Subject: [harryproa] re: telescoping again
From: Mike Crawford
Date: 5/1/2007, 3:09 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au


  I've become quite a fan of luff pockets over the past five years, but despite my fondness for them, I'm not sure they would be a good fit for the fast proas.

  If you've got a gaff rig like the Wharrams, which fully supports the sail, then you can go to soft Dacron sailcloth without resin stiffeners, and then you can reef pretty easily if the pocket is large enough to collect at the bottom in a pile.  In this case, the efficiency-to-cost and efficiency-to-effort ratios are very impressive.  No sail track or cars to purchase or fail, no mast rotation to fine-tune on each course or wind change.  A brilliant cruising design.

  But I'm not sure I'd go for that gaff on top of a flexible unstayed mast.  Without that gaff, you'd need stiffer sails, either mylar or resin-impregnated Dacron, probably with full battens, and that would cause all sorts of problems with gathering the folds at the pocket, as well as wear and tear on sails that won't have a neat series of spaced cars that allow the sail to flake from side to side. 

  With that said, I'd love to see someone implement brag_rotor's ideas of the gaff wingsail shown in the photos.  But since I'm only an armchair quarterback, I can't really say too much about that.

       - Mike



Rob Denney wrote:

 
----- Original Message -----
Sent: Monday, April 30, 2007 9:22 AM
Subject: [harryproa] re: telescoping again

Rob said:
<I am not worried about friction so much as wear on
<the lower mast.

not possible to have plastic where they touch each
other?

<The sail is on slugs in tracks on both the top and
<bottom pieces. Hoist it up the lowered top piece,
<then hoist the top piece, raising the sail up the
<lower piece.

Aha, the outside part is on top. Neat, but then the
flex will be completely odd?

< Boom is bonded to a bearing on the mast. Self <

vanging.

so you can rotate it relative to the mast? Then the
track is starting to sound desireable.

But to me a luff pocket seems way less difficult.
It can be D section, by which the outer section would
be stronger since there is a straight shear web?
And the inner can be on top, then both can be tapered.
And the halyard and telescope line could be the same?
Here:
http://farm1.static.flickr.com/191/477637200_6c9b9bd9b9_o.jpg
And, if the two got stuck up there, you could still
lower the sail.

 regards,


Rob



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