Trou­bleshoot­ing a tiller pi­lot

After his boat ex­e­cutes an un­ex­pected hard-over turn, Paul Newell di­ag­noses and re­pairs a prob­lem with his tiller pi­lot

Practical Boat Owner - - Contents - Mary Lou

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Ien­joy sail­ing my 1981 Virgo Voy­ager around the coast of Northum­ber­land and am of­ten sin­gle-handed, so my Ray­ma­rine ST1000 tiller pi­lot is an es­sen­tial mem­ber of the crew. He came with the boat when I bought her, and I chris­tened him ‘Lee’ (as in Lee Helm).

Last Oc­to­ber I mo­tored out of the River Co­quet and set Lee to work steer­ing while I went up to the mast to raise sail. Sud­denly the boat made a sharp and un­ex­pected turn off the wind. Re­turn­ing to the cock­pit, I ex­pected to find that the au­topi­lot had jumped off the spigot on the tiller. To my sur­prise, the push rod was still at­tached but at full ex­ten­sion, caus­ing the sharp turn.

I re­set ev­ery­thing and put the au­topi­lot back on auto. Ev­ery­thing seemed nor­mal so I went back to the mast, only to have a re­peat of the hard-over turn. Ob­vi­ously Lee wasn’t feel­ing his usual, de­pend­able self, and I sent him down be­low for the rest of the day. When I got him home, some time later, it be­came ob­vi­ous that there was a prob­lem with the in­ter­nal flux gate com­pass. If I held the au­topi­lot at cer­tain an­gles to the hor­i­zon­tal it would dis­play the cor­rect com­pass head­ing, but as I tilted it gen­tly from side to side it would sud­denly jump to a head­ing of 233° and freeze. Pre­sum­ably this was caus­ing the wild turns.

Un­like most mod­ern equip­ment, and de­spite the ‘no user-ser­vice­able parts’ warn­ing in the man­ual, the ST1000 does seem to have been built with the rea­son­able ex­pec­ta­tion of DIY re­pairs. I have cer­tainly had mine apart pre­vi­ously to re­place the mo­tor – a rel­a­tively straight­for­ward job. There are eight crosshead screws that hold

the two halves of the case to­gether and then a few more screws to re­lease the main cir­cuit board that sits over the top of the lead screw/push rod mech­a­nism.

With the push rod care­fully lifted clear there is ac­cess to the flux­gate com­pass that sits in the lower half of the case in a plas­tic gim­bal mount. The com­pass is con­nected to the main cir­cuit board with a flat rib­bon ca­ble, and I no­ticed this had a sus­pi­cious­look­ing mark across it where it passes over the plas­tic gim­bal mount. In­spec­tion with a mag­ni­fy­ing glass con­firmed my thoughts. As the com­pass swung in its gim­bal the rib­bon ca­ble had chafed on the edge, and over the years this had even­tu­ally bro­ken some of the thin copper tracks in the ca­ble.

A bit of Googling con­vinced me that re­pair­ing the rib­bon ca­ble it­self was a non-starter. I could ob­tain a re­place­ment com­pass unit for around £90 from eBay, but be­ing a York­shire­man I was re­luc­tant to lay out hard brass just yet. Cast­ing around the work­shop scrap bin, I found an old dim­mer switch that had gone pop some time ago. The cir­cuit board had just what I was look­ing for: a coil of thin, enam­elled copper wire. I could use this to ‘piece out’ the rib­bon ca­ble con­duc­tors, but it would still be thin and flex­i­ble enough to not in­ter­fere with the com­pass move­ment.

I care­fully un­rolled about 30cm (12in) of the enam­elled copper wire and cut a few lengths that would reach from the com­pass to the con­nec­tor at the other end of the rib­bon ca­ble. Us­ing some very fine emery pa­per I re­moved the enamel from the ends of the wire and, with a fine-tipped sol­der­ing iron, I sol­dered the wire to the com­pass at one end and the con­nec­tor at the other. I used an­other length of the wire to piece out the sec­ond bro­ken con­nec­tor.

Plug­ging the com­pass back into the main board and pow­er­ing up, I was re­lieved to see that the dis­play was show­ing the com­pass head­ing cor­rectly. I then put ev­ery­thing back to­gether and tested that the com­pass was still work­ing and didn’t lock any more as I tilted it. Be­fore re­assem­bly I also put a piece of clear plas­tic tape over the site of the chaf­ing to pre­vent any fur­ther dam­age to the re­main­ing copper tracks.

I am pleased to re­port that on my first trip of the new sea­son Lee steered the boat fault­lessly for eight hours, both un­der sail and us­ing the en­gine. As men­tioned ear­lier, my ST1000 came with the boat when I bought her, so it is at least 12 years old. It tends to have a hard life in the cock­pit, but its sim­ple de­sign seems to stand up quite well. I am hop­ing that my com­pass re­pair will al­low Lee to carry on crew­ing for me for a few more years at least. Oh, and the cost of the re­pair? Zero!

Through­out PBO's golden an­niver­sary year, the win­ning Prac­ti­cal Projects ar­ti­cle will be re­warded with a pair of Spin­lock’s Lume-On blad­der lights. These are tiny LED lights that at­tach un­der­neath the blad­der of any life­jacket: when ac­ti­vated, Lume-On lights use the blad­der as a dif­fuser, turn­ing the whole life­jacket into a glowing light, and are de­signed to work along­side ex­ist­ing life­jacket lights. Lume-On lights were named joint over­all win­ner of the pres­ti­gious 2015 DAME de­sign award com­pe­ti­tion: the DAME jury were im­pressed with the lights’ clev­er­ness of thought, sim­plic­ity of ap­pli­ca­tion and very ac­ces­si­ble cost. Priced at £14.94 a pair.

ABOVE The rib­bon ca­ble had chafed RIGHT The re­place­ment copper wire was sol­dered to the con­nec­tor at one end and the com­pass at the other

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