BRIS-SEXTANT FOR SALE

BELOW ME WITH MY SEXTANT

ILLUSTRATION MARTIN MÖRCK

THE DIMENSIONS OF MY SEXTANT

THE DOUBLE AND QUADRUPLE REFLECTIONS IN MY SEXTANT

WHEN THE SEXTANT IS ATTACHED TO MY GLASSES I GET AN ABSOLUTELY STEADY VIEW AND BOTH HANDS FREE AS THE BRIS-SEXTANT NEEDS NO ADJUSTMENTS


PHOTO JONAS EKBLAD
VIEW FROM THE SIDE


PHOTO JONAS EKBLAD
BRIS-SEXTANTS FOR SALE

1997 I produced a small altitude measurement instrument as a back up to my sextant. I soon realised that other sailors also could use it and that it can serve as a pedagogical toy for those interested in astro-navigation and that it makes a nice birthday gift. When the international yachting press published articles about my invention Cassen and Plath in Germany and Celestair in the USA started to sell them for me, but commercial production was boring so I only made a few before going back to mess around with my boats.

That is now many years ago. Today I need money to help finance my present project; therefore I will sell a limited number to private citizens. If you are one of those individuals who like to own, or give away, a unique BRIS-SEXTANT, please phone me, Swedish time 2000 to 2200 at +46 490 21530.

Here are some salient facts about my instrument.
It is smaller than most people’s thumbnails. Its weight is 3 grams or less than one eight of an ounce.

The common sextant consists of many parts, some moving; it is complicated and delicate and has a very accurate analogue scale. The BRIS-SEXTANT has no moving parts and no scale. It consists of carefully dimensioned spacers and a number of beam splitters, glued together to a unit with a specially formulated epoxy.

When a ray from the sun is double and quadruple-reflected between three beam splitters, three bright and five less bright images of the sun appears on the horizon as seen through the instrument.

I have built BRIS-SEXTANTS with higher number of beam splitters, they increase the numbers of the images in a combinatorial way. It is a fascinating exercise, but personally I prefer the three beam splitter sextant for its simplicity in looks and image pattern.

To find ones position at sea, in a small rocking boat, with the help of the sun, its altitude above the horizon has to be measured, from the top of a wave and during that limited time when the boat balances on the top of a wave. The measured error should, preferable, be not more than a minute of a degree. The BRIS-SEXTANT makes that possible by keeping the image of the sun steady on the horizon however much the boats rocks.

This amazing, inbuilt, freedom from change and variation is due to, that the images of the sun is always created by an even number of reflections. When the boat heals one way or the other, the first beam splitter reflects the image away from the horizon, but at the same instant, its mate, the second beam splitter which is glued to the first one moves the same distance in tandem, picks up the light beam and reflects it back to exactly the same position, free from change and variation. The impressive result is constancy. The principle is old and well proven. Radar reflectors and periscopes are other double reflecting devices that work equally well even though the angles of operation changes.

But there are more to angle measurements than constancy. It is not an easy art. Every angle consists of two lines and their intersection. The surveyor has to align his instrument first with one line then with the second. Early navigational instrument like the cross-staff also required the navigator to look in two different directions before the angle could be determined. This is of course time consuming and not suited for marine use as an altitude can only be measured during the limited time the boat is on the top of a wave. The sextant has changed all that. The instrument brings the sun down to the horizon so that the navigator can see the two endpoints of the angle he measures in one and the same placer.

The BRIS-SEXTANT has no scale, nor any mowing parts. It cannot be adjusted and there is no need to, because I chose simplicity over universality.
To explain how it works I will use a metaphor. A balance compares the unknown weight to a standard weight, a spring scale measures weight by the distance a spring deflects under its load. The ordinary sextant has a very precise scale engraved upon its arc. Its readout is analogical like the spring scale

The BRIS-SEXTANT has no scale; its readout is a bit like a balance, it compares the unknown quantity to a standard calibrated quantity.
In the case of the three beam splitter instrument each of the eight images of the sun are discrete standard calibrated quantities.
The business of the sun is to rise in the morning and set in the evening. When doing this she is pulling the images, created by the BRIS-SEXTANT, behind her like pearls on a string. All the observer has to do is to time them as they reach the horizon.

An evident but little realised fact is that two times a day you can determine the suns altitude without a sextant. Those two times are at the sunrise and at the sunset when the suns altitude is, of course, 0 degrees. With two timed observations of altitude you can calculate your position.

An observer using the ordinary sextant brings the sun down the sun to the horizon with the help of the index arm. Thereby he is creating an artificial sunrise or sunset. The instrument shows you how many degrees the sun has been lowered. Sextants are in fact sunset and sunrise repeaters.

Before you can measure the altitude with the BRIS-SEXTANT, all you have to do is to calibrate the instrument and it is no more difficult than taking an ordinary sight.

Three magnitudes are connected by equations. They are, time, position and the altitude of the sun. If two of them are known, the third can be calculated. To find the constants of the BRIS-SEXTANT, observe from a known position the horizon below the sun, through the BRIS-SEXTANT, keep it close to your eye, like when you look through a keyhole, never up at the sun. Take your time; watch as one of the images is getting closer and closer to the horizon. When the bottom limb or top limb or the centre of the sun is exactly on the horizon take the time. That done, use the time and your position to calculate the images constant, which is the suns altitude. Repeat the procedure for the other images. Make a table of the results. Later you can use the calibrated altitudes and time to calculate your position.
There are some relations between the constants. The difference between the suns upper and lower limb is obviously the suns diameter which is on the average 32 minutes of an arc.
If the three bright images are A, B and C and C is the biggest angle then A+B=C. The five less bright angles are 2A, 2B, 2C, A+C, B+C.

Because you have just determined the altitudes of the eight images by calibration and as the instrument has no moving parts there can be no errors, adjustable or nonadjustable. There are not even mirrors to resilver.

Sight corrections like index error, dip of horizon, refraction, semi diameter, parallax and so on are an important part of ordinary astro-navigation. Forget that when using a BRIS-SEXTANT. The reason is if you deduct them when correcting the sextant you have to add them when taking the sight. If you are very fussy you can note the time of year when you do the calibration because there is a small correction for the suns diameter and an even smaller for her parallax, but that’s for the advanced user.

An ordinary sextant takes up as much useful space as eight oranges or more, but if you don’t mind that and that it is a delicate instrument craving adjustments, it is a more universal instrument and unlike the BRIS-SEXTANT can be used to take a noon sight without a time piece to determine your latitude. The BRIS-SEXTANT is not meant to replace the ordinary sextant or GPS but to be used as a backup.
The BRIS-SEXTANT has no telescope, but in the hands of a good human eye, mine, I have measured altitudes time after time, from the steady platform of a beach, to an accuracy of one tenth of a minute of arc.

In a clean BRIS-SEXTANT you can see eight images of the sun. From each sun you can get tree readings, the lower limb on the horizon, the upper limb on the horizon and the centre on the horizon. Eight times three is twenty-four. You can make these same observations twice a day, in the morning when the sun rises and in the evening when the sun sets. In total with a BRIS-SEXTANT, in clear weather, you can make forty-eight observations each day. That is enough to make my small back-up instrument worth while.

As a bonus because the BRIS-SEXTANT is so small and light you can attach her to your glasses. There are two major advantages to this. First the image becomes dead steady. It is like watching a sunset without an instrument. It makes the observations very much easier. Second you got both your hands free so that you instantly can write down the time. The timing has to be done to the second, if accuracy is desired.

Don’t hesitate phone me and order your unique BRIS-SEXTANT. Swedish time 2000 to 2200 most days. Phone number +46 490 21530.

So far so good . . .

By Beppe Backlund, Webmaster

Sven has celebrated his 70 year birthday, 22 of April. His ordinary plan was to be ready with his boat at this very special day. Now he realized that the party have to wait and the start of his long and hazardous journey to Cap Horn will be at a later time. Building a boat, even a small one, will take time and as with a lot of other big projects – they will be delayed. We – his friends – are in fact not so disappointed about that, as we now have the opportunity to enjoy his very special person even the coming year.

The 70 year birthday event was held in his own workshop. 40 or more people where visiting him under the two hours he let the door open. Almost every one had his own question to ask. Sven answered them polite in his special manner. He also jumped into the boat in purpose to show how he take place inside. As you can see on some of the pictures below – there isn´t much headroom.

The boat itself looks very special with it´s Chinerunner concept. Sven decided to use this technique instead of an conventional keel, as he have become inspired of the American small boat designer Matt Layden. For Me, the rudder construction looks most impressive. A huge rudder almost reaching the ceiling in his workshop, now pointing 180 degrees from it´s normal position. Sven explain – the rudder is a part of the lateral plane and need to be that size. And I also like to be able to steer the boat and have good control when she´s running the heavy waves in the South Atlantic. When some of his birthday congratulators realized that he was going to ride such a big waves with this little tiny boat, they get shocked. But Sven assured – no problems, a small boat like this is more secure then a big one.

So when the two hours audience was over We got a clear view over the project, both the philosophy behind and how Sven is constructing and building the boat. And I would like to say – So far so good – with Sven and his new boat.



THE CHINERUNNERS: MATT SPEAKS

Matt with Enigma on the long Watertribe race around Florida, which he was leading most of the time. The chinerunners are clearly visible, the wheels are attached to them.

Hera is a copy of the Small Craft Advisor interview with Matt about the chinerunners. It is good reading. My copying is less good. You have to zoom or click once or twice on the different pictures to make the size of the text big enough to be readable, but its worth the trubble. Enjoy.





RUDDER

I like to have a big rudder to help prevent leeway. I also like to have it far back when surfing down the big waves in the roaring forties and screaming fifties. The when getting inshore I like to reduce my draft to and to be able to pull the boat up the beach. Finally the rudder is going to steer the boat while I sleep. I dont like selfsteering devices as the are complicated. I have good experiences with sheet to tiller system and also to get the boat to steer itself by its own balance. With sheet to tiller system a sheet is connected to the tiller to give feedback. In my design I do not have a tiller instead stearing lines are directly connected to hornlike extensions on the rudder and rudderblade as the below pictures will show. A threaded rod keeps them together. It is however very important that the rod is perpendicular to the surfaces wich must be very flat. This is how I have done it:
I covered a glass plate with teflon.

Click on the pictures to make them bigger

This is the surface of the rudderhead I vanted to be flat

I mix NM-epoxy with filler

I spread the mixture on the rudderhead

I put the rudderhead on the tefloncovered glassplate. I put on a lot of leadweights to squise out the mixture. After the rudderhead I repeated it on the rudderblade.

I made a 300 millimeter long 30 mm diameter drillbit and drilled a whole as perpendicular I could.

I had made a carbonfiber pipe to put inside the oversize hole. I closed the bottom part of the pipe with butylrubber.

I had made a guide by welding a rod to steelplate and turning the plate in a lathe thus assuring a 90 degree angle. I turned the rudderhead 180 degrees. I put in the rod of the guide in the pipe thus making being 90 degrees to the surface. What you see in the picture below is rod coming up inside the carbonpipe. In the space between it and the oversize hole I poor epoxy to fix it.

Everything worked out. Here is the rudder in the upplifted position. Thanks to the possibility to tilt up the rudder 180 degrees it does not stick out behind the boat were it can be damaged in port.

Here is the rudder in the down position.

Here is the tackle I will steer with.

THE BRONZE KEEL

After much hesitation I decided to increase the draft of Yrvind by 3.2 centimeter 1 1/4 inch and reduce her load carrying capacity by 120 kilos. I would gain better stability. Watching grib weather files for Cape Horn daily for over a year has made me worried about its storm. Also I would get a very strong antifouling bottom if I made the keel of bronze. Here I would like to thank Carol of the Copper Development Association very much for paitiently ansver my many silly questions.
The foundry BLOMSTERMÅLA METALLGJUTERI did now as with the leadweights an excellent job. To celebrate I will give talk at TIMMERNABBEN YACHT CLUB tuesday 7 of April 1900 welcome.

Below are some pictures. I started to make a pattern. I used square cut divinycell and glassfibre and NM-epoxy to make a pattern Martin gave me advice. Thank You.

As the pattern was long and flexible I made a pattern for the pattern of plywood to check it in the foundry.

First we put the pattern on a flat surface backed by sand.

Then we put the bottle arond her.

Next we packed her with moulding sand.

Next comes feeders and raisers.

More foundry sand is packed.

The mould is split the pattern removed and the surfaceces are blackend with graphit. The solvent is burnt of.

The bronze is melted.

Then poured.

The whole thing has to cool for several hours.

Then still pretty hot it is taken apart.

Now I can see one surface of my keel. It is still very hot but its starting to snow so it cools it quicker. Still I have to go for lunch before its cool enough to handle.

It weighs 126 kilos pretty close to my estimated 120. It has also shrunk 1 1/2 % But that is no problem. After cutting of the feeders and raisers I put the keel in my car and I drive one and a half houer north to Västervik where I unload her.

Next I start to get a smouth surface on her. She now looks nice and I am proud of my decision to make a bronze keel. To be continued.

A FUNNY THING ABOUT TIME

Last summer 22 April my 70 year birthday seamed so far away. Now its only one month away. My original plan was to launch the boat at my birthday and have a party. Now I realize that that have to wait – it seams only the gods know when the boat will be ready. The party and the launching have to wait.

However anyone genuinely interested in small boats are welcome to Baumansgatan 4 here in Västervik on 22 of April between 16 and 18 hours and have a look at the work so far. There will be no cakes or drinks and I will not accept any birthday gifts, but I will talk and ansver questions and you can take a picture of the boat.

THE CHANNELS

Channels are in a nautical sense the ledges projecting from a sailing ships side to spread the shrouds and to keep them clear of the gunwales. Its an alteration of obsolete chain wale. It seems that channels in the nautical sense are now also obsolete. Time is passing. I use them however, because I hope to be able to lean my mast 30 degrees side vise. That will achieve a few things like giving the boat more stability when the mast is to windward.

Theoretically, placing a lead weight on the mast top would increase stability even more.

In light wind the mast can be made to lean to lee stopping stopping the sails from flapping as gravity will keep them down.

Also more sail area can be projected to the wind and the sails will be lifting instead of pressing the boat down. Also bringing the sails to windward will give her lee helm. Keeping them to lee will give weather helm.

A tilting mast gives a sailor many possibilities to experiment with his rig.

However it has been a time consuming job with many different operations. I started by gluing a piece of Divinycell to the hull. I fixed it with wooden jigs.

(click on the pictures to make them bigger)

Then I put some glass fiber below were the metal fitting was going to be.

Then I put a shelf to fix the metalfitting

Here is the metal fitting and I measure how much unidirectional glass I will need. Al the glass work is done with NM-epoxy. The pipe (wrapped in Marström tape for release) is to hold down the UD-fibre.

Here is the result.

Now I am building up the shape with more Divinycell. Vertical athwartships pieces of glass is inserted between to make the structure rigid to avoid pealing.

Lead weights are employed to compact it and squeeze out any voids.

The final product have a lot of gluing surface and in theory should be good for twenty tons pull. A fair margin of safety even for Cape Horn.

Here are all six channels looking aft. I only really need the two forward ones but the other strong pints are good to have when experimenting with different sail sets and for lifting the boat. The aft one is for yuloh work. They give a place to put a foot athwartships and a place for the rope.

Here is a view from aft.

YRVINDS LATCH MECHANISM

Below part of the aft cabin with the latch system in the aft starboard corner of the hatch. (I only do one corner on the mock up)

Below close up of the latch system.

Below Hatch open, close up of coaming and the green spectra line and its holder. The good thing with this system is that it gives a lot of closing power, its fast and its out of the way with the hatch open. Nothing to snag and chafe. Coastwise cruising one may have to stand a long time in the hatch in heavy weather. Then when tired and weary, one thing one I can do without is a latch digging in to my flesh.

THE HATCH & MORE FITTINGS

Today Börje has been here with a load of good things. Here we are trying the toggle of the gooseneck on the mast.

Below the toggle and its pin.

Below the ball and the mastfoot. There is two sets as the forespare also has its ball and mastfoot.

Below is the dead eyes. The mast can be made to tilt to windward. The mechanism for that are dead eyes. Usually dead eyes has three holes. I use two holes and a spectra line. Just before coming about I release the windward shroud and the rig falls over to leeward in a controlled manner. With three holes in the dead eyes I feel there would be unnecessarily much line and friction.

While Börje have been working on the fittings I have been making a mock up of the hatch. Below is the inner coaming.

Below can be seen the gasket around the inner coaming, the flat pieces of the outer coaming, the rope guiding of the hatch with the hatch in its foreward position.

Below the hatch in closed position looking aft. There are two bends in the roof of the deck house. I will only keep the aft as the foreward bend makes the attachment point of the rope to high.

MOCK UP OF DECKHOUSE

There are many things to consider when designing a boat bound for Cape Horn with an old skipper who does not like to get wet and cold, but now finally I think I got most things right.

Through the windows in the aft cabin I will have a good view of the surrounding seascape from my comfortable chair.

From the bunk in my bedroom will have a good look at the sail.

There is ample place for ventilators and ducts of my waterproof system so that no water will enter even when the boat is upside down.

I have designed a hatch closing system on the principle of the Highfield lever. There is one latch out of the way below each of four corners of the hatch. From the latches a Spectra rope goes to a hook in the hatch which then can be made to press against a deep EPDM cell rubber gasket to the desired pressure and tightness. The good things with this system is that when the hatch is open there is nothing in the rim which chafes or snags.

Another advantages is that I can, in heavy weather have a modified kayak spray shirt permanently mounted on the hatch rim because the Spectra ropes can come through small waterproof holes is the spray shirt and I can from inside the spray shirt put the loops of the ropes on the hooks. I can therefore get inside the, to the boat attached spray shirt before before I open the hatch. In principle not one drop of water can enter the boat.

The mast is only 75 centimeter 2´6´´ in front of the hatch and therefore easily be reached without going on deck. The spar in the picture is a mock up of the mast.

The hatch is 40 x 45 centimeter a size I used on my first Bris in which I cruised many years. It is a size which suits me well.

I will be able to open the aft window in good weather to get better ventilation. It is closed tightened from the outside by bolts. Also the outside of the aft window is very easily reached from the hatch.
From the hatch I can also reach the water by leaning overboard. This is convenient when washing up and brushing my teeth.

I realize that my description may not be very clear but more pictures will follow as work progress.