sail area vs ballast

Hmmm. First off, I should have mentioned that you need to make sure the boat is strong enough before ballasting it. This may mean beefing up the hull laminate, as you're doing, and adding structural floors in the keel and bilge. Once you do this you can use internal ballast, and here's a company that specializes in it: www.ballasttech.com

I think it'd be a sin to cut off that keel. But on the issue of making your boat a cruiser there are some interesting precidents for it, like the famous motorsailor Blue Leopard designed by Laurent Giles:
www.harbormodels.com/BlueLeopard.html
www.laurentgiles.co.uk
There is also the precident of mini 12s for sitting down in the hull of this type of boat:
www.gaviayachts.com
www.gaviayachts.com/history.htm
www.sailingtexas.com/sillusionmini12a.html
www.nsc.ca/ablesail/NSC Mini12 syndicates.htm

If you plan to sit belowdeck you coud give your boat a pilothouse with a big sliding hatch that you can stick your head out of, or not. With the hatch closed the deck should be watertight for safety. The trick would be to run your sail controls in a way trhat would allow you to sail from belowdecks while maintaining the deck's watertight integrity. You'd want to be able to see out the pilothouse windows with the hatch closed, of course. You'd then have a boat that could be sailed longer into the autumn than most.... pretty cool if you ask me.

 

we're on the same page, stephen. if we can justify keeping the keel i'm all for it, but 36" of draft seems like a lot where i sail.

thanks for the references. i'll check em out.

 

to clarify what we're dealing with, here is a shot of the interior [the boat is upside down]. it shows the c-flex and the frames with spacers between. the spacers don't penetrate the frames. i'm not yet sure what was used as a keel.

 

Where to you sail, Tohbi? If I knew your location I could probably recommend someone nearby to advise you concerning the structure. When Olin Stephens spoke to us at The Landing School we were waiting for him to talk about hull shape. Instead he began by saying, "The most important thing in any design project is to be sure it's strong enough, the second is to be sure it's stable enough, and the third is that it's controllable. Everything else is trivial by comparison." I feel strongly that there needs to be more bottom structure in your boat, probably in the form of transverse "floors", but sequencially it might be advisable to lay glass across the inside before installing the floors. It might be possible to make a lightweight filler material by mixing MicroLite (Gougeon Bros) with a lightweight resin, or by using CoreMat or a similar product, or perhaps even with Bondo, to create a smooth surface on the inside before laying the glass. Someone needs to do their homework and think this through.

Your boat should suit your needs and environment. If you're determined to go the centerboard route I'd advise you to check with the Ted Hood Design Group and ask if you can have a look at some of their past work for inspiration. They specialize in combining centerboards with deep V section hulls.
www.thco.com/design/design_stage.html
If they're not forthcoming there are other possible sources, so don't let them talk you into paying too much. You should be willing to write a check for $100, and maybe $200 for a full set of relevant construction details for board, trunk, supporting structure and ballast. Be aware that building a centerboard trunk tends to be labor intensive, but if you're going to do it it's important to do it well.

If you'll remove your keel carefully I'd pay UPS to ship it to me rather than see it trashed.

I'm guessing the rig you'll want will be similar to that of a Yngling - www.yngling.org
There may be Yngling rigs and sails on the market immediately following the 2004 Olympics, and maybe before when contenders are eliminated at their national Olympic trials. You might be able to simplify the stability testing process by making it relative. If you fill a 55 gallon drum 2 feet off centerline on both your boat and a Yngling, how many degrees does each heel? They'd need to be configured similarly. If measuring your boat without its rig, you should measure the Yngling without its rig, too. You could try the same thing with an O'Day Mariner or Rhodes 19 - www.rhodes19.org

If you were to give your hull a flush deck could you sit up comfortably inside it? Could you still if you gave it 8" floors? Your deck needs to take some compression loading, but if you don't need a cockpit you could reinforce the deck on either side of the mast and hatch opening to do this. Then you could put polycarbonate (Lexan) windows along the sheer in both hull and deck. When heeled, this is what you could see out of. When upright your head could be in a clear "bubble" as seen on some past round-the-world singlehanders, or could protrude through the hatch. I know I recommended a sliding hatch before, but I thing you could use a Bowmar or Lewmar deck hatch, and I'd favor a round one as seen on the foredecks of many raceboats today. If you don't like the idea of a Lexan sheer or you need a little more headroom you could use a bupple neer the sheer on either side of the deck, or you could go back to the concept of a pilothouse. Consider, though, that the pilothouse should be wide enough for you to have good visibility when the boat is heeled.

 

stephen, thanks for the creative ideas and references. and thanks to everyone who is contributing to this discussion.

i live in a small town in southern arizona. i sail the local lakes, n. sea of cortez and the pacific off san diego. local lakes are shallow and the north end of sea of cortez dries out, so this design of hull is not optimum to deal with those features. i've received good advice about building "legs" for the drying out situation. shallow draft is more problematic.

we don't want a centerboard trunk; it's just too invasive and would mean cutting frames. the frames are 9" apart and a daggerboard could be inserted between them. this would make the daggerboard approx 7 1/2" wide. cutting one frame could double that width.

alternatively, a swing keel could be operated by a cable and mounted in the stub of the ballast keel.

or we can use the present configuration, wing and all, and just reduce the depth of the keel. this would be ideal if it would work.

or we can leave it like it is, probably the best solution for handling but it doesn't solve the deep draft problem. this is a major issue because it will determine what we do with the rest of the design.

i'm taking off most of the outside bondo. two or three layers of epoxy glass will be added to the outside of the hull. i intend to add fillets to the frames on the inside. do you think this will provide enough structural strength?

 

The purpose of deep transverse floors is to distribute forces from the keel and the ballast into the hull. Just forward of, just aft of, and over your keel (or just forward, just aft, and on either side of of your daggarboard trunk) there should probably be a floor at each frame. If the ballast is in the keel there should probably be a bar (or something) extending from each floor down into the ballast, perhaps bending 180 deg inside the ballast and coming up to the adjacent floor. It should probably be made of the same metal as the frames, and should be galvanically compatable with the ballast material and any bolts used. Before these are installed, any core material should be removed from the hull/keel juncture and the skin should be reinforced inside and out if possible in this region. It would also be good to run unidirectional reinforcement from the keel to where your chainplates will be and to add more unis at 45/45 diagonals from before the mast to aft the keel (incl. the area of the chainplates) for tortional strength. Unless you plan to have a bilge pump intake between each floor each will need to have a "limber hole" or space above the inside of the hull skin at centerline. I'd also propose using intercostal spacers between floors at centerline to form a longitudinal keel (I'm referring here to a longitudinal structural element, not the external fin keel). I see in the photo a longitudinal keel exists; I'm proposing building it up.

Of the draft solutions you proposed I like reducing your keel span and keeping a portion of what exists best. I recommend cutting away the top part of the keel and reattaching the lower part to the hull so the wings remain. The reinforcenents I just mentioned would be part of reattaching it.

A further note on the stability comparison notion, and rigs: If you have a chance to take measurements on boats of similar size you should take note of the distance from centerline to the shroud chainplates, and check how far outboard you're able to locate your chainplates.

I also have a thought related to interior comfort and mobility in a non-standing-headroom environment. I represent a company, www.surehands.com, that makes ceiling track and slides from which you can suspend a seat. If you did this inside your boat you could slide fore-and-aft in a sitting position rather than having to crawl. You could either have a track on centerline or you could have two tracks running on each side of a centerline hatch. The latter arrangement would allow you to clip onto the windward track when heeled or to suspend yourself from both tracks when upright. Let me know if you're interested and I'll quote you a price.

If you're in the southwest Bruce Nelson would be a logical person to speak to. Unfortunately his web site, www.nelson-marek.com, seems to be very short on information. Here are some basics:

Nelson/Marek Yacht Design
Address 2820 Canon Street, San Diego, 92106 California, USA
Tel +1 619 224 6347
Fax +1 619 224 5192
Number of employees 4
Architects Bruce Nelson, Greg Stewart, Nathaniel Fennell
Specialization Sail - racing and cruising

You might try to interest one of the junior staff at Morrelli-Melvin or Reichel-Pugh in your project (depending on how busy they are) or in recommending someone in your area.
www.morrellimelvin.com/whoarewe.html
www.reichel-pugh.com

You might check with Leif Beiley and see if he'll take an interest without charging big bucks.
www.bravurayachts.com/company_profile.htm

Perhaps one of these will be useful:
www.saic.com/acup/history.html
www.waterplane.com
www.andrewsyacht.com
www.boatmall.com/Designers/0685.htm
www.yellowpagessandiego.com/business/24618/5720/Naval-Architects.html

Jim Antrim is located well north of you, but would make quick work of any structural calculation.
www.antrimdesign.com

Talk with area sailmakers to see if there's anyone else who might be helpful, and so you can eventually select a sailmaker who'll take a strong interest in your project.

 

if we retain the wing, a metal one will have to be welded [the present one is vestigal]. it can be made to fit inside and run the length of the keel. metal straps can be welded to this "floor" and, passing through the ballast, they can attach to the frames above them. your method of using the lower part of the present keel seems a good one.

the ballast can be left loose until the boat is sailed. if it doesn't point well, a daggerboard or trim tab can be added. this doesn't answer the stability question, however. what will reducing the ballast draft do to righting moment?

i was planning to attach the chainplates to a frame and run them through the deck inboard of the sheer. how does this sound?

your idea of a swing chair is novel [maybe we can make it a loveseat ]. i haven't given too much thought to the interior except to wonder about what to do for portholes?

 

I'm afraid I'm not following your first two sentances, T (not that my clairity was necessarily better). By "wings" I meant the winglets on the fin keel.... is that what you mean?

If you keep the bottom part of the keel with the winglets I think you'll still have enough keel area without having to add a lifting appendage. A daggarbord or trim tab will not add to your stability. Stability is mainly dependent on waterline beam and center of gravity. Since you don't have much waterline beam it's important that your boat have as low a center of gravity as possible.

Your plan for the chainplates sounds fine, but if you might use, say, a Yngling rig, and you find that your stability is comparable to a Yngling, you'll still need to know if your chainplate offset from centerline is comparable to a Yngling to know if the same mast section and rigging will work.

Please note the addition to my previous post. Again, great project!

 

thanks for all the references, stephen.

yes, winglets or wings. i thought the metal could be welded in a roughly "T" shape, inverted and made as strong as possible with straps to attach to the frames.

the hull of the yingling looked [to me] like it might have more initial stability than this one. i'm thinking this boat will be very tender and we'll have to be careful to keep weight low. reducing the keel ballast and adding a cabin are counterproductive in this regard.

i'm thinking as low a cabin as possible. your bubble idea would be fun to sail but i'm envisioning something a bit more traditional. the cabin can be hinged in front with cloth side curtains that keep it enclosed when raised at anchor. keeping it light in weight will be important too.

i need to read through the great advice i've received on this forum. there are some very knowledgeable people participating. thanks

 

The reason I'm not as pessimistic as Paul is that people really enjoy the 13'-14' mini 12s (see links in a previous post). And as I've suggested, this boat's size and proportions are not far removed from those of a Yngling, now an Olympic class one-design. A beefy ring frame can take the place of a bulkhead at the mast, and the mast could be deck stepped if necessary. I agree, however, that the hull and connective structure will need to be reinforced, and the deck strength will need to be adequate. In the worst case the model could be used as a plug for a female mold, and Tohbi could build a new hull using that mold. My hope where Bruce Nelson is concerned is that he may already have enough information about this model to give an informed opinion on this matter, since he worked with these models and this may well be his design. If it's not then he should know who has the lines drawing/hull def file. If he's too busy to work on it, or too expensive, he should at least be able to provide information on the boat to someone less expensive, like Leif Beiley or Jerry Selness, to recommend Tohbi approach one of his '87 America's Cup colleagues who is less expensive or busy (whether that be Chance, Pedrick, Marshall, Scragg, or someone else), or to provide the information to a naval architecture student at the University of Michigan (his alma mater) or elsewhere.

On the subject of plugs: I was thinking the hull, keel, and winglets were comprised of one contiguous skin. If that's not the case, Tohbi, you might be better off removing the keel and shipping it to Duro Keels <www.iwm.com.mx/servicios/durokeels> to be used as a plug so they can make a casting. Some design work needs to be done in advance of this, however, first regarding strength and then a weight study. I advise you to get some advice - from a naval architecture student if you can't find affordable advice from an established professional.

 

i appreciate paul's observations about the difficulties of using this model, and i agree with stephen that an "archaic" [i prefer "classic"] design can have potential. i just read of a 1905 trans-atlantic race in which the american winner set a record that wasn't broken until 1980, and the 12-meter boats are similar to a number of old classics.

paul's comments about interior space are especially interesting and he makes a number of good points that will bear careful consideration. the focus on structural strength is a central issue.

this boat has 28 plywood frames and a substantial plywood deck. by a "ring frame" i guess you mean one that completes the "circle." it doesn't have those except for the bulkheads. i've been concerned more about longitudinal support, then i realized that c-flex has fiberglass rods in it running the length of the boat. they're tiny but there's a lot of 'em. i will lay extra epoxy cloth along the length of the keel, as well as reinforcing the ballast keel.

the intention is to take what is here and add enough epoxy glass to, effectively, develop a monocoque type skin, marrying the entire structure into one unit. the form is here. the question is how to reinforce it? one advantge is that weight isn't an issue; we could turn her into an icebreaker and still need ballast. cost is another matter.

well, that's not the only question. obviously, the boat has to be safe and perform well. we know this design is fast, weatherly, and seakindly. it is also a very wet ride and, if open, could swamp easily. stephen's suggestion to make it relatively watertight is essential, i think.

paul estimated 2500 lbs gross weight. my amateur figures came out around 2000 lbs. either figure is a lot for this size boat and makes it difficult to provide flotation, so the safety factor is a very real consideration.

i have a couple of architects interested in the project and one is crunching some numbers for me. i'm looking at this boat, more and more, as a big canoe with ballast. probably, if we go ahead with the glass work, we'll put it in the lake with a trolling motor and do our own "tank" testing to see if we want to proceed.

having a ballast keel cast would be tres cool but i doubt i could afford it. i was planning on having the wing and keel floor welded and loading my own lead on top of it.

this dialogue is terrific and what the forum is all about. it represents the thinking "long and hard" that paul suggests. [btw, i already own a venture 21]

 

Correction

In my previous post I meant to say 2200, not 2500. That was based on a guesstimate of what the original full size design was intended to weigh. The 2500 included a crew of 2.

My first instinct was to stay out of this thread. I should have followed that. I've deleted my previous post.

Good luck.

 

wing & weather

i thought you brought up some valid considerations...

i read an opinion that a wing keel is only good for cruising, that it slows a boat more than a blade keel when the weather gets up and the boat begins pitching. anyone heard this?

 

make that only good for "racing," not cruising.

 

Hi Tohbi

Despite my scepticism, I'll follow through on this!

The lead ballast can be cast at home, saving you a lot of money. The lead has a small quantity of antimony added to give it a little more strength and hardness, but if you are still concerned then you can install stainless or bronze rods into the moulding which remain a part of the ballast. You would use the keel as the plug for making a sand box mould using casting sand. Install the rods (if used) then once the lead is molten, pour in one go. Make sure no moisture is present (or BANG spatter spatter!) and leave it to cool for a long time! Many people casting their own keels bury the mould in the ground before casting. I should add my own disclaimer to this and say that the operation, whilst feasible and often succesfully and safely performed, is inherently dangerous. The information here is a VERY basic outline, written by an amateur, and doesnt contain relevant safety information or more detailed procedures. It also may contain errors. If you want to do this, then find an independent metal worker who can advise you and help you do this safely!!! :!:

If you must shorten the old keel, you might consider adding a forward fin to maximum draft and/or tinkering with the centre of effort in the sails and the centre of lateral resistance of the hull so that the rudder shares part of the lifting requirements sailing upwind. The latter is similar to the configuration on the most successful 5.5 metres designed by Seb Schmidt. Otherwise, how about a hollow fin with lifting daggerboard complete with winged bulb on the bottom of the daggerboard? Then the c of g can be as low as your sailing depth allows, and if you need to run shallower then you'll just have to reduce sail earlier. The daggerboard could also be retracted for motoring.

Keep working the weight and stability calculations, but remember that every gram you add in reinforcement, cabin amenities, motor and battery (heavy) will have to come out of the ballast for the boat to sit on her lines.

About the mast section - you will need a mast with an unusually high transverse moment of inertia. With a narrow shroud base on such a big rig, the rigging tensions should be high and the mast stronger than usual in the athwartships dimension. The 2.4 metres (and other metre boats) use a special mast section with this in mind, and I wonder if you might find it difficult to find a mast with these properties. If you find a standard mast section that is stiff enough sideways, it will probably be too stiff fore and aft as this hull will need a spar with a proportionately higher side to longitudinal stiffness ration than a hull with a wider shroud base. It will also be heavier than an average spar. You could make your own carbon/wood spar with the required properties.

The increased rig tension on the stays will need a substantail mast step and a longitudinal stiffening system of some sort to stop the boat bending under the forces of rig and keel. Stephen's comments about a ring fram in the mast area is very true. Add ring frames under the mainsheet and anywhere else you identify a transverse load on the hull.

I like the idea of a low profile cabin top - you could design it as a scale model of a larger vessel, which would be interesting conceptually and nice to look at too!

If this is to succeed, I think lightness and simplicity in the whole project will be the key. I still think that with all your mods it would be cheaper to start fresh and build around suitable and cheap secondhand parts, as I suspect you may have problems sourcing the more specialist mast and rigging cheaply. A new boat would be lighter (ergo cheaper as everything would be smaller and less loaded) and could be purpose designed around, say, a 505 rig, which should be easy and cheap to find secondhand. I currently have an FD rig and sails I am considering using on a small keelboat in this very way. Nevertheless, Good Luck!!!