Changing course has lead people to criticize me because they think I am wasting other people’s time and money. That critic would have been fair if Yrvind Ten had lead to nothing. That is not the case. Valuable knowledge has been gained. Much progress has been made that can be used on other small boats.

Serge Testas, Acrohc Australis was not twelve feet. In the back end she had a big outboard engine and in the forward part a bowsprit. Although these things no doubt could be removed, they were permanent.

This is not against common practice, and it’s the duty of o person trying to brake records to try to stretch the rules and to find loop-holes. Tax layers do that all the time as do people involved in for example Am Cup.

I mention earlier the “Hula” that added unmeasured buoyancy to New Zeeland’s Am Cup boat. On a ten feet boat you could add huge twin buoyant rudders, then locking them making it into an twenty feet trimaran and still sail within the ten feet rule.

Hugo Vilens April Fool was not a healthy boat either. Not before he added an outboard engine could he get offshore. Gerry Spiess and Serge Testa also had to use engines. I believe a small boat should be able to manage with an oar.

I realized that if I did not bend the rule some other designer would, but when I started I did not realize how much the rules could be bend. Size cannot be determined by only length.

Living with Yrvind Ten for tree years did teach me to think small. She was a stepping-stone to a much smaller and saner boat, Yrvind Ex Lex 4.5 x 1x 0.2 meter displacing 500 kilos a third of Yrvind Ten.

I have talked this over with my sponsors and friends and they are willing to continue to support me. In fact some of them think it’s a very good idea.

Quite a few of my supporters are turning up here in Västervik Saturday 16 of May to help me to laminate the new hull.  First I will give a public illustrated talk at Bankens Dag 13:00 in Biostaden together with Captain Thomas Grahn. Everyone is welcome to the talk.

Below the 4 cm thick Divinycell core of Ex Lex ready to recive the NM-epoxy lamination.

To be continued…

Regards Yrvind


Some people mind that I have changed my mind, but only idiots never change their minds. It is me who is going to do the sailing I therefore have the right to change my mind.

The note belov have been hanging on my wall for over a year.

The hull of the new boat is extremely easy to build. I know that the hull is the quickest part but I built a few other boats so I have something to compare with.

One side of the hull is already covered with 4 cm thick Divinycell.

To be continued…

Regards Yrvind


Why would anyone spend time and money trying to find a solution to such a simple task as securing a hatch? Builders of production boats ignore the problem. Professionals try to get away with as little as possible, amateurs do their best. In this case the leek proof hatches subdivide my boat into a number of waterproof compartments. The stored items gets protected from the elements and in the unlikely case of the hull getting holed they give flotation or contain the damage to the holed compartment.
It is true that a wing nut style bolt head or a simple small “T” handle welded to the Torx bolt head would make it easier to undo the bolts without any tools. I try to reduce the number of objects that can hurt me. That’s why I forgo that solution.
I do not think that I am likely to loose my Torx tool. 1976 I started to build a 19 feet aluminum boat. June 1980 I rounded Cape Horn with her. I divided the boat into several waterproof compartments bolting down the hatches more or less the same way. Obviously at that time there were no Torx bolts so I used hex heads. I had about 200 of those bolts on board. I still have quite a few of them M6 25 mm long. Not only do I have the bolts I also still have the tool. I used the same system on some of the hatches on Amphibie-Bris 89 sailing to Newfoundland and on Yrvind.com 2011 sailing to Martinique still the with the same tool. Torx tools are not cumbersome I will bring a score.

Foto showing the tool I used on my voyages since 1978. A bit rusty after the Martinique voyage but still functional.

Will the screws fail due to metal fatigue? I do not think so. There are fore M8 screws to each hatch. M6 would be plenty, even M5. I am even sure four M4 would do the job. There is plenty of redundancy.
Over center latches are good but here the geometry is not suitable for them.
Knots have been suggested. Knots are good. I have used them in in the sleeping room below the bed. Those hatches do not need to bee waterproof because the whole room can be sealed off.
I have knurled the screws. Thus on fine days I need only to screw them down with my fingers. When the sea starts breaking I tighten them up.
Have you ever been surprised at what a difference a few drips of oil can make to a rusty tool? The bronze washer is there to reduce friction and it works like oil. Now if by turning the screw the threads on the washer will be damaged so that it get stuck there permanently? So what? The better.

Photo showing knurls and cut away threads near screw head. I will bring hundreds.

Photo showing hatches in bedroom secured by lashing.

The system consists of three “cleats” and a string. There are twelv compartments below the bed. The matrass is divided into three parts for easy acces.

To be continued…

Regards Yrvind.


Long time no see. The reason is I am now working full time. After 16:00 I am writing a new book to finance the project. And before 16:00 I am working on the boat. Also to keep fit I have to take time of for that. Sundays and Wednesdays is running or kayak, Tuesday and Friday after 18:00 one hour exercises.
Also I am working on the interior now and it does not produce very exciting texts or pictures.
However because of the planned route the standard have to be much higher than on ordinary cruising boats, especially regarding stowage. Everything must be secured and waterproof. The back part of the boat, the sleeping room is the easiest part because the whole compartment can be closed of. The forward part is not so easy because water can come in through the entrance hatch when I have to open it for going on deck or work with the rigging or leeboards.
One more reason is I have been on the wrong track a few times and had to go back to square one which is time consuming.
And to be honest, I did work faster when I was younger, but of course did even more mistakes and more sloppy work then.
On the whole I have a nice time with my projects and enjoy life.
Below are a few pictures.

Abowe. The main closing hatches. Inside the compartments are subdivided.

Abowe: One of the main hatches. There is a 20×30 mm EPDM closed cell gasket running around the edge to prevent water from entering. The gasket is not glued but is squised into place, therefore wery easy to replace even at sea.

To transfer the closing edge I used thumb tacks.

an fuzzy close up.

The thumb tack and tejp.

The thumb tacks has marked a pice of cardboard. The cardboard is transfering the edge to the lid .

I did cinsider several was of closing the hatch. Finaly I decided on bolting it down. It not the quickest way but the strongest and most flexible and secure. It is easy to adjust the pressure on the gasket. It will take a few minutes to open the hatch. The process will be repeated thousands of times during the voyage. I did worry about stainless against stainless so I did a stress test. It sized up so hard it was impossible to mowe. I had to use the grinder to split the nut. I probably overdid the test but on the other hind I did not fancy being down the roaring forties with no acces to my food. I wanted to be sure.

I went back to square one and did fittings of aluminum bronze. It is ecceptionally wear resistant and you are well advised to use sharp drills.

the bronze fitting.

One fitting temporarily in place.

Bronze fitting and drain channel.

One of the drain outlets.

One of the screws temporarily in place.

To reduce friction I made bronze washers. In order not to lose them I threaded them like a nut. At the top of the nut, just below its head I remowed the threads on the lathe. Now the washer can rotate freely up there but not fall off. It works well.

To be continued…

Regards Yrvind.


Manie B has upgraded his challange. I wish him good luck. I am sure a full keel will work. Its more a question of convinience. Sure sail area foreward will help overcome weather helm but you will have a fight between two forces. To my mind its better to eleminate the keel.

For more about his challange see:


If Manie likes to quote from my work he is welcome.

I wonder about the byrocrats in Port Elisabeth will they give problems?

I have been to the book fair in Göteborg, to NM-epoxy in to get more epoxy, to Garmin, to Teufelberger for ropes, doing research in archives for my new book and much more.

Now I am back in Västervik for more work on the boat and book.

To be continued…

Regards Yrvind


To my disappointment the presentation of Yrvind Tens slotted leeboards was not universally met with rapturous applause. Some people think they will cause too much drag and not be strong enough. Therefore I valiantly feel obliged to come to their defense.

Aviators did invent the name but not the flaps, navigators did. The classical rudder attached to a long keel is a flap. If the tiller is moved a few degrees to weather the boat becomes more weatherly. That the rudder in that position creates a bit more drag is a minor point as long as the boat wins races. On the other hand, going to the extreme by moving the sail area forward so that you can keep the tiller 10 or 15 degrees to weather will increase the keels lifting force even more but then the drag will be so great that the boat has no chance of winning.

If the boat is propelled by sail and not an airplane engine the flap can and must of course be designed accordingly. I also like to point out that the leeboard is overlapping the flap. Therefore it will be attached not on the foils weak trailing edge but more forward in a position, strong enough.

From a fluid dynamic point of view the constellation mainsail and overlapping genua is a slotted flap as A. Gentry has shown. Land yachts use slotted wings and they are very fast. To my mind if slotted flaps can be used on sailing boats for rudders and sails I see no reason why I should not use them on my leeboards, its just a question of good engineering.

Why do I not use a long fixed keel as is suggested? Well it is certainly quite OK for heading into gales, but in my opinion, a centerboard or leeboard placed well forward the sail area is a much better option, and like I have said before, when retracted less likely to capsize the boat. It gives you a choice.

1989 I sailed the 15 feet Bris-Amfibie from Ireland to Newfoundland against the prevailing westerly’s. The mast was ten feet long. In heavy weather I had a 1 square meter jib and a 2 square meter triangular main. Between 6 and 18 of June we had continues contrary gales. The boat had a centerboard. It was placed well forward of the mast. Its area was about ¼ of a square meter (0.6 m deep x 0.4 m cord). Finally after 12 days the sun came out and I got a chance to fix my position. To my joy it was more westerly then when the gales had started.

We arrived in St Johns after 47 days. It had been a stormy passage but no capsizes, nothing broken, all the plastic jerry cans topped up with rainwater.

Before leaving Sweden I gave some yachtsmen lessons in celest navigation. They where bound for Nova Scotia.

“We might see each other on the other side” I suggested.

“I am not so sure” their captain said.

“Your boat is so much smaller it will take you longer time and we cannot wait for you.”

It was an argument plausible enough. After all they had a modern powerful 35 feet boat equipped with a strong diesel engine, big fuel tanks, radar and all the other stuff. I had my oar and sextant.

In the end we never meet them. The North Atlantic had been too stormy that year, they later told me. After two weeks they had turned around and run. Everything was a mess in their boat. Later they sold her.

The problem with a long fixed keel like the one Manie B is planning to have on his ten footer is that going downwind he will get weather helm and a lot of drag. On a circumnavigation there will hopefully be much downwind sailing. Leeboards on the other hand, they have even less drag than centerboards because the smooth bottom will cause no turbulence. In strong following winds I will use my twin rudders like a snowplow giving her a lot of inherent course stability.

All my experience and all my knowledge speak against the long fixed keel. Please do not use it. I never go back to it.

Below are some pictures of Bris Amphibie. The centerboard can be lowered further had not the floor been there. Click once or twice to enlarge.

Above Bris Amphibie sailing her main is 2 meter square her jib 1 meter square.

The boat.

A bit of the centerboard can be seen.

Regards Yrvind.


Every sailor knows, or ought to know that the force created by the flow over a foil increases with the square of its speed.
If Yrvind Ten would make three knots through the water hard on the wind in ideal conditions I be very happy.
If she will make half a knot in gale conditions I will be equally happy.
The heart of the matter is that the power of the foil to resist leeway has in the gale case been reduced to 2.8 %, very unsatisfactory.
(3 divided by ½ = 6. Six squared equals 36. 1:36 = 2.8 %)
To make things worse the need for lateral force in a gale is much bigger than in nice weather.
Airplanes have a similar problem. During take off, when they travel relatively slow, they need lots of lifting force.
In order to become airborne they employ flaps. That is, the rear portion of the wing rotates downwards. Flaps are high lift devices. They also reduce the stalling speed.
I have decided to use flaps on my leeboards – detachable flaps.
I will have an asymmetrical leeboard on each side, asymmetrical because they are more efficient.
I will use a slotted flap. They allow fluid to pass between the foil and the flap. That way I will have no problem to seal the gap.
I will place the flap not in the same streamline but in the way a jib and main are positioned in relation to each other, with a bit of overlap.
In good conditions the flap will stay on deck because the leeboard itself will be sufficient to prevent leeway. That way drag is reduced.
I only need one flap as I can flip it bottom for top using it on both sides.
When I put the flap on and take it of, the leeboard will be out of water. That way I can easily do the work from the hatch.
In nice weather I increase the sail area and reduce the lateral area. In rough weather I increase lateral area and reduce sail area.
Before I add an object to the boat I ask myself, do this thing earn its keep? In this case I believe it does, for the following reasons. Not many small boats have been cruising the roaring forties and not many people live there. What we know about the weather there comes mostly from big boats. But, big boats are not stationary observers, often they voluntary travel with east moving weather systems. That way they can enjoy and report strong westerly winds for long periods of time.
Compared to bigger boats Yrvind Ten with her speed of about two knots can be considered almost stationary. She will experience completely different weather patterns. She will be exposed to two or three lows each week. When a depression has passed there will often be nice easterly winds – not adding much to the progress. From a stationary observers viewpoint the roaring forties is not a strong trade wind.
To complicate matters there are also strong easterly gales. Once, when I was less experienced I rode one out in comfort to a sea anchor. When the weather had moderated and the sun came out I fixed my position. I had been set back 150 miles.
Some navigators may think that’s a good deal, not me. My present boat will hopefully be able to fight gales head on. The new strategy to deal with contrary gales is to dig in, to hold on stubbornly – at the risk of being capsized – until the wind swings over to a more favorable quarter, then I will ease the sheets and run.
Slotted flaps are high lift devices. They reduce the stalling speed. I am betting on that they will earn their keep.
However one must not forget that in stormy conditions flow around foils is very turbulent. One reason for that is the circular movement of the water particles in a wave. At the top of the wave they move in the same direction as the wind at the trough in the opposite. In a gale the speed difference is often more than six knots, a speed far higher than Yrvind Tens. Accordingly, theoretically, the flow around the foils will vary as a sine curve, sometimes being positive, sometimes negative.
In reality turbulence will create much chaos. Then only a lot of lateral surface prevents leeway, a bit like a parachute. So in stormy conditions Yrvind Ten needs all the lateral area she can get. The slotted flap will not only increase lifting force when there is flow, it will also at the same time increase lateral area. The leeboards itself are already as big as I dare to make them.

Below are some pictures. Click once or twice to enlarge.

Above the slotted flap.

The flap laying on deck.

Slotted flap on healead boat. Front vieuw.

Top vieuw.

To be continued…

Regards Yrvind.


Sharpii 2 is still worried about my rig. He beliefs a breaker may rip out the mast and deck fittings and leave a hole in the deck. I disagree. It is not a war zone out there. The waves are not loaded with dynamite. Let me explain:
It is the terrible capsizes and pitchpooles of big boats, like Smeetons 46 feet Tzu Hang and Erling Tambs 47 feet Sandefjord that have filled cruising people with horror. Compared to the above boats, Yrvind Ten and the old Bris are small.
Bris was capsized and pitchpooled near Cape Horn 1974. On a stormy March night 1976 the same boat capsized again, now on Georges Bank, outside Nantucket. On each occasion her 20 feet tall rig came up without a scratch. She had one pair of spreaders and the length of the unsupported column was 10 feet. Yrvind Tens unsupported column is 6 feet. Ten divided by six, squared is 2.777… That is how much stronger the geometry makes that column, according to Euler. The “shroud angle” to the supporting spar is 38 degrees. For Bris the corresponding angle is 13 degrees. The ratio of tangents for those angles is 3.38. The larger the angle, the less is the compression or buckling force. One more thing, the peripheral speed of a mast increases with its length. The length ratio between the two masts is 2.222… The hardness of water increases with the square of the hitting speed. 2.222… squared is 4.94… Now multiply these three numbers 4.94×3.38×2.777 and you get 46.36… The scale effect suggests that if the two masts are built with the same dimensions and materials Yrvind Tens 9 feet mast will be 46 times as resilient than Bris 20 feet mast.
Of course I do not have the faintest ideas of the forces, accelerations, rotational speeds, mass moment of inertia and other factors that are involved in a capsize, neither do Sharpii2, neither do Einstein or Newton. What we know is that shorter columns and larger shroud angles makes rigging stronger and that longer masts whips harder.
On the other hand, I have spent much time in small boats on stormy seas. That has educated me.
-“Is it possible that a breaker may rip out your deck fittings and leave holes”, asks the prudent navigator?
– “Definitely not,” I answer.
My small boat can never be subject to such brutish forces. She has to little mass moment and linear inertia. I know that seamen have been washed overboard from square riggers and other bigger boats. The same breakers have often hit me. That has never caused a problem. The sea is not selective. It hits everything with the same force, the rigging as well as me. If the breakers had the force to rip out my deck fittings they would have killed me long ago.
Sharpii2 says the fittings need to be strong enough to capsize the boat. Of course, that goes without saying. I am not building a toy. I am building a boat for long term, heavy duty cruising. My fittings will be strong enough to lift a boat ten times as heavy. Not only to lift it, but also to resist the dynamic forces necessary to stop a drop. Everything on my boat is solidly anchored. The deck has a sandwich core 3 cm thick. The reinforcements are spread out to a diameter of 30 cm good enough for a pull of 20 or 30 tons. So far my boats has had no problems to stand up against the elements. I see no reason why this boat should be less strong, on the contrary. I am learning all the time.
I will not worry. I will sleep deep and well even during the strongest storms because I know that if a breaker capsize her she will come up proud, happy and smiling.

With Respect and friendship, Yrvind.


Henry Ford said: “If I had asked people what they wanted, they would have said, faster horses.”
First he built cars with people sitting outside. On rainy days that was wet and uncomfortable so he added a cabin with windows. Then came the windscreen wiper. Today windscreen washers supplement them.
Let nature be your guide. Complicate things and you will be successful. Even the simplest cell is more complicated than a boat. The KISS principle is rubbish. The trick is not to make a new construction simple but functional. My guiding principle is utility. Building a nine feet pivoting mast is no rocket science. A 75 year old pensioner can do it with simple tools.
Its complexity is in the beholders eye. Some observers get confused when they see something unconventional. To calm their minds they call it complicated. The same people outfit their boats with outboard engines, electronic steering systems, water makers and induction cookers. They are so blinded by these mass produced products they do not realize that they are much more complicated than my homemade mast.
Optimizing each subsystem independently will not lead to a good boat. Of course, non-pivoting masts would be simpler, but then the whole system, the boat, would be more complicated. I would have less trim options. With the planned rig it will be very easy to change from lee helm to weather helm. Hopefully the result is that my boat will steer herself without electronic steering systems or wind vane self-steering gear.
I do not think that I ever will convince conservative sailors of the beauty of my rig. They suffer the same mental blocks that Max Planck observed a hundred years ago. Resigned he remarked: A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it. Still, I wish my critics a long healthy life.


Sharpii2 have pointed out that when the masts are not vertical they are acting like a crane boom -true. I like to thank him for that comment. I welcome critics because I often make mistakes and forget details that can have dire consequences. It was a good observation.
However I do not worry and it is for two reasons. One, I do not agree, I do not think that it will put a lot of bending stress on the mast and tremendous stress on the pivoting axle and the locking pin. After all, Yrvind Tens masts are not longer than an oar. Small boats do not attract big forces because of the square cube law. Sure, things break even on small boats but that’s mostly a question of dimensioning and can easily be fixed.
The second reason is that when the wind becomes strong I am going to reduce the forces on the mast and support her.
I reef the sail. That brings the yard down to a position six feet above the fulcrum. At that point on the mast there is a fitting to which I tie it with a string. Next I slack the halyard, releasing the compression. At that moment the bowstring effect is no more. True, the wind force is still acting strongly on the reefed sail. However its leverage is now only six feet.
To break things you need leverage. Take a match, say 4 cm long and break it, no problem. Break it again, OK. Now its only 1 cm long and it starts to get hard because you do not get a grip. You have no leverage. Most catastrophic scenarios come from big boats disasters. Small boats are different. They are more resilient. Other laws apply.
Still I am a man of the belt and suspenders approach. When the wind gets stronger and the seas start to break I snug things down and beef them up. I will then support the mast with an eight feet long spar. I will attach one end to the mast at the height of the yard, six feet up. The lower end will be fastened near the root of the other mast on the axis of the fulcrums. With that geometry the mast and spar can be rotated for and aft as a unit. Thus the mast is always supported athwartships. Fore and aft support comes from ropes.
If this sounds complicated and confusing I assure you, it is less difficult than setting a spinnaker pole.

Below is a pictures of the 1/8 scale model with this arrangement. Click once or twice to enlarge.

Above mast in aft position, weather helm

Above mast in aft position, weather helm

Above mast forward position, lee helm.

laminating the centerboard slot.


To be continued…

Regards Yrvind.


Boat ideal will have leeboard. Thinking aboat leeboard has changed my mind. I have decided to have leeboard on Yrvind Ten also. Ocean going boats do not have leeboard, but traditionally ocean going boats are big structures and lika all structures subject to Gallileos square cube law. Becouse of the square cube law a small boat do not have to be simular to a big one. In fact its a big mistake to build a small boat simular to a big one. Its against the laws of nature. Bugs understand that. They to smart to try to imitate vertibrates. Each one to its own scale.

The present project will then teach me much about them. Good for the next boat. The upcoming circumnavigation will be a lot of down wind sailing. Thats were leeboards excel. Downwind a keel is really bad a centerboard better but there is still the slot causing turbulence. Then the control ropes. Traditionally there is only one rope, an uphaul. but if the boat is going to be capsize-proof you need also a down-haul to control the board in all positions. For piece of mind. I have not got these mechanism to work to my satisfaction. This is not the first time I change my mind regarding centerboards. Bris had one to beginn with Yrvind.com started with a centerboard, then a daggerboard I scarped boath of them. Centerboard worked fine for me on Bris- Amphibie, a daggerboard worked fine for me on Duga.

Leebards will also give me much more space in the saloon.

I am avare that leeboards have its own sets of problem. I will try to solve them later.

Below are some pictures. click once or twice to enlarge.

Above the 15 kilo scrapped centerboard.

Above. The centerboard case cut off above the storage.

Above the turbulence causing opening for the centerboard.

Above the turbulent causing centerboard opening starting to be plugged.

To be continued…

Regards Yrvind