Resin:glass fibre ratio

[Romany 163]

 I've been advised by the product supplier (not a Burnsco/NZ Fibreglass type retailer) that the ratio is roughly 1:1 ;I.e. resin weight/m2 = matting weight - so, using 290gsm woven cloth u would expect to use approx same in mixed resin per m2. 

Maybe a liddle bit more to account for soakage, but user based f*ck ups like leaving it in the sun. Doh.

Last week i did some glass on my cockpit floor, which has had the old cork/resin non skid over the top of glass sanded right back to almost fly sh*t thickness, and allowing for the solar issue, I reckon i used 1.5 times that weight of resin.

Theories being good and all that, does anybody have an opinion to offer which is based on practical experience?

[Psyche 807]

When I do wet epoxy layups I weigh the cloth and mix up the same weight of resin, and it works out as a pretty good rule of thumb to avoid wastage and get good coverage etc. Generally you want less resin more (fully wetted)glass. Using more resin is expensive and doesnt add strength, but on a cockpit floor it doesnt matter 

[alibaba 84]

I can supply some information here, as my son did an experiment as part of a class Science project. He used West System, which is nominally 5:1 ratio of resin to hardener. He then glued standard butt joints together with varying mixes, ranging from 1:1 to 10:1 ratios, and then measured the breaking point of the joints.

To my surprise, there was little difference until the ratios were well away from the norm. All joints from 3:1 to 8:1 were of equivalent strength. I think that there is a fair amount of leeway built in for us.

Of course, I have no idea how the ratios would pan out over time or indeed with exposure to the elements, particularly u/v.

I don't think you should be too concerned if you are slightly out.

[Gappy 9]

1 hour ago, alibaba said:

I can supply some information here, as my son did an experiment as part of a class Science project. He used West System, which is nominally 5:1 ratio of resin to hardener. He then glued standard butt joints together with varying mixes, ranging from 1:1 to 10:1 ratios, and then measured the breaking point of the joints.

To my surprise, there was little difference until the ratios were well away from the norm. All joints from 3:1 to 8:1 were of equivalent strength. I think that there is a fair amount of leeway built in for us.

Of course, I have no idea how the ratios would pan out over time or indeed with exposure to the elements, particularly u/v.

I don't think you should be too concerned if you are slightly out.

Sorry It's not what he's talking about he's talking about once the resin is mixed is the weight ratio of resin to glass so if you have one square meter of 200gram glass you should use around 200grams of resin. 

But if you are using chopstrand that ratio doubles the 1 to 1 ratio tends to only apply to woven and double bias clothes.

[Romany 163]

Thanks for replies. Yesterday i did more and 1:1 is about right so I'm going with beginners luck or lack thereof, as the reason i used too much.

Another question for those of u who know... i watched a boat builder who is working elsewhere in the yard, and was intrigued/impressed to see him do a fibreglass layer on now ply, and then 2 or 3 hours later apply fairing to that same area.. no sanding! That made sense to me cos it seems that freshly laid fibreglass prior to final cure is the ultimate surface to receive fairing. Is that common practice or just a cunning old fox at work?

[Romany 163]

..new ply...

[Ex Machina 390]

9 hours ago, Guest said:

Btw,CHopped strand is for swimming pools and compost bins….

 

And Aussies 

[Psyche 807]

You want to see the weave on the glass, a beginners mistake is to try and fill it with resin or make it look smooth. As mentioned try and use peel ply as much as possible.  When I havent used peel ply, as soon as its gone off enough not to move around, Ive faired it because it saves time and no blush issues.

[Romany 163]

Oh well i better bust out my 16 grit discs

[waikiore 484]

Guest has nailed it and unless in very moist/cold conditions you can fair as Psyche says.

[SloopJohnB 329]

Something buried deep in my computer.

[aardvarkash10 1,105]

11 hours ago, SloopJohnB said:

Something buried deep in my computer.

pounds feet and inches!

Was the original on papyrus?

[waikiore 484]

It is still that way across the pacific.....

[SloopJohnB 329]

That's why I said I had to dig deep into the computer, sorry the human memory banks can't remember where I found this information.......... but yes I can still remember ft &  ins and pds even pennies, shillings and pounds.