dear knowledgable members,
with pleasure i've read your interesting, thorough and often detailed post - what a joy to see so much expertise. i hope I could make use of that knowledge and ask for advice and recommendations on my little boat.


I is a small boat in the canals in amsterdam, just take it out to go cruise along the canals and sometime cross the IJ river for a restaurant/swim/friends on the North side of Amsterdam.?

It's a former safety boat, presumably built around 1920, riveted steel. 5,5m/18ft long, 5,2m/17ft at the waterline. she is aprox 1.85m / 6ft wide at the widest point. Guesses are about 1 ton without engine etc. These are some speed test i did a while ago;



Now powered by an old 21HP 3cylinder diesel i'm looking to change to electric this year. (Amsterdam city government issued rules to ban all diesel engines from the city centre by 2025).

I usually have trips of 3-4 hours, that may include the 20 minute full-power (about 11 kmh) trip to the North of Amsterdam (and 20 minutes back). Most of the time i cruise 6-7 kmh (3.5 knots?).
I maybe have 20-ish trips a year, also of 1,5-2hours, so say 50 hours a year - all in all an expensive hobby, but with friend on the canals, with a beer or wine and some snacks, cruising to the take-away pizza on the canal, romantic candlelight tours - it makes it worth it (well as long as you can help me do this electrification....)
The boat is docked next to my houseboat so charging is no problem.

no need for a lot of power but i do need be able to break quickly and have some manoeuvre power, also when i have 8 friends on board.

I was hoping on some recommendations on;

1. power estimates the engine
2. direct on ax or via belt (what happens with an emergency brake?)
3. how to mount/install, on the current engine mounts with or without the rubbers (need a custom made frame)?
4. what kind of propellor (don't know what i have now)
5. brushless or are older/cheaper engines an option considering my hours/year.
6. power need on 6-7kmh vs hullspeed (10,4? kmh); is if fair to say that at 6-7kmh poweruse is only 30% of the energy that is needed for the hull speed?
7. what kind of batteries would be advisable for me. the boat is in the water (and could be on power) all year. In Amsterdam it it maybe 10 nights a year freezing a bit, never more then -10 Celcius

I've seen the kits from??and??but wonder if they are my only (affordable) choice, and, cautious about how to mount them.
I realise most of the converstaions here have been on sailboats and mine is different, still i hope you can educate me with your expertise,

Thanks,
Elwin

On 8/3/22 05:37, looije@... wrote:

dear knowledgable members,
with pleasure i've read your interesting, thorough and often detailed post - what a joy to see so much expertise. i hope I could make use of that knowledge and ask for advice and recommendations on my little boat.

I converted a 5m fiberglass half-cabin 'launch' of similar hull shape. Mine previously had a 5.5hp 2-stroke 2 cylinder petrol engine.



I did the conversion over 10 years ago now, so the tech has matured more now. In particular there are multiple repower kits now available. Focused on sail auxiliaries, but an inboard is an inboard.

I would consider lithium batters only 48 volt bank the prices are coming down and the last longer .

I think you should really look at the sail boat system there bench marks are way more geared to hill speed or slower

Here is a video I made of how I figured out what I had and need
Right wrong or indifferent this works for my little boat 22 footer
DIY Electric Inboard -Tails of Speed, Torque, and Prop Pitch

i've been a bit distracted the past couple of weeks but have some data on the current propellor and rpm.?

I have a (odd) 400 mm diameter , 290mm prop.?
my current engine runs stationary with a propspeed of 340rpm with a speed of 3.5kmh (1.8/19.9knots) - i like to go a bit slower then that as well
at 545 rpm the speed of the boat is about 3 knots
600 rpm 3,5knots
840 rpm 4,5 knots
975 rpm 5 knots, about max speed on the engine.
i'll probably cruise around 500-700rpm 90% of the time.?
but do need to brake/manouvre and cross a big canal occasionally, so woudl like to get 900-1000 rpm sometimes.

Taking into account my attempt to keep the prop (as long as it's not against me), i was hoping to get some advice on the engine. is a used 48v dv (series wound) dc engine a possibility? I'm trying to avoid a brushless because of cost of engine and controller.?

also I thought to find an engine with a low rpm to make it work without a reduction (less elements, less costs, less noice).?

Any thoughts?

Trying to save money by avoiding an efficient motor and speed controller will force you to spend more than you need to on batteries. I recommend that, to minimize the overall system costs while achieving your performance goals, aim for an efficient design rather than trying to cut corners too early in the process.

开云体育

I agree with this.? And the battery is the only part of the system that is scalable.? You can save some now with? smaller battery bank and expand that later.?

Dan Pfeiffer

hi, last summer I started this post, now a bit further in the process - I've purchased a used set, the best I could afford now - knowing that I need to do some adjustments to make it fit my situation.

Can you share your thoughts on setting up my system? I like to keep most parts in tact, of course, but can imagine changing some elements may be the best option.?

what there is now;
an?16x11 inch prop?400 mm diameter , 290mm prop., there is room to fit a bigger one.?
my most used speed will be around 6,5kmh, around 500-700 rpm on the shaft?
good fit or replace?.

I bought a I think to powerful, but works 12-72v. As per their site, the ME1003 is designed to run 3000rpm at 72v, "This ME1003 is a Brush-Type, Permanent Magnet DC motor with very high efficiency. Capable of 11.5 KW continuous and 20 KW for 30 seconds (at 72 VDC). For voltages from 12 to 72 VDC input and 200 amps continuous (400 amps for 30 seconds ). "

I have 8 6volt 330ah batteries AGM

It may not be an ideal mix, but It's not a sailing boat, I just like to cruise the Amsterdam canals for a couple of hours.?
Need some power to manoeuvre when it's busy, and when crossing the river.?

I read a lot about higher efficiency at higher RPM, that would suggest reduction. But is that effluence difference significant?
would a direct connection to the ax be nicer, as it requires less rpm (less noise)?
Should I make this a 24 or 48 volt set-up?
(I'll probably want to change to Litium batteries when the AGM batteries I have die (in a couple of years?)).

How can I determine if I have enough power (torque?) in on 24vollt??
is cabling for lower voltage a significant costs compared to a higher voltage??

hope you can help me some pieces of this puzzle,
thanks!

600 RPM at 11-inch pitch will come to around 8.5mk/h (allowing 15% slip).

Unsure if your motor will have enough torque though.? Seems like it will only be putting out ~2kW at that RPM.

If you have a previous reference for power consumption at various speeds for your boat, that would help.

Thinking you want closer to 8" pitch, then you can bring RPM up somewhat, which will get more total power out of the motor.

Yes, prop efficiency will suffer somewhat, but without more torque from the motor, something has to give.

The above is all assuming direct drive to the prop.? A 2:1 reduction helps with the total power issue,
allowing use of 24V instead of just 12V.? Obvious downsides of more complexity, noise, and drivetrain losses.

Thanks Bobkart,?
I only have references below on 'power consumption', so not really. This if what I measured with my old diesel engine. 340rpm is almost neutral. 9.3 kmh is not far from max speed.

rpm	kmh
340	3,5
540	6,1
600	6,5
845	8,6
975	9,3

S0 maybe there is more slip? I've added some photos of the boat.

You're suggesting a smaller prop, so I can make more rpm, so the engine will be efficient, right? if max rpm on 48v is 2250 (according to Monterey) then 24v will be 1125, right??
That's not that far off on the max rpm I expect I need with this prop.
If cruising on 50% of that max rpm @ 24v, is that a situation that needs to be improved??
by a smaller prop with direct drive
or
with the same prop with a 2:1 reduction at 48v??
is my thinking correct??

and what would be smart to do :-)
thanks again
elwin


i?

just to add,?

I remember from earlier research that a 4kw engine would probably be fine to bring the boat to hull speed. (10,5kmh, 1000/1100 rpm).

would that imply that 1200 watt would be enough for cruise speed?

I have trouble understanding the graph of the ME1002, but at 24v (rpm range would fit), would the efficiency then drop If on cruise speed (and is that a problem?)

?

Thanks

It does seem like you were experience more than 15% slip with the diesel.

Elwin's idea of just assuming you'll need a reduction and putting one in is a good one.? It doesn't look like direct drive will give you enough power (overpropped).

Keep in mind that lower prop RPM is usually more efficient.? I.e. the efficiency hit of a prop mostly comes from drag through the water, which goes up faster than linear.? Keep RPM lower and pitch on the high side and you'll win compared to less pitch and more RPM (generally).? The challenge with direct drive and your current motor is that your target prop speed of ~600mph is too low for your motor power-wise.? This is actually a general challenge for electric boat motors, and why axial-flux motors are brought into play.? If you end up needing a different motor, that'd be a good direction to consider (Lynch for example).

Once you have the ability to introduce nearly any reduction ratio you want to try, various combinations of battery voltage and reduction ratios can be experimented with.? If 4kW can hit hull speed, it sounds like 24V and 2:1 reduction seems close to ideal.

As a final consideration, you may be very close to being able to hit a decent cruising speed (~6km/h) at full throttle.? But, you usually want some headroom, and not run at maximum current 'all the time'.? Wind/current/heavy-load will be more difficult to handle if you're at max power just cruising.? So 24V / 2:1 seems like the obvious first thing to try.

Dear Bobkart,
thanks again. I understand your reasoning on the 24v / 2:1 reducing IF full throttle is for cruising speed at 600 rpm.
But I want full throttle to be hull speed, say about 1100rpm.

so that would either be 48v with 2:1, or, 24v without gear reduction.

That brings me back to the questions, would this me1003 engine be terribly inefficient at 500-600 rpm ? ?Or what other parts influence the lower or higher voltage use (Peukert effect?)
I was finding the following numbers;

48	rpm per volt	?	?	?	?	?	?	?	?
RPM	?	?	?	?	?	?	?	?	?
450	slow	5	kmh	0,5	kw	9,375	volt	53,3	amp
600	rpm cruise	6,5	kmh	0,9	kw	12,5	volt	72,0	amp
975	reasonable fastest	9,5	kmh	2,85	kw	20,3	volt	140,3	amp
1050	theortaticly hull	10,5	kmh	3,85	kw	21,9	volt	176,0	amp

Thanks
elwin

I produced this table from the first row and it looks like 48V might be a better solution.
I was basing the 24V suggestion off of your statement that 4kW can hit hull speed.
But that's with no headroom for current/wind/heavy-loads: