Fiberglassing the roof: advice?

[alistair]

So it suddenly occurred to me that we have long Easter weekend coming up and I had intended to fibreglass the roof of my TARDIS observatory this spring to hopefully stop it leaking (it's had a tarpaulin over it for the last couple of months which keeps the telescope dry but spoils the look somewhat).

Looking at a couple of youtube videos (https://www.youtube.com/watch?v=9jHUI0CiYbs) showing fibreglassing onto plywood, they seem to advise:

1. paint on a couple of layers of resin (without hardener?) until the wood stops soaking it all up
2. a 'bead' of resin & chopped strand mixture at the bottom of each 'step' in the roof to round-off the 90 degree angle
3. Chopped strand strips along all the edges and corners
4. overlapping sections of chopped strand to cover the whole area
5. overlapping sections of woven cloth to cover the whole area

Here's another one giving a slightly different sequence (all chop-strand, with gel coat and 'flow' coat): https://www.youtube.com/watch?v=TzkWeuC0yPs
And another: https://www.youtube.com/watch?v=LhWud4a5Aj8

Does this seem reasonable? Are they overkill? Does anyone have any further advice?

Looking at these, I think I will actually need to do some more prep before embarking on this. Maybe I should wait until the summer when we have moved and settled in to our new house!

[Volpone]

No idea.  I know some people have done fiberglass roofs, but I'll be deuced if I can remember who.  Goldendale?  I know there is more than one. 

[russellsuthern]

Fibre glassing has always been a blind spot for me, I've never done it...

But there is one thing I can say with certainty...

If it is an outside build, where weatherproofing is concerned, there is no such thing as overkill....


Good luck.


Russell

[brenk9carter]

I had my roof fibreglassed over by a professional, it's really helped withstand the bipolar weather here in sunny/rainy Britain, if you can do it then definetly go for it as it will really help your build last longer. Just be prepared for mess and itches 

[galacticprobe]

I had my roof fibreglassed over by a professional...

And if this is an affordable option, I would go for it. Nothing looks better, or lasts longer, that something done by a professional. (And it's less of a hassle for you.)

Just be prepared for mess and itches  

And stink! Don't forget the stink! If you do decide to fiberglas the roof yourself, make sure you do it where there is plenty of ventilation. The curing resin puts off huge amounts of fumes which are toxic. If you can't do this outside, or in a garage with the doors wide open, then make sure to get yourself one of those filter masks specifically designed for fumes - not one of those fuzzy, cloth-like things with rubber bands that snap around your head or ears you'd use when sanding things; fumes will pass right through those.

When in doubt, go to a home improvement store and ask. Let them know what you're doing (fiberglas work) and that you need an appropriate filter mask while you're working.

Number 7 of http://tardisbuilders.com/index.php?topic=8252.0.

Dino.

[Bob's your Uncle]

When I finished fiber-glassing the roof of my TARDIS, I swore I would never touch fiberglass again. In hindsight, I'm glad I did it.

http://tardisbuilders.com/index.php?topic=6434.30

After two winters outside, the roof is still holding up very well. No leaks, no cracks.
If you don't mix the resin and the hardener in just the right proportions it can harden too fast or too slow.
Too slow in my case, I had to wait two or three days between coats for the fiberglass to dry completely.
I applied three coats just because I had a hard time getting the first two coats smooth enough.

Good luck.
Greg.

[galacticprobe]

If you don't mix the resin and the hardener in just the right proportions it can harden too fast or too slow.

Adding a little to this... having the fibreglas cure a bit slow isn't that bad if you've got the time to wait, provided, that is, it does cure completely. I've gone both ends of this spectrum years ago when I had access to fibreglas resin and cloth, and loads of RTV (Room Temperature Vulcanizing) Rubber tubes. I could make moulds of model parts with the RTV, and them mix fibreglas resin and cloth to cast clear(ish) parts for the models.

My worst in both ends: the main deflector of the refit Enterprise from ST: TMP. It came with a light kit - which I modified by adding a couple of flashlight bulbs to. I put one in the Main Hull (a.k.a. "saucer" from TNG terminology), and one in the Secondary Hull (the part that has the neck and warp engines). The kit came with little grain of wheat bulbs for lighting the windows in the Primary Hull, and that was it: not satisfactory for me. So, I added more lights, and that bulb in the Primary Hull was centered so well the light came through the ports below the bridge and above the lower sensor dome so well it looked just like it did in the film. So... where am I going with this? (I'm glad you asked. )

With the light in the Secondary Hull just barely shining through the deflector array (and the thin coat of blue paint on it), I decided to cast a "clear" part for that. First try didn't go so well; the hardener to resin mix wasn't quite right and the stuff never set up. It stayed pliable... and somewhat sticky. (That one went into the bin.)

The second try wasn't much better: a bit too much hardener. It hardened so quickly that it put off enough heat to start crackling and popping... and putting off smoke! (You want to talk about stink! As Bugs Bunny would say: "Eeee-whooozh!") I needed oven mitts to pop that thing out of the mould and toss it outside on the cement porch until it finished its reaction.

Moral of the story: use special care when mixing things (and also remember to wear eye-protection; one splash could be disastrous!). Also read the instructions. Usually the instructions on the kits say it's a one-to-one mix ratio; but when you've got a gallon can of resin and a tube of hardener the size of your thumb, unless you're a mathematical whiz (which I'm not) it's not easy to get that ratio right... unless you're using the lot in which case the whole gallon of resin will take the entire tube of hardener. And ambient temp and humidity have an effect on how long things will take to completely cure even if you do get the mix right first time.

So go it slow, and ask around among your friends and trustworthy neighbors if you're not sure. Someone's bound to have done some fibreglas work before and could lend you a hand if you want to try doing it yourself.

I hope some of this rambling was helpful.

Dino.
P. S. About that deflector array I was casting. I finally got things mixed just right, with the right amount of cut-up cloth mixed in for strength. However... (there's always a 'however' with these things, isn't there?) I found out the fibreglas part didn't have the flex of the original plastic part when it came to popping it in and out to change the batteries, and the "latch tabs" snapped off. It looked great while it lasted, but I didn't feel like hassling with that again. (And then some moronic workman destroyed my model after my wife warned him to wait until she moved it out of the way before he started. He didn't wait. After the destruction she advised him to leave the house before I got home - smart move on her part - and we found another, more careful workman.)

[alistair]

Thanks for all this advice guys, very helpful. Well the tarpaulin came off yesterday and I had a proper look at the roof...

I plan to whip it off this weekend, replace it with a plain sheet of plywood and put the tarp back on. Then I can take my time tidying it up, putting another step in it and some corner pieces, before I start on the fiberglass.

I have done a little fiberglassing in the past: last year I did repairs on the canoes that are hanging on the fence, so I have some practice with mixing hardener, resin etc but have not attempted anything this complicated. The new house has a workshed for it to cure in but I expect to do most of it outside.

I've not done anything with colour before though. do you add colour to every layer or just to the top one?

[Volpone]

Again, as a total novice, I'd probably just paint it after the fact.  It wouldn't occur to me to embed the color.  But if it isn't hard to do, I'd probably do the top layer.

[Bob's your Uncle]

After sanding the final coat of fiberglass, I used regular exterior paint and primer.
I can see that you would save on paint by pre-coloring the fiberglass.

Greg.