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  #1  
Old 09-19-2001
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Encapsulated or Bolt On Keel?

I''m shopping for my first sailboat (fast coastal cruiser) and ran into a boat with an encapsulated keel. All others I''ve seen were bolted on. What are the potential advantages/drawbacks for performance and structural integrity? The boat is a Dehler 35 Optima.

Thanks, Art
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Old 09-20-2001
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Encapsulated or Bolt On Keel?

Encapsulated vs. bolt on keels:

This is another one of those ''no one universally right answers'' questions. In other words an argument can be made for either type of keel. (For the record, I personally strongly prefer a bolt on keel rather than an encapsulated keel.) Here''s the way I see it.

Bolt-on keels tend to offer more performance since the ballast must be cast and without the keel stub skin thickness tend to be lower relative to the center of bouyancy. They also have significantly less wetted surface and frontal area making them theoretically faster on all points of sail. They are simple to repair and generally can be repaired satisfactorily no matter how bad the mistake.

On the down side they are more expensive to build; requiring precision casting, bolt hole drilling and a lot more hand fairing. They are higher maintenance requiring fairing every 10 years or so and new keel bolts at some point in the boat''s life.

Encapsulated keels are less expensive to build. There''s less labor and less precision required. Boat builders will often use less expensive forms of ballasting with encapsulated keels, such as iron or lead scrap cast in concrete, resin or other binder further reducing costs. If they are not damaged in a grounding, encapsulated keels are less expensive to maintain.

On the down side they are less efficient. Their real downside is the difficulty in doing a proper repair. Typically, in a hard grounding a number of things happen on an encapsulated keel. Typically the skin of the keel encapsulation gets ruptured and separates from the ballast. This allows water into the small cavities between the keel and the ballast and once wet it can mean the ''beginning of the end'' for the boat as this permanently wet fiberglass blisters itself from the interior and the wet areas spread around the ballast. This is especially a problem on a boat that is hauled out for cold winters where freeze/ thaw cycles can really pry the skin loose from the ballast. The problem gets worse when the ballast contains ferrous materials. Here the ballast begins to rust and can reduce the ballast into a loose mass of matrix and rusting iron.

Beyond that, in a grounding the ballast is often forced upward as well. In an encapsulated keel the membrane of the hull is at the outside of the keel and the membrane above the ballast is often quite thin. In a bad grounding the ballast keel is often is pushed through this membrane causing a serious and difficult to repair damage and leak.

We grounded a boat with an encapsulated keel that we never could permanently fix for as long as we owned the boat. The problem would get worse with every year, spreading from a small dimple on the leading edge of the keel to an area that was much of the bottom and sides of the keel.

Lastly, it is very hard to lay-up the glass in the keel cavity. As a result the glass work in this vulnerable area of the boat is often inferior to the glass work elese where on the boat.

I am surprised that the Dehler has an encapsulated keel. Most of their boats have a bolt on keel.

Good luck
Jeff
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Old 10-03-2001
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Encapsulated or Bolt On Keel?

Right you are Jeff_H, this Dehler 101 has a bolt-on iron keel. The owner and broker thought it was encapsulated(!?). The table post must be unbolted to remove the right floor panel to even see the bolts, which were in pristine condition.

Thanks for your detailed response on this issue, as well your responses to many queries on this board. I am relatively new to sailboats and sailboat systems, and I really appreciate your well balanced, well informed input.

Art

San Diego



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Old 02-15-2002
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Encapsulated or Bolt On Keel?




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Old 02-15-2002
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Encapsulated or Bolt On Keel?

Jeff,
With all due respect. When you wack into somthing with a external ballasted boat,
nine times out of ten (if not ten times out
of ten) the boat will have damage to the
leading and trailing edge fillet , not to mention the damage caused by the "fulcrum and lever" effect caused by the
keel trying to yank the keel bolts through the floor (and that lets water in).

The worst that can happen to a internally ballasted boat is that a little water gets
into the ballast area.At the end of the season, when you normally haul out,
tilt the boat to the stearn drill a couple of holes aft in the tip chord and in the spring
simply patch up the holes that were drilled in the fall. No water in the boat, no
extensive fiberglass repairs and no emergency haul-outs and no keel bolts to replace every ten years or less. Iam a profesional fiberglass repairman and have never in the twelve years Ihave been in this buisness saw or heard of such damage to e-keels like you have fore mentioned . Its true some builders have thrown junk in and covered it with cement.Do a little reasearch, you will find out what builders did this.I will trade
a tenth of a knot for an the security of an encapsulated keel any time. In fact,
I already have

Dennis L.
s/v Pangaea-Buzzards bay






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Old 02-15-2002
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Encapsulated or Bolt On Keel?

It is very hard to do proper glass work in the tight confines of a keel stub. The glass work that I have personnally repaired in that area has been really poor almost by necessity. The leverage of a hard grounding does not go away when you hit hard just because there is a skin between the keel and the rock. Instead the ballast gives the rock something hard to push against and the comparatively thin membrane above the ballast has to absorb all of that leveraged load.

So, having owned a Pearson Vanguard that had an encapulated keel that hit a rock at not a terribly high speed and had the encapulation readily crush, driving the aft end of the ballast through the comparatively weak membrane above the ballast and dislocating the water tank. And after trying fruitlessly to get a decent repair and never being able to get a bond between the ballast and the encapsulation shell, I can readily assure you that a lot worse can happen than,"The worst that can happen to a internally ballasted boat is that a little water gets into the ballast area." You can end up with a boat that cannot be repaired.

Jeff
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Old 02-16-2002
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Encapsulated or Bolt On Keel?

Jeff,
Are you trying to say that you think internally ballasted boats take ground better than externally
ballasted boats?
How fast were you going????
I dont dispute this happened to your Vanguard. They were built in a time when builders did not know alot about this material. Since the late sixties these relativly weak areas have been realized
and this acurance simply does not happen anymore because these areas are now heavily fortified because it is a very difficult area to work in. Furthermore,
a boat with a deep full modifided keel has its ballast very low in the keel. It would be hard to repair at any rate. But as I stated before, this problem has been delt with.
What do you think would have happened to the ex- ballasted boat in the same circumstance???. ex- ballasted boats require maintainance int ballasted
boats simply dont. Ex- ballasted boats do not take a collision well at all.And as far as speed, how much do you really benifit? A tenth, maybe two tenths of a kt?
My good friend had a Sabre 34 deep draft and I would beat him nine times out of ten. The truth is that with a well designed boat there really is not much of a difference,if any, at all. (Unless your talking about a racing sled)
The external ballasted boat came to pass simply because of the need for speed- and thats not a bad thing...
...just dont hit any thing.

Dennis
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Old 02-19-2002
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Encapsulated or Bolt On Keel?

Bolt on or encapsulated????
Check out this site;

http://www.cliffisland.com/boat.html
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Encapsulated or Bolt On Keel?

I am not sure what the photos indicate about bolt on or encapsulated keels. The keel stub failed at the hull above the keel joint and not at the keel bolts or athwartship frames. This is an area of the boat where a failure could have occured with either a bolt on or encapslated keel. In some whats a bolt on should do better in this kind of situation since a properly engineered bolt on keel has a lot more structure (athwartship framing) than an encapsulated keel. (That athwartships framing in one of the disadvatages of a bolt on because it prevents having tanks in the bilge as easily as you would with an encapsulted keel.

This accident was actually pretty widely discussed on the internet a while back. It is my understanding that the failure occured in an area actually above the keel joint where there was a large section of rotted core thought to have been possibly damaged in an earlier grounding.

In any case, it is a very dramatic set of photos and I am really glad that all escaped without major injury.

Jeff
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Encapsulated or Bolt On Keel?

Jeff_H,
I''m sorry , I just can''t see how you can keep on saying bolt on''s are equal to an internals durability and strength! An internal is intigral.

Dennis L.


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