QL trim tabs or classic trim tabs??

i wonder are these new trim tabs from volvo penta better from classic trim tabs with hidraulics plates ..my opinion is that they will slow too much small boat because they are completly in verticall position..they will be like brakes..what do you think ???

 

The concept of interceptors, what the Volvo units are technically, is well proven in many applications over decades of use. Mostly in ship and military applications but increasingly in recreational and small commercial vessels.

They both work to provide lift, traditional trimtabs do work better at slower speeds which for many vessels is where trim tabs really shine and where real fuel savings can occur.

The Volvo units are also electro mechanical, as compared to the Bennett Hydraulic system for example. The hydraulic system has only one moving part bolted to the transom, the hydraulic cylinder piston rod. All the electric components are located inside the boat in hopefully a dry area. The Volvo units have electric components at the transom below the waterline.

I have seen situations where interceptors work very well. In one case a tender on a yacht where not having traditional tabs made sense for on deck storage.

For reliability, outstanding engineering and excellent customer service it's really hard to beat Bennett trim tabs. There may certain niche places where the interceptors may make better sense, but I doubt they will have the reliability or longevity of a Bennett system.

As a yardstick I have seen Bennett systems 25 years old encrusted with multiple layers of barnacles that have never seen any kind of service, and that work. I've never seen or heard of an electro mechanical system, trim tab or interceptor, that can or has done that.

Steve

 

There are also humphree interceptors. Servo is inside hull with shaft through transom to composite interceptor mechanism. http://www.humphree.com/products/interceptors/

See the info posted by Commuter Boats here too:
http://www.boatdesign.net/forums/boat-design/stern-flaps-interceptors-36540.html#post440016

 

Not 'better' in the hyrdodynamic performance sense, but very nearly the same for many applicatons, particularly higher speed ones, as another poster correctly noted.

Your intuition about 'water brakes' aside, rest assured that an interceptor is, instead, a very effective device for efficiently producing lift at the transom. When deployed, the blade 'intercepts' the flow in the boundary layer region and 'converts' the local dynamic pressure to static pressure acting on the hull bottom in the region forward of the interceptor blade. That region of pressure is your lift.

 

Have experience with Volvo interceptors on 35-40 kt sport fish boats. They are very effective and have a huge advantage that they don't tear off if you leave them down when backing down on a fish.