Right, bladder would be the best. My though is to make it from silicone, but not for this tube as it is pretty simple. 

Mate, seriously, you are pushing it with a 4m infusion, even2m is pretty optimistic and probably the reason it’s not coming out as youexpected it.

Do a test sheet, layup the same stack sequence on a flatsurface, about 200mm wide and say 2m long. Infuse as you would normally butmark off the resin front every 10/20/30s or whatever depending on the infusionspeed and you will soon see where it starts slowing down significantly. If you use a glass sheet you can seethe resin front at the surface and how much lag you have.

With a 2m infusion I would be looking to place the resinfeed inlet close to the centre of the mould but with a small diameter boom thisis going to be difficult.  Either that ora spiral down 2/3rds of the way or a multiple feed built into the mould.

If you try to do a 4m infusion with a single inlet and you reckon it will take and hour then it's likely that the resin front will stall at some point and you won't get a full infusion

The problem was in wrong vacuum film. After infusion resin ate out some micro holes in minutes. I both one from composites seller but with no any data sheet. After contacting they explained that is vacuum film for general usage . Now I changed it and test is good. 2m fiberglass tube with polyester resin infusion one inlet at one end bottom of tube and one outlet on other end top with spiral across the tube took 30min.

Interesting thread.

Just bought Dahlar RBG 460 and will try it. The first one was tubular too, but for general usage, and wasnt friendly ws resin.