Technical Plan And Results for Keel Bolt Repair

Valiant 40 Hull #249

Symptoms Indicating the Need to Replace the Keel Bolts

Two of fifteen bolts had snapped off above the nut without any known source of damage or other explanation. When I started investigating further, one of the nuts broke apart, leaving a broken stub of a keel bolt exposed without a nut. Given the impact of stainless steel crevice corrosion, I became worried that bolts which may appear acceptable, may have a structural defects that exist beneath the bolt surface.

The bilge was dry (except at the very lowest point where water from rain down the mast or condensation from an air conditioning unit we use in marinas pools from time to time. There was no sea water intrusion through the keel/hull seam or around the bolts.

If you’d like to see more photos or read more detail CLICK HERE.

Planned Strategy

Melt out each keel bolt, individually, and replace all of the old keel bolts one at a time with a new bolt in the same diameter and “J” shape using Silicon Bronze 655 Alloy.

Q: How can you melt out the old bolts without impacting the shape of the keel?

Answer: (1) free the bolts through channels melted in a shape and depth as small as possible; (2) never take too many bolts out in any one place at the same time; (3) use a thermal temperature gun to monitor the material surrounding the channels to make sure the larger part of the keel never got close to the melting temperature for lead (which is only 327 C or 621 F).

Q: How do you make sure the new lead will adhere to the larger block of the keel left in place?

Answer: (1) Prevent or remove oxidation by chiseling away any oxidation on the surface of the intact keel and using the oxygen part of the oxy-acytalene torch to blow away oxidation that floats to the surface of the melt puddle. (2)Make sure the lead being melted back in contains approximately 5% antimony. And (3) melt new lead to the rest of the keel using the “puddle-to-puddle” technique.

Q: How do you make sure the new bolts will be in the same place/angle as the old bolts?

Answer: Build a jig that holds all the bolts in place both in relation to each other, and at the same vertical angle the old bolts were in.

If you want to read more about the strategies I considered and why I decided against them and for this strategy, read THIS and THIS

Safety Notes

Lead is a toxic metal and will create harmful fumes when melted. You should use carbon filters with N95 pre-filter on a Full Face Mask Respirator, wear protective clothing that you remove and leave/wash on the job site, and you should always wash your hands and face before smoking cigarettes, eating or drinking after touching, sanding, or melting lead. My wife says you should probably not wear flip-flops while doing this type of work, but I have to draw the line somewhere while making boat repairs in the tropics.

Actual Report

Dropping the Keel

Hauled out and removed the mast out of a concern that the boat could tip with the weight and high center of gravity that would occur once the keel was off. In the alternative, you could build a full cradle and keep the mast on.

To remove the nuts, I built a breaker bar from two long stainless steel bars, turned at a 90 degree angle with a socket wrench on the end. This worked to remove all but two keel bolt nuts. I used an angle grinder to cut the last two bolts just below the nut. *I knew I wanted to replace keel bolts already, so this method is not a great method if you hope to inspect and preserve your old keel bolts.

Once the hardware was off, we lifted the hull off the keel using a travel lift. It took a short amount of time allowing the keel to dangle unsupported just centimeters off the wood supports to have the old glue stretch and separate keel from the hull. The travel lift driver was very cautious not to lift the hull too high until the keel fully separated and gently laid on its supports. When the glue released, it released quickly. So, if they had lifted the hull higher off the ground, the keel would have likely crash landed.

Upon dropping the keel, we found 5 of 15 bolts were visibly damaged. A few weeks later, a sixth bolt that had previously looked all right snapped apart with no major force placed on it. This convinced me the full keel repair is necessary and a good idea.

If you want to see more pictures, read more detail CLICK HERE.

Melting out old keel bolts

Once the keel was off, I sanded off the bottom paint and filler the manufacturer used to fine tune the shape of the keel.

I practiced working with an oxy-acetylene torch and a lump of lead I made from melted down fishing lures until I felt comfortable that I had the finesse to do this without messing up the keel. The challenge is to get straight, clean channels to melt away from the larger block of lead. I determined that keeping the temperature of the surrounding lead down helps make a more clean channel.

During this phase, I also built a jig out of old angle iron and pipes. I placed a 3/4 inch diameter pipe over each of the keel bolts. The outer diameter of the pipe was small enough to fit through the holes in the hull, so as long as the new bolts fit into the pipe, there should be no reason they wouldn’t align with the old holes in the hull. Then, I had a welder at the yard connect each of those pipes to angle iron that runs from front to back of the keel. I then used the keel bolt nuts to secure the jig in place by screwing down the old nuts on any of the intact keel bolts. Originally, this jig was all one piece, but I found it awkward and cumbersome to take on and off as necessary, so I had it cut into three pieces that overlapped each other from front to back. That way, when the full jig was in place, there was no way for it to sit in any position other than the original angle and position of the old bolts.

Once ready, I began melting out a couple keel bolts at a time, separated from each other on the keel so that I did not reduce the structural integrity of any one area of the keel too much. I caught the old lead from the keel in a cake pan, with the intention to reuse it and only add the minimal amount of new lead when I melted the bolts back into place.

If you want to see pictures or read more detail about this practice READ THIS and THIS.

Preparing Lead Ingots & Melting In Keel Bolts – Take One

After catching the old lead, I re-melted it in a soup pan, placed the cake pan at an angle, then poured easy to handle lead ingots into the corner of a cake pan, let cool and solidify. At one point, I needed to supplement my old keel lead (having lost some material in the process) for that, I melted lead diving weights I felt confident were made of 95% lead, 5% antimony.

I attempted to install a new bolt and melt lead to surround it while the keel was still in the vertical position, but I could never build a sufficient enough “dam” to keep the molten lead in place on the vertical keel until it cooled. This necessitated a procedure in which I lowered the keel onto its side while installing new bolts, then lifted the keel vertically again when I wanted to melt out an old bolt. Using a strong fork lift, we put two lifting straps on front and back of the keel. We lift the keel vertically first, then the forklift driver drove backwards to slowly tip the keel onto its side without dropping it suddenly or misshaping it. You may wish to prop it onto a wooden palate. Use wood blocks and car jacks to adjust the particular channel you are trying to work with to be level.

Preparing Lead Ingots & Melting In Keel Bolts – Take Two

Once I had the fork lift system down, inserting new keel bolts became much easier.

Install the Bolt into the Jig: I would slip the keel bolt in through the hole in the jig and securing it by tightening down the nut. The bolt should be resting on a bed of old lead (as the keel is tipped on its side, and you melted only enough of a channel to be able to remove the old bolt).

Create an effective dam or barrier to keep the molten lead from running out the side: I used a thin, stainless steel or other flat surface metal that can withstand the heat of the molten lead. I drilled a ¾ inch hole in the sheet metal to allow space for the bolt. Then, I tacked the sheet metal between the jig and the top of the keel, securing it by screwing the keel bolt nut down firmly.

Clean Oxidation: I would then chisel away a thin layer of lead all around the channel to remove as much oxidation as I could. The lead will adhere to itself better with no oxidation or impurities in the way.

Puddle to Puddle Melting: Using the oxy acytalene torch, I heated the sides of the channel to get a slight liquid melt on all lead surrounding the location of the new bolt. I then melt the lead ingot, making sure sides of the old lead and the new ingot are melting together so the lead is adhering “puddle to puddle” rather than cold lead to liquid lead. Black oxidation and impurities will float to the top of the lead puddle as you work. Use the oxygen blaster on the torch to push the oxidation layer and impurities into one area of the puddle where it will be easy to remove. After it cools, I chisel it off.

Try to melt in enough lead to fill the entire channel in one go. This will improve the adherence of lead to itself. However, monitor the surrounding keel lead to ensure it does not reach melting temperature. Using a temperature gun, I would pause and allow the keel to cool if the lead reached a temperature higher than 100 degrees Celsius.

If you want to see photos or read more detail about how the original dam didn’t work out, how the fork lift process went, and how easy it was to melt the bolts back in once the fork lift system was perfected CLICK HERE.

Note About the Front Most and Rear Most Bolts (…at least on Hull 249 Valiant 40)

On my keel, the front most bolt and the rear most bolt did not match the design blue prints. Those areas of the keel are not vertically deep enough to accommodate a normal “J” shaped bolt. According to the blueprints, I expected them to be a straight bolt, inserted into a smaller amount of lead. Instead, when I began melting them out, I discovered the manufacturer bent the bolts into an odd shape. That is not a “J” but fit inside the lead. It looked messy and undesirable. I attempted to melt a straight bolt into that area of lead, but it did not adhere and slipped out directly when I pulled on it from the top.

To resolve this problem, I had threads machined into the bottom of the straight bolts, I added an extra silicon bronze keel bolt nut onto the bottom of the bolt, and then melted the bolt/nut shape into a puddle of lead. This created adherence and the front/rear most bolts do not slip out when pulled vertically using this design. You could also bend them into a like-“J” shape that will fit in the area and that would give a similar result.

Reattaching the Keel

Once all the bolts are replaced, I used a flap disc on an angle grinder to sand the rough edges around the formerly melted channels to be smooth and clean like the original keel. With ideally three people, have one person sand off the outer most layer of lead/oxidization using 100 grit sand paper, the second person should follow directly behind wiping the dust off with acetone, then ideally, a third person can follow immediately behind to paint with an epoxy primer as quickly as possible over the entirety of the lead keel. This will provide some salt-water protection and a good base for filler and bottom paint to adhere.

Clean the top of the keel to make sure the bolts are all in good shape, use an air compressor to blow away water trapped anywhere that might sit inside the keel/hull joint.

Work with a very talented travel lift driver and team to position the sailboat directly above the keel.

Slowly lower the boat down, adjusting in small increments until the bolts all align and fit through the holes in the hull.

To seal from water intrusion, I used 7 Cans+ of 3M 5200, layer the 5200 onto the keel, spread from outside all the way through center of the keel, adding a substantial layer of 5200 around the bolts themselves and at the outermost edge.

I had drilled holes in new 1/4in Silicon Bronze Backing Plates to match the placement of all the new bolts. Inside the bilge I adhered these backing plates with layer of 5200.

Around the mast, Valiant has a stainless steel backing plate that was still in good condition on my boat. I had some concern about mixing metals having now silicon bronze keel bolts next to that stainless steel backing plate. So, I filled the holes around the bolts with 5200 to isolate the bolts from the stainless steel plate, and then I added custom shaped/drilled G10 Washers between the stainless steel backing plate and the silicon bronze nuts.

Finally, I installed the remaining silicon bronze washers and nuts, and torqued all of the nuts to 115 foot pounds per engineering specifications of this size/thread type silicon bronze bolts.

To see photos, videos, and read more detail about the reattachment phase, CLICK HERE and HERE

Total Cost

Estimated expected expense $10,000.

Actual cost: $6,500 plus 200 of my own labor hours.

This actual cost tally includes all three months of my yard time in Langkawi, Malaysia at [$400 / month].

Travel Lift Costs for (1) Haul out; (2) Mast Pull; (3) Lift Hull off Keel; (4) Lift Hull onto Keel; (5) Reinstallation of the Mast; (6) Re-splash.

Cost of 15 keel bolts, nuts, and backing plates manufactured, machined, and shipped from United States to Malaysia

Use of (8x) the fork lift, driver, and lifting team.

Purchase of Oxy Acetylene Torch, angle grinders, respirators, random tools etc., plus rental of oxygen and acetylene tanks.