# Side fin cant...

I’ve never used a protractor to measure degrees of cant. On my own boards, I generally eyeball it. I have measured the distance between the tips and compared that to the distance between the trailing edge of the bases. Most have come in around 1 1/4" - 1 1/2" greater distance between the tips, including the ones I eyeballed. It takes some of the variable out when measuring by degrees with concaves and vees. I’d like to see what other people are coming up with using those measurements.

Whoa John, you’re off into the deep, dark secrets of design here.

Hi John,

You must have a good ‘eye’ and confidence in it. I use a chunk of 2x4 cut at 4 degrees. THEN I eye ball it. Sometimes I measure the distance from the tip of the fin to the tips of my fish to see if I’m close. Havne’t tried your method, though. Mike

Hey John,

With the measurements you give, and supposing the distance between the fin bases is as little as 8" and as much as 15", and the fin height is between 3" and 5" tall, I calculate cant angles per fin between 7 and 14 degrees. Here’s a diagram (not to scale):

if you are interested, The formula for the cant angle on each fin is: cant = arcsin {[(y-x)/2]/(fin height)}. (NOTE: EDITED from arctan function, but this only changes the numbers by about 0.4 degrees).

Now if these cant angles seem high, it’s because things like concave and vee are not being accounted for (and the ‘relative cant’ that can be measured due to them), just distance between bases and tips. This formula also assumes that the points of measurement on the bases and fins lie on the same plane.

JSS

I use a compass.

Simple and ez to use.

I have 4 degree blocks made for me, out of aluminum,but they serve as book ends mostly.Herb

Howzit Herb, I think you mean a protractor not a compass. I use a sliding bevel square with a protractor, that way I can set the bevel square at any angle I need. Aloha,Kokua

In the interest of maintaining civility, my original response has been deleted…

“I’d like to see what other people are coming up with using those measurements.”

Howzit John, I don’t think you needed to delete you reply post, what could be said that would be uncivil. Remember we ( including Herb) are some of the long timers here and have pretty much seen it all. You can PM me with your reply. Aloha,Kokua

Hey John,

I didn’t mean to not answer your question (double negative, I know). I was merely trying to translate your system of measurement into the one where cant is measured as angle away from the perpendicular to the bottom at that point. For boards with flat bottoms, the formula translates directly, not so for anything other than flat…

I was just trying to bridge the gap…

JSS

I steer clear of complicated fuzzy math formulas.

If you guys would just do it, you’d see how easy it is.

Skip the vee, skip the concaves, skip the math… just do it. And don’t forget to get back to me with those numbers. The numbers are key to the deep dark secret.

Howzit John, I agree,those in the know don’t need no stinkin fuzzy math formulars. Aloha,Kokua

Hi John,

Usually i draw a line with the cant i want to use on a piece of thin wood (the one i use for making templates) or on a piece of cardboard using one of this (sorry, i don’t know the name in english):

The longer base make it work over concaves and other different bottom contours.

Hope this helps.

Coque.

Hi Coque -

Thanks for that great demo. And what are the tip-to-tip and base-to-base measurements please?

THANKS!

PS - Measuring this way on Bonzers won’t work. They typically have more cant than what I’m talking about.

John, one of the good things using this “system” is that no matter how long are the fins, all you need to know is which cant do you want to apply. Usually i have, at least 4 “fin cant templates”: thruster, twinfin, bonzer and quad trailers.

If you use the system of measuring base to base and tip to tip you need to vary those dimensions every time you use a different fin length. That’s why i never used that system. Well, truth is that i used it once, when i shaped my second board using the fin templates Magicman gave me and the tip to tip /base to base numbers he gave me (THANKS MM!).

So, i can’t help you on the tip to tip / base to base lengths… sorry.

Coque.

Hi Coque, what is the angle for a 5 fins bonzer setup? 60º?

Thanks.

If my memory serves me: 19 degrees for the bonzer side runners. That means 71, or 109 degrees on the semicircle measure tool…

I’ll search for the right number at home.

Coque.

The most accurate method for doulbe checking cant that I have seen uses a small bridge to span any V or concave in the tail. Then it’s just a matter of adding (right fin) or subtracting (left fin) the cant angle you want from 90 degrees. If you don’t like futsing with protractors regularly, make jigs and mark the cant angle on them. Then you just spin the jig 180 degrees on the bridge to check the cant of the opposite side.

That looks like Jim from Lokbox making the Big Bucks .

Notice he uses only a dust mask doing resin work.

North shore style is no mask at all.

Ya you’re correct Kokua !

I’ve been sucking down too many dogs hairs lately,I guess ?

I guess it will remain a deep dark secret. LOL