Subject: Re: [harryproa] re: telescoping again
From: "Rob Denney" <proa@iinet.net.au>
Date: 4/30/2007, 10:13 PM
To:
Reply-to:
harryproa@yahoogroups.com.au

 
----- Original Message -----
From: sigurd grung
To: harryproa@groups.yahoo.com
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?

That is the plan, but we need to figure out a bullet proof way of attaching it.

<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?

Odd, but not completely.  I hope.  A challenge for the engineer and sailmaker, but they both seem to think it is not insurmountable.


< 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.

 

I have a pocket luff on Elementarry.  It is pretty hard work.  First, you need full length battens which need camber inducers which do not work on tapered masts.  Second, when lowered it is very messy.  Third, the sail would have to go over the join during raising and lowering, which is very messy.  The pocket luff would also be different when reefed.

regards,

Rob



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