If you are in the position of having to get a US fin box replaced/refitted, is it possible to have a powerbox fitted instead?

Obviously the position of footstrap screws etc needs to be considered, but is addition of the recessed hole in the deck too big an issue for it to be worth while?

Leech said...

For starters, is the tail of the board thick enough to fit a powerbox?

2ndly, why would you want to do away with the ability to shift the fin forward/backward on your waveboard???! It's one of the best ways to tune the board to your style!

It is a 96L Starboard Kombat so I think that it is probably thick enough. Practically every other FSW manufacturer uses powerbox and given the slalom capabilities of the board the US fin box is very restrictive wrt what fins you can buy, especially around/above the 30cm mark. Personally I don't think the US system is a good idea when you get to that size of fin due to the torque that it must be under; possibly why this may be the second time that it will have had to be replaced.

Hey Arlo - saddened to hear the Kombat needs another new box - I am feeling guilty for selling it now - I think starboard have got a bit to answer to as the first one went within 9 months with side, front and back cracks - as you say from using the big fins with the US box.

Who is fixing it this time ?

you could get it done but it would be expensive, you would have to chop a big chunk of foam out to allow you to have a block of high density foam around the box roughly 300m long 200 wide and right through to the deck...

Good Luck arlo - Pete used I think his name was "Robbo" took a Bl**dy long time though - maybe he will fix it for free cause the repair failed!

sorry about that it was an attempt at humour!

Hope it's not going to need it

clear packing tape. make sure board is clean and dry before applying.

best thing is to silicon the fin into the board.

decrepit said...

A lot of people think putting a layer of glass over the top of the box is the best way to go.
But as you've discovered it's got big disadvantages.
Resin doesn't stick very well to the box, and that top layer can delaminate off the box very easily.
If you have a leak this makes it hard to see, so you could be taking water without noticing.
If you do notice the delam, it's very hard to tell if there's a leak.
I always put my boxes in now, with glass wrapping under the box, and back onto the bottom surface. without any glass over the top of the box. This is stronger and makes it very easy to see exactly what's going on.

Haven't fitted a powerbox, not sure how much extra support it needs, but 300 X 200 seems a tad excessive.

And certainly agree that putting big fins in US boxes is asking for trouble.

What would you know decrep? Oh yeh I forgot you've done 300 of them ........done 3 of mine....... and if I want more done in the future I better show some respect

Gestalt said...

best thing is to silicon the fin into the board.

thought i'd clarify, the silicone comment was if you just want to try and keep it going for a few months or so to get you through to may.

decrepit said...



I leave the box a smidge proud of the bottom surface, then it gets lightly sanded flat. once painted you can't see it, unless a crack develops, then you can see if there's any salt around the crack after sailing.

The glass wrapping gives a lot more strength, it stops the box compressing the foam around it, so it's much less likely to come loose.
I always use closed cell foam around all boxes and plugs, so if anything comes loose it doesn't suck water.

The only problem I can see with this is that some of the powerbox weed fins I use sit in front of the box and are meant to sit against a bit of foam which is against the bottom of the board. I must remember to measure carefully.

So far I haven't had to replace a box, but I keep on referring to the boardlady site as well to see how she does these. She shows that she surrounds the box with divinycell and joins it all together with an epoxy and q-cells paste. I guess this must be the same as you are suggesting. It sounds bomb proof in comparison to some of the standard boxes she shows.

I can imagine the first time I try this I will end up with a fin at a permanent angle

Of course, Murphy says that I will need to replace a finbox when I have the least amount of time...

Cheers.

the shaper that makes my boards does a combination of both and i have no probs with us boxes and 30cm fins.

he sets the box into the routered hole with glass as per decrepits advise and lays the glass back across the foam.

then he glasses the bottom of the board with the glass stopping on top of the box. the layers of glass laminate to each other and it makes the hole area very strong. if the glass doesn't bond to the face of the box it is still all ok because it's alos laminted to about 10cm of the glass that wraps under the box. he uses this system cause it also allows vacuum baggin of ply and or carbon plus looks great with a continuous finish which hides the box edges.

after the proocess he files the edges to clean it all up.

decrepit said...

Nah still prefer my method, I put the box in last, after the board has been glassed, that way the wrap around glass sits on top of the sandwich. The other way it's just sitting on foam, still strong, but it's relying on it's adhesion to the bottom of the sandwich for strength.

hmmm. maybe he does do it your way. the picture in my head is now sketchy. i'm confused....

next time i'm in the factory i'll look. i like to visit. the smell, the foam, the new boards at their different stages.....

decrepit said...

Ahh the smell, the foam, --------

We've all got our different ways of doing things, I'm not commercial and probably take a lot longer to do stuff. Somebody who's doing it for a living has to think about their time, especially to compete with the cobra factory. So quite often if it's a lot quicker, and doesn't sacrifice appreciable strength then that's the obvious way.

hi decrepit,

pete, like all custom builders definately takes his time and is very proud of his work. i know he does the double wrap thing with his boxes but can't remember which way now that you have put your way on the table. i have had this specific conversation with him in the past, asking how he managed to bond the outer layers to the box. he explained the overlap created with the box epoxied in seperately which seals it all tight so it sounds almost the same. trying to visualise all of the boards i have seen there has confused me somewhat. outer layer over or under?????

he's been doin it for a very very long time now and makes his own tuttle and power boxes in moulds. bloody stong they are.

i shouldn't talk for him but he also does most of the repairs around SEQ. so he has seen every board ever built.

these days he vacuum bags everything. going from hand laid to vac bagged made a massive difference to the boards weight/strenght ratio. all good stuff.

i don't think he will ever compete with cobra or the like. he's a lifestyler. so if it's windy he's sailing.

i do love visiting the factory. the smells are addictive. he also fixes all of my gear for me at mates rates. and some of those repairs have been fairly large. like whern i ripped the back off my formula board when surfing a wave and running a ground. he glued it all back up for me.

sorry to hijack the thread guys.

cheers

is it a dlam job, i saw a quatro custom board what some how delaminated off of the fin box.

I haven't done a Powerbox (would not touch them!) but I have replaced US boxes with Tuttle boxes in Polyester boards. I used the plastic 'Chinook' type and they go right through the board from top to bottom. A couple of layers of glass each side (wrapped around) and flush with the bottom. Actually, slightly high of the bottom and sanded back to flush as Decrepit does. On the deck side I leave the glass skin on the board and shape the box to fit perfectly. Then wrap the box in whetted glass and sink it in. Holes are drilled for screws later. I think the plastic Chinook type Powerbox is fitted in the same way with the exception of the holes - only one!
If I was doing it on an Epoxy Styrene board I think I would add a layer of PVC foam each side of the box and at the ends for support and to help seal the core.

decrepit said...


Trouble is without pulling the board apart it's very hard to tell.
It's very common for the glass on top of the box to delaminate from it, without a problem.
Especially if there's closed cell foam and a layer of glass around the box. But you have no guaranty that's the way your board's been made!!!

If you "waggle" the fin does the box move? Is water squashed out?

If you leave the board in the sun for a short time with bung done up, right way up, with back of the board the lowest point, does water start coming from the box?
When you release the bung do you get a hiss? you could put some water around the bung and check for air bubbles.

Try these it will give you an idea what's happening.

I'll give it a go over the weekend.