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Old 17 September 2006, 15:49   #1
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Advice please

Thinking of buying some hydrofoils for my rib as I get cavitation easily on tight turns. Can anyone recommend which type to go for? Anyone got any experience of these things, good or bad?
Narrowed it down to the following 3 types:
pic 1: doel fin
pic 2: whale tail
pic 3: SE300 turbo
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Old 17 September 2006, 15:58   #2
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My previous Rib was a Flatacraft Force 4 that I dropped a 55HP Suzuki triple on the back of.

First time out it was all over the place, as I think little or none of the boat was in the water at full chat.

I fitted a set of Doel fins which transformed it.

Not your issue I know, but still recommended.

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Old 17 September 2006, 16:27   #3
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Are there any fins that just clamp on as apposed to bolted on. I'd hate to have to drill holes in my beloved outboard.
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Old 17 September 2006, 17:15   #4
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Holes ...

Andy

It might be worth checking your outboard but on both my mariner and yammie outboards, the holes were already there - presumably in the casting at the manufacturer. My only comment is that whilst my set of fins claimed to fit my yammie in fact part of the plastic just fouled on the trim adjuster/anode tab. However this was easily solved by taking a hacksaw to the plastic of the fins and in 5 mins all was fixed.

Regards - Andrew
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Old 17 September 2006, 17:31   #5
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Have you tried trimming down on tight turns?
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Old 17 September 2006, 18:20   #6
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Quote:
Originally Posted by Limey Linda
Have you tried trimming down on tight turns?
yes, motor trimmed fully in.
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Old 18 September 2006, 16:50   #7
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I used Doel fins on an hard boat I had years ago, but that was to achieve stern lift when a bit loaded up. They worked very well.

Have you checked the actual engine height? When I bought my last Humber, she had been set up for all out speed ie with the engine set high up. the downside of this was cavitation in turns, and poor response to trim.
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Old 19 September 2006, 04:21   #8
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The cavitation plate sits about 1/2-1" below the keel and is sat on the transom as low as it will go.
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Old 19 September 2006, 04:57   #9
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Hey Jizm, Are Smurf and Arf still playing? and what is Sprocket up to now?
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Old 19 September 2006, 05:14   #10
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Jizm, I have a set kicking around my garage somewhere if you want to try a set first. Can't remember the name but think they are are Doel Fin.

Regards

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Old 19 September 2006, 06:42   #11
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cheers for the offer pete, just want to make sure I need them before I go drilling holes in my outboard!

Kitten, yes the boys are still around, Arf is working in Bristol at the mo and Smurf is over Fawley way with his new woman! Me and smurf went to the boatshow together just yesterday. Sprocket is up in London now and is the president of BALLS London.
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Old 19 September 2006, 07:02   #12
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Hi there, are you over propped??? This could be causing the cavitation. I once had a 4.8 rib which had a prop with a very course pitch and I reduced it down by 1 size and it worked perfectly.

One word of warning, if you are marginal on spare rpm, this is not the right route to go down, otherwise you risk having a blowup!!

regards richard
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Old 19 September 2006, 07:09   #13
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I get 5200rpm on my my current prop (11-1/8" x 13"P), I am under the impression that this is ok due to the manufacturers rec WOT of 4500 to 5500rpm, I am going to try a different prop when it arrives to see what difference it makes.
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Old 19 September 2006, 08:01   #14
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Call me paranoid but...

I'm not sold on sticking big things on a lower unit-whatever the manuf. say they are going to cause drag and increase fuel consumption at high RPM-it's like towing a paravane.
Basic physics says they can't do all they were claimed to do as well.
I had a set on a boat without PTT and it was all over the place with them on and trimmed out on the pin so be wary 1st time out with them.

Be aware that the lift/drag generated will change the stresses on your transom too.


Of course, you might love them!
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Old 19 September 2006, 09:06   #15
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there have been threads about them before and how they can make the boat turn violently when negotiating big waves or something. Worth looking into...
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Old 20 September 2006, 03:58   #16
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I used these on a hard boat and found that they made it handle interestingly to say the least.

Running with following waves in particular the boat would carve off unpredictably to one side when going down the wave. This would be so severe sometimes that it would cause the boat to pitch right up on one side. Without the assistance of tubes to stabilise things this effect could be fairly dramatic and eventually I took them off.
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Old 20 September 2006, 04:51   #17
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Quote:
Originally Posted by Jus
I used these on a hard boat and found that they made it handle interestingly to say the least.

Running with following waves in particular the boat would carve off unpredictably to one side when going down the wave. This would be so severe sometimes that it would cause the boat to pitch right up on one side. Without the assistance of tubes to stabilise things this effect could be fairly dramatic and eventually I took them off.

Yep, that's exactly what mine did. Very scary.
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Old 20 September 2006, 05:00   #18
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I binned a set after reading the posts last time it came up


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