Scarper Flo (SF)
31ft Blue-water Gaff Cutter
by Jeff Gilbert 
by Jeff Gilbert

Editors Note:  This is the second in a series of original designs by Jeff Gilbert.   A native New Zealander, who now resides in Australia, Jeff has a broad knowledge of boats, great drafting skills, and an eye for beauty.  Here is Scarper Flo, his well thought out offshore cruiser with many unusual features.  Contact Jeff about acquiring plans.  See also:  Scarper Flo Q & A, and Jeff's Design Philosophy

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Jeff Glibert Design # 63

SF is a single hard-chine plywood interpretation of the traditional Pilot Cutter. Most sailors will be aware of the thoroughly proven Ocean-Crossing capabilities of this design genre. However SF is atypical in that the long keel is replaced by a combination steel twin-stub and drop keel attached to a cradle fitted beneath & within the yacht. SF can thus handle shoals of 3 feet, & can be beached between tides for a bottom scrub & paint.

SF’s design aims:

  • 1/ Possiblility of amateur build (keel best contracted to prof. welder).
  • 2/ Motion comfort whilst achieving reasonable pace in a seaway.
  • 3/ Cost bourne progressively by av.salary at a building pace of 15hrs pw.
  • 4/ Live-aboard comfort for couple plus occassional guest. Note armchairs.

The gaff rig and bowsprit, plus 50% ballast ratio, allow a spectacular spread of sail (nearly 1000 ft2) in safety, without resorting to either spinakker or the huge aspect ratios which have been the epitaph of many Vendee Globe yachts. The cutter rig divides the sail plan into manageable chunks which enabe the boat to be singlehanded when necessary, and handled easily by the intended working crew of two. This sail area, along with the narrow beam, lack of overhangs & relatively low wet area gives a projected cruising speed of 7 knots. Experience with similar Pilot Cutter(PC) designs* has taught us that SF’s high displacement (cf modern fast cruiser norms) will not slow her. When combined with her slim lines, this weight will serve rather to provide the momentum needed to ghost effectively in light airs. Various PC designs have consistently achieved passage speeds which defy their apparently pedestrian Disp:WLL ratios. The high displacement & deadrise provide a smooth motion in a seaway, and enable a generous fitout with stowage capacity and headroom exceeding that of many boats 5 feet longer.

The drawings show my preferred accommodations vis--vis 4/ above. Of course they can be completely revised to suit individual needs. Note the armchairs.
(click to enlarge)

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LOA 40'9" Mast ht(awl) 44'6"
B max 8'4" Ballast Ratio 50%
SA-Main 480 Prismatic Cf. 0.57
     Foresail 225 Disp/WLL 217
     Staysail 209 LWL 29'6"
SA/Disp. 27.2 Displacement 5.56T
LOD 31'4" HR min (Galley) 6'6"
Draft (max) 7'6" Draft (keel up 3'0"

Auxiliary power is essential for manoevering and tackling harbour entrances. I’ve drawn an outboard in a dedicated well because I’ve already spent too much time floundering about in cramped spaces with errant diesels. A Honda 40hp Four-Stroke would suit admirably. Its quiet, environmentally clean, reliable, easily maintained and returns good fuel consumption at the operating loads demanded. It has more than enough power to handle bar breaks, and move SF’s 6 tons to shelter in a fair hurry to avoid sudden blows that this boat would endure in a workmanlike manner, but its crew with less comfort. Uffa Fox comments that a well-found yacht’s ability to handle storms far outstrips that of its crew. The tiller must pass over the well, but thus obtains ample leverage for the rudder size and boat mass. The covered well makes a great bait table as well as deadening engine noise. Uncovered it makes basic engine maintenance simpler & safer, especially with SF’s slim stern. Motor removed, the well can used for fishing; fitted with a wire cage,for underway bathing or cooling the beer.

The chart table folds up against the cabin’s rear bulkhead; charts taped to its top are thus visible to the helm via a porthole. With the table up an 8’ x 2’ Qtr berth is available. The chart table seat slides forward and down to form part of this berth, which extends under the port cockpit seat. The opposite & stern cockpit seats contain lockers for safety gear, plus a glass-epoxy sealed well for washing clothes (dump them in with soap while underway!).

SF is built from 25mm marine ply, on ply bulkheads and laminated ring frames. Stringers are unnecessary except as chine logs. She is sheathed outside by paint-protected fiberglass, the interior ply faces being epoxy-coated alone. Decks and deckhouse are of 18mm ply, with partners of 12mm more than doubling the roof thickness in the mast area. The deep sole gives SF full headroom without requiring relief from a companionway hatch. It’s replaced by a full & solid roof above which a 4-person provisioned life-raft is fixed by quick-release harness. The strengthened companionway door is hung from heavy-duty hinges bolted to the cabin’s rear bulkhead, and can be sealed from inside with heavy-duty clamps. This setup guarantees no repeat of the Fastnet Race disaster of 1979, where the subsequent investigation reported most sinkings caused by the weak & leaky combination of companionway doors & sliding hatches. Designers of current small ocean-going cruiser-racers must admit cabin access to be generally more concerned with convenience/comfort than structural integrity and hence safety.

The Galley features a 7 foot long work bench which can be converted to a bunk. The 7x2 ft Galley sole can be levelled on long tacks by hinges along the boat keel and simple bolts with a selection of holes opposite. A double sea berth can be had by dropping the table to seat height & lowering the forr’d seat back onto the armchair arm. (Similarly a single berth by dropping the starboard half of table/seat back).

After due consideration it has been decided to moderate SF’s rather unusual keel design. Any loss in ease of operation of the cutter is a matter of debate, but the simplification of the build (with attendant cost & time savings) is a matter of fact. Scarper Flo Mk II will appear on this site as soon as completed………

Jeff Gilbert,

June 2000

*eg Dyarchy (Laurent Giles), Bristol Channel Cutter (Lyle Hess), WesternmaN cutters (Irens)

Rockport 30 (Chuck Paine), Cornish Crabber (Roger Dongray) Austral (Mark Smaalders).

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