My favourite 48cm speed board has reached the end of it's use by date, wobbly bottom and delamned under the mast track.
I've done a quick repair hopefully to last until I get the new one on the water.
I pick up the blank from future foams in Jandakot tomorrow, so next job is to organise 2 rocker templates to hot wire it.

And Ratz has given me a mistral 55 with a detached bottom to put back together.
So far I've made the fin box for the 48 and I'm recording the bottom shape of Hardy's 55. I have it in mind, that if I clean up the old bottom, I can recreate the shape with new foam, less 3mm and stick the old bottom back on.

Not sure how I'll go doing these concurrently, there's not much room in my shaping bay. But while my board is in the vacuum bag, I can work on the Mistral.

Pics as I go

Only 2 new projects!!!!! You'd better lift ya game

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kato said..
Only 2 new projects!!!!! You'd better lift ya game

Well I have been re-stumping the shed, organising a sewerage connection for the rental property, and trying to figure out how to use a Pi zero and a u-blox chip to make a data logger.

Yes. I have my list of projects. It is long enough, but the one my lovely wife has for me is much, much longer. No idea why......

I think you will find mine is a 91 slalom mike.
I havnt managed to delam my 55 yet.

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ratz said..
I think you will find mine is a 91 slalom mike.
I havnt managed to delam my 55 yet.

Well maybe that explains the difference between yours and Joe's. But I hope you don't mind if you end up with a 55 style bottom.

Interesting development today, I picked up the block from Future Foams, and they rate this foam as closed cell!
He reckons it doesn't soak up water, so that will be my first test, if it's right this board won't have a bung.
But I have my doubts, a little bit later he was telling me I had the wrong grade foam, the 13kg stuff doesn't shape because the beads are too big and it falls apart, the 28kg stuff is what you need if you want to shape it.
So tomorrow I hope to find out he's right on the first point and wrong on the second.

Sounds like he is assuming surfboards where many people use 28kg (VH)
Of course that 28kg stuff does shape nicer compared to 16kg (SL) used in a windsurf board or SUP, but we don't need a fine finish for clear glass over.
My last board in 28kg was done totally with a surform and the block work with sandpaper was literally a 5min quick run over. I could have glassed straight over the surform finish if painting the board. It shapes that well.
Of course that would not have been the best glassing bond, just saying it would be kinda possible...


What colour is it - cos no XPS is white....?

the stuff I've bought is white and eps, that's why I doubt it's closed cell in the sense we mean. He said, "well it's made with closed cell beads"
I said, "what about the gaps between the beads". He said, "well we sell it as a flotation device"

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decrepit said..
the stuff I've bought is white and eps, that's why I doubt it's closed cell in the sense we mean. He said, "well it's made with closed cell beads"
I said, "what about the gaps between the beads". He said, "well we sell it as a flotation device"

I doubt it will be water proof. Can we have some pics please?

Hi Mike i have another bottom delam for you. My vacum pump has died so i cant do it. No rush. Let me know if you have time for another.

So rocker templates pined to the blank, ready for hot wiring.

Mike as soon as I cut through the hotwire melt, I'll post a pic of the cell structure. so far it behaves like standard EPS




You can probably see the rocker template id made from plywood. This is far from ideal, the wire gets caught in the grain. My next pics will show the result. Masonite gives a better result, but I didn't have much of that lying around.

no mike i dont mind
will just be happy when it has a bottom on it.

Oooooh nice..... another build!!! SUBSCRIBED!

Is it going to be an exact copy of your old board or are you making minor changes or completely different.
Lunny is the man for bum repairs on mistrals, he has done two recently and they look and work great.

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Swindy said..
Is it going to be an exact copy of your old board or are you making minor changes or completely different.
Lunny is the man for bum repairs on mistrals, he has done two recently and they look and work great.

Yep, sailed with Lunny the other day, his repaired Mistral looks great, and he's had a couple of PBs on it, so it still works very well.

I was getting around to deign changes, yes there will be a few.

As I've acquired a flat water addiction, I've been thinking of optimising the bottom for flat water.
The old board has a 3mm V over the whole bottom. This helps in chop, but I think looses lift to drag ratio, and in flat water isn't necessary.

So when I checked Joe's board and found a very reduced V under the feet, I was convinced this is the way to go.
So I'll keep V forward and behind the back strap, but between the feet it'll be fairly flat.
May also try slowy's twin concaves, although I'm a bit loath to copy stuff I don't completely understand, It;s very easy to get it wrong when you do that.

I'll also make the nose a bit narrower to reduce radial inertia and maybe make the board gybe easier.

More pics more pics.... we need boardporn!!

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Dar said..
More pics more pics.... we need boardporn!!

So first thing was to test the highly unlikely claim of closed cell. here's an off cut, sanded with a 60grit hand pad, then a hollow put in with an 80 grit right angle grinder.



So it shapes OK, this is the sort of reult I expect from 13kg/m3 foam after coarse sanding, wrong on one point.

Then I mixed some red water based paint and filled the indent.






About an hour later most of the water had soaked in, so I snapped the foam across the red area.




so it's soaked right through and left a big red puddle on the bench, as you'd expect.

So on to some real work and start to play around with the outline.



The back is the same as the old one, I'm happy with that, but I experimented with different nose widths.
Call me old school, but I don't design on a computer, not even paper, I much prefer doing it directly on the blank.
I've ended up with neither of these, it's come out narrower than both, later pics will show that.

Next was to get the jig saw out, but even with the longest blade I have, it doesn't cut all the way through, so I have to finish off with a hand saw.


To finish off the day I've glued some real closed cell EXPS blue foam where the fin box will go.
More pics later

Fantastic!! Keep it coming. Thanks.

This part is the fun part . Max 4 beers.??

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decrepit said..

Dar said..
More pics more pics.... we need boardporn!!

So first thing was to test the highly unlikely claim of closed cell. here's an off cut, sanded with a 60grit hand pad, then a hollow put in with an 80 grit right angle grinder.



So it shapes OK, this is the sort of reult I expect from 13kg/m3 foam after coarse sanding, wrong on one point.

Then I mixed some red water based paint and filled the indent.






About an hour later most of the water had soaked in, so I snapped the foam across the red area.




so it's soaked right through and left a big red puddle on the bench, as you'd expect.

So on to some real work and start to play around with the outline.



The back is the same as the old one, I'm happy with that, but I experimented with different nose widths.
Call me old school, but I don't design on a computer, not even paper, I much prefer doing it directly on the blank.
I've ended up with neither of these, it's come out narrower than both, later pics will show that.

Next was to get the jig saw out, but even with the longest blade I have, it doesn't cut all the way through, so I have to finish off with a hand saw.


To finish off the day I've glued some real closed cell EXPS blue foam where the fin box will go.
More pics later

Has anyone tried just glassing over the foam as in the last pic without any further shaping? I wonder how it would sail?

Careful decrepit , I see patent issues

Yes it is amazing what a random blob can look like.

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dchoco said..

Has anyone tried just glassing over the foam as in the last pic without any further shaping? I wonder how it would sail?

Go for it !!!

Select to expand quote

choco said..

decrepit said..

Dar said..
More pics more pics.... we need boardporn!!

So first thing was to test the highly unlikely claim of closed cell. here's an off cut, sanded with a 60grit hand pad, then a hollow put in with an 80 grit right angle grinder.



So it shapes OK, this is the sort of reult I expect from 13kg/m3 foam after coarse sanding, wrong on one point.

Then I mixed some red water based paint and filled the indent.






About an hour later most of the water had soaked in, so I snapped the foam across the red area.




so it's soaked right through and left a big red puddle on the bench, as you'd expect.

So on to some real work and start to play around with the outline.



The back is the same as the old one, I'm happy with that, but I experimented with different nose widths.
Call me old school, but I don't design on a computer, not even paper, I much prefer doing it directly on the blank.
I've ended up with neither of these, it's come out narrower than both, later pics will show that.

Next was to get the jig saw out, but even with the longest blade I have, it doesn't cut all the way through, so I have to finish off with a hand saw.


To finish off the day I've glued some real closed cell EXPS blue foam where the fin box will go.
More pics later

Has anyone tried just glassing over the foam as in the last pic without any further shaping? I wonder how it would sail?

Ask the Windsurfer LT guys

Select to expand quote

decrepit said..

Dar said..
More pics more pics.... we need boardporn!!

So first thing was to test the highly unlikely claim of closed cell. here's an off cut, sanded with a 60grit hand pad, then a hollow put in with an 80 grit right angle grinder.



So it shapes OK, this is the sort of reult I expect from 13kg/m3 foam after coarse sanding, wrong on one point.

Then I mixed some red water based paint and filled the indent.






About an hour later most of the water had soaked in, so I snapped the foam across the red area.




so it's soaked right through and left a big red puddle on the bench, as you'd expect.

So on to some real work and start to play around with the outline.



The back is the same as the old one, I'm happy with that, but I experimented with different nose widths.
Call me old school, but I don't design on a computer, not even paper, I much prefer doing it directly on the blank.
I've ended up with neither of these, it's come out narrower than both, later pics will show that.

Next was to get the jig saw out, but even with the longest blade I have, it doesn't cut all the way through, so I have to finish off with a hand saw.


To finish off the day I've glued some real closed cell EXPS blue foam where the fin box will go.
More pics later

Thanks for the pics

Yesterday I had to improve the level (woops, straightness) of my work bench. The board is too flexi at the moment to work on the shaping trestles. So I've used the deck hot wired off cuts to support the board on a nice flat bench.



After that I routed out for this 9mm 70kg/m3 high density foam finbox support, and stuck it in with 200gm carbon. Underneath is an insert of 35kg/m3 closed cell extruded styrene.

The old board developed a crack around the front of the fin box. I put this down to the fin box being solid as it's tied in to the deck, but the bottom can flex a small amount, and epoxy doesn't stick real well to the plastic box,

So here both the blue foam and the 70kg stuff extend in front of the box, and should support the bottom sandwich. I've also made my own box out of the same 9mm high density foam and carbon. So there should be a better bond to the box.

Of course this left the shaping bay free, so Ratz's board got a look in.

I started off cleaning up the old bottom.



I noticed something very interesting, the orange stuff appears to be the resin used to stick sandwich on. But it has soaked way in, in fact that's where the foam has failed, right on the boundary of the resins penetration.
No dry wet out problem here!!!!!!!

After I finished cleaning I noticed some failures of the stringer.





So the question now is what to do about the stringer?

I think I'll delete it and use carbon to stick the sandwich back down.

I then routed out the big hole the stringer left behind.




At the top of the hole I've made you can still see some orange resin left behind.
At the moment epoxy is setting around the block waiting to go in. So next I can route out the rest of the rough stuff and figure out how I'm going to fill the big hole in.

Then I got back to my board, marked out the "V" on rails and shaped them down.
Made up my mind to try out slowy's twin concaves, so marked them out, and sanded them down a bit.


(So this is how the nose ended up, I'm rather pleased with it.)
These need feeler gauges to get right, and the foam is too soft to use feeler gauges with, So I'll wait until the divinycell is on. Woops not divinycell, apparently that's now too hard to get hold of in WA, I'm now using GURIT 80kg/m3 pvc foam, properties seem about the same, it comes in smaller sheets, but looks to have finer cells.

A day off tomorrow, so may get it on Sunday arvo.

Didn't quite make it, was too late to mix resin by the time I had everything ready.

first of, thought I'd check the claim that Gurit has a finer cell structure than divinycell.


so clockwise from top, we have divinycell, old divinycell, corecell, herex and gurit, so I'm sure the claim is valid.

So I can use my side lights to check the concave "Vs", I put a couple of planks between my shaping trestles, rested the blank off cuts on them then plonked the board on top.

Shows up a couple of spots where I was too vigorous, and drages some cells out of the foam.






Next I made a template out of an old newspaper, marked and cut the foam and glass.
before I cut the glass I tape just outside my mark, then cut through the tape.
I wet the glass out on the bench, and roll it up on a pvc tube. The tape stops frayed strands that stick to the bench pulling the cloth when rolling.



Next I mark the centre line on the glass, it helps orient the cloth when unrolling onto the board.

Stuffed up a little bit though. I was going to keep an exact record of weights through the stages so I can calculate the volume accurately

I weighed the board after i'd hotwired it and cleaned up the rails, but now I can't find any record of it. I'm sure I wrote it down somewhere!

So I've had to try an calculate how much extra weight I've added with the tail reinforcing. I make that 124gms, as the board now weighs 1.29Kg
that makes the eps 1.166Kg. So in it's present state it's aprox 88l
I thought it was more than that, 1.186 rings a bell, that would make it 89.7l but I'll never know for sure now. I guess 2l is neither here or there.

I also weighed the PVC, that's 260gm, which means 3.25l,

Got the bottom on and in the bag this morning.


Well in two bags actually. I'm trying this to prevent squeezed out resin being left in the bag, later puncturing it.
So I've used an old leaky bag inside a nice new one. The old one is folded over the nose, to make it easier to get inside the new one.

So the shaping bay became empty again and Ratz,s board had some more progress.







Set up pieces of timber either side of the board as rails for the router carrier to run on. Decided to split the area in two, a large middle - rear area where it's fairly flat and a small nose area where the main rocker is.

Didn't come out quite as well as I hoped, I think the rail must have slipped on the nose area where it meets the middle area, it's going to need a bit of bog.



Now I've got to decide on the foam to fill it. I was thinking the offcuts from my board would do, but they are only 500 wide, this area is around 560. So I might have to cut into my big block of 24kg wave board foam. Probably not a bad idea as it will give the bottom a bit more support, especially if I get rid of that stringer thing.

Nice thread decrepit

My lastest is bit smaller - 5'3" and to be about 21-23L

First thought though- the bloke at the foam place needs the sack.

both projects looking sweet mike...