Refinish Your Swing Keel for Best Performance – Part 5: Installing

This post is the continuation of Refinish your swing keel for best performance – Part 4: Sealing and painting and the last post in the series. I describe: how to prepare the hull, tips for keeping the keel centered in the trunk, the proper method to tighten the hanger bolts, and end with a materials list and a brief project cost analysis.

Before I get started, a bit of legal housekeeping. This post contains affiliate links. That means I receive a small commission if you make a purchase using these links. You can purchase the products anywhere you like, of course. For a complete explanation of why I’m telling you this and how you can support this blog without paying more, please read my full disclosure.

Prepare the hull

Before I bolted the keel back in place, I prepared the hull to receive the refinished keel. Part of that job was cleaning and painting the keel trunk and slot as I described in the previous post. More specifically though, I also prepared the keel hanger weldments to go back in service.

Keel hanger pockets and hanger bolt weldments molded into the hull
Keel hanger pockets and hanger bolt weldments molded into the hull

The first obstacle that I encountered was one of the weldments that protruded about 1/16″ from the surrounding fiberglass. This meant that the keel hanger didn’t sit flush in the molded pocket. Instead, that end was supported only by the weldment, not a stable connection for the 550 pounds of keel to pry against. It must have been that way since the sailboat was made. The other three weldments were flush and looked like they had been machined flush. Only the protruding weldment still had a chamfer around the outside edge and makes me wonder if somebody missed it during manufacturing.

The next time you remove your keel hangers for inspection or maintenance, check that the weldments are all flush with the surrounding fiberglass.

To make the weldment flush like the rest, I used the largest twist bit that would fit in my portable electric drill and reamed the end close to flush. I finished up with a small sandpaper drum.

BEFORE - Weldment extends beyond the hull surface
BEFORE – Protruding weldment prevents proper bracket seating

The second issue was a problem that I had with the hanger bolts the last time I replaced them. The two bolts on the port side would not screw all the way into the weldments. The bolts on the starboard side screwed in completely. I measured the depth of the weldments and they were all the same, 1″ deep. All of the bolts were also the same length. I was stumped for a while until I noticed that the countersinks in the port side hanger were deeper than the starboard side hanger. Aha! I thought, and shortened the port side bolts by 1/4″ and then they fit. Or did they?

Unequal countersinks when combined with incompletely tapped weldments
Unequal depth countersinks between the two hangers

This time in anticipation of installing new bolts again, I cleaned the threads thoroughly to remove any filings, dirt, or LOCTITE residue. I used a paint gun cleaning brush, acetone, and compressed air. With the keel out of the way, I was able to look more closely up into the weldments and I discovered that the weldment threads stopped 1/4″ short of the end! The starboard side weldments were tapped all the way to the end. That’s actually why the bolts wouldn’t fit. The real problem was only made worse by the deeper countersinks.

Check that your weldments are tapped completely and that the bolts seat deep enough to hold the hangers tight.

To resolve the bolt problem once and for all, I used a 5/16″ – 18 tap and cut new threads the rest of the way in the problem weldments.

The moral of this story is don’t assume your sailboat was built to precision tolerances and highest quality. Maybe the manufacturing department of Catalina Yachts had trouble keeping up with sales in 1981. That was in the middle of the C-22 heydays when 1,000 were built each month—that’s a lot. Here on my boat alone were three defects in the keel attachment to the hull, not a good place to cut corners or compromise quality.

Keep it centered

In the picture below, you can see where the keel used to scrape the inside of the trunk on the port side when the keel was lowered. The worst gouge is through the gelcoat and into the glass mat. These pictures were taken before I painted the inside of the trunk and the keel slot with epoxy primer and bottom paint, which resealed the fiberglass.

Originally, there were no centering spacers on the keel and there was about 1/8″ of clearance between the keel and the hanger brackets on each side. Obviously, that was too much play side to side and it allowed the keel to scrape the inside of the trunk.

Scrapes inside the keel trunk from uncentered keel
Scrapes inside the keel trunk from the keel not being centered. The tip of the keel lock bolt is also visible in the top of the trunk.

To prevent future scraping and to reduce the stress on the hanger brackets, I bonded centering spacers to the keel as described in the previous post in this series. Fairing the keel reduced the clearance to the brackets to 1/16″ on each side. I fabricated a 1/8″ thick washer out of scrap fiberglass to shim the keel to the starboard side during installation for the best fit of the centering spacers.

Fiberglass washer on the pivot pin to eliminate keel sideways movement. Lines are drawn across the bolt heads with a permanent marker to make monitoring for loosening hanger bolts easy-peasy.

Then came the hard part

That is, getting the refinished keel back into place under the slot and ready to bolt up to the hull. Basically, I reversed the process that I followed when I removed the keel as described in the first post of this series. Installing the keel is more difficult than removing it. Getting everything to line up just right takes lots of little adjustments of the keel’s position. This job is much easier with a helper.

Before I bolted the hangers back in place, I packed the bottoms of the pin holes with Sta-Lube marine grease. I used just enough so that it would squeeze along the length of the pivot pin when inserted into the hangers without excess.

Tighten with care

I used new bolts in the hanger brackets and applied blue LOCTITE on the threads before I used a torque wrench to tighten the bolts to 12 ft. lbs. That is one half pound over the maximum recommended dry torque specification for 5/16″ – 18 stainless steel bolts according to the Engineer’s Handbook and fastener distributors like Fastenal. I have yet to have a bolt loosen when torqued to 12 ft. lbs. When you consider that the LOCTITE acts as a lubricant during tightening, that’s probably about 25% over the maximum recommended wet torque, which is lower than dry torque due to the lower friction.

Some owners tighten their bolts to 20 ft. lbs. (74% over maximum) without problems. In the past, the owner of a certain online Catalina parts retailer has recommended 30 ft. lbs. (160% over maximum). The Owners Manual insert that came with my ’81 C-22 recommends 35 ft. lbs. That’s three times the maximum specification and more torque than recommended for the strongest bolts you can buy, SAE Grade 8 medium carbon alloy steel! The really scary part is that, unless you shear a bolt off while overtightening it, it is likely to only partly weaken and then snap when its put under a load when your boat is in the water. You won’t even know it happened. Then its sister bolt is under double the load and also likely to snap, especially if you overtightened it too.


I can say from experience that torque of 30 ft. lbs. or more shears stainless steel bolts off easily, either when tightening or loosening. DON’T DO IT.

Extracting a broken stainless steel bolt is very difficult and runs the risk of damaging the weldment threads. Replacing a damaged weldment is even more difficult. Instead of brute force, rely on lock washers, LOCTITE, and regular inspection to keep the bolts tight enough.

Here’s a tip that I use to watch for loosening bolts. After torquing the bolts, draw an index line across the hanger bolts holes and through the center of the bolt heads with a permanent marker like in the picture above. Then you can tell at a glance if the bolts have loosened.

Repair or replace the lifting hardware

All that remained was to install a new winch cable. If you do this project and you reuse your existing cable, be sure to install a new cotter pin on the cable fork. Don’t rely on the old one to keep your keel attached to the cable.

Turning ball cleaned, lubricated, and reinstalled
Turning ball cleaned, lubricated, and reinstalled

Here’s a money-saving tip: I saved over 70% on the cost of a new keel cable by having an industrial rigging company make it using the same materials as opposed to buying one from that online Catalina parts retailer. I enjoyed similar savings when I replaced my standing rigging, as described in Standing rigging replacement.

New winch cable properly installed and wrapped on the drum

For more information about maintaining a swing keel lifting system and how to avoid some common blunders, complete with pictures of some epic fails, see Five swing keel maintenance blunders and how to prevent them.

The proof is in the putting

Into the water, that is. I wish I had a big gantry crane in my boat garage (barn). Then I could hoist Summer Dance up off her trailer and test the keel for fit and free movement during lowering. Since I didn’t have one, I towed her to a local lake for a quick test. The keel lowered completely on the first try but I could hear it rubbing a little inside the trunk. Back on the trailer, I confirmed that only some of the bottom paint was rubbed off between the spacers and the trunk. That was good news and meant that we could take her out for a pre-planned extended cruise a week later.

Well into our cruise while waiting for wind on a doldrum day, I put on a dive mask and snorkel and went down for a closer look. Pushing as hard as I could on the end of the keel underwater, it had zero play or wobble yet I could rock the boat above. Mission accomplished.

Materials list

Following is a list of the materials and quantities that I used for the methods described in this series.

The Bottom Line

This project was less stingy than it could have been, in retrospect. I could have done without the Swing Keel Refinishing DVD. It helped but it wasn’t critical to the project. Much of the same info is available in Internet forums and blogs nowadays. I also could have skipped the sanding glaze, which was included in the process described in the DVD but was not necessary. Theoretically, I could have used regular body filler instead of the more expensive fiberglass reinforced body filler. And as explained in The error in a popular DIY DVD that will slow down your C-22, fairing to a 13% or less foil shape instead of the 16.5% foil produced by the template probably would have saved a gallon or more of body filler.

Together, those items cost about $192. Decide for yourself whether they are worth the additional cost. Still, doing this project myself saved me about 74% opposed to paying someone to do it, even with the unnecessary costs.

This project definitely took longer to complete than I expected, but since I did it during winter, I had the time available anyway and I wasn’t tempted to hurry or cut corners to get the boat back on the water. I should have also kept track of the hours I invested in this project but it would probably scare you away from refinishing your own swing keel!

You can do this project too. Nothing about it took exceptional skills or tools, just good old-fashioned hard work and attention to details. Considering its non-critical nature and the price to have it done by a boatyard compared to the value of the average trailerable sailboat, if you’re not going to do it yourself, you might as well not do it at all and put the savings to better use elsewhere.

Suggested price: $2,000
$tingy Sailor cost: $529.08
Saving: $1,470.92

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45 Comments Add yours

  1. capnrehab says:

    Thanks for the full supplies list. Nice to have it all in one place.

    Wow, just had a weird optical illusion throw me off for a bit. In pictures #2 & #3, when I first looked at them (an for several minutes of close inspection) it looked like the molded space for the keel hanger inserts was actually a white bracket that poked below the bottom of the hull. Very hard to break my eyes out of that image and into seeing a molded hole.

    Actually, every time I go back to the picture, it looks like it’s poking out again. Very strange.

    Thanks for such a great series. I found a welder who’s going to fix my keel in a couple of weeks. Finally found him through craigslist. I’ll keep you posted.

    1. Hehe, they do that to me too and those are the pictures with the least illusion to them. The ones I took that look straight at it are really wacky.

      Did you see this thread at CatalinaOwners of an owner who epoxied his sleeve in. The best description and pictures I’ve seen of that method. Still not sure I’d trust it over the long term, though.

      1. capnrehab says:

        I just don’t hang out there as much as I should. I sure appreciate when you think to send me a link. I hadn’t seen it, but I do have good news. A welder came by today to talk about the job. He’s going to fix the keel in 2 weeks in my driveway. After that, quick trip to the sandblaster and then I can get started. Of course that means I’ll be $250 for the keel, $250 for the welding, & $100 (est) for the sandblasting just to get to the point where you started your refinish. Good thing this was free boat!

      2. Well, you’re not missing a lot but there are a few guys there doing some really nice work.

        You do have a pretty enviable cost basis you’re working from with your boat. I’m looking forward to seeing your keel work and you get her in the water. Get some good pics of the welding process. Those will be pretty rare. Most of time, the owner misses out on it. Then you’ll have a pretty unique blog post to your credit.

      3. capnrehab says:

        Thanks for the tip. I’ll try to get both movie and pictures. Very excited about finally making some progress. Will be so busy this summer not sure how much progress there will actually be!

  2. Luke says:

    When you lifted your hangers into place did you put any adhesive or sealant on the backs? When I had initially taken my keel down the bottom and bolt heads were coated with a layer of 4200 and bottom painted oner, plus the there was sealant on the backsides as well. Do you even need bottom paint on the exposed bronze? I was also wondering that about the mushroom head of my thru-hull for the cockpit drains.

    1. I didn’t use any other sealant than Loctite on the threads. I don’t believe anything short of 5200 or epoxy is going to strengthen the assembly considerably and anything over the hangers or bolt heads is just going to make them harder to maintain.

  3. AaronD says:

    A question for you (since some keel work is in my future too…):

    When you replaced the winch and cable, did you consider or investigate using dyneema (Amsteel or similar) in place of stainless? I’ve seen a couple forum posts about making that switch on other swing-keel boats, but haven’t done any research myself, or seen much follow-up on the +’s or -‘s over time.

    Things I can think of offhand:

    –Stronger than stainless (Amsteel by maybe 20% – 3/16″ is rated 5400 lbs vs ~4000 lbs for 316 stainless; 5mm Dynex Dux is about 10k lbs, but more expensive)
    –No crevice corrosion
    –Coils smoothly on a winch, without kinking
    –Easy to splice (with a long bury)
    –Cheap (at about $1/foot for Amsteel, you could replace it every year for a few dollars)
    –Might not be quite so prone to hum at speed?

    –The long bury splice might be too thick to run smoothly around the turning ball
    –Possible chafe on the turning ball? (although replacing it every year should deal with that)
    –If in salt water, might salt crystals migrate into the cable and compromise its strength?
    –Probably others I’m not thinking of?

    And one more con that only applies to me personally – some previous owner left a brand new keel cable in the boat (at least a couple owners ago – I’m pretty sure the immediate previous owner didn’t even know what it was, so I’m a half-step up on him there…). So I’ll probably wind up just using the one I have, but I’m still curious about the possibility of synthetics, maybe for the next time around.

    1. Thanks for your question, Aaron.

      I hadn’t thought of that but it’s an interesting option. In my opinion, the pros are minimal and the rate of chafing would be too high compared to SS. Considering my new SS cable with roller-swaged fork cost me less than $20 from my rigger, there wouldn’t be enough benefit. I will be seriously considering rope for my lifelines, however, when it comes time to replace them.

      Good luck with your keel work. Let us know if you run into anything unusual.

  4. James McPherson says:

    Although I did not follow your blog to the letter because my keel was in pretty good shape. I short cut some of the steps. However I found your blog invaluable for the information, discussion, methodology,pictures, material recommendations, and links.
    Thank you for your help.

    1. I’m really glad that you found the information here helpful, James. That’s why I do this. For other readers who come across these comments, if you want to see James’s project, see the Need help with refinishing deck plan thread at

  5. capnrehab says:

    Hey $tingy, can I get a copy that foil shape template? I should be ready for it soon.

    1. I see that you haven’t subscribed as a follower. All subscribers received a link to the template in the last newsletter I sent out on the 1st. Is there a reason you don’t want to subscribe? You’re missing out on extras that don’t go into the blog posts.

  6. capnrehab says:

    FYI: Looks like the links to the materials list isn’t working. I tried the first 4. Just goes to $tingy Sailor oops page.

    1. Sorry about that. WordPress and Amazon links don’t play well together. I fixed them (again) and they were working when I tested them all a minute ago.

  7. mark says:

    I will probably do some subset of this project this winter. My first approach to building up the shape would be to lay fiber glass, matte then Woven Roving then matte as opposed to building up with 3 gallons of filler. Just curious if you considered that route and what you thought process was. Thanks for posting…

    1. That’s a good question, Mark.

      I didn’t consider that, but I suppose it could work and avoid using so much filler. The trick would be cutting pieces of matte and roving to the right shape to fit in the low spots and building those up to the level of the high spots first, similar to what I did with the filler in the time lapse photo sequence. It would also take longer to cure before you could use tools on the result, but if you have the time, go for it. Take pictures and let us know how it works out!

  8. mark says:

    In terms of time; laying up Fiberglas goes very quickly in my experience, I like to lay the next layer just as the previous sets up so you get a chemical as well as a surface bond – I have a major grinder that when fit with 24 or 36 grit, I call the “hand of god”. It makes quick work of shaping as long as you don’t slip. If there is a major downside going this route its getting the glass dust out of your exposed skin.

    So my next question is why do you think they just put a small patch up top to stabilize the keel up top. Seems like building up the top part across the entire keel, since I’m laying glass anyway, short of the locking pin (good point THANKS!!!) would provide a more spread out load which would be better in general. I imagine you want the locking pin to hit cast iron…

    In terms of the template, just to be clear, your template itself is not 13% since it is applied 90 degrees to the keel but results in a 13% shape at a 30 degree cross-section of the keel yes? I read all the articles but was not quite sure exactly what the template represents.

    Thanks so much for helping me noodle through this ugly job…



    1. The keel centering spacers are an after-thought, a concession to minimize the adverse affects of worn out keel holes, pivot pins, and hangers. They make the lock bolt more effective, prevent the head of the keel from scraping the inside of the trunk, improve pointing ability, and eliminate the thunk sound when switching tacks. But they’re unnecessary if the keel pivot assembly is properly installed and maintained. All the keel stability was designed into and should be done by the pin, hangers, and hull thickness around the weldments. If there’s no play in those parts, the centering spacers don’t have to do anything. For example, the paint is barely worn off of my centering spacers and that’s because I made them a zero-clearance fit when the keel is fully lowered.

      You could achieve the same thing by simply building up the head of the keel to the same thickness, but it wouldn’t be easy to get a really good fit (the trunk tapers from top to bottom) and it shouldn’t be necessary as I said above. And yes, the lock bolt should rub on iron, not plastic.

      You understand the foil template correctly. It’s not 13% itself but when used perpendicular across the keel results in 13% at 30 degrees. The actual water line stretches the 15% shape to 13%.

      Thanks for your questions

      1. Mark says:

        Sorry I used the wrong terminology, I wasn’t talking as much about the spacers on the keelpin as the spacers at the top of the keel that get epoxied on each side of the Keel. Wondered if having larger surface area would be better or if there’s a reason they are that size only. Thanks for your patience and answering all these questions

      2. That’s what I thought you meant. I wasn’t talking about the pivot pin shim washers at all. They shouldn’t be necessary either unless there’s any side-to-side play of the keel between the hangers.

        Regarding the centering spacers epoxied to the sides of head of the keel, more surface area wouldn’t hurt but by the time you exclude the path of the lock bolt, more area probably wouldn’t help much either. They’re just backup, really, to compensate for wear in the pivot assembly. You don’t want too much force pressing against the sides of the trunk. The fiberglass isn’t real thick there.

  9. Ken Elwood says:

    The best documentation of keel repair I have seen. Your whole site is exceptionally detailed and appreciated. I am a car nut with a small car site, and only just getting introduced to boat restoration and also plan to share my journey on the web.
    I have recently acquired a 1976 C-22 and know I need to address a keel in bad shape. My question is why not wrap the whole keel in fiberglass fabric and resin and then smooth with filler? I have not seen anyone suggest this. Is there a reason you only put fiber on the leading edge and not the whole keel?

    1. Hi, Ken

      Welcome to the world of C-22 ownership and the $tingy Sailor nation!

      Wrapping the whole keel with fabric or matte wouldn’t gain you anything. The keel doesn’t need any more strength and additional material underneath the fairing would just build up too much thickness in the high spots and it wouldn’t fill in the low spots. It doesn’t give you enough control over the thickness. All you’re after with the epoxy is waterproofing the iron. If it were lead, there would be no need at all.

      I added fabric along the leading edge just to protect it from accidental grounding. There are a lot of rocks along the shores where I sail and water levels fluctuate. The particular iron that these keels are made of rusts extremely fast (within hours), so you want to avoid penetrations through the waterproof barrier as much as possible.

      Thanks for your question and best of luck fixing up your C-22. That’s a sweet looking Porsche. Nice work!

      1. Ken Elwood says:

        I see that you have the brass pin brackets that are wider to reduce movement from side to side. My brackets are not the retrofit, and thus not as wide, but in good shape. $131 seems heavy to retrofit them. It seems to me that I could buildup each side on the keel with 6+/- inch circular sheet of fiberglass around the pin,(like a giant washer epoxied on) just as you did for the shim above and would be able to achieve the same result, if not better then the new brass bracket. Do you have an opinion on that topic?

      2. Hi, Ken

        That would work fine if you’re going to refinish the keel anyway. Measure the distance between the hangers with them in place, then fair the head of the keel to that thickness. Three inches in diameter would be plenty but more doesn’t hurt, either. Also consider fairing a centering bulge in the very upper end of the keel like the spacers I bonded on. Take that measurement carefully because the keel trunk tapers from top to bottom and your keel pivot pin might not be perfectly perpendicular in both axes.

        Thanks for your question and best of luck with your project!

  10. Ed says:

    I love the great posts on your blog with all the detail of your though process and visualizations to make descriptions extra clear.

    I am rebuilding (not just refinishing)the keel for my Venture 21. It is what I call a composite of a steel bar core, a lead bulb and a whole bunch of filler wrapped in a fiberglass shell. I think they must have actually prepared the shell in two hales and poured in the filler over the core, but can find documentation to verify that.

    My question is about the ablative bottom paint (and this may be a newbi question…) Do you think it is necessary on a boat that will spend most of its time on the trailer and won’t be in the water for more than a few days during each excursion?

    I also wondered about rust prevention on the cast iron keel between sand blasting and the first coating. Did the shop coat it with a Phospho like material to convert any iron oxide to a solid seal layer before application of subsequent materials?

    Thanks for the informative blog! Please keep up the great work!

    1. Good question, Ed

      Dry sailed boats that spend the majority of their time on a trailer don’t need ablative bottom paint, in my opinion. My C-22 only has it because the previous owner kept the boat in salt water most of the year and it wouldn’t be worth it to refinish it to bare fiberglass. It’s a lot less work and expense to just clean your bottom well after each time you sail.

      When I had my keel sandblasted, the shop didn’t apply anything. I had them call me in time to pick up the keel as soon as it was done and I took it straight into my shop where I immediately put on a sealer coat of unthinned epoxy. I still had to remove a little bit of rust that had already formed in the time between their shop and mine. If you can’t work it out to seal your keel right away, do talk to the shop about sealing it immediately. Be sure they use something that is a compatible undercoat to whatever you plan to apply over it to complete the refinishing.

  11. Andrew Meehan says:

    I am currently in the process of refinishing my keel. I am considering using epoxy to secure a plate of aluminium along the path of the lock bolt. This way if I forget to unlock the bolt when I raise the keel I don’t scratch down to the iron. The plate will be electrically isolated from the keel so it shouldn’t become a ‘zinc’, but even if it did, better it than the keel. I will be adding the spacers (that are thicker than the plate) to the top of the keel at the same time so the aluminium should never contact the hull. Anything else I should consider?

    1. That’s a good idea, Andrew. Just remember that the aluminum will have a much lower coefficient of friction than the keel surface so you should really crank the lock bolt down to provide the same amount of braking force.

      And in case you didn’t know, if you sail in fresh water, aluminum is the preferred material for anodes instead of zinc (for salt water). So if your plate does make electrical contact with the keel, it could decay relatively rapidly depending on your water conditions. While you’re refinishing the keel is a good time to install an anode somewhere as added insurance for your fresh keel.

      In my opinion, attaching an anode to an iron keel is self-defeating because it’s almost impossible to permanently seal the anode watertight while allowing electrical conduction. You can see the resulting damage to my keel in this picture from Part 2 of this series. The tapped hole for the anode mounting screw is to the right of the yellow strap and was extensively eaten away.

      Large cavity uncovered during grinding. Note the zinc anode screw hole to the right of the strap.

      Consequently, I’m a proponent of remote anode installations.

      1. Andrew Meehan says:

        I am considering a remote anode, alternatively I thought I might install a SS stud (drill and tap) in the keel with a deep(ish) countersink I would fill with epoxy. I think this would remaining waterproof and would allow sink changes without breaking that seal. The only downside is that replacing the stud if it was damaged would be a nightmare. I sail in a inland lake so I was considering using a magnesium anode. This would protect the aluminium also.

        I am curious where you found the coefficient of friction. I used the table you referenced in you lock bolt analysis and came to the conclusion that aluminium and steel would have a higher coefficient (0.61 vs 0.4).

        Also, and maybe this comment should be on the other page, why didn’t you include the spacer to keel trunk friction in that analysis? Unless the keel pin is a super tight fit (mine isn’t) the keel trunk will have to provide nearly all the opposing pressure imposed by the locking bolt (the trunk is basically a giant C clamp). Granted I couldn’t quickly find a coefficient for this, but if I were to epoxy an aluminium plate on the keel spacer and inside the keel trunk (opposite side of the bolt) I would get a coefficient greater than 1 on that side! I am an engineer so I will probably get no rest until I do this analysis now that I have thought about it more….

      2. On paper, a SS stud in the keel looks good but I wouldn’t bet much on it staying waterproof over time. The anode on my keel was attached similarly, with a SS nut epoxied into a shallow hole in the keel. The anode was attached by a SS bolt into that nut. It pulled out easily by hand and the hole was badly rusted. Your idea of drilling and tapping the keel won’t be easy if you choose that route. The iron is very hard to drill and tap. Ask anybody who has replaced a keel winch cable eye bolt because it too rusted out. It can require a machine shop to get it right.

        In lab conditions, you’re right. More friction would develop between the lock bolt and a smooth, clean aluminum plate than with smooth, clean cast iron. But in the real world, most cast iron keels are very rough and have one or more surface films (ablative paint, filler, barrier coat) that I’d guess cut the coefficient of friction approximately in half (see the small table at the top of the Engineer’s Handbook page, for example). Put the keel in water (lubricant) and friction goes down even more. To be an effective brake, you want as much friction between the bolt and the keel as you can get. In my opinion, that’s worth possibly scratching or gouging the keel finish, which is easier to fix than the boat turning turtle or the keel slamming into the keel trunk.

        I didn’t include the friction added by keel spacers because the majority of keels don’t have the spacers. The amount of friction would depend on too many variables: the size of the spacers, % contact area, surface paint on the spacers, and so on. The inside of the trunk (bearing surface) is polished fiberglass, possibly has surface paint, and is of variable thickness and stiffness. In the end, even if you could calculate it, I believe that the amount of friction would be too low to be significant.

        All this analysis can be interesting, but I recommend avoiding the temptation to overthink solutions on a sailboat. Make it good enough to sail safely then go out and do it, I say 🙂

  12. Andrew Meehan says:

    Interesting, my idea was based on the eyebolt. Mine seems to be in great shape, I sure hope it isn’t rusting out! I have only ever tapped steel and stainless, and i know how much I hate taping stainless so that might be enough to stop me from going that route.

    I agree that the true friction from the keel trunk is probably pretty low for gelcoat to ablative paint in most application. I also acknowledge that when the bolt is simply hand tight the keel isn’t pressed up against the trunk on the other side, the weight of the keel hanging down is enough. Since it isn’t camped tight the side forces of the water when sailing can make the keel swing back and forth between hitting the side of the trunk and the bolt, thus the clunking when tacking. However, if you are placing 1650 lb of clamping force on the keel something has to resist it on the opposite side, spacer or not, and I don’t think that friction can be completely ignored. Even a coefficient of 0.1 would get you 25% more locking force.

    I will probably place the the plate simply because my main concern is protecting the keel. Given the aluminum has a higher friction coefficient than iron it will be at least least as good as iron, filler and paint to slow the keel from slamming the trunk.

    The plates on the opposite side is pretty much just fun to think about; I am not that worried about a knock down on the lake. Adding it to the analysis was actually pretty easy and using a u = 1 for the plates yielded a torque of about 4ft lb. Obviously this is a super ideal case but I think it can be shown that with a pretty reasonable modification (assuming you are already doing keel work) much better locking force is possible. Put some cross hatching into the plate and you could probably get some pretty effective locking. I am sure even better materials are out there.

    Winter is long in PA and I wont be able to sail for a while, so if I get really board I might get some scrap aluminum and do some real world friction tests. Unfortunately over thinking it isn’t possible for me, but I never let that stop me from sailing!

    Love your blog by the way!

    1. You’re on the right track, Andrew. Like other vehicles, sailboats are excellent classrooms and labs for the engineering minded. Almost everything about them involves motion, forces, and material properties. That they come together and give us joy boggles the mind.

      What’s your engineering background?

      1. Andrew Meehan says:

        I have a masters in electrical engineer and do embedded system design (circuit, PCB and firmware).

        I am currently putting fiberglass on the leading edge of my keel; how has that held up for you?

      2. Hi, Andrew

        It’s held up really well and I put it to good use once this past season. The slips in our marina have steel angle iron braces across the end of each slip underwater about 6 feet. During summer, they’re below the draft of my sailboat and I can leave my swing keel down when I pull into my slip. But the lake level is lower in spring and fall. One time this past spring, I forgot to raise the keel when I pulled in and the forward edge of the keel struck the underwater brace. The boat was moving slowly so there wasn’t any danger and it just stopped abruptly. I expected to find a noticeable ding in the leading edge when I pulled the boat out for the winter but I couldn’t even tell where it hit.

        Granted, it wouldn’t have caused much damage without the extra fiberglass either but it was a good feeling to know that whatever damage occurred, it wasn’t going to penetrate all the way to the iron, which would have been the case with just paint.

  13. Ed says:

    Back again with another question..two years after my earlier comments and my V21 keel is still not rebuilt!:-( Do you know what sort of backing plate system was used on the hull when Catalina constructed of the keel hanger system? Is it apparent when looking inside the cabin at the keel trunk area?

    The only metal components I see on my V21 are washers on the bolt that get sealed in place (and a bronze, I think, ferrule that is positioned in the keel where the bolt passes through). That ferrule was the significant wear point which allowed water to seep into the steel bar core of the keel’s upper section. I would like to devise a more secure mounting system, less prone to wear and eventual play. I suppose one could quickly over-engineer it and go beyond the economical solution…

    Thanks for reposting this series…and maybe remotivating me to dive back in!


    1. Hi, Ed

      The best pictures that I have of the keel hanger attachments are in the last installment of this series, Refinish Your Swing Keel for Best Performance – Part 5: Installing. There you can see the exposed ends of the weldments that are embedded in the thick, surrounding fiberglass.

      They look like this:
      C-22 k
eel hanger weldment

      The C-22 keels use a brass pivot pin through the cast iron keel. If the keel hole gets enlarged from wear, there is a stainless steel sleeve available for welding in place to restore the correct diameter.

      Hope that helps!

  14. JAMES NAIL says:

    Excellent post! I just refinished my keel using your posts as a blueprint. It has turned out great! Thank you so much. I have a question concerning the h pro fairing used. I used that and it worked well on the keel as you did. Id like your opinion about using that same product around the boat itself, ie hull, cabin top, interior. Do you think itd be to rigid for repairs to the rest of the boat? Thanks in advance.

    1. Hi, James

      It should work okay for small, thin areas but like all fillers on fiberglass panels, shouldn’t be applied too thick or over too large of an area.

      Thanks for your question,

  15. Matthew says:

    What is a remote anode?

    1. Here is more information about the whole subject than you’ll ever care to understand, much less read, but see the diagram showing internal bonding near the end of the page.
      Galvanic Corrosion

  16. Matthew Silva says:

    Would one of those zinc fish be considered a remote anode? What do you use?

    1. Yes, it would be better than nothing, although it’s not very convenient and easy to forget. My sailboat is always in fresh water, my keel is sealed very well, the zincs on my outboard motor haven’t deteriorated noticeably in 7 years, and I haul it out over the winter, so I don’t have a zinc on my keel.

  17. David Douglas says:

    Thanks for creating and maintaining this awesome website Stingy. I’ve already learned a lot about sailing and particularly the Catalina 22. I’ve already done a few of the simpler things like the boom out haul and down haul. Since I keep mine in a slip full time down here in corpus christi, I went ahead and pulled the keel and was horrified by what I saw. Then after sandblasting I had so little meat left above the keel pin that I had to do something. I saw cloud driver’s post on epoxying the bushing in and while it looked beautiful I too was somewhat skeptical about that approach since I’m in saltwater full time. I messaged him with pics and he agreed that I was missing too much. I ended finding a welder that filled the whole area in with brass. It looks really good. No bushing. He said when the hole wears out down the road he’ll put the bushing in. So now I’m copying your method to refinish it. I just finished the second epoxy coat and will start the pro-glass filling process in a few days.
    Thank you for all the help and advice. David

    1. David,
      I’m sorry to hear that your keel pin hole was so far gone. But that’s pretty typical of a lot of C22s so don’t feel bad. I’m glad you found a welder who knew what to do. That’s not typical. The rest of the job is relatively easy compared to what you’ve done so far. I wish you continued success on getting it back in the water. Send me some pics of your finished work and I may put one in the Readers’ Gallery to inspire others.

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