I was wondering what the 4 oz and 6 oz refers to when talking about fiberglass weights. Is it the weight of the cloth per yard or something like that?
weight per square yard, often rounded up (e.g. 3.7 ounce cloth is called 4 ounce for convenience)
You managed to answer 2 of my questions at once. I was looking at the Fiberglass supply site and I noticed all their glass was 3.7 oz. I figured it must be the same thing as 4 oz.
If I was trying to get a 1:1 ratio of resin to cloth would I use 3.7 oz of resin for each yard of 4 oz cloth?
Sure, if you were making a square surfboard…and didn’t drip any on the floor.
I’m nowhere near that precise, maybe Bert Burger can give you some tips here…
I’m pretty sure that I’ll miss the mark by a longshot, but I can dream… Thanks for the help!
i allways thought it refers to weight per square yard or meter ,6oz per yard is roughly 200gr per square metre but i bought some 1 oz cloth and that weighs nowhere near 1 oz per square yard more like 5 oz , if you compare it with 4 oz or 6 oz the 1 oz is a lot finer weave and there seems to be more glass fibres there so i am not sure now , the easy way of getting 1-1 ratio is to weigh out your cloth after you have cut out the board shape and mix up accordingly, i would mix a bit more than 1-1 because you allways lose some through drips or left behind in the pot ,you can acheive 1-1 quite easily on to the glass if you use a wet out sheet , but directly on to foam you will push a fair bit into the foam ,
i never used to bother weighing the cloth ,just used to mix up what i thought was enough but i have been using epoxy lately and it costs 4 times as much as polyester so i bought a cheap set of digital kitchen scales and thats probabally the easist way to go ,
the picture is the 1oz in the middle, 6oz on the right and 4 oz on the left,
that stuff in the middle looks alot heavier than 1oz …
it looks like a satin or twill weave 130 gram to me … cant be sure …
as far as resin ratios …
1 to 1 is only possible in a vac process , where you will be pressing laminates together or pressing the glass resin combo onto your board …
doing a hand lay up that light will leave it super dry …
regards
BERT
Hey Bert, I’ve got 2 questions for you:
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What is it about the vacuum that makes the difference in resin usage?
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I’ve heard that fiberglass is stonger when you have lower resin/glass ratios. I talked to the guy at Cerritos College and he seemed to think that even 1:1 is too high.
get a sponge and soak it in resin , then allow to dry …
it will be heavy as it holds many times its weight in resin …
now get another sponge same size , allow some resin into it maybe 1/4 of what the first sponge soaked up , now the sponge is not wet all the way through , it has dry spots , but now stack 5 bricks on it till resin squeezes out , allow to dry …
you now have 2 whole sponges with hard resin set in them , one should be about 1/3rd the weight of the other one …
unless your making bullet proof vests , your gonna need some resin …
1 to 1 is to high for what application ??
regards
BERT
He was showing me F14 jet parts. He might have been talking about those pre impregnated cloths.
One of the problems with resin infusion is making parts too fiber rich. Thought I would never say such a thing, but one thing to realize is in a lot of laminates you need a certain thickness to achieve a certain stiffness you desire. To do this at a lower cost it is much cheaper to make a laminate the same thickness out of a infused part at 63% glass versus 70% glass. Remember glass is twice the weight of resin volumetrically. What can happen if you have been wet laying up a part and you go to vacuum bagging (my case infusion) is if you use the wrong techniques or products you may need additional layers of glass to achieve the same thickness. Now you have a heavier laminate. I don’t know how this relates to bagging surfboards, I do know that I have used S-2 glass on boards with an untwisted weave, these boards dented much easier due to the lack of laminate thickness. Resin is very important in compression strength.
Prepreg Carbon Fiber Aerospace parts is a different issue.
Sluggo