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  #1  
Old 03-07-2012, 10:53 AM
gasman gasman is offline
 
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Default Don't give up on your RV-3 project...

If you are building an open cockpit 3 for local flights but worried about the price of fuel. Think about electric!! There will be many new and exciting things coming out in the next two years that will change the way you make that evening flight. And the RV3 platform is a good fit for it.

Complete the three cowl with a loaner O320 and stock mount. Then you will have that option in the future. The electric conversion will place the prop in the proper location. Batteries will be carried on the firewall fwd to true balance. The fuel tanks will be built to carry the remaining batteries.

So what do you get? An almost no noise, no vibration, perfect balance always, almost no maintenance thrill for pennys per KWH.
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Last edited by gasman : 03-07-2012 at 11:00 AM.
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  #2  
Old 03-07-2012, 11:18 AM
bkthomps bkthomps is offline
 
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ironic username given the post content
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  #3  
Old 03-07-2012, 11:54 AM
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RVbySDI RVbySDI is offline
 
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Just some food for thought concerning electric propulsion, here is a link to some news information concerning recent breakthroughs with battery storage capacities:
http://news.cnet.com/8301-11386_3-57...lash-ev-costs/

Here is the link to Envia. They are claiming to have achieved a major breakthrough in energy storage capabilities for Lithium Ion batteries.
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  #4  
Old 03-07-2012, 11:58 AM
aerhed aerhed is offline
 
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Still waiting with baited breath....hey, I smell caviar.
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  #5  
Old 03-07-2012, 12:00 PM
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rv7boy rv7boy is offline
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Quote:
Originally Posted by bkthomps View Post
ironic username given the post content
I thought the same thing. "Gasman" is in favor of an electric RV?

As to electric propulsion for the RV-3, I would hope to see it in my flying lifetime. The Chinese seem to have a leg up on us right now. But like Doug's RV-15, the pilot of an electric RV-3 would have to be content to fly within a set radius of his/her base airport. At least until battery technology advances even beyond its present state.

Airplane design is a very sophisticated set of compromises.
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  #6  
Old 03-07-2012, 12:28 PM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by RVbySDI View Post
Just some food for thought concerning electric propulsion, here is a link to some news information concerning recent breakthroughs with battery storage capacities:
http://news.cnet.com/8301-11386_3-57...lash-ev-costs/

Here is the link to Envia. They are claiming to have achieved a major breakthrough in energy storage capabilities for Lithium Ion batteries.
If I read it correctly, they claim 400 watt-hours per kilogram

About 180 watt-hours per pound

One HP is about 750 watts

So about 4.1 pounds per HP

So if hours flight is 75 HP average in a RV-3

That's a 307 pound battery, with no allowance for electric motor losses and no safety margin before the batteries go dead. I wonder how the FAA will calculate the "remaining fuel" FAR?

It's getting there, but much better for a self-launching sailplane (which you can buy now) than a fun RV-3...

Are my calculations about right?
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  #7  
Old 03-07-2012, 01:03 PM
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RVbySDI RVbySDI is offline
 
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Not sure of the calculations but I think it important to think about the differences in power needs for propulsion in the different phases of flight. The real question is what level of power (HP) does an RV-3 need for cruise flight vs what it needs for climb? If it takes quite a bit of the energy to get the RV to climb to altitude how much will be left over for cruise flight? And how much of that power is actually needed for cruise flight? Does an RV-3 need 75 HP to maintain altitude and XXX cruise speed? It is my thoughts that this is one of the reasons why the motor glider community is leading the way for use of electric propulsion. These gliders most likely are not going to need the high HP requirements to get them to altitude. Then it is also obvious they do not need any of that HP for cruise. Their needs for energy are then limited to a specific flight phase.

The RV-3, although relatively slick, is not as aerodynamic as other long wingspan low aspect ratio airframes such as gliders. Therefore it will require more HP at cruise than an airplane that may have more wing and less drag.

It seems to me the short stubby wing of our RV's might not be the best platform for electric propulsion.
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  #8  
Old 03-07-2012, 01:09 PM
Lux Wrangler Lux Wrangler is offline
 
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Default 400 cycles!

First it would have to be practical in a car, before it would become economical in the marketplace and be available for your plane. The article claims the batteries "perform well after 400 cycles". If you drive your car to work and back 5 days a week that's 10 cycles per week, or 40 weeks, or a lot less than a year, even if you don't drive on the weekend. Who would spend that much money for a car that needs a major, high dollar, component replacement in less than a year?
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  #9  
Old 03-07-2012, 01:23 PM
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Quote:
Originally Posted by RVbySDI View Post
Just some food for thought concerning electric propulsion, here is a link to some news information concerning recent breakthroughs with battery storage capacities:
http://news.cnet.com/8301-11386_3-57...lash-ev-costs/.
I wouldn't wait around for this one. Sounds great but they only want to sell the IP. Until someone is actually making them it's a long shot on the price/performance.
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  #10  
Old 03-07-2012, 04:31 PM
David Paule David Paule is offline
 
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Quote:
Originally Posted by az_gila View Post
If I read it correctly, they claim 400 watt-hours per kilogram

About 180 watt-hours per pound

One HP is about 750 watts....
Using your numbers and 160 hp at 65% power, with a 30 gallon tank. This gives me about 8.7 gph and about 3.5 hours at 104 hp. That's roughly 77,600 watts or 271,500 watt-hours of energy if my arithmetic is right.

At 180 watt-hours per pound, the battery equivalent to the 30 gallons of fuel will weigh very roughly 1,500 pounds. And that's without any mounting equipment, the motor or any other hardware or electronics.

To put it into perspective, the RV-3s built so far are running in the 695 to 890 pound range empty with their engines.

Dave
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