Modern Hydroplane Designs

[jpro60]

Hello All,

I see in pictures of stepped hulls, stepped sponson's and recessed areas at the transom. Other things like the cockpit sides going past the transom instead of being flush are things we want to know. Not only just do it this way, .. but why it's done that way are what we would like to study on.

While I'm hardly much of a boat designer, I have built many boats fairly successfully. I've also helped design, or modify existing designs. I'll offer up answers to your questions the best I can but understand that in most cases the answers are based on anecdotal evidence only.

Stepped hulls - Hopefully Sam Hemp could chime in on this as he is probably the guy who uses this the most in his designs. I believe the idea in most cases though is to help create an area where you force the separation of water from the hull.

Stepped sponsons - The idea here is to minimize drag when the sponsons touch the water. For instance lets say you have a 6" wide sponson with a 3" step. If the sponson only touches the water lightly then only 3" of the sponson touches the water and you have half the drag. If the sponson touches the water with more force then you've still got the whole 6" of sponson there to support the boat.

"Recessed" transoms - I think a more common term would be "inset" transoms. The basic idea here is to put the "bullet" (leading edge of gearcase) a certain distance from the bottom of the boat. Different classes/motors run better based on this distance. You can also change handling or motor cooling characteristics by changing this distance, and in fact I've also seen transoms there were stepped back further away from the boat. (note- I'm assuming you're referring to the motor board when you say transom)

Cockpit sides going past the motor board - There's more than just flimsy plywood back there. There's an extra thick piece of wood back there to brace the motor board and make the joint with the cockpit sides stronger. I think we use a piece of about 3/4" spruce.

Hope this helps,
Mike Perman 32-R

[johnsonm50]

While I'd agree that building is a satisfaction of its own there's usually a good boat or 2 for sale & often the best deal going. You could buy a reasonably competitive boat & go race or fun run for $500 to $1500 most of the time.

[Fast_ditchey]

Thanks Dave. And yes, I know Larry, we have talked, but not about building a new boat yet, more just about racing and old videos. I will be sending him an email soon.

[BillCNC]

Thanks guy's, ...

I have been reading up on hydroplane design and would like to be armed with current knowledge for either buying a boat or building a boat for racing from a current racers point of view but was wondering from you individual racers, ... What features do "YOU" find important in a hull design and what areas "YOU" think needs improvement?

Bill

I have been reading up hydroplane design and would like to be armed with current knowledge for either buying a boat or building a boat for racing from a current racers point of veiw but was wondering from you individual racers, ... What do "YOU" find important in a h