I spent quite a bit of design time balancing the fuselage length and size, the tail size and weight, and the wing position to minimize the need for balance weight. Didn’t quite hit it. I had to put the muffler on the LA 40 and add another ¼ oz. of nose weight. That is probably where most of the unexpected weight came from.
Span 60 in. Wing Area 735 sq.in. Tail area 124 sq.in.
tail moment 24 in. wing chord 12.25 Kt= .33 Tail Volume.
Engine: LA 40 with stock muffler 10/4 Zinger prop. 10% RC fuel. The carb is set at about ¾ throttle to keep the speed down.
The tail volume is the same as the first Giles(after the tail was replaced). It uses a larger tail(124 sq. vs 105) on a shorter tail moment(24 in. vs. about 27 in.) The slightly higher aspect tail lowered the control forces a bit making control movements easier and more consistent. The control feel varies less with speed
We did the first flights on slightly short lines, abou 57 feet. Took off smoothly from the grass, which still hasn’t really started growing. The plane showed a very slight right roll. Inside and outside turns were pretty equal. It was also a bit twitchy, tending to overshoot in square corners. Yaw in the squares was a bit much too.
After a couple flights we added ¼ oz. of tip weight, and ¼ oz. of nose weight. I also switched to the longer lines, about 63 feet, and put the down line in back. Now everything is close to working right. Less twitchiness, I can feel the neutral and hit solid corners with little overshoot. The tipweight stopped the slight inboard rolling tendency, and the reversal of the lines calmed the yaw in square corners quite a bit.
We managed to get one flight shot with the digital camera. Digital cams are the pits for action shots aren’t they.
A few notes on building. This plane is finished with just two layers of OO silkspan. It was applied with MinWax Polycrylic after filling the foam with light filler. A couple of fill coats were applied and sanded down. Final finish is two light coats of Rustoleum Gloss Protective enamel spray cans with the same paint for trim.
I’ve done a lot of experimenting with finishes for this ship. Must have covered something like a dozen test panels. It seems to boil down to the fact that a decent finish weighs the same no matter how you do it. For this plane it seems to take about 7-8 ounces of finish to seal, harden, and color. The lightest finish would be simply to put several coats of varnish on the foam, after filling and sanding. Then apply the SLC covering and put on the final colors. It seems that no matter what, the heat from applying the SLC covering raises the texture of the foam. The only way I can see to get a really smooth finish would be to fill and sand over the covering.
Two layers of OO silkspan worked fine. Silkspan is still pretty delicate. I got more hangar rash after it was painted than with any other plane I’ve built. It does add about 4-5 ounces of weight but the final finish is pretty presentable. Nice bright colors, fairly smooth and glossy, and durable, as long as I don’t bang into things. Not nearly a 20 pointer, but I’m sure I can get another 5 points or so easier flying than sanding!!!!
You may wonder where the tank is. I use a Yellowjacket(tm) bladder. It's light and reliable. The bladder is in the right wing with the access hole going through the fuselage and it comes out in the left wing. This arrangement keeps the right wing clear for easy cleaning. I have pretty good luck with the bladder. Properly filled it runs at a constant speed throughout the flight. The plumbing to get the fuel to the motor is in the fuselage.