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Old 08-17-2022, 05:22 PM   #1
Mini-Skoolie
 
Join Date: Jul 2022
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Question Repairing leaks in fiberglass roof

Hi. I am brand new to all this, having just bought a shuttle bus to convert for use as a camper now and eventually a (very) tiny home out in the desert. I discovered a hole about 3x6” on my roof, which is fiberglass. There is also a slightly leaky area in another part of the roof, and water is seeping in at the bottom of some of the windows. There are no visible holes on the roof beyond the one up front, but it’s near the factory-installed AC roof mounted unit, so that may be the source. I need advice about the best way to patch the hole, as well as to address the leaky spots. Also, must I coat the roof in toto with something like Henry’s alkyd sealer or Tropicool? I live in the desert so heat is an issue. But, eventually the roof will likely be covered with solar panels. Overall the bus is in excellent condition so I’m hoping to do the work adequately but quickly and inexpensively (aren’t we all). Advise please.

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Old 08-18-2022, 10:15 AM   #2
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I've never worked with fiberglass, but it doesn't sound like your problem is necessarily one specific to a bus. If you don't get the answers you're looking for here, there is a boatload of content on YouTube & the web in general that should get you squared away. If you're considering something other than fiberglass for the repair, I'd think again. I believe you'd be better off learning to work with it so you can do the job right.

As for tropicool & similar products, that's a controversial subject that's been covered here to the point of exhaustion. Use the search and set aside some reading time. I personally feel anything silicone based to be a nightmare you should avoid at all costs, and find the purported benefits regarding cooling to be questionable. But others seem to be pleased with the outcome.
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Old 08-18-2022, 01:00 PM   #3
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The only way I know of to repair "The Devil's Cloth" is to scrape anything (like roof coating) off, rough it up with 80-grit sandpaper, and sell your soul to the devil and get some more of his cloth, and then to add the resin and go to work like you're making something new out of it.

https://www.amazon.com/fiberglass-re...ass+repair+kit

To "patch" a 3x6 spot, you're going to need some new cloth, as well as the resin and hardener, as well as a stir stick and a container you don't care about. Should probably also wear some PPE like gloves, goggles, and possibly a respirator depending on your sauce.

3"x6" is also a big enough patch that, if you're not familiar with working with the devil's cloth, you may also want to buy some "Fiberglass mold release" compound, so you can make some kind of 'support' structure to essentially put underneath so you don't have to deal with too much sanding once you're done re-making a roof.

Using this method (when done right) will effectively make a roof that should be almost indistinguishable from the original, as the resin epoxy polymers will bind with each other and you wind up with essentially a large, plastic piece of thing with strands of silica running through it to help with structural support.

For patching purposes, I generally like to use a woven cloth rather than the more evil and satanic 'random orientation mat' cloth.

And I promise that, by the time you are done with this, you will understand why it is called "The Devil's Cloth".

Alternatively, you could also call/find a (fiberglass) boat-repair specialist--assuming you can find one in the desert--as they are quite well versed in this material and techniques, and can easily accomplish what you are looking to do. Considering the experiences I've had making custom fairings out of the stuff, I would highly advise seeking out these professionals, if you can, because getting that glass out of your skin can take days.
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Old 08-18-2022, 02:00 PM   #4
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Gracious. Ok. I will be sure to wear good gloves, etc. Thanks for the advice about using the woven cloth. I’m happy to be practicing for the first time on my bus roof—my crappy skills won’t show, lol.
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Old 08-18-2022, 02:01 PM   #5
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Thanks. I’ll search the archives for the Tropicool discussion. I’m happy to avoid coating my roof if I don’t have to in order to get it sealed up tight. Less time, money, and stress!
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Old 08-18-2022, 02:15 PM   #6
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Quote:
Originally Posted by Flowergarden View Post
Gracious. Ok. I will be sure to wear good gloves, etc. Thanks for the advice about using the woven cloth. Iím happy to be practicing for the first time on my bus roofómy crappy skills wonít show, lol.
Watch some 'fiberglass repair' videos on youtube, too. That should help with seeing some technique and advice that is probably beyond my skill level--I've even seen some videos of guys that make it look easy and relatively painless.

But, I, personally, still think fiberglass is an invention of the devil.
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Old 08-18-2022, 10:18 PM   #7
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THe 3x6 hole patch is no biggie. My first fiberglass repair was a "totaled" per the Hobbie dealer hull on my 16' hobbie cat. After repair I ran that boat for a number of years and never had an issue.


Cut out ANYTHING loose around the edges of the hole.
Grind down the gel coat and half the glass thickness for at least an inch around the hole.
Grind down the gel coat for another inch if you want to replace the gel coat layer on top of the patch. Personally I wouldn't as it's on the roof and it's not a million dollar show rig.

Place a non porus backer in the hole so that it is at the inner surface of the glass. Anything non porus will work....you don't want something that will hold moisture....Plastic cardboard would work great. Make sure it is SECURE as you'll be putting some pressure to it.



USE WOVEN CLOTH not that random fiber crap.You'll have more control over the things.
Cut layers of the cloth to fill the hole up to the step you ground into the edges, then layers to the size of that step.
Lay the first layer of cloth into the hole, pour some resin onto the cloth and work it over the entire surface and the edges using a paint brush if desired (a cheap one) and a plastic body putty "squeege".
Work the resin into the cloth so that it is saturated and lay the next layer of cloth into the hole.
With the second and subsequent layers of cloth work any excess resin in the previous layer(s) up into the newest layer before adding resin to saturate it.

The cloth is the strength and the resin is merely for bonding things.
Continue until you have filled the step you ground in but no higher than the original surface of the gel coat.
Let it all cure up.


NOTE: mix the resin in small batches as there is a "working time" which should be printed on the resin label.
DO NOT use extra hardner to make the job go faster
After it's all set you can use a straight edge to see if anything is above the roof contour and sand that down. If you sand into ANY glass fiber you need a light coat of resin over it


When you're happy with the contour, scuff up the top layer and a bit around the patch and paint to match the roof color.


Take your time....but not too much time as the resin has a limited useful life...... and you'll do fine.
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Old 08-19-2022, 09:26 AM   #8
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Look for Boatworks today on YouTube. His videos are about the best there is on glass work. He explains a lot of stuff the other videos don't

Myself on that larger hole. I would use epoxy resin. To start I would get a section of FR4 glass panel. 1/8" is thick enough. Make the panel large enough to cover the hole area. Epoxy it to the bottom side of the roof. I would use calking tube thickened epoxy to lessen the mess. Then go on the roof and lay glass and epoxy over the bad area.

That 1/8" stuff is just a support means for the outside repair to get done.

(Edit) The reason I am suggesting epoxy resin. For a beginner is that is the easiest less hassle resin to use. If you watch that youtuber I mentioned, he likes to use poly a lot.
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Old 08-24-2022, 08:40 PM   #9
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Use woven, not mat

If you haven't already bought the stuff, the woven material is much easier to work with than the mat.

Also, if you do it in layers you will have better results. The epoxy heats up as it dries and if you have a thick layer it will overheat and crack as it dries.

Its best to do it layer by layer, starting with a small piece, and then 1/2" bigger, and then 1/2" bigger.

Don't forget to wear gloves and a mask
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Old 08-25-2022, 10:25 AM   #10
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Quote:
Originally Posted by Touring4 View Post
If you haven't already bought the stuff, the woven material is much easier to work with than the mat.

Epoxy doesn't work well with chopped strand mat. That type of material has wax on the fibers for use with poly resin. Epoxy doesn't have anything in it to dissolve the wax which means the epoxy does not bind to the matting properly.

Flowergarden post up some pic's.
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