Ballasted Centerboard?

[mcm]

I'd like shoal-draft, drawing less than 3', yet in a seaworthy blue-water cruiser.
Is a ballasted centerboard my best option, and can it be simple and practical on a small 8500lbs.disp., 28' sloop?
Can a centerboard carry, lift and lower 1600lbs. of ballast?

[PAR]

I'm currently designing a 26' 7" open water sloop for a client with a shoal requirement. Draft is 32", board up, ballast is 2,400 pounds with a 900 pound centerboard. The remaining 1,500 pounds of ballast are in a stub keel, which houses the majority of the board, so much so that it doesn't intrude into the cabin sole, like most board boats. This does increase the minimum draft, which could have been 20", but the interior options, because the case doesn't divide the cabin in two, is such an attractive argument, that the extra draft isn't as much of a bother to the client.

So yes, you can have a ballasted centerboard, but you'll have design limitations, with the volume the board can comfortably contain and still providing a reasonable foil section. Most find it necessary to divide the ballast into fixed and board mounted. My solution uses 37% of the total ballast in the board, which isn't unusual.

Ballasted boards do expose some interesting design and engineering issues, but not insurmountable.

The design I'm working on is a "in the spirit of" Friendship Sloop, with faithfully reproduced above LWL works, but divided appendages below for some performance gains.

[mcm]

Thanks PAR,

Where can i find scantlings and construction details for such a ballasted centerboard if the stub-keel, centerboard and case are welded steel plate?

I'm looking for off-the-shelf, stock-plans for a blue-water, off-shore, yet shoal-draft, centerboard cruiser modified for 3mm[1/8"] steel plate construction, yet still displacing less than 9,000lbs.

So far all I've come across is the 'Benford 30' in its centerboard configuration.

Do you have any other suggestions.

[Pericles]

http://www.bruceroberts.com/public/HTML/PLANS2.htm

He'll modify if you don't find exactly what you want. Otherwise, build a shoal draft catamaran in epoxy/ply composite and lift the dagger boards. :D

http://boatdesign.net/forums/showthread.php?p=179531#post179531

Pericles

[SeaSpark]

http://www.stadtdesign.com/products/vds409.htm

Their multi chine steel quick assembly method was developed with the amateur boatbuilder in mind. Plans are not the cheapest but very good for the price and they have a good reputation for after sales assistance in the build.

http://www.stadtdesign.com/English/history11.htm

http://www.stadtdesign.com/images/photos/P409_qa2.jpg

Holland has a reputation in steel boat construction as we cut most of the trees in our country (and the surrounding ones) for building wooden boats a long time ago.

Also contact http://www.dickkoopmans.nl/uk/index.htm he may have something for you.

[SeaSpark]

As mentioned in this thread http://www.boatdesign.net/forums/showthread.php?t=20590 28 feet is on the small side for a steel sailboat. Performance will suffer greatly as it is very hard to build steel boat at this size with a low enough displacement compared to its waterline length.

Can you explain why it is impossible to scale up to 30 or maybe 32ft? It would really make a difference in how your boat will behave.

[Pericles]

SeaSpark,

Those were my thoughts as well. Putting it simply, spread the weight of steel steel out to enclose a larger volume and a more successful boat will be the result. Steel construction is best reserved from 50 feet upwards, where its weight is less of a liability.

http://boatdesign.net/forums/showthread.php?t=17985&page=3&highlight=best+size+for+steel+construction

That said, the Stadt Design yacht you posted looks quite useful. Tack and weld rather than stitch and glue:D :D

Pericles

[PAR]

MCM, your requirements seem specific enough to merit a custom or at least a semi custom design. The design I mentioned above has a steel internal element to the keel and the case. Picture an "I" beam inside a wooden sandwich and a plate steel case attached to the top in the center of the boat. The board also has an armature of steel (as does the rudder) with lead in plate form attached, skinned in fabric.

Scantlings and construction details will likely have to be purchased. Study plans will provide you a hint of scantlings and no construction details other then general method employed.

Jay Benford may have other designs that are suitable for your needs as will several others. If you'd like to contact me by email (click on my name) then we could discuss some options.

[mcm]

MCM, your requirements seem specific enough to merit a custom or at least a semi custom design. .

I'm beginning to think your right, because, even though i have no problem finding great steel designs for small cruisers, only the Benford 30 is shoal-draft with centerboard.

Benford, however, likes beamy and heavy boats.

Brent Swain proves that steel doesn't have to be heavy.

Brent Swain's 26' twin-keel cruiser uses 3mm[1/8"] steel plate and displaces only 6700lbs.

Maybe i shouldn't worry so much about getting twin-keels stuck in the mud, because, if i remember, Brent's twin-keeler only draws 3'.

Also, i want a real shallow cockpit, ala' Larry and Lyn Pardee, but instead of their bath-tub/work-table under the cockpit, i would prefer a large sea-bunk under the cockpit.

And, like the Pardees, no inboard engine; i'll mount an outboard.

One picture is worth a thousand words, but i lent my scanner out.

So you're probable right about needing a custom design, but i can't beat Brent Swain's $200 price for his stock-design plans, plus he sells his origami construction book for $50.

Still, when i get my scanner back, i'll send you my conceptual side-profile, end-view, and interior-layout, and maybe you could give an estimate for custom design plans.

The design I mentioned above has a steel internal element to the keel and the case. Picture an "I" beam inside a wooden sandwich.

Ok, i was picturing a welded box-beam for a stub-keel with a plated slot for the centerboard case.

Pericles, and Sea Spark,

Thanks for your suggestions, but i've seen and rejected those designs because they are not shoal-draft centerboarders.

[SeaSpark]

http://www.stadtdesign.com/products/vds409.htm

[SeaSpark]

I do like the origami method, Brent do you have a website apart of the Yahoo group? i can remember it from a couple of years back but can't find it anymore.

If you want a true "blue water cruiser" and insist an having an outboard please put it in a well in front of the rudder and not on the transom or it will be worthless on a lee shore.

Is there a reason you do not want to scale up to 30ft?

[SeaSpark]

I'd like shoal-draft, drawing less than 3', yet in a seaworthy blue-water cruiser.

The sailing characteristics of a steel twin-keeled 26ft boat, even if relatively light, will not be "seaworthy". Imagine outboard failure on a lee shore.

Most Dutch designers have low draft options in their portfolio. Many of the waters here are shallow, hence the leeboards on classic boats.

[Milan]

...looking for….plans for a blue-water, off-shore, yet shoal-draft, centerboard cruiser modified for 3mm[1/8"] steel plate construction, yet still displacing less than 9,000lbs…. any…suggestions.

Do you know Gerd's Yago? http://www.yago-project.com/content/blogcategory/76/58/lang,en/ Why 9.000lbs limit?

but i've seen and rejected those designs because they are not shoal-draft centerboarders.

There is "Vita" version with a shallow keel (95 cm) and centerboard: http://www.stadtdesign.com/products/vds409.htm

I would highly recommend Brent's Swain "origami" building method. Who ever follow this path, aside from plans and book, should buy Alex's DVD's as well. They are excellent, show whole hull, deck, cabin and keels building process in detail.

[mcm]

http://www.stadtdesign.com/products/vds409.htm

SeaSpark, my mistake.

I saw the fin keel on the Vita 30 and did not realize that there was also a centerboard version.

I'm avoiding heavy displacement for the usual reasons: such as needing a smaller rig to push the boat through the water; easier to maneuver; cheaper to build and cheaper to maintain and operate.

[mighetto]

Are we destined to be ruled by a bunch of old white men who are programmed to defend? Lets get this topic into the 21st century. We need only look at Icon, to see that ballasted centerboards are seaworthy. Icon lost the Van Isle 360 only owing to a leg that was canceled.

[BOATMIK]

If you don't know about Mighetto ... consider not responding to his post ... he is waiting to take this thread to only he knows where.

[Pericles]

Having read parts of his contributions, that's good advice. Water world, where's that? If he lives there then, how come these Q & As haven't occurred to him?

http://books.google.com/books?id=Y_3PAWCwSnoC&pg=PA269&lpg=PA269&dq=problems+with+waterworld&source=web&ots=oLrPoHdvYd&sig=UVxmp17OIU8livE-GmCR37l0z0Q#PPA269,M1

Pericles

[Phil Dory]

Wouldn't a heavy centerboard rip out its case in the case of a knockdown, when it would swing back in?

[BOATMIK]

Howdy Mr Dory,

With small boats it usually is not a problem.

With bigger ones it certainly can be - though normally if the case is properly designed the hull attachments are so much stronger than the top of the case that the damage is done higher up - either to the board itself or the case where they make contact.

it actually is quite amazing the forces that a properly designed and built centrecase can absorb with surprisingly little structure.

If the case is glued to both the floor and a bulkhead (either in the middle or the back of the case - plus some sort of web or structural floor at the front they seem to be quite failsafe up to quite big sizes.

But for bigger boats a lockdown mechanism - a pin or screw device or purchase or foam chock - all designed to break in a non serious mode if there is a serious collision can prevent it all falling back in the case.

This should be considered at any rate if there is much weight in the board as it will provide the stability that can help the boat recover from the knockdown.

Best wishes
Michael Storer

[PAR]

The case I've described above has metal floors, fore and aft. The forward end of the case also falls on a bulkhead. Being that the case, internal armature of the keel and centerboard are steel, plus the bulkhead and metal floor locations, I have little worry of the board causing damage in the event of a rough strike or grounding. The worst I'd expect is leading edge damage (which I also have a solution for) and pivot pin damage. Both of these aren't that uncommon in larger centerboard boats. The pin I've spec'd is twice the size necessary for the worst task I'd expect it to tolerate, which hopefully will thwart any bent pin issues.

[Pericles]

When I read of these concerns about the ballasted centre board sliding back into its case, I am reminded of the origins of the beetle and Porsche. The decision to put the engine in the rear led to years of work to make the vehicles handle safely. Development over design is how I have seen it described. Engine in front Herr Porsche!

Thus the discussions about the centre board suggest to me that the sensible step would be to double the hulls for stability and comfort and drop the ballast. :D :D On another thread there is JCD voicing his concerns about righting a catamaran. Based upon the fate of Groupama lll, which floated so well upside down that she preserved the lives of all her crew and was recovered, I'd say that multihulls rule! Although, if she'd been a catamaran she would not have capsized in the first place, :o :o All that grandstanding, flying two hulls, bloody boy racers in their flash new tri. Mutter, mutter, mutter. In my day, we didn't do things like that! Drive around like lunatics. No respect for other road users. Grumble, grumble, grumble. Grouch, grouch, grouch. :P :P

Pericles

[PAR]

Pericle's, multihulls have their place, but most have understandable issues with them. I like mutlihulls and monos, having delivered and sailed many over the years, I have my preferences, but I've never seen a mono with a trap door in it's bottom (just in case). When a design has to look seriously at this particular contrivance, it leaves one to wonder (understandable). How would you feel if the next time you boarded an airliner, they made you put on a parachute (just in case)? Better yet, if Boeing made all of its future airliners with automatic parachute deployment devices. Not that it happens all the time mind you (say the wings have a nasty habit of falling off), but enough to force the designers to take serious consideration in it's regard?

[Pericles]

PAR.

I'm not worried!

I'm a wing walker in my spare time. The times I have put my foot through the doped fabric of the top wing are too numerous to mention. I never wear a parachute and I fallen off eight times already this year.:P :P

I am also economical with the truth. :P :P

Best wishes,

Perry

[Tad]

I've never seen a mono with a trap door in it's bottom (just in case).

Have a look at the various open class monohull race boats, 60's, 40's, mini's, etc. They all have escape hatches in the transom, which is perfectly reasonable. The Volvo 70 rule requires one hatch that is useable and above water when the boat is inverted.

With the growing predilection for modern monohull sailing yachts to lose their ballast keels, I would suggest that escape hatches would be a very good idea. Unfortunately folks might think twice about buying them if they knew what the stability characteristics are when inverted and partially flooded.

We have now seen 100's of production multihulls delivered on their own bottoms from South Africa to the Caribbean, with very few (if any) inversions. I would submit that the escape hatches in their bridge decks (not bottoms) are perhaps leftovers from a previous age? Once again a design feature dictated by market pressure rather than necessity. These new multihulls are purchased by neophytes, not experienced people. The experienced monohullers (like you Par) are telling them they must have an escape hatch......maybe :D

[mcm]

Consider a centerboard in the shape of a quarter arch.

Like a quarter of a round faced clock, where the 4.5 feet of leading edge is like one hand pointing at 7, and the other hand pointing at 10 being the 4.5 foot trailing edge.

Now consider the centerboard to be 1200 lbs. of steel, and the case also welded steel.

How should such a centerboard and case be built?

[Seafarer24]

I've been looking for a nice cat-ketch to go cruising on, and this is one of the boats I've come across:

http://www.sailboatlistings.com/sailimg/m/8608/IMG_1705.jpg (http://www.sailboatlistings.com/cgi-bin/saildata/db.cgi?db=default&uid=default&view_records=1&ID=8608&mh=1)
Click the picture for details.

1985 Herreshoff 31 Cat Ketch. Fiberglass hull built in Miami with optional 3' shoal draft! Honestly, I'd prefer the 4' draft version but the price is right on this boat. There is an Offshore 33 that I'm also considering which has a slightly deeper draft.

The Freedom 28 and 33 would also fit your description, as they have ~3' draft with their centerboards up. (IIRC)

[mcm]

Seafarer24, that Herreshoff is a beauty.

The below the waterline photo showed some sweet underwater lines.

But they didn't describe the centerboard, and i can only assume that, like the hull, it is fiberglass and probable a blade shape rather than steel semi-circle shape.

Am i wrong in thinking that a swinging semi-circle arc shape makes a stronger and more stable board than a swinging blade shape?

How do you feel about that cat-ketch rig in a north-atlantic blow?

[Paulo.AS]

MCM,

I believe your choice of steel is due to many reasons but durability must certainly be one of them. However boats built in steel need to have programmed into their design an allowance for loss in plate thickness due to rust (which will occur no matter how well kept the boat is), which is dictated by scantlings under "add x % mm per decade of boat life" or something like that. And this is why usually steel boats are built in the 50'+ range...
Also the eletrical systems bonding, and zincs number and positioning will have to be carefully thought of.

Cheers

[Gary Baigent]

If you are really serious about centreboaders, light displacement is the way to go. Here are three New Zealand champions from the late 1970's. Note their relatively small rigs and yet these boats were incredibly fast. Ballast was mostly in lead bricks internally with some lead in the board tips; they were daggerboarders actually and not centreboarders.
Farr's One Tonner Jenny H and Whiting's similar sized (approximately 37 foot) Smackwater Jack off Cape Colville - the other being launched (note the easy going low trailer) is Whiting's Half Ton champion Newspaper Taxi, a 30 footer. Now they were real sailing boats and some enlightened person should build them again.