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Old 08-01-2020, 20:25   #16
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Re: Lead vs. Iron bolt-on Keels

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Originally Posted by billknny View Post
This is one of those statements that gets repeated very often, but with very little actual data supporting it. In a serious hard grounding the amount of energy dissipated by deforming lead is VERY small. Even a catastrophic collision that severely damages the hull of the boat results in a very small amount of lead being deformed, and very little of the collision energy is lost that way.

The typical argument goes like this: "Look at that mangled lead keel! Imagine what would have happened to that boat if it had been cast iron!" Quite likely--nothing. Lead deforms at loads FAR below where cast iron would crack or otherwise fail.

It is theoretically true that there are collision energies that a lead keel might dissipate and reduce hull damage compared to a cast iron keel, but it's a VERY narrow range without practical significance. In a serious grounding, far, far more important than the material of the keel is the actual design of the hull and keel, the quality of construction, and the condition of the keel bolts.

If I was designing a boat from scratch, I'd rather use lead. It's density gives you some design options that cast iron wouldn't allow. But there are excellent cruising boats out there that have cast iron keels.
Do you have some or actual engineering data, or is that just a feeling? My own feeling, not backed up by numbers, so not worth much, is that the softness of lead keels might considerably dampen the shock from a hard impact with a rock. I'm ready to change my mind if there were some actual engineering somewhere.

One objective advantage of lead keels is that a given mass of lead weighs more in water than the same mass of iron, because it has less volume and so less buoyancy. The reduced volume means better hydrodynamics, too. This is why expensive boats always have lead keels, and why depleted uranium and tungsten keels were banned for the Americas Cup.
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Old 08-01-2020, 20:31   #17
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Re: Lead vs. Iron bolt-on Keels

so it should be remembered that bolting-on a sailboats keel is entirely a nod to ease of manufacturing and transportation and not to seaworthiness. in a perfect world all sailboats would have encapsulated/integral keels.

let the outrage begin...
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Old 08-01-2020, 22:20   #18
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Re: Lead vs. Iron bolt-on Keels

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Originally Posted by robwilk37 View Post
so it should be remembered that bolting-on a sailboats keel is entirely a nod to ease of manufacturing and transportation and not to seaworthiness. in a perfect world all sailboats would have encapsulated/integral keels.

let the outrage begin...
Umm, I kinda feel outrage coming on!

As has been mentioned, encapsulated ballast has some drawbacks, but to me the biggest reason your statement is flawed is the impossibility of designing a modern high aspect bulb keel as an encapsulated structure... and, like it or not, such keels have distinct performance advantages over the typical encapsulated models.

So, even in a perfect world some boats would have bolt on keels!

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Old 08-01-2020, 22:32   #19
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Re: Lead vs. Iron bolt-on Keels

And my outrage.

An encapsulated keel means a hard grounding will damage the hull, not the external keel. Proper fiberglass repair is more complex (expensive and time consuming) than pounding out and fairing a dented external lead keel.
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Old 09-01-2020, 00:12   #20
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Re: Lead vs. Iron bolt-on Keels

[QUOTE=sardinebreath;3051624]I get the density and shock absorption advantages of lead, but I have run across several cases where keel bolt corrosion pretty much created a throw away sailboat (QUOTE]

Wow.
Quite a judgment.
My bolt on lead keel went from 8 bolts to 16, while in the slip. Glad I didn't know that my boat was a throw away.
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Old 09-01-2020, 01:57   #21
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Re: Lead vs. Iron bolt-on Keels

Lead works as an anode for stainless steel (at least 304 and 316), so the chances of the keelboats corroding away is actually less. But there is pretty little potential difference.

Once upon a time lead keels were cast with square hollows that would take a nut. These were filled with putty (or lead) after mounting the keel to the boat. That means that the keel bolts were easily removable. Today manufacturers use J-bolts, makes it slightly cheaper, but not easily maintainable.

In my opinion, lead is a superior material for many reasons. It is denser, so the CG will be lower. It does not rust. It absorbs some shock when grounding.

I do not worry about my bolt-on keel. Mostly because it is fastened in solid 3.5" fiberglass, integral with the hull and not in an interior liner glued to the hull. Also the keel bolts are oversize - as they should be. And as it is a lead keel, there is little risk of the bolts or the surrounding material corroding.

There are reasons to use bolt on keels, except for being cheaper. There is precious little tensile strength in fiberglass, but a lot in stainless steel.
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Old 09-01-2020, 02:15   #22
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Re: Lead vs. Iron bolt-on Keels

Quote:
Originally Posted by robwilk37 View Post
so it should be remembered that bolting-on a sailboats keel is entirely a nod to ease of manufacturing and transportation and not to seaworthiness. in a perfect world all sailboats would have encapsulated/integral keels.

let the outrage begin...
Hmm, so how would you mould the hull I posted a picture of in Post No 10?

It might be possible, but would you be willing to pay for all the extra labour involved in the initial purchase cost?

Could you then dry out the yacht on a regular basis if it has GRP and encapsulated keels without damage?

Should they all be fin keels instead? well 50% of the 305 Moody 31s are bilge keels so there was certainly a demand when they were produced.

The manufacturers will have made a business decision based on a design, the the cost to build, their required profit margins, from numbers they expect to sell. Mostly they get it right, sometimes not, but that is just business. It's a competitive market and very price sensitive, for example the use of iron over lead. If you don't believe me, then ask yourself how many standard production European yachts are made with encapsulated keels today?

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Old 09-01-2020, 04:19   #23
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Re: Lead vs. Iron bolt-on Keels

Quote:
Originally Posted by robwilk37 View Post
so it should be remembered that bolting-on a sailboats keel is entirely a nod to ease of manufacturing and transportation and not to seaworthiness. in a perfect world all sailboats would have encapsulated/integral keels.

let the outrage begin...
Let me turn that around - since well executed bolt-on keels work perfectly well and have been known to last for a century, and have significant advantages besides economy, why would anyone today build a boat with an encapsulated keel?

Oops, no one does. Swan, Oyster, Hallberg Rassy, Contest, etc etc etc - all the world's best, cost no object sailing yachts, all have no kind of keel except bolt on.
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Old 09-01-2020, 06:29   #24
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Re: Lead vs. Iron bolt-on Keels

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Let me turn that around - since well executed bolt-on keels work perfectly well and have been known to last for a century, and have significant advantages besides economy, why would anyone today build a boat with an encapsulated keel?

Oops, no one does. Swan, Oyster, Hallberg Rassy, Contest, etc etc etc - all the world's best, cost no object sailing yachts, all have no kind of keel except bolt on.
I totally agree with you. And they have a proven track record. Keel failures are extremely uncommon in cruising yachts. They happen mostly in racing yachts, for obvious reasons.

Encapsulated keels are a solution to an almost non-existing problem and bring their own problems.
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Old 09-01-2020, 08:39   #25
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Re: Lead vs. Iron bolt-on Keels

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Originally Posted by Cadence View Post
I would imagine redheads could be used either.


I suppose by Redheads you mean expansion anchors. Actually not a great choice, pullout strength leaves a lot to be desired, especially so in a soft substrate like lead.

There a a few types that great a bell at the bottom of the hole that have a lot more pullout strength.

Better move is to cut into the side of the keel and create a pocket so a bolt with big washers and a nut can be installed. There was an article in GoodOldBoat last year covering this.
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Old 09-01-2020, 09:05   #26
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Re: Lead vs. Iron bolt-on Keels

..the one exception to internal ballast would be a steel hulled boat. It is impractical to try and sandblast the inside of a steel keel. This is where the lead comes handy.

...my Roberts had a hollow steel cavity in the keel. I placed small lead ingots in there, about 40 lbs each, and then melted them down with an oxy-ace. torch so as to fill the cavity with no air gaps.

...after I was done, I slathered everything with coal-tax epoxy. That boat, now approaching 40 years old, is still going strong.

...I remember a ferro-cement pinky schooner one time that also had a "hollowed out" keel void. This, the builder filled with steel punchings and then poured concrete over the entire mess.

...ok, these are all 80's built homebuilt boats. The build your own boat craze has gone the way of the dodo bird...but back in those days, there were several fiberglass boats I can recall, all with lead filled keels.

...the " bolt on" version of keels, be they lead or steel, in my humble opinion, is a manufacturing design to simplify building a new fiberglass boats. As any manufacturer would be likely to do, they will look for the least expensive and least complicated way to accomplish.
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Old 10-01-2020, 07:36   #27
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Re: Lead vs. Iron bolt-on Keels

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Originally Posted by MicHughV View Post
...the " bolt on" version of keels, be they lead or steel, in my humble opinion, is a manufacturing design to simplify building a new fiberglass boats. As any manufacturer would be likely to do, they will look for the least expensive and least complicated way to accomplish.

The fact that bolt-on keels may be cheaper to build than encapsulated (if that's even true, and I'm not actually sure about that), would not indeed mean that economy would be the only reason to build a boat that way. That's a logical fallacy. If it's cheaper then that's one reason, but that says nothing about other reasons.


Encapsulated keels stopped being used by builders, including cost-no-object builders where economy (if there is in fact any economy, with bolt-on keels) would not be the first tconsideration, when keel shapes changed from full keels or long fin keels to higher aspect and more hydrodynamically efficient keels. Most cruising boats did not already have full keels or any kind of encapsulated keels already by the 1980's. Bolt-on keels make it possible to reduce the volume of the keel to the minimum, and to increase the aspect ratio, which improves righting moment, increases lift, and reduces drag, making the boat sail better. I can guaranty you that Swans don't have bolt-on keels as an economy measure, and ALL Swans have bolt-on keels, and have since they were first made.



Whether it's cheaper or not I also actually doubt. A well executed bolt-on keel requires a massive structure. The cost of a higher aspect (shorter) keel is that the loads are more concentrated, and the boat's structure has to be designed to deal with that concentration of loads. On high end boats I guess this is quite a bit more expensive than an old fashioned, low stress, long, shallow, encapsulated keel, but the cost will pay off in spades with a faster, better sailing boat with much better ability upwind (the keel is a wing).
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Old 10-01-2020, 15:56   #28
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Re: Lead vs. Iron bolt-on Keels

..I will admit....I'm old school.
In my day, sailboat builders were not " mass" producing like they do today.
The ability to pour and form a steel keel was simply not available then, especially so the "winged" keel variety, so internal lead was the ballast of choice.
Like automobiles, times have changed.
Good, better, worse....who knows....every sailor has their preference which often guides them to a particular boat...
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Old 10-01-2020, 20:59   #29
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Re: Lead vs. Iron bolt-on Keels

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...
Like automobiles, times have changed.
Good, better, worse....who knows....every sailor has their preference which often guides them to a particular boat...
Absolutely agree. No one can tell you what to like.
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Old 13-01-2020, 14:04   #30
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Re: Lead vs. Iron bolt-on Keels

I would check at least one keel boat every haul out on an iron keel.
The buyer of my last boat didn't do that. The keel fortunately fell off in the slip and not while sailing.
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