Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => GRP & Epoxy => Topic started by: Tug Fanatic on May 05, 2019, 03:00:52 PM

Title: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: Tug Fanatic on May 05, 2019, 03:00:52 PM
I have looked at Bucks Composite, East Coast Fibreglass etc & have come across terms like "laminating resin", "finishing resin" and "general purpose resin" which are unfamiliar to me.
Are epoxy resins essentially the same but with different speed hardeners & fillers to make the different types or are they actually different? I have in the past made West System do it all except very quick setting so will the same apply to all well known marine brands?


 
Title: Re: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: DaveM on May 05, 2019, 05:35:42 PM
I'm pretty sure that the finishing resins sold for models must have some sort of filler medium which makes them easy to sand smooth. I've sanded down a glassed hull just this morning and finished up looking like the victim of an explosion in a flour mill!

I use slightly thinned Z-Poxy Finishing Resin for that purpose, although I've recently been given a pack of De Luxe Materials' Aeropoxy to try. No doubt your marine suppliers will have something very much akin to these but probably in larger quantities and almost certainly for a lot less per Kg! That's fine if you use a lot of the stuff quickly, but I find its shelf-life limits me buying in such quantities.
DaveM
Title: Re: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: JimG on May 05, 2019, 06:22:37 PM
I think that one of the main differences is that finishing resin will completely harden on the surface when exposed to air and shouldn't be sticky. Laminating resin tends to stay sticky for longer to help keep the next layer of glass cloth in place. I think finishing resin may contain some wax to stop the surface going sticky., this should be sanded off before adding another layer of resin. No need for any filler in both cases.
Jim
Title: Re: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: Mark T on May 05, 2019, 06:37:04 PM
I remember sanding down a hull with finishing resin and looked at the lack of mess and dust around me - I was really impressed as I did this in our dining room.  I then stood up and saw that everything and I mean everything was completely covered in a fine white dust  :embarrassed:   I was in serious trouble as it took ages to clean up so I guessed that finishing epoxy is both harder and lighter than standard epoxy.  Lesson learnt - do this when the wife is out for a considerable amount of time.
Title: Re: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: derekwarner on May 05, 2019, 11:07:17 PM
Many many years ago [maybe 48? years ago], I was about to glass my first, a 6 foot long hull so went to a local Advanced Fiber Glass Technologies [type name] distributor & asked if "laminating resin", "finishing resin" and "general purpose resin  would be best for my application

The response was a little surprising....."mate ..we don't recommend anything....you tell us what you want & we sell it to you"

So not to be outdone I thought a surfboard manufacturer would surely know....so we to a local Surfboard Shop....a group of Surfies were just hanging around listening to Jimi Hendrix & the shop had a distinct odor of burnt agricultural matter

I asked the same question & the response was ....."man...we don't know.....we just open the tins & pour & mix the resin goop".......

Derek
Title: Re: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: JimG on May 06, 2019, 11:42:03 AM
I remember sanding down a hull with finishing resin and looked at the lack of mess and dust around me - I was really impressed as I did this in our dining room.  I then stood up and saw that everything and I mean everything was completely covered in a fine white dust  :embarrassed:   I was in serious trouble as it took ages to clean up so I guessed that finishing epoxy is both harder and lighter than standard epoxy.  Lesson learnt - do this when the wife is out for a considerable amount of time.
I find that epoxy is best wet sanded starting with coarse wet and dry paper working down to fine. No dust and it washes off while sanding. More akward for large objects as it needs something to collect the water running off. I did once use the bath to sand down the booms on a model jet.
Jim
Title: Re: Epoxy Resins - Laminating, Finishing, General Purpose etc Difference?
Post by: Tug Fanatic on May 06, 2019, 03:10:30 PM
I think that one of the main differences is that finishing resin will completely harden on the surface when exposed to air and shouldn't be sticky. Laminating resin tends to stay sticky for longer to help keep the next layer of glass cloth in place. I think finishing resin may contain some wax to stop the surface going sticky., this should be sanded off before adding another layer of resin. No need for any filler in both cases.
Jim

Isn't this about Polyester resin where the non waxed laminating resin never completely becomes non tacky unless it is barriered from the atmosphere? Hence the wax which forms the barrier in finishing polyester resin which achieves this.

In epoxies I have always regarded the wax as a problem which needs removing before another coat of epoxy can be applied if the last has been left long enough for the wax layer to form. I have heard of some new epoxies which don't have the same problem.

Thanks for the ideas on the finishing epoxy resin. Sounds totally sensible!