I hate to bring up a topic that has been thoroughly discussed in the the forum already but I am a little confused about a few aspects (ok, utterly lost) of fin design. I dont have a engineering background and reynold numbers seem to confuse me- utterly, lame I know, been miss spending my college years studying literature and finance . . . Anyway back to the point- I have some left over high density foam that I want to make a set of skegs out of for a short board (similar but completely inferior to Bert’s “Mush destroyer”). From my reading I understand that a good place for the widest place of the foil should be 20-30% of the fore-aft lengthwise with a dual foil and a rounded leading edge. I am confused as to the:
base widths (when widths up to 3/4 inch mentioned is that applicable to short boards fins or just large long board fins?)
base to tip foil (constant/curved/based on fore-aft length?)
for side fins what percentage should be outboard vs inboard
would a narrow base arcing up to the wide point set off the board be benefitial for decreasing cavitation/ increasing performance?
any comments on cutoffs for shortboards? or hatchets?
Comments on the FCS H2 design? They mention a very large cant- why so much for this design?
should the heights/widths of the center fin be different from the side fins?
Please if there is anything you would like to throw in please do so!
Anytime you want to talk about how some part of a surfboard or a fin works you gotta bone up on the terminology or it’s damn near impossible to make any progress. Rather then try and sort through what you’re trying to get at and bounce a bunch of words around and not get very far. Check out the archives and see if you can pin down what it is that you really want to know. There a many discussions on fin performance there.
How you want kind of board you have and how you want it to perform will dictate how your fins need to be configured.
I’m sorry to say that broad answers are tough to give when it comes to fins.
Maybe if we take questions one at a time we’ll get somewhere.
For the record, if you’re going to make a set of fins with high density foam cores in them it would be best to make glass-on fins. The vertical cord of the foil at about 20% to 25% off the leading edge works quite well.
Halcyon, yeah I get confused rapidly in the fin threads, I have read through them and I suppose my largest question comes down to width and the transition along the verticle cord from base to tip(the base depth). I am been convinced by several of the threads that a wider fin is what I am looking for but are the 3/4 in + wide fins mentioned in several of the threads intended for shortboards and does the width remain relatively constant along the verticle cord?
Actually I did just finish board number 3, and this was my fisrt vac’d board. it is 6’2" based on Bert’s “Mush Desroyer” but my rounded wings are more severe. There are some severe flaws in the board but nothing I cannot live with until I make another =) such as the foil near the nose is just too thick, I wanted to make it a little thicker for extra float on the smaller waves that the board is intended for but it turned out to be too much. Also, it is a single to double with a vee out the tail, the vacumm didnt like them where they were so it put them where it thought they should go, but I think I have that problem worked out for next time. If I were to make the same board over again I would fix the aforementioned, go 2" shorter and relax the rocker. This board is intended for 1-3’ hawaii (south shore mainly) but will probably end up in SoCal for all around conditions for my brother or whomever. Only had it in the water once so far, small day (1-2) and the board was really loose, cannot wait to try it when it is a little larger. Oh, it also has a concave deck, I still have not formed an opion but I like it so far and as of right now plan to use it on the next board as well. - This is the board that I plan to put these fins on but am also mentally constructing the next board in my head for 4-8 foot surf (hawaiian), it will be another vac board (maybe a flat bottom this time =), also trying to pick out what elements I would like to stress in a all-around travel board, Any tips there?
Hey chipfish, it is a 6’2" x 19 1/4 (dead center) x 11 3/4 n x 14 t
I dont have the thicknesses.
Future fin system with a set of thecheapo fins.
The stain was an experiment based on a swaylocks post that refered to it as a “blog stain”–not quite the same but close enough, here it is colored spackle sealing the foam.
Oh, please dont use the logo on the bottom for reference, it is well off center.
I 6’ 155lb, the board is primarily intended for 1-3 (hawaiian) but it will probably end up in California as an all-around board.
