layup thickness?

[ianupton]

How thick should 1808 be per layer?

I was messing around with the excess fiberglass and resin that I purchased and was experimenting with layups where I was trying to maximize glass to resin content.

I wet out 4 layers of 1808 (roving and mat), covered in plastic and 'clamped' between table and heavy MDF block.

After everything set-up, I inspected... appears the be fully wetout.

Thickness 1/8"

I would have thought a bit thicker. I understand that in vacuum bagging, you have a thinner laminate but stronger.

Thoughts?

Ian.

[CaptPatrick]

Ian,

Hand layups without vacuum bagging will have more thickness due to excess resin content. Chopped strand mat will average about 30% glass & 70% resin, by weight. 0º/90º plain weave will be around 50/50, un-backed biaxles around 45/55, & mat backed biaxles around 40/60.

Too much vacuum can starve the fiberglass material of resin... Non-vacuum compression, (your experiment), will compress the weave and force out some excess resin.

Lower resin contents, without starving, will yield a stronger composite, it will be thinner, lighter, and more flexible. Higher resin contents will be just the opposite.

Generally, 98% of the layups done in refurbishing our style of boats don't benefit from the expense and energy necessary to achieve a low resin content. As Bruce has pointed out, these are boats not space shuttles...

What is more important in straight hand layups is complete wet out & minimal trapped air. trying too hard to work excess resin out of the weave usually only promotes trapped air.

Also watch out for draining of resin on vertical surfaces... If the resin doesn't gel quick enough, especially on heavy layups, the resin will drain down the vertical surface leaving a porous upper area and an overly saturated lower surface.

Br,

Patrick