Effects of fixed trim tabs with interceptors

[meren]

Any thoughts how does fixed (stepped) trim tabs with interceptors effect on small planing craft with noched transom (as seen in the picture)?

[hmattos]

I like the look of that hullform. What do you mean by INTERCEPTORS?

The hull extension seems to have a flat bottom - Are you planning to fit twin outboards?

Have you considered the possible sideslide effect when cormnering hard at speed?

How big is this boat to be?

Good Boating
Hugh Mattos C.Eng.M.I.Mech.E.
www.explorermarine.co.uk

[meren]

Yes! I´ve thougt if possible sideslide effect might occure in turns and also ventilation problems caused by waves preventing air supply for "tabs". In this case ventilation for "stepped tabs" is provided both from centerline and chine directions.
So witch method to use in designing this kind of stern? How to calculate effects on trim, lift and drag and so on with "stepped flaps". Savitsky has equations for wedge design, but now the pressure contribution in stern is different when there is a step.
In semiplaning vessels stern flaps has gained topspeed few % and cut down fuel consuption up to 10%.

This design is 23 ft sportsfisher with one outboard (115 - 225) fitted.

With interceptors I mean 300 mm QL-trims.

[gonzo]

What is the reason to install fixed tabs? A hydraulic system is cheap.

[Willallison]

As Gonzo suggests, there are far more reasons to fit movable tabs than fixed ones. The only real benefit to the 'pod' type tabs that you show is that they provide buoyancy when at rest.

[ABoatGuy]

Speaking of tabs. Has anyone tried the Volvo interceptor tabs? Roughly the same cost as Bennett tabs, buy they are all electric, completely plug and play with a pretty decent panel with LEDs to show deployment. Much simpler tooling if you are going to recess them. On a sport fish no problem backing down on deployed tabs!!