Butyl tape - what is it exactly?

[Misterbreeze]

I need to bed down through-bolted deck stanchion bases so called into my local chandler to get some butyl tape having read that it would be the best thing for this sort of job, but they'd never heard of it. I then googled it and found stuff used by builders for guttering, and it seems self-amalgamating tape is also butyl. Should I use either of these? Or would a non-setting mastic strip as used for caravan windows do the job?

 

[coopec]

I'd switch chandlers!

In your googling you probably saw this too?

"Butyl tape is a synthetic rubber adhesive manufactured to upgrade natural rubber adhesives. Compared with its natural counterpart, butyl tape is less sensitive to varying temperatures and maintains its stickiness at lower temperatures than traditional rubber adhesives."14 June 2022
What Is Butyl Tape? Everything You Need To Know

You don't say what your deck is made of- steel, fiberglass, timber?

My deck is f/g so I epoxied a sheet of f/g (same size as the stanchion base and 6mm thick) to the deck then used butyl tape to seal the fg/stanchion base joint

 

[coopec]

Maybe have a look at this?

Bedding Deck Hardware Using Through Bolts & Butyl Tape

 

[coopec]

Here it is!

14 Aug 2019 — Our solution is to raise the stanchion base 1/2 or 3/4 inch with a piece of solid GRP stuck in place with epoxy or 5200. The stanchion is bedded ...

Decks leak

 

[LittleSister]

I then googled it and found stuff used by builders for guttering, and it seems self-amalgamating tape is also butyl. Should I use either of these? Or would a non-setting mastic strip as used for caravan windows do the job?

I am no expert but my understanding is as follows. (Happy to be corrected.)

Butyl tape that I've used is indeed the stuff sold for sealing caravan (and boat, funnily enough) windows. As far as I can make out it is just a butyl sealant in a more convenient (and much less messy!) form for that sort of a job.

The self-amalgamating tape that I have used may well be made out of butyl, for all I know, but is something different - it is supposed to stick to itself, but not to other stuff. Wouldn't be good for sealing your stanchion bases, I would have thought.

You can get butyl sealants in tubes, which are easier to use in some applications. I imagine either tape or tubed sealant would be OK for

The advantage of butyl is it stays flexible long term (except where exposed to air - where it forms a crust), accommodating movement (e.g. stanchions being yanked about, GRP flexing, and differential expansion of different materials. It can also be relatively easily removed again in future. It isn't a strong adhesive like Sikaflex [insert number I've forgotten here], which might well help to hold down your fitting, but also fail to release it without tearing the gelcoat off the GRP if you ever need to remove it again. (How do I know that? )

 

[penfold]

Self-amalgamating could be used, you could cut lengths and overlap them on a easy release surface(wax paper or a bit of heavy polythene) to make a sheet large enough to cut out the desired gasket. It would be a right old palaver though.

 

[KompetentKrew]

I bought Arboseal butyl glazing tape - at the time Dortech Direct were the cheapest UK supplier.

I'm sure I read of at least one other YBW-addict using the same brand.

The MarineHowTo guy claims that his brand of butyl tape is "specially formulated" because they changed the formula of regular butyl tape "to comply with regulations". However, he gives no further details of the formulation (when I checked) and he's in the US, so we have no idea if UK & EU regulations are the same.

The Arboseal looks like the right stuff - it's 3mm and like a thick putty, and it looks like it'll behave the same as the stuff in the MarineHowTo picture guide. I haven't actually used mine yet. I bought white, but I think I'd buy black if I was buying again because the edges of the white will probably get grubby.

 

[coopec]

Maybe neoprene gasket (glued to the deck) would be the way to go?

Stanchion Gasket / Bedding - Cruisers & Sailing Forums

 

[CrossedThreads]

I use Buty tape to seal the toe rail and stanchion bases on my Bavaria 38. Not tested it in anger (been doing it over the winter) however in a previous hose test it could have been described as a leaky sieve. Now it’s bone dry. I bought this from Amazon:

LLPT Butyl Seal Putty Tape Black 3MM Thick x 19MM Wide x 10M Thick for Leak Proof RV Repair Window Glass Boat Sealing EPDM Roof Patching (BST343)

Strips on bases of the rail and bases. Wraps around all of the screws. I did use sika 212? In the screw holes for a belt and braces approach.

 

[RunAgroundHard]

I look for the stuff that has the same colour as blutack but is stiffer to the touch. Used it successfully on frame mounts for a cockpit spray hood and bimini base. They had been problematic in the past getting a good seal, but now they are water tight.

Mentioned in post number 7, from KompetentKrew, Bedding Deck Hardware With Bed-IT Tape - Marine How To This is the definitive article on bedding with butyl.

 

[TSB240]

I have been using butyl tape for all sorts of boat sealing and repairs including bedding fittings, windows, sealing mast at deck entry and most importantly repaired a blown exhaust elbow.

Radon/DPM Double Sided Butyl Jointing Tape 50mm x 10m | Toolstation
It is 50mm wide. It sticks like s**t to anything that is dry including itself. It is blue in colour not black.

It remains flexible and can withstand the heat of a blown exhaust elbow.
My temporary exhaust repair was good enough for me to get back from the western Isles to North Wales using engine at full power for some extended periods.

It is much easier to apply than liquid butyl and can be built up in layers if you need a greater thickness gasket.
I don't have leaking stanchions but wouldn't hesitate to use it if I did.

I last used it sealing our keel stepped mast at deck, cured a leaking deck hatch joint, fixed a salon sealed window and a cockpit table floor pedestal mount.

It remains flexible and never hardens. It is an annual routine for me to check tightness of anything I have mounted with it. A tweak on a screw or tighten bolt a little and any seal will be maintained.

It should be in everybody's spares box!

 

[Daverw]

Black version is available from Screwfix

 

[dankilb]

I do think the distinction needs to be made between 'repair'/'jointing' tapes and 'sealant'/glazing tapes. Glazing tape is much thicker and deforms more readily (indeed, completely - depending on clamping force). It is arguably the 'right' product for bedding a deck fitting (whereas amalgamating repair tape is right for repairing a leaking hose).

AFAIK glazing butyl tape (such as Arbo GZ) is not available from Screwfix/Toolstation and is not that likely to be stocked in chandlers. You would need to find a local glazing supplier or order online. The black repair tapes really are not a like-alternative.

 

[DangerousPirate]

Short answer: The invention of gods

Slighty longer answer: It's kneadable, play-dough type of mass that never dries out. It sticks to a dry surface, especially well on smooth surfaces, and gives you a perfect seal. We generally use it as an alterative to acryl or similar, it's so much easier to apply and way less messy. Just cut/rip/knead to size, squish it in, tighten the screws (or whatever) and scrape of the excess (and put it back on the roll).

I use it a lot.

 

[Daverw]

The stuff from Toolstation / Screwfix is not a repair tape, it’s fully kneadable like putty, I’ve used it for years and it’s perfect and easily available

 

[dankilb]

The stuff from Toolstation / Screwfix is not a repair tape, it’s fully kneadable like putty, I’ve used it for years and it’s perfect and easily available

For a boat literally covered in deck fittings - I’d still advise the OP to source the right stuff for this job (a butyl glazing tape in a suitable profile) rather than forming it from amalgamating rubber tape.

Unless you are referring to something they no longer sell (or doesn’t come up when searched for).

 

[Daydream believer]

Surely butyl tape is not the correct material for stancion bases,. Unlike, say, windoes etc.,sStanchion bases are likely to be subject to flex. This will have the effect of extruding the butyl out of the joint. If air & water then enter the resulting gap, it will it not have an effect on the structure of the material over the longer term? Would that then lead to further leaks, along with a release of the fitting?
Of course if the butyl were to be applied from a mastic gun, hence, far more pliable & extruded at the time of fixing,: such that it was more of a gasket rather than a packing; then the issue might be avoided. That is the solution I would prefer.
Only an opinion for discussion perhaps.

 

[andyc352]

I need to bed down through-bolted deck stanchion bases so called into my local chandler to get some butyl tape having read that it would be the best thing for this sort of job, but they'd never heard of it. I then googled it and found stuff used by builders for guttering, and it seems self-amalgamating tape is also butyl. Should I use either of these? Or would a non-setting mastic strip as used for caravan windows do the job?

In my experience, chandlers don’t stock it. Maybe because it doesn’t have “marine” on the label and is so cheap. It’s the best stuff for bedding deck hardware. Available in black or white and various widths, I get mine from Dortech Direct.

 

[PetiteFleur]

I've used Butyl tape for all sorts of sealing on my boat. Windows, deck fittings, hull fittings including refitting the P bracket for the prop shaft. In some instances I've fitted a stainless washer between the fitting and grp so the sealant is not squeezed out completely. Not had any leaks at all. I'm a fan of butyl tape.

 

[zulloboy]

Over ten years I have rebedded every deck fitting with butyl and had one leak only - which was due to my lousy workmanship. They have successfully endured hundreds of "green-water-over-the-deck" events.
The trick is that less is more - making a great big gasket means it can be hard to compress it enough. I form it into "o-rings" to go around the bolts (big enough radius so it doesn't squish into the thread).
Forget neoprene as a previous poster asked - my boat's PO used it and it leaked badly after a couple of years. Butyl's shelf life is forever, so don't worry about the price - just remember all those barely used tubes of Sikaflex you've had to throw out.

Cheers, Graeme