Top Of Sponson Design

[Aaron Lavigne]

OK so you have the same AOA degree for example 3 degrees from water surface to bottom of running surface at speed. But the top of the sponson is either parallel to the water line or angles down (closer to water line in front than rear, no parallel) at speed. What would be the reason for each difference? What are some characteristics in hull performance? Should the top angle of the sponson be scribed with the top angle of the tub?

 

[Aaron Lavigne]

I measured a sponson to have 6 degree planing angle degree for 3-1/2" before curving upwards to sponson nose. That is measuring off of a flat sponson top which would also be parallel to the water line. But when the sponson is mounted on the tub, the top of the sponson is not parallel with the water line, it is angled down decreasing the planing angle from 6 degrees.

For example, the planing angle was decreased to 3 degree when installed on the hull. And the top of the sponson still angles downwards, not parallel with the hull. How does this design differ than having a parallel sponson top with 3 degree planing angle on and off the hull?

 

[Aaron Lavigne]

Any thoughts on this????

Because I feel that a 6 degree planing angle is very high, usually riggers are around 3 degrees...so you angle the sponson down that far seems very dramatic to acheive that AOA when on the boat.

Seems like it would cause a lot of drag on the back on the sponson???