Cavities for Futures fin boxes

General Discussion
1

Hi people, about to do the cavities for fin boxes but it’s the first attempt so need a bit of hand-holding please :slight_smile: got the One-Pass install kit, so properly tooled up.  

Got two questions:

  1. I’ve followed the Futures youtube tutorial, used the shims and the Timmy tool to get the height of the jig plate correct and made the cavity on a scrap piece of foam.  I’m not sure how deep the fin box is supposed to sink but this looks to me like the cavity might be a bit shallow.  The shallower part of the cavity is barely 1mm deep. The router bit has been pushed up against the nut of the router as per instructions.  I should disclose at this point that the router I’m using is a Katsu 101748 which as far as I understand is a carbon copy of the Makita 0701 (0700 in the US).

  2. The Futures tutorial for the One-Pass indicates that “when alligning the left fin, use the right hash marks on the target” and vice versa.  (tutorial link: https://youtu.be/Qq3CXyGOoLY?list=FL_k-G2HuSxGfnNV8kRe0KGA and the target hash mark instruction is at 2:40).  Is the ‘hash mark’ as per photo?  And if so why use this instead of the middle?

Cheers :slight_smile:

 



2

I believe the inside hash mark is used because the fin line should be the fins inside edge and not the center of the fin. I may be wrong though

3

The outer marks on each side of the target are for flat sided fins. (usually the front side fins).

If you don’t use them, your fins will not line up on the marks.

Always move target toward rails on flat sided fins.

Does that make sense?

4

Umm not really to be honest but thanks for the response… does the ‘flat sided’ refer to the foil? I’m building two fishes and one thruster.

5

The center bombsight line for the center of double foiled fins. The right/left lined for flat side of single foiled fins

Hard to tell from the pic but it looks like your flange rout is too shallow. Set your bit deeper and try a new test rout. Dry fit and keep testing on scrap foam until you get it right - The box flange should never be proud, it must be just below the foam and the resin dam above it.enough to be ground away later

6

How does this one look?  

And just to be 100% sure… in the 2nd pic, the black line should be the depth of the finbox, right?

And thanks for the clarification about the target. 


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7

I heard there are a few big names in the biz, who just use the middle target for all fins. No chance of screw ups that way.

Some of those do look shallow. Add a washer under the head of the router bit.

8

the flange route is not deep enough, you should not see the flange above the foam.  less shims is the easy fix.  

9

Great, thanks for the helpful responses people.  I think I’ve got the gist now.  Thanks for the assistance :slight_smile: