Downloads

TRUE WIND CALCULATOR

When we made our Pacific crossing, the SSB radio nets and SailMail position reporting services we used, such as YOTREPS, all wanted information on our current weather.  Not a problem for the most part but true wind was always a guess since our wind instrument only showed apparent wind.  The few times I actually calculated true wind were more than enough to show that I wasn't a very good guesser.  Much to my chagrin.  It was an unacceptable blow to my pride, so I fired up Excel and wrote a brief spreadsheet app to make calculating true wind easy.  Download your copy HERE.

ENGINE ALIGNMENT

The next task after rebuilding our engine and getting it back into the boat was to get it properly aligned with the propeller shaft.  Since we had also replaced the engine mounts, it wasn't going to be even close at the start and the best way of going about it wasn't immediately apparent, at least to this novice. 

The trial-and-error, brute force approach was one obvious possibility.   The prospect of climbing down into the bilge, wedging my old and overweight body into the proper position and manipulating feeler gauges at the coupling, climbing out to shift the engine around by main force (hammers, tongs, other implements of destruction) ... rinse, lather, repeat ... was daunting to say the least.  I knew there'd be some of that, inevitably, but trial-and-error meant that I might be at it for a very long time.  Indeed, I'd heard stories about this process sometimes going on for days.

I reckoned that there had to be a better way.  So off I went to cruise the internet, perhaps much as you're doing here, to seek a better engine alignment procedure.  And I found it!  It was an article by a fellow named Jack Harden, titled "Get In Line", on Transmission Marine Inc.'s web site, who've kindly given me permission to include a copy here.  This article outlined how a series of measurements, taken at the coupling, could not only measure engine-to-shaft misalignment but also show how to minimize problems with out-of-true couplings (after a bit of arithmetic).  I needed to read it several times before I was able to get much of an understanding; this was complicated by a typo* and I had a little trouble keeping track of some of the mathematical manipulations too.  It wasn't that the arithmetic was hard, I just had a bit of trouble juggling and keeping track of all the variables.

So I wrote an Excel spreadsheet to take care of the number crunching.  In the course of working up the spreadsheet, I also figured out that if I had some information on the location of the engine's mounting points relative to the coupling face, I could calculate where the mounts needed to be shifted to bring the engine in alignment.  (This info is usually given on the engine data sheet from the manufacturer but a little time with a tape measure will probably suffice if the official data isn't available.)  If I knew the thread pitch of the studs on the engine mounts, I could also calculate how many turns of the stud bolt nuts would be required to move the front or rear mounts up/down. 

My one experience with this technique was most positive.  I initially had problems getting a consistent set of measurements but I was able to track this down to an error in technique ... I was bracing myself on the engine enough to cause the flexible engine mounts to deform slightly.  Having a methodical approach allowed me to see there was a problem.  Once I stopped leaning on the engine, I was able to bring the engine into alignment in about an hour or so.  I had a pro check it afterwards.  He told me I had about half the misalignment he would normally accept as being good enough.

Download both a copy of the article and copy of the spreadsheet.  Read the article a time or two, play around with the spreadsheet, starting with the numbers given in the article.  You, too, can "Get in line!"

*  The typographical error is about halfway down the left column on Page 4.  The phrase "(e.g. 1 to 2 and 2 to 4)" should read "(e.g. 1 to 3 and 2 to 4)".

REFRIGERATION

This download is in the form of another Excel spreadsheet, one that more-or-less replicates the calculations outlined in Nigel Calder's most excellent book, Refrigeration for Pleasure Boats.  A complete revision of our refrigeration system was in order during our 1994-95 "get ready to go cruising refit".   There were many questions to be answered and many design options to be considered.  What refrigerant?  What vendor's claims were legit, who was bogus?  How cold did we want to go?  Assuming holding plate(s), what eutectic solution?  What kind of power consumption were we looking at?  AC or DC or engine drive?  Hermetic, sealed compressor  or separate motor/compressor? And so on.

Too many questions with too much at stake to just flip a coin or shoot from the hip ... or take any vendor's advertised word for it either.  The engineer's classic solution to these kind of questions is to break out the pencil, paper, and calculator and start running some numbers.  Refrigeration for Pleasure Boats provided the basis for the calculations but trying to run calcs by hand for a variety of cases would get real old real quickly.  Hence this spreadsheet, which will run cases as fast as new numbers can be input.