniques/coverings? This should be flying about 80mph so im also worried about sag on the monokote, and believe ill have to fill the LE bays with wood support or revert to Hershey-Bar wings entirely to make this work. At this point I have 100's of hours into this as I 3D modeled every single part in solidworks before I started to build it. Again, open to redesigning if needed! One thought I have is maybe doing dope and fabric, then covering that with fiberglass for the leading edges.

Respect for making the effort to learn cad and getting into laser cutting. There is something to be said for leaning from those who have gone before you. There are literally 16,000 sets of plans on outerzone.co.uk. I'm not saying that you should slavishly copy things but you can observe common techniques. For instance dealing with the leading edge fill. The usual practice is to inset the perimeter of the rib by a distance equal to the sheeting you are using. This will allow you to extend the sheeting across ribs rather than filling in between them. The advantage is that it allows the sheeting to become a stressed portion of the wing and provides what is commonly known as a "D" tube that gives wing or control surface a lot more rigidity. Usually there is a rigid leading and trailing edge that is even with the front and rear of the flying surface ribs. That will prevent a lot of the covering sag. You might also want to check the rotation of your servos. I get the idea of doubling servos but you might want to check the rotation. In particular it looks like the aileron servos will conflict with one another.

mgnostic thank you very much for your input. That link will be a great resource for me.

I believe my wings converging taper won't allow me to add a balsa skin, and the notch at the thickness of skin is an afterthought I also had. It will work great for the controll surfaces if I redo those. Great input 👌

As for the complex wing shape, I'm thinking the dope and paper covered with fiberglass will work for the LE. I may also try foam inserts between the ribs along the LE sanded to the foil profile then covered with either the monokote or some fiberglass.

I'll definitely take a look at that link you sent me to see if there's any other ideas I can come up with here.

As for the servos, I will simply flip the wires on one of each 180 flipped servo so it rotates in sync with the adjacent servo. Maybe I'll run into issues when I get there, but definitely a good thought!

Please follow up with some photos of the finished project.

You might consider adding balsa blocks between the ribs at the leading edge and sanding them to shape. To prevent some of the sagging between the ribs, I would add a pieces of 1/64 ply to the leading edge, above and below the center of the leading edge radius. Sand the edge down so that it blends into the balsa and you should be good to go.

Short of a complete redesign I would notch the leading and trailing edges of the ribs and glue in carbon fiber rod running spanwise. That would allow you to use film covering. I think that any other modifications may add too much weight. I would also highly recommend that you sand off the laser charring as you will want a good adhesion between the ribs and covering. This will greatly contribute to the torsional rigidity that I feel is lacking in your design.

speedracerntrixie
Thank you for your suggestions! Ill definitely be sanding the charred edges before applying any coating. My control surfaces will have 2 carbon rods in each, and V-stab/H-stab/wings will have 3 carbon fiber rods in each.


Hydro Junkie
Thank you for your suggestions as well!

I have some foam blocks and foam cutters. I believe as an alternate to buying the balsa blocks, I can cut the foam to fill in approximately 1" from the LE aft and 1" from the TE fore, between each rib and sand to fit the contour. After, I will add fiberglass along the LE to leave about 1/4" gap on the foam for an area the monokote can cover, which will be over the rest of the wing.

The control surfaces I will use the foam method but stick to monokote only.

Worse case scenario, I will remove the foam and get balsa blocks to replace it.

Let me know if anyone here has any major concerns with this approach. I know the fiberglass will almost eliminate future repairs but I think this is the right route.

..

The carbon rods as you have them are fine for wing bending loads but not so much for torsion. Adding foam will not add any torsional strength either, the fiberglass will but of course will add weight, more so than adding balsa. If you plan to use Monokote on top of foam or even foam that has been glassed, think again. Epoxies thermal glass transition temp is right there with Monokote’s application temp.

So you have constructed that plane yourself???
Very strange looking stabiliser...and large ! -Why that large????
Have you flown R/C planes before??

jaka54
great question, yes I have, and I don't think its quite as large as you're picturing. Those carbon rods will be cut.

Please check out the pictures for a more detailed view. I couldn't attach the video because its too large.

Also note that I will be adding another rod to the MLG for support. This current design may fail under impact.