proper weight distribution?
 

hey everyone!

I am currently making a scratch built, small delta wing that has a EDF mounted at the rear of the wing. Now, for the last four days I have been worrying over if the wing would come out to be tail heavy with that EDF back there or not, in other words, I have have only an educated guess as to how much weight would haft to go in the front of the CG as opposed to behind it. what other information would you guys need to help me out?

RE: proper weight distribution?
 

perhaps a formula that could tell me the correct CG point for delta wings could help alot.

RE: proper weight distribution?
 

You might search this forum for topics on location of the mean aerodynamic chord, or MAC. I believe the tools sticky at the top of this forum has some calculators. Also, search for neutral point, or NP. For a flying wing, the neutral point is at 25% of the MAC. I've built several flying wings, including a delta, and I have had success by locating the cg at a point that is 5% (of the MAC) ahead of the neutral point. Others may use a bit more or less, but that has worked for me, fwiw.

RE: proper weight distribution?
 

The simplest way would just to remove all the radio gear from your plane and add weight to the nose so that roughly 20% of the area of the wing is in front of the C.G. If that is not convenient, you can make a small scaled down profile balsa glider of your plane and balance it in the same way. You may find that you can move the C.G. back as far as 25%, but 20% is a good, safe place to start.

RE: proper weight distribution?
 

thanks Bobbler and Craig! I did build a half scale version of this wing, I hope you can see the pics. the balance point i found on the 1/2 scale version is about 5in from the nose of the wing, where you see the spar, thats where I had it balanced. It did glide well with about +3 deg on the elevons.

RE: proper weight distribution?
 

You'll want it to balance at about 22 to 23% of the MAC or Mean Aerodynamic Chord. There's links to sites that help you to find the MAC in the sticky threads at the top of the listings here in this forum.

RE: proper weight distribution?
 

back from a month and a half of work on this wing and I am almost finished. you guys really helped me out with the weights. right now the wing weighs 22ounces (with electronics installed). the only thing I need to do is make my elevons and install my control links and lines. I will get some pictures of it.

but now I have a new question. how in the world am I going to launch this baby into the sky? I could hand launch it, but I am afraid that I wont be able to launch it hard enough to stay in the air and cause it to stall out and bite the ground. any ideas on this?