Tech Articles

Wefunk Vacuum-laminating a cap-construction 101

There are different methods to do a cap construction, especially if you use a bag or a foil, pinhole foil and/or tear-away fabric or like I do: strechy foil ON resin and breathing cloth at the sides.

OK - I decided to give away some trade secrets:

I now have a very exaclty working electric planer (inherited from my uncle - way better than that sloped working piece of crap I could afford) which I use to plane down the 10mm foam-boards I have bought for the pure foamies down to 6mm.

I then router the shape of the core using a wood-template.

With a NT Cutter knife I cutout the squares where I put in the plywood blocks for the truck/baseplate support.

I then place everything in the mold starting with the top of the deck to become.

The mold for vacuuming is just one sided. It´s a block of cheap building insulation PU foam shaped to a rockered and convex form (like a long saddle) to give the deck the cambered and concave form. This shaped foam block get´s glassed, fine-sanded and polished.

I start with applying a nasty-smelling anti-adhesive coating to the mold and let it vent off.

Then I apply the self-adhesive vacuum putty tape around the edges of the mold. This tape comes on a roll and is like black chewing-gum and really sticky. I remove the "wax-paper" on one side of the tape in the last minute.

I start the layup:

- glass, resin
- wood (ash-veneer), resin
- glass, resin
- foamcore, resin
- glass, resin
- Texalium, resin
- placing the printed glass-fleece logo and date/signature
- glass, resin

I make sure everything sits straight and centerd in the mold. (I have marks in the mold to ensure everything being centered.)

I put in rolls/folds the "breathing"-cloth - recyled fleece stuff. I place them around the edges of the laminate. The cloth HAS to touch the laminate and glass fibres all around. There has to be enough of it to suck up excessive resin. It has to be as close as possible to the deck but not too close so that it doesn´t intersect with the outline you want to shape later.

I remove the wax-paper from the sticky-putty on the mold and attach the tube of the vacuum pump with some extra putty to one corner of the mold. I have some extra breathing cloth around the end of the tube.

I then place a thin, stretchy rubber foil on the mold, attaching it to the putty. This is one of the most critical moments: The putty is REALLY sticky and I want the foil to be slightly and evenly streched without any folds.

Start the vacuum pump.

Hear for hissing sounds (hard to hear cause the pump will be quite noisy) where the foil has to be pressed to the putty to close gaps. Apply extra putty to seal gaps between mold and foil or to close folds in the foil. Always watch the pressure gauge - there might still be small leaks somewhere. If the sound of the pump is "right" and the pressure gauge shows 8.5 bar negative pressure you have the worst part done. You can´t possibly do anything to correct any mistakes you might now encounter. (core offset, logo not straight, breathing cloth too close to core etc.)

The only thing you might do is GENTLY pressing large bubbles to the outside with a soft roll. Don´t overstretch or rub the foil - it might stick to the laminate later.

I suggest using a slow hardener or a resin system where you can mix hardeners. The resin needs some time to move to the outsides into the breathing/sucking cloth.

I also found out that the room temperature is essential to how the resin and the foil (sticking to it behaves). 20°C / 68° F are perfect. When it was really sweating hot in summer I compensated for that with slower hardener but the foil tended to stick to te laminate - very frustrating! If it is too cold in your workshop the resin isn´t as fluid and will have a hard time to flow to the outsides.

I now found out (the hard way again) that it was our (specific) slow hardener which caused the foil to stick. I changed the slow to fast ratio by a fraction towards the fast hardener and don´t have any problems.

Check out Wefunk get in touch with the author at alex at wefunk dot de

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