Author Topic: usbox versus longboard/surf/bahne box  (Read 502 times)


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usbox versus longboard/surf/bahne box
« on: April 14, 2021, 07:58:39 AM »

US STANDARD Base (a.k.a. usbox)
Fits Starboard, JP-Australia, Fanatic, Mistral, RRD and most production brands with an origin in windsurfing. This is the same fin box thatís found on many windsurfing boards and is wider and deeper, with the pin set further from the deck of the board. The base is 9.2mm thick.

US SURF Base / Longboard Base / Bahne Box
This is the same box that is standard in many surf longboards. It is a narrower and shallower base as used by SIC, Infinity, 404, Naish, Flying Fish and many more. Narrower and shallower than the US base, these boxes have the pin set closer to the deck of the board. The base is 9.0mm thick.

Sharing the information.  Most of my fins are the standard longboard base.  I have an older starboard which originally shipped as a 2+1. I have been trying to find a compatible usbox center fin (~4.5") to make it a thruster.  Anyone have any stories to share about getting a thruster fin setup on a usbox board like Starboard, JP-Australia, Fanatic, Mistral, or RRD.
Quiver Shaped by: Joe Blair, Blane Chambers, Kirk McGinty, and Bob Pearson.
Me: 195#, 6'2"


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Re: usbox versus longboard/surf/bahne box
« Reply #1 on: April 14, 2021, 11:21:01 AM »
You can easily shim a longboard fin to fit a US box, though the fin will be a little recessed in the box, and you can make a US base fin fit a longboard box, but it's a bit more fiddling. I've done it a few times to make a fin I like fit my boards. I press out the pin then grind/sand both sides to get the fin to fit snugly. A belt sander is ideal for this. Then I redrill the pin hole offset back enough so the holes don't overlap. I have to put the pin in with the fin almost flat since the radius of the front curve isn't right, but it goes pretty easily and the modification is a quick job once you've done it once.

One time when I lost the pin while I was fiddling with the fin I drilled a dimple where the pin needs to be and glued a loose ball bearing into the dimple. It worked fine.

I'm nuts enough to do silly amounts of work to save a good fin. I broke the fin tang off one of the magic old MFC fins and replaced the tang with a spring-loaded ball on both sides. Stupid amount of work to do as a one-off.
« Last Edit: April 14, 2021, 11:27:50 AM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.


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Re: usbox versus longboard/surf/bahne box
« Reply #2 on: April 14, 2021, 01:50:53 PM »
Or you can screw up like I did, when the custom SUP I ordered came with a center box that was too tight to use any of my quiver of windsurf wave fins. I had the board built with the intention of sometimes using it to wind SUP in light wind at spots in SoCal and it needed to be in single fin configuration. I filed the box out, but of course went just a tad too far, so since then I have had to use multiple shims with all the fins.


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