Vacuum bag - which VB material order

[TomW]

Need some help.

I´m doing wet laminating against a concave rocker table in one shot.

snowboard style with edged core.

What is the correct schedule of materials?
1.
from top:
-vacuum bag
-bleeder/breather
- peel ply fabric
-laminate
-core
-laminate
- peel ply fabric
- solid release film
- rocker table

OR
2.
-vacuum bag
-bleeder/breather
- perforated film
- peel ply fabric
-laminate
-core
-laminate
- perforated film
- peel ply fabric
- solid release film
- rocker table

as i understand it, nr 1 will give me more resin bleed and a dryer laminate, and nr2 will be more resin rich.
Do i use nr 2 and weigh the resin, accounting for absorbtion of core and some small absorbtion into bleeder?
Or nr1 and use lots of resin and hope there is not too much absortion?

TW

[zfennell]

hi,

just to clarify, your using 1/2 bag by sealing to the rocker table ?
as opposed to a full bag that will need to be clamped to the rocker table by additional means?
the full bag is not as bad as it sounds, because it gives you the opportunity to work the bottom surface a bit while vacuum is being applied

if using perforated release film on top side, between the breather and laminate, the peel ply fabric should not be needed.
peel ply works well, but is principally used to leave a coarse surface for additional bonded layers. the perforated film will give a better final surface.

the bottom portion of the layup will be the most difficult .
if the table is smooth and you use mold release, you wont need the solid release film.

without breather it will be difficult to maintain enough vacuum on the bottom of the board to squeeze out the surplus resin.
i dont think the peel ply is really up to the task.

if you dont want breather on the bottom, you should give extra effort to 'squeegee' out as much extra resin as possible before putting the core on the table.

a small test piece is not a bad idea to get your recipe in good working order before the real thing. there always seem to be little surprises depending upon the actual sequence of events.

dry patches happen, but if the lam is wet out properly and the amount of vacuum is not excessive ( 8-12 psi of vacuum) , the core is not out-gassing and the bag is not leaking, you'll be fine.

no worries,
-bill

[TomW]

Yes, I´m using a 1/2 bag. The board will have 18mm concave put into it by forming core over concave form.

I understand what you are saying about the peel-ply, only use it if i am going to do subsequent bonding.

Do u think i could get around the problem of the bottom laminate "wet-out" by using a breather and perffilm on the bottom. Wouldnt this make the bottom "uneven" by print thru of the breather non-woven?

Or maybe i am think all wrong- the laminate is much harder and non-saturated so the breather will not print thru..

Thanks for your help.

TW

[crabman]

Dont use anything on the base if you are using a rocker table .All you need on the rocker table is release film stuck down .If you are using a bag without the rocker table ,then you can use identical top and bottom . What happens if you use peel etc on the base , when pulling vacuum it will crease . If the base is resin rich when you de bag ,it will mean less work for the finish .

[zfennell]

Yes, I´m using a 1/2 bag. The board will have 18mm concave put into it by forming core over concave form.

I understand what you are saying about the peel-ply, only use it if i am going to do subsequent bonding.

Do u think i could get around the problem of the bottom laminate "wet-out" by using a breather and perffilm on the bottom. Wouldnt this make the bottom "uneven" by print thru of the breather non-woven?

Or maybe i am think all wrong- the laminate is much harder and non-saturated so the breather will not print thru..

Thanks for your help.

TW

there are lots of ways to make it all work.
but 'wet-out' is you saturating the cloth with resin before going into the bag. despite the amount of total force the vacuum bag can generate, there will be very little net flow of the resin. the bag is only pushing the peel-ply or release film ( like a strainer) up against the laminate where it must stop. hopefully the extra resin passes through the release film and absorbed in the breather. without the breather, the only resin removed will be what squirts out the edges ( not much).

crabman's way will certainly work and he is correct about the extra resin and better net surface. But at that point, I'm just wondering why bother with the bag at all? just put a sheet of plastic over the bottom lam and squeegee out the excess resin.

the bag can be used for two things:
-a flexible clamp
and/or
- a method to increase laminate strength by reducing excess resin and weight

both are good things. you just got to keep track of your particular goals.
two words : test piece.

-bill

[TomW]

Thanks for the replys, helped alot.

Ive decided to use PBT dye-sublimated sheets as the final cosmetic layer, so i need a bondable surface when cured.

My plan:

My rocker table is made of MDF, so i tape down a PE release film first, then tape down a Peel ply fabric.

Wet out glass-carbon-glass on peel ply fabric. Squeege out excess epoxy.

On another table i prepare blank by wetting out deck layers: glass-carbon-glass+ heel reinforcments directly on blank

Lift over blank onto bottom laminate. Make sure i have enough epoxy to bond bottom of blank.

Lay down peel ply fabric and breather over deck laminates

Seal down 1/2 bag and turn on vacuum.

---------

Sound reasonable?

---------

I´ll do a test too.

TW

[crabman]

No ,do all your laying up on the rocker table . Work from the bottom up in situe.If you try to move fabrics wet, its near on impossible and you will bend the cloth yarns all over the place .

[zfennell]

i dont think you are planning to do exactly what crabman is worried about.
but he has a good point.

if you wet out the bottom lam on the table,
using the squeege on the 'wet' side may make a mess.

adding the core to the wet rocker table may trap air that you can't see or remove.

if you reverse the order a bit by wetting out bottom lams on the core, you can add release film and squeege that, through the film, without making a mess and be more confident of the final appearance.

but, you mentioned using a top or bottom skin of PBT.
why isn't that the first layer onto the rocker table?

if you were considering adding the PBT as a additional step.
you may find things a lot easier if you do a two step process by baggging All of the the top layers . let cure . then bag All of the bottom layers, including the pbt.

by now i guess you've figured there are many 'twists' to all this.
if your looking for more ideas that may suit your needs you may want to browse yahoo boardbuilding group . the search function may get tedious but virtually all the advanatges and pitfalls of every layup method is in there.
-bill

[Halomon]

Howzit TomW; good luck on your vaccum bag adventure. Personally, I have never witnessed the process and look forward to the seeing it done. Someday, maybe. I build my boards old style; shape foam and hand laminate. I can see vaccum bagging has advantages when laminating multiple plys of different materials that must conform to the specific curve of a rocker table.
On the subject of fumes/toxins; the difference in the fume/toxin/whetever level between epoxy and surfboard[polyester] resins is huge. I have switched to epoxy for exactly these reasons; less odor/fumes etc.
Be sure to have a quiver of good masks and respirators, always use em and don't let pregnant women in your glassing room. Build safe so you can kite more!!!! CHOW

[TomW]

Tried a test piece tonight.

Did as i said and laid out bottom layers on rocker and top layers on blank and then lifting blank over to rocker table. No Probs with layup.

Get your point on trapped air. I´ll probably do a 2 step and do bottom first, then top and then single bag the PBT-top n bottom at same time. Takes so long to wet out all the layers, i´m worried one side will start going off before i´m ready.

BUT, my big prob is that the 1/2 side bag did not take a vacuum. I am sure the bag itself and fitting and pump are working. Could it be that the MDF (4mm) is not really air tight? Perhaps air was leaking thru??

Hummmph. Should i make my rocker surface out of a PC sheet or just seal the mdf with epoxy?

(My first boards i made in full bag. Put the blank + lams + top and bottom cosmetic sheets, all into the bag, together with a rocker form made of glass and foam. Worked good. But it was a lot of work to make the rocker form. Trying to avoid that this time....)

TW