Best way to remove old sealant on roof around fans and vents - Fiberglass RV


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Old 03-31-2020, 08:08 PM   #1
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Best way to remove old sealant on roof around fans and vents

Hello, I am new to owning a fiberglass trailer and camper trailers in general in fact. I have just purchased a 1984 Bigfoot B17 and was wondering the best way to remove the old sealant around the fan and vents on the roof of my trailer. The existing stuff is dried out and starting to crack. I have looked on these forums and there is a lot of info about how to reseal things... Butyl tape and dicor lap sealant seem to be the consensus but not to many specifics about how to safely and adequately remove the old sealant. It looks quite hard and like it is not going to come off easily. Is there a good solvent or cleaning agent that does the trick? Plus probably a good putty knife or something of the like?
Thank you in advance Martin....
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Old 03-31-2020, 10:34 PM   #2
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I'm not sure what the appropriate chemicals to soften these materials might be. I once used mineral spirits paint thinner instead of pitch and sap remover on a car, and it degraded the paint. So, choose carefully.

I expect someone will post a better reply concerning the solvents you might use. Personally, I'd start with water and/or hot water; it's the "universal solvent".

A Hyde five-in-one painters tool might be useful, but as they are made of metal you'd have to be very careful to avoid damaging the fiberglass. There are also various plastic scrapers available that help with the job while posing less risk to the fiberglass.
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Old 04-01-2020, 03:40 AM   #3
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For softening I've had good luck applying heat with a hair dryer. A dull putty knife will work if you are careful. Plastic scrappers, often used to apply bondo, can be found at the auto parts store often in a fish bowl on the counter next to the cheap screw drivers. Heat first, then the chemicals for the residue. Goo Gone is safe on fiberglass as is acetone. If it's silicone you are trying to remove, do some research, as silicone presents it's own challenge and may require special chemicals. Good luck.
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Old 04-01-2020, 06:38 AM   #4
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removing

I vote for the hair dryer concept. Some of that stuff is hard and after years of setting really hard. have a good scraper on hand also I would go with a metal one for the big part.

work and more patient work but you will get it off. Remember you will be covering it back up which brings up a new comment or question stay away from the silicone stuff!

best of luck on your job you will make it! these guys can tell you what to use for your resealing..


bob

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For softening I've had good luck applying heat with a hair dryer. A dull putty knife will work if you are careful. Plastic scrappers, often used to apply bondo, can be found at the auto parts store often in a fish bowl on the counter next to the cheap screw drivers. Heat first, then the chemicals for the residue. Goo Gone is safe on fiberglass as is acetone. If it's silicone you are trying to remove, do some research, as silicone presents it's own challenge and may require special chemicals. Good luck.
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Old 04-01-2020, 11:03 AM   #5
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Removing old sealant

We successfully used WD40, plastic putty knife, & cleaned oily residue with rubbing alcohol. It worked on old silicone, butyl, & polyurethane sealant, as well. Jessie
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Old 04-01-2020, 11:28 AM   #6
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The old Dicor sealant get's pretty hard, and was often applied pretty thick, so chemical treatments aren't as useful. I needed a putty knife and hammer to basically chisel away the old stuff on my roof. I'm sure I did a little damage to the gel coat, but I was just going to cover it over with new Dicor anyway...

It's probably dangerous taking my advice, but I also saw no compelling reason to get the roof squeaky clean, even though people seem to advise getting all old sealant cleaned up. Dicor sticks to dicor. So I cleaned off the chunks as well as I could, and called it good. Silicone is different story. With dicor, I don't see why it matters other than making yourself feel good.
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Old 04-01-2020, 12:30 PM   #7
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I used a Dremel Multi-tool with a flexible scraper to get sealant etc off the gelcoat. Just be a bit careful not to drive the scraper into the gelcoat; ie don't gouge it. Run it flush with the gelcoat and you should be good. Slow and steady with not a lot of pressure. Worked pretty good for me.
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Old 04-01-2020, 07:47 PM   #8
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I use a heat gun and I use wood shaped on my grinder. They do not scratch the top. I just make the size I need and make a nice sharp edge. They do not last forever but you just resharpen it. They are safe on fiberglass. Go easy with the heat.
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Old 04-02-2020, 03:12 PM   #9
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Thanks everyone! I have a good heat gun and it makes sense to use some kind of not very abrasive scraper. So far I have heard of acetone, isopropyl, de-natured alcohol, and a few others as viable options for chemical removal/cleaning.

Does anyone else see the value in attempting to re seal all of the "quote unquote" opening on the trailer ie... Door, windows, side vents and hatches etc... The roof vents and windows are the ones that seem to get the most attention in regards to there proving to be the worst culprits for major leaks.
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Old 04-02-2020, 03:35 PM   #10
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I think you should do what you are doing. Inspect them, and if they look suspect, reseal them.

Beyond that it's up to you. Will it make you feel better to have them all resealed? Then do it. Are you one of those "ain't broke don't fix it" types? See if it's broke. If it ain't...
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Old 04-03-2020, 07:13 AM   #11
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My old vent had half a dozen layers of caulk around it, up to 6" wide around the vent. The upper layers were soft but the older layers were brittle and hard. I tried a caulk removal spray bottle I found at the home store, but it only really affected the top layer a little, had no real useful effect. In the end old fashioned manual scraping was necessary for most of it. I can post pictures if interested but they are on a different computer.
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Old 04-03-2020, 10:05 AM   #12
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No help

Quote:
Originally Posted by Marty_3000 View Post

Does anyone else see the value in attempting to re seal all of the "quote unquote" opening on the trailer ie... Door, windows, side vents and hatches etc... The roof vents and windows are the ones that seem to get the most attention in regards to there proving to be the worst culprits for major leaks.
By resealing everything, it's doubtful you'll ever need to do it again. Also, with everything closed you won't be camping for a while. On the other hand if it ain't broke..... Simple repairs often turn into big projects, especially on an old trailer.
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Old 04-03-2020, 11:21 PM   #13
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Plexiglass scrapers work well. I cut 1/8" or 3/16" plycarbonate sheet into 1" wide strips on the tablesaw and then cut them into 8" lengths. Then on the end sand a bevel similar to the look of the bevel on a wood chisel. Belt sander works great for making the bevel. Put a bevel on both ends if you wish to do so. You can then resharpen it on the sander whenever the edge starts getting a bit dull. The scraper is durable but it is handy to have several of them so you don't have to stop and sharpen. Having extras saves getting up and down off the ladder in the middle of the job.

I developed my love for this scrapers when working at Boeing, they are standard issue for such task. and they make them in house for all the tool rooms in the company to stock. They do not scratch the gel coat with normal use, of course if you tried to drive the sharp edge into the surface you could do damage but not for normal caulk removal.

I promise, you will like this tool and want to have them in your tool box for use around the house as well as for caulking on the trailer. Makes a nice pan scraper for the kitchen. Or for getting a spot of gunk off the floor. Scraping a label off, etc.
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Old 04-04-2020, 07:21 AM   #14
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Quote:
Originally Posted by Steve Carlson View Post
My old vent had half a dozen layers of caulk around it, up to 6" wide around the vent. The upper layers were soft but the older layers were brittle and hard. I tried a caulk removal spray bottle I found at the home store, but it only really affected the top layer a little, had no real useful effect. In the end old fashioned manual scraping was necessary for most of it. I can post pictures if interested but they are on a different computer.
Thank you but it is as say... It seems it is going to just be a matter of getting up there with the right tool and using a lot of elbow grease. If you happen to be on your other computer and feel like you have time to post those pictures that would be nice. Pictures are always helpful! But don't go out of your way I think I know what I'm up against now. I appreciate the reply.
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Old 04-04-2020, 07:30 AM   #15
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Originally Posted by k corbin View Post
Plexiglass scrapers work well. I cut 1/8" or 3/16" plycarbonate sheet into 1" wide strips on the tablesaw and then cut them into 8" lengths. Then on the end sand a bevel similar to the look of the bevel on a wood chisel. Belt sander works great for making the bevel. Put a bevel on both ends if you wish to do so. You can then resharpen it on the sander whenever the edge starts getting a bit dull. The scraper is durable but it is handy to have several of them so you don't have to stop and sharpen. Having extras saves getting up and down off the ladder in the middle of the job.

I developed my love for this scrapers when working at Boeing, they are standard issue for such task. and they make them in house for all the tool rooms in the company to stock. They do not scratch the gel coat with normal use, of course if you tried to drive the sharp edge into the surface you could do damage but not for normal caulk removal.

I promise, you will like this tool and want to have them in your tool box for use around the house as well as for caulking on the trailer. Makes a nice pan scraper for the kitchen. Or for getting a spot of gunk off the floor. Scraping a label off, etc.
That does sound like the tool for the job. Now that you mention it I used some clear hard plastic to scrape off sun baked painters tape from an antenna dome on board one of our navy ships while it was in for re fit.

Where did you get your polycarbonate? I could normally likely get some from work but we are shut down at the moment. I would assume my local industrial plactics and paint supply place would have it. Probably not something you could buy at the home depot or the like?
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Old 04-04-2020, 09:59 AM   #16
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K Corbin, great idea. Would hold an edge longer than the wood and would definitely get sharper. I like when people share tool ideas.
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Old 04-04-2020, 11:15 PM   #17
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Originally Posted by Marty_3000 View Post
That does sound like the tool for the job. Now that you mention it I used some clear hard plastic to scrape off sun baked painters tape from an antenna dome on board one of our navy ships while it was in for re fit.

Where did you get your polycarbonate? I could normally likely get some from work but we are shut down at the moment. I would assume my local industrial plactics and paint supply place would have it. Probably not something you could buy at the home depot or the like?
I suggested polycarbonate as that material reduces the risk of shattering when cutting the plastic on the tablesaw.

I just talked to my workshop partner and he said he can laser cut you some out of acrylic. That is what we make them out of for our own use as we have a laser cutter here. We have the materials on hand so a quick turnaround to get them into the mail

A half dozen for $11.00 including standard first class shipping in mainland USA. If you want priority shipping instead let me know that so I can add the extra shipping cost to the bill. Invoicing can be done with Pay Pal which works because I can buy the postage through them too.

Just send me a pm if you want to do it that way. Anyone who want some scrapers is welcome to contact me. But not shipping outside of the USA at the moment. Just offering this to fellow FGRV owners who are stuck, oh excuse me, safe-at-home this spring without a lot of resources. I am not trying to start a business producing them in mass.
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Old 04-08-2020, 12:31 PM   #18
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The boat industry deals with this regularly. Tools that I used were dense wood wedges and palette knives from an art store. The knives are used by oil on canvas artists. The knives are thin and can be easily shaped if you want to reshape them. They come in different shapes. I used heat, palette knives and wedges to keep seam open as I worked around the fixture.


For cleanup you can look for options on boating forums but alcohol does no damage gel coat. Acetone can damage the finish. I forget what I used but be careful with acetone.
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Old 04-08-2020, 01:43 PM   #19
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I suggested polycarbonate as that material reduces the risk of shattering when cutting the plastic on the tablesaw.

I just talked to my workshop partner and he said he can laser cut you some out of acrylic. That is what we make them out of for our own use as we have a laser cutter here. We have the materials on hand so a quick turnaround to get them into the mail

A half dozen for $11.00 including standard first class shipping in mainland USA. If you want priority shipping instead let me know that so I can add the extra shipping cost to the bill. Invoicing can be done with Pay Pal which works because I can buy the postage through them too.

Just send me a pm if you want to do it that way. Anyone who want some scrapers is welcome to contact me. But not shipping outside of the USA at the moment. Just offering this to fellow FGRV owners who are stuck, oh excuse me, safe-at-home this spring without a lot of resources. I am not trying to start a business producing them in mass.
Thank you for the generous offer but I live in Canada so that leaves it out of the question for now. I will be able to get my hands on some one way or another
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Old 04-08-2020, 01:44 PM   #20
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Originally Posted by Bob Gr View Post
The boat industry deals with this regularly. Tools that I used were dense wood wedges and palette knives from an art store. The knives are used by oil on canvas artists. The knives are thin and can be easily shaped if you want to reshape them. They come in different shapes. I used heat, palette knives and wedges to keep seam open as I worked around the fixture.


For cleanup you can look for options on boating forums but alcohol does no damage gel coat. Acetone can damage the finish. I forget what I used but be careful with acetone.
Also very good advice! Thank you for sharing. I didn't realize how much the fiberglass trailer world crossed over with the marine world
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