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Aerial Photography and Video > opinions on extending blades to 800mm for electrics
 
 
FLAP
Veteran
Location: Michigan

I am currently running a couple of Bergen Intrepid gas birds for AP. Not long after I started using them, I went to extended booms and 800mm main blades. I liked the upgrade for the gas engine as it had no real down side with the surplus of air time and power. However, I understand that with electric birds, which I'm considering, the extra blade length contributes to extra drag and reduced air time. For those of you with experience, is the trade off worth the extra main length?
(looking at Jokers and new Bergen Tazer)
05-07-2008 02:12 AM
 
 
cranester
Veteran
Location: Bogota, Colombia

Bergen's Tazer 800 swings 800 mm blades but they don't mention flight times or payload capacity, give Chris a call he will gladly help you out. If you already have two Bergens I would suggest the Tazer as most of the parts will be the same, but then again a Joker... Wow thats one cool helicopter.

Juan Crane
05-07-2008 02:49 AM
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ehx
Senior Heliman
Location: Northern Minnesota

Extra blade length would contribute to more drag and less run time IF you kept the same headspeed. Of course you don't. In going from 700mm blades to 800mm blades you can drop the headspeed by a few hundred rpm and get similar lift.

There's a reason why Minicopter advertises the Maxi Joker (800mm blades) as the "lifter" versus the 700mm regular Joker. As a general rule the 800mm blade helis can be a little more efficient.

Exactly what you want to lift and how you want the heli to perform can make a difference in picking a blade length, but to maximize flight time and/or weight lifting capacity go with the longer blade.
05-07-2008 02:56 AM
 
 
aerton
Veteran
Location: Longueuil, QC, Canada

I was experimenting with 550, 600,620 and 640 size blades on 30-50 size electric bird. What I found is, every motor has it's "prefered" blade size and prefered battery size. Going below it is inefficient.
For example lately I put 640 blades with 650A motor and 9S pack, the performance was significantly better than with 620 blades and same motor and batt. 640s are 100g heavier, yet the lifting power was amazing. Just by 2 cm. I had similar experience going from 550 to 600 with neu 1910-1.5y. The run time didn't reduce at all or practically, but the power was higher. So if I were to go from 710 to 800 I would primarily question the motor itself and probably increase the batt pack by a cell or 2. But if the motor "loves" 800 blades it would be very noticeable increase in performance.
05-07-2008 01:12 PM
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AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
However, I understand that with electric birds, which I'm considering, the extra blade length contributes to extra drag and reduced air time.

The instant you decide to go with electric power efficiency becomes your greatest concern. There is no magic battery technology even today. The amount of energy that you can store in a battery vs. liquid fuel is hundreds of times smaller.

Efficiency in an electric helicopter is dependant on blades, yes, but also on gearing, headspeed, payload and motor design. You can’t make an assumption that a longer or shorter blade is better without considering the gearing, headspeed, payload, motor and power source. That is what makes electrical powered helis black art (far too many variables). I would say the best bet is to query the electrical forums for a specific model that you like as to how it is set up based on what already has been tried. Keep in mind that an electric power plant will always have a limited hang time when compared to liquid fuel. This is the biggest nut to crack when trying to solve our dependency on foreign oil. It takes more energy to power an electric car than it does to power a gasoline car. What appears to be a green solution is not so green.

Ace
What could be more fun?
05-07-2008 09:13 PM
 
 
Autoeject
Key Veteran
Location: Ashtabula, OH, USA

I've asked Chris a few questions about the Bergen electrics because I'm considering converting one of the gassers I've got over to electric. Configured more like the E-Observer, I believe he said I should be able to pull off 15-18min flights. This is more than enough for most of what I'll be needing.
If I'm off on that info, I'm sure Chris will set us straight. From what I understand, he's been doing a lot of work to get the Tazer/E-Observer helis dialed in for the optimum combinations. I'm just happy Bergen decided to get into the E market.

Mark Webber
webberaerialimaging.com
Spartan RC Distributor
Outrage Helicopters
05-07-2008 09:31 PM
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wlfk
Veteran
Location: uk

Quote 
It takes more energy to power an electric car than it does to power a gasoline car.

I'm not sure that's true. Electric cars are very efficient in turning electricity to motion, and power stations are considerably more efficient than car engines at turning oil into power. On the other hand you lose a lot in power-line transmission and the energy that goes into making those batteries is going to be significant too.

My understanding is that electric wins out overall, though the calculation isn't simple.

K

A bit like a kite, but 500 times more expensive
05-07-2008 10:13 PM
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
My understanding is that electric wins out overall, though the calculation isn't simple.

Most people leave out the dead weight of the batteries that you are always carrying around. They also leave out the energy that the battery looses just sitting dormant when the car is not in use. And finally the energy to make the battery and recycle the spent batteries. The only way to make electric powered vehicles come on top is to produce electricity without oil or fossil fuels.

No matter how you slice it efficiency is paramount when considering electric power and with liquid fuel it isn't even considered.

Ace
What could be more fun?
05-08-2008 12:17 AM
 
 
tabbytabb
Elite Veteran
Location: seattle

Quote 
The only way to make electric powered vehicles come on top is to produce electricity without oil or fossil fuels.


Bingo, time for some nuclear power!



Also, too stay on topic I have found for upwards of 20lbs AUW the 800 blades are helpful in flight time, efficiency, and disk loading. Anything under 20lbs I would run 700 to 720 blades. The 800s fly like a dump truck and your amp draw really depends on the blade.

Ace, electric helis really are not a black art at all. A robust power system is fairly simple to find and easily reproducible. I would say keeping a combustion motor in tune and smooth is much more of a black art.


Tabb
05-08-2008 12:22 AM
HOMEPAGE  
 
 
FLAP
Veteran
Location: Michigan

That's what I was looking for, thanks. My AUW will be in excess of 20 pounds or close too it. Looks like 800's then.
05-08-2008 02:14 AM
 
 
tabbytabb
Elite Veteran
Location: seattle

Flap, I would go for NHP 800s or some semi symms then.

I prefer the fully symmetrical blades myself but some of the semis fly nice as well depending on what you need.

I would also recommend the joker 2 maxi as it has been nothing but excellent for me, but if you already have 2 bergens then their electric makes sense as well.
05-08-2008 03:04 AM
HOMEPAGE  
 
 
FLAP
Veteran
Location: Michigan

a difficult choice knowing MJ2's are proven product that's been out a while and used by top notch AP'ers vs Bergen's new bird...a product, in Gasser form, which has been very good for me (not to mention the excellent support I get from Bergen).
Their video of the new Bergen Tazer, with the Lithium-Mang batteries looked impressive. Probabably either would be very good...but the required financial investment requires careful consideration of options.
How's parts support for the MJ's?
05-08-2008 03:31 AM
 
 
Autoeject
Key Veteran
Location: Ashtabula, OH, USA

I wouldn't be concerned about choosing the Tazer because it's new. Since Greg Alderman lives so close, I've gotten to see the prototypes he's been flying for more than a year now. I'm sure it would have been released sooner but Chris was trying out various motor/esc/pinion combinations to achieve the best results. I'm sure he wouldn't release it unless he was sure it was the best it could be.

Mark Webber
webberaerialimaging.com
Spartan RC Distributor
Outrage Helicopters
05-08-2008 10:37 AM
HOMEPAGE  
 
 
FLAP
Veteran
Location: Michigan

Where's he live? I'll drop by to see one
I doubt if either is a bad choice. Hard to pick with a recommendation from Tabb for Joker and my general proximity to the Bergen factory and my positive experience with my Bergen Gassers.
05-08-2008 12:41 PM
 
 
Autoeject
Key Veteran
Location: Ashtabula, OH, USA

If you want to see one, I'd drop by the factory. Chris can demo the production model. We're in OH. No need to drive farther than necessary.

Mark Webber
webberaerialimaging.com
Spartan RC Distributor
Outrage Helicopters
05-09-2008 12:29 AM
HOMEPAGE  
 
 
FLAP
Veteran
Location: Michigan

yes, been there a couple of times. When Chris and Larry have one ready, I'll take a look. I've never actually seen either other than in video on the net. Trying to hook up with another AP Joker driver to see one in the flesh.
05-09-2008 01:18 AM
 
 
wlfk
Veteran
Location: uk

Quote 
Most people leave out the dead weight of the batteries that you are always carrying around.

That would still be included in the "well to wheels" figures, which are several times better for electric vehicles compared to similar petrol-powered ones.

Quote 
They also leave out the energy that the battery looses just sitting dormant when the car is not in use.

Not really an issue if the car is being used at all regularly. Won't be an issue at all with A123 packs, which were originally developed for evs.

Quote 
And finally the energy to make the battery and recycle the spent batteries.

Energy to make the batteries will be substantial. Energy to recycle... less so.

Quote 
No matter how you slice it efficiency is paramount when considering electric power and with liquid fuel it isn't even considered.

Probably should be, all the same...

Anyway, sorry for getting OT.

K

A bit like a kite, but 500 times more expensive
05-09-2008 03:33 AM
 
 
Autoeject
Key Veteran
Location: Ashtabula, OH, USA

Call Chris and make an appointment. He's been flying the snot out of his all the time. The one he's pictured on the site has been to many funflies for demo flights. From what I heard, he flies it more than his other helis.

It's available now on their site.

Mark Webber
webberaerialimaging.com
Spartan RC Distributor
Outrage Helicopters
05-09-2008 11:12 AM
HOMEPAGE  
 
 
1 page397 viewsPOST REPLY
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Aerial Photography and Video > opinions on extending blades to 800mm for electrics
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