Centerboard dinghy with inboard rudder?

[Shalfleet]

Is anyone aware of an un-ballasted centerboard dinghy design that uses an inboard rudder, i.e. not hung on the transom? I would think this is difficult to do as there is little room below the waterline but I do like the look of an uncluttered transom.

Thanks!

[holzbt]

I'm not sure if you are looking for a dinghy tender or a racing/sailing dinghy but you might want to look at the SS class. These are 16' unballasted, gaff rigged, centerboard sloops with inboard rudders. There is a class association somewhere on the east end of Long Island, New York.(possibly West Hampton)The Long Island Maritime Museum built one several years ago and there are still quite a few racing, some frome the 1920's and possibly one or two from the teens. "Early One-Design Sailboats: Grand Old Classes Still Active After Half A Century And More" by Diana Eames Esterly has a chapter about them.

[ 04-24-2002, 12:09 PM: Message edited by: holzbt ]

[Thaddeus J. Van Gilder]

celebrity class is about 20' LOD and uses an inboard rudder, and I seem to remember a moth class boat with an inboard rudder, but I forget where I saw it.

[Bruce Hooke]

As you may have already figured out the difficulty with this arrangement is that while the centerboard or daggerboard can be pulled up out of the way for beaching the rudder cannot without some fairly clever engineering. Also it makes it harder to remove the rudder when you want to, say, put the dinghy on a roofrack...

[johnw]

The Geary 18 (AKA Flattie, a popular Northwest class) has an inboard rudder. It sits in something like a daggerboard case and can be pulled out easily for tailering or just because you don't want pond scum forming on it while the boat sits at the dock. I'd rather have a kick-up rudder for sailing off a beach, but the setup on the Flattie works fine in every other way.

[Dave Williams]

Shalfleet,

Can't really call her a dinghy but I am envolved in working up a design for a 22-24ft. deadrise Sharpie for which I intend to put the rudder in a case forward of the transom. Because of the stern overhang I think I can keep the opening above the waterline to avoid turbulance and keep the tiller more midships.

JohnW, Do you know where I could get any drawings of the rudder case of the Flattie. I am still pondering how to arrange such. Also I notice we live pretty close.

Dave

[ 04-24-2002, 06:19 PM: Message edited by: Dave Williams ]

[Ben Fuller]

On the International Canoe we do this all the time. The way is a rudder trunk. Rudder post goes through a cassette that fits snugly in the trunk. Pull it like you pull a daggerboard. A trunk like this will work nicely in a stern seat of a dingy or through a stern deck.

[johnw]

Dave,

Here's a link to the flattie web site: http://www.flattie.org/association.html Geary designed the boat in the 1920s, so I suspect progress has been made in these types of designs. If your library has a copy of Dixon Kemp's Manual for Yacht and Boat Sailing, you'll find a Linton Hope design from the 19th century that has a removeable inboard rudder. Can't remember the class, but it was an 18' dinghy. I suspect the International Canoes have the most sophisticated design. The flatties I've sailed haven't had the casset, and the system they have is easier to build. If you want to look at one, the Center for Wooden Boats might still have a flattie, though I don't think they have one currently in service in the livery. Basically, the rudder is a steel plate welded to a round shaft, at the head of which is the tiller fitting. You drop it in the well, put in a filler behind the rudder that is like a daggerboard that only goes the depth of the hull, then put a wedge in behind it. Probably a little more drag than the casset would give you, but not a whole lot. Flatties are quite fast.

[ 04-24-2002, 07:35 PM: Message edited by: johnw ]

[Stephen Hutchins]

I'm working on a design just like this right now. It's sixteen ft long, 6 foot beam, decked over double ender with gaff rig. I had not thought of making the rudder retractable, but now I'll be giving it some thought. One way, If you had a very flat run, could be to make the rudder and hull bottom one piece- a cylinder with the diameter equal to the cord width of the rudder, slipped down inside of a tube built between the deck and hull bottom. Okay, a better way would be to build a daggerboard type case between deck and hull, and then cut the dagger board flush with the hull bottom and run a rudder post through it. I think you'll figure out the rest.

[Thad]

Indian Class, 21 ft Alden design racing dory drawn by S.S. Crocker in 1921. Kind of a big dinghy, but not as big as most maxi boats

[johnw]

And of course, Long Island sharpies had inboard rudders and shallow centerboard hulls. The rudder for a 35' sharpie is about 3 ft. long and six inches deep. It can be pulled up as far as the hull, and since the hull is then deeper than the rudder, it's fairly well protected. It can also be lowered about a foot. Makes a sharpie pretty manueverable, because if the helm is put over hard, the ends skim over the water and the boat spins on the centerboard. It's really hard to stall the low-aspect ratio rudder, but because the rudder is blanced, it's not very good for sculling. You carry oars in a sharpie, anyway.

[Shalfleet]

Many thanks for all your responses! The cassette option sounds great and is obviously proven so I would like to learn a little more. I found the following Uffa Fox international canoe design which seems to show a cassette type arrangement above the rudder...anyone got any better pictures?

http://www.interlog.com/~timgitt/hist/uffa_flying_fish.html

[Ben Fuller]

There are several international canoe web sites with far more modern designs. Concept is simple howver, a frame to fit the hole, rudder post goes down through it. Size of the trunk is what you need to get the rudder through it.

http://www.conversedesign.com/IC/canoe.html is the US site and will get you to the rest. On the US site we have posted contents of some of the old class newsletters and I think there was cassette building information in at least one of them. Those newsletters are a great resource on high tech one off small boat building.

[WFK]

Shalfleet;

I was just going through an old Classic Boat Mag. from June 1998 issue 120. In it you'll find just what you're asking about. A sailing skiff with both centerboard as well as an inboard rudder, although it does carry 176 pounds of ballast. It's called a Morgann and is built with plywood and epoxy. Dig up the issue and have a look and if you can't find one, I'd be glad to pass this on to you via snail

[DesignByBird]

Shalfleet, I have a copy of Racing, Cruising & Design, if you need i can scan and forward those pages to you - e mail me (with a week 'cause i'm moving back to Blighty then).

Otherwise another solution has been used on catamarans ; where the whole lazarette hinges / swings up allowing the rudder to be structurally transom hung & retractable, but when the lazarette is down ; then the fairbody run continues aft (and with it the buoyancy).

I believe this is photographed along with other interesting alternatives for shoal draft rudders in Ron White’s (??) excellent 'Cruising Multihulls' (??)

Hanging the rudder below has several advantages ; 1) in certain seas, pitching & heeled conditions the rudder is less likely to aerate, (boat loosing control) which otherwise might mean a shorter (less wetted area) blade can be used.,
2) especially on a cruising boat ; keeping the rudder below waves, greatly reduces the risk of damage / slamming / twisting against its stops,
& 3) the blade is considerably more effective / efficient having a top wing (hull underside)- which hydrodynamically is the equivalent of having a higher aspect ratio blade (again, so it may be possible to reduce the blade length / wetted surface area) see ; Lars Larsson's
'Principles of Yacht Design'

Hope these help, Pete.

[Andrew Craig-Bennett]

Folks, there is a snag to this. As Uffa Fox himself discovered, when he tried it in an International 14, if you bring the rudder inboard you dramatically increase the turning couple and can make the boat far too "hairy".

[Dave Williams]

Andrew,

I don't know what you mean by turning couple but I'd be interested to hear more.

Dave

[N. Scheuer]

The current edition of Messing About In Boats includes an illustrated discussion of a Phil Bolger design that combines an inboard, sharpie-style, balanced rudder with leeboards in a small plywood sailboat. He suggests that horizontal fins extending laterally several inches along the full length of the bottom edge make such a rudder a great deal more efficient.

These sort of shallow "fenced" rudders appear often in Bolger designs.

Moby Nick

[Andrew Craig-Bennett]

John W - the boat in Linton Hope's edition of Dixon Kemp is the RCC "B" Class canoe "Bubble", 16ft x 3ft 6ins, and my father restored her in 1921 and sailed her from London to Cambridge, where he was an undergraduate. He even slept on board for a couple of nights, which amazes me as he was 6ft 2ins tall!

No sliding seat, bronze centreplate, and a very clever reefing system!

One of these days I will build a replica.

Dave Williams - the boat turns too violently in response to small rudder movement - it makes her hard to steer and the rudder also generates a large capsizing moment.

Not really a problem in the size you envisage - more a dinghy thing.

[ 05-16-2002, 11:11 AM: Message edited by: Andrew Craig-Bennett ]

[DesignByBird]

Andrew ; “and the rudder also generates a large capsizing moment” – please enlighten us..

Otherwise ; It is also worth considering the practical application of an in-board rudder, in particular ; the end position of the tiller and the effect on crew weight being that far forward when sailing off the wind !.., a short tiller reduces leverage, and so loads up the weight and compromises the fineness of the helm.., a tiller extension brought back reduces the angle of applied force to such a point where control is noticeably more difficult - Practical (though additionally complicated) ways around this could be the whipstaff / vertical tiller, or else using a quadrant and fitting the tiller remote from the rudder.

Hope this helps .. Pete