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Discussion Starter · #1 · (Edited)
Saw this Ericson in the yard the other day. I'm under the impression Ericsons have encapsulated keels and was struck by the narrow profile of this one. If this keel is encapsulated, it's hard for me to believe the narrow profile of the FRP could take the lateral stress induced by the led while heeling. How does it work? Does the lead become a structural component? What would the ratio of lead to FRP be 3/4 down the keel? How day do dat?
 

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baDumbumbum
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Our Albin Ballad has an integral keel. Even with a 47% ballast ratio, all the lead is in the bottom 32" or so. Which leaves more room for structural FRP & flooring up high, where the stresses are. Think of it this way: the farther down the keel you go, the lower the leverage on the assembly. At the very tip of the keel, the glass only has to support the lead right at that level. Move up six inches, the glass has to carry its lead plus the weight plus the moment arm created by the lead below it. Up another six inches, the glass has to support its lead plus the weight plus the moment arm of the 12" below it. And so on. The trick is to run out of stress (lead + leverage) before your FRP runs out of strength. :D This is a calculation NAs are quite capable of making.

The difficult aspects come from dynamic loading, which is always a fudge, and in achieving good layups inside a deep, narrow keel or skeg. I haven't heard of too many encapsulated keels tearing off, so presumably they got it approximately right.:)
 

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Look in the bilge under the cabin sole... if there are keel bolts then it's a bolt on keel. Tap on the outer surface of the keel.. are you hitting (painted) metal or fiberglass?

I'm sure it's a lead keel, and I was under the impression that that model has a bolt on keel but not positive.
 

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Don't know the details of your boat but you can think of it somewhat like a cored hull. Depending on tack one skin is in compression and the other extenson. If glass lay up is not on bias of forces it can easily handle loading. Also some boats use various sub structures to transfer loading to grid structure (stringers etc.) inside hull. Very rigid and strong if done correctly and no issue of keel boat corrosion or metal fatigue concerns. ?Is it an erickson made by PSC. They made great strong boats.
 

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I once saw a fibreglass boat hauled out in Auckland, which had had an encapsulated lead keel. It hit St Heliers reef, the fibreglass around it had broken, and the lead sunk. The boat floated to her haulout . You could see the neatly broken line, where the fibreglass had cleanly broken around the profile of the lead. Only the fibrglass which was put over the lead had stopped her from sinking.
I'd want a bit more than the fibreglass holding the lead it. Pouring molten lead into fibreglass has to effect the glass.
 

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baDumbumbum
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Look in the bilge under the cabin sole... if there are keel bolts then it's a bolt on keel. Tap on the outer surface of the keel.. are you hitting (painted) metal or fiberglass?

I'm sure it's a lead keel, and I was under the impression that that model has a bolt on keel but not positive.
If replying to my post.... The Ballad keel is most certainly integral -- no bolts. You see the light streak running down the keel in this photo?



That's the drain plug in the aft keel sump. The lead ballast starts just below that line.

The Ballad's lead was supposedly laid in place as formed ingots, not hot-poured as with some Morgans. Which method I agree sounds horrible, but many many boats have poured lead keels & again, very few have fallen off. For every example of an integral keel failure you can toss out, Brent, I'll match you with a bolt-on keel failure.;) There's no surety your Auckland boat would not have lost its keel -- and perhaps its stub -- had it been bolted on. Either attachment method is fine if the engineering was sound and the layup done properly. Jeremy Rogers built Contessa 32s with integral keels. Not a weak boat.
 

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grumpy old man
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I have done many internally ballasted, "encapsulated keel" or "integral keel" boats. I've done a similar number of bolt on lead keels. Either way done correctly is fine. I like bolt on from a designj perspective because it gives me a free hand in shaping the ballast. With an integral keel you shape and foil distribution has to be suxch that you can pull the boat from the mold. Ionce poured hot lead into an integral GRP keel on my own half tonner. It worked fine. That boat is still around.

Once again, generalizations about a keel type are silly. If the boat is well designed and well built either an integral or bolt on keel will be fine. With all my designs with integral keels I cannot think of one that has had a keel problem and I would estimate I'm talking about over 2,000 boats. Maybe there has been a few but I have never heard about them.
But, when there is a problem like a keel failure I am usually one of the first to be called.
 

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Bruce King boats have both internal and external ballast depending on year and model. Most of his older boats had internal ballast glassed in and bolted to discourage shifting of the lead so you may see bolts on internally ballasted boats.
 

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One of None
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Bob how great in layperson's terms are the lateral stresses on keels?
 

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That looks like an Ericson 38 with the "competition" keel. A quick search showed me that these are bolted on.
 

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baDumbumbum
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Regards the OP's question, and with reference to Outbound's point about the keel as core-box: I found details in the manufacturer's handbook on our boat. The layup thicknesses are 8mm topsides, 10mm below waterline, 25mm (1") at the hull/keel transition, and a mere 6mm down the keel sides. I'm not sure if NAs include whatever structural properties the ballast may exhibit in their calculations, or if they just treat it as a generic, non-compressible core material & focus all their attention on the FRP skins. *shrug* Whatever methods they use/used have proven adequate -- it's astounding how few recreational or cruising boats drop their appendages.:)
 

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Good question for Bob. Haven't a cue. Just thought most of the lateral loading would be at or near the canoe body appendage transition and would note skins are 1" thick there. Seems you're probably right-antimony hardened Pb should have some structural benefit.
 

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grumpy old man
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"In layperson's terms"?
I would say great. There are impact loads and there are bending loads. Imagine you have your chute up and it's blowing. You do a round up and are knocked down say 90 degrees. The chute collapses and the boat begins to right itself. The chute starts to fill and fills with a bang that shakes the boat and because you have rounded up the chute is still luffing so it fills and dumps several times each time with a big "bang" is not the right word maybe "huge thump" is better. This filling and dumping shakes the entire boat and with the boat still pretty much on its side the lateral forces on the keel joint are great. I could lie to you and say there was a precise way of calculating that but there is not. At least not with the tools the typical yacht design office has. We can guess and we can use safety factors. We can try to simulate it on paper but it's hard to replicate the dynnamics of what happens at sea. We can use CE regs to insure the keel meets those requirements. We can use LLoyds or one of the other certification bureaus scantling standards. I would not include any benefit from the lead or iron ballast in the calculations as there is no way of being sure the skins are bonded to the ballast completely. There is always a possibility that you are going to do something with your keel involving wind, waves and rocks that the designer did not have in mind and that is regardless of whether the keel is bolted on or integral with the hull. The best insurance is plenty of deep and strong floors in the way of the keel with an extra strong floor right at the trailing edge so if you impact the leading edge hard you will not drive the trailing edge up through the hull. I once hit a rock pretty square at 6.5 knots with a bolted on keel. It got very quiet on board for a couple of minutes while we checked the bilge area for damage. There was none. We did put a softball sized divot in the leading edge of the keel though. That was on NIGHT RUNNER a cold molded boat. My AMATI, another 41'er composite build with a high aspect ratio, deep bolt on fin/bulb keel hit a rock hard and managed to break a couple of floors but it did not take on water and had no hull skin damage. We beefed up the floors when it was repaired.
 

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grumpy old man
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Keep in mind, and I'll speak for the way I do it knowing that most designers do it this way, I'm certain there must be exceptions. If you use ABS or LLoyds or any other certification bureau you will chose your laminate thicknesses from their scantling rules based on the dimensions of the hull. LLoyds and ABS are particularily conservative. The rule will give you a thickness for the keel shell lam. But the way you physically layup the boat on centerline is to take the laminate from one side and wrap it accross the centerline essentially doubling the centerline laminate so you don't just have a lam butt joint on centerline. This is pretty standard practice. That's why a Valiant 40 is an inch thick on centerline. And because we are talking about an area well below the VCG of the boat there is little impetus on a cruising boat to go light.

If this structural stuff interests you try this:
Google "the front fell off".
 

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"The Front Fell Off" was priceless. They had me completely taken in until the "no cardboard or packing tape" part. I thought the guy was just your basic condescending idiot bureaucrat until then.

Monty Python never did better. :D
 

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To good to stay hidden:

 

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Discussion Starter · #20 · (Edited)
That looks like an Ericson 38 with the "competition" keel. A quick search showed me that these are bolted on.
If true...that explains things doesn't it? Though, the keel in post #7 is very narrow.
Didn't know bolt on was an option with Ericson. Do you have the link?
 
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