Entry 11

Sturdy

Design by Horst Werner  horst.werner@sap.com

Loa 3.90 m (w/o rudder)
LoD 3.20 m
Beam 1.20 m
Total weight empty 37 kg
Loading capacity 150 kg
Draft26 cm
Total sail area 4.8 m2
Main 3,8 m2
Jib 1 m2

(Click on the image to see the VRML model)

This boat is designed for relaxed sailing on lakes in moderate winds. The low weight makes it a good cartopper. In relation to the amount of material given, it has a reasonable stability, which of course is not too much. Thus it got a keel similar to my "Clipper"-design, which keeps the lever of the heeling momentum small. The keel is a bit deeper than the keel of Clipper because the multichine hull itself does not provide lateral resistance when heeled (a sharpie hull does, as the Weekender proves). The keel has the further advantages of a very shallow draft and good rudder protection but limits the upwind capability of the boat and might be troublesome when you try to beach the boat in order to leave dry-footed. However it is possible to build a daggerboard version of the boat.

The boat carries two not too heavy adults or an adult and two kids. There's some stowage under the foredeck and, if a hole is cut into the rear bulkhead, under the aft deck. However I'd personally prefer to leave that aft compartment as emergency floatation. Additional floatation may be provided by a styrofoam block which is fixed under the thwart. An (almost) watertight hatch to close the front compartment would provide a maximum of safety, but I couldn't get it to fit on the sheets any more, so it's an extra.

In the following pictures, all parts made from plywood are yellow, whereas the parts made from lumber are red. The thwart in the middle is not to be used while sailing. Its main function is to stiffen the hull. It can be used when the boat is rowed (oarlocks are not in the picture but meant to be fitted) or anchored.

(Click on the image to see the VRML model)

The front bulkhead is built as a frame of four pieces of 25 mm (1") lumber (top and bottom are 40 mm wide, the sides are square) which serve as butt plates as well (These parts are cut from the rest of the "keel" plank). The outside of the butt joint is made by 50 mm wide fibreglass tape (maybe 200 g/m2, which has to be laminated before the panels are bent.

The plywood sides which are glued to this frame give it the necessary strength (torque resistance) to cope with the mast forces. The mast is put in a mast step on the bottom through a hole in the foredeck and is secured in place by the forestay. Shrouds should not be necessary due to the hull's limited stability.

 


Building sturdy

Construction is stitch and glue with taped seams, I estimate that about 1 kg of Epoxy and 70 cable tiers are needed. About 16 drywall screws will fix the bottom to the keel (Epoxy fillets between keel and bottom help transmitting the bending momentum). Here's the plywood sheet layout:

The 1" lumber is cut up like this:

Keel, Stem and Rudder are cut to a thickness of 22 mm, the aft bulkhead to 12 mm and the thwart to 18 mm. One of the 2"x4" beams is intended to be cut into 8 parts of about 20 x 20 x 2400 mm. These are used as follows:

  • main boom (2300 mm)= 1 part
  • main gaff (1550 mm)= 1 part
  • 2 rubrails scarfed from 2 parts = 4 parts
  • left: 2 parts (might be used to make a pair of small oars/paddles)
The other beam is cut into 5 planks of 2400 x 100 x 8.5 mm which are used for the decks. After cutting, we've got a total of 12 m of planks. Assuming the decks were rectangular, we'd need 10 x 0.8 m for the foredeck (91 cm wide, 80 cm long) and 4 x 1.04 m for the aft deck (104 cm wide and 40 cm long). So in total we'd need 12.16 m of these planks. The missing 0.16 m can certainly be saved due to the fact that the decks are more like triangles than like rectangles. The seams between the planks may be emphasized to get a salty look.

The mast and bowsprit are made from the poles.

The following pictures show how the sails fit in the given polytarps. They do not show the real sailcut.

Modifications for daggerboard version

Sorry I didn't have the time to make pictures of this version. The thwart has to be put 40 cm forward to form a "top plate" for a daggerboard case mounted between thwart an bottom. A slot of 26 cm length and 2,54 cm width (1") is cut in the middle of the thwart and the boat's bottom. The keel is reduced to a 2.5 x 2.5 cm (1" x 1") strip (or rather two: one in front of and one behind the daggerboard slot) which only serves for stiffening the bottom. The lower end of the bowstem is altered to fit to the smaller keel. The daggerboard is 80 cm long and 26 cm wide. The daggerboard and its case are made from rest of the 1" x 10" plank from which the keel is cut. Draft is now about 13 cm with the board up and 60 cm with the board down.

Horst Werner - short biography

I'm a mechanical engineer and have been reading about boat design as a hobby since 1998. Currently I'm building a 4.70 m folding tri of my own design in stitch and glue (See Duckworks Magazine's projects page). I use a self-written design system ("Ligo") for modeling and calculations. (Unfortunately this system is too buggy and complex to be used by anyone else, so please don't ask about it.)

Information about VRML

VRML (Virtual Reality Modeling Language) is a format to describe 3D-Models. You can display VRML models with your Web browser, if you add an appropriate plug-in like Cosmo Player. The cosmo player can be downloaded at
https://cosmo.sgi.com
 

 

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