TURNFIN Info (hydro).

[detox]

I found this comment in another forum and was wondering what everybody else thinks. Does this TURNFIN trick actually work and will it help our hydros turn better?

Mike,
In the hydro world, best way to get a handle on hull attitude with turn fin placement changes is PICK BOAT UP by the turn fin.

Now while cornering hull is pivoting / hanging by the fin.

So a fin too far forward has hulls tail heavier that the front and hull will YAW hard having transom swinging around faster than the bow.

Fin too far back places bow heavier than tail and hull will seam to push like a race car does with a straight axle not wanting to set up and get around the corner.

When placement is correct tail should follow the bow as if hull is swinging on a string while balanced right in the middle.

** Tuck angle having fins lower edge tilted towards hull places the water pressure of the sliding fin to climb the angle and this pressure tends to pull the hull downward at the same time.

[Boaterguy]

I think it could, think if you were to balance your boat sideways on the centroid (just got out of math homework) of the turn fin, how would it balance? I don't know if bending the turn fin will work because the fin doesn't slide at a high enough speed to create down lift.

[detox]

A person that is insane, does not know he is insane.

[Boaterguy]

changing that right now, but back to topic.

[Fluid]

Turn fin/CG placement has been a successful tuning aid for many years. You may notice on some hydros that the fin or the bracket has numerous holes - these allow changing the fin's position fore and aft to balance the handling. Having the CF ahead of the fin makes the boat very difficult to turn, it is far better to have the CG aft of the fin's centerline. Some boats will turn best with the CG even with the fin's centerline, it really depends on the hull design and the size/position of the rudder.

You had better believe that an angled fin will suck the boat down onto the water! Too much angle and the fin can cause the whole boat to dive under water - a club member had this problem several years ago before he understood that too much of a good thing is not so good. Today a better solution may be to use a 'hooked' fin, with the main portion of the blade straight up and down.




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[detox]

Yea it seems you would want the stern to slide around just a tad in the turns for best cornering.