SUP Sports fin doesn't secure

[mik911]

I have a SUP Sports Wardog center fin off a Hammer I used to own.  Tried mounting the fin on another board (Hoe Nalu), but it doesn't secure. The screw tightens down, but the fin is still loose in the fin box, freely moving up/down the fin box.  Comparing the fin base where the screw goes in, the Wardog fin is deeper than my other fin, thus despite tightly screwed to the nut, is still free to move around in the fin box.

Does this fin need to be cut down/sanded down? 
Has others had this problem?

[Bean]

There are two slightly different types of longboard boxes out there, and I’m sure Warren will chime in to explain how to modify your fin to work.

[Billekrub]

Since no one else has piped in,

Longboard fins use the same box as windsurf fins, called A box, or US box?; or, at least I have found them interchangeable to mount.  There are two depths.  Worst case, one has both types of fin box in different boards and cannot readily share fins between them.  This description assumes the screw in in the front, though some fins have the opposite.

Those fins for the deeper box have an extra 3-4 mm (visual guess) of depth in front.  It is easily rasped off for the more shallow box.  Or, one can also replace it if familiar with Epoxy and glass resin.  When using the shallow fin in the deeper box, the nose of the fin sinks below/above the hull and often works fine; causing a small rotation of the fin forward and some possible loss of efficiency. 

When using the deeper fin in a shallow box, the front of the base sticks out of the box and is not fully seated.  Maybe, that is what the OP describes.  If not fully seated, a marginally tight fin base might remain loose.  Even if one shims the fin with a thin material, such as a thin film or soft drink can material, the front of the fin sticks up and must reduce fin efficiency--not very pleasing.

[mrbig]

Lots of info out there.

Bahne Box and US box NOT interchange.

A fin with little hump will NOT fit correctly even if you sand it off.

The pins are located differently and they are not the same the same thickness.

What a revolting development to quote Bugs!

[mik911]

Those fins for the deeper box have an extra 3-4 mm (visual guess) of depth in front.  It is easily rasped off for the more shallow box. 

When using the deeper fin in a shallow box, the front of the base sticks out of the box and is not fully seated.  Maybe, that is what the OP describes.  If not fully seated, a marginally tight fin base might remain loose.  Even if one shims the fin with a thin material, such as a thin film or soft drink can material, the front of the fin sticks up and must reduce fin efficiency--not very pleasing.

Thanks Bill,
Yes this is my situation.  3-4mm extra depth to the fin (where the screw goes through).  When screwed in tight, the fin does NOT stick up, but the fin is not fully seated, so still move fore/aft in the fin box
As suggested, maybe i'll rasp or dremel 3-4 mm off the fin base.

Mahalo

[PonoBill]

Try shimming it before you start grinding, especially since the fin does not stick up out of the box. Mylar works well, or any hard plastic. I use aluminum, but that's because I have hundreds of scraps of it in various thicknesses, and yes, beer can aluminum is fine. The fin is not supposed to contact the sliding nut. It sounds like that's what is happening--that the screw pulls the fin down deep enough for the nut to pull up tight against the fin--which leaves the fin free to slide--instead of the fin being snug in the box with enough gap to leave the nut tight against the upper edge of the inner slot. If the fin is not standing proud of the box then that's likely what is going on and a shim along the sides of the fin plug will fix it. You can use about anything just to see if it will work, even cardboard, but for a lasting job you need something hard enough that it won't squish and loosen over time.

[JimK]

+1 to PONO

JimK
Extreme Windsurfing

[Bean]

Just to follow up on the two/too similar longboard boxes in use today.

http://www.blackprojectfins.com/which-base-do-i-need/

[mrbig]

+1 Bean. I knew it was out there somewhere. The Makini Fin site also had the info, but not as clear.

A final caviat. If you use a screw that is too long in the box, it can (and will) damage the fin box.

Don't ask and I won't tell. I use Dr. Pepper cans as shims. It's the damn pin being in a different location that causes a lot of the trouble.

My first MFC fins with the hump taught some painful lessons trying to get them to fit in my Exocet Marlin - may it rest in peace!

[Billekrub]

+1  Pono, mrbig, et all

[mik911]

Great!!  Adding shim sounds easier than rasping/grinding fin.
Great info here as usual--thanks!

Since you guys insist, I'll down a brewski now, so I'll have aluminum for shim.
Gotta do what you gotta do:)

Mahalo!

[SUP Sports ®]

Aloha Mike,
All of my center fins are designed to US box standard...they are produced based on my CAD files...then, QA checked...etc...
Aluminum cans work fine for shims if you are using one of the other Chinese or Euro center box variants...etc...as does plastic packaging sheets or plastic bottles..

https://supsports.com/sup-fins/

[mik911]

Wardog,
Thanks for the reply.
Yeah, the 11.mm measurement on your fin is 'deeper' than the fin box allows on my non-SupSports board.
Want to take advantage of using your fin, so shims are next.

Mahalo [had one of those too!:)]

[Wetstuff]

Warren...  It would be nice if some of the major brands handled an inquiry as well as you. Props. Too bad a positive feature had to be defensive.

Jim