fin box thickness problem

General Discussion
1

Hello everyone, I need some help.

I am in the process of making a board and I want to insert a fin box into it. Unfortunately, I cut the board a little bit too thin at the tail for a fin box.

The board is 7/8" thick at the shallowest point where the fin box will be placed.

The fin box is 1 1/16" thick.

Should I just sand down the fin box until I get it to the appropriate thickness, or do I just continue the installation since it’s such a small margin?

2

Is it a single fin installation, and is it an FU Bahne box?

3

This is one of those think-ahead kinda things.

You will either take material off the top or the bottom of the box. Your choice. The lip probably is an extra 1/8th high for grinding flush anyway, so you could start there.

4

It is a 7.5" FU Bahne box.

It is for the center fin of a bonzer that I am making.

5

You can trim off top of box, but I’d just glass over the deck of the board with about 6 layers of cloth after you drilled thru and installed the box.

So what if it sticks out 1/8" at the very back, you don’t need to always stand there.

6

Howzit JLW, If it’s a Bahne box It’s actually 7/8" deep from the bottom of the tabs to the bottom of the box. No problem I do them all the time. Just rout as deep as you can without going through the deck and install. The excess in the tail can be sanded off. I find that with todays tail rocker the boxez usually balance in the middle of the box and both the front and tail end of the box are above the bottom so just sand the excess off. Aloha,Kokua

7

So wait, those tabs are meant to be sanded off?

I thought that the tabs were there for strength, not to be sanded off?

8

Howzit JLW, The tabs are there to sit on top of the edge around the routed hole and for the box to sit flat. But the bottom would need almost no rocker for them to work right since with rocker if the tabs are sitting on the edges of the hole then the center area of the box will be below the lip edge and after it’s sanded some of the boxes raised lip will still be there and you don’t want that.Aloha,Kokua

9

Leave the tabs. They get grinded off when you sand. Helps position the box when you set it. Most thinner boards are okay if you grind the back off after it is glued in.