Turn Fin

[Heartbeat]

I am working on my 21 rigger.

Can somebody tell me how much hook should be in the bottom?

how should the fin be placed in relation to the COG?

I am trying to make it turn better, it wants to roll instead of hook.

Thankyou

Mike

 

[shoboat]

Mike,

I need a little more information,like what boat and what motor are you running.

I should remember,but I can't recall your setup. There are a lot of different

things to consider when you are working on your turnfin setup.

Thanks,

Mark Sholund

 

[Heartbeat]

Its a older Mongoose, Novarossi power. COG is about 2.25" back from rear of front sponson.

Mark its the same one I am trying to get the prop right on, as I started going faster this other problem crept up.

Thanks Mike

 

[Preston_Hall]

I like a lot of roll in the fin. Almost til it is horizontal. Well, don't get too crazy. Start the roll about 1" below the sponson. The trailing tip should be around 1" in front of the CG. If the boat hooks, the fin is too far forward. If the boat turns lazily the fin is too far back.

 

[John Finch]

If it's an old mongoose look at the left rear sponson. It should have a non trip edge on the outside left edge where it hits the water. If it does not, that's why your boat is tripping and rolling.

 

[Heartbeat]

Thanks for the help

From what I can figure my turn fin was all wrong, built a new one, we will see tommorrow.

John Whats a non trip edge? The left rear has more angle off the leading edge, is that what you mean?

Thanks Mike

 

[John Finch]

Mike,

The non trip is the outside edge of the sponson. You see, all boats slide to the outside when making a turn. The front sponsons especially need that angle to keep the boat from rolling over. If the outside of the sponson is 90 degrees to the water the boat trips and rolls over when making a corner at high speed. That's why all front sponsons have that angle on the outside half of the sponson. The particular boat you have may be one of those that did not have that angle on the rear sponson. While the rear sponson does not usually cause the boat to roll over, this particular model did. A slice in the left rear sponson at the bottom outside edge was later added in production to prevent the roll over. Just some history on your boat and something you can look at.

 

[Heartbeat]

Thanks John

I do have that slice.

Mike