Gentlemen, hopefully to help show how pitch effects performance on an electric drive, here are a couple of tables I complied from readings I took on my sailboat Chiquita, a C&C 29 Mk 1, in 2014, the first year of my conversion. As indicated in the heading information I have a 12" diameter PYI Max 2 blade feathering prop in which I can adjust the pitch of the blades when out of the water.
The first table is an average of four test runs, in/out, in flat water, with no tide or current and the pitch set at 10 inches as recommended by PYI for this initial installation.
The 2nd table is under the same conditions a little later in the year, with the pitch set at 7.2 inches. Note the significant reduction in energy requirement for the same throttle setting. Also note however, the correspondingly reduced speed and maximum speed. I chose to reset to the 10" pitch to retain 90% of my original hull speed with the previous Atomic 4. A further note for comparative purposes, my original pitch setting with the 25 hp Atomic 4 the electric drive replaced, was 6.4 inches or 16 degrees and max speed in flat water was 5.7 knots.
This coming season I plan to set a 11 and possibly a 12 inch pitch and due further tests.
| Electroprop E-7 | Owner: | Jamie Storey | ||||||||||
| Shediac, NB | Canada | Propeller: | PYI Max 2 blade | |||||||||
| Boat Name: | Chiquita | FIN Keel | feathering adjustable | |||||||||
| Make & Model : | 1977 C&C 29 Mk I | Pitch: | 10 inches | 24 degrees | ||||||||
| Displacement | 7,600 lbs | Shaft Seal: | New PYI Dripless | |||||||||
| LWL | 23.58 ft | Controller: | Sevcon 4 | |||||||||
| LOA | 29.6 ft | Throttle: | OEM Controls Dial | |||||||||
| Batteries: | 4 x 215 amp Odssey PC1800 FT | Volts: | 48 | |||||||||
| Average - Based on Last Four Trials after motor and new dripless seal worked in 2014 | |||||||||
| Flat Water | |||||||||
| Throttle | |||||||||
| Setting | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 | ||
| Amp draw | 2.5 | 6.5 | 12.5 | 19.3 | 31.3 | 45.5 | 70.7 | ||
| Knots | 1.6 | 2.0 | 2.6 | 3.3 | 3.9 | 4.4 | 5.0 | ||
| RPM | 602 | 837 | 1061 | 1266 | 1500 | 1720 | 2003 | ||
| voltage | (estimated) | 51.3 | 51.1 | 50.9 | 50.6 | 50.4 | 50.1 | 49.2 | |
| Power | (Kw) | 0.13 | 0.33 | 0.64 | 0.98 | 1.58 | 2.28 | 3.48 | |
| Notes - 1. Slight vibration of prop at 4.5 throttle | |||||||||
| 2. RPM's oscillate slightly after 3.5 throttle so we took average |
| Average - Based on Two Trials in/out after Pitch reduced to 7.2" or 18 degrees. |
| Flat Water | ||||||
| Throttle |
| 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 |
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| Amp draw |
| 2 | 4 | 6 | 10 | 16 | 24 | 34 |
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| Knots |
| 1.4 | 1.8 | 2.1 | 2.5 | 2.9 | 3.6 | 4.1 |
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| RPM |
| 603 | 828 | 1022 | 1260 | 1480 | 1768 | 2008 |
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| voltage | (actual) | 51.3 | 51.1 | 50.9 | 50.6 | 50.4 | 50.1 | 49.2 |
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| Power | (Kw) | 0.08 | 0.18 | 0.31 | 0.48 | 0.78 | 1.20 | 1.67 |
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A couple of pictures of the prop and the throttle to add to the explanation:
Posted by: Avalon@nbnet.nb.ca
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