Think about what would happen if you put both beams
in bearings so they were free to rotate The torsion load is what would restrain
this from happening. If you need further explanation, just say so. The analysis
of the actual forces and moments is more complex and will vary depending on the
details of hull shape, rig, beam structure etc
Cheers,
Peter
----- Original Message -----From: Malcolm PhillipsSent: Wednesday, November 17, 2010 3:31 PMSubject: Re: [harryproa] Re: Rig - windward or leeward? Forces at play
On Wed, Nov 17, 2010 at 12:56 AM, tsstproa <bitme1234@yahoo.com> wrote:
Where and why does the difference in rig placement racking loads come in to play?
Maybe this will help.
Imagine you have cylindrical beams and they have bearings in the windward hull so there are no torsion loads transferred to the beams.
You are sailing on a beam reach, with the boom perpendicular to the hull.
The forward component of the sail force is resisted by the short windward hull, which would make it bury the bow.
(This could be called a rotation or pitching moment using aircraft terms i.e. roll yaw.)
The long leeward hull is better suited to resisting the forward component of the sail force,
so pitching moment has to be transferred from sails in the windward hull via the beams to the leeward hull.
One question I have with this hypothetical setup (with bearing in the windward hull),
is how much of the pitching moment would be transferred by the two beams spaced apart.
A force down on the forward beam and up on the aft beam.
This would however cause torsion loads in the leeward hull between the beams.
The good thing about the Harryproa especially with a schooner rig is the reduction in torsion loads.
The long leeward hull resists the pitching moment, the beams and windward hull provide the righting moment.
I too have enjoyed your videos and insights and this discussion has helped me think about the forces involved.
Malcolm
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.869 / Virus Database: 271.1.1/3263 - Release Date: 11/17/10 21:34:00
__._,_.___
.