pyramid roof-final part--or fibre glass is a pain in the ---- but cheap

Did you have to incorporate thermal expansion sections ? and what is the colour of the gel coat? Tom

Can be any colour you like, though it's probably wise not to choose black - the roof will probably get a bit hotter than white.

No expansion sections although the pyramid is free to expand and contract as it is raised on a 600mm high upstand the perimeter drain similarly can move horizontally.

and what is the

Gel coat comes in standard grey which suited me as it matches zinc. There is a bewildering choice of many shades-at least 30.

Any chance of some photos? It sounds like a very interesting building ! Yours interestedly, Simon.

And you can get process colours - Cyan, Magenta, Yellow, and Black. From which you can make any colour you like.

Gel coat comes in standard grey which suited me as it matches zinc.

Gel coat should be applied no thicker than 1/2kilo per square metre it contains wax so once its on you cannot bond to it so you need to grind back to the base coat. Gel should go on when base coat is just set-but-I had to overcoat some bits

The wax floats to the top of the basecoat, and forms a skin. This leaves you with a wax skin over the fiberglass, which excludes water, and lets the fiberglass set. In damp weather especially, fiberglass doesn't set all the way up to the top, and goes sticky without a gelcoat.

You can clean off the wax, and bond to this, in theory, but it's problematic. An excellent tool for cleaning off the gelcoat is one of those carbide donut thingys that fits onto an angle grinder. And a breathing mask, or something.

Does it have to be applied as a sheet, or could it be dotted on with a small brush?

I was just thinking of a self-coloured fibreglass roof mural. Or, as it's approaching that time of year, internally-illuminated 8' high reindeer.

Owain

It's basically like painting with thick honey.

That gradually, over the period of a few minutes to hours sets. You can in principle colour any part of the fiberglass, however, I'd start with laying up the glassfiber sheet in clear, and then a white layer to keep the UV out of the middle layers, where it's not wanted (UV causes yellowing, and eventual failure). Then paint with pigmented resin a design, followed up by clear gelcoat once it sets.

(My fiberglass experience is limited to repair, and putting on black gelcoat to an already existing fiberglass pond liner - it's still there several years later, as good as it looked at first)

So it would come out a bit impressionistic?

I think that could be kewl - stained glass for the 21st century.

Owain

For making any structure like a reindeer-tank-spitfire-santa-ice cream van-that would be an interesting roof ornament--you would need a very different resin from roofing resin. Roof type never gets glass hard and its got uv resistance. Usually for structures you use polyester resin and in terms of cost-chopped strand matt up to 600 gram per square metre-woven roving is next up in cost. In summer you wont get much more than one hour usage of resin-in my experience 20 minutes is about it. Brushing resin is pretty useless as the resin must be forced into the matt hence rollers. I built a recumbent trike from glass reinforced plastic using woven roving and epoxy resin. It has suspension all round 63 gears and folds used it for 15000 miles so far all over Europe-so GRP is serious stuff. Quite happy to email pics of the trike in action---oops strayed far from the pyramids.

On your blueyonder webspace.

I wouldn't dream of trying to wet out the matt with a brush, a roller must be used of course.

However, once a smooth surface is obtained, you can then paint on it with gelcoat quite easily.

The gelcoat won't set if its exposed to the air and will forever remain tacky and prone to damage.

Applied to a mould and then overcoated by a conventional resin and mat layup its not a problem, but if its used as a top coat, and not formulated as such, then you need to add a specified wax solution (available from most resin suppliers) to make it go off.

True, I was assuming a gelcoat with wax added, sorry.

Well, it is runny enough that it will smooth out, unless you paint it on just before it sets in the very hot.