Subject: Re: [harryproa] Span Efficiency - Another Harryproa Opportunity |
From: Arto Hakkarainen |
Date: 6/7/2011, 3:14 AM |
To: harryproa@yahoogroups.com.au |
Reply-to: harryproa@yahoogroups.com.au |
Rick,
So to consider what this means in reality let's think about visionarry size boat. If the mast is 18 m high above water and the boom sits about 2 m above deck meaning boom is about 3 m above water we get 15 m span on the rig? Right? And 10 % of span means then 1,5 m between sail and deck to have the span efficiency of 1,3? And recuding it from 1,5 m to 0 m increases the span efficiency by 54 % (1,3->2)? Does this mean that with no end plate at all span efficiency is 1? Did I get it right?
With such increase in span efficiency how much is L/D improved? If I understood the Tom Speer figures correctly already 1 % gap (15 cm in the example above) increases the induced drag significantly and moving from 0 % to 1 % has biggest effect on the efficiency. Or am I reading it wrong?
Arto
--- On Tue, 6/7/11, Rick Willoughby <rickwill@bigpond.net.au> wrote:
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