Outboard Fins (hydrofoils)

[Storyline]

It was recently my birthday and I have a few quid sculling around that I need in order to buy a present for myself (my mother likes to know she has got me something tangible). As we have been sailing for so many years we have got all the cheapish type stuff and our wish list comprises of items with three zeros minimum.

I have always been aware of the fins you can get to attach to your o/b that promise a great improvement in performance . We have got a 5hp Tohatsu 2 stroke. This is a lovely motor and really powerful for its weight. It can get my wife and I up on the plane in our 2.8m Avon Rover air deck. However this is only in completely flat water. Anything more than a few ripples and then we struggle.

Would the fin make a big difference as claimed ?

http://www.force4.co.uk/force-4-outboard-hydrofoil-up-to-50hp.html?#.V1F0a7grJaR

 

[Carmel2]

I have alway asked myself, why don't outboard manufactures make the fins that size in the first place?

 

[Hadenough]

They have many detractors but they work. Made the difference between planing or not with my 2.7 RIB, dryer ride too as the stop a lot of prop splash over the transom. Main problem is that they make the outboard cumbersome off the dinghy but I leave mine on in the davits.

 

[TQA]

Yup they work.

 

[bignick]

Also consider "lifters".

http://www.maximarine.com/products/lifters/

I fitted them to my old ribtec 280 rib and they were superb. Planed earlier and no ridiculous bow to the sky attitude during acceleration. Highly recommend them. (No association, just a very happy customer.)

 

[geem]

Spend your money on a bit of 6mm marine ply and make your own. The ones you buy are too wide usually and not long enough. We have used a plate for the last 12 years on a 9.8hp tohatsu on our rib. The plate starts out as 400x400mm and is cut into home made fin. We simply painted it and bolted it through the anti-cavitation plate. I took it off last week to paint it and coudnt believe how unstable the rib felt without it. Plans faster, stays on plane at lower revs, doesnt drop off plain, keeps bow down in a chop. Our sogs also use it as a step to climb put of the water on to the rib when they have been swimming

 

[Storyline]

Those Lifters look great and the testimonials make very encouraging reading. Am going to invest when we have our davits installed as we would have to take them off each time we use the dinghy now. Thanks for the feedback everyone

 

[jac]

I'm assuming you could combine lifters and the fins. Anyone done it and does it make a difference?

 

[bignick]

I think you would struggle. The normal method of determining the correct vertical placement of the outboard is to set the anti-ventilation plate to be level with the keel line. If you do that then the hydrofoil fins would also be level with the keel line.
The lifters are just like oversize trim tabs, and mount just above the lower transom edge. I think you would find that they may clash with one another. Even if they didn't physically clash, there may be some interesting interactions between them.

 

[Storyline]

I also wondered about combining them but came to the conclusion that they would probably clash with one another. Having now read various reports on the two systems it seems to me that although they are a lot more expensive the lifters are the way to go.