sponsons VS tub

[iceman]

Hope you guys can help me with this. when mounting the sponsons to the tub on a rigger how much lower then the tub do you want the planing area of the sponsons? Do you want the same on the rear sponsons? and lastly, how many inches do you want from outside of tub to inside of sponson? thanks for all the info in advance.

GARY

[Boaterguy]

You want the hull to be level when on plane, So the back sponsons should be below the tub equally as much as your rear sponsons/ski.
I've never seen a formula or measurement for the tub to sponson, the wider the stance the more stable it will be, but there must be a few disadvantages.

[iceman]

how much below the tub should sponsons be?

[Boaterguy]

No idea on exact measurements, but mine ran at around an inch, although I never got above 25% throttle

[iceman]

Boaterguy, why only 25% throttle? you think 3/4 would be enough?

GARY

[Boaterguy]

it was the first run and I hadn't soldered the collet, next run it sank so I stripped it out (after a nice chilly swim) and put the guts into a hydro.
i would probably be enough, but once again I'm not sure, I don't know how but some people make it adjustable.

[iceman]

how much below the tub should sponsons be?

Anyone else have info on this? come on now dont be shy. help a fellow out!

GARY

[siberianhusky]

No offense dude, but I think you're on your own, you designed it and built it, this should all have been part of the original design process. There are so many different designs out there and different sizes there isn't right generic answer for your question.
There is a 99% chance any answer you're given will be wrong, all I can say is the tub should be level when at running attitude, prop depth, sponson lift, hull lift these are all variables that nobody can answer for you. There is a very fine line between a rigger that runs like it's on rails and a real dog, just changing the turnfin angle a degree can make the difference between a boat that turns great and one that lifts a sponson and cartwheels in the turns.
They look so simple but riggers are the F1 cars of the boat world, and just as sensitive to changes and design flaws.
All you can do is try something that looks right and be prepared to change it, part of the design process, the first try rarely works as people want it to.