Thruster fins

Hey everyone,

I just have a question about fin toe angle. Is it the greater the angle(such as 1/4") or lesser (1/8) that delivers more power and drive in the experience? I already have the meausurements written down for the fin layout, I’m just having trouble understanding toe angle.

 

Thanks!!!

I generally follow a few principles when setting fin toe-in.

Increased toe-in results in increased responsiveness, increased thrust, and increased drag. If these principles are true, and theory and experimental evidence suggest they are, then it makes sense to toe thruster fins in more on boards designed for smaller or weaker surf, and less for boards designed for bigger or faster surf.

Thanks a lot! Im in the middle of making a board for my brother and this really helper out a lot. He generally only surs during the summer so this infor was greatly needed.

 

 

Thanks a lot! Im in the middle of making a board for my brother and this really helper out a lot. He generally only surfs during the summer so this infor was greatly needed.

 

 

When I do fin placement I tow in by distance off the nose tip, because 1/8" tow in on a 7’2x 13 3/4 tail will bedifferent than an 1/8" on a 5’5 x 15" tail. once I get it dialed on one side, I will see how much it is towed in. Lets say it ends up being 3/16"…then I will do 3/16 on the other side to make it symetrical and double check the distance it is towed off the nose. just my take on things…hope this helps

Say the board is a 6’4"x14 tail, what toe in would you use for a small wave thruster? Right now I have 1/4" on the mind.

Thats not what I meant…I was just saying that there is a difference between 1/4" on a longerboard with a narrow tail and a short wide one. Also will change depending on where rail fins are placed(off the rail and up from the tail). That is why I said that I measure off the nose. so the line from the trailing edge of the rail fins to the front edge extended all the way out to the end of the nose is how I measure. Do a test…find a long straight edge. plug in your dots…line the straight edge up…say it is 4 inches off the nose tip and you want it 2 inches off, then move the front dot in more. Once it is good then figure out the difference between the front and back fin dots from the stringer. Say for example it is 1/8" difference that gets you 2" off the nose for tow in on this board, then plug in 1/8" difference on the other side…test it with your long straight edge to make sure it is 2" off the nose, and you’re good.

1/32" diference between front and back dots could be a full inch or more difference off the nose, so it makes a HUGE difference.

I have limited experience and probably learned this here, so search the past forum questions and answers and you might come up with better advice…works for me so far. hope this makes sense…good luck, adam

Yes, astevens is trying to teach you how to figure the toe-in for different shapes and different lengths.

 

that diagram helps…I don’t know how to make that stuff and put it on here. I don’t tow fins in past the stringer because I hear it causes lots of drag, but rather measure by inches off the same side of the stringer(ie 2" off stringer is towed in more than 4" off)

Yeah I'm with you I don't think I've ever gone more than 1" past the nose. I'll Update the diagram tonight...it was late and the Corona made me do it! Mostly I go to the stringer for side bites on 2+1 setups. I'm more conservative on fishes and clusters...maybe 1" Same Side or close to neutral.

 

Here’s version 2:

 

Having that image is great for me to actually be able to visualize it. Tomorrow should be the day when the fin boxes go in thanks to this information.  Can’t thank you guys enough for helping me out!

I make boards we use to surf a river wave with. Please don’t hate. My go to size is a 5’0, aggressive little short board thruster fin set up. I’ve messed with different fin toe measurements, usually just do the angling toward the nose thing which typically puts me at about a half inch toe in at that board length. This does seem to make the board slow and loose. It’s kind of a tight wave the board needs to be fast and turn quick. 1/8"? 1/4?

Yes use the stringer as your final point of reference.  What ever your toe is;  make sure it is OFF the stringer.  Put the toe dead on the stringer or across the stringer and you will have a dog.  Generally it is best.to stay 1/8" off the stringer minimal.

The off the stringer thing is really making it too difficult. You really think the glassed is even capable of placing the fin plugs to tolerances of 1/32 of an inch? I/8" goes straight and fast. More than 1/4" drags.

If you really want to find out. Glass on some fins, try them out, then sand them off and try something different.

Or you could just buy and install some of those fancy swivel fins like Verbal uses and cross them up.  I think that’s a good alternative for people who can’t take solid advice.

Real shapers mark the fin placement.  It’s not for the “glassed” to make that decision.