Limits of butyl putty tape?

[pindraak]

After reading about silicone in threads here, I have spent the last two days in hard labor removing all the lights and water/electric hatches on my Bigfoot 17. There was a lot of useless stuff tacked on to this trailer over the years, and a lot of silicone glopped on.

What I'm wondering is why put on any sort of caulk-like sealant? It seems like if the item you are screwing or clamping down onto the surface has a flat border/edge that can squeeze the putty and it is secured properly, it's sealed. Trying to bead stuff around the edge seems irrelevant or worse.

The only items on my trailer I see that are exceptional are the tail lights. There is a narrow sheet metal edge that contacts the trailer and it looks like the putty tape will be useless.

Could there be cases where the item has to be screwed on so hard that too much of the putty gets squeezed out? I am looking at screwing down an aluminum plate over all the holes made by a hatch and drip cap I removed.

[Carol H]

Ken, All I can tell you is over the past few years I have slowly taken off a number of things on the trailer that had caulking around them - fan, water supply, awning etc and I have used only butyl when putting them back on and have not had any leaks.

Your queston re the tail lights caught my intreast though as I have taken mine off to replace the bulbs and noted there is no putty or caulking used on them. Thinking of replacing the whole units and wondered about whether or not they should be sealed on.

[Richard Hayes]

Could there be cases where the item has to be screwed on so hard that too much of the putty gets squeezed out? I am looking at screwing down an aluminum plate over all the holes made by a hatch and drip cap I removed.

Hey, Ken,

I can't speak from experience with trailers, but I have done a lot of work on sail and powerboats as an assistant to a friend who has made his living doing it for over thirty years. Butyl tape is amazing stuff - you can stretch it to thin it out, roll it into ropes, double up thicknesses, make doughnuts to seal screw heads - and it stays flexible darn near forever, unlike silicone which goes rubbery. It's also far better for adhesion, and can take far more flexing than cured silicone. I have scraped butyl off boat decks and fittings that was forty years old, and it was as pliable as the day it was installed. I've also seen butyl completely seal copious deck leaks in a 45' sailboat after we'd removed, cleaned and reseated every single item of deck hardware - perhaps 400-500 holes in all! They'd been seated in some sort of goop that went hard and cracked over the years. (You don't even want to think about what it cost the owner to get that multi-day job done )

Re your question - if you have any doubts about it sealing the plate, can you place another strip of tape inside the contact one, use a double-thickness strip, or roll a "rope" that would allow a bit of butyl to squeeze out on either side once the plate is seated? Don't overtighten the fasteners - snug does the job just as well as cranked down hard! Once you see tape starting to squeeze out, that's tight enough. You might want to make little doughnuts of rolled butyl to go under the screwheads. Just trim the exterior excess tape from around the edges of the screws and the plate with a sharp knife, and keep an eye out for leaks for a few days...

Finally, if you want to apply butyl where silicone has been, make sure it is thoroughly cleaned - we use fine sandpaper, followed by a scrubdown with alcohol, to get the residue off. Any lingering trace of silicone, even an oily film, will really interfere with the tape's adhesion.

[Darwin Maring]

When I remove the taillight lens there are noseaums and other bugs in there. If the assembly was not sealed to the trailer I suspect these things would migrate inside the egg.

My preference is to use Butyl tape as Richard above has outlined. I assume the manufacture does not use Butyl tape because of the time constraints, labor and product cost. So much easier to use a caulking gun, slap it on and let the customer worry about it.

[pindraak]

Well, the plate is not quite working. Half the screws don't have enough to bite into to really squeeze the tape without tearing up the fiberglass and plywood underneath, as I can hear it cracking. I guess I'll put a piece of plywood inside and use bolts.

[Richard Hayes]

Originally Posted by pindraak

Well, the plate is not quite working. Half the screws don't have enough to bite into to really squeeze the tape without tearing up the fiberglass and plywood underneath, as I can hear it cracking. I guess I'll put a piece of plywood inside and use bolts.

Bolts are good - screwing into FG is a very ticklish business. You can doughnut the heads of the bolts to make sure they're sealed. On the boats, we just make sure we have a generous thickness of tape in whatever shape works under whatever we want sealed,then screw/bolt it down until some tape oozes out. Let it sit a day or two, then lightly tighten again. Trim off the excess...

[pindraak]

Yeah, I noticed how the stuff squeezes out some more. I'm wondering if everything will need to be tightened more once it gets really hot out.

[Richard Hayes]

Originally Posted by pindraak

Yeah, I noticed how the stuff squeezes out some more. I'm wondering if everything will need to be tightened more once it gets really hot out.

Don't have much experience with "...really hot out" here in Newfoundland, but I'd think not - the stuff allows lots of flex for expansion and contraction, grips like crazy, and you don't want to thin it right out. I'd be inclined to tighten just a tad after a few days or first use, then leave well enough alone unless I had a leak. You can always add a half-turn or so later if needs be...

[pindraak]

That makes sense. I'm planning to take my Bigfoot from the southwest up to Newfoundland this summer. I tried to drive the entire trans-Canadian one summer a few years ago, but fizzled out in New Brunswick.