Just as a matter of interest what sort of layup is suitable for a hollow board?

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NotWal said..
Just as a matter of interest what sort of layup is suitable for a hollow board?

A strong one!!!!

The only one I've seen used a pvc/glass frame supporting the external pvc/glass sandwich. But I don't know what sort of layup it had, didn't turn out any lighter than conventional construction.

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Dar said..
Hi Rider

What weight carbon, 200gsm?

Slalom or wave board?

Have you found it to be very stiff?

200gm 95l waveboard not stiff as the deep mid concave and vee in the tail help keep the ride soft.

Not much action in my shed, not only have I been distracted by the raspberry pi GPS project, I bounced out of the harness on Wednesday at 35kts and managed to ping something in my back. So I took things very easy for a while, just playing on the computer, trying to connect to the pi.
Back has come really good, so after getting a pi-computer connection this arvo, I thought I better spend some time with my board project.
So took the sand paper to the rough rails where I couldn't squeegee the folds out. Then I had a small amount of bogging to do to fill the holes I'd left.
sorry pic is blurry, must have moved when I pressed the button. But believe me the rails are now nice and smooth, ready for the top glass.
Won't happen tomorrow, there's wind forecast!

So a bit more progress.

Using the template, I cut out breather, peel ply and cloth



because the template was for the PVC, and the cloth overlaps the bottom by a couple of centimeters I'm cutting everything out that much bigger.


Here I'm organising the breather to fit into the well.


I did the same thing with the bottom glass as I did the deck, 2 layers of 4oz cut across the meter wide cloth. With centerline and cross lines at the PVC joins.
Next job is to use yet more masking tape around the edge of the overlap routing. 3 runs gave me enough width, I don't like using newspaper like I do for spraying, as the resin can soak through the paper and stick to the board.
This time I just had to use the slow resin, so I kept it indoors overnight, (21c min inside, 13c min in the shed). Mixed the resin about 0930. After I had the first layer roughly on the board, I wet out the second layer and carbon reinforcing. This meant I didn't have a lot of resin in the tub heating up. I had the board in the bag about 2 hours later, and the resin was nice and runny the whole time.
The vacuum bag was holding fairly well, (the pump cycle was on for 6s off for 3m). At 2200 the resin was a thick treacle. So I was confident it was OK to turn the pump off.
Next morning, the resin was still too soft to remove the peel ply, so I stuck it in the sun while I had breakfast.



Still soft after breakfast, so I drilled a hole where the bung will go, wrapped it in black plastic and put back in the sun.

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With a free workbench I took the opportunity to progress Rat's board.

I hotwired the biggest section of foam from my block to fit in the big gap.



Using a straight edge salvaged from old blinds, supported on nails pushed into block and held in place with masking tape. I ended up with a piece of foam the right thickness to cut to shape. I'll use the old bottom sandwich as a template.

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After lunch I thought the resin on the board was hard enough to cut the rail overlap out. I lift the tape up to the glass then use a sharp blade to trim the excess cloth off. If everything is right it only needs a small amount of bog to smooth it out.

Once I had the peelply peeled off I weighed it.






You can see a misalignment between my lines, this was mainly the top layer, that's much harder to move about.
This time I've got more carbon around the well, so hopefully this board will last a bit longer.

And The problem I had with the bottom cloth sliding around, didn't happen on the deck. The slow araldite was sticky enough when first mixed and stayed that way for a few hours. The smelly black stuff I used on the bottom had no stick when first mixed, for about 15m then went like treacle fairly quickly and was much too sticky.
So it's got nothing to do with the gurit foam it's the ancient donated resin.

More to both boards today, got the fin box in mine and the largest bit of replacement foam in Ratz's
To create the hole for the fin box I use a router, as opposed to drilling holes and using a saw of some sort.




Routing directly on a "V" will give a wider hole on the opposite side, so I support the router on a couple of strips of ply wood I tape in place.
I start of with a standard bit to go through the tough sandwich. But it's a long way through the board, and standard router blades aren't long enough. So I grind the tip of a drill bit. It works fine in soft foam, but the sides of drill bits aren't really meant for cutting, so not a good idea to use on anything harder.

After mixing some stiff bog, thick enough so it doesn't run, but so thick I can't move it around, to adjust the box angle.

Checking the angle on a "V" bottom against a tapered fin is problematic, but I use this method.




So not 100% perfect, but it's probably close enough.

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After that another go at Ratz's board. I used the template to mark out the previously hot wired foam. And cut that to size with a jigsaw. But I had trouble getting it to fit, the rails have closed in a bit and the old bottom is a very tight fit. I had to sand a few mms off the sides, to get it in.

Stuck it in with bog and weighted down.




I ran out of weights, but I think that will hold it. I've supported the deck under the weights to prevent distortion.

I made an interesting discovery when I broke the old stringer off, so I could check the fit of the old bottom.



The foam inside the brown bog is the 5mm mistral stringer, the top 3mm foam is my new Gurit. Looks like the same stuff to me.

And to answer Rider's earlier question, the glass on the stringer only goes half way down.

Good to know the resin sticks well to the Gurit

Marked out the mast box and footstrap plug holes.


It's very hard to see marks on carbon, so yet more masking tape solves the problem. And yep, that's the current weight with finbox in.
The mast track and plugs will push it into the low 4s

I mixed a bog that just runs, so I can push the tack and plugs all the way in, but not so runny, it goes every where.

I'm trying the double screw set up for the front straps, so they don't twist on me. I'll make a broad single strap for the back.

Interesting that you put these in at this stage. Is it so you can wrap in glass and make more water tight or easier to locate and drill out holes if under carbon?

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R1DER said..
Interesting that you put these in at this stage. Is it so you can wrap in glass and make more water tight or easier to locate and drill out holes if under carbon?

It's the way I've always done it.
On my speed boards, to save weight, I didn't use xeps inserts I just wraped glass up onto the deck, to try and give it some waterproofing and strength.
But on the last board I had a couple done this way fail, splitting the glass and letting a lot of water into the board. On my old wave boards with xeps inserts and no glass wrap, I haven't had a problem.

And you're right with the carbon going off inside the vacuum bag it's very hard to find the holes after woulds. It's easy enough when the resin is still soft to probe with a fine point and cut the holes out.
This could be done before it goes into the bag.
My thinking was, that the sandwich is giving the plug sideways support, so I like the full sandwich up against the side of the plug.
Next step is a couple of layers of cloth over them to hold them in.

But now you have me thinking!!!!!!

It's probably more important to secure the plugs vertically than horizontally, so under the carbon would save the weight of the extra cloth on top.
Not sure about fin box and mast track though.

Sorry Rob another stuff up, getting a bit too many on these two projects.



Before I tried to fit the front piece of foam, I decided to cut the excess off the rear section. Should have used the hot wire with a guide. But I grabbed the hand saw instead. The entry and exit points where fine, so I got a nasty shock when I saw this. The saw decided to take on a concave bend, so those gouges aare 5mm deep at the worst points.
So my plan to use the rails as a guide to recreate the bottom shape is out the window!
I'll be able to do that with the starboard side and front but the rear port section will have to be done 3mm down.

I'll get the rocker at the center line correct, then use my router support to bridge between center line an rails. This will give me a straight "V". I'll then have to shape the concaves.

Wish me luck!!

Looks like such a crappy job to fix a delammed bottom....

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decrepit said..

I'm trying the double screw set up for the front straps, so they don't twist on me. I'll make a broad single strap for the back.

Well worth doing. On the boards that I have renovated I have put in the whole 5 hole chinook block and twisting straps are a thing of the past. So much so that I get a surprise when I use another board and they twist!

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Dar said..
Looks like such a crappy job to fix a delammed bottom....

Well it's easier than building a new board from scratch, but not much.

That is why I am so grateful that mike is having a go at it for me.
would be a shame to throw a board like that away.
he richly deserves the title of legend....

great posts guys, thanks for passing on your knowledge, its been great reading.
I'll never do what you are up to, but have picked up a few tricks that might serve in another way.

Have got the last small glass and carbon pieces over the inserts, and started bogging the bottom.
While I was waiting for stuff to go off I worked on the rear footstrap, tried something a bit different this.
I laminated some foam I bought for boom grip over a shaped piece of foam, to try and create a pre-curved shape.



Here, I've already got 3 layers of 2mm varying densities of foam laminated, the heaviest on the outside With a piece of pool tile foam waiting to go on last. I've shaped this with an angle grinder to be thinner and rounded at the edges. (on the opposite side to that showing)




Here weights are holding it in shape while the contact cement cures. And I've added two webbing straps to take the loads.



I'm very surprised by how stiff this ended up, it's never going to sag or twist

Just waiting for Hardie to return my soldering iron so I can melt some holes in it

This strap is about 1/4 the weight of conventional straps and doesn't soak up water.
And going by my previous efforts will outlast them. The blue foam is quite soft and comfortable, but I have to admit to only ever using booties with them.

Great construction ideas Mike.

It a pity that no one makes a wide rear strap commericially anymore (that I can find anyhow). Luckily. I have a couple of spares left over from the early 90's. I am now tempted to follow your lead and make a better one though.

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sailquik said..
Great construction ideas Mike.
I am now tempted to follow your lead and make a better one though.

It should be on the water next week, (if we have wind) I'll let you know how it performs.
Although, I could fit it to the old one and try in the next couple of days. If I'm twiddling my thumbs with nothing to do, maybe it'll happen.

I've got the first coats of bog on the board now, a sand tomorrow, and more bog to fill low spots.

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sailquik said..
Great construction ideas Mike.

It a pity that no one makes a wide rear strap commericially anymore (that I can find anyhow). Luckily. I have a couple of spares left over from the early 90's. I am now tempted to follow your lead and make a better one though.

Kowalski does! The best straps imho, I use them on all of my boards (slalom).

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CRO169 said..

sailquik said..
Great construction ideas Mike.

It a pity that no one makes a wide rear strap commericially anymore (that I can find anyhow). Luckily. I have a couple of spares left over from the early 90's. I am now tempted to follow your lead and make a better one though.

Kowalski does! The best straps imho, I use them on all of my boards (slalom).

Got a link?
Are they available locally?

Did a search. Nothing found except some pics of normal narrow straps. Link??

The ones I want are double width of a normal strap, to use where you would have two side by side on a narrow speed board for the back foot. They are not just a slightly wider normal single strap.

DA Kine used to make them but no more. I still have some old Gaastra ones from the late 80's.

I realized from this photo that my size 12 foot happily sits through the two singles straps on my kode 94. I think the straps are separated by at least a couple of inches at the screws.

Great build. Just a tip for getting the bag to form in the mast track well, use clothes pegs or bulldog clips to gather up excess bag into the well and make a long dog ear along the centreline of the board and one across the board at middle of well befor you pull vacuum. Then when vac comes on thrre is bag in the well ready to pull into the well corners then pull off clips as the bag pulls into corners. This is kind of how you have to bag in a female mould, the bag has to drape in the mould but then its too long to match the mould flange, so you make a dog ear by pulling a pleat up and tacky taping the bag to itself. basically you want loose material and t he bag will suck the excess to itself and make pleats or dog ears sticking up.

Thanks Piv, that should work better than my idea.

Kowalski footstraps, I have them also, the best light straps
www.facebook.com/kovalski.footstraps?ref=br_rs
www.den-8.dk/new-footstraps

we've had wind here and I have a flue jab cold, so progress has been slow, but I've managed to get some spray putty on and the first coat of white on the bottom.



You can see how the V fades out under the feet. and comes back at the tail. The slight concaves are also visible. I just hope they work as well as they do on the slowy designed mistrals.

I was about to spray the deck today, but discovered another "seniors mistake",
NO BUNG!!!!
Somehow I forgot all about when bogging in the footsrap plugs and mast track.
So the bog holding that in is going off at the moment, plan is to spray the deck tomorrow.

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ned321 said..
Kowalski footstraps, I have them also, the best light straps
www.facebook.com/kovalski.footstraps?ref=br_rs
www.den-8.dk/new-footstraps

Thanks. They look like really nice straps, but I don't see any double width ones mentioned anywhere. Am I missing something?

Looking good Mike, cant wait to see it on the water. Have you weighed it lately and has it come in above or below what you expected.

I think it's around 4.5Kg, I'll weigh it when I get the paint on the deck. I think once sugar deck and pads are on it'll be around 5Kg. I suspect foot straps will push it a bit over.