Finbox angles with concave or vee

[ChrisM]

Hi everyone, I have a question about setting finboxes
the new ones I bought have angles of 5 degrees or 9 degrees FCS Fusion side boxes.
When placing fins in a vee tail or concave tail do you set angles differently to compensate for the v or concave .
if there is a 5mm vee at fin position the extra angle added to cant if finboxes are installed flat or flush with bottom is 1 -2 degrees so cant is extra from 5 to 7 ,. and if its a concave at fin point the cant is less as the flush box will point the fin back at the centre, perhaps 1 degree less.
Does anyone worry about this. ? Thanks in advance.

[Huck]

These questions come up again & again, you can find a lot of discussion in the archives. Try rephrasing your search in different terms to get more results.

Here’s a couple I found: link 1

https://forum.swaylocks.com/t/relationship-of-quad-fin-single-to-double-concave-and-cant/40680

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Link 2

cant fins angle on concave bottom

  looking at your diagram, look at the ‘green’. Its the angle in excess of 90 degrees. So a proper measurement would be in the range of 0-10 degrees.  Cant can perhaps be described as a fin leaning toward the closest rail and is the angle in excess of 90 degrees leaning towards the rail. Alternatively a protractor could be put to any side of the fin to measure the angle off of the perpendicular(90deg.)   A fin leaning towards the rail would have a positive cant of 0-10 degrees. A fin pe…

[ChrisM]

Thanks for your reply I will read the link you posted much appreciated

[OSS1]

Yes the archives. But yes if you have a desired cant you have to compensate in some way to get that cant. It occurs to me though that routing the hole is the best way to compensate. Possibly using shims under the jig.

[OSS1]

The link Huck posted is a solid explanation.

[Huck]

There’s two links, to two different approaches, check both the links out

[stoneburner]

I could be wrong.
It is said that tail Vee in the Retro Fish made it easier to put the board up on its rails.
But IMO, for the Retro Fish, tail Vee created the desired fin can’t for fins glassed on at a 90-degree angle to the bottom.

[Steve2]

This response is somewhat related, but more appropriate during the shaping phase. Sift thru Zack Flores’ you tube channel on shaping concaves. My recollection is that he leaves the area near the fins telatively flat and shapes the concave between the fins.

I like how he handles this scenario, as the fins keep the originally manf. Intended cant.

Not sure how he handles this with vee.

[ChrisM]

Thanks
I will check it out.
I find the info passed around really helpful

[Railwaysurfer]

I would have thought that the very subtle angle created by either vee or concave is going to have a negligible affect on the fin angle?
Would a solution be to route the boxes when the bottom is flat and then shape the contour into the bottom? One side of the box would require a little more sanding but it surely couldn’t be too much?

[stoneburner]

5-degree Vee (below) would create 5-degree fin cant – as mentioned in OP’s post.

[MRat]

Railway, You don’t want to do that. Shim the Jig so it’s level if you have to. To fine tune your cant if it’s off snap or cut a stir stick and use the flat end to scrape/press the inside the route down where the flange sits to the desired depth on whatever side of the box needs adjusting. Get the cant where you want it before setting. Pour/set boxes, Check your angle, tape it in place if you have to and then check again.

[ChrisM]

Thanks guys so helpful .

[OSS1]

As described by mrat; Shim the jig level and go from there. I’m a “Soft V” proponent so it never is an issue on my boards. I don’t do faddish multi

• channel bottoms; so again not an issue. I do double barrel concave out the tail with slight V, but place my fins just outside or on the edge of the concave. Concave is about the width of a Louisville slugger wrapped in Indasa. Starts about the front edge of the forward fins. Goes from single to double. Single starts under the front foot. I like to keep it subtle. Not too deep, but not so shallow that you can’t see it. Some of CI’s scrubbers act like they don’t want you to notice that there is any concave in the bottom at all.

[Railwaysurfer]

That makes more sense! Great advice, thanks.

[lemat]

That’s way fcs2 and fusion plugs avec 3 angles: 3° for Vee, 5° for flat, 9° for concave for standard 5° thruster cant. For future angle is on base fin so plug is set flat (ie 90° from stringer).

[OSS1]

That’s right lemat. That and the fact that there is a weights savings over Futures in four and five fin boards is why I prefer them for those applications. Future is still my “go to” for Thrusters and Twins.