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Boom Internal Outhaul - Flatten Mainsail & install to shorten boom.

The section of boom protruding beyond the clew supported an external block & tackle to tension the mainsail foot.  The problem with the protruding section on Panache is that I sometimes didn't see it coming across.  Yikes!  I guess this is why its called a boom?  The prospect of it whacking my head was not something I looked forward to on my outings.  Since I've had far too many close calls and lost too much coffee, I shortened the boom 9" so now it extends only 6" past the clew.  Shortening the boom solved one problem.  It also necessitated an internal outhaul due to the reefing lines installed on the outside of the boom. 

At left is the exit block of the outhaul line at the bottom of the (mid) boom.  At right is the shortened boom showing the entry block of the outhaul line. 

Construction

• Use a metal cut off saw to make a perfect square cut across the end of the boom.  I have a stand with a threaded top to support the boom at exactly the same height as the saw table.  This is important to line up the boom perfectly square to the cutting disk and to steady the boom for cutting.  File off any burs and go to the next step to install the internal outhaul.
• My initial outhaul design was a simple 2:1 block & tackle that lead aft to the cockpit.  But not having space on the deck to terminate the line I chose a 4:1 block and tackle that exits at mid boom as shown at right. 
• Ball bearing blocks have the least internal friction and are therefore the prime choice.  My internal blocks are equipped with smooth turning bronze bushings and I have not experienced a problem with them.  However, the exit blocks are equipped with ball bearings.  I installed the exit block on the side of the boom for a simple installation.  The line then loops through the clew and back to an eye strap at the end of the boom.  This balances the pull on the clew but adds some friction. 
• All blocks and the end casting are mounted with aluminum pop rivets with marine adhesive between metal surfaces to prevent corrosion. 
• All line is 5/16" prestretched polyester.  Look at the diagram at right to see how the control lines are installed.  Three lines are required.  A static line is attached inside at the gooseneck.  (Remove the goose neck cap to secure this line).  The other static line exits at the free end of the boom. (Remove the end cap to secure this line).  This line exits through the side mounted exit block, turns forward to the mainsail clew and back to an eye strap.  The control line exists at the middle of the boom to an exit block and then through a captive jam cleat to hold the tension while sailing.  To prevent an internal jamb, adjust the lengths of the three lines to position the internal blocks such that they never jamb against the bottom exit block or whatever else you have inside your boom.  The correct relative position is shown in the diagram.  In the above left photo I've pulled the sail cover back to reveal the bottom exit block and jam cleat.  Note that the style of jam cleat on Panache holds the line captive, make cleating easier in a rough seaway.  The line exists at about mid boom so it is within reach of the companionway when the boom is ~45⁰ out.

Conclusion - With the shorter boom I can now stand astride the tiller, steering with my knees and focus on where I'm going without fear of a concussion from the boom.  I can also finish my coffee to the last drop!  With the outhaul adjustment in the middle of the boom, I can adjust the tension on all points of sail except downwind, thereby maintaining sail balance and drive.  There is sufficient mechanical advantage to tension the foot of the mainsail well beyond what is required.  You don't have to be a deck ape to perform this job!  The only problem I've experienced, is dealing with the internal friction to release the tension for light air sailing.  This merely requires that I pull some slack into the line and push the foot of the mainsail forward.  (Seems like a dumb thing to say but it works).
"One day my buddy and I were sailing in fairly light winds and he thought the mainsail was too flat, while I thought the sail was loose enough, having no tension on the foot.  By moving the clew forward 6" and inducing wrinkles in the foot, we gained another knot of speed.  I have never forgotten that lesson.  You learn something new every day!"

NOTE - Unfortunately I can only guess at what the factory version of the outhaul line looks like.  Panache did have a block and tackle between the clew and the end of the boom but it was not factory hardware.  The previous owners of Panache changed this long before I bought her.  This is a similar system to what Panache had.
 

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