Greetings,
I'm after a bit of info re control surface throws for a flying wing I've just about completed. It's built from plans and there's no suggested throws mentioned. It's 41" span, 12" chord, 2" thick with 1" elevons. It was originally designed for .15 to .21 size engines, but I'm putting an old Magnum .40GP on the front (it's been done successfully apparently). It's a King Kombat, for those who may remember it.

Can those of you who fly combat wings give me a guestimate as to throws for this thing?

Thanks,

that should get you in the ball park.

Start with 3/8th.

A bipe Gremlin ????????

For your King Kombat's initial flights balance it on the front edge of the spar. Set your elevator throws to 1/4" up and 1/4" down.....and set the aileron throws to 1/2" up and 1/2" down. As you move the CG rearward, it will take less elevator travel to stall it.....but the rearward CG will make it more maneuverable.

Back in 1979, several of us around here built and flew King Kombats. Initially we powered them with OS 25 bushing engines, but later changed to the K&B 3.5cc engines to get more power and speed.

We also discovered that if you left the wingtips off of the King Kombat, and used a K&B 3.5cc, the elevons would flutter in a slight dive. Since you are planning on using a Magnum 40GP, be careful because your King Kombat could easily go fast enough to flutter the elevons.

Eventually, our King Kombats evolved into a plane I called the DaWing, which used foam wings, OS 40FP engines, and had a modified elevon design that completely cured the flutter problem, even without the wingtips. In fact, I used to have a DaWing powered by a Rossi 40 just to go blazing around the sky. If you visit my DaWing web page, you will see the distant resemblance to the King Kombat.
http://mypage.yhti.net/~dmcdnld/dawing.htm

A club buddy tells me I also need to have both elevons up slightly (1/8 inch) or it will take a nose dive upon launch. He reckons to do this for the test flight, then trim it and leave it. Is that what you guys do? Also, how do you guys launch these things? I'm assuming it's a 2 person job? What do you get your helper to do? Just let go of the wingtips when you give him the nod, or does he need to give it a bit of a push?

Hey Dave, do you know what sort of speed you're getting with these things? The aforementioned club buddy (who had one of these King Kombats years ago) reckons I should be able to get something like 200kph out of this thing I'll be stoked if that's the case! I'm beefing up the elevons by using 5mm balsa instead of the 1/8th inch the plans call for, in anticipation of the extra speed. I've also added an extra hinge for each elevon, just in case. I like your idea of the foam cores. I'm going to ask the aforementioned club buddy to cut me a core for the next one

I'll post some pix when I get it all together.

Mrbonk, maybe an 1/8th up. Or when you launch, have your hand on the elevator not the gas.

Mr. Bonk,
The short answer to how much reflex you will need is......."It depends on your CG."

On a flying wing with a symmetrical airfoil, the reflex needed in the elevons is entirely dependent on the CG location. The more nose heavy your King Kombat is, the more reflex it will need to maintain level upright flight.....AND the more control surface deflection it will require. The further aft you move the CG, the less reflex it will need, and the less control surface movement it will require. In fact, if you move the CG location back far enough, you will eventually find a "sweet spot" for the CG where no reflex is needed at all. And with the CG at the "sweet spot", the plane will fly straight and level upright, and also straight and level inverted without having to retrim the elevator. For combat, this "sweet spot" CG works great! It gives you maximum maneuverability, and the plane simply goes where you pointed it last.....no matter whether you were upright or inverted.

For your initial test flights, I'd recommend setting the CG at the front edge of the spar. Then adjust your linkages to get about 1/16" of up reflex in the elevons. This should get you pretty close for the initial test flight. Once it's trimmed out and back on the ground, be sure to note how much reflex was needed for your particular CG location.

To handlaunch the King Kombat, have a helper grab both wingtips, rev your 40GP to about 1/2 to 2/3 throttle (not full), and give it a gentle push at an upward angle of about 30 degrees. The partial throttle launch will quickly get you up to flying speed, but also allow you some extra time to make any needed stick corrections. Once it's been trimmed, handlaunches are much easier. It simply goes where the handlauncher aimed it.

And after the initial trim flights, you can easily handlaunch it yourself. Using the left hand, wrap your fingers around the leading edge next to the fuel tank, and place the thumb across the top of the motor mount. Set the throttle at about half power, and give the DaWing a slightly upward and forward push before releasing it. Once properly trimmed, it will fly right out of your hand.

With an OS 40FP, no muffler, and an APC 9.7 prop I once clocked a DaWing at 117 miles per hour, or 188 kph. I would expect a King Kombat with a Magnum 40GP be similar in performance.

My name is David cope have flown king combat`s since 1979
and still have 3 left & several k&b 3.5
look at what dave mc donald says thats perfect information
for your project & yes keep youre hand on the elevator
at least they have computer mixing now 1 of mine still has a dubro mechinical mixer 120 plus w 3.5 &tuned pipe so be really ready

are any of you flying deltas like laser arrow or DD
and does info on cg sweet spot & reflex aply.
where can I get fome cors cut

rc yogi 2,
Yep, since a Diamond Dust has a symmetrical airfoil, the same reflex vs. CG sweet spot applies. To even get close to this with my DD, I ended up moving the CG back 5/8" behind the farthest aft CG shown on the plans. Even at -5/8", the DD was still slightly nose heavy, but was much better than before.

Hi , Dave
Is there any plan for Da-Wing 40 ?
Thanks

Sorry, no plans are available since I'm using jigs to fabricate the wing cores.

Thanks
mjse

Hi

I have no any plan , i would like to build one combat wing , my questions are :

1- what is the best wing size for .25 engine ?
2- where is correct CG for it ?

Any help would be appreciated .

Thanks

Find Lee Liddles email address on the rcca forum and get a Combat wing from him... He is the combat wing king right now in RCCA...esp the North Texas Round Robin..... He has a SSC wing called the falcon that is 60" span for the stock .15 and a 72" monster for open b (up to .30).... Wing area is everything right now in combat so give yourself a fighting chance and go BIG.... I have a ssc falcon and its the best combat ship I have ever flown.... b open , scale or ssc... see ya johnny v