Outdrive question

[Guest]

I have no problem getting on the plane, and I rarely if ever use the tabs. All the stuff I have read about trim tabs suggests that you keep their use to a minumum, since they add considerable drag, whereas a hydrofoil just adds lift. Dunno...

 

[adarcy]

Re: drag

Graham

Anything which gives a lifting force must cause drag but you are talking about 2 slightly different things.
A hydrofoil will lift (and drag) but the benefit on the hull drag ( which is v much more considerable than the outdrive drag) from this lift at the stern maay give a great benefit overall.
Trim tabs work obviously by deflecting water down from the stern thus lifting it but they also change the planing shape and so affect the trim more than a hydrofoil of the same lift would. Again, they cause drag and so should not be used unless necessary but they can have a vast effect on the overall hull drag.
On our Princess45, a few degrees of tab down gives us another knot when on the plane.
In summary, they both must cause drag but still may be worth it for different reasons.

Of course, tilt on the outdrive legs adds another variable.