To paraphrase Walter Schultz ( Shannon Yachts) statement of decades ago " as wind speeds increase you want to maintain the position of the head sail at the extreme bow of the boat. This will result in a better mannered vessel with a neutral helm."
He took it as far as to place the smaller (TOPSAIL) sail in front of the larger STAYSAIL on his designs.
So did Bob Perry on most of his double-enders. Perry LIKES 'large' staysails, me too.
If you analyze from a 3 (or 4 or more) dimensional perspective - x, y, z + rig elasticity and sail elasticity .... and not just a 2 dimensional combined center of effort of a sail plan, my exhaustive data collection on a PerryBoat Cutter over the years would agree with Schultz' statement ....
On a cutter rig, this is far far far more complicated than with a simple sloop.
I think what Schultz' comments addresses is the (infernal) headstay sag (and opposing reactional forestay 'tightening') that NATURALLY develops on a cutter rig ... with headsail, staysail flying and the wind strength is 'changing'. The 'dynamic interplay' of rig tensions and elasticity is incredible on a cutter rig.
Simple speak (at least trying to simple speak):
- on a cutter rig especially
, if one allows the luff section of the headsail to sag off to leewards and that luff curve (w/r to fore and aft AND from the Center Line)) is much greater than the 'hollow section' that the sailmaker cut into that forward edge, any boat will begin to skid off to leewards, and usually with the helmsman erroneously decrying 'weather helm'. With an improper headstay tension (for the actual wind strength) allowing headstay sag off to leeward, the 'dynamic
' center of effort of the headsail is now no longer near or as close to the boats centerline (along that imaginary 10-12° headsail tack-to-clew line); plus, with additional fore/aft headstay sag the headsail leech will close (tighten) and which totally screws-up the interaction between headsail and staysail ('bootstrapping' / 'velocity dumping') .... draft aft, hooked-up / tight leech, headsail CE way off to leeward = skidding to leeward
- aggressive heeling, slow and cranky boat, plus the 'feeling' of weather helm.
Remedies for cutter rigs
(in agreement with my impression of intent of Schultz) and for optimizing going-to-weather / pointing.
1.headsail luff sag (to leeward) correctly tensioned via backstay .... with additional 'help' from runners if required. The wire sag should exactly 'match' the smooth concave curve that the sailmaker cut into the luff - depending on wind strength.
1a. to decrease 'fore/aft' headstay sag (opens the leech and remediates 'draft aft') - slight release of sheet / winch pressure to help remedy fore/aft aspect of wire sag. Keep the gorillas off the winches!!!
1c. when beating for optimum VMG, LOOSEN
forestay (the staysail wire) tension ... but don't allow staysail luff to sag to weather .... 5% tension?? if you slightly loosen the forestay on a cutter rig, the headstay will automatically 'tighten' and without increased backstay tension.
2. Super-laminate sails, or very high quality high aspect ratio dacron cut into a radial, etc. pattern for least stretch possible. Less sail 'elasticity'
3. Re-tension halyard(s) as needed to control draft position
and control leech shape.
4. Control/optimize 'slot' distance (all sails) via sheet tension (and/or barber hauler). The higher the wind speed, the 'larger' the slot distance. Set the correct 'slot open' distance via max. output of your speedo (vmg).
4a. As wind speed (or boat speed) increases, increase headsail and staysail CUNNINGHAM tension to help the luff entry to become 'more rounded
' (w/r horizontal plane); will also help with keeping the leeches FLAT and 'open'. The higher the boat speed or wind speed, the more 'rounded luff entry shape'.
5. When all else fails, reduce sail area / reef down.
If one sets up tensions at 'plain vanilla' 12-15% on a cutter, invariably as the wind increases, the luff sag will cause skidding and the CUTTER will only be tacking through 90°A .... or more. Set up as above and the CUTTER RIG, especially a Perry Boat, can easily tack through ~70°A and be pointing (and at optimized VMG) like a banshee. (Got the load of PHRF pewter to prove it).
Note - Skidding is determined by noting increasing helm pressure followed by watching the stern wake. The turbulence from the rudder should be about 3° off from the centerline in a well rig tensioned boat with correctly shaped
sails .... plus watching for that headstay sag
Note1 - precision monitoring of headstay sag, (forestay sag on sloops) http://www.ftp.tognews.com/GoogleFil...f%20Hollow.pdf
Note2 - set up the amount of mainsail draft via outhaul tension so that you get maximum speedo output .... every time you go out because every day the wind and sea state is 'different'. If you don't have perfect mainsail shape for the days conditions, you'll never have close to perfect jib/genoa/topsail/staysail shape and performance output.
Note3 - If the boat is NOT skidding, control weather helm via mainsail halyard or cunningham tension.
Note4 - special aerodynamic considerations for staysails that don't apply to sails made for 'sloops': http://www.ftp.tognews.com/Publicati...e_Head_Rig.pdf
hope this helps. ;-)