Resin Infusion Techniques

[Neil C.]

I was idly browsing the website of my local fibreglass supplier today (www.ecfibreglasssupplies.co.uk). They have a whole section selling equipment and accessories for resin infusion techniques. I don't really know anything about resin infusion. How does it work? Is it something you could use for small boat building projects?

[phil_kirk]

I have never tried resin infusion but understand that allows you to lay up the item dry in a vacum bag and then the resin is sucked in from a pot when you apply the vacum.  It means you only use the correct amount of resin and should be good for large jobs when you don't want to be constrained by resin curing time.

Difficulties. ensuring that the inlet hose allows the resin to reach all of the laminate before reaching the vacum hose. That probably requires a little experience.

I don't think we would gain anything unless making hulls or thicker laminates.

[TSC]

Its a great technique for producing minimum weight parts. As Phil says, you can lay all your cloth in dry and then once happy with it, you vac it down, release the valves and pump the resin through. You basically want the have the resin entering the bag in the largest volume end of whatever your making, and have your outflow somewhere near the other end. You use the vac pump to draw the resin through but have a collecting vessel in the system before the pump.

Its really good seeing the part wetting out, as the resin is drawn in, and if you have your resin in a container on scales you can see how much goes in.

In principle any parts you would normally bag, will benefit and it shouldn't really take much additional time.

[Phil Alderson]

I have tried making a couple of things with resin infusion, and I think it benifits from practice. Sealing is critical, as a small leak will ruin the part.
I have never done it on foam, as I was concerned that you would get a lot of resin into the holes in the foam cells, unless they were well sealed, and with thin laminate this could be significant.

The other problem I have had is temperature, my garage is normally cold so I normally heat the area after I have finished. With the infusion I fond it hard to keep the heat even so the part and the resin was warm, but never got too hot and set.

[phil_kirk]

I have a thick fleacy builder's dust sheet which has proved very useful for making a small tent over the fan heater and anything you want to cure.  Just means you are heating a smaller volume and can reach a higher temperature with the same amount of energy.  This technique may help with resin infusion. With my garage I would probably end up heating much of gloucerstershire before the garage temperature rose at all.

[roland_trim]

For infusion we found we wanted a higher temp, so it is the tea urn sending hot water through pipes criss crossing below the item. If I were to do it again I'd fins a road sign (or similar aluminum sheet) to drop onto of the heat coils to spread the heat out.

As an aside we found that wet layup was far lighter for the garage style working we are doing as the voids and joins always seem to let us down.

[andy_paterson]

Infusion bladerider moths are a couple of kg (  or 20% !!   ) more than the earlier wet layup ones.
But maybe the supervision / workforce had changed also.

[tim_unerman]

From quite a bit of experience of both standard hand layup and resin infusion, when using thin laminates with cored structures if you have the right skills hand layup will tend to give a  lighter laminate. When you start getting thicker laminates resin infusion work better also the extra resin in thicker cored structure is less notable. So what Andy is saying about moths makes sense.

[Phil Alderson]

With a tent and fan heater it is hard to control the temperature exactly. With a hand layup the diference between 20 and 30 degrees is not critical. But for infusion it is as too cold and the viscosity will stop it, too hot and it sets too quickly.

[phil_kirk]

I'm learning about this. 

I can see that resin infusion allows larger jobs to be done more easily especially if hand layup meant that early layers would be starting to cure before the vac bag was sealed.