I am currently doing a DIY project of making an extended swim platform for my boat.  The platform is fairly large measuring 8 feet x 4 feet (2.4 m x 1.2 m).  I am making a mold from a plug and then will make the actual 'part' from the mold.  The platform design is of moderate complexity, having a step-down section to it and 'pylons' on the sides. The total area of fiberglass is about 40 sq. ft. (3.8 sq m) due to the complexities of shape.  I plan on using VARTM in order to achieve good conformity of the fiberglass to the various shapes of the platform, and hopefully to apply the resin in one step vs. a more labor intensive process of hand layup.

I'll be using polyester resin to make the mold and vinyl ester to make the part.  One concern right now is finding ways to reduce the 'fill' time of the VARTM mold/bag considering that poly resin has a fairly short 'open' time as compared to VE or epoxy resin.  In order to get a reasonable thickness of laminate, I plan on using 3 layers of 1.5 oz chopped stand mat. Then I will add stiffeners and reinforcements as hand layup after the vacuum bagging is complete.   I figure that the faster I can get resin into the mold/bag and going through the flow media to all areas of the mold, then the more time the resin has to flow into and saturate the fiberglass.  My plan is to have lots of resin runners throughout the mold so that the resin does not have to travel very far.

One idea that I am considering is to pressurize the resin pot slightly, which is more typical of an RTM process, so that the resin is drawn through the tubing and into the runner system and flow media by both the vacuum from the bag and the pressure from the resin pot.  I have done some searching and have not found much in terms of trials and experimentation of actually putting pressure into the resin pot, rather than merely relying on vacuum.

My thinking is that with just vacuum to move the resin from the pot to the mold, you are limited to 1 atmosphere of pressure.  With both vacuum and pressure in the pot, you can go beyond 1 atmosphere of pressure.  (within reason of course).

I am wondering if anyone has thoughts, comments, or experience in using both vacuum and pressure to get the resin to move to where it needs to go faster than it normally would with just vacuum?  Thanks in advance for any comments/insight/adverse effects.

I have tracked down a supply of the crystal (flake) form of TBC.  I had to order it from a retail supplier that acts as a middle-man between the commercial supplier and the end customer.  It seems that the product you mentioned. . . Pergaslow BK-10 is not readily available in the USA.  I did contact the USA division of Pergan (Pergan Marshall) but have not gotten word back.  In the mean time, it looks like I will have a life time supply of resin inhibitor, once I mix it at a 10% solution (by weight) with either styrene monomer or actetone.  I'm thinking styrene would be best.  The smallest amount of TBC that I could order was 250 grams.  I think I'll use not even 10 grams of it.  However, after days of searching and contacting various companies, i'd just be happy to have some in hand.

Along the way, I've also been steered towards a 'slow' catalyst  . . . Norax MCP which gives about twice the gel time as MEKP.  I'll have both to try and see which of the two works better for my situation.