SJ23 Tech Tip F06, (Updated 2002-12-10) Art Brown & Bob Schimmel


Jib Deck Tracks.

One of the reasons why I bought a San Juan 23 is because she can tack through 450 and track straight in a lumpy seaway without loosing headway like my previous boat with its ballasted center board.  Both are valuable performance assets when the homeward leg is upwind!  However, to get maximum upwind drive from the jib, the sheeting angle must be correct, both fore/aft and athwart ship. A track installed on the side deck ensures both. While the operating manual suggests attaching the jib sheet block to the toe rail, I find that too far outboard.  If the track is long enough, the forward end can be used for the storm jib and the aft end for a 110% or 135% jib.  The 150% jib is sheeted to the cockpit track.  However, I do release the jib sheet a tad to create for foil in the jib for lift.  It helps the boat to go faster.

NOTE:  "There are limits to increasing boat speed or arriving at your upwind destination sooner by pointing higher.  A high performance keel boat can do this for one reason only, keel shape.  The keel is a foil that generates lift as it "pulls" through the water.  Total lift is a squared function of forward speed: double the speed, quadruple the lift.  An SJ24 keel is much more efficient upwind with its high aspect ratio and deeper keel than an SJ23.  The SJ23 has a keel stub so it can be trailer launched.

The trick to getting the most pointing performance out of the SJ23 is to drive the boat hard to maintain speed through the water, which allows the keel stub to generate more lift, which leads to less leeway.  You can aim the boat as high as you want and sheet the beejeezus out of the jib, but on the SJ23 with the stumpy keel, compounded with the flat centerboard, the underwater foil just stalls, lift goes in the toilet, and the boat ends up going sideways.

I sheet my working jib to the rail, led from about the shrouds.  For Genoa sheeting, I trim it so the leach is about a foot off the spreaders, or more.  For comparison, I trim an SJ24 jib to ~(2-4)" off the spreader.  The goal here is to drive the boat hard with an open slot to let the sail plan breathe, not stall out the keel, and minimize leeway.  In addition, the SJ23 has relatively little rocker and sailing lower and fast means you don't pound into head seas, which stops an SJ23 dead.  When in doubt, foot off.  If you have speed through the water you have way more options to make something happen."  Glen Moore.

You can determine the optimum sheet angle by drawing a straight line from the middle of the luff, through the clew to the deck.  This position is usually good for mid range winds for the particular jib.  Since you now have a "middle point" for the track you simply have to allow for about a foot either way to accommodate the fore and aft positions required for lighter or stronger winds.  Do this for each of your jibs and you will quickly determine the position and overall length of the track.  The SJ23 manual, Tech Tip H08, Sail Setting Guide, also has for suggestions on where to place the sheet for the optimum angle.  Panache's track is equipped with Merriman doublewide block, so it is possible to change jib sheets on the go without releasing tension.  Also, a single sheet slides easier through a double block when tacking.  If you install a single block on the track then use a spring under it to keep it standing.  This does several things: it keeps it from flopping against the gel coat, which is also quieter when sailing in the "doldrums", and keeps it standing which means the sheet will run through it easier. 

DECK MOUNTING - The track on Panache (shown at right) is through bolted to the deck and the holes are sealed with epoxy to prevent wood rot.  Sikaflex is used to keep the water out.  A strip of tapered oak is installed on the ceiling to encase the nuts to prevent a nasty scrape on your skull.  Wow, can that make you miserable!  I can't remember how the track nuts on Banana Split (below left) are covered but I sure wish I had that full length to position the block exactly for each jib. 

The track on Banana Split (at left) was bent horizontally (along the difficult axis) to follow the curve of the cabin.  Forming the track horizontally is best performed with a bender equipped with three wheels or rollers; two idlers rollers on one side opposing a third hydraulically loaded roller on the other side, between the two rollers.  As the track is pushed and pulled between the three rollers, the force from the middle roller bends the track in a smooth curve.  There's art involved in doing this job and it pays to have some experience.  Benders of this type are available in specialty machine or aircraft maintenance shops.  Sometimes you can find an old guy who just happens to have one.  "This happens more often than you think.  All you have to do is ask, with a coffee in hand."  The alternative technique is to create 'steps' in the bend using a bench vice.  However, a stepped bend looks crude next to the smooth curve of the cabin as your eye can compare the parallel lines.  In operation the car may jamb at a step.  I've also seen long tracks consisting of two sections, one added later.
"This happens when you determine that you need a longer track and are too cheap to buy a single replacement section.  Instead, someone offers you a deal on a surplus section and the gears start churning on how to merge this new treasure in a seamless fashion.  I've been there and done that, so I don't blame you.  At least make it look intentional and ask for a beer if someone wants to hear the rest of your story."
If you decide to add your treasure, then "key" the ends together to create smooth sides and prevent binding the car at the junction.  This is far superior to butt joining where the two sections can move sideways with respect to each other.  If there is no gap inside the keyed ends then the finished job looks quite good and operates very satisfactorily.  I wouldn't hesitate to add a curved section to the aft end of Panache's track. 

CABIN SIDE MOUNTING - Besides the potential for water leaks and wood rot in the deck core, the other problem with a deck mounted track is that the sheet block is perfect for catching bare toes.  (I hate that!).  I realize you shouldn't walk barefoot on deck, but there are times when it's simply too hot to bother with shoes.  In this case, sandals are a good alternative.  Make sure they are the type that are OK to get wet and stay on your feet!
Anyway, to keep your toes, a friend suggested installing the jib track on the side of the cabin, just below the window.  This is the factory technique on a SJ28 as shown at right.  Note that the block is hanging and the deck is almost clear.  Shown on the left is an SJ24 with a similar installation.  With this technique it is possible to back up the track on the inside of the cabin by through bolting it to a hand rail.  A shoulder height hand rail in the cabin is a very useful addition on any boat whether to hang on to in rough weather or to dry clothes in calm! 
The cabin wall mount is a favourite location of many designers to achieve close jib sheeting.  If I had to do it over again, I would install the track on the side of the cabin.   The SJ23 cabin is strong enough to support the sheet load.  However, it must be backed up with a strip of aluminum inside the cabin to distribute the load.  If you want to hide it, cap the aluminum strip with a thin wood cap, over which you can install the grab rail.  Makes a nice neat, functional installation that is easy on the eyes and hands. 

NOTE: Bending the metal track to conform to the shape of the fibreglass prevents stressing the glass.  Bending can be accomplished over a sand bag, between three rollers or over an anvil. 

  • On the cabin side installations the track was bent (along the short easy axis) to conform to the shape of the cabin. 
  • Bending sideways (along the long difficult axis) can be done in a machine shop if you don't have the skill.  But it is possible to bend between two pegs with the track held inside a conduit.  You just have to put some elbow grease in it.  The trick is to create a matching radius bend.

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