Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 09-12-2019, 19:16   #61
Registered User
 
double u's Avatar

Join Date: Feb 2016
Location: Tahiti
Boat: Elan 410
Posts: 1,617
Re: Could one use boat propeller to drive el generator?

& driving a shaft generator is a total different situation from a -theoretically frictionfree - freely rotating prop. Any electric energy has to be produced by the sails & therefore is not available to drive the boat. It isn't going to be much (7A x 16V =112W as an example) so just over 1/7hp
__________________

__________________
...not all who wander are lost!
double u is offline   Reply With Quote
Old 09-12-2019, 19:47   #62
Registered User

Join Date: Nov 2018
Posts: 11
Re: Could one use boat propeller to drive el generator?

Yes you can. Forget using an alternator. Not enough torque for the rpms needed. There was an older post here in the forum.
http://www.cruisersforum.com/forums/f14/permanent-magnet-generator-on-propshaft-22266-5.html
I have read his research on two different sites. His figures are sound vs oceanvolt. If you are not a tinker, an easier way would be to use a 600watt 12 volt PMA from aliexpress.. Takes 600 rpm to achieve max watts. Put a ac clutch on the generator like Harold did and you can run the motor with now worries, just disengage the clutch. A prop for a boat is not the same as for hydro but it will still work. That is how oceanvolt can generate so much power. Their prop adjusts to the correct pitch for thrust and hydro. You lose about 33 percent power generation. Its a compromise without blowing several thousand for a towed array.


https://m.aliexpress.com/item/32879164158.html?trace=wwwdetail2mobilesitedetail& gps-id=storeRecommendH5&scm=1007.18500.139671.0&scm_id =1007.18500.139671.0&scm-url=1007.18500.139671.0&pvid=7f5ee7df-2125-4dc8-ae17-056d0c38eef1&_t=gps-id:storeRecommendH5,scm-url:1007.18500.139671.0,pvid:7f5ee7df-2125-4dc8-ae17-056d0c38eef1&spm=a2g0n.detail-amp.sellerrecommend.32879164158&aff_trace_key=7b03 4378c9c448e5a275d92add2dc408-1575030911156-08131-5dnnyP8k&aff_platform=msite&m_page_id=3354amp-qPXhXz6ttPcQ_DTL-okTqg1575945658888
__________________

QuentinC is offline   Reply With Quote
Old 09-12-2019, 20:05   #63
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 10,263
Re: Could one use boat propeller to drive el generator?

Quote:
Originally Posted by double u View Post
& driving a shaft generator is a total different situation from a -theoretically frictionfree - freely rotating prop. Any electric energy has to be produced by the sails & therefore is not available to drive the boat. It isn't going to be much (7A x 16V =112W as an example) so just over 1/7hp
This is true however the wind (via the sails) will often be supplying more power than the hull can use. This is one of the many reasons why we reef!
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 09-12-2019, 22:22   #64
Marine Service Provider
 
LifePart2's Avatar

Join Date: Sep 2010
Location: ex Canada - now on the boat
Boat: Leopard 42 catamaran
Posts: 161
Re: Could one use boat propeller to drive el generator?

We did put a prop shaft driven alternator on Life Part 2. It worked great at 6+ knots - until we switched to a folding prop and installed lithium batteries. That put an end to the experiment.

The full account is here: LIFE: Part 2: Prop-Shaft Driven Alternator

Noel
__________________
Noel Swanson

Life is too short to live in ugly places.
LifePart2 is offline   Reply With Quote
Old 10-12-2019, 02:01   #65
Registered User

Join Date: Jan 2018
Posts: 34
Re: Could one use boat propeller to drive el generator?

Click image for larger version

Name:	IMG_5725_Original.jpg
Views:	23
Size:	93.6 KB
ID:	204719Click image for larger version

Name:	IMG_5671_Original.jpg
Views:	22
Size:	358.5 KB
ID:	204720

I fabricated and installed two shaft driven generators on my twin engine sailboat. The key concepts that made this very doable were:

1. Fabrication of split pulleys (so I didn’t have to disassemble the shaft from the gear box to install the pulleys). I cut in half standard aluminum pulleys, hollowed out the center to fit my shafts, then coupled them back over the shaft using the shaft-gear bolts.

2. Use of A-link v-belts (again, so I didn’t have to disassemble the shaft to get the v belts on, and also so I can easily tweak the length of the belt to match my install). With A-link belts you first size the belt by removing appropriate number of links, and then re-link the belt around the shaft.

Here’s the link to the belt I used (there are other A-link belts that exist, this is just the one I chose):

Jason Industrial A-LINK-5 Accu-Link V-Belt Belting, 1/2 inch https://www.amazon.com/dp/B00A9ZNE7C..._fG17DbS83JGGF

3. Use of high-voltage low rpm permanent magnet dc motors for generators (so Im generating DC not Ac and didn’t have to use rectifiers which alternators need. I used 72v DC Ametek motors bought off eBay ~ $40)

4. Use of a Solar MPPT controller to regulate and convert the speed dependent high dc voltage output of the PMDC motors down to 12V dc charging voltage. I used a MorningStar MPPT 45 charge controller - same family of charge controllers I use for the 820W solar on same boat. You want a motor that can generate high voltages at low rpm. This high voltage can then be down-converted to excess current at 12v dc via MPPT circuitry. The Morningstar MPPT I used can handle up to 150v dc, though in actual operation at normal speeds I rarely see above 50v dc input.

Attached are photos of the final product. Have two identical installs, one for port engine other for starboard.

Pulleys are 6.6” (split, on prop shaft) to 1.75” (on PMDC motors) for an almost 4:1 ratio.

Props are 3-blade 16”.

System works beautifully. Props start freewheeling at about 3 kts (and stop freewheeling at about 1 to 2 kts). At 3kt 5 amps can be generated. I’ve seen over 15 amps generated (at over 6 ~7 kts of boat speed surfing down waves). Steady state average generation at normal speeds is 10 to 13 amps. This may seem small compared to solar (my solar peak generation is over 40 amps) however over the course of an average day, the props typically generate more than twice the total energy (>200 amp-hours) compared to my solar (100amp-hours).

On a recent CA to HI leg, I was energy-positive (more than enough energy for autopilot, nav instruments, refrigeration, and via inverter a washing machine and electric galley).
Seafarer7 is offline   Reply With Quote
Old 10-12-2019, 02:23   #66
Registered User

Join Date: Jan 2018
Posts: 34
Re: Could one use boat propeller to drive el generator?

Click image for larger version

Name:	IMG_4991_Original.jpg
Views:	27
Size:	185.2 KB
ID:	204723Click image for larger version

Name:	IMG_4994_Original.jpg
Views:	26
Size:	85.2 KB
ID:	204724Click image for larger version

Name:	IMG_6177_Original.jpg
Views:	28
Size:	207.8 KB
ID:	204725

These photos show the “split pulley”: a regular aluminum pulley cut in half and reattached around the shaft.

Also shown in one of the photos is the “split belt” (A-link belt in its split state, prior to re-linking around the shaft).

Btw: these A-link belts make a good easy-to-install spare belt for other systems such as engine water pump and regular alternators. I carry some extra onboard as emergency spare.
Seafarer7 is offline   Reply With Quote
Old 10-12-2019, 02:26   #67
Registered User

Join Date: Jan 2018
Posts: 34
Re: Could one use boat propeller to drive el generator?

Click image for larger version

Name:	IMG_7204_Original.jpg
Views:	21
Size:	200.9 KB
ID:	204726Click image for larger version

Name:	IMG_7205_Original.jpg
Views:	22
Size:	207.8 KB
ID:	204727

Final installations : one on port engine the other on starboard engine.
Seafarer7 is offline   Reply With Quote
Old 10-12-2019, 03:05   #68
Registered User

Join Date: Jan 2018
Posts: 34
Re: Could one use boat propeller to drive el generator?

Results
These are actual “in-use” data, (solar and hydro generator snapshots) taken from two different scenarios
(A) Captured in daytime, cloudy, with boat near hull speed, estimated to be going 6 - 7 knots.
(B) Also daytime, sunny near solar noon, boat speed estimated at 3-4 knots.



To understand the displayed data and photos (which are screenshot of the onboard energy-monitoring computer) one needs to know these are the outputs of 3 MorningStar MPPT Solar Controllers:
- 2 dedicated to solar panels (a 300w bank of panels and a separate 520w bank of panels) and
- the third dedicated to the two hydro-shaft generators combined (in parallel, with blocking diodes to prevent one hydro-generator from discharging into the other).


Case A: Cloudy, Boat was at or near hull speed:

MPPT#1 (300-watt solar) Output:
- 10.24 amps @ 13.5v (charge voltage) = 138.5 watts

MPPT#2 (520-watt solar) Output:
- 5.29 amps @ 13.47v = 71.3 watts
(This group of panels gets somewhat shaded by the sails)

MPPT#3 (the 2 hydro-generators) Output:
- 14.11 amps @ 13.5v = 190.83 watts

Total charge power into the combined 1225-AH battery bank (solar + hydro):
29.65 amps = 400.67 watts

Click image for larger version

Name:	IMG_1449.jpg
Views:	18
Size:	301.0 KB
ID:	204731



Case B: Sunny, Not much wind, Boat speed estimated at 3 to 4 knots:

MPPT#1 (300-watt solar) Output:
- 21.46 amps @ 13.22v (charge voltage) = 284.11 watts

MPPT#2 (520-watt solar) Output:
- 16.16 amps @ 13.19v = 213.35 watts
(This group of panels gets somewhat shaded by the sails)

MPPT#3 (the 2 hydro-generators) Output:
- 6.21 amps @ 13.19v = 81.96 watts

Total charge power into the combined 1225-AH battery bank (solar + hydro):
43.83 amps = 579.42 watts

Click image for larger version

Name:	IMG_1450.jpg
Views:	23
Size:	281.6 KB
ID:	204730
Seafarer7 is offline   Reply With Quote
Old 10-12-2019, 04:18   #69
Registered User

Join Date: Nov 2011
Location: 6 were made, locations unknown
Boat: Mose & Hoye Pty Ltd Ampopette class 39'10"
Posts: 5
Images: 3
Re: Could one use boat propeller to drive el generator?

Quote:
Originally Posted by suiramor View Post
When my boat is under sail, my (fixed) propeller is rotating (I did read the fascinating thread somewhere here whether to put it into gear, reverse or leave in neutral - I leave mine in neutral). However, I was wondering whether I could not jig up an electric generator to it. Would it un-balance the shaft? Why is it not done? (like the dynamos in the old fashioned bikes)
It depends, our Ampopetta had a Stewart Turner 10hp with a 3 to 1 reduction driving a 20x18 prop, max 500rpm. This was done with the engine backwards under the cockpit, to one side, 4 "V" belts drove the largish shaft mounted pulley! Got that? now if you dropped off the belts and ran on one to a generator it would maybe charge the battery. The wind/boat speed needed to be getting up designed hull speed to free wheel, SOO if you had a puny little prop forget it, get some solar panels as the drag is not worth it anyway IMO These days with LEDs the battery may be much smaller than what was needed in the 1960s. The Stewart had a v pulley on the flywheel we just used that to drive our generator as we did not do long trips, just harbour sailing with friends. Alternators may charge at car idle but a flat battery you may need 5-10 HP, you can see this idea is problematic, I guess our shaft speed freewheeling may have been 300 rpm, the large pulley giving you 900+ in a generator but I doubt the prop would have enough umph, you may have to use larger/smaller pulleys to make it work at all!
ozepool is offline   Reply With Quote
Old 20-12-2019, 17:57   #70
Registered User

Join Date: Feb 2010
Location: Ireland
Posts: 222
Re: Could one use boat propeller to drive el generator?

A propeller is the mirror image of a turbine rotor, so is not effective for power generation, As others have said, it you are sailing close to hull speed anyway, you won't be particularly concerned with drag or efficiency. At other times, it will slow you down considerably. You would be better with a folding/furling prop and trail an old fashioned log connected to a low-speed permanent magnet alternator/brushless motor
__________________

skenn_ie is offline   Reply With Quote
Reply

Tags
boat, generator, propeller, rope

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Always use a snubber or your boat could end up like... dreuge Seamanship & Boat Handling 285 05-11-2019 10:05
Propeller size , could someone help me out bobs Propellers & Drive Systems 31 29-10-2019 03:37
Buying a boat in Panama. Could use some advice, please. philaw Atlantic & the Caribbean 64 14-07-2019 10:26
Feathering Propeller, which one is this one? thaisail Propellers & Drive Systems 4 22-12-2017 18:21
San Francisco Live aboard slip (finally!) I could use help moving the boat. Vancefish Liveaboard's Forum 41 04-07-2016 16:44

Advertise Here


All times are GMT -7. The time now is 08:19.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.