Fibreglassing

[The Bear]

I need to make what can best be described as hatch covers for a couple of things in the garden, Basically a sheet of exterior ply with a lip. I want to waterproof the whole thing by covering in fibreglass.
(I have got a couple of other projects in mind involving fibreglass and this will be a good learning curve)

From the research I have done, sound like I need to use polyester resin and chopped strand mat to build up a couple of layers. I want them coloured.

Question I can't find the answer to is at the end can I just paint them the colour I want or do I have to use the coloured top coat (which as far as I can tell is just more polyester resin with a pigment added)
I'm thinking the topcoat way may be more hardwearing but want to way up my options (and the cost)

Any ideas?

Mark
(if this is not deemed woodworking enough can a mod move it to the general section)

 

[mahking51]

Generally paint on top of f/glass is not too good as there can be a waxy constituent to the top coat, much better to tint the gelcoat, very hardwearing indeed, can fade in the sun as any colour.
Just done my flat roof and it will be good for 30 years!
Cheers,
Martin

 

[jasonB]

A gel coat won't dry well as it should not be exposed to air when drying, thats why it goes against the mould and the matt on top. If not fully cured you can get styrene leaching out of the fibreglass.

The topcoat has wax in it which rises to the surface and seals out the air, it can be rinsed clean when the resin has set after a week or so.

You add the pigment to the topcoat and roll or brush it on.

Depending on the finish you want I would use a layer of matt, sand off any nibs, later of surface tissue, sand again then the topcoat

Have a read of the pond and roofing projects on this site, both use topcoat not Gel coat, they are good on delivery, I use them ouite a bit

http://www.ecfibreglasssupplies.co.uk/P ... fault.aspx


Jason

 

[MikeG.]

I was a fibreglass virgin until earlier this year, and was always worried by the process. However, one big and complicated moulded item later, I can confidently tell you that what you are proposing is going to be really easy. At least, it is easy to do a reasonably good job. It is much more difficult to get perfect than you would imagine.

The other thing to tell you is that the stuff, resin, matt, gel coat etc......is really expensive.

One little tip I can pass on is that if you do use a mould, do not wax it with a coloured wax....even if you put 10 layers of clear wax on top. My Saharan-sand coloured rooftent lid has pink blotches all over it where the dark brown wax reacted with something in the gel coat.

Mike

 

[Boatfixer]

I would do just as Jason said for this small job. Moulds and gelcoat are all very well for production runs but tend to take a lot of time to get right for a one off. The firm he linked to are very good at advising - they have their own moulding shop in the unit next door and all the staff are very helpful in my experience.

 

[LarryS.]

Generally paint on top of f/glass is not too good as there can be a waxy constituent to the top coat, much better to tint the gelcoat, very hardwearing indeed, can fade in the sun as any colour.
Just done my flat roof and it will be good for 30 years!
Cheers,
Martin

Martin, have you got any pics, looks like I am going to have to replace 2 flat roof in the next couple of months and fibre-glassing seems a good altentive to re-felting

thanks

 

[Niles Crane]

May or may not be relevent, but this guy made some fiberglass kayak paddles and put some patterns into the blades. If memory serves he refers elsewhere to putting tints into the final mix.

http://webspace.webring.com/people/ss/s ... blade.html

Hope it helps.

 

[ondablade]

A few more bits of input.

If you use a very coarse shop strand mat then as Jason says it's best to use a finishing layer of something like tissue mat or a much finer chop strand of a closer weave. Coarse chop strand takes huge amounts of resin that adds nothing structurally to fully fill - it's full of voids and you will inevitably end up with pin holes.

When mixing be very careful to add only juts the required amount of hardener. Even slightly too much and you'll end up dumping resin as it speeds it up no end. It's a catalytic cure system, so (unlike epoxy) more or less hardener speeds or slows the cure and gives good material.

Correct quantities of pigment are not so critical, but a good idea also.

Make a few trials with smallish amounts before you get more ambitious so you can figure a speed that suits.

When you wet the mat first with resin it won't want to lie down. Keep on going brushing resin over more of it. Return to what you did after about five minutes and you will find it's dissolved the binder and become nice and pliable.

Stop immediately and dump the leftover if it starts to go off on you - stringing is the first sign. Pushing on is a sure fire recipe for a crude looking mess.

Don't leave a large quantity to cure in a bucket, as it may overheat and go on fire.

Brushes and rollers are generally good for putting it down.

Acetone is the cleaning solvent for standard polyester resin.

Don't try to work in cold conditions, best above 60 deg F or you may have problems getting a good cure.

Make sure the substrate is suitable, maybe try a test. Polyester gases off styrene when curing, that's the smell. It'll strip some sorts of oil and cellulose based paints for example - especially if they are not long time dried.

There's a lot of GRP being used these days to seal wet rooms, or as a damp proof membrane behind showers. It's very possible there are resin systems available that are optimised for outdoor applications. Plus there must be some decent application manuals available from specialist suppliers... (i don't suppose the old Strand Glass is still on the go....)

ian

 

[Oryxdesign]

There is some useful info here
http://www.cfsnet.co.uk./

 

[would not]

I've got some chopped strand mat and surface tissue you can have for the cost of postage. I had my own business making fibreglass and carbon fibre stuff and have part rolls or material kicking about.

 

[cadders75]

I've done quite a bit of laminating and there are a couple of things you need to bear in mind before you laminate onto ply. you need to follow this list and you should get a decent result.

1. Acetone wipe the ply you will be laminating onto. Some ply has an oily surface that can lead to the GRP cap popping off and the acetone should remove most of it giving it better adhesion.

2. Prime the surface of the ply with the resin, this will also improve the adhesion and it will soak up quite a bit of resin, you don't have to wait for it to dry before you start laminating onto it.

3. For most Polyesters you use a 2.5 to 1 ratio of Resin to Glass weight, so a meter square piece of 450 gram chopped strand matt will use upto 1125 grams of resin. If you want to pigment the resin then you dont really want to use more than about 4% of the total resin weight of pigment in a laminating resin.

4. Paint Polyester resin onto the ply, leaving the surface wet with a decent layer of catalysed resin, then push the CSM (Chopped Strand Mat) into this resin, then paint on the resin onto the top of the CSM, the binder on the mat can take a while to soften so its best to wet it out as fast as possible. You then go over the wet CSM quickly in a "stippling" action to help the binder break down and drive some of the air out.

You then have to use a consolidation roller to compact the glass down and drive the trapped air out of the laminate, we recommend a fin roller for as it's better for driving air to the surface.

Until you are used to doing this I would not recommend laminating more than 1 layer at a time till you get the feel for it.

5. If your going to use a surface tissue you want anywhere between 5:1 up to 10:1 Resin to glass ration depending on the tissue type.

6. If you are going to paint a flowcoat on you want to use 450-600 G/m2 of flowcoat to achieve the correct thickness. An alternative to buying a specialist flowcoat you can use a standard polyester Gelcoat with 2% of a wax solution (Solution MW is the Scott Bader Manufacture) added to it by weight and mixed in well before the addition of catalyst. Make sure you get one that is suitable for exterior applications.

You probably will not be able to paint straight onto a flowcoated surface because the wax that stops air inhibition will stop the paint from sticking, you can however abrade the wax off with wet and dry and you should be able to paint onto the abraded surface after giving it an acetone wipe, but to be honest I would not recommend it as it never really looks as good or wears as well as a flowcoated surface.

Heres a couple of links to the sort of products you want to be using and a link to one of Scotts distributors which would give you an idea about the prices you will pay. Unfortunately Scotts no longer deal with cash sales

http://www.scottbader.com Resin manufacturers website

http://www.fiberglasssupplies.co.uk/ On of Scotts Distributors

Laminating resinhttp://www.scottbader.com/downloads/UK_PDF_Datasheet_Files/Resins & Compounds/2-8500PA - Mar 01.pdf

Flowcoat http://www.scottbader.com/downloads/UK_PDF_Datasheet_Files/Gelcoats/Topcoat 65PAX - nov07.pdf

Finally the type of roller you need to use to consolidate the laminate, clean it with acetone thoroughly after use or they start to seize uphttp://www.fiberglasssupplies.co.uk/acatalog/Fin_Rollers.html

Sorry for the small edition of War and Peace, it's not really as hard as it sounds

 

[The Bear]

Thanks to all who have replied so far, some useful info gleened but I need to study this against prices. I will have a look at all the links over the next few days, got a busy weekend planned.

Would not, thank you for your kind offer, I'd like to do that, again I will PM you over the next few days.

Having watched some guys a few years ago fibreglass my flat roof, I agree it looks easy to do an acceptable job but tricky to do a fantastic job. Hopefully I wont have too much to lose on this project.

I will report back when I've read everything

Mark

 

[would not]

Mark if you're going to fibreglass a roof get yourself some pre made edges, they are easier and make the job a lot quicker to do.
I've done loads of fibreglass flat roofs, you really need to wait for a dry few days that aren't too hot and not too humid. If it needs to be done urgently then I buy plastic roofing and plastic weld the joints, here again the edges can be bought pre made. I wouldn't even consider felt unless it's on a shed or rabbit hutch.

 

[The Bear]

Big thank you to Ian (Would Not) for the massive roll of chopped strand mat that he gave me and arrived today

Mark