I would like to know if someone can help me with the following subject:
How do we determine the fin placement on the board? Is there any rule i should follow? What measures should i use to place the fins? Are the side fins pointed exactly at the nose or somewhere else and if so where exactly? How does the fin positioning change in relation to the board’s size? And what about twin, single fins and longboards sidebiters?
I will be grateful for any help you can give me, i searched on the internet but all i get is a lot of contradictory information.
Take a look through the archives here by searching those topics - I think you’ll get a lot of the answers you’re looking for in them. You may still see some contradictory information but then post back on those particulars concerns. There are a few guys on here, who really are fin experts in that area.
Here is a link that really may help get you started in your search for answers - Greg’s summary in it is excellent:
I have been searching the archives and i have found some info but i still have a few questions:
When every one refers to toe in measurements, those measurements are taken in relation to what? example given: 1/4" on a 4.5 inch base
Another question i have and that i couldn’t find an answer to in the archives is how does one determine at what distance should the side fins be from the stinger and how do changes in that distance affect performance?
By the way, here goes a picture of my second board. Its a 6’7’‘x19’’ 1/2x2’’ shortboard.
I didn’t mark the fins on this one. I took it to a glass shop and asked them to do it for me.
On my first board i tried to place them and glass it my self and the results are catastrophic. I’m not so bad at shaping but glassing is defenitely not for me. However i would like to be able to decided fin placement by my self.
When every one refers to toe in measurements, those measurements are taken in relation to what? example given: 1/4" on a 4.5 inch base
Let’s say you decide to put a rail fin 10.5 inches from the tail. Measure 10.5 inches up the stringer. Using a T, measure 1.25 inches from the rail at that distance up the stringer. Put a little dot there. Measure the distance from the stringer.
Take a 4.5 inch long straight edge (or fin), put the trailing edge on the dot. Set the front edge of the fin so that it is 1/4" closer to the stringer. Put another dot there. Those two dots mark the fin line, with the rear dot being the fin trailing edge.
So, 0.25 inches on a 4.5 inch base means the toe-in angle is the arc-tangent of (0.25/4.5) or about 3.17 degrees.
In checking quite a few production thruster shortboards, this angle is quite common. Almost universal. That I find somewhat odd as side fins come in a range of assymmetric cambers which change their effective toe-in angle. There are a few fin systems that let you tweak out the toe-in, these should allow you to dial in any board (if you are the type of tweaker that like to dial in a board).