Moving ballast

[SchoonerSaraB]

Been kicking around an idea. In the not too distant future I will have to make a decision on wether to rebuild or move on to a different boat. Wife would like more room below for extended cruise ie: possible 5-10 year cruise.But because of shallow draft and internal ballast standing headroom is about 5'7''.If I could make her an external ballast, I could lower the cabin sole gaining head room ,increase initial stability not to mention it would make cleaning the bilge much easier.I realise there would be structual modifications needed but I am talking a complete rebuild to begin with. Also at 38' with a 10'beam shes framed 8" on center and weighs approximately 14 ton she is built like a tank. So, any one out there whos had any kind of experience along these lines? People have said why not just get another boat,but you know the story,the devil you know.....

[JimD]

SSaraB, I haven't any experience with what you're proposing, only know what I read about such questions but just to kick things off...What is the design, construction method? what is the internal ballast made of? How much does it (ballast) weigh? ie if its concrete/scrap iron could you get it out and replace it with lead which takes up far less room but still leave it inside? how integral is the ballast as part of the boat? how sound and well built is she? What's the keel design and material, fin or full keeled? Hanging the ballast outside with bolts may mean serious modifications to the keel, adding deadwood, etc. Maybe you need a real naval architect or at very least a very competent surveyor to get you started. If you can provide more specific info you might get some responses.
regards and good luck
jimd

[mmd]

IMHO, and without seeing the actual boat or accurate structural drawings, I would venture that this is a "do-able" modification, but with some serious modifications involved. The stresses imparted by a large lump of lead hanging on the outside of the hull are considerable, and a boat originally designed for internal ballast will not likely have the backbone to carry it, especially for long-term, blue-water cruising. You will most likely have to beef up the keel, floors, and maybe reinforce the frames in way of the ballast keel. This is doubly so if you are considering a fin-type ballast keel as opposed to a long, shallow ballast keel, as the stresses inparted will be both magnified and concentrated. Also, be aware that changing the C of G and distribution of weights in the hull will alter the motion characteristics of the boat.

An example of the latter is the Bluenose Class sloop. These were first built as plank-on-frame boats, but in the late sixties a company began producing them in FRP. As the hull was lighter, they increased the mass of the ballast keel, but kept the shape of the hull exactly the same to stay within class. You'd figure that with a higher ballast/displacement ratio and lower C of G that the boat would be faster, right? Wrong. The newer FRP boats are regularly trounced by the old woodies. There is now a small renaissance in building the boats in wood. (Yea! :D )

Definitely have the boat surveyed by an experienced wood-boat surveyor, and I would suggest having the keel size, bolt size & number, and structural mods designed or vetted by a NA.

[SchoonerSaraB]

Well, I should have been a little more informative when posting. SaraB. is a tancook schooner plank on frame with lead pigs as internal ballast. She is full keeled,round bilged forward with a turn towards the stern. I've seen another set of plans for the same design only 28' with external ballast and the scantlings are are pretty much similiar. A son of a friend is a naval architect who knows the boat well. I would probably ask him to figure the particulars. Guess I just wanted some imput from fellow forumites.Am I crazy for contemplating this or is this a do-able thing.I don't know the weight of the ballast but i would hazard a guess at about 6-7 thousand lbs.I know every time I move it around I think I am crazy. At 4'9" draft I could easily afford an increase,and not be to concerned.

[Bob Cleek]

No, it isn't do-able. Unless, of course, you want to maybe install a new keel and all new floors. Doubtful she's engineered to distribute the stresses in the localized fashion required for an outside ballast keel. Sitting down below is a much easier solution. As LFH once noted, how often are you standing up down there anyway?

[mmd]

Bob, I've been hanging about in here for about three years now and I think that this is the first time I've disagreed with one of your posts. :( I hope that you'll not take offense, but here goes nuthin':

I certainly agree that it would be no small task, and that it would require major modifications to the backbone structure. I believe that I alluded to that in my previous post. I am even more firm in my conviction that it is "do-able" now that I know it is a Tancook schooner, as I am very familiar with these boats. Tancook Island is about twenty miles from my home and I have studied these boats for many years. The structure of the vessel and it's long straight keel would enable a lengthy shallow lead keel to be installed. A sixteen-foot length about 8" wide by 8" deep would yield about 4700 lbs of ballast with the remainder as ingots fitted internally for trimming. New floors would have to be fitted to better distribute the load, possibly a keelson added to stiffen the existing keel, and I would consider sistering every second frame over the length of the ballast keel for strength. The addition of the external ballast would stress the keel by about 300 lbs per foot, which is not exorbitant, and would create a tensile stress in the keelbolts of about 4500 lbs/in^2 which is again not too scary.

There are definite down-sides to the project, though. We are talking about a major, costly rebuild of one of the most difficult areas of a boat to rebuild, not to mention that we are considering essentially butchering a classic hull form (presuming it is a faithfull reproduction of a traditional Tancook Schooner). There also may not be much gain in headroom, what with adding a keelson and beefing up the floors.

Bob, at risk of tugging too strongly on Superman's cape ;) , I'll concede the argument on terms of cost, labour, and complexity, and the moral propriety of altering a traditional hullform, but stick to my guns in terms of structural feasability.

By the way, for all you fans of Tancook boats, the Fisheries Museum of the Atlantic in Lunenburg is building a new Tancook Whaler. I'll post pics when I visit in the near future.

[Ross Faneuf]

As I recall from my reading of the recent book on Joel White, he converted his Northern Crown from inside to outside ballast - a boat much the same size as this one. Corrections to my memory welcome.