Author: Yrvind

I keep working on the C.B. I like to make it as good as I can. It is excessive, but in a world were yachts are done to minimum standard- except the finish which Neptune dont care about- it is nice to have something to be proud of. Besides it is also nice when you are out there to know that what ever the sea will throw at you you do not have to worry but can sleep peacefully.

The C.B. is now shaped. The trailing edge is very thin therefore I have shaved away the Divinycell there and replaced it with epoxy thickened with migrofibers.

I have also made a bronze bearing for the axis. The pin diameter will be 18 mm close to 3/4 inch.

The below picture shows the shaped C.B. Click once or twice to enlarge.

The below picture shows the shaved away Divinycell.

The below picture shows the pin bronze bearing. Some gassfibre reenforcement can be seen in the hole, more will be addded higher up.

The below picture shows the bronze pin bearing epoxy-glued in position. Later some Divinycell will be routed out and replaced with glass fibre reenforcement.

To be continued…

Regards Yrvind.

I am still working on the C.B. The control lines, upphaul and downhaul needs a reliabel point of attachment. The distance from that point to the rollers should be as small as possible. It is also important that the knot or splice is beyond the fitting as not to add to the lenght. A knot two inches long on each side of the fitting means four inches and if there are two fittings worse. It is worse becouse the whole centerboard case will be that much bigger and if you build a ten feet ocean going  boat it is nice to conserve space.

The following pictures show my solution. Click once or twice to enlarge.

The above shows a  thimble I made of bronze. I will encapsulate it on the top of the C.B. the surface is increased to get more contact with the epoxy. One more square centimeter means 300 kilo more load can be absorbed.

The hole is just big enough for two 10 mm ropes to pass through. A figure eight knot acts as a stop.

The fitting in its position ready to take the thickend glassfibre reenforced epoxy. The blue stuff is styrofoam preventing the epoxy to fill the space where the rope  and the knot later will be.

To be continued…

Regards Yrvind.

This is the final mock up. Small corrections will be made and transfered to the real C.B.-case. On the aft top end a step will be made. It is the inspection hatch that fills two functions. Click once or twice to enlarge picture.

This is the same motif seen from a different angle. The aluminum profil indicates the top of the deck house.

Above is a picture of the pattern of the NACA-profil that will guide me shaping the C.B. The hydrodynamic properties are compromised in favour of strenght. To get a good nos radie I have chosen a NACA 0020, that is 20% thick, nos radie 8.6 mm. The real C.B. is 43 mm without lamination. The virtuel chord is therefore 215 mm. The chord of thereal  C.B. is more than 700 mm. I have therefore split the profile at its maximum thickness, that is 30% from the leading edge and inserted a parrallel section of the missing lenght.

To be continued…

Regards Yrvind

The surface shape of the C.B. is now cut. Time for one more mock up. Everything was OK in the hull. However now I had to figure out how the control lines were going to find their way to the deck. I did not want them inside the boat becouse that would bring in water in one form or other. The original plan was to conduct the down-haul in a pipe straight up to the top of the deck-house. But there was the sliding hatch making that impossible. It had to come out foreward of the deck-house.

Picture one show the C.B. in the down position. click once or twice to enlarge.

Picture two shows the C.B in the up position.

Picture 3 shows the drawing of the sliding hatch. It is a pen drawing look close.

Picture 4 shows a piece of plywood around the roller preventing the rope from getting stuck between the roller and the C.B.-case. One of these anti-stuck pieces on each side of the C.B.-case.

Picture 5 shows the dawn-haul roller. It has a much bigger diameter. The reason is to lift up the rope some centimeters to clear the top of the C.B. Here the C.B. is in the down position. The lower rope dissapears up through the deck when the board is raised. It is the other rope that has to stay clear as the board mowes foreward.

For service, to change rope etc. there is a slot in the deck leading to the C.B.-case. At the back above the big diameter roller there is a service hatch.

To bee continued…

Regards Yrvind.

At an other front I am working on the C.B.

It is very easy to get an symmetrical profile working with plywood becouse you can use one of the layers as centerplane. Working with composite and Divinycell is a different matter. Au pif I decided that the thickness of my C.B. should be 4 cm. Instead of trying to shape 4 cm Divinycell I glued tvo 2 cm pieces together. In the middle I put three layers of 450 gram glassfiber. Also I made reenforcment for the axis, the up and downhaul and the lowest end, the one which are going to touch the ground being my echo-sounder sailing in shallow waters. Also By having glassfibre in the middle the aft end of the profile which is very thin will be stronger. Whith this layer in the middle I have a plane of reference when shaping the board.

Below are some pictures. Click once or twice on them to enlarge. First picture I have used a router to create space for the reenforcement. Routing depht is 8 mm.

Petter, a young man just mowed here is helping me, here he is laminating the reenforcments.

We are using a lot of lead to put pressure on the surface. Of course the result is much better with vacum. I should realy using that instead. Still weights are good enough. We are using about 300 kilos of lead. Had we used vacum instead we would have gotten a force equvilant to about 10000 kilos (the area being about 80×120 cm) In addition the vacum would have gotten rid of all the small air bubbles.

To be continued…

Regards Yrvind.

I had made a rough calculation of the volume of the bronze soles patterns using an estimates prismatic coefficient etc. As the have compound curvature and consists of convex and concave surfaces I was not to shore about my estimate therefore I decided to do as old Archimedes one of my idols, submerged them and measure the overfloving water. I do not have a bath-tub so I asked around. Then a freind of mine said I have a better method, I have a 3-D scanner. It is realy amazing all the new things they find out.

He kindly scanned my patterns. Each had a volume of 6.5 liters bronze density is 8.8 kilos per liter giving a total of about 110- 115 kilos just what I wanted.

Below is a picture. The top image is the scan the lower ones the crated surfaces. Click once or twice to enlarge.

By the way, the book comes in an electronic form E-bok. Se Bokus.com search for yrvind

To be continued…

Regards Yrvind.

Click once or twice on the picture to enlarge.

The book: Den unge den gamle och havet, is now in print and for sale on internet in book shops and signed copies from me and my co-author Thomas Grahn.

It is published by Swedens oldest book company Norstedts. The text on the back cover reeds in my free translation.:

Nineteen year old youth and his freind calls on Yrvind a seventy year old experienced small boat sailor to get advise for their dream cruise. After a few houers consulting they part. Weeks pass. One day Yrvind phones curious about their progress.

My freind jumpt ship, says the Captain.

You must sail single-handed, says Yrvind.

I have never been away from home for more than a week, the longest I have sailed is across to Denmark, and I have never been sailing at night.

I lend you a sextant and an inflateble. If the worst comes to the worst I give you a hand for start.

A week later Captain phones back.

Are you serious?

If you give a hundred percent I will give a hundred percent, but we must hurry, soon the authum storms are here. We got a month.

Followed by calamity howlers the odd duo departs, the old man and the youth bearing the heavy burden of being the Captain. After enduring storms, a broken down engiene, blown out sails, a leaking boat they finally exultant reach Florida after a in many ways an unique sail.

It is a practical, instructive book for people with big dreams and small budgets, enjoy.

Regards Yrvind.

I have now decided to have the masts fixt side by side, not mowing them. In the masts there will be lightning conductors. They will be earthed to bronze soles,  one on each side below the masts. In addition the bronze soles will also give some weight low down about 100 kilos for additional stability when I am low on water and food. I chose bronze for its electrical conductivity, antifouling properties and chafe resistance. the latter is important when taking the ground and touching rocks and other underwater obstacels I may encounter cruising close to the shore.

I have begunn to make the pattern from square-cut Divinycell glassfibre and NM-epoxy. I begunn by insulating the hull then putting a layer of glassfiber on top of that comes the Divinycell. I weigh it down with lead-weights. to prevent them from sliding I use sandpaper.

On top of the insulation made from household plastic wrap is the Divinycell and weights.

Here is a close-up. Click once or twice on the pictures to enlarge.

To be continued…

Regards Yrvind.

Several years ago i invented the Bris minisextant as a navigational toy and back up to the GPS. There is a video on youtube – search Yrvind.

Yesterday I got a thelephone call asking if the surfaces where coated .

There is no coating. Not on the production type nor on any experimental prototypes. It would not work on this kind of sextant.

I use ordinary flat panel glass. When I was a small child living on the windward side of a small island I noticed, and was intriged by the fact that the windows in our house was transparent in the daytime and mirrors at night when it was dark outside. I remember that I asked my grandmouther about about that very interesting and curious  fact but she could not give me an satisfactory ansver. I never forget it and thougt that one day I may have use of it. Now I now that windows are beamsplitters. 90% transparent and 10 % reflective.

In the 3-glass sextant one can see eight images of the sun. (in the 4-glass sextant many more). One of the glasses is a filter to reduce the strenght of the sun. It is very balanced not to bright not to dark. To enable the observer to see the 3 bright suns created by dubble reflections and the 5 dim suns created by quadrupple reflections at the same time. People have fat on their fingers. The fat creates fingerprints. If fat or dirt gets on the sextants optical surfaces it may reduce the transparency and only the bright suns may be seen.

If this happens the sextant should be cleaned. I use ordinary disch washing detergent. After rinsing I dry the surfaces with compressed air – oil-free compressed air. Like what people use for diving or cleaning negatives. If you do not have acces to clean compressed air try to centrifuge away the water use the cord attached to the sextant, attatch a little weight to it to gove more inertia, swing swiftly, do not hit anything.

The outer surfaces are easy. For the inner ones one can use a dentalfloss-houlder and cotton thread – do not use dental floss as it is waxed.

The sextant is glued with a specially formulated NM-epoxy that chemically reacts with the glass. You can clean with anything that does not harm epoxy and glass.

Regards Yrvind.

Today I put the main bulkhead in place. It was a good fit. Not as good as a traditional japanese boatbilder though. To get a better fit I will cheat. This is how I will get a fit perfect  down to the molecular lewel. I cut a groove on the periphery of the bulkhead with my router. The eagle-eyed reader can see it on the picture below. Click once or twice to enlarge.

Here is a close up.

Below is the bulkhead in place. Soon the wowrk of putting radius on each side and laminating it with 45×45 directional glassfibre will start.

Below is a close up of the intersection of the sheerline and the bulkhead. The groove can be seen. ( The different coulors of the Divinycell indicates its strenghts yeallow indicates 100 kilo/ meter cub grey indicates 80 kilos/ meter cub The Divinycell of the hull is 4 cm thick the Divinycell of the bulkhead is 5 cm thick)

After laminating the bulkhead in place I will suck in NM-epoxy with the healp of my vacum-pump into the groove. The epoxy will fill the space between the  periphery of the bulkhead and the hull to give a perfect fit. The periphery is 2.45 meter long and gives with radiuses and laminations a cross section of 10 cm about. This is a tremendous surface making the boat very strong. An other reason for making the bulkhead so thick is to give good insulation to my bed-room. The weight of the bulkhead is 20 kilo. The weight of the hull is 115 kilo.

To be continued…

Regards Yrvind.