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Old 07-09-2008
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Drop keel from wood to metal??

HI...new to Forum so hope I am in correct place.I have just aquired a beautiful Mcnaulty 12ft gaffer.......for her size she caries a great deal of sail and with a wooden drop keel and no ballast this makes for a very "on the edge" boat.We have sailed in the past with ballasted boats and metal drop keels without incident.
This boat makes my wife very nervous,not a good situation if you wish to keep both ladies in your life together.

I feel with a bit more ballast she would be much more stable,loss of speed we are not concerned with.

Would it be practical to change the wooden drop down keel for a metal one?
if so what material would be suggested?

This would be the most pratical way of adding ballast,at the most affective point.

Thanks for your time
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Old 07-09-2008
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Is this drop keel a centerboard or dagger board? In the case of a daggerboard, it would be relatively simple to make a ballasted replacement board of fiberglass and lead or steel. If it is a centerboard, it gets a bit more complicated, since the centerboard trunk and centerboard lifting/locking mechanisms would all have to be reworked to handle the heavier board more likely than not. A drop keel (usually referred to as a lifting keel) would really depend on the design.

btw, I seriously doubt that this boat, a 12' gaffer, uses anything like a real lifting keel. It is probably a daggerboard boat. It would help if you would learn the proper terminology for the parts of a boat, since that would make it easier to understand you. I'd also highly recommend that you read the post in my signature, as it will help you get more out of your time on sailnet.

Be aware that adding any significant amount of ballast to the "drop keel" will cause the boat to sit lower in the water, may make the boat more likely to sink and add additional stress to the rigging—and possibly cause the rigging to fail under certan conditions.

If you really have a problem with the tippiness of the design, I'd highly recommend you look at other boats. Most small sailng dinghies are going to be relatively unstable.
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Old 07-09-2008
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SD the gentleman is British. Drop keel may actually be the proper name for a daggerboard over there since I have seen that term used by Brits in the past.

As to the question at hand, you probably could change to a ballasted dagger board or a metal ballasted hinged centerboard, but I doubt that it would make a noticeable difference. If you were to take that next step you would probably want to cast a lead tip and build a composite board with a glass and wood upper board. This will have to rpoperly engineered and constructed and may yield tangible results, but not big ones. Simply building a CB around a steel plate or bronze plate will have minimal impact on sailing stability on a boat the size that you are discussing. I have seen lead shoes bolted to the centerline of the hullks of small, early 20th century sailing dinghies again with some minimal effect on stability.

Jeff
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I'd love to see some pictures of this boat as well as of the drop keel current. I can imagine that Jeff's second suggestion of laying up a new keel with a lead casting at the lower edge might provide just the increase in initial stability to ease your wife's concerns. Please post some photos and we'll get "on the case" with some ideas.

And welcome on board sailnet!
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Old 07-09-2008
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Here's an idea.
Take your wooden drop keel out. Measure a square of about 6 inches by 6 inches square as low down in your board as you can and cut it out. Fasten a temporary bottom to the hole with tin or sheet metal. Get (buy, get from used tire weights etc..) enough lead to melt into a 6 x 6 x 1 inch square, melt the lead in a coffee can (or frying pan on a outdoor bar-b-que or other gas/propane flame and poor the lead into the hole. Put enough in so it is a tight fit - yes it will char the wood edges a little bit but that's good as it will make a tight fit. Overflow the lead just enough so that when it cools you can hammer a flange into it over the wood.
Lead weighs about 64 pounds per square foot (12 inches square x 1 inch thick). Naturally, the size of the lead filling can go larger if you would like more weight.

Once it's cool you can shape it better for smoothness then coat the entire board with 3 coats of epoxy.
At 6x6x1 inches (half a square foot) You'll have added about 32 lbs of ballast down low where it counts.
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Drop keel/dagger board

many thanks for all suggestions.

I might add I have spent 24yrs RN and over 20yrs sailing 20ft Luggers and gaffers.

This particular boat is definitely a hinged,levered drop keel and NOT a dagger board.....have to say that even us Brits do name dagger boards and drop keels as do you guys over the pond.

I take on board the possible strengthening that may be required to substitute metal for wood,and that was one of my concerns.....I do like the lead idea,as for getting a another boat,this one is a dream so if like any lady she feels a bit skittish at times thats fine by me.

photos I can supply,if you have the time...at the moment the British Summer has deteriorated into an Indian monsoon with constant SW gales,so that at present to totally rig and present the boat is a bit dodogy..what I will attempt is to upload some photos of her as he sits on the trailer
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caskin,
Chuck's idea is a good one although I might be inclined to just make up a whole new keel for as small as it is. And I'd think that you'd want to cast some bolts into the molten lead to attach the flange that Chuck mentions.

That boat is a little beauty. I'm not at all sure that, if I owned her, I'd be so solicitous of my wife. I really shouldn't be considering which is more easily replaced, but....

Another thought occurs. If you do modify this drop keel you may well want to give some attention to the pivot point. It will have an increased load placed upon it and the time to double it up is before wear occurs. And, if not already fitted, you might give some thought to finding a way of securing the keel in the lowered position-perhaps a hole with pin through the keel trunk. With the added weight to the end of your keel, were you to capsize, the keel is going to slam into the keel trunk with much more inertia/force than it would as presently configured, creating damage that could be severe.
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Very pretty boat, I can see why you want both ladies in your life...

By the looks it is a pivoting centerboard, rather than a daggerboard as JeffH called it. How large is the entire board? If it isn't too large, you could possibly make a composite replacement that had an "L-shaped" section of metal ballast cast in or bolted to it. The "L" would run along the forward edge and the bottom when the board was deployed.

By making the weighted section an "L-shape", this would help the "weighted" board give the boat some more stability when the board was retracted as well as when it was lowered, as well as help distribute the weight of the ballast a bit more evenly fore and aft when the board was up. You'd probably need to reinforce or re-build the pivot point area with a larger bolt or pivot hinge pin to accommodate the additional stresses. Putting in a positive locking mechanism to hold the board in the down position in a capsize would probably be an excellent idea, as Sway has pointed out.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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May I start by saying a big thank you to you all for being so responsive and helpful.
I have to say that when I was alongside In Newport VG and Mayport Fl
that the welcome we had then was second to none and that was back in 1976 Bicentennial.
Even so It makes a change to come onto a Forum as a newbie yet instantly get genuine advice..
All the ideas and comments have been both professional and helpful,as although I have been around both large and small boats all my life,when it comes to design/stress/etc I hit a brick wall.
I,m thinking that I may well incorporate Sailingdogs final idea,as that may also prevent the over inertia affect during capsize as suggested by Sailaway 21.
The present pivot bolt is already 3/4inch stainless with double external reinforcing sections which I would have thought capable of accepting sailingdogs modification?
Locking pin again a good idea and not difficult to incorporate......all being well as soon as weather allows I will strip out drop keel/board,perhaps if you will allow me to,get back to you with final measurements and also finished mod...
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Look forward to seeing it.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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