Epoxy or Polyester Resin

[Erfolg]

I want to mould a GF UC for a model I am building.

I thought I would buy a small amount of Epoxy laminating Resin. It came as quite a surprise that even tiny amounts cost cira +£20.

I can buy a ready made one and pay the postage from HK at a lower cost.

I then looked up the cost of polyester resin from Halfords which I can buy for £5.

Is there any good reason not to use Polyester resin?

[Martin Harris - Moderator]

My understanding is that epoxy is stronger, more stable and less brittle. Full size gliders are (at least when I was involved) constructed using a polyester gel coat and epoxy for the structural laminations. The reason for that is if any significant movement occurs due to overstressing the structure - for example around the tail area from ground-looping - then the gel coat will crack as a telltale. There might be a weight difference too?

From the smell when I visited Carbon Copy a couple of times, polyester is used for at least some of their work...

Edited By Martin Harris on 07/12/2018 22:20:06

[Geoff S]

One reason could be smell. Polyester resin stinks the place out and, as my workshop adjoins the house my wife would certainly object.

I've been using WEST epoxy for many years, in fact it dates from when I was building a racing dinghy in the 1970s. A so-called minipack does actually cost a bit short of £20 but, in practice it lasts for years and you wouldn't use 25% of it to make an undercarriage. Epoxy is always considered the higher quality product and that's why I use it but I admit I don't know enough about chemistry etc to provide a reason.

Geoff

[flight1]

hi epoxy will give a lighter and stronger product see here for a general purpose laminating resin and i have found out it is very good a wetting out the cloth and nice to use. ( make sure you get the slow hardner as it gives you time to get it done)

Epoxy might be a bit more expensive but worth it . just remember when laminating just wet out the cloth don't try to 'fill' the weave first go , wait until it has gelled the do a flow cote which fills then weave and you can sand back this saves resin,and a stronger/lighter laminate is made.

Edited By flight1 on 07/12/2018 22:32:52

Edited By flight1 on 07/12/2018 22:34:12

[Alex Ferguson 2]

1.) Don't mix it up in a small "cup", spread it out or it will get hot and go hard before you are ready.

2.) Clean things with acetone if you must but white vinegar is far better. It breaks the parts down and is drinkable (before being used on epoxy).

3.) Any epoxy on the skin (yes, always wear gloves) should be washed off immediately with the white vinegar.

4.) Use the correct mix ratio and don't change it.

You can mix using proportions (volume) but I use scales. It is possible to buy digital scales to 0.1 gram reasonably cheaply.

Having used epoxy for decades and watched someone recently do it the wrong way as per (1), yes you can get things wrong. The dish I use for mixing is usually half a plastic milk bottle, cut top to bottom making a (2 per bottle) disposable tray.

I use epoxy for plywood sea kayaks. Coat it with something (paint) as UV will break it down or at least degrade it.

[Cuban8]

Hobbyking laminating epoxy is excellent and reasonably priced - never had a problem with it when glassing (US Bob Smith Industries product rebadged). Avoid polyester IMHO, it might be cheaper but it's truly evil stuff and should never be used in a home or garage without very efficient ventilation/masks etc.

My friend who used to make polyester glass fuselages for a kit manufacturer, seriously damaged the lining of his nasal passages and never recovered a proper sense of smell because of not having a properly ventilated workshop. Epoxy (as with poly) is nasty if you get it on your skin, but as far as I'm aware, is nowhere near as bad in terms of fumes and I've never noticed any ill efects from working with epoxy for many years, as long as you have at least some ventilation.

[Erfolg]

Cuban

I used to make fibre glass canoes in the 60-70s, with my wife, it did make a mess of her hair, I then found that the recommended rollers were much better. How times change, then there were no concerns about the fumes. You could buy resin, cloths etc by the shed load from "Strandglass", at what now appears to be very reasonable prices. I built a lot as a Slalom and white water canoeist, they got a bashing and had to be light weight to be competitive.

In the 70s you could buy Epoxy resin, which I used primarily for glass light weight clothed wings, at almost every street corner.

I guess it is the fact that there are a lot less industries that use the stuff now in the UK. As for health issues, if you did not die the next day, where is the problem?

I will now look at Hobbyking, it is a pity that i have just recently placed an order with them. It is the postage that is now the killer, particularly the UK. It has been cheaper to buy from the Dutch site, because of this.

[Martin McIntosh]

Don`t even think about polyester resin. It is for filling dents in cars,not for modelling. The setting time is much too quick and it is very brittle. I now only use epoxy from ABL (Stevens) resin and glass in Sandbach. www.resin-supplies.co.uk.

You need the multi purpose, not general purpose stuff, at around £30 for 1.5kg.

I use this for moulds and skinning. Best left for 48hrs before sanding.

[Erfolg]

Cuban

Is it the Tamiya resin that you are referencing. The reason I ask i cannot as yet find a Hobbyking resin.

[Don Fry]

And another killer is polyester has a short shelf life when opened. Epoxy lasts forever.

[John Duncker]

Using epoxy

Getting the right ratio is critical It may be different by weight or by volume. I have used graduated syringes and more recently electronic scales.

Understand the difference between laminating resin and finishing resin.

Do not thin it. If you want a runny consistancy warm the components before mixing.

The strength comes from the carbon fiber not the resin. Use just enough resin to fully wet out the tows.

Wear protective gloves.

Do not dry sand it NOT EVER.If you do you are likely to become sensitized and have severe allergic reactions to epoxy. Ask me how I know this.

[Erfolg]

Martin

Once upon a time Sandbach was pretty local, now it is 70 miles away.

Now being out in the sticks, knowing very few people, modeling supplies are a real problem I guess shades of things to come for many.

There is an irony in that Glasdon are about 3 miles away, unfortunately I do not know anybody who works there, I also suspect that all their products are made from Polyester Resin.

 

Edited By Erfolg on 08/12/2018 15:59:54

[Erfolg]

John

I almost agree with you, the strength comes from an ideal resin to fibre ratio. The problem really is with manual layup the matrix is almost always resin rich. Yet to get the ideal ratio, you pretty much need to vacuum bag, to force the resin into the weave, to get the ideal fill. Or use Prepreg.

Yet again all of this takes me back to student days, and crack propagation theory and how the stresses are dissipated. As a student I could not care less. As a youth, it seems an awful lot seemed boring, had to be learnt. The irony is for young engineers they were or are taught a lot, and nobody cares less. You then decide to make any money at all, it has to be management and forget engineering, other than they just make the world work.

[Steve Hargreaves - Moderator]

I've found these chaps very useful for composites Erf....resins & fibreglass in many different weights

+1 for the West epoxy resin too particularly the Mini packs & Junior packs. These can often be found in a marine chandlery as well....should be a few of those in your part of the world....

[Erfolg]

Now then Steve, these guys seem like the modern day Strandglass. The immediate problem with them is there are so many resin manufacturers, all seem to be similar prices.

As yet I have not found the P&P pricing structure.

I have now cast my mind back some 50 years and remembered there was a major supplier in Southport, which i can see a mere 2-3 miles away across the estuary. If it still exists it is another 30 mile journey, as I have to drive to the first bridge to cross over. If I could only remember the name.

A more important question does the Brown Parcel tape make a decent release surface? Or do I still have to paint my mould with resin, then wax and polish it a number of times.

Which has brought me to yet another issue, where is my tin of mould wax, and do I still have any PVA (the blue stuff) that is viable? Then there is my tiny slotted roller for GRP layups. Seems I need to go rooting in my garage just to find what I have and now need.

It seemed an easy trivial decision to make my own GRP UC, when I could not find what I wanted on the HK site.

Edited By Erfolg on 08/12/2018 16:58:42

[Steve Hargreaves - Moderator]

Strandglass....now there's a name from the past....i remember my Dad & Uncle buying many gallons of resin & hardener from them to make some canoes way back in the 70's....

Delivery costs are here....

And in response to your last thought is this not what we do? We are modellers & will spend far more on making our own widgets than buying one ready made....

[Steve Hargreaves - Moderator]

PS...is it Glasplies you were thinking of in Southport perhaps?

[Erfolg]

Yes it is, although looking them up, they now seem to have a pretty negative reputation.

You are correct, in that I probably spend more in building mainly from scratch. At best a kit, sometimes from a plan, finding it hard not to do a Vanwall, and think, you know, i can improve on that, fro my own perspective.

It is the fun. of doing your own thing, without thinking, is this potentially career limiting.

Sometimes the result of changes comes as a surprise. I produced a "V" tailed TH Cleansweep. On take of it was a pig, not responding to ruddervators. In the air great. I changed it to as designed, to find on the ground great, in the air not as forgiving. It is these experiments which pleases me the most.

[Stuart Z]

Just to add a supplier I find very useful and helpful when you call,

Bucks Composites, with lots of useful guides as well as tools to help you do a good job.

**LINK**

I have limited experience in the world of resins but find Bucks site very helpful and have helped me progress with jobs I have no experience of.

S

[Martin Dilly 1]

For what looks to me like by far the best range of resins, fabrics, mould releases, vacuum bagging stuff, tools and whatnot try:

https://www.r-g.de/en/home.html

That's R&G in Germany; I've often used them for carbon and hybrid Kevlar/carbon cloth and for laminating and mould resins in the past. Goodness knows what the prices would be like if/when the Brexit disaster happens, but presumably 20% v.a.t. will be added for a start, no doubt plus the 'handling charge' the Post Office, or whatever they're called this month, will put on top of that, so ordewring before March 29th might be wise. R&G supply the aerospace industry, but also the 'high end' of model flying. The website's well worth a look.

[Gary Murphy 1]

Sorry to side track but I was watching Sky and "how its made". The episode was the the making of a carbon/Kevlar canoe.

The factory/workshop looked pretty hi spec but the guys were pouring and scraping the resin into the cloth with no resperators / masks.

Is there resins that are not noxious? Know little about this,thanks

[Martin Harris - Moderator]

Posted by Martin Dilly 1 on 08/12/2018 22:04:16:

 

presumably 20% v.a.t. will be added for a start,

That's one way to look at things but surely the local VAT (19%?) has already been paid to the German tax authorities? I'm no expert on the taxation terms likely to be imposed as part of Theresa's "divorce terms" but it seems to me to be a 1% difference - and Germany has a below average VAT rate - which will surely make little difference to the overall cost of an item sold outside the EU which would normally be VAT exempt - while, if we continue to pay VAT, Purchase Tax or whatever, that amount will go into our government's coffers instead.

Edited By Martin Harris on 08/12/2018 23:31:54

[Cuban8]

Posted by Gary Murphy 1 on 08/12/2018 23:18:40:

Sorry to side track but I was watching Sky and "how its made". The episode was the the making of a carbon/Kevlar canoe.

The factory/workshop looked pretty hi spec but the guys were pouring and scraping the resin into the cloth with no resperators / masks.

Is there resins that are not noxious? Know little about this,thanks

I've seen that episode, and wondered the same thing. I can only surmise that they're using epoxy, which in my experience, doesn't have much effect as an airborne irritant (when wet) and they're relying on good ventilation. If it's polyester, then I don't hold out much hope for their long-term health prospects.

[Cuban8]

Posted by Martin Dilly 1 on 08/12/2018 22:04:16:

For what looks to me like by far the best range of resins, fabrics, mould releases, vacuum bagging stuff, tools and whatnot try:

https://www.r-g.de/en/home.html

That's R&G in Germany; I've often used them for carbon and hybrid Kevlar/carbon cloth and for laminating and mould resins in the past. Goodness knows what the prices would be like if/when the Brexit disaster happens, but presumably 20% v.a.t. will be added for a start, no doubt plus the 'handling charge' the Post Office, or whatever they're called this month, will put on top of that, so ordewring before March 29th might be wise. R&G supply the aerospace industry, but also the 'high end' of model flying. The website's well worth a look.

Martin, you have past form for making known your liking for the EU in a recent article in the BMFA mag. Not everyone shares your passion for things EU and I'd respectfully request that you refrain from using our forum as another political platform.

[flight1]

hi as for getting a supplier with model making in mind with a comprehensive stock and good delivery and prices.

I have bought a few things from them, like some nice fine 25g/m cloth for skinning, i have no ties to them but just found them to be good see lindinger model shop here to the right page