View Full Version : Volvo Penta speed rails

Dale R. Hamilton
11-26-2003, 09:39 AM
Saw something in the Volvo catalog- "speed rails are aluminum extrusions installed on boats lifting stakes that reduce friction, offer higher speed, better fuel efficiency, better maneuverability, better ride" So how about it- anybody got any experience with this sort of thing.

John E Hardiman
11-26-2003, 10:49 AM
Speed rails (TM) manipulate the lift of the existing spray rails. This is not new technology, but the old hooked spray rail configurations tended to be fragile. They help some boats, mostly deep-V hull is smooth water by lifting the hull higher to reduce wetted surface and possibly injecting some air (but then they don't lift as well...pay Peter or pay Paul). Additionally, the generate significant lateral force. As long the boat is going fairly straight they balance. They are fairly benign is wide sweeping turns, but can cause problems in high heel tight turns. Additionaly, because they generate lift by a jetting process that works better as speed increases, they have little benefit to slow speed or heavy hulls.

The designer website is Ocke Mannerfelt Design (http://www.ocke.se/) . Go to Motorboats/the technology.

Dale R. Hamilton
11-26-2003, 11:11 AM
good answer John- I have a moderate V flying bridge cruiser- 12 degrees deadrise I believe- with no strakes, skegs, or whatever on the bottom. She seems to do just fine- gets 50 mph easily, behaves nicely in turns (even with 2 good size men on the flying bridge. Still- Volvo promising better this and that makes me think about it.