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Speed,Combat,Scale,Racing => Carrier => Topic started by: bill bischoff on November 19, 2010, 11:35:58 AM
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Here is some info on my new Profile Zero. It's not really new since I started on it over three years ago, but I just recently finished it. This is the same airplane in David Russum's photos from the recent Dallas contest.
The airplane uses a 41" foam wing with about 340 sq. in. The wing is covered with silkspan , and topped with low temp iron on film. The green is Solarfilm, and the gray is Sig Aerokote. The fuse and tail feathers are standard wood construction, finished in dope over bare balsa. The insignias are the 1/12 scale Japanese WWII set from Major Decals, and the canopy is cut vinyl from a file we created. The weight is 42 oz, including 3 1/2 oz tip weight. The engine is a reverse Wiley 36.
The features that make this airplane a bit different are the wing mounted landing gear, and the line slider design. The landing gear are mounted in 1/2" basswood blocks, which are keyed to the fuselage. If I've done it right, there will be accompanying photos which will explain things better than words. The slider was designed to be less draggy, less complicated, and less ugly than previous designs. Note that this slider doesn't really have a "slider". It is simply a slot for the lines to move in. The little aluminum bar holds the lines forward for high speed. When the hook is dropped (by full up elevator), a cable is pulled, and the aluminum bar falls back out of the way. The lines then slide back to the aft position where they are retained by a small wire catch. The lines are kept grouped together with a brass line eyelet. I cut a slot across the eyelet with a razor saw (like turning a letter "o" into a letter "c"). The eyelet is placed around the lines between the bellcrank and the slider, and gently squeezed shut with pliers. At the end of the day, the eyelet is spread open and removed. If you zoom in on David's flight photos, you can easily see the eyelet.
At the risk of repeating what I've already posted, the airplane has only six flights, but has performed extremely well so far. The first timed low speed was 4:49. It was windy at the contest the next weekend, and I still managed a 3:49. The airplane was more stable and predictable in the wind than the MO-1, which sometimes pitches nose down when crossing directly downwind. The best high speed has been 21.1 sec, which for 10% and open exhaust is quite acceptable. There is probably a bit left in the high speed needle setting as well.
I am working on a CAD built up wing, and ultimately I plan to have plans and maybe a wing short kit available. If anyone is desperate to build one right away, I can provide some outlines and sketches. Of course, questions are invited.
Bill Bischoff
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Thanks Bill, keep us informed when you can. Interesting fresh project.
Wayne
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Hey Bill, I like it. Have gotten out once this year to fly the old G-S Bearcat and get a new Skyray in the air. I have Webra engines on both. Keep us posted on the Zero and I hope to see ya down the road. H^^
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Very nice looking model Bill #^
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I just came up with a simpler line slider than I used on the Zero. It's functionally very similar, but less complicated. The little aluminum "flipper" is not needed. Instead, the brass eyelet that holds the lines together is locked in place by the release cable from the hook.
I constructed a mock-up and took some pictures. The wing rib is 1/16" balsa, and the frame is 1/16" music wire. The rib gets 1/32" ply doublers on both sides. A 1/8 ply "trough" holds a brass eyelet in the desired high speed position. A hole is drilled for a music wire pin which will hold the eyelet in place. An 1/8" ply side closes the open side of the "trough". Some small basswood blocks are added as supports for the music wire pin, and the assembly is drilled. The catch wire for the aft end is bent from .025 or .032 music wire. Holes are drilled, and the catch wire is sewn to the rib with thread and saturated with CA.
Operationally it works just like the other slider. The lines are locked forward for high speed by the release pin. The hook drops, and pulls the pin, releasing the eyelet. The lines slide aft, past the catch, and get locked in the slow speed position.
The only special tool required is a pair of round jaw needle nose pliers for bending the wire bits. The key to the design is the line eyelet. It needs to be fairly large. The one I used is from a new set of Sig control lines. It looks to be about 3/16" ID. I have lots of others that are 1/8" and 5/32", but they are really too small, and would put the release pin hole too close to the edge of the rib.
I will definitely use this design on my next airplane, and encourage others to consider giving it a try. As always, feel free to ask questions.
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Bill -
Question -- It appears that you don't use permanent leadouts, so do you connect the lines directly to the bellcrank? If so, how do you make up the ends of the lines so that you can get them through the eyelet?
Thanks --
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The lines connect directly to the bellcrank with buttons made from blind nuts. On my Zero, I used an existing set of lines, and sawed a slot across the eyelet to fit it over the lines. Then I just squeezed it shut. I think there won't be enough force generated to spread the eyelet open, but you could always put a couple of wraps of copper wire around the eyelet and solder it. If you are building a new set of lines, simply build the eyelet onto the lines. (The line ends are too big fit through the eyelet.)
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KOOL