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Hi All,

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 further 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. There are many ways to do this but after filling literally hundreds upon hundreds of deck penetrations I have found this method to be the easiest..

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;





 

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Telstar 28
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Thanks Maine Sail...thought you had forgot about Sailnet... :)
 

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Butyl Tape

Wow, great writeup. Only questions I have concern Butyl Tape. Are all types the same (automotive, marine)? Are there better and worse brands? Good source? Seems like a heck of a sealant.
 

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Courtney the Dancer
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Maine- another great job! This is going to save a lot of people a bunch of time, money, and frustration. I potted and rebedded all of our deck hardware this year, wish I had known about the Dremel, I used allen wrenches that I cut off the short end to the correct length and used them in a drill. Worked OK for balsa but not plywood. I had read one of your earlier posts about potting which was invaluable and learned the rest "on the job".

Good job, John
 

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Discussion Starter #7 (Edited)
Thanks Maine Sail...thought you had forgot about Sailnet... :)
I actually thought I had posted it here:confused: and when I went to reference it for the genny track thread realized I had not..

Wow, great writeup. Only questions I have concern Butyl Tape. Are all types the same (automotive, marine)? Are there better and worse brands? Good source? Seems like a heck of a sealant.


Generally Ace, Lowe's, Home Depot etc. do not carry glazing quality butyl tape, at least in the North East, but they do sometimes carry butyl foam weather strip which is NOT the same as the rubbery silly putty like stuff and should not be used.

For butyl tape you'll usually need to order it online from an RV dealer or visit your local RV dealer and ask for it. DO NOT use black! Gray or off white in flat versions, not round, work best..:)

Here's a source:

RV Wholesalers - Off White Butyl Tape



This is the stuff I use
:
 

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Most window replacement/repair shops will have it and sell it.
 

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Thank you, again, Main Sail.

FWIW, I found a cream color butyl caulking at HomeDepot. Used it again last week, this time for chain plate leaks.
 

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Butyl Process

Thanks very much for the followup on the tape type and sources. I guess the only remaining question is how to make the Butyl tape meet the (through) bolt? All over the threads (like regular plumbing Teflon tape?), or squished up at the head end of the bolt like a traditional polysulfide caulk?
 

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Rhodes-

Squished up at the head of the bolt is better, since you don't want to seal the bottom of the opening, so that if water does get by the top, you'll see it dripping out the bottom, rather than it sitting there in between, testing how well you sealed the core. :)
 

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Excellent article and very timely for me because I've been preparing to install a pad eye in an area that is cored with balsa. I'm also planning to add another line clutch on the cabin top, but that area might not be cored. A couple suggestions for expansion, actually a couple questions:

All of the pictures show just a bolt, and in most cases something would actually be bolted down. Are there additional considerations for various types of hardware being bolted down?

Are there any special considerations in non-skid areas? Is butyl tape thick enough and plastic enough to make a seal without other preparation?

What is the best way to drill really perpendicular holes through the deck that in my case is about 1 1/4" thick. Really perpendicular holes would be important if there were a matching backing plate with two or more holes. I have a drill attachment for drilling perpendicular holes, but there seems to be more play in the attachment than I'd like. Because of that, I've had an aluminum drill guide fabricated with the same hole pattern as the pad eye and the matching backing plate. I'm wondering if there is a better way.
 

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Discussion Starter #15
Thanks very much for the followup on the tape type and sources. I guess the only remaining question is how to make the Butyl tape meet the (through) bolt? All over the threads (like regular plumbing Teflon tape?), or squished up at the head end of the bolt like a traditional polysulfide caulk?
1) Clean the deck and hardware with a strong solvent like Acetone. If hardware was preciously bedded with silicone you will need to sand to remove silicone residue.

2) Roll a small piece of butyl between you fingers until it's about a 1/8" diameter and wrap the underside of the bolts head.

3) Insert the bolt into the deck hardware.

4) Cut strips and lay the flat butyl tape across the entire bottom of the piece of hardware and around the bolts.

5) Roll a bigger diameter piece between your fingers and mold it into a cone around the bolts shaft on teh underside of the deck hardware.

6) Insert fitting while guiding the bolts into the holes.

7) Using two people, or the method of your choice for holding the bolts from turning, install backing plate and tighten the fitting down.

8) Use a heat gun or hair drier to heat the fitting (be very careful if it's plastic). This allows the butyl to soften and squish out better.

9) Re-touque through botls.

10) Clean up any squeeze with an X-Acto knife and tear it away.

11) For a very clean edge dampen a rag (DO NOT soak the rag) with paint thinner and wipe around the fitting. This will soften the butyl and create a nice clean looking install. You do not want the rag so wet that is softens beyond just the perimeter..

Here is a butyl cone fitting into a chamfered hole (on a bolt with no deck fitting):



 

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I got a chance to sit down and check out your web site and the info you have on sealing deck penetrations was very well done. Thank you for that. I also enjoyed the info on thru hulls and seacocks.

I would like to see deck re-coring, do you got anything on that?
 

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My Solution

Over the last couple of years I have rebedded all of my deck hardware. This is what i have done. While the epoxy potting works it is time consuming. Instead I buy phenolic tubing from US Plastics. It is available in various IDs and ODs. It is impervious to water. I buy the 0.5 OD with the ID to fit my fastner size. It comes in 3' lengths. Cutting to the appropriate length is easy with a band saw or hack saw. Then i simply over drill the mounting hole and epoxy the phenolic insert about 1/16 inch below deck level. Then thru bolt the hardware with sealant. simple, quick and easy. Even works with balsa core. No more core rot , ever.

remember you heard it hear first.
 

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Unfortunately, this really doesn't do a very good job of sealing the core IMHO, since any heavy loading on the area may break the epoxy bond to the phenolic tubing, allowing water to enter the core. Also, this probably doesn't solve the problem of the lack of compressive strength that potting the holes with thickened epoxy does. The core materials, balsa and foam, have fairly low compressive strength.

Over the last couple of years I have rebedded all of my deck hardware. This is what i have done. While the epoxy potting works it is time consuming. Instead I buy phenolic tubing from US Plastics. It is available in various IDs and ODs. It is impervious to water. I buy the 0.5 OD with the ID to fit my fastner size. It comes in 3' lengths. Cutting to the appropriate length is easy with a band saw or hack saw. Then i simply over drill the mounting hole and epoxy the phenolic insert about 1/16 inch below deck level. Then thru bolt the hardware with sealant. simple, quick and easy. Even works with balsa core. No more core rot , ever.

remember you heard it hear first.
 

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Discussion Starter #19
Over the last couple of years I have rebedded all of my deck hardware. This is what i have done. While the epoxy potting works it is time consuming. Instead I buy phenolic tubing from US Plastics. It is available in various IDs and ODs. It is impervious to water. I buy the 0.5 OD with the ID to fit my fastner size. It comes in 3' lengths. Cutting to the appropriate length is easy with a band saw or hack saw. Then i simply over drill the mounting hole and epoxy the phenolic insert about 1/16 inch below deck level. Then thru bolt the hardware with sealant. simple, quick and easy. Even works with balsa core. No more core rot , ever.

remember you heard it hear first.
I agree with Dog on this one. You are really only creating a very, very thin epoxy bond to the balsa or foam of which is a very poor bond when compared to the deck skins and first filling with un-thickened epoxy then thickened which creates a very strong bond. You also cut away both the top and bottom skins when over drilling and have multiple different expansion and contraction coefficients between the balsa, poleyester resinated fiberglass, epoxy and the plastic plugs.

Part of the whole process of potting the holes is for the viscous un-thickened epoxy to penetrate the pores & surface of the core to create a sealing & bonding layer. Then the thickened epoxy is injected creating a strong bond to the deck skins and a decent bond to the core.

I'm guessing you simply slather the plugs with epoxy and stick them in the holes? In this case gravity will be against you and the epoxy will do as it should, run down hill, thus potentially leaving unprotected & unsealed areas of core.

Personally I don't see how this is any easier than a simple over drill, then an injection with thickened epoxy, which would bond and seal better. You are already mixing epoxy, and as you stated, you'll need a band saw or the ability to cut the plastic rods. The only addittonla tool needed for injection is a $2.00 syringe. The mixing of the epoxy & thickener takes about 20-30 seconds. Like anything it's the prep that it time consuming..
 

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I agree with Dog on this one. You are really only creating a very, very thin epoxy bond to the balsa or foam of which is a very poor bond when compared to the deck skins and first filling with un-thickened epoxy then thickened which creates a very strong bond. You also cut away both the top and bottom skins when over drilling and have multiple different expansion and contraction coefficients between the balsa, poleyester resinated fiberglass, epoxy and the plastic plugs.
Good point MS... :)

Part of the whole process of potting the holes is for the viscous un-thickened epoxy to penetrate the pores & surface of the core to create a sealing & bonding layer. Then the thickened epoxy is injected creating a strong bond to the deck skins and a decent bond to the core.
The thickened epoxy also gives the area a lot more compressive strength than the original core material would have.

I'm guessing you simply slather the plugs with epoxy and stick them in the holes? In this case gravity will be against you and the epoxy will do as it should, run down hill, thus potentially leaving unprotected & unsealed areas of core.

Personally I don't see how this is any easier than a simple over drill, then an injection with thickened epoxy, which would bond and seal better. You are already mixing epoxy, and as you stated, you'll need a band saw or the ability to cut the plastic rods. The only addittonla tool needed for injection is a $2.00 syringe. The mixing of the epoxy & thickener takes about 20-30 seconds. Like anything it's the prep that it time consuming..
As MS states, you already have the epoxy... any time saving from not reaming out the core is taken by having to buy and cut the phenolic tubing... and the potting method I use and MS describes results in a much better solution long-term.
 
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