Rig Tension and Tuning

Rig Tension and Tuning

Rig tension refers cumulatively to shroud, cunningham, and outhaul tension. The rig tension should be set appropriately to the wind conditions you'll experience. Those new to the UFO need not focus on "perfectly" tuning the boat for the wind conditions. You'll be able to enjoy foiling with this basic rig tension setup. For those wishing to race the UFO and want to tune it more precisely, see Advanced Tuning and the UFO Rigging Table below.


Basic setup

  • Pull shroud tension until there is ...

  • Pull cunningham tension until ...

  • Pull outhaul tension until ...

That's it - go enjoy foiling!



Advanced tuning

This section references the use of a tension measurement device. See the tool section for the recommendation. Select the condition's tab below to view that condition's recommendations. Alternatively, one sailor nicely summarized a UFO rigging table for a variety of conditions. While it differs in some aspects, it is also presented below the tabs.

Bottom of mast markings to calibrate cunningham tension

Lowered mainsail setting

  • Hoist the sail to full hoist, the halyard should be cleated on the mast with the sail at the very top of the track

    Attach no other lines.

    Add rig tension (on diamond shrouds) until both stays read 40kg of tension

    If you're getting uneven tensions by more than 5kg (batten loading will always make it slightly uneven), release the rig tension and move the final bowline hitch on the loose shroud at the black low friction ring. Repeat until you've got an even 40kg (or 5/barely reading on a PT-1) on each stay.

    Pull the cunningham on -- it’s hard but doable -- until you have 5.5 inches (14cm) of separation between the bottom of the bolt rope (the actual bolt rope, not the “slug” or the strap) and the top surface of the mast collar. It is a good idea to mark this 5.5 inch spot on the mast.

    Pull on the outhaul until you read between 85kg and 100kg (16 on a PT-1) of tension in the shrouds. You can't attach the gauge to the outhaul (no room) so you need to deduce it from the shrouds tension. When the grommet is just shy of the 7 inch mark, the shrouds read 100Kg. It is a good idea to mark a ruler on the end of the boom to calibrate this.

    This results in a full sail that takes off faster in puffs and keeps you flying through lulls. Works great in the 8-12kt range.

    Why this is good: Flatter sails, while technically more efficient in wind are outright disadvantaged in course-racing both upwind and down, in 8 to 12 knots at least as far as we can tell. Essentially it's better to lose some performance up in puffs with a full sail than to fall out of the sky in lulls with a flat sail.

    Downside: at full straight tension, it can be a bit “binary” - full power on, or off with a narrow “some power” band. It can be hard to “calibrate” your sheeting. Pumping does not work well (sail stalls). If this affects you, try flat’n’twisted below.

    To depower this setting: Ease Shrouds just a tad. ADD CUNNINGHAM AND OUTHAUL

  • This is another option that works well. Needs a bit more wind than full straight sail.

    Apply some cunningham before rig tension.

    Then rig tension.

    Then WAY WAY WAY more outhaul. flat’n’twisted achieved (ie: see picture above, with grommet at approx 4 ½ inches from metal arch).

    TODO: Need tension numbers.

    The twist seems to counteract the downside of a full sail with a straight leech when you're pumping. If you have an outright full and straight sail and you're pumping you have pretty high odds of stalling the sail. If you twist it, you'll keep a bubble of attached flow on the sail somewhere which can be used to reattach flow elsewhere.

  • With wind in the 12+ range -- recipe:

    Hoist to the top… and then drop it ~3 inches (top of sail will be ~4 inches from halyard eye at top of mast). You can mark the mast with white electrical tape.

    Before attaching any lines - put ~35Kg on the shrouds

    Apply downhaul until sail boltrope is ~2.5 inches from mast collar

    Apply outhaul until it's the sail is ~1 inch from from maxed out

    Shrouds should now read ~85Kg

    Because the sail sits lower, in this setup you are somewhat limited in how much you can depower from there. If you are expecting big winds at any time in your outing, hoist to the top. When you need it you'll have the full range of the downhaul to depower.

    Combine this with Low Drag foil configuration covered in the Rudder and Foil Rake Section

  • This is serious business!

    Sail: bring the batten tension down to baseline, in particular the 2 top battens need to be depowered. (Remember to power them back on for light conditions.)

    Rig:

    Keep the shrouds relatively tight.

    NAIL. THE. OUTHAUL. (full outhaul puts a lot of pressure on the spreader bracket -- you want the spreader bracket fully upgraded to latest spec…)

    Cunningham to taste.

    Keep the endplate sealed (the bottom of the sail must close the gap with the deck)

    Wand: pull it up about six inches

    Main Foil: forward pin groove

    Rudder: minimum rake, to the point where the tiller almost touches the wheel

    Going for peak speed. Try to hold about 7 degrees of weather heel and just stay laser focused on one point you're steering towards.

    Try not to use the tiller at all. Use sheeting and body motion. Steering is slow and unstable. The boat is a missile and you are the guidance system.