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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||8 hp|
|Draught||1.15 m||Design category / Crew||C6|
|Light weight / ballast||1 800 / 600 kg||Building time with kit||2 200 hours|
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 and these show 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, in particular at slow speed, thus being ideal for manoeuvring under sail in confined waters. Finally, the short classic keel, with the tiller at mid-cockpit, combined with a well-canvassed rig, appears to be an excellent compromise for a boat requiring easy drying out. In addition, it reduces dramatically the risk of rudder damage. At the owner’s request, the draught may be modified to cope with local mooring conditions. The NC cut plywood structure. As 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 (my own son) 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 layers of cold moulded 6 mm plywood. See here the assembly process and the pictures of the construction.
The boatbuilder and I have decided that the first Pen-Hir will be built respecting sustainable development, as much as possible, and 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 extremely 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 properly protected. All main timber parts are made of oak, in particular 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 common marine plywood and redwood as timber.
In the same ecological spirit, I have decided to use electric propulsion. It is based on a new 2 kW Torqeedo Cruise R outboard motor giving a thrust equivalent to a 6 hp petrol outboard. Remote throttle control is located in the cockpit at helmsman’s hand. The motor is tilted in the aft well, so there is not any speed loss when under sail. Four gel type batteries (100 AH), located under fore berths, allow 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 come back to shore if the wind falls down. Batteries can be charged either by the means of a vertical axis wind charger or from harbour electric power. The aft motor well may also receive a petrol outboard at the owner’s choice.
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