The Offshore Voyaging Reference Site

Deck Hardware Mounting Photo Essay

Time for a break from lithium batteries. Even if you readers don’t need it, your never-humble scribe does!

Also, it’s time we reminded ourselves that there are way more important things that contribute to a safe and fun offshore cruise. The best lithium battery system in the world will seem pretty insignificant if a deck fitting tears off the deck…or even if it just leaks over our bunk.

And because my fingers are tired after all this lithium battery blather, let’s make it a photo post…Johnny likes pictures…

Last winter I mounted several pad eyes and remounted two blocks on our new-to-us J/109.

Over the years I have done a bunch of this work on cored fibreglass boats, most notably every single damned fitting and track on my Fastnet 45 because the builder had not removed the core in the way of fittings, so it had compressed and the boat was a mass of leaks.

Still, even with all that experience, it always surprises me how complicated mounting fittings can be, and how many steps are required to do it right, as well as how much I learn each time.

Given that just about every fibreglass boat owner will be faced with this task, this will be useful to many of you.

And this project was particularly interesting because two of the blocks were mounted on angled Delrin shims that had failed.

Let’s dig in to what I did (with a lot of photos), including a few thoughts on things I could have done better. The day I finish a project convinced that I have done it perfectly will be the day I retire from boats—that kind of hubris is dangerous.

The Challenge

The jib turning blocks were mounted on Delrin shims that had, after 20 years, failed from sun exposure.

What a mess. Also note that the bolts are bent because the builder did not install a backer plate parallel to the base of the block, a common mistake when installing fittings at an angle.

And its gets really ugly underneath. At least Tillotson Pearson had removed the core, so no worries there. But then they had committed an all-too-common crime: Using over-sized washers instead of a proper backing plate.

The block might have been rebuildable but, as a general rule and particularly after 20 years, I believe in replacement, particularly of any deck fitting with moving plastic parts.

Sounds extravagant I know, but if we really want to get out there sailing, rather than spending all our time working on the boat, replacement is often the way to go.

There are few things more heartbreaking than going to all the trouble to fix the mounting right and then having the old fitting fail, particularly if, as is common, an exact replacement for the old fitting with the same bolt pattern is no longer available.

And that brings up another tip. One of the big advantages of replacement over rehab is that the new fitting can easily be repaired or replaced for more years into the future if it gets damaged.

New Angled Shims

So how best to replace the shims? Making a compound angled shim from plastic is actually quite difficult and time consuming, even for a machine shop. And, anyway, there’s a better way:

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Charlie R

I’d definitely appreciate more articles like this!
Any recommendations for folks that don’t have a drill press / etc at home?

Karl Lewis

I’d like to second that motion; and call for a simple voice vote.

Alan Bradley

Excellent article and excellent photos to illustrate all of the steps. More articles along this line would be most welcome. Thanks!

George L

All for it.

very useful

Michael Cilenti

Ditto! And the photos were very helpful. They do say a picture’s worth 1,000 words. This is exactly the kind of information I can apply to my own situation. VERY HELPFUL!

Justin White

That’s the one I have and, with care, it works great for most small jobs.

John, I’m 72 as well and just bought my first sailboat 2 years ago, ’91 Gozzard 31. I can’t tell you how valuable your articles have been, as I’m almost as nuts (technical medical term) as you are and I really appreciate the detail. More like this one 😉

Ben Logsdon

I appreciate the rationale of what to do (and what not to do) so I can apply it to other projects. Great write-up!

Also for non-leak goop…what’s your opinion on butyl sealant?

Scott Grometer

I use butyl (more specifically, ‘Bed-It’, which is a butyl hybrid), but typically in combination with the ‘over-drill holes/fill with epoxy/re-drill to fastener size/countersink/make butyl donuts around bolts to fully fill countersinks and seal threads/torque from bottom nut holding bolt/screw stationary’ method as inspired by Rod Collins.

I do this even with plywood coring (and always with foam or balsa coring) with the idea that any inadvertent leakage would be more nuisance than threat to structural integrity.

Of course, I don’t do this below the waterline!

…and YES, more articles like this please! Brilliant!

Scott Grometer

Hi John,
Here is the link to Rod’s rather lengthy (but informative) article on the topic of bedding with ‘Bed-It’:

He has a separate article that addresses the ‘Overdrill/Epoxy/Re-drill’ cores technique (which also discusses ultimate sealing):

I feel that the countersinking of holes AND only torquing the bottom nut (while holding the bolt/machine screw stationary – often requiring two people) is key to success. In my experience, the Bed-It material in the countersink chamfer will maintain sufficient thickness regardless of torque value AND if a sufficient ‘donut’ is used around the fasteners (well proud of top of chamfer), the Bed-It will be forced into the fastener threads upon said torquing.

I honestly do not trust ANY sealant 100% and put much more faith in the overfill and epoxy treatment of any hole in a cored area – especially with blind holes!

Thank you again for addressing this topic, and looking forward to more!

David Nutt

Having built and maintained many boats and sailed a bit including a 6 year circumnavigation I have done a fair bit of mounting and re-mounting deck hardware. I think this article is excellent and I think additional similar articles would be great for all of us to see regardless of out background.

Eric Klem

Hi John,

I see that we had some overlapping projects this offseason. We redid all of the hardware on our cabintop which included epoxy filling all the holes. Thankfully the original Butyl held up really well and there was 1 big leak requiring repair and 1 minor leak out of at least 50 fasteners with no hole chamfering. I am always amazed at how time consuming this sort of work is.

I totally agree on the importance of chamfering the holes. I have become a fan of Bed-It Butyl although it can’t be used for everything. Besides having a very good track record for long term sealing, I really like that I am not constantly opening new tubes and worrying about them drying out or aging out plus it is a lot less messy. The only failures I can think of were related to petroleum products breaking it down. Our boat even came from the factory with Butyl on the thru hulls and none were leaking when we got the boat although RC strongly discourages this sort of application.

I will have to try your method of the filled epoxy shim. I have always found it easy enough to just make a starboard or G10 shaped shim but I can definitely see the appeal and occasionally I run into a crazy geometry that is a real pain to make.

With regards to your controversial method of not drilling out the epoxy threads, I think it isn’t as bad as it might first appear because you are properly torquing prior to installing the nut which is key as it gets the bolt in tension. What you are doing is a little like using a jam nut which is never ideal but is a viable method in certain applications. The narrow jam nut (or backing plate for you) actually goes on the inside. It is a good idea to put a washer in the middle as not only does it provide a small amount of length to stretch, it gives a hard enough surface that with a little lubrication, you can get a proper torque.


Eric Klem

Hi John,

Yes, I think if you are torquing the bolt from the top, butyl will mess with the torque to tension relationship for 2 reasons. The first reason is that butyl does not give a nice low friction surface. The second is that butyl squeezes out slowly, especially when it is cold out so you can use it just fine at 30F but you need to do everything slowly. Given butyl’s properties, I think it may be dependent on how quickly you torque the bolt. Even when you are torquing a nut below, you need to wait a minute for the butyl to squeeze out on the other end before going to final torque.

I personally try to avoid torquing from the outside with butyl involved. My observation is that if you spin a screwhead with butyl on it, you can wipe a lot of the butyl out the top. I think the only fasteners that we have that are done this way are the stops for our jib tracks which are just screws in to the deck. We have always used butyl on them and then never leak but when I take them out, the butyl coverage on the taper portion of the head isn’t great but in the chamfer it is great and that does a plenty good job of sealing. I haven’t properly looked at this, I just know that I try to avoid spinning the screw head. Maybe butyl and your method of leaving the threads in the backing plate are not a great mix due to the need to torque from the screw side?

One other thought. I have taken to lubricating the threads where they contact the nut. Part of this is to get a nice K factor but an equally big part is that when using 316 hardware, galling can be a real mess both when assembling and if you take something apart mid cruise. Depending on what the hardware is, I will use tefgel or Loctite 243. The issue with doing this is if you have to take it apart you can get cross contamination. Butyl seems quite contamination tolerant (I have certainly tested it with way more dirt than is good a few times) and you can usually pull most of it off if needed so I replace a lot less screws than in the days of polysulfide where I replaced every screw I removed to try to get a good seal.


Eric Klem

Hi John,

Loctite does lower the K factor a little and maybe more importantly it makes it more consistent as there is a lot of variability in dry fastenings. I use 0.2 when using Loctite 243.

I am unaware of an industry standard K factor for tefgel. I have in my notes that it is okay to use the same torques as Loctite 243 but they don’t say a source and I can’t remember where I got that. My guess is that if anything, it is a little lower. For reference, anti-seize is generally in the 0.13-0.18 range and using 0.15 for calculations is relatively standard.

Boat life in an uncured state will likely do something similar to tefgel but I don’t know of a verified number that people are using. In engineering type applications, I don’t think that specifying having this on the threads would be very common although I know it is the way it is on an awful lot of boats.


Mark Wilson

More please. As someone who dreads drilling into a perfectly good deck that thankfully isn’t leaking at the moment I welcome all the advice I can get on keeping up the good work of others. The more detailed and specific the better.
And can I say, not in the spirit of criticism, that when a new article on lithuim pops up I am reminded of the the comment of one of JRR Tolkien’s fellow dons when he would read his latest chapter to them in an Oxford pub during the war «  not another ****ing elf ». Judging by the volume of comments to the lithium articles I am very much in the minority. However concerns over leaking decks are much more my thing. Romantic, eh ?

Kurt Mammen

Very timely article for me as I’m in the middle of mounting a couple of padeyes for jacklines and a new stronger bow cleat in a balsa-cored deck. Holes overdrilled and epoxy filled Will install hardward and G10 backing plates next week. I was on the fence about countersinking the holes so it was helpful to have your opinion and experience as well as others in the comments supporting that route. Also good to hear your experience, an others, regarding sealants. I’m intrigued by Eric Klem’s comments about
Bed-It Butyl as I’m loath to waste a tube of sealant for a few screws.

QUESTION FOR JOHN: How long does an open tube of Boatlife caulk stay workable for you (looks like a resealable top in your photo)?

Definitely interested in more such articles and in your readers thoughts and opinions on sealants – definitely a place to learn from experience as it takes years for us to run our own experiments!

Dick Stevenson

Hi all,
Another vote for Butyl Rubber, Bed-It, which I also get from RC/ Marine How-To. I have done all bedding on the deck for a decade now with BR and have been very pleased. RC’s site has a photo essay on its use, if my memory holds. My best, Dick Stevenson, s/v Alchemy

George L

Excellent essay. Thx

You may want to wear gloves, protective clothing , a breathing mask, and run a vacuum when you sand or otherwise work with semi-cured epoxy. Some people have pretty nasty allergic reactions to this stuff. When it has been cured with some heat applied, it is usually no problem.

I second measuring by weight using a postal scale. However, the scale might not be as accurate than the digital number imply. Mine jumps in 6gram increments, which matters in very small batches.

the filler powder isn’t great for your lungs, either.

Westlake sells epoxy paste, it works like a charm, but you need a mixing insert for your drill if you do more than a kg. Up to 3 kg at a time works well, with more, there may be premature curing due to exothermic heat. For small amounts, westlake has it in dual cartridges, which is really convenient. Up to 1/2 a kg, if your time has any value, it’s worth considering.

i use a sander where the vacuum connects directly (Festool has a really good setup with HEPA filter) that works really well when filling and fairing keel and rudders.

George L

Hi John,

It needs to be completely cured for it not to be toxic and depending on the formulation, it may get hard and strong at room temperature but not completely cured until the next really hot summer day.

West, obviously, if fine, having been around forever and successfully used in the boating context. Getting a custom consistency may also be useful.

I use EPIKOTE# Resin and EPIKURE# Curing Agent, and that has a perfect consistency for shaping and fairing, but it can also be used for gluing. Both have the filler mixed in and these chemistries with or without filler are used extensively for wind generators. I haven’t done a test, but I would be very surprised if there were a difference in strength. It ain’t easy sanding when its hard ;-(

The mixing is easy; the resin is yellow and the curing agent is blue; when your paste is a consistent light green, you are good.

Dick Stevenson

Hi George,
For some of us who are a bit confidence challenged, light green might be elusive. I can see myself adding a little blue: then a little yellow: repeat. Until the tubes are empty and I just have to go with the last mix. And then it will have started to kick off.
But good to know and I will take a look.
My best, Dick

Todd Edger

I too always countersink and love butyl tape. For thick shims I like to use 3M Marine high strength filler. It’s vinylester with glass fibers, and the right thickness right out of the can. Easy to mix, with no blush, and much less shrinking over time then epoxy. Unless you pre cure your epoxy with additional heat, the first time the summer sun heats that up the epoxy will shrink and there goes the torque spec on your bolt

Dick Stevenson

Hi John and all,
Back 40+ years ago West System also had great written instructions which were a great help in the beginning and I suspect they have just gotten better. I learned a lot and got many ideas from reading their support literature. And I appreciated feeling like I did not need a PhD in chemistry and materials use their epoxy and fillers/additives as did some of the other brands. I suspect there is excellent U-Tube tutorials by now also.
My best, Dick Stevenson, s/v Alchemy

Todd Edger

John I’ve been using West System product professionally in marine repair for 40+years. I know epoxy shrinks from both personal experience and from talking to the West System tech department. I called them about 30 years ago to ask why some repairs showed back up after a couple of years. They explained the shrinkage to me and suggested using heat lamps to post cure repairs to at least 120F on deck repairs that would reciever direct sunlight. Don’t take my word for it. Give them a call.

Vesa Ikonen

John, at least I dont see a link in your comment above.

Bob Hodges

Great essay John. I keep a sheet of G10 plate in my shop stash for making backing plates when needed.

I smiled when I saw the gel coat crazing. We also own a 2002 J/80 that was in mint condition when we bought her three years ago. We race her on lumpy/bumpy Lake Pontchartrain and we’ve seen a lot of crazing start which happens due to the normal flexing/expansion/contraction of the boat. Our Dragonfly’s has way better gel coat as it has just a couple of spots of it.

J/Boats are decently built but we’ve seen some stuff that raised our eyebrows. On the J/80, we saw rust stains coming out of the rudder pintle bolts indicating water intrusion. We removed the pintles and found the factory had mis-drilled the holes, re-drilled new ones, but had left the misdrilled holes as is and did not even bother to fill with a bedding compound. We fixed properly. The J/80 has a balsa cored deck so I always check around fittings and stanchions for core compression and delamination.



Frederick Gleason

We rebedded all deck hardware years ago. I suppose it is getting time to do it all again, not looking forward to that.

Since you like pictures, John, and so do I, it appears that I have to click on each and every picture in order to see it, otherwise it is a complete blur and indecipherable. I don’t know if this is happening on your end, but I don’t believe this is your intention. It ruins the reading experience. Sorry but that is my opinion.

I can understand if the picture becomes better and improves in quality over some time to allow download, but this is completely ridiculous.

Now to tell me it is some setting in my browser because my browser works properly 99% of the time with graduated pictures.