Thoughts on replacing keel bolts

[donncha]

Replacing the keel bolts on a 30ft, 7 tonne Falmouth pilot


The keel bolts will have to be replaced sometime soon, they are extremely rusty and in a few cases the nuts have disintegrated in my hands.The keelbolts go from the underneath of the keel up through the floors and the nut is inboard.

The boat usually lifts out onto a static cradle. No trailer. The ground is solid granite, so that rules out digging a few holes. I was thinking that it might be possible to place wooden blocks under the keel in such a way that a few of the keelbolts would be visible. i.e. there would be a gap of about 1 foot between the keel and the ground, where it might be possible to drop the bolts out. Now the bolts are about 3 foot in length, it wouldn't really be that safe to leave the boat up that high for the entire winter so therefore it would be possible to use the 1 foot gap to cut the bolts as they come down.

The big question I have then is how to put in the new bolts. As things stand, the nuts are inboard as they are in most boats I suspect. If the bolts were put in from the inboard side and then good locknuts were used on the underside, would this be adequet? Or would it be advisable to use studding and weld a "head" onto the studding from underneath after putting it through from the inboard side?

Are there any other alternatives methods to replaceing the bolts that I have overlooked?

Ruling out lifting in a crane for the job, as I reckon it's going to take a good deal of time to remove the old ones.

 

[KenMcCulloch]

Port Edgar, where I keep my boat, has many deficiences but among its best points is the use of a very good hydraulic trolley system for moving boats about. The boat sits in its cradle on 3 or 4 sleeper-sized timbers. These sit on the trolley for moving and then on some blocks to allow the trolley to be lowered and slid out. This gives about 50-60cm clearance between the bottom of the keel and the ground. Even on a Folkboat with keelbolts the longest of which is a bit under a metre they can only be removed by knocking downwards and cutting them off piecemeal as it were. Removing old keelbolts can be quite time consuming and you need to be prepared to make other repairs as for example floors may be damaged in the process.

If you could have your cradle chocked up in this way it might make your job easier.

A friend who is replacing keelbolts on a restoration of a Folkboat has had new bolts made up in the appropriate lengths from steel rod, threaded at both ends. The bolts will be inserted from inside the boat, nuts fitted outside, probably with strong thread sealant, then tightened inside the boat.

 

[Tranona]

It depends on whether you want to split the keel/hull joint or just replace the bolts. If the former then you can't avoid a crane or some system of jacking it up off the keel. When I did it I had the keel moved sideways and the boat lowered to a safer heght while I worked on it and then lifted back on later.

With regard to the bolts themselves, bar threaded at either end. You need to be sure that the pockets in the bottom of the keel will take the nuts. You have a choice of materials. Mild steel is common - either galvanised or set in pitch, but you can also use 316 stainless if you are happy that no water will get into the joint. This can lead to corrosion where the bolt goes into the ballast keel. I used 316 when I did the job about 18 years ago and filled the holes with sealer. Seems to be OK so far!

 

[johnlilley]

Replaced nearly all the bolts on a 6 Ton Falmouth Pilot many years ago from the inside of the vessel. made new bolts from plain mild steel and machined on the lathe a carrot head nut to fit In the recess in underside of the keel. It is likely the 9 Ton Pilot also requires carrot head nuts fitted.
The new bolt has to be slightly longer in order to allow the bolt to protrude underneath so the shaped nut can be screwed on and then pulled into position from the inside of the Vessel.
Make sure the carrot head end of the bolt is threaded for only the length of the nut and that the inner end of the bolt is reduced in diameter at the extreme end to allow for any damage caused by hammering into position.
Use plenty of lubricant whilst drifting the bolt in from the inside, wind a few spirals of cotton caulking on the outer nut before locking up from the inside.

These bolts were rechecked approximately 12 years later following survey and a new purchaser and they were nearly as good as the day and they were fitted. If you are able to do a search on Classic Boat magazine, I wrote an article on exactly this procedure many years ago. It is entirely feasible to carry out this procedure if the vessel is on blocks ashore.

John Lilley

 

[SHUG]

Don't replace all the bolts at once!!
If there a six then do three this year when hanging from the crane or blocked up and three next year. That way you will not disturb the hull-keel joint.....(much)

 

[Jwoods]

Us Falmouth pilot owners must stick together! I replaced 3 bolts on my 6 tonner last winter. I had never done this before and did not know what to expect. My boat sits on a cradle and I designed it so that I could remove the keel slats one at a time. So it was the issue of just getting them out. I used a Glasgow spanner (angle grinder) to cut through the nut and then 10 feet of bar on the socket drive. The sledge hammer finished the job. We had to use car headlights to see what we were doing and a drift helped extract the bolt.

The bolts are 7/8th whitworth and I got a local blacksmith to "upset" the ends. A friend helped thread the tops as it would not have been possible with my lathe unless I screw cut the threads. I also replaced all the nuts I could find with the proper thread. The bolt heads were recessed so I used car body filler instead of putty to fill in the recess. Nothing has leaked yet. although my friends do call the boat "its-still-afloat".

As It happened I did not have to replace all of them, but moving the engine (Volvo 2002)to get at the one under it, was a pain and them I had to rewire everything too!

I suspect that the same size bolts were used in the larger boats. I do not know if this will help, but best of luck.

 

[cliffordpope]

I did this job on my boat early in the restoration. The 100-year old bolts were rusted solid into the iron keel and the oak floors, but wasted away to virtually nothing at the join.
Nothing would drift out - the bolts simply compressed and locked in even tighter. I hacksawed through the remains and removed the iron keel, then drilled out all the bolts.
Each floor had to be removed, by hacksawing through each fastening, then hacked open to get the bit of keel bolt out. Some split and were replaced, others were reasonably sound.
The old oak was pickled rock-hard.

Then I had 6 new bolts made from wrought iron, said to be "marine grade" from a precious store of old iron.

It took about 3 years of painfully slow progress, the most wretched part being lying in the bottom of the boat hacksawing old fastenings one by one.

Good luck!

 

[donncha]

Thanks very much for th replies, such an amount of information. The intention is simply to replace a few keel bolts maybe 3 or 4 at a time, no need to separate the keel from the floors I hope. It will be a simple solution then next year to make some space under the boat using wooden blocks spaced out and cut away the old bolts.

Most likely replace with stainless but will have to cost this first. I am well aware that ss suffers from crevice corrosion and pitting in oxygen starved environment.

Thanks for all the help, especially from the falmouth pilot owners, I shall keep everybody posted.

 

[Sniper]

Just to reinforce your plan, I've been following a similar strategy over the last few years; a rolling programme of keel bolt replacement doing two each year. They've all come out without a problem and were worn enough to be replaced. I have two in the forward part of the keel which are stainless steel. I know the received wisdom is generally no s/s below the waterline but they've been out twice in the 15 years we've owned the boat and are displaying no signs of pitting or crevice corrosion.

Floor bolts on the other hand have given me a real head ache! Completely degraded in most cases and with the surrounding timber quite rotten. They've now all been replaced and the wood made good with stealers.