On this one the styro has compressed a bit and also has a crack across the damaged area. I was planning to rout down into the styro 6mm and glue in a 6mm piece of HD foam, then a thin layer of glass then another 6mm layer of HD foam and then the external skin.

Or should I try to get hold of some styro for the first layer?

Ok, I'll give it a go.

Piece of stiff plasic over the hole in the styro.
Inject expanding foam (proper 2pack not bunnings crap)

Then it will
- fill all the cracks and glue the styro back together (over quite some distance internally, as you are stopping it from escaping too much)
- fill the styro depression up to the right level

Does that stuff go hard or does it retain some softness (like the styro)?

Looking at these sort of repairs now, I wonder what I would do with that sort of damage.

I mean, I like cutting out finboxes and adding new ones, and adding new footstrap inserts. I have enough 'extra solid' boards to show for it, but with damage like that, I can't help but feel I would have just injected a little bit of resin into the cracks, plastered a bit of q-cell and epoxy mix into it, and maybe add a layer of glass or two over the top once it has hardened and been sanded back.

Are we getting too concerned about perfect repairs? It is a genuine question as I never seem to sell boards on, so I don't really see how cheap repairs compare against doing it perfect after it has been used for a while.

One of my first repairs was to a 5 cent hole in a carbon board where I just filled it with epoxy and filler, and it is still fine after a few years.

That looks nasty!! About 20 tubes of Marine epoxy putty should fix it though

P.S. Mine's fiber glassed, painted and ready for tomorrow's NE'r.

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2035 said..
That looks nasty!! About 20 tubes of Marine epoxy putty should fix it though

P.S. Mine's fiber glassed, painted and ready for tomorrow's NE'r.

Nice one! I have more work to do....

Used the router to cut out the bulk of the damaged styro and chop down the HD foam to just shave the glass layer in between. Also used the router to take off the surrounding paint and expose the glass beneath ready to overlap the new outer skin on to.

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FormulaNova said..
Looking at these sort of repairs now, I wonder what I would do with that sort of damage.
I mean, I like cutting out finboxes and adding new ones, and adding new footstrap inserts. I have enough 'extra solid' boards to show for it, but with damage like that, I can't help but feel I would have just injected a little bit of resin into the cracks, plastered a bit of q-cell and epoxy mix into it, and maybe add a layer of glass or two over the top once it has hardened and been sanded back.
Are we getting too concerned about perfect repairs? It is a genuine question as I never seem to sell boards on, so I don't really see how cheap repairs compare against doing it perfect after it has been used for a while.
One of my first repairs was to a 5 cent hole in a carbon board where I just filled it with epoxy and filler, and it is still fine after a few years.

The problem is sticking resin into styro where it may well overheat and melt the core.
Especially this time of year.

Do it in the evening with super slow hardener, may be OK.

Also it is heavier, decent cracks can take 50ml to 100ml (which means grams near enough) of resin and just puddle in the bottom so you added weight and only stuck some of the crack together.
An expanding foam weighs 25% of that, gets everywhere so stick hundreds of little cracks together, and duplicates the core strength rather well.
I am amazed how well a stryro core can be repaired with 2 pack polyurethane.


Is is kinda in between stryo and divinycell in density but confining it as it expands makes it denserer :)

But I do agree about do we really need 'perfect' repairs. If that hole is nowhere near the stressed rear half or 2/3 of the board, and/or it will never be jumped, fill and one layer of d'cell then glass would be perfectly fine

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Mark _australia said..
Piece of stiff plasic over the hole in the styro.
Inject expanding foam (proper 2pack not bunnings crap)

Then it will
- fill all the cracks and glue the styro back together (over quite some distance internally, as you are stopping it from escaping too much)
- fill the styro depression up to the right level

I haven't used the 2pak mark is talking about but I have found the bunning's expanding urethane ok for small repairs , on a repair like that with the Bunnings stuff I have found you will get trapped air bubbles , so what you need to do is as mark said use the plastic ,
with the Bunnings stuff you will need to run the foam around the edge of the cavity when it expands use a spatula and break it and it will deflate spread like spreading butter on a piece of bread , then as mark suggested use the plastic and inject some more foam
the reason for the first layer of foam is to make sure you don't get any trapped air around the perimeter of the repair and the foam will be a bit denser , with the Bunnings stuff you mite find you have some trapped air when you remove the plastic so just repeat, if your just doing a one off repair I cant see a problem with the cheap way out
you also need to know your product because a little bit goes a long way , and be careful injecting boards because you can do a lot of damage

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ikw777 said..
Used the router to cut out the bulk of the damaged styro and chop down the HD foam to just shave the glass layer in between. Also used the router to take off the surrounding paint and expose the glass beneath ready to overlap the new outer skinw on to.

If that was me i would
mix resin and qcell apply to eps, lay down layer of pvc as eps replacement,
apply more resin qcell onto this to fill any voids.
apply 1 layer of 4 oz and resin.
apply pvc and fill any voids with the qcell resin mix, then vac bag or weigh down with sand bag.
When dry sand to correct height and glass with 2 x layers 4 oz, let dry, fill coat with resin and qcell mix, let dry sand and paint.Might ad an extra 30gms but is quick, easy, strong and functional.
good luck and your prep work looks great so far.

Some more work getting done on this repair:

All ready for a big glue up tomorrow followed by routing down the big plug to the level of the EPS core. I'm lucky that this part of the board is very flat - makes it easy to use the router.

That looks like a bit of an over kill for a non stress part of the board.

Sand, lightweight Q-cell mix, glass, sand, Go sailing, drink beer.. would have been the better option.

Keep digging and you might make it to china.

IKW, you know MOB's pic of the super pit was not an instructional....?

if your going to do a job, might as well do it right..looking good there ikw.

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P.C_simpson said...
That looks like a bit of an over kill for a non stress part of the board.

Sand, lightweight Q-cell mix, glass, sand, Go sailing, drink beer.. would have been the better option.

Nothing is too good for this board. Best one i ever had.

Looking good Ian - there's nothing wrong with doing a great repair job, if you have the time knock yourself out !

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Mark _australia said..
IKW, you know MOB's pic of the super pit was not an instructional....?

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Mark _australia said..

The problem is sticking resin into styro where it may well overheat and melt the core.
Especially this time of year.

Do it in the evening with super slow hardener, may be OK.

<snip>

An expanding foam weighs 25% of that, gets everywhere so stick hundreds of little cracks together, and duplicates the core strength rather well.
I am amazed how well a stryro core can be repaired with 2 pack polyurethane.


Is is kinda in between stryo and divinycell in density but confining it as it expands makes it denserer :)

I would have just used the resin to seal the styro before then using the q-cell paste. I have found a brush layer of resin makes the q-cell mix adhere a little easier, but then again, when its styrofoam, adhesion means very little. I agree that a pool of resin would heat up, although I have only seen it 'thermal' when I have left too much of it mixed up in a cup.

I know about the 2 part pour foam. I posted up photos ages ago where I used it to re-adhere a delaminated bottom on a JP FSW by drilling bunches of holes and injecting syringes full of the foam. It worked really well except where I got too excited and used more shots of foam than the holes could handle in one place and it bowed out a bit. I needed something like 5 holes for expansion for each hole that the foam was injected into. If someone thinks you can't glue a skin back on, they haven't tried this, but filling the holes afterwards can be a bit tiring.

A few years later I cut the board up and widened it, and it was a good chance to see what the injected foam had actually done. It looked good. It was like a seam of yellow running through the styro and had stuck it all together really well. An excellent glue, and effectively water-proof.

I ended up coming up with a system where I would mix the foam, inject a few shots into the board, and then draw some acetone into the used syringe to clean it. I could then use the same syringes over and over again for the foam injection.

Will that 2 part urethane fix a delam?

Some more pics showing the styro core fully restored, glass cut out ready to go under the pvc foam and the pvc foam cut to shape. Another glue up tommoz.

I have another board you can practise on Ian

doing a great job.

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NotWal said..
Will that 2 part urethane fix a delam?

Yes, it will. depending on where the delamination has happened. If its the stryrofoam, it will glue it back together. If its the divinycell that has come apart from the fibreglass, I don't think it will get in there.

I repaired a delaminated board using this, but it required a lot of small holes, and a lot of work to fill it all once I was finished.

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FormulaNova said..

NotWal said..
Will that 2 part urethane fix a delam?

Yes, it will. depending on where the delamination has happened. If its the stryrofoam, it will glue it back together. If its the divinycell that has come apart from the fibreglass, I don't think it will get in there.

I repaired a delaminated board using this, but it required a lot of small holes, and a lot of work to fill it all once I was finished.

I have an old board with a huge bubble in front of the fin. It's certainly skin separation from the core and fractured styro. I was toying with the idea of injecting epoxy through lots of holes but 2 part styro would be more structurally consistent.

Do you think that drilling holes at say 70mm spacing in both directions and injecting 2 pot styro would be worth a try?

The idea is that I would first attempt to flatten the skin by mechanically compressing it and leaving it in a hot car for a day then drill the holes, inject the goo, compress it flat with short lengths of sticks and wipe off the goo that squeezes out, let it cure for a day or so then just epoxy fill the holes and sand and paint.

Does that sound viable?

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NotWal said..

FormulaNova said..

NotWal said..
Will that 2 part urethane fix a delam?

Yes, it will. depending on where the delamination has happened. If its the stryrofoam, it will glue it back together. If its the divinycell that has come apart from the fibreglass, I don't think it will get in there.

I repaired a delaminated board using this, but it required a lot of small holes, and a lot of work to fill it all once I was finished.

I have an old board with a huge bubble in front of the fin. It's certainly skin separation from the core and fractured styro. I was toying with the idea of injecting epoxy through lots of holes but 2 part styro would be more structurally consistent.

Do you think that drilling holes at say 70mm spacing in both directions and injecting 2 pot styro would be worth a try?

The idea is that I would first attempt to flatten the skin by mechanically compressing it and leaving it in a hot car for a day then drill the holes, inject the goo, compress it flat with short lengths of sticks and wipe off the goo that squeezes out, let it cure for a day or so then just epoxy fill the holes and sand and paint.

Does that sound viable?

What I found was that it worked well if you had a hole to inject the foam, and about 5 around it for the foam to come out of. They were much closer than you suggest at around 50mm distance at most, maybe even less. The idea is that the foam can escape instead of expanding and forming a bulge, and that the foam pours out of the hole you injected it into and the surrounding holes as well.

You only have a small amount of time once you mix the foam and draw it into the syringe, so I had a bunch of 5ml syringes and the holes I drilled were just the right diameter where the syringe is locked in. Once you have injected the foam, if you want to reuse the syringe, cycle some acetone through it to clean it.

Scrape off the foam that comes out as its easier to remove it than after it sets.

By the sounds of your problem, you could drill the holes first. I don't think heat is going to soften anything.

The two part urethane foam is called GP something, and is the same foam they used to build the original plastic skinned boards. One of the components (the darker of the two) seems to react with air or moisture and you will find it will stick the lid down, so if you can, find some way to store it where the lid comes of easily.