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-   -   telescopic keel ? (http://www.sailnet.com/forums/general-discussion-sailing-related/433-telescopic-keel.html)

innovator 12-14-2000 02:15 AM

telescopic keel ?
 
I would like to travel down shallow rivers using a 50 ft sailboat, rather than have a fixed keel that limits depth, could I have a keel that would
travel or slide up into the mast?, a thin metal pole 4" or 6" diameter, incorporating a
wheel or rotating ball at the bottom of the pole and maybe a forward/backward hinge one metre from the bottom of the pole?
I would be most grateful for any help or advice no matter how crazy it may seem, thanks.

Jeff_H 12-15-2000 02:57 PM

telescopic keel ?
 
If I understand what you are describing, it probably would not work for a variety of reasons none the least of which is that the position of the keel fore and aft rarely aligns with the position of the mast. That said, boats woith center boards and dagger boards are not that unusual.

To clarify the terms: Centerboards are appendages that can be raised and lowered on or near the centerline of the boat. They can rotate up into a trunk or rotate below the boat. Daggerboards are a type of centerboard that raises vertically or near vertically in a trunk. Swing keels are a type of rotating centerboard that actually contains a substantial portion of the boat''s ballast. They may be housed in a trunk like a Tartan 27 or 34 or hung below the boat like a Catalina 22. In the case of the Tartan 27 or 34 type, they are more frequently referred to as a Keel/ Centerboard (abbreviated k/cb)
A drop keel is a daggerboard that actually contains a substantial portion of the boat''s ballast. These are easier to lock down but can be more easily damaged in a grounding. They generally have better shape than a swing keel and can be more robust, but not always are. One great advantage of a daggerboard is that you can have a large lead bulb that when fully down gives enormous stability and when raised still is more effectve than trying to ballast a full length shallow keel.

While the basic idea of a retractable keel has been around for a long time, few manufacturers build them today as they are more expensive to build and maintain, and, except for the case of a dagger board with a bulb, do not offer as good performance as a fin keel.
Keep thinking-As a person who would like to see dagger boards with bulbs become more common and has designed one which used a stainless steel tube frame that extended becyon the top of the board to take the moment loads- I''ll be glad to kick ideas around you.
Respectfully.
Jeff


innovator 12-15-2000 04:59 PM

telescopic keel ?
 
thank you very much Jeff, it looks to me
like I need to do much more research in this field I shall be back to get a full analysis
of your idea of which I don''t quite understand at this moment
thank you very much
regards ADAM

Quickstep192 01-29-2001 11:15 AM

telescopic keel ?
 
If this is a duplicate, I apologise. A company called ETAP makes what you described. It''s a fin keel with a bulb on the end. It retracts into a fore-aft bulkhead by means of a screw. There''s even a recess in the hull to accept the bulb. They have many other clever innovations as well. Check them out at
www.etapyachting.com

Jeff_H 01-29-2001 03:07 PM

telescopic keel ?
 
That would be a daggerboard with a bulb.
Jeff

oldguy 04-22-2001 09:37 PM

telescopic keel ?
 
Still looking for any information on a Balboa 26 ft. Rudder. It is placed in a pocket in the cockpit. dimentions or pictures or where I might find one would be appreciated


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