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Old 21st September 2007, 05:16 AM   #11
Jean-Marc
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Quote:
Originally Posted by Roger View Post
If you back off on the downhaul with the softer mast, you will get a fuller foil both at the top and in the lower sections of the sail.
Why is that, Roger ?

I tought the contrary, i.e., a harder mast will deflect less, will tension more the leech and will not tension enough the luff curve (bend curve less than intended, thus making sleeve cloth more fuller because of less skin tension) below and above the boom whereas a softer mast will deflect more, will tension less the leech and will tension more the luff curve (bend curve more than intended, thus making sleeve cloth less fuller because of more skin tension). A bit confused as well...

Cheers !

JM
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Old 21st September 2007, 09:12 AM   #12
steveC
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With all due respect, the one thing that I have noticed is that static and dynamic loading produce clearly different results, regardless of SDM or RDM usage, at least with Bill Hansen's designs (Windwing, and now Hansen Sails). In fact, I've had to make some major adjustments in my outlook with more current designs (starting with the Bash model designs). What might look very loose leech on the beach changes significantly once on the water. While I'm not suggesting that that can be expected in other sail brands, we do need to keep in mind that things might not always be the same between different sail brands, and especially including the bends and characteristics of recommended masts (or not).
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Old 21st September 2007, 01:16 PM   #13
Jay
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Roger, thanks. I had forgot the Glide was cambered. So instead have you had the opportunity to compare a Backbone vs Joystick (or Speedstick or Lightstick) on a Retro? I would think that a Backbone 460 might be good with a Retro 7.5 on the Serenity because it is softer than a Joystick 460 and I would expect the smaller diameter of the RDM mast to leave more luff sleave to create a bigger pocket for a deeper draft. Does this thinking make sense?

Jean-Marc, thanks. Very helpful.
Just one clarification - when you said: "In contrast to a RDM mast in a standard sleeve, the excess sleeve cloth around the mast will make the batten heads go behind the mast, thus creating a much flatter profile on a static state. However, once powered up, this excess sleeve material will be under tension and will create a draft further away from the mast (up to 50% behind the mast) because once loaded with wind in a dynamic state, the excess sleeve material will be added to the initial shape of the luff curve." - you lost me a bit here. First to clarify - is this paragraph describing an SDM mast in an SDM luff sleeve or an RDM mast in a SDM luff sleeve? I guess I'm trying to understand your bottom line - are you saying that an RDM mast in a SDM sleeve gives more or less sail fullness (for the same amount of DH)?

Thanks guys - I really appreciate your help in figuring out the these issues!
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