pre release issues

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#1

I am building some J foils for a foiling multihull.

I am laying them up in 2 halves, then adding a shear web before joining

I am getting some problems with pre release. The mould are finished in Duratec to 600 grit and then we used Safelease as the release agent.

the layup is in M40J pre preg.

I have tried a few different ideas, the last one involved the laying final 2 layers of RC90 onto the mould flange which had no release agent applied… even that jumped out the mould.

Is there a release agent that will only release when you want it to… i.e. after i have routed the part level…?

#2

J-foils and routing them level, that sounds interesting :wink:
High temperature wax based release agent is less slippery than semiperms. Some here apply a surface sealer underneath. But I doubt that will hold the blades in while routing. Maybe there is an other way of keeping them in place?
I sand the edges level, but I’ve never made curved foils…

#3

Zyvax makes a release system with 6 levels of “slip” called Flex-Z. Flex-Z 1.0 has the lowest slip while Flex-Z 6.0 has the highest slip. They can be intermixed so you can have some area of the mold with high slip will others like the edges can have a lower slip.

#4

If pre release is anticipated, my preferred option is to use Tooltec release film/ply with an “edge bag”. You use a perimeter bag connected to a vac pump to keep the part firmly in the mould.
The slight porosity of the Tooltec works in your favour here.
However:
In this case it may be difficult as I suspect the routing includes the perimeter areas as I am guessing it’s a split female mould joined at the leading and trailing edges.

This usually requires a strip of flash tape applied to the mould surface at the leading and trailing edges before lamination commences.
The prepreg takes to the surface of the flash tape well enough to perform careful routing, but it will not tolerate much abuse.
If this pre release persists, you will need a vac port that penetrates the mould and connects to the tool surface. This is so that you can connect your job to a pump after curing and before machining to keep your part locked down.
After the two halves are joined and released- The rebate formed by the flash tape is then filled by a secondary external tape (eg: 1x RC200 @ +- 45.) This is good practice for the leading edge of foils which have a habit of splitting without a capping tape of some sort.

Do not underestimate hydraulic forces!

I’d also save a small amount of prep by pre applying prepreg peel ply to the tool surface first in the bonding areas.

If your laminate is very unbalanced, you could find that nothing will keep the foil in the tool.
This is when you have to try and co-cure the two halves together. I have done this with hollow foils and syntactic foam in the trailing edge.

Have fun!.. Jim.

#5

Thank you for the replies.

I’ll keep plugging away and work this one out…