Quote:
Originally Posted by seuadr
from this thread: HERE
i saw this recommendation on angles:
that seems like a very reasonable taper - but, i'm not sure about the chamfer - should it just be a straight 45-deg or would a curve between them be better? (or better enough for the effort vs the 45, which would be a lot more straight forward?)
the top to side corner(s) already have a chamfer that i could taper from possibly? would look better at any rate (assuming i don't do a bad job anyhow...)
Either way i plan on mocking something up with wood and sheeting - maybe even cardboard so i'll have some practice... |
The General Motors 'OPTIMUM' boat tail had all-radiused edges, however, was designed specifically for a trailer van with matching upper edge radii. GM used a radius equal to 7% of the trailer box height.
Since your bus already has the softened edges, it would make sense to integrate the tail into those.
GM's tail was 20-degrees downslope, 10-degrees plan-taper, and 10-degrees diffuser.
GM's tail length was 93% of the box height.
All edges, top, sides, rear, and bottom were softened with the same radius.
In Thomas Scott Briedenbach's US Patent # 8590961, he does the same thing. He used 12-degree upper, 12-degree sides, and 9-degree lower.
On my first trailer, I ran large Schedule-40 PVC pipe through a table saw and used the inner surface as tooling to create wet-layup FRP radii. Polyvinyl alcohol and 3-coats of carnauba wax made for a clean release.
It amplifies the fabrication man-hours, but kills edge vorticity, which can be a source of relatively high drag.