Kite Fabric for Combat Wings?

Our EPP wings need flexibility for impact absorption, AND a tight skin to keep the wing from twisting under flight loads. For several years, Ultracote was THE BEST covering answer for this dual problem. Now we have a superior alternative: Icarex

Icarex comes in many colors and it's light and super strong. All colors except white seem to be hot fuel proof, but our white may not be indicative of all whites available. Icarex is a trade name and technically not still in production, however kite flyers still use the name "Icarex" to denote the lightest and strongest ripstop polyester.

Note: For sport flying, we still recommend Ultracote for looks and ease of assembly, but for combat, nothing beats Icarex

The cloth you need is 1/2 oz per square yard ripstop polyester coated with polycarbonate. It has a weave similar to ripstop nylon (RSN) but feels more like plastic tissue paper. It is not nearly as stretchy as RSN, which makes it a good alternative to Ultracote (RSN applied to EPP was a dismal failure). This fabric is available from Hang Em High Fabrics online, as well as other kite supply stores. They offer it in 40" and 54" widths, and sell it by the yard.

Here are the online store link to Hang Em High's Part 12PCxxx - 1/2 oz. Polycarbonate Coated Ripstop Polyester

(Note: both 40" and 54" widths are available)

Contact Hang-Em-High Fabrics at :

We apply Icarex in 2 layers with 3M77. We cut the first inner layer on a 45 degree bias, and this gives maximum resistance to tearing. 2 yards of 54" is sufficient for the Panther.

For the outer layer we use the 41" width 2 yards cut to 65". The diagram shows only 33" is needed.

You can join different colors to make patterns if you like, but I suggest overlapping by at least 1/2" and sealing the seam with CA.

Icarex is actually pretty fun to work with, as it stretches over uneven surfaces and shrinks slightly with heat in the same temperature range as low temp coverings (250 deg F.) We seal the seams and edges for fuel proofing and durability with CA, epoxy, or Goop. Goop can safely be thinned for brushing with laquer thinner. Final weight is comparable to a single layer of Ultracote. It accepts paint and you can detail it as you like. The only drawback we've found is we can no longer clean fuel residue off with mineral spirits, as we've found it tends to penetrate undesirably, however the usual soap/alcohol/ammonia solution works well.

Hinges are made automatically with this covering as the top and bottom layers are ironed over the elevons, and then sewn down the hinge line from top to bottom to top (etc) with carpet thread for ultimate toughness. The ends of the thread are anchored in the balsa elevon tips with CA.

The steps for covering with Icarex are illustrated and explained in our Panther and Predator kits.

As an overview, here's the process:

1. Get enough Icarex so you'll have 4 strips that each cover the wing and elevons with about 3" extra at the edges. You can use multiple pieces for splicing wing tip small areas, but this is not recommended near the wing center. The inner 2 layers (45 degree bias) don't actually need to extend to the wing tip edges if you prefer as you won't need double strength at the wing tips.
2. Cut 2 layers on a 45 degree bias to the wing chord (or span). It seems like you'll waste "some big trangles" here, but you can cover smaller planes with these, or use it for patching later. We like to use white for the under layer, and always use this for the 45 degree bias layers.
3. Cut 2 pieces for your outer layer on a "normal" bias. We like to have different colors for top and bottom.
4. Be sure all components are installed, and the wing and elevon surfaces are sanded smooth. We like top hinged elevons with rounded corners for the wing sub TE and elevon bottom corners. This method will work for other hinge geometries, but take care to think through when applying.
5. No need to spackle, but vacuum to get the dust out.
6. Spray 3M77 over the entire wing bottom and the bottom of the elevons. Not dripping wet, but be sure to get good even coverage.
7. Spray 3M77 onto the bottom covering piece (45 degree bias -- white in our case).
8. Let the 3M77 set until it's no longer tacky (this way you can position the covering easier)
9. Start to stretch the white (45 degree bias cut) Icarex over the wing bottom. The glue sides go together. Lift and smooth it with your hands. Iron down only when no wrinkles are present. A covering iron set at 250 degrees F works well. Avoid using a heat gun. When it works right, you'll actually see the 3M77 "liquefy" under the Icarex and you'll see any voids that need attention. Slit and pleat as necessary around corners or servo splines. Cut any access holes later.
10. TE Hinge : Place the elevon on the wing top as though it was folded over onto itself by the hinge. Stretch the bottom covering around the TE to the top (bottom of elevon) and smooth it in place.
11. Iron Icarex onto sub TE and elevon when the Icarex is smooth and tight. Flip elevon away from wing top and examine to be sure gap isn't too big or small. It's usually never too small with top hinged elevons.
12. Spray 3M77 on the entire wing top and the top of the elevons. Again, be sure to get good even coverage.
13. Spray 3M77 onto the top covering piece (45 degree bias -- white in our case).
14. Let the 3M77 set until it's no longer tacky
15. Now apply the top 45 degree bias cut (white) covering to the top, stretching, smoothing and pleating as before. You'll be able to pull the covering over the elevons very easily and flex the hinge.
16. Iron down the top covering as you did the bottom. Take care around the hinge to make sure it's free and tight. You can cut the Icarex even with the elevons, but go around the LE with about 1" overlap to the bottom.
17. Examine wing. You're half done!
18. Spray 3M77 on the entire wing bottom (over the first layer of Icarex) and the elevon bottoms. Again, be sure to get good even coverage.
19. Spray 3M77 onto the outer bottom covering piece (normal bias -- color in our case).
20. Let the 3M77 set until it's no longer tacky
21. Now apply the outer layer of Icarex to the wing bottom. Like the first layer, but this time try to make the edges prettier. Take care to keep the hinge free when ironing by flexing elevon onto top surface like before.
22. Spray 3M77 to wing top surface and let it set till not tacky.
23. Spray 3M77 onto the outer top covering piece (normal bias -- color in our case).
24. Let the 3M77 set until it's no longer tacky
25. Apply upper surface Icarex like before. Again, be careful around hinge to make sure it flexes very freely. Overlap LE at least 1". Dress elevon corners as you wish.
26. Now get some carpet thread, a sewing needle, and stitch the elevon hinges down the small hinge line gap. First poke through the balsa at one end of the elevon near the hinge line several times (use thimble!) and anchor thread with CA.
27. Stitch all the way down the hinge. A single line of thread with 1/8" to 1/4" long stitches going from top to bottom and back to the top will suffice. Anchor opposite end of thread with CA as well. Repeat for other elevon.
28. Seal edges and overlapping seams of Icarex with epoxy, CA or thinned Goop. Pay particular attention to LE and areas that get fuel soaked. Goop thinned with laquer thinner has good penetrating properties and dries quickly.
29. Install rest of your equipment, go fly, crash or whatever!
30. repairs can be more Icarex, clear thin packing tape or Ultracote covering. Ultracote will stick to Icarex without 3M77 underneath.

    A great way to patch rips is by using fiberglass reinforced strapping tape. Apply CA all around the patch edges, and then iron down. The glue and fiberglass threads in the tape turn almost perfectly clear, and the patch is very strong. This is great for prop strike rips and elevon hinge repair.

Many thanks to Scott and Brian Gilkey who have pioneered and perfected many of the techniques for Ripstop Nylon (RSN) application. They gave us lots of great advice which helped our research, and carried over well to Icarex application.