March 22, 2014


First something about that inadequate planning leads to add on’s that becomes abortions. This statement comes from Manie B. I fully agree. It is much better to figure out everything in advance and not do changes. If your plan is not complete the project will get a life on its own and you are not the master anymore but just someone trying to put it back on track.
My problem is that I am not smart enough to foresee all the implications of my complex project. My brain is to small to in advance figure out how all the details interfere with each other. Therefore I end up with add on’s. However I do not consider all of them bad. Some will even be of great value for my next project.
Every time there is a restricting rule someone will find a loophole. It is ridicules to measure the size of a boat by length. It leads to absurdities like my swim platform. But the fact is that the European Recreational Directive’s harmonized rules, the International Towing Tank Conference, the US Coast Guard, the Nordic Boat Standard and other recognized bodies ,according to common practice, exclude spars, bowsprits, and rudders, bolted on swim platforms, pulpits, and other fittings from the measured length. Ange’lique and MoeJoe argue that my swim platform has buoyancy therefore it should be included in the measured length. I do not agree. Rudders are not included in the measured length and they certainly do have buoyancy, especially big ones with a fat profiles, like for example, NACA 63-021.
If my planned voyage can help to stop the stupid habit of measuring boats by length it would be a good thing.
Once again, every time a simple rule is in use people find loopholes. A complication that plugs the loophole mends the rule for a time and so it goes until we finally end up with one designs and the yacht designer is out of business.
I have never before built a boat to a rule if you do not consider the hole in my mother’s basement that I had to get Bris I through to get her out.
Adding on buoyancy parts is ridicules. Bolgers Folding Schooner is a good example of what it can lead to.
As for the seas smashing the swim platform. They build 60 feet long ocean racing multihulls that keep together. My engineering problems are order of magnitudes smaller. Do not worry.

About the video of Manie Bs margarine box. It looks like it has a ballast ratio of close to 100% and a very low center of gravity and an extremely low rotational mass moment of inertia. I do not think Manie B will have problems with stability at large angels of heel. But still to my mind his experiment is misleading.

Above the rule of the door. Difficult to find loopholes in. The best I could do was to remove the frame.

Below the boat Bris I comes out spring 1972.

Regards Yrvind

March 20, 2014

Yrvind Ten in 3D

Here is a 3D model of Yrvind Ten 1500 kg . You can play with it, just twist and turn it with your mouse.  A tip: toggle full screen mode and the experience will be even better. If you are using a Mac-computer, use Firefox web browser. Michael Tatschl made this 3D model. You can contact him at if you are interested in his work.

March 18, 2014


Yrvind thanks Sharpii2 for concern of his masts. However it feels embarrassing to be called master.

Yrvind 10 will be hard to flip, but the weather conditions on the planned route will be even harder. The boat will flip, not once but many  many times. It will flip forward and sideways, but I cannot see how any damage can be done.

I have experience of capsizing and of pitch-pooling. The first Bris had a 20 feet mast. She was capsized and pitch-pooled near Cape Horn and then once more capsized on Georges Bank outside Nantucket a stormy March night. The second Bris was knocked down to I am guessing 160 degrees near Uruguay after successfully rounding Cape Horn. Only the time when the boat was pitch-poled was there no sails up. During the two capsizes and the 160 degree knock down I had sails up. It was freak waves.  The 19 feet long Bris II also had an 20 feet mast.

However due to scale small boats are very strong, in fact the smaller they are the harder it is to break them. Galileo was the first understand the mechanism of it. Its called the square cube law. Because strength increases with the square of the scale but weight with the cube.

There is also the other side to the problem that favor the small boat. The destructing forces increases with scale.  Big boats attract big forces. The peripheral speed of the mast increases with its length and the hardness of water increases with the square of the hitting speed. So in all I guess by a scale of two the the bigger boat is 32 times less strong or strength diminishes with the 5th power if I am right.

Also when the seas starts to break I will secure the rigging with dynema (spectra) ropes. I am shore the mast will be strong enough with out them but it is only a few minutes work and I am not pressed for time.

The two masts in fact support each other. There is a spreader between them, a spreader with both ends fixed to the mast like a ladder in such a way that they can take up bending and torsion moments.

The masts will be very strong sideways capsizing. The worst case is pitch-pooling but thanks to the spreaders fixt ends even then they support each other as can bee seen on the photo of the experiment below.

The twin mast hardly bends for the same load. Of course if I have really bad luck they hit the water at exactly the same time. Even then they should be strong enough even without ropes to support them.

Above one way of reenforcing the rig with dynema ropes. Its only two meters up to the spreader so even though I am only 1.67 meter tall I easily reach the spreader.

Above some of the sail configurations.(Lansells illustration)

Above natures way of fixing the ends of spreaders. I will try to find a tree here in Sweden like that.

Regards Yrvind.

March 14, 2014


I am getting competition, friendly competition I assume. It is Manie B. from South Africa who is challenging. It is welcome. The more well conceived boats that are designed the more the people in Brussels the ones with the Recreational Boating Directive will stand out as fools.
One can read about the design at.

Manie are doing good work. However I like to add two reflections. First Steve Lewis box keel will interfere with stability and stability is one of small boats weaker points. The keel box will add a lot of volume low down. It has the same effect as putting a pontoon below the boat. It will tend to capsize it. The center of flotation should be as high as possible for maximum stability.

Second Manie likes a long Yankee Girl type keel for directional stability. It works but one should keep in mind that it’s only the parts in the end that are useful much in the same way as only the top and bottom part of a beam add to its strength. That is why we have I-beams and sandwich construction. The top part of the beam is in compression the bottom in tension the neutral axis in the middle is useless .
So with the long keel the middle part only add wetted surface. It is better to put that surface in the ends. However going downwind in strong winds the last thing I like to have in the bow is lateral area. That is why I in 1985 launched my first boat with a centerboard before the mast right up in the front. It was very successful and more boats with that principle has been built by others and me.
It is a complication but a windscreen wiper is also a complication but driving in rain and having a windsscreen wiper makes life less complicated. In the same way, when running before a gale a forward centerboard makes life less complicated

Below is a picture of the mock up of the batterys. I made the mock up becouse at 40 kg each the batterys are heawy to move.

Below is a picture of the sides of the battery boxes that contain the four 120 amp gel Sonnenshine batterys.

To be continued…

Regards Yrvind.

March 11, 2014


Interference is the biggest problem – by far. It is difficult to do a good centerboard, its difficult to do a good hatch, its difficult to do a good rigging, but the biggest difficulty is to make it all work together, in harmony and in an optimal way.

Below is an example. I was making waterproof stowage in the saloon. Putting up the frame of edges that takes the gasket. Everything was fine. The most practical way of building a small boat is to first  finish the interior, then do the deck. Suddenly I realized that when the deck is on I can only lift the lid to the stowage hatch 6 or 7 inches, because the side-decks tumblehome,  not very practical. Luckily I had only done one edge before I realized what a terrible mistake I was about to make. What if I had put on the deck first. A disaster, it would have been impossible to put in the four 120 amp batteries for example.

The more complex a boat is the more interference. The bigger the boat is the more complex it is. Each new component can interfere with all the previous ones. We get an factorial function. They increase extremely rapidly. 6 elements gives 720 combinations. 24 elements gives 6 to the power of 23. That is if you like to check them all you have to do 1000 checks each second for a time 1000 times longer than our universe has existed. Luckily not everything interferes with everything else. Problem is how to know.

Below is the edge in place and grinded away.

Below the created mess -but I fix it.

To bee continued…

Regards Yrvind.

March 6, 2014


Fact is amateur means lover of. Professional means doing it for money. So an amateur builds the best boat he can. An professional builds as bad a boat as he can get away with. The individual professional boatbuilder may be a skilled worker and he may like to do a good job but he has a boss that looks at the bottom line and if he continues to do good work instead of fast work he is soon out of his job.

Some production boats here in Sweden pride themselves of their high quality. In an interview the designer stated that ” The main bulkhead we laminate on booth sides to the hull. We also add an fillet before we do the glass.”

I am an amateur. Of course I laminate booth side with fillets to get a good radius and I do it not only on the main bulkhead but all bulkheads. But I also have a trick. I inject epoxy between the two laminations. I start by cutting out a groove on the bulkhead edge to get free flow right around. Even the partial bulkheads supporting the centerboard case there is more surface than comes to the mind about 200 cm by 3 cm and the strength of the Divinycell of about 10 kilos per square centimeter gives 6000 kilos supporting force there are four bulkheads in this area so about 24000 kilos the weight of the boat is less than 2000 kilos and its speed will rarely exceed 4 knots. So this is overbuilt but if in all detail you do your best you get an product that you really can love and lover thats the amateur by definition. Some may say it takes to long time, but what better can you do than something you love.

Below are some pictures of the infusion. I use NM-625 an epoxy that is very wetting and has low viscosity. The syringes are Codan 50-60 and 100 ml with catheter tip to take the tubing. I use copper tubing that can be left in place.

During epoxying an silicon rod is inserted that epoxy does not block the flow. Epoxy do not stick to silicon. The rod is extracted when the epoxi has set.

Alternating injecting and pouring the epoxy. This gives a fit down to the molecular level.

One more thing. On Saturday 8 of March at 15:00 I will give a public illustrated talk at the Stockholm Boat Show. Welcome.

To be continued…

Regards Yrvind.

March 4, 2014


The male mold for the window frames is now done. The female product will hold a 2×3 centimeter EPDM-cell-foam gasket. The windows will be made of tempered glass. That way I get a clear view. Glass transmit heat better than plastic. Therefore I will get a lot of condensation on the windows during wintertime. Some person may at first think that is bad. But humidity will be one of the biggest problems during the cold part of the year. If it gets to the windows I can get rid of it thus making a dryer boat. Dry cold is not really a problem.

Some may think polycarbonate is a good window material because of its high impact strength. It will however crack if exposed to static pressure. Also its very sensitive to solvents. for example just a touch aceton and it will crumble. Try it and you be amazed. In a few seconds its strengths is gone.

One problem with tempered glass is that nickel sulfied cases spantanius fracture in tempered glass. However this is greatly reduced by heat soak test. Statistically there will be about one chance in a millon of it to ockour. If so thanks to the EPDM gaskets I can change a window in a few nimutes. They have a sight thruogh diameter of 22 cm.

To speed up production the mold is for two frames at the time saves on vacum bagging.

A picture below.

To be continued…

Regards Yrvind

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