TUNING A HOBIE 20
By Chris Bolton

Most people are doing things pretty much the same, as far
as I know. The side shroud pins are put in the 3rd or 4th
hole from the top, and the forestay is adjusted to be
TIGHT (this requires setting one shroud pin loose (top
hole) to raise the mast, then hanging on a trap wire in
order to get the pin in its lower hole (TWO PERSON
JOB!!). Mast rake is measured by taking a line from one of
the trap wires and noting the point at which the line hits
the bridle wire tang on the front of the hull. (Pull the trap
wire off the bungie; might need to add a 3’ piece of line to
the trap handle to make it long enough) Run the line back
until this point hits the aft deck, and that is your rake
measurement. The center of the hatch cover is a good
intermediate location. Some people have been playing
with LOTS of rake (like a 16) for windy conditions, but the
jury is still out on this, and I am not convinced. Might have
to add a forestay extender or second shackle to the mast
tang to get this much rake. Adjust the rudders with very
little toe in (1/8" or less), and kick them under so that you
have manageable weather helm (don't get rid of all the
weather helm, though). I don't know what a ballpark
setting is for the adjustment screw, but it ain't out much
(rudders are almost touching the castings). Maybe around
1" of rudders are forward of a line straight down from the
pintles. Remember that as you change the rudder rake,
you should check/adjust the rudder cam tension. As far as
the spreaders, most of the guys leave them at factory
settings, and tension the diamond wires to about 475 lbs
(you'll need a wire tension gauge to check this). The
dealer's setup manual will give the initial settings, but I
think putting a straightedge across the spreaders should
show a 2" height above the luff track (I might be off on this
number). The prebend varies wildly with sails and
conditions and crew weight. If you have a flat sail, you
don’t want as much prebend (more tension=flatter sail). If
it’s blowing, you want a lot. I’ve heard of people running
up close to 800# of tension in big air. Each 360 degree
turn of the turnbuckles is roughly 50# of tension. Carry two
screwdrivers or similar on the boat; often it helps to adjust
this tension between races. If you can’t keep it flat upwind
with the downhaul cranked on, add more tension. If you
don’t have enough power (can’t fly a hull), ease the
tension off.
Adjust the jib blocks while you're out sailing on a
reasonable day (not 20 plus) so that the jib is about 2
inches from the spreader rollers and is not twisted off too
much from top to bottom (upwind). This setting changes
depending on where your mast is rotated; try pointing the
rotation bar at the leeward shroud initially. The jib cars go
outboard as the wind picks up to keep the slot open; they
also might need changing in light air for the same reason.
Batten tension is not too critical (I think); put in just enough
to remove any wrinkles in the sail; better too light than too
much. A lot of people are using very flexible battens for
the top two slots, and softer-than-stock battens for
everything except the bottom two. Ideally these bottom
two should have the draft a little further back to help keep
the jib slot open. I wouldn’t worry about this too much yet.
Of course, your boards and rudders all have smooth
leading edges (no mold lines), and squared off trailing
edges? Hum is slow and leads to ventilation (not good).
Upwind the jib halyard is fairly snug, and most people
loosen it up (to the point of almost getting wrinkles)
downwind. The outhaul should be snug, or maybe a little
loose in light air. I think that's about it for rigging. More tips
for on the water tuning in the next issue.

TUNING A HOBIE 20
Chris Bolton