And so to the aesthetics

Imagine this at 34 feet and each hull 4’6″ wide – this is the classic cat shape and there are reasons one is forced back to it each time.   In a seagoing craft, there needs to be more sweeping sheer and higher stemposts.

OK, for those who’ve been following this:

Hulls and platform

34 feet by 21’6″ [each hull 4’6″ beam and 11′ x 11′ platform between them amidships] because that allows, in the hulls:

1. 4′ long bulkhead at the bow and 3′ at the stern;

2. 8′ long for’ard compartment, with 6’2″ headroom at one end [washroom/head in port and forward galley in stbd hulls];

3. 3′ long x 4′ wide wet area [also the access hatch], from which for’ard and midship compartments are accessed [same in both hulls];

You begin to get the hull shape from Yellow Pages – note very little rocker [there’ll be some in the seagoing version] but some nice sheer curvature and an almost cheeky bow – I liken this to a meat cleaver.

4. 9′ long midship compartment with 6’2″ headroom at the for’ard end, reducing to 4’8″ [same in both hulls] – these are the two cabins and include dresser and small hanging space;

5. 6′ long cockpit x 4′ wide, not accessible from any other compartment [same in both hulls] but enclosed with hard dodger and dacron and perspex panels.

Crew of 2 only but at a pinch, children can sleep in the galley area.


Ketch with 3 headsails – yankee, jib and staysail [all 91 sq ft], gaff main of 198 sq ft, gaff mizzen of 170 sq ft.

You can see the motif in this lifeboat.


1. Well aware that 3 headsails mean the yankee must be sheeted out wide and it’s only for a 180 degree downwind angle, the jib is for 240 degrees [between a broad and tight reach, not unlike a gennaker] and the staysail for all points of sailing – the front two roller furl and the staysail does too when released from the boom [not intended except in bare pole conditions]. So no reefing required for’ard of the foremast and no need to go for’ard unless something jams [there are nets and safety line]. All action [including access to masts] from the platform and cockpits;

Again you get the idea of the lines, with the vertical stempost, a little rounded where bow meets keel.

2. All boomed sails have a double sheet system, rather than traveller, all leading to cockpit[s] – cats lend themselves to this arrangement;

3. Aft mast is slightly more upright and is intended as a driving, not a lifting sail – hence the 170 sq ft. Intended to be used over long periods solely withe the staysail.

It wouldn’t have the fat cheeks like this but note the bow – part-submerged, which allows straight motion through the water and early fullness when under sail pressure – this allows the three foresails on the 8′ bowsprit.


1. Rudimentary keel of 3″ just to protect from rocks, until under aft positioned cockpit, when it curves out into a skeg, from which the aft pillar mounted rudder hangs;

2. Leeboard is positioned slightly further from the hull surface and is movable to suit the sails up at any time.


This is today’s issue. I’ve looked at any number of hull shapes and it’s been painstaking. Unfortunately, many classic mono designs look either a bit silly in a cat or else they have overhang which is a no-no on two counts:

Combine this doubleender’s plan view with the next pic and that’s close to it.

1.  Cats need full waterline length so the bows can be finer;

2.  Double-endedness is no problem on a cat;

3.  Too fine a hull and too much rocker leads to hobbyhorsing;

4.  Enough chines to approach a parabola is the ideal;

5.  Fullness is needs to begin about 6′ back from the bow.

The only hull shape which will allow all of this has part of the bow underwater and is much straighter as it goes aft, a curved sheer makes for pleasing lines at the gunwhale and the chines also follow that curvature bow to stern.   I’ve tried to capture this in the pictures.

Note the chines here.  Replace the transom with a sternpost and that’s about it, only 34 feet long, with two masts and a ketch rig.

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