10.5 Fins Unlimited Box- Why so tall above tabs?

Hey Guys,


Just a quick question as all of my fins are usually glass-on. 

I’m installing a 10.5" Fins Unlimited box and the lip or the box is about 3/16" about the tabs.  The 8.5" box is virtually flat with the tabs.  Just wondering why there is such a tall wall above the set tabs in the larger box and how you guys grind down this box?

Here’s a photo showing the difference:




keeps the resin out while allowing you to use a fin or jig to make sure they’re in straight…grind it flat with a hard backed pad and an 80 grit disc or so, doesnt take hardly any longer than the 8" boxes!

Funny you mention it cus I have one in black that I haven’t used yet,it’s for my next longboard.it’s gonna see some belt sander time before I install it though,I’ll just lay tape over the hole of the box for the install to keep resin out.

If there's substantial rocker curve through the box area, the ends of the box may sit somewhat high and the center almost flush during install, so the lip keeps glue out. Shorter boxes don't span as much curve, not as much of a problem.

Thanks Guys!

Just wondering why the same company would make the box so different???  That’s odd to me and the lip looks like it would take alot of sanding, but I’ll give it a try. 

I’m picturing a jig the same thickness as a fin, the cut to straddle the tab with two wings to hold the box at 90 degrees?  Tape or down or a weight while the resin/cab kicks?


ProBox makes a 10.5" centerfin box without tabs that allows you to install it before you glass (like a Futures fin box) as well as after glassing.

With highly rockered tails you have to shape the box to follow the stringer. I route the slot and drop the box in then sketch the curve on the sides of the box. Then I put it in a vice or clamp to a table and shape the curve using a hard Powerpad with 60 grit.  

This method eliminates the chance of hitting the foam or glass when grinding the box down. It also reduces heat build up from grinding friction which melts the plastic and gets all over the board.

Use 2 layers of 6 oz. glass when installing 10.5" centerfin boxes

All the best




Hello Tommy ,

I'm using the 10 inch Fins Unlimited box and the Hi Surf Box from ProBox Larry. After reading some stuff on Swaylocks I'm playing around with using the router instead of the grinder....just messing...the angle grinder is a great tool....

I like the tabs on the FU boxes ...I like the clean install on the Hi Surf boxes....Here's some photos to help with your Hi Surf box installs..I use a file to mark the center line of the  box......

manual sanding in fact is safer than using a sander as it grinds off easily. it doesn’t take long too