Petrel 33

Petrel 33: widen your horizons

Petrel 33 is the logical evolution of her smaller sister Petrel 28 , with the task to expand the horizons of cruising activity for a 4-6 person crew, raising the bar of onboard comfort, keeping the boat size under the critical (for a homebuilder) size of 34 foot – 10 meters of overall length.

A “new classic” looking cruiser, sturdy, with no frills and weird solutions, ready to let you sail with a decent speed and a very good comfort level both at anchor and sailing.


the starting point is the very good sailing capabilities shown by the Petrel 28, so I decided to develope this hull into a enlarged design, keeping a quite narrow hull for actual standard, prolonging the bow lines for a plumb stempost; I expect to have a similar behaviour of the proven 28footer, with a tender weather helm in every situation, a very soft and gentle wave riding attitude in a seaway, and a good acceleration coming out of the tacks, I expect a little bit more speed given the longer water length; section are moderately full at the bow, maximum beam is around 60% of hull lenght , transom sections keep a moderate VEE

petrel 33 hull lines

Stability calculations give us good parameters (see stability curve attached), with a real large positive area stability, a 123° AVS (Angle of Vanishing Stability) with loaded boat, and a minimal negative area in the stability curves.



Rig and sailplan:

sailplan is based on a 50% area split among mainsail and a furling jib; we kept the upwind sailing area to a moderate value, avoiding “wannabe racers” temptations; a decent sized gennaker can be hoisted on the fixed bowsprit, an obvious choice given the fact that the new generation furlers are making this sails very easy to manage for cruising crews too, adding the pleasure of sailing downwind in light airs at a decent pace, a weather situation which is quite a pain in normal mainsail + jib configurations ; in roughest situation you can hoist a storm jib on a removable internal stay fitted on a high load chainplate leaning on the forward structural bulkhead ; rig is a classical 2 spreaders mast , spreaders are 15° swept, there is a structural backstay and no structural runners, lower shrouds are doubled.

Deck gear:

deck gear configuration features classical sturdy and manageable solutions, without too many frills: 4 self tailing winches to pull sheets, halyards and control lines, 2 stoppers array on cabin top panel, 2 tracks for jib cars, so that the jib can keep a decent shape even furled, a small track for the mainsail purchase, all the control lines are led to cockpit to avoid bow walks in “spicy” situations (plans will detail how to make bombproof fitting points for lifelines too);


Boat will be powered by a diesel (20-30 HP) or electric (7 kW) inboard engine fitted with a saildrive or shaft-line transmission; this will allow to keep a decent pace while motoring in zero wind situation, or to add a good booster to sail thrust if needed; I expect to reach a 6.5 knots boat speed at 2000 Rpm with a 30 HP diesel engine.

Rudder and steering system:

Rudder is a single blade semi-compensated one with tiller steering system; there will be two options detailed on plans: spade rudder with ss steel shaft (this solution is depicted in rendered images), and an easier to build transom hung rudder.


Finkeel is NACA profile keel made of welded steel plates, ; ballast is made by lead poured in the keel hollows ; keel is fitted on the hull with a web of bolts on solid hardwood floors, with nuts and high thickness ss steel counterplates under the cabin floorings; keel load is carefully distributed to avoid any local high stress area.

Interiors and on board living:

This area marks the main differences among this 34 footer and her smaller sister; higher hull topsides and two more meters of boat make a world of difference in terms of interiors and on board comfort; we have 6 regular berths, a comfortable galley and dinette area, a decent volume for on board systems and storage, all that you need to medium-long range sailing given the size of the boat; both forward and after cabin are closed with a small door to gain a little bit more privacy ; cabin height is around 191 cm 

cockpit is quite wide, and it’s designed to be comfortable for a crew of 6 while sailing with the heeled boat too; transom area is protected by a sturdy wooden hinged structure that can be lowered when moored to be used as a transom platform. Low sleek coamings protect the forward area of the cockpit , making the primary winch basement too; toerails and good sized areas among cabin flanks and hull sheerline make going to the bow a very safe operation even when boat is heeled and in rough conditions;

Building system:

given the good amount of miles sailed by Petrel 28  in every sea state with very good reliability, I keep a similar structure for this project, upgrading the scantlings to cope with higher stresses; so the boat structure is a grid of plywood bulkheads and frames linked by solid wood stringers and a mixed plywood-solid wood structure forming keel backbone and stempost ; hull planking is made by 12 mm plywood, with the radiused area made by two layers of 6 mm plywood panels , all glued to the underlying structural grid , in a reliable , sturdy and easy to build system called “radius chine” ; cabin , cockpit and deck surfaces are made by 10-12 mm plywood panels stiffened by a grid of secondary stringers, solid beams and other structural elements; the hull bottom is further stiffened by a number of solid wood floors , tightly spaced in the centerboat area, where they bear the finkeel loads. All critical areas and structural bondings are strengthened and stiffened by epoxy resin laminated glass fabric and epoxy resin liquid joinery and structural bondings. This building system is definitely suited to be realized by home builders or small boatyards, with a basic level of wood craftmanship , in a decent amount of time given the size of the boat.

In my view this will allow a small boatyard to build and offer a highly customized top level sailboat keeping the final prize to a reasonable level, which is basically the main concern when it comes to manage a small boatyard.

petrel 33_strutt

Building plans and study plans: project Petrel 33 is is completed : now I’m starting the long and meticulous process of drawing the building plans; complete plans will be available approximately at the end of spring at this link , anyway if someone is so committed to long for an immediate start of construction he can purchase plans starting from now, a first batch of drawings (hull parts , assembly scaffold and hull structures) will be delivered within a week so that he can start building, the rest will follow as scheduled within half of June 2018; study plans and bill of materials will be available approximately within the end of April 2018 and will be downloadable form this page for free, as usual.
Stay tuned !!!

plans price: 900 € for paper sheets, 840€ for pdf format drawings, 350 € for CAD engraving files (required if you want to cut all the plywood parts with CNC machinery, includes keel steel plating shapes) ; plans will be made approximately of 27 drawings and a 25 pages booklet with assembly sequence, tips and tricks, plans can be purchased here, a discount will be available for the first buyer .

Petrel 33 specifications

  • Hull length: 9,90 m (bowsprit included)

  • Overall length: 9,90 m

  • maximum beam: 3,03 m

  • Prismatic coefficient: 0,53

  • sink rate: 170kg/cm

  • canoe body wet surface: 18 m2

  • draft at design displacement: 1,80 m

  • vacant ship diplacement: 3400 kg (all gear up, no water and food, no fuel)

  • design displacement: 4050kg (crew of 4 + luggage, 50kg fuel, acqua 150 liters water, 100 kg extra)

  • maximum displacement: 4500 kg (crew of 6 + luggage, full fuel, full water)

  • ballast: 1300 kg: fixed keel

  • upwind sail area : 47,3 m2 , mainsail 23.2 m2, jib 24 m2, staysail on removable babystay: 6.5 m2

  • gennaker: 65 m2

  • mast height on DWL: m 13,3

  • performance parameters : SA/displ^0.66 = 19.5 , SA/wet surface = 2.6 (canoe body only)

  • engine: diesel inboard with saildrive or shaftline transmission, 20-30 HP, 50 liters fuel tank , electric engine specifications on plans

  • accommodations: 6 fulls sized (1,90 m or more) berths, 1 V berth at bow, 1 double berth on transom , 2 galley berths

  • interiors: charting table with main electric panel, VHF radio and chart plotter area, galley with stove, sink and 30 liters fridge, enclosed toilet with WC sink and shower, central table in dinette with foldable wings. 190 cm height in the whole galley area.

  • Systems: 12 v and 220 V wiring scheme, fresh water and black water plumbing scheme, 200 or more liter freshwater tanks.; two service batteries and a engine dedicated battery

  • CE label : possible B6/C10 , data to be required as extra item.

  • plans: 900€ for paper version, 840 for PDF version , 350 for CNC cutting files , can be purchased here