Forming Lead Keel and Afixing it to the Boat

[Kristian]

Again on the subject of sharing..

I know that I´m exposing that my restoring project of a beautiful old boat might have gone a bit too far but I will anyhow open my mouth just to shed the last pice of possible doubth......

12 years ago I was in the process of studying keels and attachments methods and materials and learned that it is almost impossible to cast a big keel that is really fair and will fit your keel sole perfectly. This is mainly due to uneven shrinking as it colds.
This was very evident to my fin keel.

The interest was partly due one of my old collegues that had a a rather extreme racer produced that on the maiden voyage in really tough conditions on the Swedish Eastcoast lost the keel. It was unfortunately very cold water and my friend lost his daughter that did not make it until they were rescued.
The architect was of course responsible fitting a high aspect racing keel with a single row of keel bolts but other aspects interested me as well.

The normal procedure with mastic betwen keel and sole invites to a small movement in the construction wich in turn invites to acceleration loads on the bolts when beating in rough seas

It is easy to see that if you have a perfect fit the movement problem will be reduced as far as is possible and if you have the right amount of keelboalts with the correct preetension you will get no acceleration loads due keel movement.

I contacted one of the companies that are into keel manufacturing and learned that the only good way to approach the perfect fit wish was to saw the lead keel with a chainsaw. They said you can not saw lead in any other way since it will just clog.

The problem was now just to get a chainsaw and make some guides so it could be used for precision sawing.
Making the guides fitting for normal L shaped steel that was easily screwed into the keel was really very easy. A rather uneventfull 3 meter run with the chainsaw and there was a perfectly straight plane surface of lead.
I lost 1,5 cm of lead but belived that that was OK.

I was at that time studying a West Epoxy instruction book on boatbuilding and also SP´s technical manual on Epoxy properties.

Due to my wish to achive the absolutely best keel attachment that is possible I contacted West Epoxy´s technical director to discuss weather or not to use Epoxy with high strength additive instead of the usual mastic between lead and fiberglass.

He said it is no better way to attach the keel but you have one downside and that is you will never get that keel of the boat if so needed.

I did of course go just that way and I conforted myself in that I hope to find one way to get the keel of the boat if ever needed without breaking anything.

The procedure is just like if you are using mastic with the only difference that I used a single layer of Mat and slow hardening epoxy with a thickener giving the highest bonding properties.

While thinking about all that now rather a long time ago when I yesterday was writing about Microwaves and drying a wet deck core an Idea struck me. This type of epoxys heat deflection temperature ( when it starts to go soft) is only 80 degres celsius. Putting the Boats lower parts in a really hot bath for a few hours before lifting her out and removing the keel could probably do the trick.

Do I need to say I used 10 (25mm) highly polished keel bolts that was screwed down with a compressed air wrench for lorries.

I do never worry about my keel ever poluting the seabed unattached form the reat of the boat.

Rgds

Kristian

[Geminidawn]

Originally Posted by Kristian

The normal procedure with mastic betwen keel and sole invites to a small movement in the construction

This reason why a flexible bedding compound is used, it is meant to flex a little and not meant to be permanent. There will always be movement, be it solid or not the lack of flexation will lead to something cracking even if those cracks are minute and it will eventually lead to water ingression. Keel bolt inspections and replacement is a standard practice and something to be expected once or twice in a yachts lifespan and I have done my fare share of them. The trick is to use a flexible bedding compound with no adhesive properties.
We once got a boat in where the owner was complaining about leaky keel bolts. We took it out of the water and the Surveyor ordered a full replacement. The lads jacked the boat up and removed the old bolts, however some genius on the previous keel bolt replacement bedded the keel with a flexible adhesive, the lads tried to coax the keel out with little sucess, the keel hung on the adhesive alone for two days and when it eventually came away it took half the laminate with it. Such a repair bill could of been avoided if the proper materials were used in the first place.

[Kristian]

Hi Geminidawn!

Thank you for your reply!
You are correct in your statement about everything beeing more or less flexibel.
If I understand your point correctly You want flexible mastics to actually add to that flexibility and if it is thick and flexible enough it will keep the boat watertight.

Let me explain my way of looking at these things by describing other things we might be more familiar with.

If you place your head against a wall and ask a friend to apply lets say 10 kg of force on you forehead you will feel that force on your forehead and neck.
If you do exactly the same thing but start with the head 1 cm from the wall you will feel a much bigger force to start with and then the same as before with your head against the wall.
The point is that you experiance acceleration forces, thay are much greater than the forces you are dealing with originally.
If you go this way your keelboalts must be much bigger to handle the added stress.
You say that keelbolt replacement is more or less part of the regular maint. I do strongly dissagree.
Using correct size for the comming loads ,the correct pre tension of the boalts and last but not least a shape and materials that do not give will give you keelbolts that will outlast the useful servicelife of the hull.

I do agree that keelbolt inspection is warranted due to way to many yachts with incorrectly pretentioned bolts and less than perfectly fitted keels.

It is perhaps even easier to understand if you look at the head of a diesel engine.
Your statement sure is true about everything flexing and due this the gasket ( the part sealing the compression/ explosion) is made from metall and not something nice and flexible. The pretentioning is precisely described in your workshop manual.

An other thing where exactly the same principles are adopted is your rigging.
No matter if you use wire or rod you get flexing.
This is actually the reason why correctly tuning ( In this post I only adress the pretentioning not the other aspects of rigg tuning )of the rigg is essential.
If not tuning ( pretensioning) the wire or rod correctly they will fail early.
The thing that might feel a litttle strange to grasp is that you subject your wire to much greater forces if you tighten it to little!

To understand this you only need to imagine your rigging beeing slack and what happens in waves...the accelerationforces involved are far greater than the forces needed to keep the mast in place!

I hope you can see that the thing is exactly the same with keel bolts.

Rgds

Kristian

[forsailbyowner]

What kind of equipment did you use for melting/pouring the lead? Must you do it all in one batch?

[Kristian]

Hello Forsailbyowner!

I did not cast the keel myself so I´m sorry that I can not awnser that question.
I learned that many keels just as the one I have was not " true" at the top due the shape changing during cooling.

I did saw the keel true and fixed it to the hull using epoxy insted of mastics.

Rgds

Kristian

[Geminidawn]

You'll need one hell of a cruicible or two even one for the primary melt and waste removal and the second for pouring, be prepared to loose up to 30% in slag. Melting that much lead in one go is tricky work and a real hazzard so it's best to be avoided if you can.

I just finished a keel fo the Sailwind 27 which is an improvement on the production type. Where the production type is a 914kg, 3" thick flat shapeless slab of cast iron I sculpted mine out of hollow steel. I set a good framework with an aerofoil shape with the tip chord at .12 and the root chord at .8 and the maximum chord thickness at 30% back from the leading edge. This aerofoil hollow fin weighs only approx 300kg so I'll have to make up the rest of the weight using lead of which I can melt in smaller amounts as I am pouring it into a pre-formed "container". Once the 914kg mark is gained the rest can be bulked up with foam. Because the bulk of the weight is in the bottom the keel looks like a fin keel but behaves like a bulbous one.
If the volume of your keel is large enough you can also use the same method and fill with concrete, less of a hazzard and less of an expense.

[SabreKai]

I've had some experience casting lead. One of my boats was a steel HO-28. The keel was filled with scrap steel and cement. I ended up chiseling out the cement, and then removing and weighing the complete ballast. Given its dimensions I figured out its approx center of gravity and then recaluclated for lead. The result was that I could install about 6 inches of lead in the keel and then add water and waste tanks without disturbing the righting moment. So, the quest for lead began. I put 5 gallon pails out at a large number of garages I did business with and had them collect tire weights. After I got enough, I borrowed a smelter from the Ontario Boat Builders Coop. This is a large metal bin on legs, about 12x20 and about 9 inches deep. Underneath is a propane ring. Fire it up and start adding the tire weights. Scoop off the floating crud. I had a dozen ingot molds made up of 4 inch channel, cut with a slight bevel on the ends and capped with 1/8 sheet. I would line up the ingot molds and start dipping out lead, filling each one with one ladle full. Then back to the start and add another. I ended up with 3300 lbs of lead ingots, all pretty much uniform and none of them showed any signs of layering from not being poured all at once.

The only problem I ever had was one 5 gallon pail with about 2 inches of weights in it. I picked it up and up-ended it into a half full smelter. Instant explosion. Luckily I was behind the smelter and had installed a high back because of wind which deflected the spraying molten lead.

I forgot to check the pail for water. After that I went round and punched drain holes in each pail. even then I would take the last weights out by hand and dry them on an old towel if they were even slightly wet.

My landlord was not impressed. I spent about a month crawling round on my hands n knees cleaning up the mess. It got onto the driveway, the fence, my patio and a few other places. each bit had to be picked out with an awl.

So from this work I can tell you that you can pour it into a mold in small amounts. I would suggest that the mold be filled with ingots first by hand then pour the lead in around it and build up the layers of ingots till you get to the top. I seem to recollect that you can plane lead too. I haven't but some one I knew did it with his keel. He also used a chainsaw on it.

Sabre

[chala]

Originally Posted by forsailbyowner

What kind of equipment did you use for melting/pouring the lead? Must you do it all in one batch?

It is all depending if the lead is internal or external. Pouring bit at the time the lead will layer which is great in an internal keel if you have to remove some later on. I would not really like an external keel which is layered.

Kristian did you investigate pouring the keel up side down, I doubt that few tons of lead will shrink upward and float in mid-air.

[Kristian]

Hi Chala!

What an absolutely wonderful idea.
I do totally agree in that this would probably give you a much better result.
My hat of for you thinking upside down!!!

As I said I never did any of the casting work myself.

This beeing an external keel I do really not think it is suited for casting in many different layers and in addition to that you have to add correct amount of antomonium to increase the physical properties of the lead othervise being to soft.

On the original subject of forming lead I did also try to plane the lead but failed.
I´m very interested in a description on how this was done so Sabrekai if you can find that information I would be grateful.

My failed planing could of course be due the lead being tougher with the added antimonium.

Rgds

Kristian

[SabreKai]

Sorry my friend. The guy who planed the lead keel did it about 30 years ago, and I've long since forgotten the details of it. All I can recollect now is the boat sitting there with a nice square hole cut in the keel, lots of lead chips and a chainsaw laying there. I suspect it was a power planer, but that would be an expensive experiment if I'm wrong.

Sabre

[Geminidawn]

Originally Posted by SabreKai

Sorry my friend. The guy who planed the lead keel did it about 30 years ago, and I've long since forgotten the details of it. All I can recollect now is the boat sitting there with a nice square hole cut in the keel, lots of lead chips and a chainsaw laying there. I suspect it was a power planer, but that would be an expensive experiment if I'm wrong.

Sabre

I re-shape damaged lead keels sometimes using a "Surform" or rasp, to no great extent mind, just mainly on bulbs where they are in need of fairing after a repair. The lead soft as it is still has a severe blunting effect on the tools so whatever tool you go at it with make sure the blades are easily re-sharpened or cheap to replace.

[chala]

Lead can also be reworked, removed using a welding stick as a means of producing heat (maintaining an arc), a 3.2mm steel electrode at 180A will melt around 2kg of lead out of a mass, a slow process and also the melted lead will become polluted with steel. Beware of the nasty fumes. The heat need to be controlled and also the flow of the melted lead. A job that requires a lot of consideration and caution. Lead can be drilled using round wood drill bits at a certain speed. Metal drill bits have a tendency to screw in and shear. With know how lead can also be chased manually or mechanically or jack hammered. Due to the nature of lead expect a slow job and broken tools.