Bedding Hardware

As anyone that has owned a boat probably knows, mounting (or re-mounting) hardware on the exterior of a boat isn't as simple as just screwing it into the hull.  In many cases there will be some stress placed on whatever you intend to mount, so drilling all the way through the hull and putting a backing plate on the hardware is required to distribute the load across the fiberglass.  And, of course, holes invite water leaks. Even in simple or more cosmetic hardware, simply screwing into the hull results in a hole that can cause problems if water enters...and you are on a boat so chances are water will enter.  For a boat like mine that is "cored" (the fiberglass structure is strengthened while keeping weight down by placing a lightweight substance like cork or foam between two layers of fiberglass), water getting into the fiberglass laminate can result in expensive repairs.

To prevent water from entering the hull, you "bed" the hardware.  All this really means is that you put some form of sealant on the hardware around the hole so water hopefully won't get in.  This sealant can take many forms and different options may be used depending on what you are attaching to the hull (one obvious difference would be items above or below the waterline).

During our survey, there were a few items noted that needed to be re-bed.  A couple handrails were found to be loose and the moisture meter detected some slight moisture around one of the stantion bases.  All of this is above the waterline so I did a bit of research on what would be good to use and figure I could do this without an experts oversight.  People mention 4000 and 5200 (a couple adhesive sealants from 3M designed specifically for marine use), as well as various forms of silicone or silicone-like substances.  The important things seem to be that the material be resistant to UV (imagine that...boats sit out in the sun), be flexible, and able to tolerate the marine environment (water, salt, etc.).

After doing some reading, I decided to give butyl tape a try.  It sounded fairly easy to work with, adheres well, can be removed without damage, and lasts a long time.  The down side appears to be that you are supposed to compress it fairly slowly, so it takes some time and patience to mount each piece. Since this will be my first attempt at rebedding hardware, easy to work with had me sold. And, of course, there are good butyl tapes and bad ones.  I found someone that sells what is supposed to be good butyl tape and his web site has great instructions on how to use it so I decided to order some.  You can check out the web site below:

http://www.pbase.com/mainecruising/rebedding_hardware
(if you want the Bed-it butyl tape, you can order it at the end of page 3)

A lifetime supply of butyl tape?

For my first re-bedding attempt I decided to fix a pair of...hmm...can't really call them pushpit rails can I?...handrails on the back sugar scoop stairs and swim platform.  These were noted as loose on the survey, are obviously loose, and may be the source of some water I'm finding in the engine room bilges. No huge structure or disassembly of the interior to contend with so they seem like a good first place to try.

I remove and clean the starboard side rail and around the mounting holes.  I take about an inch worth of the tape and roll it into a relatively thin rope shape and put it around the bolts on the rail like it shows to do in the above web site.  Reinsert the bolts into the mounting holes, apply the backing washers and snug up the nuts.  As advertised, the butyl tape slowly squishes.  I spend the next several hours, while working on other projects, periodically (every half hour or so) going down into the transom to tighten the nuts just a little bit more.  The web site said this could take days and not to rush it and I didn't think I did, but the rail seemed to be tightened down as far as I think they should be after just 4 or 5 tightening attempts.  Even though I didn't put a particularly big band of the stuff on (somewhere between 1/4 and 1/8 inch diameter was used) a large percentage of it did ooze out from under the rail's mounting flange. Using my fingernail to sever the connection between the oozed butyl and what was still under the flange, I carefully removed the excess.  And as advertised, this stuff is sticky...at least sticks to my hands, itself, the railing, and the gel coat of the boat.

After the first tightening, it is just starting to squish out.

Fully bedded, still need to clean up a bit.

I would like to tell you that the port side railing went just as easily, but when I went to remove the nuts, I found one of the bolts had been snapped off and there was no bolt or washer.  So, in true boat project fashion, I find another issue while fixing one (actually...guess I should be happy I only found one more project...seems I usually find two or three).  Guess I'll see if I can find a welder or machine shop that can put a new bolt on the railing for me.  I put some tape over the holes where the broken railing was, put the broken railing in the trunk of my car so I can take it to a welder and it won't get scratched up in the meantime.

As for the bedding, it was pretty easy and if this stuff really doesn't harden or loose it's stickiness, I have high hopes that it will be a good solution for a long time.