LiteStick Modifications
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Home > Articles & Tips Index > Kit Modifications > LiteStick Modifications

[Courtesy of Don Stackhouse djaerotech "at" erinet.com, November 2000]

After all the fuss about Litesticks on the Slowflier list, I figured I should try one out and see for myself. I've had one now for a couple of months, and it's probably a good time now to pass on what I've learned.

After shopping around the Net a little, I found that for a little more I could get one at my local hobby shop. These are the guys who have that bit of hardware or that unusual color of Ultracoat or that odd-sized prop when I need one on short notice, so I don't mind spending a bit more to support them. I bought it from them. The version I have is a GWS "Pico-Stick-S", uses a 10" prop and has metal brushes in the motor, not carbon (more on that in a moment).

I figured I'd build it as stock as possible, then add mods as necessary, so I could see firsthand how it is "stock out of the box". I used the glue that came with it. It dried a bit slow but otherwise seemed to get the job done. I have had zero failures in any of the glue joints I made with it.

The molded-in creases in the tail surfaces that were supposed to act a hinges were way too stiff. I cut them free, sanded the edges smooth and sanded a bevel into the leading edges of the rudder and elevator, then hinged them back on with 3-M's "Blenderm" first-aid tape. For those of you not familiar with Blenderm, it looks a bit like frosty-colored Scotch tape, but a bit thinner and very rubbery. It goes around compound curves well (which will become important in a few more paragraphs), and stretches enough to absorb impacts. It also seems to be a tiny bit lighter than regular Scotch tape. It's waterproof and holds up well over time; I have a rudder on a Speed 600 electric 2-meter Chrysalis prototype that's been hinged with Blenderm for a couple years now, including spending a week and a half out in a cornfield (including going through the initial crash and three severe thunderstorms in that time), and it still shows no signs of deterioration. Blenderm is my current favorite for hinges on smaller models that don't have skin hinges.

The fuselage stick was straight, but the height and width were both a bit oversize. The molded plastic pieces for radio and wing mounting wouldn't slip on. I scraped the top and sides down with a knife until everything fit. The rest of the assembly went smoothly, up until wiring the ESC. I decided to hard-wire the ESC output to the motor to cut down on wire length and connector losses. Apparently I got one of the motor terminals just a tiny bit too hot (didn't have the iron quite all the way up to temp, so it took longer to make the solder joint, resulting in too much heat applied to the terminal), the brush shifted in the plastic end bell, and the motor wouldn't run. After a very tricky bit of work getting the end bell off, I re-adjusted the tiny stamped-sheet-metal brushes and reassembled it. I was glad to have some experience in watch repair (another hobby of mine), but eventually I got everything back together and running properly. Be very careful around that motor with a soldering iron!

I used a Castle Creations "Pixie 7" ESC (tiny, light, and absolutely flawless performance so far), two little GWS servos, and one of the original Hitec Feather receivers. Yes, this is one of the first batch of those, with the short greeen antenna, the ones that so many people had major problems with. I replaced the short antenna with a 31 ga. 39.5" long antenna, but otherwise left it stock just to see how bad it was. Flying in my back yard "out here in the boonies", I've had little or no trouble with it as long as I keep it within about 250 to 300 feet max distance. Not a lot, but adequate for a backyard flier.

For batteries I bought three of the 4-cell 600 mah NiMH packs that Cox sells for their "Firebird" pusher trainer. It was the closest thing to anything suitable at the hobby shop where I was at the time. I cut the packs up and re-soldered them into a pair of 6-cell packs. I figured that with the large diameter prop I didn't want a lot of voltage, or the motor would pull too many amps while tring to turn that big prop too fast. Yes, the big cells make the model heavy (about 8.5 ounces), too heavy for loops (more on that in a moment), but I consistently get over 20 minutes of good, useable flying time per charge, and the climb rate, while not stellar, is certainly adequate. The battery and motor never get more than slightly warm, and I've had no problems so far with brush wear or burnout. I charge them on a cheap Dymond charger at about 1.2 amps, and it doesn't seem to bother them at all.

However, loops are a no-no with the big battery. It requires an agressive dive to get enough speed, and then the "G" load in the pull-up will overstress the bamboo dowels in the wing roots, resulting in a sudden increase in dihedral (guess how I know!). Fortunately it was only one dowel that cracked, and I managed to get the model down without further damage. I C/A'ed the dowel back together, then drilled about 1.5" down along the center with a 1/32" drill and C/A'ed a piece of 1/32" music wire into the hole. It hasn't broken there since.

I'd heard all the horror stories about poor roll response, and that almost total lack of dihedral didn't look at all encouraging, but I decided to try it with the stock dihedral anyway. The model isn't quite as bad as the worst of the stories. It yaws fine with rudder, and a sustained yaw will EVENTUALLY result in a roll response, IF the batteries don't run out first. Yes, you can force it to change heading with yaw from the rudder, but Heaven help you if a gust drops a wing and you need to roll it level again. In a dead calm it's probably adequate with the lack of dihedral, but not fun. In anything more than a dead calm, I consider it dangerous to its own health.

I tried the trick of running a string between the wingtips on top to pull some more dihedral into it. It was an improvement, but still not good enough, and I didn't like the aerodynamics of the string. In addition, I'd used some Berkely "Fireline" (a Spectra-based fishline) for the string. Spectra fiber is based on polyethylene, and therefore has problems with cold-flow. If you subject it to a steady load, it stretches. Sure enough, when I let the model sit overnight and got it out to fly again the next day, half of the dihedral was gone.

I needed a permanent fix for the dihedral problem. I didn't really want to heat the wing root fittings and bend them like some folks suggested, or make new ones out of aluminum tube like others had tried. Then I got the idea of adding polyhedral. Adding dihedral at the tips is a more effective way to improve roll response, and the extra dihedral also improves performance in turns (yes, I know, that's probably the opposite of what most folks believe, but we've been able to explain it analytically and have measured it in flight tests).

There's a molded-in "rib" in each wing panel about 8" in from the tip. I cut the wing along that rib, sanded enough bevel into both sides of the cut to allow for about 3" dihedral, then used 3-M Blenderm tape on top and bottom of the joint to reattach the outer panels (no glue needed). Blenderm is essential here; regular scotch tape can't conform to the highly curved shape. It took only a few minutes, probably less than rigging a king post on top and some rigging wires. If you can't find Blenderm, 5-minute epoxy is probably a good second chioce. The model now rolls quite responsively to yaw inputs from the absolutely stock rudder, and also holds altitude and bank angle in turns very nicely.

I've been using this model for quite a while now to exercize Pedro, our cocker spaniel. He'll bark frantically at this "invader", I'll do low passes over him (about 3-4 feet altitude), and he'll run and jump as high as he can and just miss it. He never seems to tire of this game, and with 20 minutes of battery life I've certainly had enough time to give him a thorough workout! I also do ROG takeoffs from our back porch, "carrier" takeoffs across the width of our picnic table, limbo passes under the clothes line and "carrier" landings on a 5' square stone slab set in the edge of our back yard where the old shed used to be. You don't need to be able to do loops to have fun with an airplane!

With all this flying around obstacles I have managed to knock the wings off more than once. What usually happens is the wing panel catches on an obstacle, it pulls loose at the forward dowel, then snaps off the plastic socket for the rear dowel. Fortunately I saved the sprue that the plastic parts came on. I set my butane soldering iron on about 50% throttle and weld the broken part back on, using the leftover sprue as a welding rod. So far the repaired areas appear to be as strong as the surrounding plastic.

The mounting brackets for the battery and the servos tend to break in a crash as well. I finally got tired of fixing them, lashed them to the fuselage stick with carpet thread, and saturated the thread with C/A. I haven't had any further problems with those parts.

Overall the model flies reasonably well and (with the added polyhedral) has good control response and harmony. I've used it as a trainer for my youngest son with excellent results. It's a good sport model, provided that you find tasks for it that match its performance and personality. I'm personally comfortable flying it in winds up to about 5-7 knots, provided it's not too gusty. Overall it's a decent model, especially with a few mods.

Don Stackhouse "at" DJ Aerotech djaerotech "at" erinet.com, http://www.bright.net/~djwerks/


A followup on "Blenderm" Tape

3-M's "Blenderm" first-aid tape. You can find it at your pharmacy, although they may need to special order it for you. It comes in a variety of widths. For hinging I prefer 1/2" wide, but for reattaching the wings on the LS after cutting them for polyhedral, the 1" wide is better. If you don't want to invest in a whole bunch of rolls of different sizes, just get a roll of 1". If you need some 1/2" wide, pull out a strip the length you need, lay it sticky-side-up on a cutting board, pull it snug (but NOT stretched) and tape it down at the ends, then slice it down the middle.

Blenderm is thin, very flexible and stretchy, waterprooof and light. It won't work for places where you need rigid tape (such as taping the old rudder hinge when making the all-flying rudder mod), but it's great for things that need flexibility, have to give in a crash, or where it has to conform to compound curves, such as the polyhedral mod.

 

 


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