Originally Posted by
crossman
I have been flying glow, mostly a 40 trainer for a few years, but I have been considering an electric sailplane for awhile and these plans have caught my eye.
http://www.modelaviation.com/thermix13
Since I am new to sailplanes, I do have a few questions about the plane. It seems like this would be somewhat over powered with the motor that is listed, am I missing something about sailplanes, or would something around 450watts be enough? is there anything about this plane that would not be good for a first sailplane? I do enjoy building, both kits and from plans, I have also looked at the Great Planes Spirit kit. Any advice is welcome, thanks.
Welcome to the world of RC Soaring.
First about the weight The specs say it is 64 ounces which is exactly 4 pounds. His wing loading says 10 oz which would imply 67 ounces. Close enough to say that it is nowhere near the 5 pounds that someone posted.
AT that weight a 450 watt motor would be more than adequate. That would put you at 112 watts/pound. You should get a crisp climb of at least 45 degrees and maybe steeper. However I see he has the motor and battery all the way up front so they may be there to balance the glider. If you go to a lighter motor you may want to be sure to offset that with a battery that will balance the glider.
While Dick says you could put a 4000 mah pack in it that would probably be around 14 ounces. That is a BRICK! Unless you need that heavy battery to balance the glider I would run an electric glider on much less, say 1300 to 2200 just to save weight, but that assumes you can balance it with a smaller pack.