Futures fin box installation

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I am trying to finish up a composite sandwich quad. It has an EPS core and Divinycell rails and skin. It also has some stragetically placed basswood and balsa.

This board still needs a sanding coat and I'm going to paint it, so I didn't need to be neat about marking the box locations.

I started with 4 Futures rail boxes. Futures makes several types of boxes, their standard fin boxes come in a 3/4 in depth and 1/2 in depth. The 3/4's are used for the rail boxes and the 1/2 in for the trailer fin on a thruster. Now quad fins come in different flavors, the trailers come in 1/2 depth or 3/4, so you have to plan for that at the this time. You'll see that all of these boxes have the Futures "F" logo in the back - those are the rail boxes. The trailer boxes have a "X" at the back.

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This is the side view of the boxes you can see the reinforcement ribs and the depth of the base.

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One last picture of the box. If you look at the F logo you'll notice that you can see the white napkins through it. The logo is a whole - after the box is glued in the epoxy or ploy resin will ooze through and provide a tighter bond.

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The first step is to mark out where you want the boxes. There are many variables to consider. Toe-in, distance up from the tail, distance from the rails...etc. So, after you have made that determination, you can lay out the basic location of the boxes and the line for the inside of the foil. That's what this shows.

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Once the location of the boxes is established, you can trace an outline of the boxes. I do this by turning the boxes upside down and alinging with my marks.

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The folks at futures sell a routing jig for installation of their boxes. It's not really necessary but makes the job easier if you have to do a bunch. It consists of a router, a clear plastic alignment tool, an aluminum plate that is the foundation of the jig and a plastic circle that allows two different depth cuts.

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The process is fairly simply. Lay the aluminum base close to the location that will be cut. Then use the plastic alignment tool (which has markings for the center and the outline of the box) to insert into the opening of the aluminum plate and line up with the markings on the board. Once done, the plastic tool is removed.

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The plastic ring allows two depths to be cut. One that is just for the flange and is very shallow and the other that is for the full depth of the box, but very narrow.

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The fin box "holes" are routed in two passes. You'll leave the aluminum plate in place until the hole is fully routed. You will do the first cut. Turn the router off, flip the plastic guide ring over and then make the second pass. It doesn't really matter which cut you make first - shallow or deep, just make them both before moving on.

What the process looks like:

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All four box holes routed and ready for box installation.

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When gluing the boxes in, you want to make sure they are aligned properly. The best way to do this is to install the fins in the boxes before gluing them down. Insert the set screws then tighten the fins in.

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Make sure you have help Woofie aligning the plastic sheeting for me.

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All the boxes installed

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The next stage is to laminate over the boxes after the resin has cured. Then grind down the center section to expose the opening to the fin boxes to allow the insertion of the fin.

After that I will apply a sanding coat of epoxy and then finally I will paint the board before a final clear coat.

Now, you're ready to install some boxes!

[sagmanaur]

Jeff,

So how do you determine the angles of the fins, is there some sort of water tunnel (a wind tunnel using water) to see what kind of effect the angles of the fins are making. Or is there some sort of standard that Futures came up with, or an industry standard.
It seems like there are a lot of factors to consider (vertical angle, horizontal angle, angle of second fin with the first), especially when using a twinzer configuration?
Has anyone ever tried using 2 different angles on a dual fin configuration that would be better for a left side vs. right side wake? You really got my engineering mind in gear with all of these construction photos.
I wonder if anyone has come up with a fin that can be locked into different angles by simply rotating the fin (similiar to a wakeboard binding attached to the wakeboard).
Food for thought.

Jeff, did you get a chance to look at the pic/video I sent you last week?