I have a big problem with the water-tightness of my boat shell. It shell MUST be very thin like no more then 0.40 mm after laminating, I made the first layer of spayed gelcoat GC50, then one layer of matt 30gr,  one fiber plane cloth 50gr, aramide 100gr and last fiber cloth 50gr. Then I put peelply, perforated sheet and absorber cloth. Next was to apply the vacuum for several hours until the epoxy resins cures. After de-moulding and pulling off the peelply I could achieved the required shell thickness. When I did the water-tight test the shell has had so many micro pores and leak badly. The next time I did the same with exception of peelply layer because it looked to me that pull off this layer opened the micro pores. In that manner I increased the shall thickness for more then 50% !!!! Water-tightness is OK but the boat shell is to thick and to heavy and it is not competitive. 
Please HELP me with suggestions how to make water-tight shell at minimum thickness !!! What lamination layers and fibre you can suggest?
Thank you in advance and best regards,
Miroslav

If you used vacuum compression, you seem to have a vacuum pump. If it is an oiled rotary vane pump, it should be able to achieve enough vacuum for resin infusion.
Such a thin shell could get tiny holes, when using hand laminating techniques. Basically any small air bubbles could have an opening to the inside, after the peel ply is removed.
By using resin infusion, you should get away without trapped air bubbles, and therefore you should get a  leak free hull.
I wonder about your layup. With only 0,5 mm, any contact with rock's will get though your hull, with or without aramid. The aramid might stop tge damage growth, but the boat will sink anyway. You should get away much cheaper and faster, by using only 2x200g carbon.

Do you really need the gelcoat from the weight perspective? Assuming you can solve the water tight issues, then I would suspect the gelcoat is added extra weight.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Infusion with tight resin management will save quite a bit of weight compared to vacuum compression. The trick is to clamp of the resin line before the flow front reached the vacuum line. Ideally, the resin will then spread just over the whole part, from the excess resin near the resin feed line. But be careful, if you clamp the line too early, you might get gas bubbles in your resin, especially if you didn't use a degassing chamber before.
If you get your part out without air bubbles, it is unimportant wich layup you have choosen, the laminate will be water and airtight anyways.
If you want to go really light, both gelcoat ant mat are really bad ideas. What cloth are you using? As it is 50g, I assume it is glass cloth. Glass has about twice the density of carbon. So for the same cloth weight you get less thickness, and therefore less stiffness. As the stiffness goes up to the power of 3, while the weight goes up linearly, a thicker laminate with less density is the better way, not to mention, that carbon itself has a much higher Young's modulus compared to glass.
2x200g carbon will get you about 0,4 mm thickness, while being more rigid  in the end.