jet boat leans at speed

[jumjum01]

Hi. I am new in the marine world. I build a small aluminium boat with a seadoo 3d pwc engine. I basicly took the complete driveline and fitted into this alu boat. I run great, but the problem is that is at speed it leans to the starboard side. The greater the speed the more it leans. The impeller turn counter-clockwise. The hull seems pretty symetrical and the boat seems to be in balance.

Kristian from Denmark

 

[fatboyroy]

Did you try to counter the lean by shifting weight to port side? Fuel tank driver seat etc?

 

[jumjum01]

Yes, then it leans to port at low speeds.. It seems like the motor is (torque lifting). But the jet drive should even that out. I have never seen a jetski tilt at speed, so I dont understand why my boat does it..

 

[fatboyroy]

Maybe you need trim tab or research on tiny boat like this YouTube cleetus McFarland build many of this u can try to message him or put comments in his channel

 

[TimW451]

@Cobra Jet Steering LLC You can solve it!

 

[FSH 210 Sport]

Yes, then it leans to port at low speeds.. It seems like the motor is (torque lifting). But the jet drive should even that out. I have never seen a jetski tilt at speed, so I dont understand why my boat does it..

I definitely think it is torque tilting.. your boat barely has any draft at least looking at the pictures, and when you get going there is even less, so it is going to settle onto the starboard side at speed… you might just need a couple of fixed trim tabs out back on each side, or a set of motorized ones that you can adjust independently to get rid of that lean.

 

[AZMark]

Cool little boat!

 

[Cobra Jet Steering LLC]

@Cobra Jet Steering LLC You can solve it!

He needs a special ride plate built for it. I did some for my new Yamaha skies because they have a really bad chine walk that wants to throw you off around 20 mph TOP secret though can not show pictures of it but if you saw it you would do a HOMER SIMPSON instantly DOH however there is a reason p w c's have sponsons and the correct design would probably solve the issue

 

[tdonoughue]

... or simply redesign the boat to have 2 jets. With counterrotating engines, of course. Should be simple. [ha!]

Or, in addition to the above ideas: ballast and/or a keel might help.

Neat little boat. Would love some more pics of it...

 

[jumjum01]

Thanks for all your answers.. It seems the best solution might be a different or modyfied ride plate. As an expirement I will try and make the plate angle adjustable sideways, to compensate for the torque tilt. I kind of mabye makes sense the at higher speeds, when the boat planes, the drag area of the boat becomes smaller and most af the balance will rely on the ride plate.. so a ride plate angled clockwise might be able to counteract the cc torque

 

[jumjum01]

More pictures..

 

[fatboyroy]

checkout their design seems like swim platform in the back instead of ride plate does it for them but it’s rotax engine not sure if that makes any difference