So ive pranged my PB finbox. Hit a sandbank. Fin now sits at 45'. Rear of fin forced up thru top of box. Sides n front of box looks sound at planing surface. Damage seems to be only to the rear lobe of box. A split at rear centre of box vertically. Dont have time to replace looking for a quick fix.
Can i just fill the void made, with epoxy n cloth, get it close to correct shape then slap a fin head coated with release agent. Let it harden then pop fin out? Will try to get a good pic of damage to box.
DECREPIT n MARK AUSTRALIA
WHATCHA RECKON????

Helpful link, I have a similar job to do myself

Skip the release agent and leave the fin in the box permanently !.... it meets your immediate quick-fix need.

Do be aware that there will be a better than average chance than anything you do other than a proper box-repair, is likely to continue to leak... and some people ultimately find out what that means, when the bottom-skin comes aware from the core.

Select to expand quote

Stretchy said..
Helpful link, I have a similar job to do myself

Hey, im not sure what to make of that link. Did it work or did it fail twice? Pics kinda say fail?

I have to agree with Matt here. I haven't had a good look at how C.A. fin boxes are made. If there's a layer of cloth of high density foam at the rear of the box. It's possible the top layer of cloth is just fractured and the high density foam inside is badly dented, this could still leave the board water tight. In which case your idea is viable. Just use plenty of release agent!!!!

Sothe big question is, "did any water get in your board after your sand bank incident"? If it did, then a temp fix is very risky.

Decrepit, im guessing water would have entered. Board In the water about 30sec after damage occured. Its been in the sun since Tuesday arvo. The box will be replaced in near future.But not right now. This fix is temporary. Got an interstate mate dropping by. Need a second board to use.Its only gotta last a week or two of use. Then box will be replaced.

You can get an awful lot of water in in a week.
If it's got a gortex vent replace that as soon as possible with a standard bung. Gortex doesn't breath at all if there's water both sides. So until it gets replaced make sure you keep it out of the sun.

Initially, I was thinking pity the box is so weak. But recalling a couple of boards that had the tail snapped clean off, after hitting something with the fin. That's a much harder fix than yours, and also much harder to get back to shore.
Think I prefer the sacrificial box, although a sacrificial bolt is probably better.

Decrepit, board is 90s Speed F1 RB. No ventscrew. I also thought PB screw or barrel nut was supposed to let go before damage occured? But fin wouldve then been lost id think.. Screw was bent about 30' 10mm from tip. Made removing quite difficult.

No vent could mean it's closed cell foam, if that's the case, you're cool to do anything you like. Your temp fix sounds as good as anything I can think of. But I've known people with a very stuck fin after a similar operation, but that may have been with a tuttle that has parallel sides. It just needs some small undercuts, and the fin doesn't want to come out. the double tapered PB should be OK as long as it's well released.

That board needs to be dry docked until properly repaired. There really isn't such a thing as a waterproof temporary fix for a cracked fin box.
When using the board, strong lateral forces are put on the box by the fin, any temp fix will open right up, in comes the water.
So you have to ask yourself, how important is this board to you?

Decrepit, EPS core. No sandwich lay up. Layer of uni directional then layer of cloth over. Apparently the boards were layed up then compressed in a mould. 80s-90s technology.
Mastbender its my favourite 90s RB. Thinking i should wait til my repair guy is back in town.

Select to expand quote

olskool said..
Decrepit, EPS core. No sandwich lay up. Layer of uni directional then layer of cloth over. Apparently the boards were layed up then compressed in a mould. 80s-90s technology.
Mastbender its my favourite 90s RB. Thinking i should wait til my repair guy is back in town.

That would be safest if it's eps

Select to expand quote

olskool said..

Stretchy said..
Helpful link, I have a similar job to do myself

Hey, im not sure what to make of that link. Did it work or did it fail twice? Pics kinda say fail?

I posted the repair method in that link, it worked perfect for me and was very easy. Board was near new and I had it trouble free for 3 more years. The carbon Art fin box is high density closed cell foam, no water into board, I can't say how another brand is done or if that repair would work with it

My damaged box before repair

Select to expand quote

decrepit said..
You can get an awful lot of water in in a week.
If it's got a gortex vent replace that as soon as possible with a standard bung. Gortex doesn't breath at all if there's water both sides. So until it gets replaced make sure you keep it out of the sun.

Initially, I was thinking pity the box is so weak. But recalling a couple of boards that had the tail snapped clean off, after hitting something with the fin. That's a much harder fix than yours, and also much harder to get back to shore.
Think I prefer the sacrificial box, although a sacrificial bolt is probably better.

After hitting a fish, not mine but a mate's

BIG FISH.

Firiebob, mine looks to be considerably more crunched than yours. Upper rear surface ( closest to deck) of box is really blown out. 3mm crack just visible on deck. Hard to get a good clear pic of it.

Also you could do the bung up and let the board heat up a bit to check if it's still water tight before you choose your repair method when it's warmed up spray some soapy water and check for bubbles if there's bubbles a more extensive repair is needed !

Select to expand quote

olskool said..
Firiebob, mine looks to be considerably more crunched than yours. Upper rear surface ( closest to deck) of box is really blown out. 3mm crack just visible on deck. Hard to get a good clear pic of it.

And so I say no quick fix

You have a buggered fin box, and the deck laminate, and where the bottom meets the box.

Really, the fix is inserting a new box into a 20cm x 4cm void that you need to cut out. And a bit of deck and bottom laminate work (that bit is minor)

Filling the bits around a box that is basically detached from the rest of the board will not be strong, as it is ignoring the role the deck and bottom laminates play in holding that box in. It is like if a brick is loose in the wall of your house, and you smear some mortar around the perimeter crack and expect it to be as strong as before. It will look good and may be servicable, but will take considerably less force to dislodge it again.



What board is it?

Mark, 1991 Speed F1 RB. Eps core, pre sandwich construction. Layer of uni directional then layer of cloth. No ventscrew.
An oldie, but a goodie.
Well worth redoing. Chucking a PB in has really improved performance, as i can use a REAL fin. Regularly crankin it to 25-28kts.