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  #11  
Old 05-07-2013
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Re: Encapsulated Keel?

That looks like an Ericson 38 with the "competition" keel. A quick search showed me that these are bolted on.
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  #12  
Old 05-07-2013
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Re: Encapsulated Keel?

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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  #13  
Old 05-07-2013
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Re: Encapsulated Keel?

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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Old 05-07-2013
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Re: Encapsulated Keel?

"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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Last edited by bobperry; 05-07-2013 at 08:03 PM.
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Old 05-07-2013
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Re: Encapsulated Keel?

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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Last edited by bobperry; 05-07-2013 at 08:43 PM.
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Re: Encapsulated Keel?

thanks Bob.
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Old 05-07-2013
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Re: Encapsulated Keel?

"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.
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Re: Encapsulated Keel?

To good to stay hidden:

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Re: Encapsulated Keel?

Wait just a gol darn minute!
Are you guys trying to tell me this was a spoof?

As far as I can figure out life is a spoof.
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Old 05-08-2013
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Re: Encapsulated Keel?

Quote:
Originally Posted by Alex W View Post
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?

Last edited by L124C; 05-08-2013 at 05:54 PM.
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