What's a Bitstream-II, you ask? Well, that's just what I'm calling my electric sailplane experiments. The first in the series, Bitstream-I, was built years ago in Hawaii, using RG-15 foam wings sheeted with obeechi plywood, and a balsa/ply fuse. It had a straight 55" wing, with upturned tiplets. It flew ok on a 4:1 geared Speed 400 and 11x8" Graupner folder. It was a tough little plane - high enough wing loading to be fun on the slope, with a little power to get home when the lift was light. But WOE be unto he who let it slow down. That plane tip stalled something awful. The second photo below is the original Bitstream, now retired. Handsome little bugger if I do say so myself!

This thread will track my progress on Bitstream -II. Basically, this project is a combination of bits and pieces I have around in the shop which I think might make a neat little e-sailplane. Bitstream-II will be a full house 2m electric with built-up wing using the SA7037 airfoil. The wing is a slightly modified Spirit Elite wing, reinforced with carbon fiber, kevlar, and some additional shear webs in the right places. It is going to be a t-tail. Motor will be the AXI 2814/12 spinning around a 12x8 prop, and 2600mah Lipo batteries. My target is 45 minutes airtime in calm, no lift conditions. It is not a hotliner, but more of a sporty plane with a solid 45-50 degree climb, light enough to thermal well, strong enough for mild aerobatics, or to dive from speck altitude.

In the first photo below, the right wing panel is framed up on the workbench. You can see the CF tape, which is laminated to the inside of the spars. The spars are sanded down to compensate for the thickness of the CF tape. The plywood joiner that joins the inner and outer panels is also laminated with CF.

The fuselage in the background is an old fiberglass electric fuse that I've had kicking around the shop for years. I don't even remember where it came from. Perhaps someone can identify it?

So, here goes! All comments appreciated.

--Jim Laurel
Redmond, Washington, USA

I am looking forward to watching your progess Jim, that is a nice looking wing. Is the construction of seperate top and bottom spare with the carbon tape on the inner surfaces?

On tip stalling..... is the second photo of the Bitstream I? In my 'Hitcher' series of designs 'Hitcher3' used a tapered wing with a straight trailing edge which was at 90 degrees to the fuselage. That wing had a sudden stall if you waited too long.... Then I read an article about the use of the Schuemann planform on full size and model wings.... that suggested that a straight trailing edge at 90 can be trouble.

Graham

Any progress?