freakingfast

My Feedback: (3)

Had a funny dream, I was flying this mongo sized DD and it was quick …..then I woke up.
A fast giant DD? that could never happen, but I couldn’t shake the Idea. So I started doing the math to prove it wrong. But now it seams plausible.

First, what power plant? It has to be light weight so a two stroke glow is it. It’s got to be big and on hand, so a Mark (Moki) 2.10 is what I got. Weight 40oz., well its relative LOL. Powerful, It’ll swing a 16X16 @ 9,600 rpm with a full length tuned pipe on 5% nitro giving 26 lbs of thrust. And it’s still under the maximum safe prop speed of 11,875 rpm, on the ground at least. So far so good.

Based on the engine, pipe, tank and receiver system + plus air frame, how big would this thing need to be to get the same wing loading as my standard DD that flies great despite the its wing loading is a tad high at 11.3 oz. sq.ft. Well, it works out to be 140oz. (8 ¾ lbs)
Now this is where I got surprised, in order to get 11oz loading it needs to have 1819 square inches of area! To keep to original DD shape but scaled up the wing span would be 60” the length 45 ¾” and the wing tip cord 14 7/8”. Dat a big delta!

How fast will it go? Well according to Andy Lennon’s speed nomograph it looks to be about 170 mph, but I think that’s optimistic. My guess about 155mph.

Now I like to slam hard turns, so what kind of servos do I need. Well each eleveron is 2.8” wide by 29.3” long and it will deflect to 40 degrees at 190mph (for a dive, worse case + safety margin). Another surprise, it would need 624 oz.-in. of torque! That means two servos per control surface and a large battery to feed them. So I had to recalculate the plane’s weight to what you see above.

Please feel free to comment or cut up this dream….err..a… nightmare.

Lomcevak Duck

My Feedback: (14)

You'll need to make the wing three pieces to transport it is what comes to mind first. A center section, two outer sections with two carbon fiber tubes and you'll need to make the elevons four pieces with one servo on each section, split them at the wing separation point and put one servo in each outer wing section. Too big to hand launch, so you'll need to do tricycle landing gear...

To keep weight and cost down those ENORMOUS ribs should be cut out of 1/2" insulation foam and caped with 1/16" balsa, definately two rudders, and for heaven's sake don't use a diamond airfoil. Use something a little thinner and smoother.


You're not the only one who's had that dream and then thought about how to do it. I just haven't gotten around to doing it.

soarrich

My Feedback: (98)

http://a123racing.com/

You can run an arc welder with these, no drop in voltage 2300 mah 6.6 volts The guys with big planes say you can run a 14 servo plane no problem, I've used them on my 50cc 7 servo plane no problems. A123racing.com have a full size electric motorcycle that does 8.20 at 155mph in the 1/4mile, you get a running start so you should do at least as well.

http://www.troybuiltmodels.com/Servo****ec.htm#HS7955

These will supply the power you need.

Lomcevak Duck

My Feedback: (14)

For some reason I did not notice you said 60" span in your original post, I have been thinking about something like 80" or so for the OS 1.60 FX. 60" is just larger than the BTE Vortex, at 54". They have been clocked around 125 I think, and fly with a .91.