Installing Fin boxes

General Discussion
1

I just finished shaping my 8’9’’ PU longboard and am now looking to glass it with PE. This is my first attempt at installing fin boxes. The side fin boxes are fcs fusion and I’m not sure what type the center fin box is, but it looks similar to the one posted here http://www.foamez.com/fin-box-105-black-p-351.html.

I’ve looked in the archives and on fcs’s website and decided that I can go with the following two options.

**Option One:**

Use a router to make the hole in the pre-glassed board.

Lay a piece of fiberglass over the hole and push it into the hole with the fin box,

Take the box out and fill the hole partially with resin

Put the fin box back in the hole making sure it is laying flush

Put a test fin in the box to make sure the cant and toe angle is correct

Spread excess resin around the extra fiberglass that is surrounding the box

Let dry and take test fin out

Cover opening of box with tape

Continue with normal lamination being careful to avoid fin boxes

**Option Two:**

Use a router to make the hole in the post hot coated board

Make sure the fin boxes fit correctly in the hole

Fill it partially with resin and then put the box in the hole

Put a test fin in the box to make sure the cant and toe angle is correct

Let dry and take out test fins

Cover fin boxes with tape

Cover boxes with a laminated patch of fiberglass

Then hot coat the patch

Cut out glass on the area that had tape on it to reveal the portion of the fin box that will hold the fins

My main concern is strength and I am thinking the first option would be stronger, but slightly harder to ensure it ends up flush with the surrounding board when it is done. Am I right in this assumption? Also, are there any other upsides/downsides of either method? Or are these methods the wrong way to install the boxes?

I was thinking of installing the center fin with the opening to the air, but I heard that it is supposed to be the other way and then you grind the fin box open after hot coating the board. Which way is correct?

Finally, I am going to do some resin swirls, so would either method interfere with the look of the swirls?

2

I think ya kinda got it a bit confused!
First of all, the center fin box goes in last, after
the bottom hot (sand) coat but before sanding.
The side fins, fcs fusion, futures, lokbox & probox
all can go in at two different times.

  1. Route into the foam before glassing, set with
    a small amount of resin, cant, etc. Then tape off
    the opening and lay out your glass. You might need
    to cut a relief slit to make the glass lay flat on the sides
    of the box if you don’t have much experience setting boxes.
  2. Lam the bottom, lam the deck. Clean up the lap in the
    tail area. Route the box, add resin, cant, etc. Once the
    resin has gone off (be sure to squeegee of excess) add
    football patches or a full tail patch if you want. This looks
    cool if you are using volan. Hot coat once the patches have
    set. Make sure you tape the holes!! There are lots of little
    details you can do to speed up production but if you are
    just doing one at a time, no worries! Hope this helps!
3

ok cool. This makes sense. So, are there any differences in terms of durability if I install the side fins before glassing compared to after laminating. Also, is there any reason why the center fin goes in after the hot coat instead of at the same time as the side fins? Thank you for the advice.

4

Most of the box makers will argree that side loading
is very important so that the force is distributed along the
glass. Foam is never strong enough. If I had a customer that
was really hard on side fins, I would foam route first, lam bottom,
lam deck and then football. If there was an airbrush on the bottom
or a foam swirl, I would route after the lam and then football.
The center box is designed to go in after the hot coat, that is what
the little tabs are for. There is some disagreement on how to
install, such as with a patch of cloth inside the route, cut fiberglass
strands or just resin. I like the just resin method. If you do hit
something (or someone, LOL) with enough force to rip out the box,
you don’t want the tail going with it!! Anyway, just my 2C!

5

That was helpful. I’m trying to learn why people go about a certain process, so I can adopt different aspects to make the best process for me. Haha hopefully I dont hit anyone, but yeah hitting something and losing more than just the box wouldn’t be fun to say the least. Thank you again for your 2 cents! I’ll try to post some pictures when the board’s done.

6

I would recommend routing the side boxes after the lam, and finishing with a glass patch. The

issue with routing before the lam if you are not super experienced is getting it to sit flush.

The center box is typically route the hole, sink the box with cabosil (or microballoons) and

resin, and grind clean. If the center box sits on the stringer, it will be plenty strong. If you don’t

have a stringer there, you want to sink the box with 1-2 layers of glass instead of cabosil in the

resin. Also - the open side of the box up, with masking tape over the opening to keep the resin out.

7

Yeah I was thinking that getting it to sit flush would be a problem, but I think I’m going to try to do it before the lam anways. I just figure I’ll never be good at it if I don’t try. It will be sitting on the stringer, so I think I’ll try the cabosil. I’ve heard about it before, but didn’t think of using it. Ok, so I was right about having the open side of the box up. It just didn’t sound right when my friend told me that it was the other way. Thanks for the input.

8

Blakestah,

I’ve only done 3 or 4 single fin boxes and I can never get a clean route of the hole. Do you use a jig or do you have any tips for making a clean straight cut?

I was hoping fins unlimited had a jig for their boxes but I could never find one. If you’ve made your own do you have any tips for making a good one?

Thanks

9

I have seen some long boxes with a raised cap that is ground off after installation to open the slot. Ofishl makes them…

http://www.ofishl.com/systems/boxes.html

10

Jigs are essential. Just trace a box on a thin plate of aluminum and route it very slowly and carefully, or have a machinist make you one.

11

I made a center box jig for a preglass install of an O’Fish’l 10.5" box.
By clamping scrap particle board tightly against each side of the box lengthwise then cut out two smaller pieces for each end and tack glued them all for together. Later I realized the particle board didn’t have enough depth for the 1/2" top bearing bit I had so I used it to route a 10"x20" piece 3/4" of melamine.

Worked well. But the O’Fish"L was scarey because unless you grind off the top you can’t put a fin in for alignment so the route has to be perfect. I glued the box in 1# foam with Gorilla glue, brawhahaha. But did put in some unseen wood reinforcement bits.

12

Mahalo! I suspected as much. Got to find some plate aluminum. I have some really nice shelf pad that looks exactly the same as the stuff on the Futures jig. MIght take the extra time to make a good one.

A glasser friend said the O’fishl boxes are nice but too much vee and tail curve can make them difficult to line up.

Thanks again!

13

This is even more of a problem with other fin system boxes. That’s why I created a jig to hold the box while it is glued into the board - it sets the cant, toe, and depth of the box relative to the plane of the board bottom, centerline, and lam. All of a sudden the route can be a little imperfect, but the box position is perfect every time. You could make a holder for the center fin boxes that did the same thing - it makes life a LOT easier. And it is not difficult to design or make.

Mahalo.

14

i remember trying to convince myself i could rout a clean line…

jigs are as easy as you want them to be

15

I think thats awesome advice “surfteach” about not putting the cloth inside route. I usually do just the resin method as well.