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Author Topic: Fin position on yacht  (Read 1400 times)

Popeye

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Fin position on yacht
« on: March 19, 2015, 06:11:49 PM »

I'm preparing to start my next project - a 37"loa Suffolk bawley- and will fit a removable delta shaped fin (see photos). I'm uncertain whether its' horizontal plane should be positioned parallel to the plan waterline (sketch A) or to the keel (sketch B).


I favour position A in preference to position B because the latter will tend to lift the bow when under way. plus the fact that it just don't look right. 


What's the concensus view???
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Netleyned

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Re: Fin position on yacht
« Reply #1 on: March 19, 2015, 06:46:26 PM »

Why a delta fin?
A vertical fin with a streamlined bulb would surely be better on a traditional craft.
The delta plate is going to decide the dynamics of the sailing qualities.

Ned
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Popeye

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Re: Fin position on yacht
« Reply #2 on: March 19, 2015, 06:55:28 PM »

Why a delta fin?
A vertical fin with a streamlined bulb would surely be better on a traditional craft.
The delta plate is going to decide the dynamics of the sailing qualities.

Ned


I'll use one of my spare tried and trusted delta fins molded by the late Tony Williams coz I've used all my conventional bulb fins which he also produced.
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boneash

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Re: Fin position on yacht
« Reply #3 on: March 19, 2015, 08:05:15 PM »

On 12" to the foot yachts the delta is fitted with a slight toe down to the water line.
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Popeye

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Re: Fin position on yacht
« Reply #4 on: March 19, 2015, 09:30:20 PM »

On 12" to the foot yachts the delta is fitted with a slight toe down to the water line.


Just the kind of response I was hoping for. Many thanks :-))


PS. The bawley is !:12 scale.
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Brooks22

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Re: Fin position on yacht
« Reply #5 on: April 17, 2015, 05:20:39 AM »

With B, the more the boat heels, the more the wing will drive the bow off the wind. This may be helpful if you find that your boat develops excessive weather helm when she heels.

With A, heel should not affect bow thrust as much, either into or away from the wind.

If real boats use an "anti B" (nose of the wing pointed down a bit when the craft is level), it might be to counter the drive I mentioned above. Or  to at least ensure the off-wind drive does not develop when the boat pitches.
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