Teardrops n Tiny Travel Trailers

I finally bought a Fantastic fan for our Silver Shadow. I cut the hole in the roof and wired every thing in. The roof has a curve to it and it obviously does not sit flush. It did not come with any gaskets. I went to a RV store and bought a roll of putty tape that they recommended. I asked if I should use Butyl tape ( I think I spelled that right ) and they said no that the putty is what I should use. I put a couple of strips of the putty tape where it should go and mounted the fan in place. I figured the tape would fill in the 1/4 inch gap between the roof and the fan. It looks awful and very sloppy. I am going to remove it and take all of the putty off. Are there any reasons why I can't use silicone instead ? I do not think that the putty will leak, it just doesn't look very neat. Thanks for your advice, Ed.

The only disadvantage to silicone is that new silicone not stick to old silicone. So if there ever was a need to remove and replace all the old silicone has to be removed. Less of a factor these days is the reaction of the acetic acid in the silicone with metal; years ago there was more acetic acid in the silicone than today. The acetic acid helps it cure. However a high quality latex caulk seals as well, does not react with metal and can adhere to itself.

I would use polyurethane it sticks better.

I use silcone II (it isn't corrosive like I is) and have a love-hate relationship with it. Don's absolutley right about new silcone (or anything else I think) won't stick to where silicone has been before. A good polyurethane would be best I think, perhaps someone could chime in here and suggest one.

T

Sika makes high grade sealants. I have used Sikaflex 1a; an elastomeric sealant. I get it from a local metal roofing wholesaler. FWIW, generally a product called a sealant is superior to one called a caulk.

Sikaflex pro is a polyurethane sealant a though it's not an adhesive by rating it's a very good sealant and half the price of of sikaflex 252 11fc and it's other full adhesive rated counterparts

Is there any way to caulk or seal a 1/4 inch gap without making a mess?

I would consider making a contoured shim flange to level the mounting location, seal that and the fan flange and screw them in a sandwich. For weather resistance you could consider making the shim out of vinyl trim material or other plastic stock. This shim could be made from 3/8 x 2 inch stock front and rear, and the side pieces could be sanded into saddle profiles tapering to 1/8 inch thick in the middle. You might have to use slightly longer screws.

I went to Home Depot and the only Sikaflex that they had was in tan or gray. I bought some Dap caulk for windows and doors. I went to pull the vent back out and the putty tape that I used was apparently pretty strong and the fan would not come out without forcing it. I did not want to distort the metal so I left it in place. I ran a strip of painters tape around the roof approximately 1/4 inch from the lip of the fan. I carefully trimmed all of the excess putty that squeezed out from between the roof and the fan. I then ran a strip of painters tape around the top of the lip on the vent. I caulked all the way around the fan then ran my index finger around the lip between the 2 pieces of painters tape. I carefully peeled the tape off and it came out perfect. I let it dry over night and will check it tonight. It now has a double seal with the putty tape and the caulk. I saw a factory job that was done and they had warped the metal when they tightened everything up and I was so afraid that this would happen to me but thankfully it did not.I wasn't in a hurry. Thank you everyone for your advice and comments. Ed. ( next project a deep cycle battery so I will get a few days of use out of the fan. Any advice on that one? )