About three years ago I had mentioned my interest in such a configuration to the Volvo rep at the Ft Lauderdale show. He said I should come visit them in Norfork. I never did take the time to follow up on that invitation. I suspect they have been working on this for some considerable time.
I had previously suggested this idea for both single and/or dual props, but utilizing a kevlar belt drive component rather than 90 degree shafts:
From my website,"Other than direct straight-shaft drive of propellers, most marine drives today involve some sort of 90 degree arrangement, ie.sail drives, stern outdrives, outboards, etc. The 90 degree gear set (and there are usually two sets) is the potential weak link in the system. All the power is being transferred over a very physical small contact area between two bevel gears. This contact patch can be nothing more than a thin line on the opposing two teeth! Special hardened gears and maintaining close-fit tolerances permit the horsepowers of today. But when it comes to diesel engines, the situation gets worst. The diesel is by its nature a much more torque'y beast. Gears to handle an even modest horsepower diesel are extra hard pressed. Teeth can break or get worn so quickly as to loose all tolerance."
Volvo is talking some fairly big diesel power here. I can only think that the smaller dia props (dual configuration) are a factor in making it work, but I still have trouble believing it. I wish them the best of luck in a successful product.
PYI is now using a Morris chain drive component in lieu of the kevlar belts:
http://www.pyiinc.com/?section=drive_leg&sn=1
I still believe the kevlar belt idea merits research, particularly in this forward facing config., and as simplier, less expensive possibility. Couple of older references on the belt subject:
http://www.boatdesign.net/forums/sh...681&postcount=4 http://www.boatdesign.net/forums/sh...12&postcount=11