Originally Posted by outbound
Jeff- really like what you did for "your boat" ? What are the mechanics of the lifting keel? ?How did you mitigate possible damage from grounding? Have you thought about the interior lay out? ?Why did you go with that shaped bulb? Would you construct in wood epoxy,GRP, cored GRP, cored exotics, metal or what? Feel like a 4 y.o. with to many questions. sorry
Thank you for the kind words. As Bob points out these are only a first sketch. That said, I have been thinking about many of these same questions as I have been drafting (and some for many years before that).
The lifting keel is one of those items which I have given a lot of thought to.
I will post more about that at some point, and in order to adequately explain how it works I will need to put together some drawings, but as a broad generally, the dagger board can be raised approximately 2 1/2 feet. The trunk tht it rises into is located beneath a fixed portion of the table an terminates at the top of the table except for a pair pf rectangular components which extend to the cabin top.
The daggerboard and bulb would be constucted in two parts. The upper part (the foil above the ballast) is a stainless steel or monel weldment. The lower part is cast lead.
The weldment would designed so that when the board is in the down position, it will be foil shaped from the top of the lead to a few inches into the trunk. Within the weldment are two rectanglar tubes. These extend from the bottom of the welded foil portion where its meets the lead ballast, through the foil and extend approaximately 4 feet above the foil. They an integral part of the structure of the foil, and they serve to transfer the moment laterally. These tubes slide in slightly larger metal tubes which extend from the deck to the top of the centerboard trunk and which are braced by the main bulkhead forward, and by a large knee aft that is intergral with the dinette settee.
There is also a heavy center spine plate in the weldment, that is oriented fore and aft, and which extends from the leading edge of the daggerboard to its trailing edge. That plate rides on upper and lower- fore and aft rollers mounted within the trunk and which maintain the fore and aft position of the daggerboard. Those rollers are through bolted through large blocks of high density urethane. The urethane blocks are intended to act as shock absorbers in a grounding.
This assembly requires a fairly large rectangular opening. in the bottom for installation and maintenance. The (exposed bottom of the hull) fairing for that opening would be removable heavy neoprene membrane with just a slit in the shape of the board so that the board can ride and fall through it. The fairing would not be waterproof. This is similar to some smaller saildrive ports.
The board would be lifted by a reel winch with a cable run to sheaves that are attached within the end of of the guide tube and sliding tubes. The reel winch would be mounted on the guide tube to isolate the compressive loads. the reel winch would be driven by a hydraulic motor and would be driven by an engine driven hydraulic pump. The thinking is that you would never sail the boat with the board partially raised, and so, by definition would have the engine running if the board is being raised. There would also be a back-up geared drive on the reel winch which would take a winch handle for emergencies or when a full back is sailing with you and gets bored entering a harbor.
If we really wanted to guild the lily, I had also looked at a rack and ratchet (similar to the original design for an elevator emergency brake) that would automatically engage when the load was taken off the cables and lock the board down. Os when fully lowed the cable would slack enough that ratchet pawl would engage the rack, or in a knock down, if the board tried to slide into the trunk cable would slacken and the ratchet would also engage locking the daggerboard where it is. Otherwise, the cheap solution is that there would be a simple pin inserted in the guide tubes to lock it down or up.
What I don't like about this is that there is no bilge sump.
The bulb keel shape while schematic in nature was intended to lower the vertical center of gravity, avoid having a bulb extend beyond the leading edge of the keel to avoid catching things, minimze wetted surface, centering the lead weight beneath the main lifting tube, and acting as an end plate.
We have not gotten around to building materials, but to some extent it depends on whether we think of this as a one off or a production design (now there is a laugh). If this was a one off, and my boat, I would probably do cold molded western red cedar veneers over bed and cove strip planking with vinylester-kevlar/glass outer sheathing laminates for puncture resistance and epoxy glass interior for sealing purposes. If production, I personally would want a vinylester-kevlar/glass laminate, cored with high density foam to the waterline and with uncored glass with tightly spaced internal framing below the waterline.
I have not discussed this with Bob, and so Bob may have much better ideas on all of this.
Needless to say, this is not an inexpensive boat. Or perhaps seen from my perspective, this is the cheapest possible boat...The one that no one actually constructs.