Sealing The Deck Core From Moisture (how to)

Hi All,

I know this subject comes up here a lot and wanted to share this with you you guys too.

For years I have been trying to describe, as have others, in words, how to "pot" or fill deck hardware penetrations with thickened epoxy to seal the decks core from moisture damage.

I have also been trying to describe why a slight bevel to each hole that penetrates the deck is a good idea. Sometimes folks understand it via words, and sometimes they don't.

I have had this article on my mind for years and finally over the last month or so had the chance to make it all happen with some late nights in the barn.

As far as I know this is the only article of it's type that uses deck lamination cut-a-way samples to show what goes on inside the deck when you "pot" with epoxy and countersink the bolt holes..

I hope this helps make some sense of something that really isn't all that difficult to tackle just difficult to describe..

If you see any typos, and I'm sure you will, please let me know and I'll fix them as soon as I can. I'm not a writer,:doh: but do have a lot of tricks & techniques I've learned over my years of boating that I like to share with fellow boaters. Some of these I feel can best be illustrated through pictures, with the help of some words of course..

Click this to read it:
Sealing Deck Penetrations To Prevent Core Rot (LINK)



And some of the photos from the article;

Very nice write up! I would like to suggest two other methods for sealing the holes from below to keep the epoxy from dripping. Small holes I have used disposable ear plugs to seal the holes. Try to get the kind with "skin" on them, they seal better. The other method is plumbers putty, held on with duct tape. The putty seals uneven surfaces really well but needs tape to hold it there. Both methods come off easy when you are done. RT

Great Job

I've never used Butyl tape. How is it used? Do you wrap it around the bolt before you put the bolt in the hole or stuff it in the hole then insert the bolt or what? It seems like a good alternative to sealants in a tube... and cheaper too.

Mike

This is a great piece--practically a gospel, like your thru-hull posting. The text is as clear and concise as pictures. Loved the closing phrase:

"Don't let the epoxy cure entirely or you'll need to remove the amine blush and this can be a royal pain in a small hole."

I also have butyl tape questions. Where do you get it? Does it come in different sizes? How do you know what kind to get?

B Tape

I've used it on my roof before, around chimney flashing, ice dam, it was very black. Assume it comes in white... but where white it's sold conveniently is another issue? The characteristic properties make sense, it's very self sealing, all most bullet proof at all temps.

Butyle tape is used in the trades. Very dense product.

It has sound deadening and insulating properties. I've had it taped over the backs of electrical/cable boxes in sound walls.
It's been used as a spot pad between a roof membrane and metal roofing where a fastener penetrates it.
You can buy pads of it from automotive stores to deaden sound on firewalls and door panels. Used a lot in the collector car market.
Small rolls can be bought at any quality roofing supply house. Some is even foil backed and suitable for wrapping pipes, though it starts to fall apart at temperatures above 200 degrees or so.

It never stood out as an expensive item.

John

I just remembered I bought a roll recently, 3/4" wide, from a glazier. It's used to seal window glass into metal frames.
FWIW

Butyl Tape

Great information--and as they say a picture is worth a thousand words! The group may get tired of my photo attachments to many of my postings--but they always help me get my point across!

Regarding Butyl tape, I have a friend that repairs motor homes and he ALWAYS uses butyl tape to seal windows, popup skylights, etc. It is cheap ($6.95 for a 10 ft piece--3/4 inch wide) and remains sticky, waterproof and pliable for decades. He only has gray and black colors--but believes it also comes in white (his comment is that white never matches anything--as few RVs are truly white). Plus he trims it from around the hatch or window and says color is not a big deal. So if your interested in trying butyl tape--you might visit your local RV dealer.

Thanks for reading my two cents worth!

Gary

Butyl Questions

This is an informative topic, and I appreciate the photos, Mainsail.

I seem to spend more payola on sealants than any other regularly used maintanence item, and I haven't found one I like using: the urethanes make too hard to remove whatever you are bedding, the polysulfides yellow and crack, and only a few brands come in small tubes, so there is a lot of waste. I like the idea of giving butyl tape a try.

If there is excess butyl, can you trim it away, or does it turn into a mess? Also, if there is any left exposed, does it continue to stick and leach off onto hands, feet, lines, etc? Lastly, will it pickup dirt and grime that settles on the boat?

When do you decide to use butyl instead of a tube sealant, and vice versa?

I think I can answer these.

- It can be trimmed.
- It probably will continue to be sticky and possible pick up dirt.
- Butyl is ideal for sealing items that need elasticity and do not require a strong mechanical bond.

Stanchion bases, cleats, turning blocks, etc all have primary mechanical bonds via screws or bolts. They all may flex with the forces being applied to them. Buytl's elasticity is much beeter than most liquid sealants.

I would not recommend using butyle below the WL.

Excellent write up-- answers many of my questions, especially when the epoxy sinks after filling the hole.

Thinking about your procedure - why do you inject unthickened epoxy then remove it and thicken? Could a little bit of unthickened go in then fill with thickened?