Made a flat panel the other day adding to my learning curve, comprising a 13 layer mix of 600g csm and wr with polyester infusion resin.
I stopped the infusion mesh about 30mm from the end of the laminate stack and there was a further 80mm or so of double thickness peel ply going to the suction tube, so plenty of brake to slow down the resin.  20 minute drop test and all seemed fine.
Started to infuse and soon noticed how the bag became loose/flabby and I assumed I had a vacuum problem but this wasn't so. (just read on the forum that this can be expected)  When the resin eventually bled in to the peel ply by about 10mm I clamped off the hoses. It looked resin rich to me or at least fully wetted out.
Came back the following morning and the whole thing looked and felt dry.  The mould side (glass top table) is shiny and there are no voids/pin holes or signs of leaks and seems perfectly ok but I feel the general appearance of the panel is wrong. Is this good or bad?
What should a polyester infused part look like with such low resin/fibre ratios compared to hand lay-up?
Should I have reduced the feed speed a bit by partial clamping the feed pipe to reduce the 'loose' bag effect?
Is the 'whiteness' just an effect of using emulsion binder csm?
Has the resin cured too quickly (about 1hr in this case) before it has a chance to fully wet out the csm?
Have I had a small undetected leak, so need to get a digital gauge as the dial I have is not sensitive enough?
Pic - infused

Pic - peel ply removed

Pic - mould side 

Pic - trimmed edge

Pic - panel view (patches are surface dust)

Where did you read, that a bag could get loose/flabby during an infusion. This should only happen if the resin is very viscous, or you used no flow mesh. Even then, the bag should only get looser near the resin feed. The bag should always be absolutely tight everywhere else.
From the photos it is hard to tell if the laminate is ok. The csm makes it hard to see air bubbles. But I don't see anything that looks wrong. Keep in mind, that the resin content of csm becomes way, way lower when using resin infusion. The laminate only takes about half the resin it does when hand laminating. So the final piece feels very different.

I came across an answer very similar to yours somewhere in this forum about someone else's issues, although they were only using a couple of layers of carbon. 
The bag was only flabby at the feed end and I had thought I had some kind of vacuum lock going on as it was down tight elsewhere.  The final piece is a constant consolidated thickness, so it is not as if I've ended up with a lump of resin and floating layers - just going to put  it down to experience! When I de-bagged, the flow mesh was perfectly infused - my best yet - which makes me think it is a good indicator as to the resin content of the part? I had about 2.5kg of glass and used 2kg of resin which I figured was ok. 
This is another part I made but with a foam core. Again, this has the csm on the top.

All the voids are filled so I assume it is wet-out sufficiently....?

Depending on the size of the bag and resin viscosity, you can find the resin end of the bag goes a little bit loose compared to full vacuum but it should not be totally loose. This is because initially you end up with a thicker layer of resin at the resin feed end as the resin is still infusing and soaking in. However generally it evens out as the infusion progresses.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

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Warren (Staff) - 6/19/2018 8:51:58 AM

Depending on the size of the bag and resin viscosity, you can find the resin end of the bag goes a little bit loose compared to full vacuum but it should not be totally loose. This is because initially you end up with a thicker layer of resin at the resin feed end as the resin is still infusing and soaking in. However generally it evens out as the infusion progresses.

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Yep, think that was happening...