Ok ive asked this before n got a bunch of contacts. (SE Qld). NONE who will replace finbox in my 1991 SPEED F1 Raceboard. So im wanting advice on how to do it myself. Board has US box that seems to be leaking/ rolling.
1. Do i use PB or Tuttle?
2. Can someone in the know talk me thru all the steps??
3. Ive got a good basic knowledge of general board repairs but nothing as tech as finbox replacement.
4.HELP GUYS,FAVOURABLE WIND APPROACHES.



Thanks

Never done it myself. .. if I was to do it I would research...

boardlady website

there are few boardbuilds on YouTube showing fin box insert process

i think there are a few threads here on finbix repairs plus board builds showing box wrapped in high density foam and inserted

pb vs tb- if you plan on experimenting with big fins (phantom has 52) then deep tuttlebox if there is room

cheers Jeff

Select to expand quote

jirvin4505 said..


boardlady website

boardlady.com/repairmenu.htm

^^ she doesn't really show all the steps.

It would be a 3 page reply here....... but presuming some knowledge here's my main tips anyway:


Router - be accurate and take your time, you don't want any more than about 3mm bigger around the box, too much room = too much filler = too much heat = melted core foam.
Get your depth right and check often, you don't want the hole too deep, only about 3mm deeper than the box is

Use a super slow epoxy like West 209.

Sand the bejezzus out of the box with 40grit and clean well with acetone.

After making your big box hole, rebate out the bottom laminate around it about 30mm wider, and about 2mm deep. Then when you push the box in all buttered with filler, it has somewhere to flow to as a lot of excess comes out.
Put glass around the box also, and that then flops over into that rebate. It is the single biggest tip I reckon, as that makes a more watertight seal, if your cap of glass over the top separates from the edges of the box (many do) then the water still can't get in. Easier in pics...... here is my prep for a slot box install:



so as you can see the glass that wraps around/under the box can the lay over into the shallow rebate (this one is a bit deep if anything...). Then after all cured you can sand the top of the box well and cap it all with a few layers of glass

Mark thanks for info. Existing US box has crack down one side leaks but no movement. Yet..How do i remove old US box? Router it out? Its about twice the length of PB or Tuttle. How then do i know the CORRECT new fixed finbox position? What do i fill the void left from installing smaller length box with?

They are a bugger to remove if still bonded around most sides. I cut them out with angle grinder to salvage, best way is to do that all around maybe 1" bigger then the box, rip it out - muscles - and fill the whole thing with one big block of divinycell with resin / q-cell filler around it.. If you cant find divinycell, or wanna save the quids, you can get away with a block of Knauf foam from Bunnings (its just yellow XPS), about $25 for enough to 20 fin box installs.....
Then you have a nice big neat rectangle of d'cell to router a new hole in.

Position.... wherever your favourite fin pozzie was, just centre in that spot. ie: draft of old fin wherever you had it. I'd mark it first like my lines above are well away from the hole so you can't lose them later.... mark a centerline too before you start cutting

eg:


that is a bit bigger than it needs to be, the board was just screwed up by somebody's attempts to get the stuffed box out without a good cutting around the outside...

Last but not least , put fin in box for angle

I used a multi-tool like this.... works very well for finbox surgery.... as well as a host of other tasks.

I have done this job once fairly successfully

I agree with all of above by Mark. Make sure the new hole is not too much bigger than fin box and use slow hardener. It can be a bit of mucking around to get the depth correct, especially as most router bits will not go that deep. There are some router bits available that will go that deep (I have one that will cut about 80mm deep- can't think of brand). The inverse pattern following bits are just the best if you can be bothered spending the money (but won't go as deep as you probably need www.carbatec.com.au/pattern-bit)

The multitool is a great idea.

Routers are good, but can have a habit of grabbing. I clamped a few guides onto the board prior to routing out my busted fin box.

The chinook box I used had a big cavity in the top side of the box (see photo 2 in link below). (I filled this cavity up with foam and set it with resin and let it go off prior to inserting the box into the board.) The "slope" on the top of the fin box fitted the deck profile of my board very well. If the depth and "top slope" of the finbox does not match the slope of the deck, it is worth getting this sorted- cutting, sanding, shaping carefully. This will also dictate how it is finished on the deck/underside of the deck as the top of the screw sleeve (and hence the box around the screw) ideally needs to be flush with the deck.

Draw on some accurate guide lines for getting the fin in straight (and making the router cuts nice and straight) and make some off-sets of these to make sure they can still be seen when all the crap and tape is in the way.

Interesting that Eva Hollmann goes right through the board with the box and then seals from the deck side www.boardlady.com/jppowerbox.htm This would go a long way to minimising overheating of resin around box and some of the depth/profile issues mentioned above.

As Eva Hollmann says, use a nice long fin and measure accurately to the rails (prior to glassing in box) and tape it in place until the epoxy goes off.

Good quality blue masking tape (the $20 per roll stuff) is your best friend on these jobs.

Nice board by the way.

Good luck

Clarence