A SECOUND MODELL WITH BETTER SPOON BOW

Do it again, do it right.

I was not satisfied with the shape of the bow therefore I made an other one with a more rounded bow.

Modern yachts in contrast have very sharp wave piercing bows. Good for windward work but not so good for downwind. For several hundred years the hull shape was “cods head, mackeril tail”. Those ships sailed similar routes that cruising people chose. I belive in “cods head, mackeril tail” when running with a gale behind you. My belive is that that kind of bow reduces the risk of broaching.

Broaching is not a big deal for a small boat but its a nice feeling to sail a boat that behaves well in wild weather.

Below are some pictures.

First out me and the two models

On the secound modell I have started to build up the starboard sidedeck.

To be continued…

Regards Yrvind

CONFIRMING CORRECT DISPLACEMENT THE SIMPLE WAY

Below are some pictures confirming correct displacement.

The planned weight of Exlex Minor is ready for 5-6000 nautical miles is 800 kilos. The 1/10 modell weighs 0.8 kilo. Dipping her in the workshop baisen conforms that the draft 20 mm corresponding to 20 cm on the full scale boat is correct, correct .

To make it easier to see the waterline I have added some sawdust to the water. Click once or twice to enlarge.

Sawdust is a good thing for many uses.

To be continued…

Regards Yrvind

A SIMPLE WAY TO DESIGNE A SIMPLE HULL

Thursday night late I was back home in Västervik determined to get sailing in a new boat, Exlex Minor, 5.8 X 1.12 meters as soon as possible. Hence after sorting out several bourgeoi duties like mail, bank, internet I was back in workshop designing.

During my 40 days at sea I had well prepared my mind.

Nowadays yacht designing is almost exclusively done by computer and that is an excellent way of doing it. In the 70- I designed by ducks and splines. Later I got help from clever people with computers ,like John Letcher, Rolf Eliasson, Matt Layden and Guy Liljegren. At sea I thought of an other way.

Given a boats lenght, beam and draft there is a very simple way of figure out displacement using the prismatic coefficient. Prismatic coefficient is the fullness of the hull. 0.54 is common for sailboats. Sailboats also usally are 3 beams long, Exlex Minor hovewer are more than 5 beams long. Boats with a good lenght ratio can have higher prismatics. A higher prismatics gives more stability and a higher top speed for a given waterline lenght. I chose 0,7.

By multiply the midsection area by the lenght of the waterline by the prismatic the displacement is fond. In the case of Exlex Minor it is very simple just multiply beam by draft as its an rectangle

Exlex will have a waterline of about 5.6 meters she will have a beam of 1.12 meters. At 18 cm draft she gets 790 kilos displacement. At 20 cm draft ( about 8 inches) she gets 878 kilos displacement.

I started with a block of wood 58 cm long 5.6 cm vide and 9 cm high the bottom part was of MDF board to indicate the underwater part. The tricky part was to get the prismatics right, but as I have been around boats for a long time I got a sense of their shape. As they are usually 3 beams long I imagined a boat 3.36 meter long cut it in middle and added enough midpart to make it 5.8 meter long. Cargo ships are designed along similar lines, a forword part, an aft part and a parrallel middle section.

After shaping a half modell I made offsets of the surfaces and made a model.

Below are some pictures.

The wooden block being glued.

Clamping 3.7 mm plywood to the half modell to take off the lines.

The modell

The modell on a chair. More work will be done to her like giving her a spoon bow and make her waterproof. That done I will load her to 0.8 kilos, she is an 1/10 scale modell and float her to find her waterline.

I thank everyone who has donated money to help me with my project and get me back from Madeira. My economy has now crashed and I need to get plywood and other items for an full scale sailing modell before starting on the sandwich composite boat. I hope you will continue to support me. Me I will let everyone for free use my ideas and drawings as published here to build small safe enviromentally friendly boats. I really think I am into something new a good, a mountain bike for the oceans.

To be continued…

Regards Yrvind.

Back home

I am back home. There is many things to sort out, for example to get a new internet connection.

As soon I am settled I will start working this site and build a new and better boat called Exlex Minor with a length of 5.8 meters, beam 1,12 meters, draft of hull 0,18 meters and displacements loaded for 60 days at sea, 800 kilos. That will give approximately 5000 nautical miles. The building of this boat will be presented on this blogg.

I take the opportunity to thank everyone who has contributed to my last project, because at sea I been unable to express my gratitude.

Regards Yrvind