I have some preliminary drawings and let me apologize for the drawing. I haven't "inked them in yet" so the pics were hard to get visible, but here goes anyway.
Front view...

Side view...

I've got a sitka spruce top from Gilet's and a neck blank ready to go from vic ash.

The sides will be solid kauri pine, ie, not bent but cut to shape. The board will be jarrah. The back will also be Vic ash. I have a couple questions for you seasoned acoustic builders as a total novice...
For an acoustic bass guitar;
1. How thick would you make the back? The current plan is to make the back will be 3 piece due to timber constraints.
2. What would you used to brace the back and top? At the mo the plan is to use 2 longditudinal braces on the top ala bass bars and maybe a tressel brace in between the top and back.
BTW, Forster's archtops are very different to regular archtops with a full length neck and a low tension belly. You can check one out here...
http://www.nkforsterguitars.com/instrum ... tar-oscar/
My bass will be headless too. Strictly speaking this will be an electric with some acoustic properties, but I'm trying to get it right none the less.