The Perfect Mainsheeting System
(or How I Re-Invented the Wheel)
by Bob Dymond
Sunday, 30 May 2010
A couple of years ago I really got tired of the stock mainsheet system on my FROB.

You know what I'm talking about: Triple at the top, and double with a becket at the bottom. Turns into a real rats nest when you need it to run, or it decides to demonstrate the all the properties of friction when you are turning the leward mark.

I would sit in meetings at w**k, assiduously taking copious notes of the utterances of the division chiefs. Of course, my notes were taken in my own particular shorthand which has a striking resembalance to a series of circles which had extended diameters, and were connected one to the other with one long tangential line.

When asked, I would reply: "It is my unique combination of Boolean Algebra and Set Theory with which I can easily reconstruct the entire presentation we just saw."

As most of the individuals asking the question were Management or Management Staff, they just nodded their respective heads and said: "Hmmmmm. . . . interesting."

4:1/16:1 Double-ended Fine Tune
Click here for Harken Page
As the title of this page suggests, at the end of the day, I found I had re-invented the wheel, because what I "invented" was a system the specifications of which can be found on the Harken Web Site. And a much nicer illustration than I could ever draw.

However, the Harken System calls for attaching, in tandem, two 76mm blocks to the boom.

Obviously one block would be attached to the existing bail at the end of the boom, but I was loath to put a bunch of screws in the boom in order to hang the other block.
My solution was to use a Spectra Loop (24" circumference) which is literaly looped around the boom, and stayed in place (so it does not creep forward) with a string tied from the Loop to the bail.

Here is a photo of the 76mm block mounted on the traveler car.

Mainsheet to fine tune double.
Mainsheet to fine tune double.

Lower left corner: Swivel Base w/Cam, and Hexaratchet. Parts B & C in the Harken diagram.
As you know, you can pay a lot of money for a Spectra Loop, but I have a couple of sources listed below (including current prices). The Spectra Loop you see in the photos has been in place for over a year (removed during the winter of course) with no signs of wear. I purchased it from "Tools for Stagecraft" (see below) for the princely sum of $13.00. I have since found an addition source at REI.

Lots less than the Harken Loops.
Spectra Loop (The ones I've been using)
Rated at 5000 lbs.
11", 24" and 44" lengths (diameter), @ $7.00, $13.00 & $30.00
Mammut Dyneema Contact Sling
Item # 709160
24" diameter@ $9.50
Mammut Dyneema Contact Sling Specs
Weight (48 inch) 29 / (24 inch) 15 grams
Strength 22 kilonewtons (~5-6 tons)

I hope this material may be of use to some of you folks.

For me, it removed yet another excuse for not trimming in the main quickly enough when going around the leward mark.
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