Typo calls should be calcs 

 

The heeling moment on a cat increases until the windward hull is out of,the water then it starts to decrease after that. A harry proa is the same as soon the windward hull is clear of the water then heeling moment starts to reduce.  All the calls are done assuming the windward hull is just clear of the water.

Chris Purkiss

M. 0428755749

On 7 Jun 2018, at 7:37 pm, Björn bjornmail@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:

 

Rick, you wrote (in another thread):

" An interesting feature of the harryproa configuration with regard to heeling is that the heeling moment reduces as the boat heels.  A cat with the mast in the middle or on both hulls has initial increase in heeling moment when one of the hull lifts.  "

Why does the heeling moment reduce on the harryproa, but increase on the cat?

On Fri, Jun 1, 2018 at 1:30 AM, Rick Willoughby rickwill@bigpond.net.au [harryproa] <harryproa@yahoogroups.com.au> wrote:

 

My first flat panel hull V14 taught me a lot about section shape.  My V11 hulls were the fastest up to that point and they had round sections.  The V14 were constant flare flat panel.  For the same weight the design data indicated 3% higher drag.  However the lowest drag length was about 15% shorter than the round section and that results in a weight saving.  In operation the V14 hull was definitely faster, and by a significant margin.

With regard to the 24 hour record, that boat was a V11 version 7.2m long with a round section.  The record was set in 2008 but broken by a surfski in 2015.

The fellow who set the record in 2008 has built one of my V16 hulls with the aim of retaking the record.  The V16 hull is the first version to use the variable flare generated by the 32 parameter shape function using GODZILLA (Michlet). The new hull is shorter, lighter and faster at target power level of 110W.

The link has a video showing the plug built to make the female mould:

https://www.dropbox.com/sh/2tcyk3y7drpwr2d/AACctJy1zD2FMDkG4fCykWzya/PlugVids20151107?dl=0&preview=VID_20151107_200302698.mp4

This link has a video of the boat with Greg operating at 110W giving some commentary on speed and other aspects of tuning the boat:

https://www.youtube.com/watch?v=0QrdEu1-zSc

As it turned out he did not go to LA as he could not muster the support needed for the attempt there.  He did try on the Calgary dam but weather and the short course affected his average speed.  I do not know if he plans to have another go this summer.  The 2008 record was set on Whitefish Lake in Montana.

 

On 1 Jun 2018, at 3:44 am, mcrawf@nuomo.com [harryproa] <harryproa@yahoogroups.com.au> wrote:

I'm predisposed to agree with Rick Willoughby on the flat bottoms for two reasons:   a) The flat bottoms work better with intelligent infusion than a half-circle (meaning: I will eventually be able to afford to build the boat), and  b) One of Rick's designs for a human-powered pedal boat held the 24-hour distance world record at one point.