I've got a wave fin which needs saving - I've seen pictures of a few fins with a stainless plate fitted around the front where the screw goes, and I'm happy to make one (or two) of those, and to grind the fin down so that the plate sits flush with the fin head.

I have some stainless sheet left over from a kitchen fitting - pretty thick stuff, but that shouldn't matter too much I wouldn't think?

My question is what are they held on with so that the fastening doesn't interfere with the fin fitting in the box? Is the stainless countersunk somehow?

yep the stainless steel is rebated into the fin so the outside of the fin saver is flush with the face of the fin base.

the top of the fin saver has a positive lock into the fin. you need to scribe an aris into the end of the fin to take the fin saver.

then just rivet the hole thing together with stainless stell rivets.

The stainless is contersunk (well, pressed in a bit really), and you use a countersunk screw with a special nut that looks more like a female screw.



For $10 it's easier to buy one, I'd think.

Thanks Neb - that picture is exactly what I needed!

Unfortunately there are no windsurfing shops in the near vicinity, and the ones further away would really prefer to sell new fins. I haven't seen anyone selling or using fin savers here.

Time for some cardboard, scissors and a mockup I think.

i see the picture but i cant understand what they actualy do for the fin ..... increase strengh? stops damage when hit bottom ??

They're a fix for when you've snapped the tab off the front of the fin. Instead of binning an otherwise good fin, you modify it slightly, and put a fin saver on.

See the middle fin in this pic:

Can you get these for powerbox fins?

so they can only be used on u.s style fins ? ( wave fins)

Well they're extended tabs, my understanding is that US box is the only tab style fin.

I fix mine with fibreglass and resin, just grind a taper onto the base of the fin where the tab has broken, and build up new fibreglass.
I think that would be much easier than trying to bend thick stainless that accurately.

I've had a couple of goes at building the fin up with glass and resin, but with only very short term success. Apparently my method wasn't up to scratch, and they just kept snapping off without even any decent hits. Probably needed to taper further back on the fin head.

I'm now running stainless screws with keepers, and 4mm nylon nuts (home made) the theory being that the screw will rip straight out of the nylon on any sort of impact, and leave the fin well alone. I made 10 nuts at the time, so they're basically a disposable item.

Neb's pic makes my stainless look thin - I was able to cut it with tin-snips, but haven't tried folding it yet. I figure that I need to drill and press the indents before I can fold it, and I need to get some fastenings before I can do that.

Hi, All,

555: Suggest that you don't re-invent the wheel. Suggest that you e-mail a windsurf shop on the east coast of Australia (have a look at the Neil Pryde website to get the addresses in Vic, NSW and Qld), to see if they have them in stock and if so, get them to mail you some (after giving them money, of course).

Nick0, Easty: Yes, this type is only for US box (but see below)

Easty: the theory is this. When you hit an object, the foresection of the tab collapses as the head of the screw pulls through it when the fin rotates around the rear fin pin. By changing the whole tab assembly, you continue sailing and don't have to change the fin.

555: they do work: I've been lucky in having only one finstrike and can attest to their effectiveness. Naturally, after my finstrike, I didn't have another tab with me so couldn't replace it. Had to use another "normal" fin and was very nervous in case I hit another object.

Re Powerbox. Most of the nuts inside Powerbox fins are made of brass. When the fin hits an object, the stainless steel screw MIGHT pull through the thread, releasing the fin before major damage occurs. Personally, I've seen this happen only once during my career, when a guy hit Gilligan's Island whilst sailing full speed at Rickett's Point North. There was an almighty bang, he went A over T into the water, walked to shore and we were amazed to find that his fin was still in place and that the finscrew had pulled through the nut (but sunk to the bottom, never to be seen again). The guy put in another fin and finscrew, then sailed off again.

Most times during a normal reef strike, the fin pulls the finscrew through the board and you lose the fin, the finscrew and put a big hole in your board.

Some time ago, there used to be an accessory brass screw sold for Powerboxes, that was "universal" in that it was made using a thread that accepted the use of both Imperial and Metric threads (used on finscrews). The idea was that the finscrew thread engagement with the brass nut thread was tenuous: It allowed the finscrew to be done up, but stripped easily if the fin hit an object. Don't know if these nut are still around.

For those of you with Tuttle fins, I have never heard of a quick release nut for them and, because the fin uses two bolts to hold it in, I don't think it would work anyway (front screw might strip the QR nut, but then the fin would pivot or pull through about the rear screw)

Hope this helps.

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WindmanV said...

Hi, All,

555: Suggest that you don't re-invent the wheel. Suggest that you e-mail a windsurf shop on the east coast of Australia (have a look at the Neil Pryde website to get the addresses in Vic, NSW and Qld), to see if they have them in stock and if so, get them to mail you some (after giving them money, of course).

Some time ago, there used to be an accessory brass screw sold for Powerboxes, that was "universal" in that it was made using a thread that accepted the use of both Imperial and Metric threads (used on finscrews). The idea was that the finscrew thread engagement with the brass nut thread was tenuous: It allowed the finscrew to be done up, but stripped easily if the fin hit an object. Don't know if these nut are still around.

Windman - There's no wheel re-inventing going on here.. Wave fins traditionally use a fine stainless screw in a fairly thin brass nut. The idea is that the screw will tear out the thread on impact, and avoid damaging the fin. Pretty much what you outlined above for powerboxes

I don't have any brass, but I do have nylon. Substitution of materials maybe, but no re-invention. The only thing I've added is a keeper nut which saves me losing the screw each time I hit something hard. I'd think that tearing the thread out of a nylon nut would require significantly less force than pulling the head of a stainless screw through a stainless plate.

The fin saver at this stage is a way to replace the missing tab on my fin - not a disposable 'weak link' so much. I have already had a much appreciated offer from a fellow 'breezer to post me over a finsaver.

As Decrepit says though, I should probably have another crack at glass and resin to answer that need.

Made these to repair surf ski skeggs,1/4 tube inside 3/8 tube squeezed together in vice to req. width ,drilled for bolt. Drilled hole in fin and epoxied in.Would make a mess of fin if it were to break out but with nylon nut i think would be OK.

Pirrad, that looks much easier to make and simpler to fit, but there wouldn't be much fibre glass left around the walls of the fin. I'd prefer a smaller dia tube inserted into the fin, but that's going to make it harder to make. Probably OK as it is.

555, I make the taper at least 2cm long, doesn't need to be more than 3cm.