A hydro turn fin question.....

[drobie]

Why do the nitro guys use turn fins with a curved leading edge and yet most of the ones I've seen FE use have straight leading edges.

H&M specs a curved leading edge for the hull I just got, so I assume that other Europeans do as well.

In addition, most mono turn fins I've seen also have curved leading edges.

What's the scoop?

 

[Propjockey]

You see Doug, our (nitro) turn fins start out with a straight leading edge -- but at the speeds that nitro burners go, the drag causes the aluminum to be worn down at the molecular level. But don't worry--as electric's speeds increase, you'll get rounded fins too! ;D

(Gee, did I open a can of worms? ;D ;D )

Seriously though, I've seen 'em both ways. I think it's a product of personal preference and the hardware available for the different hulls.

 

[Spuds]

Interesting question. Looking at my hydro’s I have a mix of curved and flat. My first thought is that this probably has more to do with where I purchased the parts and their personal preference. The only thing that I can think of is the flat one has more surface area in the water to turn against, so it might be more responsive and turn tighter (just a guess).

 

[forresterace]

Doug

I think it is a personal (or maybe even regional) preference or it depends upon which "expert" you talk to.

The only thing that I know for sure is that I have read that there are those that claim that a curved leading edge turn fin creates lift and the lift increases as the fin rides higher out of the water. Theoretically, this would promote the lifting of the inside sponson and of course we generally angle the turn fin to keep this sponson on the water.

Obviously, "you pays your money and you takes your choice" ;D

 

[Hammerhead]

I usually bend my fins twice with the big nitros. I think having the bend does a lot to reduce lift. I bend 10 degrees for each bend. For my .12 it is bent once at 20degrees. If you have a vertical leading edge wouldn't that be bluntly anti-aerodynamic. I have also noticed that you can sharpen turnfins to where you could shave with them, and I haven't seen any notible advantage over having them just rounded. In the JMPBA, you cant sharpen your fins or rudders where the will cut your skin. Safety thing, I guess. I doubt if it would matter if your got hit with a turn fin flying at full speed whether it was sharpened or not.

I noticed that the turnfin on my ProBoat Bud is almost verticle.

Hammer

 

[Strikedeep]

What would be the best angle to mount the fin at from vertical? Hull is a H&M Bud hydro.

 

[Hammerhead]

I left my degree measure at work, but just looking at the proboat bud, it looks like it is around 10 degrees.

Have no experience running it, at the moment, it is a decoration, so I don't know if that is an optimum angle, but I have read a lot about the proboat bud, and never heard anyone complain about the turn fin.

Good question for Eric Perez!

Hammer