Subject: Re: : Re: [harryproa] Re:: Tortured infused panels.
From: "Jerry Barth shredderf16@sbcglobal.net [harryproa]" <harryproa@yahoogroups.com.au>
Date: 8/30/2019, 12:29 PM
To: "harryproa@yahoogroups com. au" <harryproa@yahoogroups.com.au>
Reply-to:
harryproa@yahoogroups.com.au

 

Rick,
The foils are to help with capsize moment while sailing? I've got plans for a Woods Strike 15 and a pile of foam in my workshop, it's intriguing to add something like that to it when I start building. My initial plan was to have a Chinese electric outboard as well but since I pretty sure I'll flip it at some point one of your peddle drives makes better sense.
Jerry Barth



On August 29, 2019, at 11:33 PM, "Rick Willoughby rickwill@bigpond.net.au [harryproa]" <harryproa@yahoogroups.com.au> wrote:


  

The prop is 330mm diameter.  It spins at 5X cadence on the yellow boat.  Pitch is set to give just over 5kts at cadence of 70rpm.  I have used bigger props with gearing as low as 2X but anything less than 4X give noticeable torque roll.  At 5X ratio the torque at 5kts roughly offsets the offset weight of the drive so trim remains level if there is no initial list.  There is a point where the drag associate with strut and shaft offset ant gain in efficiency from using a larger prop.  Also a larger prop has so little slip that it gets hard to spin in a headwind. The 330mm works out to be close to optimum.


I use T-10 synchroflex belts.  The on in the video is 25mm wide.  I have used 16mm with a slightly larger crank pulley.  16mm is OK for sustainable power but could be broken if pushed hard during a sprint.

The blade twist is not set for constant pitch but to give good blade loading.  There is a slight reduction in induced drag with the blades compared with a blade of constant pitch.  The prop efficiency hardly changes throughout the speed range.  The slight gain in efficiency at higher Re# with constant blade loading is offset by the increase in wave drag increasing blade loading.

The pedal drives are considerably more compact than oars.  They also face forward (or sideways on larger boats).  Pedal drives are also much easier to use for sustained periods and in rough weather.  I can easily motor sail using the pedals although I cannot spin above 8kts so I have to force the prop to fold or raise the prop out of the water.  The pedals spin violently if not held back once the boat gets some speed up.  I usually lift the pedal prop when I motor.  

Rick

On 30 Aug 2019, at 1:23 pm, Stone! Tool owly@ttc-cmc.net [harryproa] <harryproa@yahoogroups.com.au> wrote:

Rick:
    I assume you are using Gates Polychain or HTD belt...... Looks to be about 1.5"....... I like your large dia low speed prop.... it's about what I would have gone for.  I also like the way you designed the prop mounting so it could be brought up easily... elegant!  My guess is that this system is 1x all the way through.... which I like also.... It just makes sense in so many ways in terms of R-number range gearing losses, tip losses, etc.

    I assume that your prop has twist, though it is not obvious......... Prop twist is an interesting topic.   It creates a "groove"......... a speed where it all comes together....... above or below that speed it is not optimal.

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Posted by: Jerry Barth <Shredderf16@sbcglobal.net>
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