You shouldn't need spiral on the vacuum side as well, you're going to have an even vacuum as it is. Really you use spiral on the vacuum side when you want to distribute the vacuum more evenly, so if you had an irregularly shaped mould that you knew was going to flow faster in one direction than another, you can use spiral tube to create a vacuum manifold that continues drawing the resin towards it rather than the flow sealing itself off and becoming choked. Because your geometry is very straight forward, your resin is going to flow very evenly out of the inlet spiral and straight down the tube. If you are envelope bagging, you will probably find the seams flow marginally faster than the rest of the tube, but I would still wager your flow front will get to the end of the tube all within about an inch of itself.

With connector positioning, you want to position everything off the laminate if possible, otherwise it will create a defect in the laminate. So unless you need to run spiral tubing on top of the laminate for some reason, again usually geometry related, then you keep it and the connector off the laminate.

I would say your biggest challenge will be the length of the infusion. 1500mm isn't an excessive distance for infusion, but after about 500mm the flow does slow a bit and at about 1000mm it can become a bit of a crawl. Which creates two issues:

1. You need to be aware of your pot life. Mix in 1kg batches rather than trying to do big batches of resin. Have the second batch mixed and ready almost as soon as you start the infusion, the first kg or two will flow very quickly. Once in the part your resin should continue to flow for atleast 3-4 hours, so its the resin in your pot that you need to avoid gelling or even getting hot before the infusion finishes. 

2. Keep an eye on your resin inlet during the infusion, and watch for slackness in the bag. Often if the resin is flowing over a large distance, the resin can sometimes flow into the bag faster than it can flow through the laminate, which leads to excessive pooling and slackness on the feed side of the bag. if you do notice it becoming slack, simply clamp the feed line for a minute or so and allow the resin to move through the laminate and even out again before you unclamp and continue as normal. 

To be honest, I doubt either of those will be too much of an issue if you are using a proper infusion epoxy. I would expect your infusion to take 40 minutes to an hour, so it won't be extremely long. But thought it worth mentioning anyway.

And also I have the spiral tube past both ends of the layup to guarantee the resin flows the full length of the layup. So the spiral is not sitting on the layup as such it is on the peel ply just prior to the cloth/core, and the connectors are half on and half off the layup. I seem to remember someone in the past saying the connector should sit flat on the layup?
Where exactly should i position the spiral to guarantee the whole lot gets wetted, is it OK to put them about one inch in from the ends?

Thanks for the reply. Makes perfect sense. Do I use spiral tube for the vacuum circumference, as well as the inlet?

Mesh the whole thing, and just cut the mesh back about 3" in front of your vacuum connector. You don't want your brake zone in the middle, remember that the resin is flowing through the entire part, not just the flow front. So if you have a brake zone in the middle, the resin can not speed up again once it hits the last third of mesh, it is still having to flow through the brake zone. 

You also don't really need a large brake zone here, the resin should flow quite evenly through the whole part. So all you really want is to slow the flow for the last part of the infusion.

Hope my description makes sense? If not this picture might help....

Thanks all for your replies. I have breathered the mould external for envelope bagging.
The layup is 4 plies of 200g, 3mm of 3D core PET 100, 4 plies of 200g.
Not sure about the best infusion arrangement here?
I have peel ply overall, the first third has infusion mesh, the middle third is bare to act as a brake, and the last third has mesh. I think this might work or should I use mesh over the whole lot? I have spiral tube going around the circumference at the inlet, should I also have it at the outlet?

Regards.

It peels off easily afterwards too. You could spend time sanding the outside of the mould to remove sharp edge issues.  Then of course you could envelope bag the whole thing as suggested before. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

RTV silicone gasket maker is your friend here...

Can you use the seams to your advantage as vacuum manifolds?  If you infuse from the inside middles of each half and pull vacuum at the seam using some spiral wrap or flow mesh on the outside - so the seam is the air-channel?  Might be hard to get the resin to converge at the same time... Or you could feed resin in one seam and pull vacuum on the other. I have done this but the split line of the tooling had some features that made it work.  

What is the layup?  How many plies and how are you connecting the two halves?  Core?

You might be able to fill in the area between the ribs on the back with very cheap insulation foam and have that make the bag less difficult.  But its extra work...

The resin will only go where there is a path and you may be able to block it by leaving the breather on the back pulled back from the edge by a bit - and hosing the sealed back of the tools with PVA or something might help.

Do they have to be co-cured in one piece or could you layup in halves and tape together?  Or wet-bag?