Fin placement?

[spark6]

Hey all,

I am in the midst of finishing a board I have been shaping (my very first!) and am now trying to work out fin placement... I'm going to use a three fin thruster set up - i've got the fins - and the board is a 7'6" hybridish thing .

So I have all that ironed out, now the question is, where to put the things? First and foremost, how far in from the tail should the center fin go? I have been reading a website that suggests 3" in, but is that from the base of the fin, or the tip? If its from the base, it doesn't quite look right, like its too close to the tail... i dunno...

The second question then remains where to put the side fins? how far forward of the trailing edge of the center fin should they go?

Third, using the S.W.A.G. principle (Systematic Wild Ass Guess) it looks like the trailing edges of the side fins should be about an inch from the rails... then from what I have read they should be set with about 1/4" toe in... does all this sound about right?

Fourth, what about rake? My reading points me toward 4-8 degrees, so i was gonna shoot for 6 (lol)... will this work?

Fifth, (and last, i promise) can i use these same principles on a 6' 1" retro fish and a 6' 8" funboard? The fish is gonna be a twin set up, so i guess that is different, but i assume the 6' 8" has gotta be roughly similar to the 7' 6" set up right?


All right, so i guess one last thing (I know, I know, i promised...) what about the fish? How far in should the twin keels go? and are they ok with about an inch in from the rails and 1/4" toe in? Can the rake on them be the same as the rake on the 6' 8" and 7' 6"

Thanks guys, if this has been asked before, I apologize, i tried the search function, but didn't find anything that really pertained. But i am really bad at looking for things...

[kitesurfer]

Hey all,

I am in the midst of finishing a board I have been shaping (my very first!) and am now trying to work out fin placement... I'm going to use a three fin thruster set up - i've got the fins - and the board is a 7'6" hybridish thing .

So I have all that ironed out, now the question is, where to put the things? First and foremost, how far in from the tail should the center fin go? I have been reading a website that suggests 3" in, but is that from the base of the fin, or the tip? If its from the base, it doesn't quite look right, like its too close to the tail... i dunno...

The second question then remains where to put the side fins? how far forward of the trailing edge of the center fin should they go?

Third, using the S.W.A.G. principle (Systematic Wild Ass Guess) it looks like the trailing edges of the side fins should be about an inch from the rails... then from what I have read they should be set with about 1/4" toe in... does all this sound about right?

Fourth, what about rake? My reading points me toward 4-8 degrees, so i was gonna shoot for 6 (lol)... will this work?

Fifth, (and last, i promise) can i use these same principles on a 6' 1" retro fish and a 6' 8" funboard? The fish is gonna be a twin set up, so i guess that is different, but i assume the 6' 8" has gotta be roughly similar to the 7' 6" set up right?


All right, so i guess one last thing (I know, I know, i promised...) what about the fish? How far in should the twin keels go? and are they ok with about an inch in from the rails and 1/4" toe in? Can the rake on them be the same as the rake on the 6' 8" and 7' 6"

Thanks guys, if this has been asked before, I apologize, i tried the search function, but didn't find anything that really pertained. But i am really bad at looking for things...

Right lets start with the 7ft 6 board. All fin measurements are given from the trailing edge of the base of the fins relative to the tail of the board!
Centre fin 3.5-4 inches up from the tail, 4 inches for a slightly looser board 3.5 for a bit more stiffness.
Assuming the board is either a minimal or big thruster style of board then the thrusters should be around 11 to 12 inches up from the tail and 1 1/8th to 1 1/4inches in from the rails.
Again the further away from the centre fin you put the thrusters the stiffer the board will be. Fine adjustments are up to your preference. Measure the thrusters position in from the rail NOT out from the centre line of the board in case your board isn't the same width both sides at this point.

And MOST importantly check double check and even triple check your measurements before making the holes. Trust me its very easy to get your measurments wrong!

1/4 inch toe in across the length of the fin base is about right. Or for a board of this length you can point the fins to the nose of the board. More toe in helps in turning but creates more drag.
Cant on a board of this style is less critical and your figure of 6 is ok.
More cant/rake gives more lift at the nose but if you already have alot of rocker then then keep the cant angles lower.

The fish will be different set-up. Ask me again when your ready to fit fins. And the funboard set-up will depend on what type of board the fun board is as the term funboard is used these days to describe all kinds of surf boards.

Hope this helps.

KS

[spark6]

Thank you KS! You are a lifesaver! lol. I just got back from a ski trip, so probably tomorrow i'll get back out to the surf shop... I am doing glass-ons for this set of boards, so hopefully, i'll have the fins stuck on the 7'6" by tomorrow night. (fingers crossed) What I am doing is spearheading the building for three surfboards at the same time with my two little brothers. The youngest really wanted to build a fish - I am now wishing that I had protested that choice a little more, but what's done is done. I'll def. come back for advice on the fish when we get to that point, maybe the end of the week... As for the "funboard" I'll get some measurements in the morning, right now I need to hit the sack and sleep off some of the soreness... oof!

Thanks again for your input!

[spark6]

Alright, well, as often seems to happen to me, life got in the way of grand plans. Hmmph. But now it looks like we are finally ready. So, i'm back with more questions...

1st; for a 6' 1" fish what should i be looking at for fin placement measurements? How many degrees of cant? How far in from the rails and from the tail should the trailing edges be? Will 1/4" of toe in work?

2nd; for a 6' 8" hybrid, what am i looking at measurement wise? Its going to have a thruster setup, and is 21" at the maximum beam and 9" at the tail. I assume that i cannot use the same set up that i used for the 7' 6" that i described in the first post, but i am thinking that it is going to be roughly similar?

Thanks all!

[kitesurfer]

1st; for a 6' 1" fish what should i be looking at for fin placement measurements? How many degrees of cant? How far in from the rails and from the tail should the trailing edges be? Will 1/4" of toe in work?

2nd; for a 6' 8" hybrid, what am i looking at measurement wise? Its going to have a thruster setup, and is 21" at the maximum beam and 9" at the tail. I assume that i cannot use the same set up that i used for the 7' 6" that i described in the first post, but i am thinking that it is going to be roughly similar?

Heres an outline of the first fish i ever made.



I use this as a basis for most my measurements. You might also want to go to a few surf shops if poss and look at some more modern fishes to see where exactly they're fins are as it is dependant on the size of the board to an extent.

Cant or toe-in are not necessary if you want a really loose retro fish as all they do is slow the board down. Put some in if you want a board that is a little easier to ride.

As for the hybrid i'm looking forward to seeing some piccies of it.

KS

[spark6]

How do I post pictures?

[kitesurfer]

When your in the reply section look just above the white box and there's a link that says "Upload and Image for this post"
Voila!



KS

[spark6]

Man, that was easier than I was making it... thanks KS.

The first pic is of the fish, the rest are the 6'8". Pic 2 is looking from the nose. Pic 3 top down, and pic 4 is looking down the rail...