Thanks Bertie, info recorded. Would love to build more boards with this stuff, but I have a feeling Bluejuice will get to it before I use my block of plain boring old porous white stuff!

Any body want to build a VERY thick board??????

no prob.

Damm! I was getting all exited till I saw the address and ph number. That's the place I used to get it from but they used to be called Urolight and the lady at behind the desk is Anna, They are agents for Aerodynamic Industries in Sydney.
Thanks anyway Bertie but those blanks they have there are about 45kg /m3 which = a shaped blank at 3kg's.
They are all yours Decrepit. I've got one here half shaped you can have for half that price.

so what density did u used to use BJ??? i know they has 2 densities there and the light one seamed pretty light to me.

how much would a shaped blank normally weigh? the density of EPS is about 25kg/m^3??? or am i all confused now??? way too much vinylester resin exposeure tonight ( on the upside i get to play with carbon prepreg and aluminium honeycomb tomorrow )

let me know the figures/weights coz now my brain is hurting.
Bertie

EPS 12.5kg/m3 = 1kg blank
XPS 28kg/m3 = 2.2kg blank
If the block is 2400mm x 100mm x600mm how do I work out how much that block should weigh if the foam is 28kg/m3? Whats the formula ?my maths is poor

mass= volume * density
but beware all the units are in kg, m^3 and kg/m^3
and i hope ur not serious.

Nuh Bluejuice, think I'll give them a miss, there's still about 4 boards left in the block I have, and no plans to make another board on the horizon.

Just in case you are serious, that's 2.4 X 1 X .6 = 1.56 cubic meters
X 28 = 43.68Kg

And by reverse engineering that 2.2Kg blank is 78.6l
and the 1kg blank is 80l


Pity about the 1/2 shaped board!!!
Maybe you should run a competion for ideas about what to do with it.
In this eco age a sacrifice ti Hui is probably out.

thanks

Hey Decrepit,
I think it might be 2.4 x .1 x .6 = .144 M3 or 144 Litres x 28 kg = 4 kg (unshaped)

hmm I'm getting confused now cause the blocks that size at "urolight" weigh 10.5 kg

quote:

---

Originally posted by Paul Kelf

Hey Decrepit,
I think it might be 2.4 x .1 x .6 = .144 M3 or 144 Litres x 28 kg = 4 kg

---

Thanks Paul, that's what happens when you get old and stupid, two silly mistakes, and in public, shame, shame!!!

OK, I'm games to try again .144 m3 at 10.5 kg = 73 kg/m3

Wow that can't be right!!!! what have we done wrong now?????

That's skin material not core.
Blue juice are you sure about those dimensions???
The ones I bought were 2,400 X 150 X 600. That still wouldn't make it right, but 100 mm is a bit thin for a modern windsurfer, makes it hard to get any thickness let alone rocker!!!

OK, .144 x 10.5 = 1.5 kg
after shaping approx 1.0 - 1.25 kg

Sorry Paul don't see what you've done here.

Didn't Blue juice say that a .144 M3 blank weighs !0.5Kg

Not that the blank was 10.5Kg/m3

You guys have me confused now!
I don't know where the 10.5kg came from or what it represents, I'm just doing the calculations for you.
You said

quote:

---

OK, I'm games to try again .144 m3 at 10.5 kg = 73 kg/m3

---

I thought the blank material was 10.5 kg /m3 but it looks like you meant the blank would weigh 10.5kg and a cubic metre would be 73kg.
Even Bomboras weren't that heavy!

But How STRONG wpuld it be!!!!

That's why I think there's something wrong with Blue juice's dimensions.
Something has to be wrong!!!! and this time I don't think it's me.

Where are you BJ????? please sort us out.

DAVO

You know the saying

GLASSED TO LAST OR GLASSED TO BLAST

TIGA 257 BLOWMOLD

G'day there,

I'm 107kg and have had an Acid 94 for 3yrs, released the breather plug where necessary, esp in WA, and never had a problem with it. The only way I killed it was in 40 knots getting catapulted in the harness, whilst coming off the back of a wave and slamming the boom/mast into the nose. It hit so hard the bottom copped a negative crease and months later delamed.

One common aspect I've noticed among delaminated boards is the point in the construction they seem to let go at, (Styrene / Divinicell). They seem to bond well together as there is a thin layer of Styrene left adhered to the Devinicell after delam has occured.

Maybe thru failing to always open/close the breather plug between sessions, (especially in hot/sunny conditions) the Styrofoam being weaker fatigues over time, from being stretched/pulled by the expanding stronger outer skin.

cheers

CarbonArt New Zealand - 2 warranties in 10 years.

Hey Bluejuice,

I've been wondering, why does everyone still use foam sandwich construction?

Most boards end up with holes in them at some time and because polystyrene foam isn't closed cell it sucks up the water and you can't get it out......dead board.

Wouldn't it be better if you could make a hollow board (something like the Salomon surfboards)or with multiple composite stringers (no polystyrene)then when you stuff it into a reef you can just empty out the water, patch the hole and get back out there....

Have you ever tried anything like that?

I have a mate who made a hollow board, but it was still foam sandwich. Weight was about the same, took a lot longer to make. (It was his first go so maybe he could have worked out ways to do it quicker). Was very noisy to ride, he called it his bongo board! Not sure what happened to it, he didn't use it all that much, think he got the rails a bit too thick or something.
That's one of the problems as far as I'm concerned. They really need to be made with a mould. OK if you're making lots of boards you can have a range of standard shapes, but I've never made the same board twice.
The other possible disadvantage, is they don't just suck a little bit of water, if you get a big enough hole, it could sink before you get back to shore!!!

Hi Decrepit,

Never considered the noise factor...interesting.

It wouldn't be a good construction method for custom boards of course but for mass production, I reckon once you had your moulds built you could bag the whole skin sandwich in one hit and then just trim and glue the two halves together around the stringer/core arrangement.

It would be quicker to build and lighter than a traditionally built board and would never get waterlogged. (I reckon multiple stringers would make compartments inside the board which would stop it sinking)

I want one....

That's very much the method my mate used, can't remember how many stringers he had, possibly just the one down the center.
The mould was an existing board he liked, I think that's why the rails ended up a bit thick, he reckoned he'd allowed for it but I'm not sure.
Trouble is with having multiple compartments, you need multiple bungs!
My mate made sure water could get to the bung from anywhere in the board.
Hmm you've got me thinking now, don't think he had a bung, he was confident enough it wouldn't leak unless dinged, then the water comes out of the ding hole before you fix it. I remember somebody doing the maths and expansion thru temp variation wasn't a problem.
For custom boards the solution is closed cell foam, pity that blue stuff is now too heavy!

Decrepit went and looked at an old invoice and the styro blanks were 200 thick not 100 SORRY!
Spotty you hit the nail on the head a sealed board will expand and contract on a daily basis due to the variation in the minimum night temp and the maximum day temp, and the weakest link is between the individual foam beads. I keep telling people use the vent plug, it’s not there for decoration.
Sinker I’ve always thought hollow was the way to go! A guy called Doyle in the states used to make hollow boards I think he makes kite boards now. I just can’t work out an easy way to do it. You would need a lot thicker sandwhich say15mm and thick PVC would be very hard to bend into the inside of a mould. If theres any geniuses out there that think they know how it can be done I’m keen (if I think it can be done)

All i can say is PVC foam and a heatgun.
i made a race car side pod by cutting out a flat sheet like you would with sheet metal and did 90degree bends and everything.

Anything is posible!!!!
B

quote:

---

Originally posted by Juice

Decrepit went and looked at an old invoice and the styro blanks were 200 thick not 100 SORRY!
You would need a lot thicker sandwhich say15mm and thick PVC would be very hard to bend into the inside of a mould. If theres any geniuses out there that think they know how it can be done I’m keen (if I think it can be done)

---

I wondered if you'd changed your name, or if there were 2 of you, now we know!
OK so that makes it 37Kgm3 that sounds more reasonable, but as you say too heavy!

Can't remember exactly what my mate did, but I don't think he went any thicker than 5mm, just had a few internal supports, 3mm dcell with 4oz glass bagged on either side, makes a nice light stiff "stringer".
There's a rumour that Saloman are giving it a go, but I think they're using more flexible internals.

Yep it would add an extra 1/2 kg in weight, the rumour is true the are using PPU foam.

hey,

aren't there some hollow (ish) starboards around, or at least hollow starboard proto's with starboard riders on them???

Anyone seen these boards. They have a bung in the nose instead of vent plug. I've seen em in white (painted) and ones that are wood all over with visible carbon under the heals, only in evoish shapes.

Have seen severne, patto, and others on em.


Are these babies hollow or am I way off??? A swedish mate of mine had one and it sounded pretty hollow when you tapped on it or looked in the hole on the nose. He mentioned it was done in a Saloman (blue board) type construction.


Anyone?

quote:

---

Originally posted by Juice

Yep it would add an extra 1/2 kg in weight,

---

Hey juice, do you lay up the internal cloth on the board or off???
I'm making a mal for a mate, and decided to use this board as a trial of laying up on plastic, looks like it would almost save you that 1/2 Kg.
I made myself an 8' mal last year sealed the styrofoam with a 110gm q-cell mix, then used 250 gm resin to wet out the cloth. aprox syrface area 2m2.
Mate's mal is 9'8" aprox surface area 3m2, used 210gm resin, that's a diference of 330 grams per side for a 3m2 board or about 200gm per side for a 2m2 area board. Blew me away, didn't think it would save that much!
bit of a pain getting the wetted out cloth on the board, but that weighjt saving is worth it. Did a test first and there's no loss of adhesion. Makes me want to build myself another wave board!!!

Hi Juice,

I reckon this is how to build a mass production "hollow" board. You need 3 moulds: top, bottom and 'stringer'.
Lay up the glass/carbon/closed cell foam sandwich in the top and bottom moulds dry, then resin infuse (no nasty wetting out and rolling, no messy bog, perfect glass/resin ratio)

Trim the product precisely to the mould.

Here's the clever bit:
Then lay up the stringer mould, basically a single corrugated sheet of glass or carbon. The stringer shape would have to be made to exactly fill the void inside the board just touching the inside surface of the top and bottom moulds.

Then apply plexus to the top and bottom points of the 'stringer' and assemble the board. you'd have to seal the edge join.

It's a bit hard to explain without pictures so I did a quick 3D model and I'll post the image under photos/other/stringer concept on this site.

Tell me what you think.