WpgTech
The Moon
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Joined: 10/05/2008
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I get asked a lot about resealing units - something I do a lot of at work.
Cracked and excessively bulging and generally ugly seals are indication of work needing to be done.
In most cases what you are looking at is the inner seal under the metal molding (butyl tape) bulging out, compromising the outer sealant, which is often Proflex or Silicone.
First of all, Silicone Sealant sucks. It simply doesn't bond well at all with fibreglass (and only slightly better on metal). It lifts, and eventually pretty much falls right off. RV Proflex is a much better product but is trickier to work with.
First step is to determine how badly the butyl tape has been compromised. If the molding is lifting, and is obviously distanced from the RV body panel, a quick seal job isn't going to help here. This is time to remove the entire molding or at least the portion where harm has found it's way. This is very typical in the rear bottom corners of units. The white plastic center cap over the molding easily pulls back for removal. This will reveal the screws - often those screws are holding on to... nothing, and are corroded. As well, it is common for the backing wood to be rotten.
If this worse case scenario is the case it's time to determine how complete of a fix is necessary. 9/10ths of the time, if a customer comes to me with a rotten rear corner and is determined to "properly fix" the unit - I will come up with a creative new "use" for the corner. What I mean by this is - rather than remove an entire sidewall to fix a rotten corner - I will opt to put a new storage compartment, or outdoor shower... or something in the damaged corner
that will give us an excuse to completely rip it apart, but not have to "patch it" back together.
In a less severe case, you'll want to remove the molding and refresh it. Two tools you'll want: a razor knife, and a plastic scraper (get one of these from a glazier, window installer). Carefully slice into the seal at a 45 degree angle inwards toward the metal molding, down the length of the molding. This is especially important at points where decals meet molding. This will prevent decal "lifting".
Once you've sliced through the outersealant, if necessary remove the entire molding, clean, and replace the butyl tape. Use the type with brown paper backing, not the lousy kind with crinkly white paper backing. Be extra careful to make sure enough butyl is used, even if that means doing two passes, and make sure every single hole is well covered.
Do a thorough cleaning of the corner while the molding is off, using (BEST) Diasol, or more easily found (VARSOL). If you want to be really picky because the unit is very new, follow that up with something that evaporates like alcohol. Be very careful using strong evaporating degreasers like BEST DARN DEGREASER. They work excellent, but keep them restricted to use on just the corner. Don't go wiping big areas that will be visible as they will "ghost" a brand new fibreglass finish, and be visible in bright sunlight.
So after you have either scraped and cleaned all the old sealant from the corners of the molding, or revamped the entire molding (butyl tape and all) - it's time to put it all back to factory.
Re-install the molding if necessary, sometimes this will require new screws, and screw locations. In bottom corners, sometime a MUCH MUCH longer screw (3-5") to get it to "hang on". Clean and re-install molding cap, or use new (it's cheap). Cut the end of the molding capin an elongated V shape, in order to double it under itself, and put in the last screw about 3/4" from the end of the molding. You'll have to stretch the cap quite a bit to do this, but afterwards you can fold it doubled over, and insert it - allowing even the last screw to be hidden by cap.
Now for the resealing part:
Using a plastic scraper, carve back the excess butyl tape DEEP. In other words, carve it away leaving an actual groove or indentation, into the molding. This will leave a pocket for the outer sealant to "live" and it will hang on better. Otherwise, you are going to be "painting" the bulging butyl with sealant - not what you want. Because the butyl is under compression - for it's life - it is constantly, slowly "expanding" - so do not be scared to really "cut in".
Use RV Proflex - but heres an important tip. Only seal in one, comfortable direction. Don't apply more than about 6' at a time. Set a good time allowance and tackle a lot, in one day - because PROFLEX doesn't "last" well once opened. Cut the sealant tube tip "small" - only letting a small amount out at once.
CLEAN YOUR HANDS POINT
So -- here is how its done. Apply about a 1/8" bead down your freshened and clean molding edge. Run it out smooth and consistent for about 4 ft. the first time. (later you can do 8-12' at a time).
Here's the trick:
Have a plastic bowl of VERY soapy water (or a spray bottle) ready.
Soak your hand in soapy water (or at least the finger you will use). With that very soapy finger, make a first pass with the fingerprint side of your finger "pushing" the sealant into the "groove" you carved out of the butyl. Now, soap up that finger again, this time making sure the finger nail side is very slimy and soapy.
Run your finger up the molding, this time pressing harder using your fingernail as a "scooper". Only go as far as your finger nail will "contain the excess", In other words 5-12". If the Proflex is slopping off the side of your finger onto the sidewall, you've gone too far. Have a paper towel handy to wipe the excess Proflex onto, as you go. When done you will have a perfect amount of sealant running the length of your molding, and it will appear very nice, dishing inwards slightly - looking like a small fillet gas weld. Not too much, not to little. Just like the boys at KZ do it 
Don't worry about any slop that occured, at this point. Let it all dry, then carefully take white paper towel and degreaser and clean up any "smearing" after it has all set up.
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raygreg
Seattle,WA
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Joined: 06/30/2003
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Thanks for the great write up and good tips.
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alpenliter
Olympia WA
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Joined: 04/10/2005
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Thanks Kyle! I've read all your posts and put your posts on my subscription list, as it seems like you know what you are talking about, and like to think outside the box on repairs. Welcome to the forum and keep posting!
My first Wife Linda, 40+ years
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