Shaft Angle

Looking at the WarP-9 graph I am unable to identify a 144-200 Kw range.
I see 32 hp as the upper limit.
For a boating application you will run the motor around 2500 rpm - assuming direct drive - where it develops 22 hp and draws 250 Amps from a 72 volts battery, so approx 18 kW.

Am I overlooking something or do you have a different graph?

You can position the prop near the transom if that suits you. It will have some adversely effect when backing up because there is no hull to prevent the prop from pulling air. I use such a setup several years already and see a vortex starting at 700 rpm. At 1500 rpm (prop) it is very noisy and moves more air than water. To me that's no problem because there seldom as a need to back up more than a few ft.

 

It is not at all good to have the propeller at the transom. It will suck air from the surface and that will ruin its performance. The same is true for the rudder--it should be positioned all under the boat and well forward of the transom. The rudder can also suck air which will cause it to lose lift and turning ability.

See the diagram attached. This is Figure 9 from an article in Professional Boatbuilder magazine, issue #78, Aug/Sept 2002, called "Rudder Design for High Performanc Boats," by Don Blount and Dudley Dawson. It shows the positioning of the rudder and propeller in relation to the hull. Dave Gerr also wrote a series of articles for PBB in issues #98, #99, and #100, in Dec/Jan, Feb/Mar, and Apr/May 2006 called "Steering System Fundamentals" which covers steering design for all types of boats, power and sail. See also Dave Gerr's excellent book, "The Propeller Handbook," published originally by International Marine Publishing, for everything you need to know about propellers.

Eric

 

That's a huge help Eric, thanks again!

CDK- Those numbers on the graph are baseline numbers using a 350amp controller. I'll be using Netgain's 1400 amp controller so the power levels are a bit higher. They use those motors in electric cars (drag race cars as well) If you google 'White Zombie electric car' you'll find a car that runs 2 of the 9"motors. It does 10.258sec runs in the quarter mile. I wont be running it that high all the time, would just cool to be able to throw out some power if needed you know?

 

One other thing Eric, if I run a cavitaion plate off the transom it could make up some of that distance right?

 

Yes, it has to be fairly wide, I'd say as wide as the diameter of the propeller. Fore/aft length probably half the diameter of the prop.

Eric

 

Ns,

I am not a designer, I have just worked in the industry since I was 18. If you want to plane, you will use a significant amount of the available power to get over the hump. Once there the power requirements stay high. Most planing boats use around 70% of the available hp at cruising speed.

These boats were significantly overpowered originally for racing, and I can't guess at the power requirement to get it up on a plane, but let's guess around 50hp. That converts to just over 65kw.

With your installed battery pack, assuming 100% efficiency, and no heat loss. Your battery pack hold roughly 75kw on the day they were manufactured. Subtract 1% for every month after that. So if you operate at less than a third of the power the boat was designed for, you can run for about an hour. But you would also be capable of draining the entire battery pack in around 15 minutes.

But Li batteries can only be brought down to around 1/2 of the available power before they stop working and permanent damage occurs. This means your available power is only good for ~30 minutes at low speed cruise, and 7.5 minutes at high speed.

Remember that Li packs have to be kept cool, and fast discharge and charging heats them up. This negatively effects the lifespan of the battery pack. Loss rates vary by temperature: 6% loss at 0 °C (32*°F), 20% at 25 °C (77*°F), and 35% at 40 °C (104*°F). This is the annual permanent loss of capacity. So presuming your average temperature is 77 you permanently loose around 20% capacity a year. This is why Li computer batteries have to be replaced regularly. Excessive heat, even spike temperatures can also accelerate battery degradation.

In addition you may need to check with your jurisdiction, but large Li packs in the US have significant transportation restrictions, and may be treated as haz mat in large quantities.

 

Nothing for the moment can beat the efficiency of a diesel engine.
Renato "Sonny" Levi put the engine and shaft at 14 degree on "A'Speranzella" and went to win the Cowes-Torquey race.
High angle was quite common time ago. Nothing wrong with that, providing the engine stay well lubricated and the prop designed for this condition.
Lister

 

Hmm, where to start. Funny how a question about the angle of a strut gets turned into a hater party. Leave it to an attorney
Well, as far as the battery goes, I should have been much more specific I guess. It's a lithium iron phosphate (LiFePO4) battery. Which if you would have read the very next line on Wikipedia, where it seems like you got all your info from because it's basically word for word from the site, it stated "In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge." or how about "one key advantage over other lithium-ion batteries is the superior thermal and chemical stability" or "Lithium Iron Phosphate chemistry also offers a longer cycle life over standard lithium ion cells." or "cycle life (number of cycles to 80% of original capacity) = 2,000–7,000" or "One of the other major advantages for LiFePO4 when compared with LiCoO2 is higher current or peak-power rating" Oh, and your pack losses you stated by temperature are from a fully charged pack sitting over time, not the discharge rate or capacity that can be discharged because of temperature...These packs can be discharged at 3C (3 times it's capacity=300amps constant) with 10C pulses from 14.4 volts down to 11.2 (which is pretty close to the 11.5-11.6 that a standard 12volt lead acid battery shows when it's sitting at 20% state of charge)
Wow, wasn't that fun! I'm sure you'll come up with plenty of disadvantages to contradict everything I just wrote, because it just seems to be your nature. But honestly, I could care less to hear about it, because just about anybody could find something negative to say about just about anything....

Anyways, if you dont like my plans, fine. I hear you loud and clear. The one thing I DID NOT hear from you was any input what so ever about the shaft angle. Where is your 18 years of experience on that question???


Hey Lister- Yeah, you cant beat a good old diesel when it comes to efficiency, but its not quite my cup of tea...at least on this project. I'll check out that boat though.

 

Don't get bent out of shape nsmoracr - it's all connected.

You have a hull that was designed to be a small fast planing boat. Now you want to load it down with a ton of battery weight. All the electric boats I've seen run a displacement hull.

What speed are you aiming for and what do you calculate your battery weight at?

P.S. I'm not a "hater" - spend your money on experimentation and I'll give you a round when you succeed I look forward to the day when an electric can replace gas, but I'm not holding my breath it will be 10 years. I'm watching http://www.cwecosport.com/

 

Ns,

I am anything but a hater. We get about a thread a week on the use of hybrid technology to operate boats. And your decision falls exacally into that mold. Now I didn't attck you personally, just your ideas, and I would appreciate the same courtesy.


As for using LiFePO4 batteries, they certainly do have advantages over traditional Li batteries, and seem to make sense in this type of installation. To the extent that an electric boat makes sense. You might want to confirm that your pack has a fast enough draw down rate to power the engine you are using since I know they have maximum draw down speeds that are lower than traditional batteries, but I don't know them off hand.

Additionally I don't have 18 years in the industry. I started working in the marine industry when I was 18. I grew up living on boats, primarily in the souther Carribean, then got my 100ton license when I was 18 and worked as a private captain for years. Primarily on power boats, but also on large racing sailboats. Then went back to law school and am a Maritime attorney now. My engineering background is only practical, and I am the first to admit it has holes. However I have worked with people building electric boats in the past, and tried to work through the problems I raised, to no avail since the power demands were just too high.


FMS

In this application the weight of the batteries and electric drive is actually less than the engines these boats were built to use. Most of them were designed around big block 6 cylinders, with a few converted to v8's. I don't think weight is the problem here at least.

And the reason most electric boats use displacement speeds is that it is the only way to get reasonable range from the power available in batteries. Though if you accept distance limitations planing hulls can work, they just don't go far.

 

Yes, I am aware of the 'White Zombie', it has been discussed here in a thread about hybrids a few years ago.
Unless you put wheels on your boat and run it on tarmac you cannot reach the power levels they are talking about (there are also considerable flaws in their calculations).

If you want to get much more than the 22 hp I've estimated from this motor, the use of a transmission is inevitable. At twice the rpm much more power can be transferred before the prop looses its grip on the water.

 

Ok Stumble, sorry for the 'personal attack'. I am my ideas though... But I will say that was your most constructive post yet. J/K. Maybe if you would have just asked if I have considered than range limitations this could have been avoided in the first place. Anyways, I am a little curious a out said electric boat. And thanks for the concern about wasting my time and money. Battery technology has come a long was in just the past five years, so I'm betting they'll advance a bit more in the next five. By that time I should have most of the drive issues resolved and the range will be extended.

 

CDK-

I wasn't sure what was out there in the marine world as far an overdrive type transmission. Since the DC motors have such high torque at low rpms but the power falls off as rpms increase, is there a 1:2 or maybe even a 1:3 that you are aware of??? One of my buddies thought I should use a wide cog belt (like a supercharger belt) but I wasn't too thrilled about that idea. I guess it might work if I fab'd up a sturdy enough support to handle that amount of torque, but I would like a sealed transmission better. Do they make v-drives with overdriven gears?

I know that the power levels will be totally different from that car to a boat because the prop/water grip is different than rubber/asphalt grip. I was just stating that the motor has the potential to apply huge amounts of torque. I see what you are saying about the rpms it gets that power at and how a normal prop for this boat just wont work properly at those low rpms. I'll have to so some more homework on the transmission. If you know of something that might work or where a good place to look would be, let me know.

 

Ns,

Specs and technical drawings for Casale Split Case V-drives can be found on our website's Transmission Page. Scroll down to the entry for Casale transmissions.

In the section titled Shaft Angles & Layouts - Drilling the Shaft Hole, you'll find links to online content from Glen L. Witt's book Inboard Motor Installations (Chapter 6 : V-drives, Chapter 11 : Shaft Angles & Layouts, and Chapter 12 : Making the Shaft Hole).

You may want to order the book and peruse Chapter 2 which discusses motor location and hull balance. Locating the motor between the front seats is going to cause a bow-down trim angle. The book will tell you how to do a Weight Study and balance the hull.

For help rigging your Rayson Craft, check out the Forum at v-driveboat.com : http://www.v-driveboat.com/forum.php

Follow the link in our sig line to see photos of our V-drive installation.

Hope this helps !

__________________
Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod : http://www.boats.chelseacoachworks.com

 

@nsmoracr.
Your post #28 (email version) contains the correct power calculation. In the WarP-9 graph the torque drops at higher rpm because it is a series wound motor. To get the 70 ft/lbs back at double rpm the input voltage must be increased accordingly.

A wide belt is not a good idea because the motor has a thin shaft: the pulleys do not stay perpendicular and will eat the belt.
For sealed transmissions look at Reliance, Catep Int'l or Radicon (formerly David Brown), they all make compact 1:2 and higher transmissions.