Turn Fin Location

[Aaron Lavigne]

I have read through countless threads on hydro setup and turn fin location. Many have said put the trailing edge of the turn fin right at the CG, other up to 1" ahead of it. Where should the trailing edge be in relation to CG? I know this may not be a simple question because it just depends on many variables.

If a rigger is blowing over would moving the turn fin forward of the CG help? Seems like it would have more length in the rear of the boat to help balance it, instead of having up force in the middle right on the CG.

Any hydro or rigger discussion is welcome

 

[Javier Picon]

Have you tried dropping the strut? What AOA do you have in the sponson? Have you tried laying them down?

 

[Aaron Lavigne]

I cannot easily adjust the sponsons but I have measured and I think they are at 3.5 degrees. The strut is pushed all the way down to the setup table and there is a little bit of negative in it.

The bend in the turn fin is parallel with the water line. Maybe a tad upwards towards the front side. I am going to remount it a little more downwards, maybe that will help, but at the same time I was thinking about the actual location of the turn fine.

My question is not really boat specific just wondering where it should actually be mounted because there seems to be a wide range. What's the reason for the wide range?

 

[moparbarn]

Drop the strut some more, it will lift the back, lower fr. sponson aoa & settle the boat down - all at once! Dick tyndall/vacraftsman turn fins wants the cg on the center(sweet spot) of the fin. His come marked as to where it should be in relation to the cg. Front of turn fin up will lift the right sponson & loosen the boat up. Angle the front down a little. You might be able to get rid of the neg. in the strut, also.

 

[Aaron Lavigne]

I'm going to fool around with my rigger and see how pushing it further to the front of the sponson changes how it runs.

 

[El Zorro]

A good starting spot for the turn fin ( rigger, Sport hydro, etc. ) is usually about 3/4" just forward of the rear most part of the turn fin. The turn fin is your pivot point when the boat is turning in the corner. Moving the fin forward puts more weight BEHIND the pivot point and will make the boat more sensitive to rudder inputs and may even make the boat spin out. Moving the fin to the rear of the boat puts more weight on the FRONT of the boat, therefore making the boat harder to turn ( needing more rudder input ) or as the race car guys say, PUSHING. The boat will let you know what it likes when you start moving the fin forward or rearward. You also have to deal with tilting the fin forward or back to keep the right sponson on the water in the turns. If the right sponson rides off of the water in the corners, tilt the bottom of the fin slightly to the rear of the boat. If the boat has a hard pull to the right in the straightaway, tilt the bottom of the fin forward slightly. Again, the boat will let you know if it likes or dislikes your adjustments.

Hope this helps you out with your boat.

Dick Tyndall

 

[Aaron Lavigne]

Thanks for the info, do you mean the rear most part of the turn fin needs to be 3/4" behind the Center of Balance/Gravity?

Do you think turn fin location, not angle, has any impact on how it rides like wet or dry? If all other things being equal.

 

[El Zorro]

The answer to your first question is yes. But as I mentioned earlier, it is only a starting point. I have a Gas Rigger and this is where the turn fin is positioned on my boat. I could probably fine tune it some more, but when I can drive it around the corners in Lane 2 at 74 MPH it is more than I can handle. As for your second question, the ANGLE of the turn fin has more to do with how the boat rides ( wet or dry ) than the forward or rearward position of the fin.

One other thing to keep in mind is to cut down on your rudder throw and make the rudder inputs less sensitive...........slow things down. Any hydro going at these speeds don't need much rudder to go around a corner.

Dick Tyndall

 

[Aaron Lavigne]

Awesome thanks a lot bro