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sgilkey -> RE: JKA reccomended mods (1/21/2008 3:35:53 PM)
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I agree that HS81 will strip easily, even if you use two of them for ailerons. you need MG if you use the HS81, 85, or 225. even those will strip- Hitec leaves one plastic gear in the MG servos, and it will strip in a hard hit, just not as easy as the plastic (the hitec plastic gear mini servos strip pretty easy and are usable only for throttle). so if you have, say, an HS81MG and you strip the one little plastic gear, you can replace it with the one from the plastic replacement gear set (which is cheap- you don't need to get the expensive MG replacement set).
To me, all the hitec resin gear servos strip easier than the futabas. I use the Futaba s3003 by the dozens, they do strip, but are pretty tough. Stay away from the HB (Karbonite) hitecs, the do NOT take impact well and break way too easily for combat use.
diffrent strokes for diffrent folks on the wing construction, follow the method that appeals to you most. when i want to evaluate a construction method, I build a test part- using some scrap or your wing shucks, try building a foam "core" with balsa TE and aileron, CA hinge, and then pull/bend/beat/smack with a prop on it as if it were taking a midair or crash. Do the same with a strapping tape/coro setup, and judge for yourself which one will absorb battle damage. The balsa setup is lighter.....if you do the criss-cross strapping tape hinges, you need no other hinge material, but just cover over the hinge line with packing tape when you cover the wing, to seal the gap.
If you have full-span spruce spars with no joint in the center, I don't think f/glassing the center will do anything of value. What I would do, if you have wood spars, is wrap a strip of strapping tape SPANWISE around your wing. Start at one tip, and wrap over the spars to the other tip, around the tip, over the spars on the other side, around the tip, and overlap the starting point. One continuous strip. This will help support the wood spars.
On the tank, it's tricky, the front end does get crowded. What I do on some planes (usually the narrow, in-line engine ones) is cut the fuel tank pocket to just fit the tank, in both halves of the fuse, before I join them. I cut a notch in the firewall so the tank can slide in/out from the FRONT, which is much easier to service, especially in the field. The engine mount partially covers the hole in the firewall, and retains the tank in the fuse. Makes it very easy to fix plumbing problems or replace a leaky tank. If you need to fish the tank out from the radio compartment, usually there's a throttle servo and a bunch of other junk in the way.
Don't worry about leaving room for foam padding around the tank, like you would on a conventional glow plane. Most combat planes have the fuel tank mounted right in the foam fuse, with no padding. The 25FX is such a smooth engine, foaming is not usually a problem. Some engines such as the cheaper brands do vibrate more....leaving room for foam padding only means less foam structure for the fuse, in an area where you really need structure! Now if you have a plane where there is ROOM for padding, or an open-type plane where you can mount the tank with padding, that's a different story, but still, with a 25FX, padding is not needed and I usually use two-sided tape and zip ties to mount the tank.
Notching the firewall for tank access can weaken it, use at least 1/4 birch ply though two layers would be even better. I use 1/4 lexan, which is very tough. Glue it on with PU (the only thing I've found that remotely sticks to lexan and foam) and then wrap some strips of strapping tape across the front of the f/wall onto the fuse sides, to help hold it on. With either wood or lexan, I use #4 sheet metal screws to hold the engine mount to the f/wall.
Depending on balance, I usually try to work it out so I can put the battery flat, in a small pocket under the rear of the fuel tank, up front where it won't hurt anything (this is where the small flat 300-400 nimh packs come in handy). Then I locate my throttle servo where it makes the most sense (due to packaging constraints, p/rod routing, etc), and then cut a hole in the side of the fuse and stick the elev servo in (on the outside) wherevever it needs to be to achieve the correct balance point, somewhere between the wing TE and the hstab.
for a roomier radial-engine type, it may be much easier to package everything in the front end and still have plenty of "beef" to absorb impacts.
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