Soft PE Resin after glassing in high temperatures

General Discussion
1

Firstly thanks for being here. This site is incredible and helped me greatly over many years. This is my first cry for help as I am doing something new that I don’t quite understand. 

I live in the tropics and we are training up the local boys to hand shape and glass surfboards and its going okay for the first round. (Imports are expensive and the local boys just want to make boards and surf). The PU foam is imported from Bennets Australia as is the 4oz cloth, Lam and wax/styrene. We have done a few boards so far and the resin seems a little weak and soft.

Using the same process I have previously used when in Australia and the only real differences I can think of is the boys are sanding too much (though seems fine to me). 2x4oz (650ml res) on the deck seems okay, 1x4oz (450ml) on the bottom seems soft in places. Only using a polished filler coat and no gloss presently. The same result is seen across all 5 boards.

I am wondering on the effect of temperature on the cure of the resin and whether it is too hot to cure properly. 

We are currently glassing in temps of 32-36 degrees celcius (sometimes more, sometimes less). Using a 0.3%-0.5% Catalyst mix (due to the temp it’s very low). That gives us approx 16mins before the lam kicks. This is PU/PE combo.

Could the temp be responsible for the softness? Could the blanks have weakened in hotter temps?

I did use local resin and it cured correctly yet turned yellow and is horrible stuff. I can just add another cloth layer but would like to understand more about the causes of the softness before I use the sledgehammer approach. Is Epoxy a better way to go (due to the temp I had previously decided not to)?

Any advice is greatly appreciated.

Cheers,
Dave

2

Thanks SammyA, They sanded well in the filler coat though some were still quite sticky after 24 hours in the lam before the filler was applied. Two of the blanks were seconds (for training) but didn’t seem soft before the lay up.

Boards are skinned on top and shaped from the bottom. We are using mainly 6’7 blanks (and of course the boys want boards thinner than a pencil) so maybe they are being overshaped and exposing too much soft foam on the underside. With a touch of oversanding I’m guessing this would produce the softer bottom.

Time for the sldgehammer approach and another lam coat :slight_smile:

3

Without knowing more details of the variables in your process, I really don’t think high temps will cause a ‘soft’ lamination. If the resin hardens to a full cure…easy to sand, not gummy, I would suspect the culprit is soft foam. Double 4 oz doesn’t have a whole lot of compression strength and will deflect easily on a soft blank.