The holes are just so that resin can flow through the core to saturate both sides of the laminate. Of course, this adds some weight. The holes can be quite small diameter (~1mm), so they don't have an effect on the strength or flexibility of the sandwich. Successful infusion depends on having a good uniform flow of resin through the laminate stack. Infusion will generally result in a sandwich that is slightly heavier than wet-bagging would produce, because of these small holes. Flat panels are much easier to infuse than complex structures, of course, so this difference is minimal. In a structure with any shape to it infusion becomes a more difficult operation, and a minimum of 5-10% weight penalty over wet bagging can be realistically expected. This does not include the spongy matrix layers that are used in some production shops to provide bulk required to address the print-through issues that infusion has.
OK - thanks Gardner, but can I have just one more dumb question?
If there are 1mm holes through [closed cell?] foam, then they must become columns of resin after infusion. So they seemingly,
1. play a part in cohesion between fibre-glass components which sandwich the foam, and
2. change the flexibility of the composite panel as opposed to one that was hand laminated without the holes.
So to the question bit. How does the composite made this way compare with the non infused one in terms of strength, stability of bond, and flexing?
(I know, I know... "Make one of each and test them". :) )
Jeff> On Tue, May 31, 2011 at 12:31 PM, jaythree59 <jaythree59@...>wrote:
--- In harryproa@yahoogroups.com.au, Gardner Pomper <gardner@...> wrote:
>
> Yes, the reason is just to be able to watch how the resin infuses on the
> underside. By seeing it do that, and getting a feel for how long it takes,
> that helps you judge how to do things when you make bigger panels on the
> table. Just attach everything to the glass, as if it were a table, and put
> it on sawhorses, so that you can watch the underside while you are doing you
> test infusions.
>
> - Gardner
>
>
> >
> >
> > Thanks, Rob. Er, you mean window glass? I have a piece of that 500 x 900
> > odd that I can lay on the table....
> >
> >
> > --- In harryproa@yahoogroups.com.au, Rob Denney <harryproa@> wrote:
> > >
> > > PVC (Herex, Divinycell, Corecell, etc) foam, 80 kgs per cu metre unless
> > it
> > > is a very big boat. It must be perforated (1mm holes at 50mm centres)
> > which
> > > you can do yourself by stacking and drilling, or you can pay for. Make
> > sure
> > > you blow or vacuum the sheets to remove any lumps from the hole making.
> > You
> > > can buy it with tracks (2mm x 2mm is standard, once you are confident,
> > try
> > > 1mm x 1mm) to disperse the resin, or use commercial disperser or hardware
> > > stuff (fly screen, shade cloth, etc).
> > >
> > > Start small (and ideally on a sheet of glass), then build up to full
> > size.
> > > Prep is everything.
> > >
> > > rob
> > >
> > > On Tue, May 31, 2011 at 10:05 AM, jaythree59 <jaythree59@>wrote:
> >
> > >
> > > >
> > > >
> > > > Hi,
> > > >
> > > > If planning to use sections formed on an infusion table for my 60/40
> > proa,
> > > > which kind of foam sheet shall I buy? I don't really want to waste the
> > > > section I make now - it would be kinda nice to point to some ugly first
> > > > effort featured in my boat later :)
> > > >
> > > >
> > > >
> > > >
> > >
> >
> >
> >
>