The age old question;
if I want to fibreglass a few bits and pieces of ply to my polyester hull (which will be well sanded down to the bare fibreglass) should I use epoxy resin or polyester resin. The finish is not important and I don't mind if one is more expensive.
Epoxy. Epoxy sticks to just about everything. Longer working time so there is no rush if your working in a confined space. Virtually no fumes. I think it's cheaper to use than fibreglass resin because there is virtually no waste. Use the same epoxy with various fillers for fillers and glue. Downside is it needs to have a coat of paint. Buy it from the Fibreglass place opposite the old Motor Registry in Flinders estate. You will need a digital kitchen scale and a jewellers scale if you want small mixes.
Select to expand quoteRamona said..
You will need a digital kitchen scale and a jewellers scale if you want small mixes.
Or just use 12cc to 60cc syringes for small amounts.
Totally reusable and real handy for epoxy and 2pak paint.
Another vote here for epoxy, it doesn't stick to some plastics, which is handy, if you need to form anything up.
only needs painting if it's going to be used in an exterior application.
try to wear nitrile gloves.
wash your hands with white vinegar if you get any on them, and any tools in metho.
cheers
I would go with epoxy as well, as mentioned no fumes & longer working times, higher bond strength. They only time polyester wins in my opinion is ease of fibre consolidation
great advice thanks, I suspected epoxy was the way to go but just wanted to check because a friend of mine that used to build wooden boats was convinced polyester was way to go.
Polyester does not stick to wood all that well. High resin woods particularly. Water gets behind the lay up and the whole lot will separate. Epoxy sticks well to most plastics, particularly if you abraid the surface. I built a dinghy years ago with a perspex bottom so light could show through. Roughed up the edge 40mm all round the edges. I have built dinghies with tape and polyester resin on the chines and one dinghy full polyester over a foam core, I was not concerned with weight. I could have used epoxy and it would have been half the weight but very expensive. Now epoxy is very cheap and I would not bother with polyester.
I'm an epoxy person too for its sticking properties.
But I do need to challenge the "no fumes" statements. It may not smell, but breathing its fumes is way way worse than polyester; especially in an enclosed space. Essentially it corrodes your lungs. Do it enough and you will suffer holes in them and a collapsed lung. Google "Epoxy resin lung"
It is worse if you are in an enclosed, or heated space and if sanding partly cured epoxy
polyester is for swing pools eskies and things that dont matter and where price is a concern vynlester for boats and structural layups things that need gelcoat and tanks epoxy for repairs timber or any high load or quality jobs
at our yard we barely get through a 200 liter drum of poly before it goes off but are always running out of epoxys the real decision is which epoxy or glue you should use as the variety of resins is massive
Epoxies are the way to go
shelf life of poly 6mths max and epoxy 2 years and longer if not worried about the colour change in the hardener.
www.sanded.com.au/pages/surfset-resins
Select to expand quoteTamble said..
I'm an epoxy person too for its sticking properties.
But I do need to challenge the "no fumes" statements. It may not smell, but breathing its fumes is way way worse than polyester; especially in an enclosed space. Essentially it corrodes your lungs. Do it enough and you will suffer holes in them and a collapsed lung. Google "Epoxy resin lung"
It is worse if you are in an enclosed, or heated space and if sanding partly cured epoxy
thats interesting , about epoxy being bad to breath . Ask any old surf board glasser how bad polyester is !!! its really bad for you to breath !
so i guess fresh air is the go .
Select to expand quoteRamona said..
Polyester does not stick to wood all that well. High resin woods particularly. Water gets behind the lay up and the whole lot will separate. Epoxy sticks well to most plastics, particularly if you abraid the surface. I built a dinghy years ago with a perspex bottom so light could show through. Roughed up the edge 40mm all round the edges. I have built dinghies with tape and polyester resin on the chines and one dinghy full polyester over a foam core, I was not concerned with weight. I could have used epoxy and it would have been half the weight but very expensive. Now epoxy is very cheap and I would not bother with polyester.
It is possible to make polyester stick to plywood just as well as epoxy. Just a few tricks involved.
When I was in Fiji I looked over a 25 year old Wharram that had a full polyester external laminate (over ply) . It was in great condition.
Select to expand quoteRamona said..
Polyester gives you really bad breath!
..and vinylester as well. It's the styrene fumes.
Select to expand quotepsychomub said..
It is possible to make polyester stick to plywood just as well as epoxy. Just a few tricks involved.
Sounds encouraging, Psyco - any chance you could share those "few tricks"?
My experience of resin to plywood bond has been poor - if exposed directly to sun and water, and if the wood piece is NOT 100% sealed against moisture uptake, the wood will expand and contract with sun and cold, and cycle between damp and dry - but the hard resin layer will not breathe in sympathy and separate from the wood after a few seasons.
Select to expand quoteKarsten said..psychomub said..
It is possible to make polyester stick to plywood just as well as epoxy. Just a few tricks involved.
Sounds encouraging, Psyco - any chance you could share those "few tricks"?
My experience of resin to plywood bond has been poor - if exposed directly to sun and water, and if the wood piece is NOT 100% sealed against moisture uptake, the wood will expand and contract with sun and cold, and cycle between damp and dry - but the hard resin layer will not breathe in sympathy and separate from the wood after a few seasons.
Basic method:
Key up ply with grinder or course sandpaper.
Mix polyester and acetone togeter in a 4:1 ratio to give a very thin resin. If anyone tells you to thin with styrene , ignore them.
Add Cobalt napthanate accelerator @ 4%.
MIX COBALT IN WELL. If you don't, when it comes into contact with MEKP, you will get a surprise.
Catalyze with MEKP @ 4%.
Brush/roll it on quickly. It will soak into the timber and the acetone will gas off.
Wait till surface is touch dry, then proceed with polyester laminate.
BTW , epoxy encapsulated boats also have major issues. The industry standad was external glassing, then a couple of coats of epoxy inside. All good until you get some damage or an incorrectly bedded fastening. The moisture that gets in now has no escape route, so rot is guaranteed.
