sgilkey
Posts: 144
Joined: 2/27/2002
From: Shelby Township,
MI, USA
Status: offline
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for a short wing like this, coro will work well for ailerons. coro has an advantage in that it takes prop strikes better, and if it's sliced by a prop, it's easy to fix with tape and bamboo skewers. A balsa aileron will often splinter when struck by a prop, and is harder to field-repair. You definitely want a fuse reinforcement for the wing dowels, there is a lot of tension on the rubber bands and they will rip the dowels out of plain foam. One solution is the coro doublers as mentioned, or about a 1 inch square of 1/16 birch ply or lite ply, glued to the inside of the fuse, with the dowel hole drilled through (use f/g rods for the "dowels" instead of wood, the wood will split in an impact, f/g "dowels" are virtually indestructible). an even better solution is to use .100" to 1/8" dia. f/g rod fuselage longerons, buried in the foam, that go from the firewall back to the tail- this will really toughen the fuse (not sure if the JKA has those by design... some planes do). run the lower longeron just above the high point of the wing saddle and the upper longeron near the top of the fuse side, where it starts to wrap over to the top. you can make the grooves for the f/g rods with a soldering iron dragged along a straightedge. bury them in the fuse with PU glue and a few wraps of strapping tape to hold them in till the glue dries. then when you install the wing dowels, drill the holes just above the lower longerons. this will just about ensure the dowels never rip out of the fuse. You still need doulers (ply or coro) to keep the dowels from tearing forward or backward, but the biggest load is downward, and this is absorbed by the longerons. don't notch the firewall for the longerons- have them butt up against the back of the firewall. otherwise, in a dirt nap, the longerons will poke forward with enough force to pierce engine parts such as the muffler. if they're butted up against the f/w, this is usually avoided, but what WILL happen is rods will tend to bow OUT and explode the fuse, that's why you wrap strapping tape around the fuse to hold it together.
Now that you have a rubber banded wing that can absorb impacts, you run into another big area where scale planes get ripped up- when the wing shifts a lot in a big hit, aileron torque rods will either get hung up and bind on the fuse sides, or they'll just rip the fuse to shreds. you can avoid this by laying down the servo in a well in the wing, and driving the ailerons with cables buried in the wing (make the cable grooves with a soldering iron), OR use dual mini servos for aileron (much easier but more costly). I'd recommend MG servos for aileron, if you use minis (ie HS81 or 85 MG). A standard size, resin-gear servo will usually work OK for scale plane aileron servo, but even those will strip in a major hit.
Tape aileron hinges are very durable. Conventional CA or pin hinges buried in the TE will rip out. The way to keep a tape hinge from allowing the aileron to pop up or down over the hinge line is to use a criss-cross arrangement. Using strapping tape, cut two strips about 1 1/2 inch long each. Stick them together sticky-to-sticky with about a 1/4 inch overlap, so you have a strip with adhesive on opposite sides, with the small center overlap. Using such strips in pairs, tape the aileron to the wing TE such that one strip is stuck to the top of the aileron, with the overlap area THROUGH the hinge line, and the other side of the strip stuck to the bottom of the wing. Right next to it, attach another strip opposite( ie stock to the top of the wing, overlap thru the hinge line, stuck to bottom of aileron). Use three or four such pairs of mating strips per aileron, and you have a nearly indestrucible hinge that won't creep. Then cover the hingeline with packing tape when you cover the plane. If your aileron is damaged, it's pretty easy to repair if it's coro, but if it's shredded, you can easily slit the tape hinges and tape on a new aileron in minutes.
Try to keep as much foam as possible in the front end of the fuse, ie make your tank cutout as small as possible. In an impact, the front end absorbs the brunt and you want as much structure there as possible. This is where f/g rod longerons really help.
Lay out your radio equip so the rx battery is in front of anything damageable, esp. your Rx. and use the small, light 300-400 nimh cells instead of heavier nicads, or 700-size nimhs. in an impact the battery becomes a battering ram and will crush the Rx or anything in front of it. It's much easier to control the smaller nimh packs, they are much less destructive!!
wrapping your fuse or other parts with fiberglass will not add anything but weight. fiberglass actually tears very easily and in an impact or prop strike it will fail. Try it yourself- glass a piece of scrap foam, bend it, and then notch it with an xacto knife- the notch will propagate and BOOM the part will break in a spectacular fashion. Using water-based polyurethane to adhere the f/g cloth, rather than epoxy, is an improvement but the f/g is still relatively brittle. Strapping tape is much tougher and will yield when bent, and is not so notch-sensitive.
A few more hours spent making these modifications when building will help keep your plane in the air, and help it endure the inevitable impacts to come!
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JKA reccomended mods - 
