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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > Twin Keel vs Bulb Keel
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Topic Review (Newest First)
05-15-2003 10:27 PM
thefantasea
Twin Keel vs Bulb Keel

The Merriam-Webster Dictionary carries this entry:

Main Entry: road∑stead
Pronunciation: ''rOd-"sted
Function: noun
Date: 1556
: a place less enclosed than a harbor where ships may ride at anchor
05-14-2003 01:36 AM
garyp
Twin Keel vs Bulb Keel

I would think "roadstead" would be the passage into the anchorage, while rodestead would be the anchorage (the place where you drop your rode.)
Just kidding.
04-04-2003 05:42 PM
paulk
Twin Keel vs Bulb Keel

Have to agree that it would be simpler to leave the lead exposed on the keel and box in the bilge/garboards with steel & floors and bolt the lead assembly to it. Lead is a great cushion if you hit something hard. (We know -- but that''s another story...) If you poke a hole in a steel casing that''s holding your ballast you can develop some nasty problems before you know it. Woodenboat has had several articles on pouring lead keels and moving them around with farm tractors, winches, and tackles. Sounds quite straightforward if you think it through. Unless you absolutely require shallow draft, twin keels are not the way to go. They''re lighter, individually, but imagine the fun you could have making sure they''re both parallel with the hull and each other...!
04-01-2003 10:51 PM
megman
Twin Keel vs Bulb Keel

One of my main considerations for using steel was that 9"x6" Elm is damn near impossible to get, which is what is called for to build the keel up.

Steel is used for the Twin Keel version. Only stands to reason it should be fine for a single.
I''m just trying to do this with what is available, yet still usable.
04-01-2003 07:28 PM
Jeff_H
Twin Keel vs Bulb Keel

I think that Rodestead (also and perhaps more correctly spelled Roadstead) is interchangeable with anchorage. I used to hear the term used when I was a kid and it was often used for an outer anchorage so that someone might say, "The inner anchorage was full so we anchored out in the outer rodestead." That said I am not really sure that there really is a difference between Anchorage and Rodestead though.

Jeff

Jeff
04-01-2003 07:17 PM
Jeff_H
Twin Keel vs Bulb Keel

Stainless steel may actually be a worse choice because it is even more prone to crevice corrosion and because it is dimensionally pretty unstable when heated. When you apply heat to stainless steel to stainless it tends to distort and lose fairness. It is also quite difficult to get bottom paint and fairing materials to adhere to stainless steel but stainless steel provides a poor surface for fouling meaning that barnacles can adhere to the stainless steel very tenaciously.

This is sounding like a worse idea with each post. Why not pour the keel and attach it as it has successfully been done for the past two or so centuries. It will be cheaper and easier and have a better result in the long run.

Jeff
04-01-2003 07:06 AM
megman
Twin Keel vs Bulb Keel

Well not worried about movement as I would be welding some cross members also into the cavity to eliminate the chance of that. Not sure what the solution would be to eliminate any shrinkage.

I did mention I would be using 1/8" steel for the keel. I should have mentioned that it will be "stainless" steel with stainless welds. This will cut down on the maintenance.
04-01-2003 03:51 AM
DuaneIsing
Twin Keel vs Bulb Keel

Jeff_H,

Besides all the other good info, thanks for teaching me a new word: rodestead. Do you discriminate between "rodestead" and "anchorage"?

Duane
04-01-2003 03:05 AM
Jeff_H
Twin Keel vs Bulb Keel

Actually, you need to be very worried about shrinkage as the lead will pull away from the steel when it shrinks and will create a cavity that is perfect to allow crevise electrolysis in the cavity between the steel and the lead. Depending on the design of the keel, this cavity can be as large as and inch or more fore and aft, and a 1/4" side to side. Beyond that the lead is free to move within this cavity giving it momentum to shift and do damage in a grounding or shift and make a lot of noise in a rolling rodestead. The more traditional way to do this is to extract the lead after the pour, and to fill the cavity with a semi-soft material like hot tar or concrte (I don''t especially like concrete as it traps moistre against the steel) and then put the lead back in. This fill helps to restrain the lead as well as eliminate the cavity. Frankly it would be easier to extract the lead and not even bother with keeping the steel which will be a maintenance pain in the butt over the life of the boat.

Jeff
03-31-2003 07:45 PM
megman
Twin Keel vs Bulb Keel

Thanks geohan. Excellent idea.

The ingots I''ll probably be dealing with are 50-60lbs and 18"x4"x4" and this would allow a good continuous pour also.

Not too worried about shrinkage as it will just be filling the steel casing.
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