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Old 04-07-2023, 08:16 PM   #1
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Best Seam Sealer?

Hey Everyone. I am starting the process of re-sealing my entire roof/all the seams. I am trying to decide between dynatron 550 (seems to be popular) and 3M Urethane Seam Sealer, 08368.

Does anyone have experience with both of these? Which did you find to be the best?

https://www.amazon.com/3M-08367-Blac...007NIQONO?th=1

https://www.amazon.com/550-Permanent...005RNFBMC?th=1

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Old 04-07-2023, 11:13 PM   #2
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I absolutely prefer the 3M, for its "workability" and the ability to smooth it. I find that the Dynatron is very hard to smooth and it wants to ball up, pull, and generally fight me. Maybe I'm doing it wrong, but I've tried about 5 different tubes of it (primarily because our local Auto Zone carries it) and just don't care for it.

Recently...and finally!...I've been able to do a bit of work on Stevie, our Crown, and I have 4 tubes of that 3M on the shelf for sealing seams on that bus (after I wire brush and remove some loose paint at the seams).
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Old 04-07-2023, 11:42 PM   #3
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Originally Posted by rossvtaylor View Post
I find that the Dynatron is very hard to smooth and it wants to ball up, pull, and generally fight me.
I wonder if you've gotten somewhat older, dried-out tubes of the stuff. I always use it with a spray bottle of mineral spirits. Misting the dynatron down with mineral spirits keeps it supple and easy to smooth out and prevents it from skinning over until I'm done working with it. I've never used the 3M so maybe that just works better right from the tube, I dunno.
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Old 04-07-2023, 11:42 PM   #4
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Originally Posted by rossvtaylor View Post
I absolutely prefer the 3M, for its "workability" and the ability to smooth it. I find that the Dynatron is very hard to smooth and it wants to ball up, pull, and generally fight me. Maybe I'm doing it wrong, but I've tried about 5 different tubes of it (primarily because our local Auto Zone carries it) and just don't care for it.

Recently...and finally!...I've been able to do a bit of work on Stevie, our Crown, and I have 4 tubes of that 3M on the shelf for sealing seams on that bus (after I wire brush and remove some loose paint at the seams).

Do you wet a finger with anything to tool it?
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Old 04-07-2023, 11:52 PM   #5
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I wonder if you've gotten somewhat older, dried-out tubes of the stuff. I always use it with a spray bottle of mineral spirits. Misting the dynatron down with mineral spirits keeps it supple and easy to smooth out and prevents it from skinning over until I'm done working with it. I've never used the 3M so maybe that just works better right from the tube, I dunno.
Now you tell me... I'm sure it was operator error on my part. Our Auto Zone has a normal stocking quantity of exactly one tube, so I'd buy one...wait a few weeks...buy another...and so on. I think they were fresh.

Quote:
Originally Posted by fo4imtippin View Post
Do you wet a finger with anything to tool it?
Uh...no, I didn't. Which was most likely my issue. It skinned over very fast and I should have tried (but didn't know about) musigenesis' mineral spirits suggestion.
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Old 04-08-2023, 11:59 AM   #6
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I’ve used Dynatron on a lot of my bus but I do find it works much better when it’s warm outside and the tube itself is warm. It is very sticky and may not be the best tool for every job. I bought a different kind for my roof seams and it was much easier because it wasn’t as sticky but I can’t remember what it was called…I’ll update later when I remember or get home.
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Old 04-08-2023, 12:33 PM   #7
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Sikaflex 221

We've been very happy with Sikaflex 221. Flexible and tough. Definitely need mineral spirits for clean up and tooling.
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Old 04-08-2023, 12:45 PM   #8
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I remember! I used Sem automotive seam sealer on the roof. A little pricey but less sticky than dynatron.
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Old 04-08-2023, 12:46 PM   #9
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We've been very happy with Sikaflex 221. Flexible and tough. Definitely need mineral spirits for clean up and tooling.
Mineral spirits in a bottle will help with a lot of the process for any of these seam dealers. I think I’ve used paint thinner too, makes the sealer a little more elastic if it sets up too fast and will pick it up if you accidentally get it somewhere you don’t want it.
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Old 04-08-2023, 01:02 PM   #10
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I remember!
Yay, for coffee!
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Old 04-09-2023, 05:10 PM   #11
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ive been using good old dynatron 550 for decades and it has held up well for me over the years.. it is definitely sensitive to cool.. I almost always work with it when its good and warm for both the tube and the surfaces.. a urethane might be less sensitive ive really never tried anything else as 550 is in stock about anywhere you go
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Old 04-09-2023, 06:49 PM   #12
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Thanks everyone. I actually first tried going with the 3m stuff I posted but apparently it is packaged in a flexible tubing and I don’t have an application tool for it. So i went to my local AutoZone and got some dynatron.

That stuff does not spread easy without water/mineral spirits. I applied it pretty heaving with hope that it will be able to partially sand when I sand the roof for painting.
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Old 04-09-2023, 08:54 PM   #13
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I don't think you're going to be able to sand Dynatron-550. I wouldn't worry about it since your roof seams are not really all that visible from the ground.
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Old 04-10-2023, 06:16 PM   #14
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Quote:
Originally Posted by [LEFT
nconn[/LEFT];490511]That stuff does not spread easy without water/mineral spirits. I applied it pretty heaving with hope that it will be able to partially sand when I sand the roof for painting.
It will pull out if you try to sand it, same with caulks and silicone. Save yourself a few hours! And Rusty has a point, no one will see it. If it does need to be neatened up you could always paint the roof with a thicker elastomeric paint which is basically rubber in paint form. Or add more seam sealer to make it more uniform way better than sanding down too far and having to reseal the metal.

Also, not sure if you used painters blue masking tape but that will give you very straight seam lines like a pro, with less cleanup (if you are careful removing the tape).
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Old 04-19-2023, 06:43 PM   #15
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IMO 3M is the best

https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1

Silka is a great alternative, or any urethane window/door sealer.
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Old 04-19-2023, 06:50 PM   #16
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I have not used Dynatron but I used 3M automotive urethane to reseal my windows and I’ve been very happy with the performance. The only complaint I had was it did not stay white for long. It turned a dingy sand color within the first week so don’t buy the white stuff expecting it to stay white.
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Old 04-20-2023, 07:26 AM   #17
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Has anyone used 3m 5200? I used it for sealing my window patch panels and a box I made in the back to expand the engine compartment for easier working under the bed where the back seat bench was. I also recommend the tape lines method, we put windows in airplanes that way, tape 1/4” away from the edge on the window and right on the edge of the metal and then smooth the sealant down with a little metal spatula, then peel the tape off while it’s wet and it’s perfect fillet every time.
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Old 04-20-2023, 11:05 PM   #18
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I don’t see many people mentioning sikaflex 221 or the UV equivalent here. Any reason?
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Old 04-24-2023, 12:54 PM   #19
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I don’t see many people mentioning sikaflex 221 or the UV equivalent here. Any reason?
Too many alternatives and people tend to get overwhelmed (like me) and pick the most common options like Dynatron even though it's not necessarily the best for all applications (in my case I find its really sticky, which makes it hard to work with sometimes).
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Old 04-24-2023, 06:24 PM   #20
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Also would depend on the area etc. Sikaflex is easy to find in Aus and NZ but less so here in Ontario, I’ve been recommended it by boaties since it’s used to bung holes in yachts and I’ve done a shipping container roof patch with it.
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