Muldoer

Here is something I built that I thought may interest others. Looking at the SPAD2K plans and doing a little modifying, I made a motorglider.

The wingspan is 75 inches, basically a 36" yardstick midsection with 2x 20" sections for the outer wing. The polyhedral is 4" for each 20" section. I used the FNS25 plans for the airfoil. The spar is cut to 3/4", as the FNS wing would have made too thick an airfoil for glider use. Wing thickness is 11% of chord, I was aiming for 10%.

The Fuse is a SPAD2K fuse...which is basically a Deb fuse turned over. Although its canadian pipe rather than american pipe. The radio access cover is 13" from the firewall and is 6" long. I mounted the Rudder/Elevator servos(micros!) on top of the tail, approximately 15" from the tail end of the gutterpipe. Whilst moving the wing for balance, I couldnt move it further back because of the servos, so I had to add a bit of weight to the front. I swissed the tail to save a bit of weight. Tail feathers are SPAD2K but given 1/2" more chord on the stab and 1/2" more height on the vert. A coro fuse would also work well and save a few ounces of weight.

AUW is 3 pounds give or take a few ounces. Wing loading works out to 10.2 oz/sq.ft. I used an 8 ounce tank because I didnt have anything smaller, I just dont fill it up all the way.

Flight report taken from spadworld:

"I fired up the little 10 and gave her a good 3-4 minute first flight. I am not accustomed to rudder only control for turning, so I accidentally dove it into the ground...busted a prop.

Put a new prop on, fired up the 10la again and this time had a good 10 minute flight with the engine on. I didnt fly her too high because I wanted to get a handle on how this plane flew. Anyway the engine quit and the glide was nice and slow, took about 2 minutes to glide back down from say 300 feet.

One thing I noticed was that if I let the airspeed down a bit too much, the rudder became ineffective, and had to dive in order to get some air on the fin and regain control. The self stabilizing characteristics were very good with the polyhedral. I didnt get to do any stall tests though...was busy fighting the wind.

I guess that something like this could make a nice budget trainer if you have access to 2mm coro. A .15 would pull it around with a bit more authority than my 10, but that wasnt my goal. I wanted a glider that would climb to altitude on its own and then go hunt the thermals. On good days, this plane would be nice for all around lazy flying. Bring a lawn chair to the field and relax.

It came out at 3 pounds even. I swiss cheesed the tail, but had to add a few washers to the front for balancing cause I put the servos on top and I couldnt move the wing any further back. Building a rail fuse or coro fuse for this would probably save some weight over the canadian pipe I used. I like it this way though...I feel as though I'll be flying this plane for a long while to come."

dbruening80

My Feedback: (1)

sure bet it is easy to tell if it upside down or not! Great looking bird! I've got an old OS 15 FP that is looking for a home, this may just be the ticket. I wonder if I could get by using standard sized radio gear? I would imagine that with the sq ft of the wing a few ounces of standard vs. mini/micro servos really wouldn't matter

Muldoer

No I wouldnt think so. My throttle servo is a Tower High Speed Nano servo. My other servos are Cox/sanwa micros, they're more like Futaba / Hitec mini's in size and weight. If you used a coro fuse instead of pipe I dont think the weight difference with standard gear would matter. Plus you'd be using a .15, which has a bit more power than my 10LA. I was using a 7x4 prop, an 8x3 would absorb more hp and would give greater thrust.

Plus the OS15 is a tad heavier than the 10LA, so adding washers to the nose like I did wouldn't be necessary.

rsieminski

Great work! Might be just the ticket for teaching the little guys to fly with. How slow will it go?

Muldoer

Its really not a fast machine! Slow...I dont know how slow, but...slow. Much slower than a Deb. The little 10 was almost pulling the plane out of my hand, and in the wind I could feel it wanting to lift off. I could have caught it on landing.

But like I said...If you let the airspeed down too much the rudder loses its effectiveness. In other words, it didnt want to turn at all if it was going too slow. I dont know if its like this on all rudder only planes though. Guess I'm just not used to it.

rsieminski

Yes the slower the the airspeed, the more sa the control surfaces need to have. I will def. increase the SA and % of rudder.
Thanks, great design! Just the thing I need.
--Rick

Muldoer

Well the rudder is already pretty big. Its 3.5"x8.5" on mine. But give it a try. You never know.

dbruening80

My Feedback: (1)

possibly the long nose moment is making the rudder less effective at slow speeds. I guess I'm thinking of a rod running vertically thorugh the wing/fuse at the cg, seems as though the larger the mass in front of that point, the more force it would require to move it than if that point were further up on the fuse.hmm............now i think i confused myself, maybe one of our aerodynamic brothas' can chime in on this one

dbruening80

My Feedback: (1)

hmmm, now that i look atthe pics again, the nose isn't that long....

Muldoer

With the wing on, the nose is 13" long and the tail is 19" long. So from the tail the CG is at 25", which is a big lever if you ask me.

rsieminski

Like this:

It'll spin like a like crazy. AUW was 3lb 4oz.

Muldoer

how big is that rudder?

rsieminski

I just cleaned out the garage, and rtired that one, and most of my other birds to the garbage can. It was a good 65% of the total vert SA, with 45+ deg of deflection. Has to be set on dual rates with expo. It was a fun little plane.

jessiej

Nice, Muldoer. Looks a bit like a downsized Butterfly. Bet it flies like one too.

jess

Muldoer

Dont know...never seen a Butterfly before...

Hey rsieminski, I have alot of stuff that has to be thrown out too...only thing is I like to keep things "in case I need them later" but I never need them later. My work table is like [sm=drowning.gif].

Just wish I had more friends that wanted to participate in this hobby, then I could give all my old stuff to them.

jessiej

Kitted by Dynaflite. 99" span. I built mine in the mid 70s. Still fly it with the original HB 20 engine. 99" span. I think Tower sells the kits.

jess

ChrisSpad

i used to have a dynaflite piece o' cake, which is a scaled down butterfly. I forget the span, i think about 80", though. At any rate, it originally flew with an 049 and alot of lead in the nose. A 15 was way plenty. Ended up giving it to a flying buddy, and he's still flying it.

Muldoer

Found it. The Piece o' Cake.

http://www2.towerhobbies.com/cgi-bin...?&I=LXE615&P=7

Apparently 72" span. And the nose is pretty short, accounting for all the lead you had to put in it Chris. Its hard to say if the a spadded Butterfly would scoot with a 10. On my motorglider I can feel the engine wanting to pull the plane, but it needs a good toss to get up there.

I knew about the Butterfly Jess, what I meant was that I had never seen one fly before, so I couldnt really comment on the flight performance.

ChrisSpad

I'm sure its just like the one Tower has - i gave it to Chunky C - he likes the gliders. I don't, lol. Too high in the air for me to see comfortably.

jessiej

Altitude is a problem for me too, Chris, unfortunately, as I love climb and glide events as well as freeflight. That, in my case, I suppose is an advantage of models such as the Butterfly and various Oldtimers- anything that big is easier to see!

jess

Muldoer

Update:

I flew it for a couple flights again this weekend. I've been out of the flying loop for a little while as I am job hunting. I moved the CG a bit farther back, and now this thing climbs like there's no tomorrow. Only thing I did was swap out the fuel tank for a smaller one and since I had changed the battery pack for a AA sized one, I decided to remove the nose weights I had added. The prop is now an APC 7x4. That little prop hauls way more than the top flite wood prop I had on it before.

Unfortunately I flew it on a grey cloud covered day, so I cant say if it thermals or not. With a good headwind the ground speed was zero knots. With the throttle reduced the ground speed was -2 knots. Its really weird to see an airplane going "backwards" in the air.

I'm still getting used to the rudder only control. Its kind of funny in the air because you can see the effect of adverse yaw when I give rudder input...the tail wiggles a moment then it starts to turn in the direction I want it to. Did some stall tests too. It stalls smoothly and recovery is almost instantaneous. On stall it just points the nose down and builds up its airspeed again. I just have to go flying it on a sunny day to see if I can catch some thermals. [8D]