[Rhodes22-list] Mast Bend With A Masthead Rig & Double Lower Shrouds
Roger Pihlaja
rhodes22-list@rhodes22.org
Wed, 21 Aug 2002 19:21:11 -0400
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Richard,
It is precisely because the Rhodes 22 masthead rig has double lower =
sidestays that it can exploit mast bend. Please reread my rig tuning =
procedure. Note that, with a standard rig, I specified about 200 lbs =
differential tension between the fore & aft lower sidestays. With the =
forward lower sidestays about 200 lbs tighter than the aft lower =
sidestays, the mast is constrained from rotating around the mast =
tabernacle at the lower sidestay attachment points just below the =
spreaders. Now, when backstay tension is applied, the mast must bend, =
primarily from the spreaders upwards to the masthead. Actually, the =
curvature extends below the spreaders as well because it is physically =
impossible for there to be such an abrupt discontinuity in the strain =
curve of the continuous mast extrusion. So, the bend curve tends to =
spread itself out along the entire length of the spar with the =
centerline of the mast actually moving slightly forward to relax out =
some of the differential tension in the lower forward sidestays in the =
region around the spreaders. This curvature is easy to see by holding a =
halyard up against the aft edge of the mast while varying the backstay =
tension. Rather than argue with me, I challenge you to go out on your =
boat, set up the rig as per my procedure, & see for yourself.
Roger Pihlaja
S/V Dynamic Equilibrium
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<DIV><FONT face=3DArial size=3D2>Richard,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>It is precisely because the Rhodes =
22 masthead=20
rig has double lower sidestays that it can exploit mast bend. =
Please=20
reread my rig tuning procedure. Note that, with a standard rig, I=20
specified about 200 lbs differential tension between the fore & aft =
lower=20
sidestays. With the forward lower sidestays about 200 lbs tighter =
than the=20
aft lower sidestays, the mast is constrained from rotating around the =
mast=20
tabernacle at the lower sidestay attachment points just below the=20
spreaders. Now, when backstay tension is applied, the mast must =
bend,=20
primarily from the spreaders upwards to the masthead. Actually, =
the=20
curvature extends below the spreaders as well because it is =
physically=20
impossible for there to be such an abrupt discontinuity in the =
strain=20
curve of the continuous mast extrusion. So, the bend =
curve tends=20
to spread itself out along the entire length of the spar with the=20
centerline of the mast actually moving slightly forward to relax =
out some=20
of the differential tension in the lower forward sidestays in the region =
around=20
the spreaders. This curvature is easy to see by holding a halyard =
up=20
against the aft edge of the mast while varying the backstay =
tension. =20
Rather than argue with me, I challenge you to go out on your boat, set =
up the=20
rig as per my procedure, & see for yourself.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Roger Pihlaja</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>S/V Dynamic =
Equilibrium</FONT></DIV></BODY></HTML>
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