Is it possible to use the spray adhesives on a surface that only has PVA on it?
I don’t do the gelcoat thing for various reasons, but would still like to use the spray adhesive stuff to hold down the materials when laying them in molds.
I guess I would have to be very gentle with it so the PVA won’t rip…
is it just a light misting with the adhesive?
I recall people talking about the 3m stuff, are there different varieties?
I use it in combination with a pva’d mold. Spray the cloth itself very lightly mist it with spray glue, then lay it down. Make sure you infuse within an hour of spraying the glue, else it gets hard and you end up with bad results.
Hmm, an hour is quite short, I don’t think I could do it within that window…
Use the 3M 75 for the first layer, spray it on the cloth not the mold. There is no residue at all. If you use the 77 (no gelcoat) you will get a residue if allowed to dry hard and pits in the final surface. The 75 doesnt have a high grab so make sure the cloth does conform to all areas. The 75 also allows repositioning.
I have used the 75 for some time now even on very complex molds with tight 90 degree bends. All subsequent layers i lightly mist the cloth with 77.
Hope this helps.
Baz
so are you saying that the 75 will not cause pitting if it drysand can be allowed to dry whereas the 77 can not?
why cant you do it in an hour? you just have to START the infusion within the hour…
get EVERYTHING ready before you even start to do the infusion…you need a checklist of things todo ahead of time that way you arent running around trying to get things you need…figureout EVER SINGLE step you need to do then write it down…figureout what steps you can do before you start the infusion that way you can save time and not have to rush around
this is MANDATORY for hand layups…you have a very very precise schedule that you have to follow or else your part just wont turn out right…
I don’t think I could get all the layers in there and get the peel ply on ther and get the resin flow on there and then the bag with proper amounts of pleating, leak testing (which alone would take up about half that window)… I’m very maticulous with everything I do, the exact position of all pleats etc.
The 75 is a repositionable adhesive and stays tacky. On parts where i have to make a cut line i spray it thicker and the cloth then acts like a prepreg with the weave staying intact. Also the 75 is a finer spray and colourless unlike the 77 which is yellowish. There is no pitting with the 75 and no residue, the surface is shiney and as smooth as the mold surface.
Baz
that sounds perfect thanks.
where do you guys buy the 75 adhesive from? I looked on the home depot website and other sites, but nobody has it listed.
I get mine in the UK. Did a quick google for you (3M 75) first one i see in the US is here http://www.hillas.com/Products/3M_Aerosol_Adhesives/Default.asp but i guess there are many more.
Baz
thanks baz I already saw that one, but you have to buy an entire case:eek: