Great Thanks for walking me though it. These forces all seam pretty obvious but cemented now. Three different axis of force. What I still don't get is Rob saying there is no way beams on an Atlantic or Pacific would be lighter than on his craft due to lower forces at play. To me it still seams its based on weight, and where it is located. The stayed rig would even help to prevent some force on entire craft. Like that of a dolphin striker under mast on beam of a beach cat or like that of a suspension bridge. As I have explained before Atlantic with all the weight to WW with just the float the saving in weight on just the float would seem to make up any difference in extra strengthening needed, if needed. Which I don't see much difference between the two if both were engineered to there fullest potential. Advantage atlantic still achieving a higher righting moment.Pacific with hardly no weight to windward when static or when sailing. Smaller everthing meaning lighter in weight over all for fast sailing with minimal sail, hull, weight, down side maybe not as much room. Its starting to sound more like Robs boat could be a novelity over traditional catamarans being based on catamaran principals due to over all balance and dynamics in how it sails. Truly unique. Even my flat bottom models, square harry, slam tacker show extreme sure footedness with very little weight.
Really though, advantage Echelon the shunting tri with centralized weight location on shorter beams connecting all three hulls. Beam and hull integrity could be optimise to there fullest as each one will see different loads. But still craft is limit in terms of space. Just a small rant.
Todd
--- In harryproa@yahoogroups.com.au, "Peter Southwood" <peter.southwood@...> wrote:
>
> 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 Phillips
> To: harryproa@yahoogroups.com.au
> Sent: Wednesday, November 17, 2010 3:31 PM
> Subject: Re: [harryproa] Re: Rig - windward or leeward? Forces at play
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> On Wed, Nov 17, 2010 at 12:56 AM, tsstproa <bitme1234@...> wrote:
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> Where and why does the difference in rig placement racking loads come in to play?
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> 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
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