Way back in June, Ratz asked me to fix his delamed mistral. Hoping it was a case of the sandwich cleanly separating from the core, so it could just be restuck back down, I agreed. Routed around what seemed to be the limit of the delamination to find this.


Not a clean separation at all, bits of loose foam floating around, causing random compression of the core. There's no way this can go back together and be any good.

Interestingly you can see at the rear it has come away cleanly, mainly because of mini d'cell stringers stiffening the impact zone. You can see the broken, longer, centre one, the two shorter side ones are just peeking through.

So I'm sort of committed now, nothing for it but to recreate the bottom.

Had to remove more delaminated sandwich first, taking it almost to the rails. I wanted to use the rails to help stiffen the board while I worked on it, and as a guide to the original rocker line.
There seemed to be a constant 3mm "V" through the bottom, slightly concave through the middle and flat along the rails.

So the plan was to remove the damaged foam leaving a flat surface to rebuild from.
Trouble was I didn't have any foam wide or thick enough to do this in one piece, so I had to leave two flat surfaces at a slight angle to each other, to minimise depth of cut.

Then of course, I've never worked on an 800mm board before, all my aides are two small. So channelling Heath Robinson I came up with this.


Some ancient fibreglass battens for runners shimmed up to be straight, and a travelling router guide to slide over them.

So this is how the front bit looked after I'd removed the damage there.



After doing the same to the back half at a straighter angle, then came the jigsaw puzzle of fitting bits of new foam into the big hole.


The three sets of lines mark the position of the mini stringers. I'm going to extend them a bit in the hope that helps prevent a reoccurrence.

Next job is to shape the foam as close as I can to the original, then remove an even 3mm all round including into the existing sandwich, just above the underlying glass. So the new sandwich goes on flush, and ties in to the old bottom layer of glass.

Then fit new d'cell with vacuum bag and reshape.


A little bit of bogging needed before the top two layers of 4oz get vacuumed on top. You can see where I've sanded back into the board so the new cloth can overlap the old.
Then the usual, bogging sanding and painting.
But that's still to come, and Ratz is still waiting patiently.
So be warned anybody who's thinking of it, a delam fix by me can take an awful long time.

Geez Ratz - is that the board you got from me?

Any idea why it delaminated?

Nice work, Mike

JJ

Now that's a fix decrepit
No job to big.
Love it.

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azymuth said..
Geez Ratz - is that the board you got from me?

Any idea why it delaminated?

Nice work, Mike

JJ

My guess, and it's only a guess, is one too many ocean nautical miles

Hey Great job mike, it looks very neat or are you just putting up your best picks did you know you can buy small sheets if variious thickness EPS from Clarke rubber, thats wher I got mine from when I did a similar repair www.seabreeze.com.au/forums/Windsurfing/Wave-sailing/Whats-Mike-up-to-now?page=1 Your delam looked like it went pretty deep, what length and width router bit did you use?

For the deep stuff I used the largest drill bit that would fit in the router chuck, (long router bits are soo expensive) 3/8inch I think. As the foam is so soft I reckoned I could get away with it. Wouldn't want to do that with a harder material.
No didn't know Clark rubber sold eps, good tip Mike.
Yes it was deep, getting close to 50mm in places.

OK, just checked and it was a 3/8" or 9.5mm drill resharpened with a flat end.



Still in the 1/2 inch adaptor. One of these days I'll invest in a 1/2 drill bit.

yeah j.j same one
i put the damage down to a fair bit of ocean sailing
and also beating back up wind in to our lovely australind chop.
i am not really a light handed sailor either so she has had a rough life.
thanks to mike for taking the project on
would have been sad to lose her.

Thanks Mike , I wish I had have bought a half inch router, long 6mm bits break easily if I go too fast. I blunt 6mm file drill bits I get from SCA they're only a few dollars.

JJ, Ratz.
The goretex vent is also under a bit of a cloud. A while ago I tested one, with water on the outside it breathed out but not in. But with water on the inside it breathed in but not out! This board had a repair to the fin box, so there is a possibility that there was some water inside. I haven't seen any sign of water, and I removed the vent and could blow through it OK. BUT--------
I wouldn't recommend using goretex vents.

I agree Mike, I pull the goretex vent out of my M91 regularly, suck and blow it (), but can't really tell if it's working.
It's a potentially costly gamble.

I've been looking for a screw-in solid plastic plug that fits the goretex housing - no luck yet.

Make sure you don't blow any spit onto the inside!

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azymuth said..
I agree Mike, I pull the goretex vent out of my M91 regularly, suck and blow it (), but can't really tell if it's working.
It's a potentially costly gamble.

I've been looking for a screw-in solid plastic plug that fits the goretex housing - no luck yet.

Nylon bolts from Bunnings fit my Carbon Art. Is the Mistral a different thread

yeah i think thats the go rob.

The mistral and carbon art have the same goretex vent, so the bunnings bolts should work.

Just pulled the board out of the vacuum bag, with the last two layers of 4oz on top of the sandwich. Going to be busy again tomorrow, but may get a chance to put some bog on.

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decrepit said..
JJ, Ratz.
The goretex vent is also under a bit of a cloud. A while ago I tested one, with water on the outside it breathed out but not in. But with water on the inside it breathed in but not out! This board had a repair to the fin box, so there is a possibility that there was some water inside. I haven't seen any sign of water, and I removed the vent and could blow through it OK. BUT--------
I wouldn't recommend using goretex vents.

Totally agree Decrepit, I dont recommend using Goretex vents on our windsurf boards. A standard SS 10 g 15mm self tapper screw into a Chinook insert with no O ring has served us well over the last 29 years of epoxy board building with Zero delamination issues. I tell customers to screw them in and LEAVE them there, only to remove them only if you are travelling on an air plane, due to differant air pressures at altitude.
The goretex menbrane is not 100% waterproof, so once you put a hot board from your car into cold water ,this causes a vacuum inside the board ,as the styro foam beads contract, This, then draws a very small amount of moisture into the core, which then get repeated again and again over time. Along come's a super hot day, which we get occurring here in Australia over summer , this then built up moisture then steams up and expands the air in between these large styro beads [Asian Molded styrofoam blanks] quicker then the Goxtex can vent the air pressure inside the board, resulting in the repair delamination you , Decrepit are needing to do now.

Thanks for the advice OES, Mike, Ratz and Stretch - I'll head to Bunnings and buy a nylon bolt, one less thing to worry about

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azymuth said..
Thanks for the advice OES, Mike, Ratz and Stretch - I'll head to Bunnings and buy a nylon bolt, one less thing to worry about

what exactly are the nylon bolts to get?
I am presuming you screw out the goretex vent and put one of the nylon bolts in?

So have I been doing it wrong all this time. I normally screw in a standard plug into my boards before going into the water and then once they are dry I tend to back off the screw a little to let air in/out when they are stored in my van. I regularly change the O rings. Won't the board delaminate if it is sitting in a hot car day in day out with the screw in.

^ Yes if it has any water in it, and you wont necessarily know if it has until it blows up.

Yep, there's no guarantee either way, it may blow it may not

Dunno why we need to get fancy.
Goretex was a great idea, proven to not work.
Some boards with no vent did blow up in hot cars. OES ones haven't as they are made well, and having looked at the lack of care / resin / commonsense in mass produced boards, I would rather play it safe and simple with mass produced boards.

ie:
Use the garden variety Cobra style plug with o-ring and open it when not on the water.
Change the o-ring yearly.

Oh yeah and with new boards stick a long nail down its flooter, cos I found a couple that were not drilled out..... there is no point opening the vent if the factory never drilled thru to pure white styro after installation!!!!

Simple and works.