Butyl Tape

[ebb]

[later edit: later posts generally have more up-to-date info]
OFF-WHITE trimable butyl rubber tape is hard to find.
Some sources are not clear about the difference between putty tape and butyl tape NOT interchangable.
Putty tape is never used on a boat, it is oily and gets hard. Butyl rubber tape stays sticky & pliable forever.
Butyl rubber tape throws no oil and is impervious to water.

Getting ready to mount the lexan slab-on windows to the cabin side.
Positive I will attempt white tape for the frameless 'slab-on' lexan lights to the cabin.
Will also use it to imstall flanged Bomar hatches.
Use it between fiberglass and any metal hardware. Use it for seacocks and thru-hulls.
More common gray or black butyl tape can be used here.
It stays sticky forever and gets stickier as it ages.

Butyl is not adhesive. You will always be able to remove it.
Read on the net there is a growing cadre of skippers who have rediscovered this material.
It's imco a much better all-round caulking material than the highly advertised and expensive marine sealants.

The tape is used to make a thick controlled seam. It is difficult to squeeze the stuff out when something is flat against flat like a cleat base.
We're using the caulk to make a rich waterproof seam. It is a sticky clay-like substance so it is possible to squeeze 90% out with the sustained clamping action of bolts. You want caulk to remain in the interface. You can insert an EPDM rubber washer or O-ring on your fastening as a spacer in the caulk to help keep a 'butyl line' while cinching up the work.
The butyl is softer as temperature rises. As you unnroll, the cooler it is the more likely it will keep its shape. If you pull and stretch it, which it likes to do, it gets thinner.
You can stack the tape. make seams by overlapping,
but it can take considerable force to to get squeeze-out, but not too much squeeze-out.
There is a bell curve. Most flat tape can be teased around corners (like our cabin windows) without distorting it too much.

Your heirs will be able to take anything butyl apart without consigning you to the depths of hell.
So if you do manage a leak it is relatively easy to take the damn installation apart again.
Have used tube butyl in conjunctiion with tape butyl. Won't use tube butyl to mount anything.
Because it is less stiff and will act like polysulfide and polyurethane caulks which, as you know, gets squeezed too thin with very low pressure from fastenings.
Tube butyl is cleaner to use, wipes up with mineral spirits, the whole exercise is less messy than with synthetic rubbers. A tube of roofing butyl will set you back $4, not $24.
The 1" wide butyl tape we've just ordered (3/11) comes in 30' rolls for $7.

Elixir Trimable Butyl Tape 180
off white 48462 1/8" X 1" X 30'
Recreation Vehicle Accesories.
Denver, Colorado

There are other widths and thickness.
Trimable means you can cut the squeeze-out away with a plastic spatula, something that comes to an edge but isn't sharp.
Some butyl tape used for roofing comes with plastic cloth inside. That you can't separate without a knife, and you don't want to do that. Also becomes messy.

Once got butyl tape from an RV supply that charged me 3 times over what the above supply did. Shipping was MORE than the product!
Also, pleasantly, R.V.A. came with a very knowledgable and friendly order taker.
The overcharge source shipped in a carton that allowed the tape to get badly smooched out of round which makes it a PITA to use. Glues the release paper and concentric layers together.
It's difficult to ship - so ask for careful packaging.