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Old 04-10-2020, 11:44 AM   #1
Mini-Skoolie
 
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Which sealant or adhesive is best?

Hi, I have been looking at several posts that discuss different adhesives and sealants for use between sheet metal overlap on skoolies, and it is coming time to make a decision for our bus.

It seems like the main choices on this site are between:

3M Dynatron 550 Automotive Seam Sealer - Relatively cheap. Has a good reputation as a sealer. But has a handling time of only 10-20 minutes which may not be long enough for me to rivet a 10 foot side panel.

3M Bare Metal Seam Sealer - Two-Part, Stronger bond, but more expensive and only 15 minute working time.

Sikaflex 221 Polyurethane Adhesive and Sealant - One part, and work time seems to be closer to 40 minutes. Can elongated up to 3 times its original thickness before it tears. But doesn’t seem to have much adhesion strength.

3M Impact resistant structural adhesive. - 2 part, recommended for riveted joints in the automotive industry, some say it is as strong as a weld, has a 1 hour work time. But it is very expensive, and is not advertised as a sealer, so much as an adhesive.

What do you guys think would be the best option for putting between sheet metal seams for a strong bond and minimize (zero?) water leakage?
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Old 04-10-2020, 01:08 PM   #2
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I've only ever used Dynatron-550 so I can't compare it to anything else, but I've been totally happy with it. I covered over my back rear window with a riveted piece using the 'tron to seal around the edges and to seal each rivet: https://www.skoolie.net/forums/attac...9&d=1563447226. That was about 100 rivets and I had no problem with the set time (you have to have all the holes pre-drilled, of course). You can also easily mist it down with mineral spirits from a spray bottle to allow you to work with it longer.

Best price by far is (was?) at Auto Zone stores for $15. Everywhere else it seems to be at least $20 + shipping. FWIW I have heard Dynatron-550 described as expensive by other people here.

There's also a Dynatron-570 which is the same thing only white, but I've never used it or seen it.
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Old 04-10-2020, 03:09 PM   #3
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Originally Posted by musigenesis View Post
I've only ever used Dynatron-550 so I can't compare it to anything else, but I've been totally happy with it. I covered over my back rear window with a riveted piece using the 'tron to seal around the edges and to seal each rivet: https://www.skoolie.net/forums/attac...9&d=1563447226. That was about 100 rivets and I had no problem with the set time (you have to have all the holes pre-drilled, of course). You can also easily mist it down with mineral spirits from a spray bottle to allow you to work with it longer.

Best price by far is (was?) at Auto Zone stores for $15. Everywhere else it seems to be at least $20 + shipping. FWIW I have heard Dynatron-550 described as expensive by other people here.

There's also a Dynatron-570 which is the same thing only white, but I've never used it or seen it.
Ah, I have been wondering about sealing each rivet. Do you put it under each head of the rivet, or dip each shaft, or both?

It seems like under the head would be the first choice. But i was concerned that they would squeeze out from under and interfere with the paint job around the rivets. Is that an issue?
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Old 04-10-2020, 03:41 PM   #4
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Originally Posted by Truffles View Post
Ah, I have been wondering about sealing each rivet. Do you put it under each head of the rivet, or dip each shaft, or both?

It seems like under the head would be the first choice. But i was concerned that they would squeeze out from under and interfere with the paint job around the rivets. Is that an issue?
For my back door panels, I ran a bead of sealant around the edge of the piece (on the inside) then put it into place with the clecos. To put in a rivet "wet", you put a small blob of sealant over/around the hole, then put the rivet in and pull it. Then you wipe off the excess that squeezes out with a cloth and mineral spirits (you do the same with any that squeezes out from under the edges).

Dynatron-550 can be painted with no problem, but with this method you don't have a whole lot of sealant showing anyway.
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Old 04-10-2020, 03:48 PM   #5
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I've done like 2 or 3 roof hatch deletes and a few windows and never had a leaky rivet. Never dipped any just took time and care with the rivets.
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Old 04-10-2020, 03:55 PM   #6
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I've done like 2 or 3 roof hatch deletes and a few windows and never had a leaky rivet. Never dipped any just took time and care with the rivets.
What kind if rivets do you use? Closed end pop rivets? Solid rivets?
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Old 04-10-2020, 04:15 PM   #7
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Stainless closed end 1/4". I bought a LOT.
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Old 04-10-2020, 04:28 PM   #8
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Stainless closed end 1/4". I bought a LOT.
Mind if I ask your source? That size seems to be rare on the internet these days.
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Old 04-10-2020, 04:30 PM   #9
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I've done like 2 or 3 roof hatch deletes and a few windows and never had a leaky rivet. Never dipped any just took time and care with the rivets.
Before I started my riveting I built a watertight metal box and then practiced putting rivets into the bottom to test out how well sealed they were (I fill the box with water and then see what leaks out past the rivet). My rivets always leaked unless I put them in wet with seam sealer like I described. It may be that the water pressure of a filled container is a more stringent test than what you would get from just rain on the outside of a bus, but I like knowing that they're definitely going to be watertight no matter what the situation.
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Old 04-10-2020, 04:31 PM   #10
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I used dynatron with good success.
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Old 04-10-2020, 04:33 PM   #11
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Lacquer Thinner works great at smoothing dynatron and for cleanup
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Old 04-10-2020, 04:54 PM   #12
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Quote:
Originally Posted by musigenesis View Post
Before I started my riveting I built a watertight metal box and then practiced putting rivets into the bottom to test out how well sealed they were (I fill the box with water and then see what leaks out past the rivet). My rivets always leaked unless I put them in wet with seam sealer like I described. It may be that the water pressure of a filled container is a more stringent test than what you would get from just rain on the outside of a bus, but I like knowing that they're definitely going to be watertight no matter what the situation.
a dab of lap sealant on roof rivets is more than enough. On vertical surfaces you really can just run em dry. I've went back with a dab of sealant on roofs for the hell of it.
What rivets are you using and what are you using to pop em?
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Old 04-10-2020, 05:38 PM   #13
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I have experience with both dynatron and the sikaflex1a on my project...

Sounds like my experience and musigenesis were about the same with dynatron 550. Although I didn't know the tip for clean up with mineral spirits. we installed alot of "wet" rivets and they do look a little messy... We cleaned them up with a wire brush on a grinder i think. Just kinda smudged it around but it will be ok with paint. Worked good for the wall panels after the roof raise. It has very little adhesive qualities. ( We used solid rivets 3/16 and 1/4...This requires a two person method of instal.)


I bought a case of sikaflex for my window installs and i have liked it so far. Really good adhesive, apply good clamping pressure. Seems to be a very good sealant as well. Honestly, I think you can skin over windows/holes or a whole roof raise with 3/8" hex head screws and sikaflex. Easier than rivets and just as strong. (My bus body had some hex head screws holding rub rails or body panels on where it would have been impossible to set a rivet... I used these for reference when purchasing.)
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Old 04-11-2020, 12:37 AM   #14
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I have only used Loctite PL-S40 (or equivalent) for adhesive and sealant on our bus so far. It adheres strongly to metal, wood, and plastic .... perhaps more. It takes time to cure properly, but when it does it can be painted.
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