Mast Track Replacement advice needed

[SupScott]

Hi!
the mast track on my Shinn Nubo wing board has started disintegrating and I'm looking for advice on layup schedule when replacing it. Not many local suppliers so I'm limited to 6oz twill weave carbon, 6oz glass, and 4oz glass. Is 3 layers of CF and 1 layer of 4oz glass (on top) enough or should I go 4 layers of carbon and 1 glass?
Also, I planned to extend the cloth to 10cm beyond the PVC foam in both directions but I've only 5cm of board at the front due to the handle recess in the hull. Do I need to be concerned about that? Should I extend the cloth in front of the handle recess?

Thanks, Scott

[finbox]

Here is how SUP SURF MACHINES does boxes - https://www.standupzone.com/forum/index.php/topic,38336.msg439152.html#msg439152
The business is closed - the "cassette" ties the top and bottom skin of the board together so you don't just lever on the bottom skin. It looks like the board is carbon - so use carbon with glass for the final surface of sanding and finish.

[SupScott]

Thanks Finbox. I've already bought the mast tracks & pvc foam cartridge. I figure the board already has re-inforcements of some sort to the deck, or I would have had other problems before now. I just need to route out existing cartridge to the depth of my replacement and fix my new one with Gorilla Glue. I'll review if I don't find any HD foam in there already!
Should I laminate over the carry handle aswell as its so close to the existing tracks? Only 5cm from handle to front of cartridge, 8cm from handle to front of tracks.

Thanks

[finbox]

Hi,
I would think that laminating past the handle is a good idea - if you can wrap fiberglass under the boxes and on to the deck that could help them from crushing into the foam. you can fill he hole with gorilla glue then route our the box shape. That way you don't have to worry about the foam melting.
Good luck

[SupScott]

There's already green high density foam in situ, with a small 2cm strip of EPS exposed. See attached image. Were you recommending the cloth wrap around the boxes if I was replacing only the fin boxes? Is it still recommended when replacing the full cartridge? I've seen someone do that before.
It looks like I can fix the cartridge in with just Gorilla Glue now. Or will the cloth wrap give me a better bond?
Thanks

[finbox]

Hi,
This may be too late but - You can just gorilla glue the foam cassette in - the issues that were found is that the levering action of the mast on the tracks and lots of cycles of that typically result in the high density foam crushing under the box and then the box delaminates from the bottom surface skin of the board and leaks. Kings Boards uses a wood stringer to distribute the force from the box into a wood stringer then into the board skins with the foam keeping the wood stringer in plane and not buckling- see photo of the stringers next to the boxes.
https://www.standupzone.com/forum/index.php?action=dlattach;attach=112507;image the start of the post https://www.standupzone.com/forum/index.php/topic,38271.0.html
If you just use the high density foam cassette you can wrap under the box to support the bottom of the box so it won't push into the foam from the lever action of the mast- by wrapping under the box with a layer of fiberglass cloth when you set and laminate the boxes into the high density foam and tie it into the bottom skin of the board.

[SupScott]

Ah, ok. I get it now, albeit too late. Thanks for explaining in depth. I might get away with it for a while as I don't get out very often (only 25x last year). Will carry on.

One last thing I'm still unsure of is the height of the track boxes. They sit proud of the foam cassette. Am I right in saying I tape over the opening before laminating over the top, then grind away the extra height (inc the tape) after curing? It seems to me that if I make it level first and then laminate, the cloth will be adhered to some of the tape.
For the fill coat, I again tape over the opening but remove when the resin is tacky? This will leave a slight gap between edge of the opening and where the resin ends, depending on my accuracy cutting the tape.

Thanks again.

[finbox]

Hi,
The boxes you have are Future Fin Boxes. They have the wider flange - thats good. See the video's on how they are designed to be used. Lamination & Hot coat - https://www.youtube.com/@futuresfins/videos is the main video page, scroll down to 8 years ago and watch a few on how they think it should be done.
Then do what seems to be easiest. Just make sure to get glass to bond to the flange of the box.

[SupScott]

Thanks for that, I was on the right track 

However, I was a bit early saying last question... I managed to make the cassette recess slightly too deep. I poured in 4lb PU foam and sanded it back to the correct level but it feels too soft. Almost spongy.

I think I should sand it all back and use thickened epoxy to fix the level. I already have cabosil I could use or should I use micro balloons? Or both? Next dilemma is to apply below or above the cassette?

I know this isn't standard but appreciate any advice

Thanks

[finbox]

So the big rectangle hole is too deep? If it is 1/8 or less too deep you can set the foam block with the boxes in place using gorilla glue. The gorilla glue will foam up to fill any voids and it won't melt the EPS foam, like epoxy can. It will bond the new block of foam in place. hit the gorilla glue with a spritz of water to help it kick.

[SupScott]

I did the lamination but I didn't get the 1st layer of cloth tight to fin boxes. Now that I've levelled the boxes, both now showing cavities around the edge, mostly to the tail end. Is it a complete failure or just needs some remedial action? Any suggestions?
My best plan is to expose the gaps with a dremel and then over-pack with resin & chopped carbon strands. Can vac-bag again or clamp into place.
The woes of being inexperienced!!

Thanks.

[SupScott]

Thought I'd close this off with pics of the final result and a report that the first test-run was a total success! Thanks for help @finbox

Would need a proper vacuum setup if I did it again 

[finbox]

Looks good - it is difficult to vacuum bag repairs and keep them straight and not crush the foam. You did a better job than many commercial repairs- Tim