convert pvc roof to fiberglass?

[DeadRinger]

Originally Posted by MattC

Well,

Sorry,

I just wrote out the whole job and the site gliched and lost it all I won't have time to do it again.

Matt

bummer when that happens

[fishseeker]

Originally Posted by Cougarkid

Fishseeker,

So add a layer of mesh to the coating, make sure it is covered, and all is good?

Easy enough to do. Adds a bit to the cost, but not a deal killer.

You want to put down a layer of mat then cloth. Mat has fibers going every which way, cloth has squares. If I were to try something like this I would use Bi-Aixel 1708 that has mat roving and cloth all in one. Because once you start laying down the glass you don't want to stop. I wouldn't want try something as large as an RV roof and I know what I'm doing, for someone that has never done it, it will go bad for them in a heart beat.

[Huey]

I'm pretty sure the last layer before the gelcoat should be matt because the pattern will show through on cloth.

[fishseeker]

You don't want to use Mat as a last layer. It balls up some as you roll out air bubbles (which is an important step) fine mesh roving is easier to sand smooth, that is why I mentioned 1708 Bi-ax. The top layer is fime mesh boat cloth. Sanding its something your going to do a lot of trying this kind of repair. And Itching. like is said I wouldn't try it.

[MattC]

Eagleman,

I got stuck between cures so I took the time to write it up again. This time in a text editor, so it could drop me....

Reading the other posts...
Stay away from mat.. Mat needs the acetone that is in a polyester resin to dissolve the binder. That binder will prevent a bond with epoxy.

The 1708 stitched bi-ax that fishseeker noted is great material for building the weight and strength of a section, but you should not need it. It also eats resin. Great for the strength he need for a drift boat, but not what you need for a coach roof.

Stay away from polyester resins. I have used polyester, vinylester and epoxy. And unless you have the mixing and handling equipment, the chance of a bad mix with any ester (have a ratio 32~64:1) is real good. They are very mix ratio sensitive. Epoxy (uses ratio 4~5:1) is not nearly as fussy. If you miss an ester by 5%, it will either set up before you finish mixing or never cure at all. Epoxy can miss by 10% and it will cure to nearly full strength.

The write up - if you have questions, come back.

Doing the coach roof.

This is assuming that you have effective weight bearing structure to work on.
You will have to prepare and be ready to deal with any epoxy that leaks through into the interior.
This is the way I have done to replace the canvas and paint coach roofs on the cabin trunks of several custom built cruising boats .

First => Get the books on fiber glass work that the are published buy West systems. They can be downloaded at their website. West Systems is no part of West Marine. Many years ago the Gougeon brothers were building boats with epoxy and found that none available were all that satisfactory for boat building, so they started formulating their own. This is exactly the sort of thing that they were working on.

I don’t know where you are so I cannot even begin to recommend suppliers to work with, but the web is full of them. You will find lots of people willing to make a deal, but don’t get fooled into trying to save 50~100$us on a job that would cost 6~10k$ to buy.

If I were being asked to quote this job (I have not seen it). I would quote it as four passes with a crew of 4 men. We would lay down two layers of glass, a layer of fill and the then a finish.

You will need several gallons of epoxy/hardener resin and the measuring pumps (essential).
Roof area plus 10% of a 4oz cloth that is either a twill or a satin weave. This is important. You do not want standard roving as it will be too rough to even make a good surface.
The same amount of 1~1.5oz “fine glass” this stuff looks and feels like silk. It will give you an almost usable finish.
Several pounds of light filler - either glass balloons or styrene spheres - it makes no difference. I would go with the glass, but it might require an extra coating of epoxy.
A good marine finish polyurethane like Awlgrip or Imron to be a UV barrier.
Of course you will also need brushes, rollers, saturating rollers, squeegies, gloves (lots of gloves), vinegar for clean up (works for West), and real carbon filter masks if you are working inside. You should also have two pairs of shears. One big beautiful expensive pair for cutting the glass to size and one (maybe more) throw away wet shears and we will get to them later.
Different thing! You will want to have a thick coating tool. This is a linoleum glue spreader (toothed trowel) or the similar tool from West.
Make a table with whole (probably 3) sheets of plywood (cheap) on 2*6s and saw horses. It needs to be large enough to lay out and cut the working panels of glass fabric. Cover the table with a layer of heavy plastic so the cheap wood can’t snag the fabric. Do not try to cut all the panels in advance.
Have lots of ladders and staging on hand because most of this operation will be conducted on the coach roof.
Note: I have probably left out some number of things I always have and so you will have to thinks this trough very carefully. *** Like mixing cups and stirrers....

Start the job by removing everything that can be from the roof. You will have to plan to cut the fabric to go around what cannot be removed.

The Process:
The crew is four - Two on the roof, a mixer and an cutter. All should be gloved (and masked). One of the two on the ground should be detailed to stay dry. Everybody’s hands will be sticky in short order, but the dry guy should be ready to reglove as soon as he gets fouled.

Start by inspecting and smoothing and filling the base material surface. You will be applying an expensive four layers that will have difficulty hiding flaws.

With the crew in place and before the first mix, cut one panel and pass it up to the roof and practice, wetting, coating, saturating all while unrolling that first panel. Make this dry run as real and complete as possible.
Do that until you are very comfortable. You will not be able to stop the process one it starts without a large loss of material and time.
Now, roll that panel back up and pass it back down.
Do a first mix, do not let the mixer short the stirring time. In just a few go-arounds, you will get the plan how many pumps of mix and when can be started to stay with the demand.
Put a wet coat about a foot wide on the base and pass the panel back up. Lay the panel up and line up the starting edge.
Now, wet out the fabric, use the saturating rollers to get the bubbles out of the fabric and use the squeegies to pull any excess resin along. Resin adds no strength, it is only there to stick the glass down and make it water proof (why bubbles are bad).
When the first panel is laid, decide if you can butt or if you have to cut the splice (you should have read about this in the West publications).
Once you get started on the next panel, one of the crew can take the wet shears and clean the edge of the first panel. He cannot do this while you are working the panel.
Once you are done with the first layer, you have to wait for full cure. The last cup of mix is handy for this.

The surface should again be inspected and repaired as required.
The surface will have to be washed with soap and water to remove a film that is the result of the chemical processes in the curing of epoxy. This film can inhibit a bond with the subsequent layer.

Same Game.... Do the fine glass layer. This is usually easier. Butting the panels is usually good because the fabric is sooo fine.

It will look great, but if you paint that with the good urethane, it will hold dirt like you would not believe. So, wash it again.

Now your mixer gets to go crazy. You need clear resin to wet the surface and then filled resin to put over that to make a flat surface. You do this with the thick material spreader (a fine one) to put down a constant amount of filled epoxy and then smooth it out carefully with squeegies.

When that is fully cured. Do a light sand on it and paint it with the UV barrier. That may take two or more coats and then you can put all the stuff back on the roof.

Now do you know why a good job would be expensive?

[wickedrevs 56]

An alternative to fiberglass would be an EPDM (rubber) that you can roller application. Check out "Liquid Roof", we use it all the time for old worn out RV roofs. It is without doubt the best way to seal your RV.

[PeterS]

It's not as complicated as waterman explains, but it is smelly and messy! You will need disposable gloves, brushes, paper bowls and shirts (lots). A scaffold helps. I also made formed fiberglass edges so I could mold the top onto the body. If you do this be very precise when gluing the edge. I wasn't and had to hide all the ugly with diamond plate. Lose the ladder and the luggage rack. I also added 1/2" standoffs. No screws penetrate my roof skin. Two hurricanes, no leaks. It won't be flat, but it's solid, repairable and only birds will see it!

[Cougarkid]

PeterS,

That's what I'm talking about. Looks good.

The standoffs at the openings are a real plus. Water doesn't like to go uphill.

What did you use for the final covering?

[PeterS]

I used three layers of half ounce fiber glass cloth. I got a big roll on ebay cheap. What I saved in money I paid for in labor. I had to put on three coats, it was way too light! Also I didn't design the stand-offs well enough. The corner between the fridge vent (why is this on the roof?) and the bath sky light (Mines now lexan) collects leaves. pics of crappy roof edge, most of the lumps ground off. I then injected foam for strength and covered with diamond plate (for fun) I used Bondo resin from HD.