Ok, so to start off I realize there are a number of questions in this post so I am going to try and break it down as much as possible. I have been shaping my first board for a couple of days now and I am closing in on the fin placement. I live in FL and aside from the incoming swell this weekend my local spot gets waste to chest high mushy surf with occational clean same size days. I began shaping a fish to work in these conditions. I have shaped a 5’8" performance fish, 20.5" x 2.75" at center with stepped deck with a small swallow tail. The I have seen a number of contradictions about fin placement for quads and wanted to see what would be best for this size/shape board. So lets begin:
Distance from the rail to the trailing edge of the fins: I have read thoughout swaylocks and other sites that there is somewhat if a standard for fish quads of about 1-1/4" from the trailing edge of all the fins to rail. This being one of the few dimensions that I found somewhat consistantly I was excited knowing I have somewhere to start from. Then I came across this site which had the trailing fins much closer to the stringer then I had seen before. This site also provides a number of dims that seemed useful but none specific to a perf fish.
Distance between the rear and front set of fins: I have seen a number of posts saying that this measurement is impoartant because if the distance between the two is too great then the 2 sets of fins will act just as that, two entire sets of fins. If you keep these fins closer together you create a channel between the 2 fins on each side and thus they work together. I came across a few posts, one below for the CI biscuit, saying this measurement should be 3/4" from the rear of the leading fins to the front of the trailing. I didn’t know if this would translate to the performance fish I was shaping because I have been looking at other boards (the super fish inparticular) and noticed this distance was much greater than 3/4". It alsmost looks like 2" - 3" which looks to fall in line with what the MekeeSurf site references. I was thinking the trailing edge of the front fins would be around 10-3/4" based on the length of the board but this still doesn’t answer the question of the distance between the 2 sets.
Cant of the front fins and cant of the rear fins: This measurement I have heard the most contradictions. I have heard that the front set should be canted in 1/4" and the rear should be 1/16" or straight (most have argued that straight is incorrect and a little cant is needed). I have heard that both sets of fins should be parallel, canting both sets of fins 1/4" in. I have also heard (this one seems to make the most sense to me because it takes into account the width and length of the board) that you should take the width of the board at the back of the front set of fins. Let’s use 14" as an example. From here you would then find on the nose where it shares the same width. So you would move down the nose about a foot to where the board is 14" and mark this. From here you are to draw a line from the left rail at 14" to the mark on the right rail at 14" and do the same thing for the other side. You would then have a “X” across the board and you would make the front fins the same cant as the parallel line. See diagram below that I mocked up. You would do the exact same thing with the trailing fins thus making the trailing fins more parallel to the stinger but not quite straight.
I guess the real delema is finding a way to get ALL of these
measurements correct so they all work together as a quad. Nature of
the beast I guess. Below are also some picture of the board. I am not
quite done with the tail, the shape is good but I plan on taking more
weight off the tail because it is to think right now and I need to
plane down the deck so the transition to the swallow is more graceful,
but the rail shape is done. If I could please get some suggestions or
information from past experiences that would be great. I appreciate it.
I also forgot to mention that I am using the FCS Fusion fin system with FCS SF4 fins. The fin boxes are 9 degree for the front and 5 degree for the rear.
I am just finishing up a 5’8 quad fish and had to do exactly what you are doing now - wading through so much information. A thread that really helped me was How I Probox. You should check it out. It gives detailed instructions on a quad placement that is recommended by Probox-Larry. After reading through that and many other quad fin placement threads I went with:
Trailing fins: 6" up from tail tips and 1 1/2" in from the rails, cant 4 degrees.
Leading Fins: 11" from tail tips (Next time I would go about 11 1/4" - 11 1/2") and 1 1/2" in from the rails. Cant 6 degrees.
As for toe-in I went with 1/4" on all, which corresponds to the front of the leading (front) fin box being about 2 3/8" in from my rails. The trailing box toe in was based off the leading box (see How I Probox Thread).
Also, Probox-Larry reccomends same toe-in on all the boxes and about 3/4" - 1" distance between trailing end of leading fin box and leading end of the trailing fin box, which makes perfect sense. Quads are suppose to work together as a cluster. With my install I ended up with just under 3/4".
Also if your going with a removable fin system, go probox. It is SOOOO easy to install! My first time using it and no problems. Sweet product Larry!
5 and 9 deg cants on that board will leave you with a lack of drive, something that even trying different fin models might not even be able to fix. You would be much better off going with 6 and 4 deg cants imho.
Thanks for the ProBox recommendation fws, I agree completely! With ProBox in there, if the cants I recommended dont work out, you can easily change it to see what happens, and you can use your existing fcs fins too.
Thanks for the information! The more I read about the ProBox system the more I am leaning towards it. Knowing I can use my FCS fins with it is huge because I didn’t really want to get away from FCS just because of their availability in remote locations. I can always find a shop with FCS fins. I had originally wanted a 5 fin setup so that it could be surfed as a thruster, but after seeing a friend of mines’ board with the FCS Fusion plugs in a 5 fin setup, I noticed that when the shaper had routed out the center fin box the router caught the stringer and there was a 1/2" splinter that was taken off that was filled in with the resin. After seeing a professional shaper catching the stringer (and after dealing with it while shaping the swallow on the tail) I decided I didn’t want to mess with the 5th box. Have either of you installed a center fin with the ProBox system? If so is it more or less difficult then FCS fusions?
I recently did this install; it was only my second probox install but it went pretty well without any grotesque errors.
The best thing about probox in my opinion (even beating out the cant, although that is also a very valuable feature) is the huge amount of forward and back movement potential in the fins; so you can separate the fin cluster or tighten them up or slide them forward or drop them back etc and so on, making it a much more failsafe process for inexperienced shapers like you and I. Way less chance of ending up with something that doesn’t respond well or is lacking drive or not enough hold or whatever. Fusions also have a bit of movement potential but it’s like 3/16" or something compared to probox’s half inch.
IN answer to your question: when routing the center box, it’s important to take it slow and be careful because the stringer does make it harder; but as long as you are careful and make sure that you’re routering into the stringer from the right side (so that the bit’s cutting edge is spinning INTO the hole that you’re routering, not outwards toward the board when it’s cutting the stringer - make sense?) then you should be fine. It’s important to let the router do the work and not try to hurry the process by forcing it along. I used a crappy little Black and Decker laminate trimmer and it worked fine although it was a real pain to adjust accurately.
I’ve never installed FCS fusions so I have no input there.
That makes perfect sense and explains why the stringer on my buddies board was split from the center of the stringer to the right and up, as if he was cutting from the left side all the way through and it caught 1/2 way.
