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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction
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  #21  
Old 05-07-2013
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Re: Encapsulated Keel?

My Ericson 39b has encapsulated lead. recently I had to do a repair of an old repair due to the keel being put down on the edge of a sleeper cracking the old repair. what I found was the glass was at least 1" thick at the sides and nearly 2" at the foot. the lead did not touch any part of the skin but was supported all around by large blobs of bog. I could only see the bottom 15" inside the keel the top of the keel is glassed over as is the leading edge of the bilge behind the lead.
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Last edited by SimonV; 05-07-2013 at 11:57 PM.
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  #22  
Old 05-08-2013
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Re: Encapsulated Keel?

I don't know those boats but looking at the pics I have a hard time thinking it's an integral keel. It's just too skinny. Call Bruce King. Tell him Bob sent you. We share a non sailing hobby. He'll tell you the truth.
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  #23  
Old 05-08-2013
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Re: Encapsulated Keel?

Quote:
Originally Posted by SimonV View Post
My Ericson 39b has encapsulated lead. recently I had to do a repair of an old repair due to the keel being put down on the edge of a sleeper cracking the old repair. what I found was the glass was at least 1" thick at the sides and nearly 2" at the foot. the lead did not touch any part of the skin but was supported all around by large blobs of bog. I could only see the bottom 15" inside the keel the top of the keel is glassed over as is the leading edge of the bilge behind the lead.
Whats "Bog"? Any pictures of the keel and repair?
Thanks!
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  #24  
Old 05-08-2013
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Re: Encapsulated Keel?

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Originally Posted by L124C View Post
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?
Not anymore, but 30 seconds of searching for Ericson 38 keel bolt will find you plenty of your own. I trust the guys over at ericsonyachts.org and their dozens of photos of Ericson keel bolts.

Since Bob is here: that keel shape seems really odd to me. It minimizes weight farthest from the hull, the opposite of most keel designs. Any thoughts on why it would be that way? It did make it easy to ID the boat.

thanks,
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  #25  
Old 05-08-2013
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Re: Encapsulated Keel?

Alex:
It's a long story.
But there was a time, you were probably a kid, when designers had this idea that for a keel to be efficient it had to have "eliptical loading".

Say that twice, eliptical loading. Good.

This meant that the loads on the foils ( and I probably have this a bit off) had to describe in a vertical plane an eliptical curve. I could draw it for you.

The idea was that the drag of the keel would dissipate towards the tip reducing the tip vortex ad it's accompanying loads.

This "eliptical loading" gave way to keels with plan forms that features curved leading and trailing edges. Sort of an eliptical shape to the planform. But this really had nothing to do with eliptical loading. You could achieve eliptical loading with a highly tapered keel with straight leading and traling edges. Eliptical edges were of a red herring. But people bought into it anyway and the weird thing is that it did have some benefits apart from eliptical loading. If you reduced the root foil you could reduce the interference drag of the keel, i.e. where the fin meets the hull. Keep in mind that the perfect keel was not attached to the boat.!!!!!!

Short story is we had a series of keels with that highly taered shape. I used it myslef on the Nordic boats. It made sense. But it did put the VCG pretty high up on the fin. But the damn boats sailed really well.

Now we know better. It's better to get the VCG of the keel as low as possible, make the bat stand up and take advantage of the sail plan.

Phases and trends:
Yes, we went through quite a few. Some worked to some degree and some were bogus. But in the end we learned ( some of us) a little bit more about what makes a boat go.

Does that make any sense?

I have to go now. I'm certain there is someone I need to be rude to.
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  #26  
Old 05-09-2013
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Re: Encapsulated Keel?

Thanks, that does more or less make sense, and gives me more to search on. I really appreciate you hanging around here (and on sailing anarchy) and providing context, design history, and sharing your thoughts on sailboat design.

I've been trying to wrap my head around different keel plans (not fin vs full, but different designs of fin keels and different B/D approaches) and how they affect sailing ability. This comes from seeing how differently my Pearson 28-2 (low B/D) and a friend's Yankee 30 (high B/D) sail even though both have the same LWL and close SA/D. His boat is over 2000lbs heavier, and almost all of it is in the keel. The mast is 4' taller to make up for that. It's interesting seeing how my boat gets pushed around in following seas, while his extra weight keeps the boat on track. Speed and performance wise they feel quite similar.

Researching those differences has lead me down many other tracks and paying attention to things like odd Ericson 38 keels.
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Re: Encapsulated Keel?

Quote:
Originally Posted by L124C View Post
Whats "Bog"? Any pictures of the keel and repair?
Thanks!
I thought every one knew what bog was, maybe it an Aussie thing!...It can be polyester resin or epoxy resin, thickend with talc or micro balloons. mainly used for fairing or leveling. Also a great glue. Can be bought in two part cans, but that is expensive.
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Re: Encapsulated Keel?

Quote:
Originally Posted by SimonV View Post
I thought every one knew what bog was, maybe it an Aussie thing!...It can be polyester resin or epoxy resin, thickend with talc or micro balloons. mainly used for fairing or leveling. Also a great glue. Can be bought in two part cans, but that is expensive.
Hadn't heard that term in that context before, but I'd gotten the gist of it..

We have similar products here, of course, including short and long strand filled polyester fillers, often called 'carpatch' that can be used to good effect as well.
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  #29  
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Re: Encapsulated Keel?

Simon:
We use "bog" over here too.

Alex:
I'm not sure what you see in handling differences in a following sea with your Pearson and the Yankee have anything to do with displacement. I think it may have more to do with the fact that they are very different hull shapes. Very light boats can track beautifully.
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  #30  
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Re: Encapsulated Keel?

My Pearson 28-2 tends to get pushed around quite a bit in following seas (not even overly big ones, just the ~2 foot wind waves that we get in Puget Sound). If we get the right sail plan it will start surfing, which keeps it better under control (and brings up the speed). It can get quite tiring going downwind in over 20 knots of wind.

The Yankee 30 tracks a whole lot better and seems to sit in the waves rather than climbing over them in the same conditions. The ride is smoother and easier. We sailed from Eagle Harbor to Shilshole side by side a couple of months ago and it was very obvious.

I had guessed that some of this might have to do with his boat having a lot more ballast (BA/D is close to 50%, vs about 33% on my Pearson) and having the ballast lower down. The Y30 has a deep bilge with the lead hung down low. My Pearson has a thin bolt on keel with a very shallow bilge, so the weight is higher up.

I'd think that the Yankee's extra weight would hurt it in light airs, but he seems to do okay there too. There is a lot of extra sail area to make up for the extra weight, so the SA/D is about the same on both boats (a little under 17...squarely in the cruising not racing range).

I haven't looked at enough boats out of the water to really understand hull shapes very well. Is there a book that you'd recommend for someone trying to understand the basics? The boats are very obviously different there, the Yankee has a much longer keel (though still a fin) and a big skeg where my Pearson has more of a fin keel and a spade rudder.

I quite like how my boat sails in general, this is just one big difference that I noted.
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