Let's talk about turning fins

[chuckhomuth]

What kind of innovative ideas are it there about turning fins?
What kind of metal should they be made out of?
How far below should it be?
Straight down our tilted back?
Thanks

[Team B&H]

1. No new ideas, everything has been tried before in some fashion or another.

2. Something with a high modulus of elasticity. Does not necessarily have to be metallic.

3. Testing. Depends on boat and driving style. Generally easy to determine if it is not adequate in depth or area rather than if it is too big.

4. Testing. Ever think that straight down or swept back has more to do with location than shape?

[Tunnelman801]

Sam, Do you set your turn fin Angle [ camber] by the bottom of the boat or the bottom of the sponsons?William Anderson

[Team B&H]

An interesting question. The best answer is use whatever reference you desire but then be consistent. I start initially with the boat upside down by placing a straight edge across the bottom of both sponsons and then measure off vertical from that. You may have to tweak that a bit if your hull doesn't have equal length sponsons but the key is to measure off a line you can duplicate if you want more or less angle after testing. Camber is more a factor of boat design (cockpit offset) and driver positioning rather than an absolute number.

I also have to agree with Black Sheep about getting the fin blade straight with the boat. I use a laser for this, clamping a simple hardware-store laser level to the fin bracket and measuring out to the light from the air trap at the sponson and again at the transom. I try to get this within 1/8 inch over this span. Sometimes this can be a royal pain and take far longer than you anticipate to do without any silicone on the fin bracket, only to have the numbers change when you glue it on. If you're really sophisticated, you may want to go a little one way or the other if you know what you are looking for, but generally go for straight ahead.

,

[Bob Rusnak]

I have had fins made from 1/8 thick 6061 T6 Aluminum. Ran them under a 700 Pro Hydro and never broke or bent one. I still have about 20 different shapes and sizes left if any one is looking for a fin. I tried all kind of shapes but location and debt is the important factor.

[Matt Dagostino]

Sam made my stepbrother Greg Kneeland a Rockwell hardened steel fin in the 1980's we still have today! Greg turned his 30H B &H Hydro CSH so hard it kept bending fins. We find the 'Bannana Shape" fin slightly swept back works best for our 125 pound 20ssh driver nowadays.

Seems the lighter the driver the more sensitive the fin shape and location and height!

[Black Sheep]

I think we would all agree, each boat and each driver perform uniquely based on total setup. One driver might ask for a setup change that another driver may not like in the same boat.
Skid fins are obviously no different. I have been very fortunate to work with some REALLY smart people in boat racing, and the SINGLE MOST IMPORTANT THING is to be sure it is parallel to the boat!!! I don't care WHO built the boat, by the time you mount your fin bracket on the sponson transom, go rip a few heats off, I'd be willing to bet, it is no less than a 1/4" or more out of parallel over a 6’ span.

Now that the fin is strait, two more basic variables to keep track of are the fin angle (Or camber) and the dimension of the TRAILING edge of your fin.
I have made some wedges that go between the fin and the bracket in 3 and 5 degree angles. Depending on your mounting arrangement, you may need to be sure everything is parallel again as you now that you added a compound angle to the situation when using a wedge.
Now for measuring the location, find a consistent location to measure from. I prefer to measure from the prop nut with the engine strait to the trailing edge of the fin. I use that since that is the point of thrust as well the rudder function.

NOW GO TESTING!!!

…So much for a quick posting…
skidfin.jpg

[chuckhomuth]

This is great information.
Thank you
Oh by the way the cut suit is very nice.