midair02

RCCA GNAT Rules 9-7-2012

1. Contest: With the exception of the following restrictions, all RCCA A-class rules and scoring will be used. GNAT combat rounds will be 5 minutes in duration.

2. Aircraft: All aircraft will be of the popular GNAT design. The following aspects must be met:
A. Wing constructed out of coroplast.
B. The leading edge of the wing must be folded over or have the flutes running with the wingspan or have the exposed flutes of tapered wings covered with tape.
C. Maximum wingspan of 34 inches.
D. Maximum chord of 13 inches.
E. Fuselage length of 24 inches.
F. Equipped with horizontal and vertical stabilizers.
G. Equipped with aileron, elevator and throttle control.

3. Power Plants and Propellers: Only engines legal for SSC will be allowed. Electrics will be allowed. All aircraft will use a non-modified Master Airscrew 8x3 prop. To ensure electrics are on a level playing field with glow engines, the Contest Director will randomly tach 3 aircraft prior to the start of each day of the contest. The highest RPM attained will be the maximum RPM for Electrics for that day. Electric motors shall be tached and the ATV adjusted so that the maximum RPMs are not exceeded prior to each flight.

4. Sticky fluids/sprays, double sided tape and sandpaper/tread tape are NOT allowed. Notches in wingtips and tail feathers are allowed.



Broke down to the basics:
1. Normal RCCA scoring system
2. Looks like a GNAT
3. SSC motor (popular are OS LA .15 and Magnum XLS .15) and prop (MAS 8x3)
4. NO STICKY STUFF!!!


To keep it simple, there are no weight restrictions and no RPM restrictions. Section 3 does limit electrics to what glows are turning so electrics don't have an advantage over glow.

Tom Nied

I got a question. I notice the above GNAT rules state fuselage length 24". The GNAT plans show the aluminum U channel as being 24" with the cutting board motor mount extending beyond the 24". I'm guessing it's not a big deal but I'd like to be clear on this.

Once while flying Indoor Free Flight at a contest, my "Easy Bee" was disqualified because my planes chord was 1/16" too long. Only because I followed the plan that came with my kit and through many copies had gained the extra dimension.

Maybe I'll never enter a combat session, but I'd like this plane to be RCCA GNAT legal. Line #2 in basics states, " Looks like a GNAT ". So maybe it's not such a big deal.

DaneMcGee

I think the intention is to build per the plan, which calls for a 24" piece of alum U channel.

Bill Rademacher

My Feedback: (77)

My only comment is that we started with the cg at 4 and 1/4 inches back, and they flew, but like snot. We moved the CG forward and they flew better and better with each adjustment. I don't remember our final setting, but try it out if you are not happy with the flight characteristics.

billrad

Tom Nied

Hmm, that makes sense. Might consider trying 3 3/4". Might be more to my liking, as far as flying. I do wonder what amount of throw up and down for the elevator and ailerons.

blindfaithnogod

I would start with
1/2" up and down elevator
1/2"-3/4" up and down aileron

That said I have not built one of these yet, but that's about what I setup my other combat ships to.

DaneMcGee

The CG on the plan is wrong. It calls for 4 1/4"

It should be 3 3/4"..... Start there with control surface travel as Paul suggested then as you feel comfortable with the bird switch to high rates with all the control travel that it will throw.

kenh3497

Maybe this???? http://combat.eavesonline.com/ 150 watts per pound so like a 3D plane for performance. It is electric though so may not appeal to all. The motor specified is becoming hard to find. There are motors that will substitute though.

Ken

combatpigg

My Feedback: (3)

Thanks for showing that Ken. Ive heard of FFF Combat but never have seen it. I didn't realize they were so big. Very clever and well thought out. I'll bet it's popular enough to get "Glow Guys" to buy in.

midair02

Like Dane said,

U-channel 24 inches

Start with CG at 3 3/4" and what Paul said for throws. You should set up high rates for as much throw as you can get. The beauty of these planes is that they can slow furball, kind of a aerial ballet when you get a couple of good pilots 3-D'ing it out in the sky.

Tom Nied

Dane, do you still put the 18" x 5/32 music wire spar in the wings that you just fold and mount to the bottom of the fuse, like the Red wing Gnat you pictured earlier? Not sure if it needs it if the holes in the wing coro aren't made. Thanks.

DaneMcGee

Yes, I used 1/8" fiberglass rod x18" long for the spar........ I had no music wire

I believe that without the spars, the wing would fold.

boiler1

I have used 1/8th inch fiber glass rods and the music wire. No difference in strength but the FG rods are much easier to install with a little polyurathane glue. Put a piece of tape over each end of the flute to keep the glue in till it dries.

boiler1

I have used FG rod and music wire. Same strength but the FG rod is easier to cut and install.Put some polyurathane glue in the flute with the rod and tape the ends of the flute until the glue cures.

Tom Nied

I would think fiberglass rods would be lighter. And where do you find fiberglass rods? Online?

DaneMcGee

........Kite builders supply like GoodWinds.com

Tom Nied

Is carbon fiber rod overkill?

Tom Nied

Found this drop ceiling molding that cuts real easy.

boiler1

That stuff isn't too brittle compared to gutter pipe. It might be a little more brittle than fencepost but it it not warping like the post material. Thanks for the suggestion. I like the T shape compared to the L shape.

Tom Nied

As far as I can tell, it appears to be PVC. I was specifically looking for a nice tight 90 degree strip. Found it at Lowes home improvement store. Came in a 8" length, I think.

It was marked on clearance (under $2), I should buy more.

Tom Nied

Appears to be ACP White Ceiling Grid Component. Which is supposedly high quality PVC . I'm going to give it a try. Didn't mean to hijack this thread, but while looking for materials, I ran across this.

You can see how I was able to cut out two nice angle pieces for mounting vertical and horizontal stabilizer.

Tom Nied

Now that the holidays are over, back to the GNAT. It's coming along.

Don B.H.

So I put one together and they do fly combat pritty goodas I went up with Bob who came down from Ohio and we put on a show.

boiler1

I flew mine with Craig Buttery in December in West Palm Beach. It was a short match as he made a direct hit to the center of my wing slicing through the chord and spliting the hing on the aileron. I shoved a bamboo skewer in the one flutes at the field. Since we didn't have any more time before the 2948 scale event I left it at that. When I got home I smeared Outdoor Goop in the rest of the slit and place some fiberglass cloth over the hing and fixed it in place with some more goop. Good as new in about 5 minutes of repair time.

Tom Nied

Don B.H., I'm surprised you didn't end up moving the wing back a bit. I'm at the point in the process where I am deliberating where exactly where the wing is going to mount. I'm guessing at this point 3/8" back from the engine mount. But I haven't had the time to really pin that down. Soon will have some time to play with that. Thanks for sharing. Tom