Subject: Re: [harryproa] : Flat bottom hulls?
From: "Rick Willoughby rickwill@bigpond.net.au [harryproa]" <harryproa@yahoogroups.com.au>
Date: 10/13/2018, 11:43 PM
To: "harryproa@yahoogroups.com.au" <harryproa@yahoogroups.com.au>
Reply-to:
harryproa@yahoogroups.com.au

 


The hull length is the starting point.  The aim is to go for the maximum length you can pay for; build; transport; handle with intended crew and berth in desired location/s.   Having set the length you play with the design speed to produce a nice shape.  The point I made is that the design speed, for displacement mode, will be higher for a 3-panel hull than a semi-circular section hull. 

Length is king when it comes to performance in waves.  However for calm water performance the length actually reduces for high speed to length and the lowest drag hull will have a wet transom (does not apply to a HP).  Note that this is applicable to a displacement hull.  A 3-panel hull will get some dynamic lift, which reduces drag compared with pure displacement.  A semi-circular section generates less dynamic lift.  The dynamic lift can be significant on a lightweight high performance hull although foiling is faster than planing.

Rick
On 13 Oct 2018, at 8:23 am, Rick Willoughby <rickwill@bigpond.net.au> wrote:

You mention that a three panel optimized will be shorter than a half round... wouldn't this knock some points off the top end?
I can see some weight saving from floors and lower structure but a shorter hull runs counter to overall performance. Maybe I'm missing somethin.

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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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