I will echo what Sunline Fan posted and add some more.
When you go to buy the butyl sealing tape, try and make sure you can tell what brand it is. A generic role on a shelf at a RV place with no name attached to it sometimes creates problems. How old is it? (there is a shelf life on this material) What type of butyl is it? Is it really butyl tape and not putty tape?
Putty tape is sold and advertised for exactly what you are doing. And it does work, but it has many negative attributes which include a short life span of leak free use. So if you ask someone in the store you want to seal up a cargo hole on a camper, they may give you putty tape and not think twice about it. It looks close to some butyls. They do sell butyl for sealing roof vents on a rubber roof as the butyl does not affect the rubber membrane.
One large difference you can see between the two products is their elastic ability.
Do a small pull test on putty tape, (take 1" or less of the material and pull each end) If it snaps in two parts in a few inches (1 to approx. 3") of pulling, this is an attribute of putty tape.
If you do a small pull test on butyl tape, (take 1" or less of the material and pull each end) If will pull like salt water taffy and goes all stringy... and it may take several feet to yards to snap in two parts and it thins out as you pull, it really does not snap, this is a attribute of butyl sealing tape.
On the Dicor non leveling caulk, I agree this is good to do on the exposed butyl. The butyl is so sticky that dirt wants to attract to that exposed edge worse then putty tape. What make the product work so good by sticking and staying in place creates this one side effect. Doing the Dicor also creates a secondary water seal and prevents the sun rays from directly hitting the butyl.
If you never caulked Dicro before and tooled it smooth, there is a learning curve. Which is generally frustration preceded by efficiency.... To help on the learning curve, see this post. This is one method that is repeatable and someone who never did this before can learn and it not look bad. Hopefully someday a master caulking person can take this to the next level. (that is not me, yet anyway)
Hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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