Why do so many use Dicor lap sealant when other products are far superior?
- Thread starter Jack Grit
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seak
Well-known member
If you will ever need to take the assembly apart again, I would consider a polysulfide sealand as a bedding compound. I use to use 3M 101 as a bedding compound, above and below the waterline on boats, but that's no longer available. I understand that Life-Calk, by BoatLife is a direct replacement.
If you have a good mechanical connection and clean surfaces, polysulfide will not leak if applied properly. It will remain flexible and survive for a very long time. I was told that 3M 5200 was developed as an adhesive sealant for sealing the deck to hull joint on fiberglass boats. You have to cut the adhesive join in the assembly with a blade to separate the parts. I have rarely used it for that reason.
If you have a good mechanical connection and clean surfaces, polysulfide will not leak if applied properly. It will remain flexible and survive for a very long time. I was told that 3M 5200 was developed as an adhesive sealant for sealing the deck to hull joint on fiberglass boats. You have to cut the adhesive join in the assembly with a blade to separate the parts. I have rarely used it for that reason.
seak said:
"Polysulfide is the most versatile of marine sealants. It is a synthetic rubber with excellent adhesive characteristics, and you can use it for almost everything. As a bedding compound it allows for movements associated with stress and temperature change, yet maintains the integrity of the seal by gripping tenaciously to both surfaces. It is also an excellent caulking compound since it can be sanded after it cures and it takes paint well." -http://masticmasters.com/polysulfide-vs-polyurethane/ . Which brand/product, that has good UV protection, would you suggest (other than Life-Calk) for adhering fiberglass to aluminum? I need some 3M 3000 UV but it would cost me 40 bucks per 10 oz tube to get unless I want to wait a long time for shipping.
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C-Cat
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You can't compare RVs with Boats. Lot's of RVs have rubber roofs (EDPM or TPO), often with fiberglass end caps. Dicor can seal many different materials and is safe for almost all rubber roofs (other sealers can damage or dissolve the rubber or will not adhere properly) and it's very forgiving if applied incorrectly (for example it will likely work fine even if the surface is not perfectly clean). Because it's self leveling, you don't need to apply it perfectly, it will just flow to make a seal between all these different materials and you can to some extend just add more to fix a leak quickly in a pinch. It's also water tight after 4 hours (and I even once had it rained on right after application and it held up). And as others have mentioned, it's relatively easy to remove when old and in need of replacement - some other sealers are a horrendous pain in the you-know-what... 
Teardrops and Tiny Trailers is a site that details homebuilt experimental building methods, especially the foamies section. Expedition Portal is another good site. The reason many people build out cargo trailers is the lack of well built RVs.
seak
Well-known member
Jack Grit said:
It's a little hard to know what's going on there without also seeing the assemby as a whole, but those are some big gaps. I would think you want to remove that whole aluminum sheet and rebed it. Hard to know how big a job that is from photo. But, chasing leaks with a tube of sealant without addressing the underlying issue hasn't been satisfactory in my experience.
Well then, ending up with a more robust longer-lasting result is a nice side effect.
IMO this is not an area to skimp on, penny wise pound foolish.
Same with waiting to get the right stuff, rather than just using what's conveniently available.
IMO expecting all functions in one product may be unrealistic.
Adhesive function can be separated from the UV-protecting sealant over the top.
So start with the top adhesive, 5200. Or will you want to undo it one day? If so, is some damage to one side or the other acceptable in that (undoing) process?
I agree the situation is not clear enough to be so specific.Jack Grit said:
IMO this is not an area to skimp on, penny wise pound foolish.
Same with waiting to get the right stuff, rather than just using what's conveniently available.
IMO expecting all functions in one product may be unrealistic.
Adhesive function can be separated from the UV-protecting sealant over the top.
So start with the top adhesive, 5200. Or will you want to undo it one day? If so, is some damage to one side or the other acceptable in that (undoing) process?
seak said:
The interesting part is the only damage I have found from this is a square foot area that is slightly infirm. The aluminum sheet is the entire roof except the fiberglass above the cab. Re-bedding may be optimal but I don't think necessary. I have done a heck of a lot of work on the roof. The underling issue is likely taken care of. I agree with the sealant comment. I plan on doing more than simply slapping some sealant up there. Thanks for the reply.
You make a good case for dicor being good in some instances. In my view there is a time for dicor. For me it's not often.C-Cat said:You can't compare RVs with Boats. Lot's of RVs have rubber roofs (EDPM or TPO), often with fiberglass end caps. Dicor can seal many different materials and is safe for almost all rubber roofs (other sealers can damage or dissolve the rubber or will not adhere properly) and it's very forgiving if applied incorrectly (for example it will likely work fine even if the surface is not perfectly clean). Because it's self leveling, you don't need to apply it perfectly, it will just flow to make a seal between all these different materials and you can to some extend just add more to fix a leak quickly in a pinch. It's also water tight after 4 hours (and I even once had it rained on right after application and it held up). And as others have mentioned, it's relatively easy to remove when old and in need of replacement - some other sealers are a horrendous pain in the you-know-what...
John61CT said:
Yes, this is not a time to skimp.
Even though rain is expected next weak, I decided to do it right the first time vs a wimpy patch while waiting for a longer stretch of sun.
Yes, I plan on using more than one product.
On the UV issue. absolutely.
Concerning 5200, I know too little about the rig to seal the area permanently. Although I have had it for over a year, I have only driven it three times. I don't know enough about sealants and what damage they may cause if removal is necessary. It may be that the area in question may need to flex. I just don't know. Still searching.
Thanks for the reply.
5200 still flexes fine, but avoid in your case, really only for true permanent use cases.
3M 4000UV may be just the ticket if you don't need to cover further, but beware it sets up very quickly, maybe 10-15min working time.
4200 no UV, but needs moisture, at least humidity to cure.
Sikaflex 291, Boat Life Life Seal and Life Caulk, just google these, especially in the marine forums with the
site:
operator and you'll learn a lot.
Download and read the detailed spec sheets for any before buying.
3M 4000UV may be just the ticket if you don't need to cover further, but beware it sets up very quickly, maybe 10-15min working time.
4200 no UV, but needs moisture, at least humidity to cure.
Sikaflex 291, Boat Life Life Seal and Life Caulk, just google these, especially in the marine forums with the
site:
operator and you'll learn a lot.
Download and read the detailed spec sheets for any before buying.
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