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Old 29 September 2016, 03:16   #1
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Hydrofoil Fins

On ebay you can buy small hydrofoil fins (4-40 hp) for £17 on my other bigger boats I have. Fins but they were always fitted so no idea of any difference

On my little 3.4 m valiant with 15 hp mariner 4 stroke I was thinking of fitting these small fins. It is not the cost but IDont want to drill the plate if they will make no real difference.

Have any of you got experience of these on a small set up. I don't have Ptt

Thanks

Dennis
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Old 29 September 2016, 03:29   #2
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These seem to be a Marmite thing.

I've had them already fitted to one used outboard and they came unfitted with another outfit and as the OB was already drilled I tried them.

To my mind they are a sticking plaster for a bigger setup problem and not needed if everything is matched and set up properly.

In my experience I didn't like the downsides which were a lower top speed and draggy feeling in the steering which at times felt as if you were stuck in a rut.

Just my thoughts and related to use on 3-4m smallcraft/SIBs with 10-20hp motors.... others may have found more benefits.
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Old 29 September 2016, 03:30   #3
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"real difference"

What are you trying to achieve with doel fins?
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Old 29 September 2016, 04:04   #4
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BP you mentioned in another thread your outfit will plane nicely at 11kts with minimal wake... and make 20.5kts tops... that sounds as if it's well set up already.

Also just looked at your pics in the "34 mile passage" thread. Your console is well forward giving a near level attitude that looks fine. Adding fins is quite likely to push the bow down too much. That's what they did with one of my boats... a 4m hard hull with 20hp.
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Old 29 September 2016, 09:37   #5
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Quote:
Originally Posted by Fenlander View Post
BP you mentioned in another thread your outfit will plane nicely at 11kts with minimal wake... and make 20.5kts tops... that sounds as if it's well set up already.

Also just looked at your pics in the "34 mile passage" thread. Your console is well forward giving a near level attitude that looks fine. Adding fins is quite likely to push the bow down too much. That's what they did with one of my boats... a 4m hard hull with 20hp.
Thanks for the info My little boat does seem well set up but just thought they might help. I think I will leave them off for noe
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Old 29 September 2016, 12:45   #6
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I've used one wasn't impressed I agree with fenlander sticking plaster they add drag as said.
you can buy them which don't need drilling which is a plus if it don't work you haven't defaced your motor.

Cheers
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Old 30 September 2016, 11:31   #7
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I've used them on a 4m Avon with a 40HP - the set up was very stern heavy, - console with, rear bench housing fuel and battery. Took ages to get on plane with boat on a very steep angle. The doelfins made a huge and positive difference in that case.

It will depend on how your craft is set up, if it gets on the plane quickly and is stable I'd say don't bother.
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Old 30 September 2016, 12:29   #8
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I've used them to good effect........but if it ain't broke, don't fix it.
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