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L124C 04-27-2013 02:03 PM

Encapsulated Keel?
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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?

deniseO30 04-27-2013 02:42 PM

Re: Encapsulated Keel?

bobmcgov 05-06-2013 11:22 AM

Re: Encapsulated Keel?
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.:)

Faster 05-06-2013 11:27 AM

Re: Encapsulated Keel?
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.

outbound 05-06-2013 11:35 AM

Re: Encapsulated Keel?
4 Attachment(s)
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.

Brent Swain 05-06-2013 03:43 PM

Re: Encapsulated Keel?
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.

bobmcgov 05-06-2013 05:23 PM

Re: Encapsulated Keel?

Originally Posted by Faster (Post 1026244)
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.

bobperry 05-07-2013 11:52 AM

Re: Encapsulated Keel?
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.

barefootnavigator 05-07-2013 03:33 PM

Re: Encapsulated Keel?
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.

deniseO30 05-07-2013 03:41 PM

Re: Encapsulated Keel?
Bob how great in layperson's terms are the lateral stresses on keels?

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