Delemma-Hull to deck joint

people forget that vacuum is pressure applied over the whole surface not just in places , so yes you are very close . it doesn't sound much but even 1.5 psi is enough depending on the foam core thickness and the viscosity of the core bond at the time , wetting out the core with a generous coat of resin is really important and allows the core bond to slide and penetrate much better in to bleed holes and gapes and any spaces to fill them completely and absolutely smooth and of course give a core bond thickness so there is exotherm and cure will take place this is a problem if the pressure is to high and the film thickness is thin cure never really happens properly !!good or bad bond the peel ability of foam is it weakness and real scary!!

 

Isn't it resin infusion that takes a bit more pressure (the 3-5 quoted) to 'pull' the resin through a good size piece??

I was thinking about those 'core bond' adhesives being a bit 'stiff' to bed a big piece of core into.

 

Ok so you never seen or used core bond ??
When the core bond containers arrives you need to check first the date of manufacture , and record the batch number . take the top off the container and observe the contents . even just 2 days old it will have separated out and have like a thick crust on top so needs a really good stir up and remix . this is not just a matter of a stick and trying to do it by hand !! you need a big stirrer and a big drill and stir for at least 5 to 10 minutes . then leave to stand so the air can come to the surface !!, now you'll find it is quite trowel-able and runny almost . take out the amount required for you job and catalyse then trowel onto the job ,the trowel with a vee shape is best and a uniform spread and thickness all over every where !!. the core needs to have a generous coat of catalysed resin applied with a paint roller so all the pores of the foam are completely filled and its shiny all over including the edges (is best to do this before you start to trowel the core bond) !!,then place the core on top of the core bond starting with one side or edge and bend the sheet slightly and with a rolling action press firmly down into the core bond , the resin makes the core bond move much easier and flow and dispel the air bubbles that will be under and need to come out , the perforations in the core already are really not adequate ,the number need to be doubled and the size doubled as well !!pressing evenly and not squashing till the core bond oozes out all over the place it needs to stay under the core . then vac in place with the usual procedure . peel ply , course air bleed and bag . the signs of even pressure are the resin comes out first and then the core bond follows !! ,the core bond should bleed to about a 10 to 15 mm dia spot under the peel ply and be consistent all over the whole panel , with a little practice this is achieved 100% of the time if you doing a few panels .
a gentle suck to press firmly (always use a pressure gauge and never just guess ) and evenly then write the time on the bag with a marker pen and the pressure setting and check periodically and allow 2 hours to gel, harden ,and cure a little and be quite firm to press your thumb nail into !!
. off with the vac and take all the peel ply etc off and there is your panel ready for the layers of glass on top .
The core bond we used was manufactured by ADHESIVE TECHNOLOGIES , always fresh, always consistent ,and always arrived on time !!
Like I always say at the end of each one of my descriptions of how to do a particular job "KNOW THE PRODUCTS YOU USE AND UNDERSTAND THERE CAPABILITIES "and you wont have any sort of problems !!

 

I meant that it is relative:
When I make flat panels (on a flat and hard surface), I actually would not need a vacuum at all i.e. with honeycomb. Just make sure it is touching throughout. Similar to foam, but some gentle pressure is welcome.
For curved vacuum applications in or on moulds I need the pressure higher than a possible tension in the core. If the core is thick, heavy foam used, or with strong curvature, vacuum will be stronger. Sure, the core can be cross-cut or whatever, but I tend to avoid this solution;
My pressures vary between 50 and 70% in average. (ca. MINUS 9 to 10 psi)
When vacuuming a laminate, I found that excess resin is not evacuated to my satisfaction with pressures below 50%. Anything above 70% does not improve consolidation or surface quality (waves/wrinkles).
In this pressure range I achieve glass ratios of 55 to 60%, a little higher with carbon fibre.
When the vacuum is set, my first test is to pull the bag by hand: if the pull is not evenly or does not have the 'right feeling' I search for leaks.
Next, I judge the way resin comes through the bleeder (evenly?reluctant?excessive?) and take action if required.
Can't say anything about infusuion - have not tried it yet.

Have I passed your exam? Can I send you my resume now?

 

how would you wrap 20 mm sheet of high density form core around a 60 mm radius corner , and not have any core print through anywhere on a 2 layer 600 gram glass skins ?? wasn't easy and took 5 minute to sort !!on 8 boats !!:idea:

 

I wouldn't (wrap).
Please ignore my resume.

 

Its really simple and nothing complicated at all !! and no heat is involved !! !