fiber content in GRP laminates ???

the question is quite easy:
-Wich is the tipical glass content in a classic glass and polyester/vinylester resin laminate (hand lay-up)???????
In literature i found values of 28% using Chopped Strand Mat and 38% using Wave Roven or biaxial fabric; so 28% of total weigt is made by reinforcments fibers usind CSM.
some other following questions, maybe not so easy........
-are these vaules reliable???
-wich is the difference between a very carefully operated hand-layup and a "standard" one??? I mean: how much more resin can I squeeze out from laminate????
and the ultimate question:
-How much does vacuum bagging improve this ratios??????

thanks
Mistral

 

I had a similar question. here's the thread with some answers:

http://www.boatdesign.net/forums/showthread.php?t=4688&highlight=fibre content

 

ok, thanks Peter, that's what i was looking for; now let's see if some shipyard-guy will answer our questions with direct knowledge on the subject ; i need reliable numbers to calculate as exactly as i can a hull's weight. Few percentage points of difference mean a great amount of resin (and weight....)

fair wind
mistral

 

How critical is this weight? You could have the yard make a lay-up and do a burn test to determine the glass/resin ratio.

 

as a matter of fact i think that i'll build up some test-panel, 1 square meter sandwich, to have reliable results; the weight is not so much critical (the boat is not a racer), but it takes a slight difference in fiber/resin ratio to have 30kg weight difference in a 9m hull!!!!! Altough she's not a racer i prefer to employ weight in more useful way than adding a bunch of brittle unesuful resin to the hull

Mistral

 

It may be easier to use a better weave than to worry about the best ratio.

Unidirectional cloth will be about 60% fiber (weight).
Satin weave about 50%.
Plain weave about 40%