Some more views representing some design decisions.
My current design for the upper cabane mount is to have two ribs cut from 1/8 lite plysandwiching a 1/2" x 1/16" flat aluminum strut I plan to bend to shape. I plan to mount it with a 6-32 screw + washers + locknut. This is one of those "measure 10 times drill once" things where the wingincidencewill be set and that bothers me. I'd rather have a slot in the metal but am afraid of slippage in flight, would I have to crank it down so hard it would crush the ply? even with generous washers? a lock-washer even? I think I'm safer with non-adjustable but that is not set in stone. I am planning on 0-degrees for top and bottom wing but would like that to be adjustable for triangulation-trimming.
Next up the firewall. A little unconventional, a 1/4" ply doubler is behind the front fuse former. I started with a huge air baffle behind the engine and have taken great pains to maintain it. I want gobs of cooling and plenty of airflow to carry the smoke away from the plan in hover.
The rear profile shot shows some design decisions I made early on that may or may not haunt/kill this design:
- The wings have as large a separation as I could manage. The bottom wing is practically flush to the fuse (the line you see there is the center of the rib). I am hoping this reduces the venturi-effect between the wings, and minimizes interaction. In addition providing slightly large torsional moments for the roll axis.
- The rear fuse is very thin, getting the taper right on the entire radial axis for this was a royal pain let me tell you, but I think I have an approximate airfoil. The main idea is to push the center of pressure forward for stable knife-edge flight. That's the theory anyway. The reduction in material is minor.
- Thestabilizeris centered at the halfway point between the wings. Originally I wanted to make sure the air coming off the wing surfaces affected it as little as possible, but the wings are staggered so my gut says it should be a bit lower to really achieve that. But then how does p-factor affect this? Does it matter? Should I be moreconcernedwith the thrust line? These are maddening questions because 3D flight is really not covered in the literature. Tail plane design is all centered around proper authority in imminent stall conditions. Okay fine I want it to harrier well but is that a function of just the tail design or more due to obscene power/weight to just muscle through?
- Can't really see the rudder but I pretty much figured "more is better" as long as the large surface was as close to the thrust line as possible to avoid the p-factor blowing the model sideways. I have compared ratios to known-good 3D designs and I am pretty sure I'm in the ballpark.
The more "finishing touches" I put on this design the further from done I seem to be. I really wanted this out for laser-cutting
quote this week.