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Traditionnal classic keel boat, 7.5 m long. The Architect boat!
|Hull length / waterline||7.49 / 6.85 m||Sail area||33.8 m²|
|Breadth / waterline||2.50 / 2.07 m||Outboard motor||10 hp|
|Draught||1.15 m||Design category / Crew||B6|
|Light weight / ballast||1 850 / 600 kg||Building time with kit||2 200 hours|
New version 2023
On the occurrence of a new order for a Pen-Hir at the Grand-Largue shipyard, I have modified the plans of the Pen-Hir to make the following main changes:
- Design category B instead of C, obtained by closing the space under the side deck of the cockpit and the motor well’s side spaces. The companionway threshold has been raised by 50 mm. Note that storing the beaching legs in a cockpit locker is possible. For those mainly aiming for coastal navigation in a tidal region, the beaching legs can be stored under the side deck of the cockpit, but then the boat remains in category C.
- The geometry of the engine well has been simplified with oblique sides. It is possible to place an electric motor or a petrol outboard motor of 10 hp.
The sail plan is unchanged, but I have improved many rigging details, considering the experience of 12 years of navigation by the architect on his personal Pen-Hir. In particular, this facilitates single-handed navigation.
- Finally, the plans of the boat were modelled in 3D, which allowed a total overhaul of the construction manual. Appendix 4 presents more than 60 pages of 3D views of all the stages of the boat assembly.
The classic lateral plane.
All traditional yachts have a classic keel with the rudder attached at the aft. On modern boats, we always try to reduce the wet area and, therefore, to have a fin keel and a separated rudder. On Pen-Hir, I was very concerned about both performances and the ability to dry out on legs, which makes it possible to avoid calling in modern marinas. I made drag calculations showing that the number of appendages is a major factor. In other words, a classic keel-rudder is one appendage only, whereas many modern sailing boats have 3 (keel and 2 rudders). A classic keel also gives a more effective lateral resistance, particularly at slow speed, thus ideal for manoeuvring under sail in confined waters. Finally, the classic short keel, with the tiller at mid-cockpit and a well-canvassed rig, appears to be an excellent compromise for a boat requiring easy drying out. In addition, it dramatically reduces the risk of rudder damage. The draught may be modified at the owner’s request to cope with local mooring conditions. The NC cut plywood structure. Like many others of my designs, the structure of Pen-Hir is made of crisscrossed plywood bulkheads, including the vertical keel. This allows Icarai boatbuilder in Cherbourg (now closed) to have the boat ready for planking, including most of her accommodation parts, two weeks after receiving the NC cut plywood panels. The bottom planking is made of one single developed plywood panel. The bilge and sides are made of two cold moulded 6 mm plywood layers.
The boatbuilder and I have decided that the first Pen-Hir will be built respecting sustainable development as much as possible. We have launched a research and development program with several laboratories. We chose to exclude all tropical woods and, in particular, okume or mahogany plywood. The boat is made of first-class Finnish birch plywood, which is highly resistant and stiff. The only drawback is that birch, as okume, is not a durable wood. Therefore the hull and deck are epoxy sheathed, and all edges are properly protected. All main timber parts are made of oak, particularly the coachroof coamings. Pine is also used in the accommodations. The mast and spars are made of Douglas fir. Of course, Pen-Hir may also be built with okume marine plywood and redwood as timber.
In the same ecological spirit, I have decided to use electric propulsion. It is based on a 2 kW Torqeedo Cruise R outboard motor giving a thrust equivalent to a 6 hp petrol outboard. The remote throttle control is located in the cabin at helmsman’s hand. The motor is tilted in the aft well, so there is no speed loss when under sail. The batteries are located under the fore berths, allowing a range of about 20 nautical miles at 4 knots on a quiet sea. The motor is mainly intended for harbour access and manoeuvering but may also be used to return to shore if the wind falls. Batteries are charged from harbour electric power. The aft motor well may also receive a petrol outboard (up to 10 hp) at the owner’s choice.
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