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Building Tips and technical articles. => Building techniques => Topic started by: Bootlegger on April 15, 2012, 01:44:47 PM
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Anyone built a Sky Ray using a foam wing?
How did it go?
Looking to do this using Tom Dixon's foam sheeting method..
Any help and or suggestions appreciated..
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I've been tempted to, but haven't done anything beyond thinking about it.
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Go for it if you are doing it for fun flying. I've done several planes using foam cores. Put leading and trailing edges on. Then sheet and capstrip like built up wing. Be careful you don't put a warp in while planking. On one I cut out the foam in between the cap strips. Never again. H^^
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I would put a Flite Streak "Foam Wing" in it.
It will fly much better!!!
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Good idea Paul.
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Hello John, I'm not stirring the pot here just curious as to why you would sheet the foam. I understand for strength. I've been using Phil Cartier's wings for a few years now. Using the techniques he suggests, the foam wing is almost bullet proof. No need for any sheeting and the only wood required would be the spar. I generally use a piece of basswood for the spar 1/8" x 3/8". Placing a strand of carbon tow under the spar in fact keeps the wing stronger than anyone would imagine. The same carbon tow can be stripped into 1/8" strands and glued to the trailing edge with white glue or foam safe ca for a incredibly strong and straight edge. Phil uses a lap technique for his SLC covering which virtually needs to be cut off with a razor knife if you do say explode the wing. I can assure you the foam will hit the ground and everything else will break around it using Phil's techniques. In fact many of the guys flying speed limit combat with what would be a fuselage, they have designed in break away points. In other words putting a saddle into the fuse so that you have a plug in wing is one idea. You only need a little Gorilla glue to hold the fuse. I mean a little. If it hits the ground the fuse breaks away without shattering. The wing is first covered in film then glued to the fuse so your really only gluing to the treated film which is good if it contact with terra firma. The strength is perfect until you need it to break. I just built a foam winged Ringmaster using his foam wing with a internal bellcrank. Obviously the mechanics took a bit longer, but the weight savings was a real benefit. All up weight using a somewhat heavy landing gear (bent aluminum) I ended up with 29 oz's with a Fox.35. I covered the foam with Econokote. The film added almost 2.5 oz's just in its weight. I could of easily cut that in half using SLC. In the event the airfoil is thin at the trailing edge, silkspan applied with thinned white glue makes that edge as tough as wood. I usually follow the silkspan with a 3 " wide strip of SLC wrapped around that. Not only is it simple and strong but using the iron you can bend it in any shape you wish. Ken
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I covered the foam with Econokote.
My experience with Econocoat is that the glue turns to goo from exhaust residue -- what do you do to combat this?
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Hello Tim, I was initially raising the question in regards to the initial post as to why sheet the wing. I'm assuming that it may be believed that the foam isn't strong enough by itself. I went onto explaining that Phil's covering and methods are quite remarkable as far as weight and strength is concerned. Unfortunately, the SLC covering is only clear. I merely suggested on my latest build using some of Phil's techniques and covering with Econokote that I chose a color. I myself never had this covering turn to goo. In the event your telling me this, it only leads me to believe fuel is seeping under the covering. I do several things to prevent this and it will happen to ALL coverings. I use alcohol prior to finishing all of my seams. Prior to folding the leading edge over or trailing edge, I try not to even touch that area. I use Nelson clear extensively as well on seams, decals, and also leadout exits. Although the product isn't recommended for films, it works for me and I'm pleased with the result. Back to the origin of the post though. I can certainly see the benefit of sheeting the wing for durability. I for one have never sheeted a wing so I was wondering how much of a weight gain is to be expected. I can see sheeting the leading edge would also have a benefit. This however would require cap strips and trailing edge sheeting. Whenever I see this being done, epoxy being used sparingly is typically the glue of choice. Does this put the weight back on as well? I look at foam wings generally as a expendable item. In the event all this was to be done, is it just as easy to build the wing traditionally? I do however feel the results from sheeting parts of the wing would look terrific. We have one member in our club with a particular wing as described above. The wing is actually silkspanned and doped. Is this the other benefit of sheeting the wing? I would imagine one would have to be quite careful initially using light coats of dope until the silkspan is sealed. Ken
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Ken I recently built a Bill Bischoff design Hellcat using Phil's Gotcha 740 wing and it is a very good plane. I covered the wing with silk span and 50/50 Titebond/water with Econocote over that per Bill's instructions and it looks great. I am curious about the internal bellcrank and how that goes together.
can you expound on how that works?
Thanks,
Steve Thornton