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downunder wrote:

BWD wrote: @downunder:
I suspect he meant "heat" as in heat the resin used for laminating topsheet, to get lower viscosity, so bubbles escape and are easy to move around/out of laminate.... ?

The WS is quite low viscosity 1:3 by volume. 1:3.5 by weight.

Heating 100-120g of epoxy doesn't mean much in practice me thinks based on my experience with a topsheets and vac. It might work better with a press, centrally applying pressure, slowly to the rails, heating under bladder. Again in theory and difficult in practise.

The problem with a topsheet, unlike a FG, is the bubbles can't escape when rolling it. And a concave does not make it easier. A slight topsheet lifting up will make a huge bubble and leaving it for latter will make the things worse.

More and more I think a resin infusion is a go. But, how on earth can one do it under the topsheet is unknown to me.
OR, as discussed elsewhere, a tiny holes in a core to act as a perforated film and vac it as usual? But than, would more epoxy than needed leak out under the topsheet (and ss inserts) to the above layers? Duno.

Yeah heating the resin to minimize bubbles. Also Vac Bagging with resin infusion would work too. A Friend is making a foil at the moment using this method and his results are stunning!

downunder wrote:

sijandy wrote:

sijandy wrote:..and in case you're wondering it lived in the garden pond for a week to be able to get that nice person off!

what? why ? So after a week is the board still same rocker and concave?

I don't remember reading about it...Nice board tho. How muchos air bubbles in the rails? Perforated core for infusion, is it?

PS
600/300 on top/bottom? Would be better 300/600 for a wake board? How stiff is it?

I used a different kind of mould release that didn't work so i effectively glued the board to the rocker table. I threw it in the water to soak and help break down the mdf... tried everything but the best tool in the end was a wire brush on a grinder.... tore the shit out of the MDF but didn't hurt the resin/glass! And yes the board lost no rocker/concave but i fail to see why you would expect it too being left in water?

Fair few bubbles in the PU but not too bad, to be honest i think thats an easy fix i just need some PU with a longer pot life than 2mins.... unfortunately i still have about 2/3 boards worth yet and i'm a tight bastard so i'm ignoring that issue for the time being, it's only a cosmetic thing anyway.

Perf'd the core just too allow better air flow and help the excess resin from underneath out.

600/300 or 300/600 surely makes no difference does it? Must admit i've never really thought about it, i just tend to go with the heavier stuff closer to the core...don't know why just how i've always done it.

Hard to describe flex/stiffness cause it's all relative but it's one of the stiffer boards i have made, i intended it too be pretty stiff as it's for the light wind days there won't be any shitty chop too deal with and it'll pop much better.

i dont really think that small random bubbles under a preformed top sheet will contribute to any of the problems you are experiencing.

the process is pretty standard with sandwich skin builds for surfboards and windsurfers.
in both case the cores are 80% air and things generally work out just fine

if both sides are wet out and properly clamped, the amount of adhesive will certainly be enough to match the shear strenth of the core it attaches to.
as long as the top sheet is opaque, whose gonna know?

-bill

BWD wrote:by stripes I meant what you call stringer, not the paint job.
sorry I was a bit unclear.
but if they are just carbon tows on the bottom surface of board, it would be more typical to call them springers, than stringers.
Looks like a good way to do it.
I just put some bigger carbon strips on the bottom of a board that needed it (call them what you want), big improvement in pop/stiffness.
Nice work with the spray paint.

@downunder:
I suspect he meant "heat" as in heat the resin used for laminating topsheet, to get lower viscosity, so bubbles escape and are easy to move around/out of laminate.... ?

i thought maybe you did but then immediately below you mentioned stringers separately, anyway, whatever the f*** they're called they are too improve stiffness/pop. Seems to work well but they're a bugger to prep and lay down....i would use better stuff but it was a freebee and i've got shit loads of it!

Tone wrote:

downunder wrote: @downunder:

OR, as discussed elsewhere, a tiny holes in a core to act as a perforated film and vac it as usual? But than, would more epoxy than needed leak out under the topsheet (and ss inserts) to the above layers? Duno.

Yeah heating the resin to minimize bubbles. Also Vac Bagging with resin infusion would work too. A Friend is making a foil at the moment using this method and his results are stunning!

I can't wait to see his results with a topsheet

Ps
bwd the above fixed for you...

but i didnt wrote that
so confuse...
oh

zfennell wrote:
if both sides are wet out and properly clamped, the amount of adhesive will certainly be enough to match the shear strenth of the core it attaches to.
as long as the top sheet is opaque, whose gonna know?

-bill

You can see the topsheet on photos here:) So, no, it's not opaque, it's super clear.

If you look carefully at DSC05798 (Small) photo you can see what the problem is. See this "dry" spots ie top corner? They are not dry FG. That is the air trapped when rolling the topsheet.

And vac doesn't help here. Only a roller and good elbow works to dissipate the air pockets. To dissipate, but not eliminate...

downunder wrote: You can see the topsheet on photos here:) So, no, it's not opaque, it's super clear.

If you look carefully at DSC05798 (Small) photo you can see what the problem is. See this "dry" spots ie top corner? They are not dry FG. That is the air trapped when rolling the topsheet.

And vac doesn't help here. Only a roller and good elbow works to dissipate the air pockets. To dissipate, but not eliminate...

my appologies,
i was confusing the question with your previous thread about bubbles in the top (upper) surface of your board ....which you seem to have solved, nicely.

i have no valuable experience applying film laminates.
But i bet one of the DIY ski or snowboard sites has it all figured out.

-bill

zfennell wrote: But i bet one of the DIY ski or snowboard sites has it all figured out.

-bill

Probably just to use a solid colour so you can't see the bubbles

chrislandy wrote:

zfennell wrote: But i bet one of the DIY ski or snowboard sites has it all figured out.

-bill

Probably just to use a solid colour so you can't see the bubbles

i've only looked at a few of the sites , most have u-tube vids.

clear film is pretty common.
some are adhesive-backed for application , post cure or as a repair.

some , similar to the 'duravision' come with masking anticipating the need for adhesive.
one example i saw for skiis, offered the following:
-coat back of topsheet with epoxy
-coat top layer of ski with epoxy
-place ski in press
-place top sheet on ski
-add layer of smooth rubber on top of topsheet to better distribute load from high pressure bladder and prevent 'print thru' of bladder material
-bladder is located on top of rubber sheet (in press)
-raise pressure in bladder to 30-60 psi
-extra resin squirts out
-assembly is left in press until cured
-trim flashing and hit the slopes

the example in the vid was a clear top coat that looked nice.
but who knows?
-bill
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