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First multihull circumnavigator

Sep 25, 2007
After last issue’s navigation problem on Donald Crowhurst, I thought that I would continue to focus on 1968’s groundbreaking first solo Golden Globe Race. That event was full of some of sailing’s great characters: Bernard Moitessier, Robin Knox-Johnston, Chay Blyth, Donald Crowhurst and Nigel Tetley. Tetley was the first man to circumnavigate in a trimaran. Nowadays that wouldn’t make any headlines, but in 1968 no trimaran had ever completed such a long race. The more conservative monohull sailors thought the multihull was not seaworthy and could never compete with the standard displacement monohulls. Since those days multihulls have come to dominate long-distance racing.
 
In 1968 there were only two trimaran entries. One was the ill-fated Donald Crowhurst and the other was a man who might have won the race if not for the prevarications of Crowhurst. That man was Nigel Tetley.
 
At the time Tetley was a Lieutenant Commander in the Royal Navy. He and his wife Eve had spent the six previous years aboard their 40-foot trimaran Victress. When he heard of the Golden Globe he decided that he should enter the race. Never mind that he had no sponsor, little money and no time to build the 50-foot trimaran he wanted to sail. He couldn’t find sponsorship so he decided to race Victress, which was the family home. Victress was a 40-foot, Piver-designed trimaran rigged as a ketch. Constructed of plywood covered with fiberglass, the boat was hardly the type in which one would contemplate rounding Cape Horn. The vessel had been built in 1962 and the Tetleys had cruised extensively around Europe. The boat at the time of the race was in need of repairs and gear upgrades. At the last minute, a company that produced classical music, Music For Pleasure, took over as sponsor — on the strength of the stereo system already built into the boat. The sponsorship was announced by this headline in the Sunday Times: “Around the World in 80 Symphonies.”
 
Tetley departed England on September 16. It took him awhile to get settled into the routine of racing around the world while listening to good music and eating like a king. Tetley was a gourmand, and before the race he and his wife had prepared an almost inexhaustible supply of gourmet foods. He began the race with smoked trout and fresh fruit, with an entrée of roast chicken accompanied by Handel’s “Water Music.” It was reported that in the trade winds he began catching flying fish, which he fried in butter, serving them with Polish sausage, roast duck and smoked salmon.
 
On March 18 he sighted Cape Horn and celebrated with another fine meal. Thinking that he had to beat Crowhurst — who had never left the southern ocean — Tetley pushed his boat to where it finally began breaking up. On April 19 he crossed his outbound track, thus becoming the first trimaran to circumnavigate. But his good luck was not to last. On May 20, 1,100 miles from home and 245 days out, his port hull broke loose. He abandoned ship and was rescued by the Coast Guard. Tetley was the first man to sail solo around the world in a trimaran in record time of 179 days. He was also the first to sail a trimaran around Cape Horn. He received a consolation prize of £1,000 at the conclusion of the race. Had it not been for the fiction that Crowhurst perpetrated, forcing Tetley to push his boat beyond its limits, Tetley might have been the victor of the race instead of Knox-Johnston. Perhaps then his life would have taken a better turn. Tetley hanged himself in 1972.
 

Let’s do a celestial problem. In 1968 all the participants knew their celestial. They all used it to find their way around the world, and Tetley was spot on when he passed south of Cape Horn. He wanted to pass about five miles south of the Cape. We are at a DR of 56° 02’ S by 67° 17’ W sailing in an easterly direction. The height of eye is 10 feet and the sextant error is 2’ on the arc. There is no watch error. The sun shot is the upper limb and is taken in the a.m. before meridian passage at 11:50:10 GMT. The Hs at the time of the shot is 11° 20.8’. The day in question is March 18. We will use the 2007 Nautical Almanac. To find his distance off Cape Horn, Tetley takes an early morning sun sight. The resulting LOP will give him distance off — with any luck.

 

Questions:

A: What is the Ho?

B: What is the intercept?

 

The position of Cape Horn is at 56° S by 67° 17’ W. If you plot the sight, which I recommend, you will see how spot on Tetley was in his navigation.

 

Answer:

A: Ho is 10° 55’

B: Intercept is 7 nm toward
 
 
 
 
EXTENDED ANSWER: 
 

In this problem we have Nigel Tetley, passing Cape Horn, on the way into the south Atlantic. In order to make certain that he has enough room to maneuver, Tetley wants to clear the Cape by at least 5 nm. In order to guarantee his success, Tetley decides to take an early morning shot of the sun, as it is rising, but far enough above the horizon so that he can get an accurate shot without too much refraction. Accordingly, he waits until there is a break in the clouds and at 11hours 50 minutes 10 seconds GMT he gets a upper limb shot of the sun. He knows, as do all practitioners of the art of celestial navigation, that the LOP of the sight is perpendicular to the azimuth, so he knows that by taking a shot where the azimuth bears east that he will get an LOP that will be in a northerly direction. Since he wants to be south of Cape Horn, what he actually doing is finding his distance off by shooting an early morning sun sight. The facts are as follows: We are at a DR of 56° 02’ S by 67° 17’ W. Height of Eye is 10 feet and the sextant error is 2’ ON. The Hs at the time of the shot is 11° 20.8’, and the day is March 18. What is the Ho?

To find the Ho we have to reduce the Hs-standard operating procedure in any and all celestial sights. What we are doing is correcting the sight for refraction, semi-diameter and parallax, in other words we are putting ourselves in the exact center of the celestial sphere and not on the surface of the earth, fortunately we can achieve this mathematically.

 

Hs      11° 20.8’

-dip             3.1’

-IC              2.0’

Ha      11° 15.7’

3rd cor -    20.7’

Ho 10° 55.0’

 

The only things to pay careful attention to here is the fact that the Index Correction is On the arc so that means it has to be subtracted (remember when you’re on, you’re off?) and the fact that are working with an Upper Limb sight so the corrections are subtracted instead of added as in a Lower limb sight. I personally prefer to take lower limb sights but it is good practice to shot both limbs in order to be comfortable with the procedure. This comes in handy when shooting the moon.

 

 To find the intercept we have to find the LHA of the sun and then enter into the sight reduction tables – in this instance vol.3 HO 249:

 

GHA at 11 hours 342° 57.4’

50 min 10 sec          12° 32.5’

GHA                       355° 29.9’

-Ass Long                  67° 29.9’

LHA                         288°

 

 

While we are poking around in the NA lets get the declination of the sun at the time of the sight. Dec is S 1° 00.4’ with d of 1.0’ which converts to 0.8’. Now we can tell by inspection of the declination tables that the declination is decreasing so the 0.8’ is subtracted from the dec. thus:

 

 

Dec.   S 1° 00.4’

-                                        0.8’

 

Dec S 0° 59.6’

 

Now we enter HO 249 Vol 3 to page of 56° latitude (this is our assumed latitude) and we go to tables where declination is 0-14° Same name as latitude. We find the following under 0° declination and 288° LHA

 

Hc 9° 57’     d+51       Z105°

 

We go to Table 5 for corrected minutes of declination which in this case is 60’. I got that from the declination for 59.6’. The table 5 correction is added to the Hc as indicated in the tables

 

Hc  9° 57’

+         51’

corrected Hc 10° 48’

Ho                  10° 55’

Intercept is 7 nm Toward. Remember HO MO TOW, which is to say that when the HO is greater than the Hc the Intercept is moved toward the direction of the celestial object. By the way also notice that at the bottom of the page in the sight reduction table it states that if in the southern hemisphere and if LHA is greater than 180° that Zn =180-Z thus the true bearing of the sun at the time of the sight is actually 180°-105° = 75°

 

For further edification and delight you all should plot this sight. Tetley was damned good!

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