[Public-List] A30 Hull Prismatic Coefficient

[Kris Coward]

What sort of transmission are you looking to use? When I built my
electric, I went with a timing belt (H type -- I initially went with
double V-belts, but they'd slip too much when the prop would get fouled
with weeds; I'd love something that would slip when the prop's fould
with something heavy enough to bend the shaft or wreck the alignment,
like a mooring line or a sheet, but still grippy enough to rip through
dense weeds, and ended up having to err on the side of actually being
able to get out sailing).

-K

On Mon, Jun 28, 2021 at 11:21:40PM -0300, David A. Bardsley via Public-List wrote:
>    Gordon,
>    That is an awesome data point, thank-you very much.  It helps
>    corroborate something I'm seeing in these spreadsheet calculators.
>    One such tool is predicting 4.4kts at 1000rpm and 5kts at 1150pm.  This
>    data point of 5kts at 1000rpm will help me calibrate this tool's s
>    coefficients so I can make meaningful predictions throughout the entire
>    power band.
>    Right now it feels like I'm zeroing in on 1.65:1 as the optimal match
>    for one specific motor's dyno data and my 13-8 sail prop.
>    Dave
>    Ginseng 574
> 
>    On Jun 28, 2021 22:45, Gordon Laco <mainstay at csolve.net> wrote:
> 
>    Here’s a bit of direct observation to help you… when we had the
>    factory-installed two blade 13 x 7 on the boat, 1,000 rpm gave us
>    5knots.
>    Gordon Laco
>    Surprise 426
>    [1]www.gordonlaco.com
> 
>    On Jun 28, 2021, at 7:00 PM, David A. Bardsley
>    <[2]davebardsley at eastlink.ca> wrote:
> 
>    Gordon,
>    Thanks for the pointer.
>    I've removed the PO's vetus diesel and am installing a 10kW electric
>    drive with a completely new transmission.  I'm free to pick an
>    arbitrary ratio to maximize (hopefully) the performance of my 2 blade
>    13-8 prop.
>    As you can imagine I'vd been spending a lot of time at Google
>    University and on the vic prop calculator!
>    Dave
>    Ginseng 574
>    On Jun 28, 2021 19:47, Gordon Laco <[3]mainstay at csolve.net> wrote:
> 
>    Check out Skene’s Elements of Yacht Design.  There will be information
>    there to allow you to make a good estimate.
>    I reckon you already know that if your boat has an Atomic IV, it has
>    direct 1:1 drive.
>    Gordon Laco
>    426 Surprise
>    [4]www.gordonlaco.com
> 
>    On Jun 28, 2021, at 6:44 PM, David A. Bardsley via Public-List
>    <[5]public-list at lists.alberg30.org> wrote:
> 
>      I'm designing my drive's reduction ratio and the resource at my
>      disposal requires our A30's prismatic coefficient as a part of the
>    drag
>      calculation.
>      Can anyone share a decent figure for our craft?
>      Dave
>      Ginseng 574
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> References
> 
>    1. http://www.gordonlaco.com/
>    2. mailto:davebardsley at eastlink.ca
>    3. mailto:mainstay at csolve.net
>    4. http://www.gordonlaco.com/
>    5. mailto:public-list at lists.alberg30.org
>    6. http://www.alberg30.org/store/A30supporters.html
>    7. mailto:Public-List at lists.alberg30.org
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-- 
Kris Coward					http://unripe.melon.org/
GPG Fingerprint: 2BF3 957D 310A FEEC 4733  830E 21A4 05C7 1FEB 12B3