I've also been playing with this idea becuase active trim tabs are just about *the* most efficient way to add speed to a Deep V hull if you want a fast boat. The Steven's Institute reckons on a 35% speed increase.
While I haven't got around to sorting out kit, there are a few things to think about>
1) Power: The trim tab will need to be pretty strong, and the system that supports them - and the section of the hull that they are attached to, will also need a good deal of strength. The tabs need to push the bouyant bow of the boat down, and this will need a good deal of force.
One mechanism I was thinging about was to to drive each tab from a 10kg servo. 2 would giv som factor of 20kg's of force, which might be enough.
2) speed: There would seem to be significant benefts in mixing the response rate of the trim tabs to the speed of the boat. forward speed will be proportianal to the number of times per minute that the trim tabs need to support the weight of the boat. The trim tabs can be viewed as dampers to an ossiclating motion. By keeping the damping at roughly the same rate as the motion-to-be-damped, there is a significan increase in stability to be gained
3) "Knowing whats happening". In order for the system to be "active", there needs to be a sensing mechanism to know when the boat is pitching, so as to activite the dampers. This system also needs to be proportional - you don't want the dampers at full arc when the boat has only tilted slightly. This - I think - can be done pretty simply with a Heading Lock Gyro - from the model Helicoper world - trned on it's side - it ill also give propertional response, and is cheap enough and very light.
4) Option for trnasverse damping. Active damping gives the biggest benefits - in terms of speed, stability and fuel saving, for straight ahead motion. However, there is also significant benefits in transverse damping. I.e if the boat tilts to port , the damping on that side kicks in to attempt to level it. Ths will give a minor sped increase, but a bigger stability increase, although this increase will be directly propertional to speed - the faser the boat is going, the better this mechanism will work.
Essentially it's just another heading lock gyro, pointing on a transverse axis, and in theory is easy. The issue is that there will rarely be 100% transverse tilts without some form of forwards tilt as well. At this point, you need a micro controller which has code to decide which "tilt" to give priority to controlling. Or built two sets of dampers.
Anywho, dampers are something I definately want to play with. But I've not yet worked out a "cunning plan" to make it work well.
If you do come up with a plan though, the rewards are pretty big though.
Steve