Twin turn fin help.

[Troy Hammons]

I am using the same fin on a single and it works well. The extra weight of the twin has it mushing around the corners. I have about 2 3/4" of fin in the water and about 4" front to back. It never lets go in the corner, just not carving. I was thinking of making one wider front to back? Anyone have some hints? Thanks.

 

[David Murany]

Check the CG and put the trailing edge of the turn fin about a half an inch in front of it at the water line. That should get it close then you can fine-tune from there.

 

[Troy Hammons]

I'm at 2.5" in front of the CG now. We will give that a try next time out. In the past on singles the boat becomes less reactive with the fin back. so we will see. Thanks for your input.

 

[dave roach]

Troy
Looks to me that the right sponson is lifting in the corners.I think you need more curl at the bottom of the turn fin I stop the video in the corners and that is what i can see.How deep is your turn fin.Look at the shot at 2min and you will see it The sponson is coming out of the water

 

[Terry Keeley]

Is it braced to the tub? Or is the sponson and rear boom taking all the force?

Can you post a coupla photos?

 

[Troy Hammons]

Dave, I thought the same thing ,but the video quality isn't helping much. Fin is in the water almost 3"

Terry, It's not braced to the tub. I make my fins from .090 7075. They get fairly thin towards the bottom. May be some flexing going on.

 

[Brad Christy]

Troy,

Check with Brian Blaser about the turn fin he puts on his GSHs. I believe its 1/8" stainless, and almost the size of the state of Ohio. Those boats turn like their on rails.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[brad nichols]

Have to agree that on a twin gas there is a huge load on that thin turn fin!! 1/8 stainless would be the way to go.

Brad

 

[Lay26]

boat looks good Troy

 

[Terry Keeley]

Terry, It's not braced to the tub. I make my fins from .090 7075. They get fairly thin towards the bottom. May be some flexing going on.

Assuming the curl is parallel to the water line or slightly kicked up at the back it might be flexing, or just too small or a bit of both.

It would probably be better with a brace to the tub (1/8" or 3/16" ss rod) but it's likely too narrow as well.

My new single 90 fin is 4.5" wide at the water line on an 8 lb boat. Bet your's weighs twice that?

I'd think 0.090" 7075 should be good enough with a brace...

 

[Troy Hammons]

Thanks for the input everyone. It' weighs 20 lb 4 oz. I will make some bigger fins to try and see how it goes.

 

[Larrykent]

I make my own fins on my two RR Twins.
it looks from the pic that the front is already angled to pick up the sponson.
I set mine level with sponson and usually down in the front a hair to help pull down while turning. Parasitic drag causes the boat to twist a little anyway, so a (hair) compensates.
Just my thoughts .
Good luck
Larry

 

[Troy Hammons]

Larry, I just threw it on for a picture. I set mine by sighting the bottom edge of he fin parallel to the bottom of the tub then kick the back up just slightly. the tub is flat all the way to the transom so its an easy way to set the fin.

 

[Larrykent]

I understand
But
The tub does not ride in the water. Good reference though.
lk