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Old Aug 08, 2014, 11:23 AM
chuck
santa barbara, CA
Joined May 2009
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Quote:
Originally Posted by Grouser View Post
Okay, I'm about to pull the trigger on this puppy. I just want to be sure I'm aiming for the right thing.....

Today I am receiving an L-39 Skyangel airframe and I am much more interested in thrust than speed. (Much rather do a vertical 8 than a 90MPH pass though likely neither is possible.) Using on hand very good 1600mAh 30C 3s batts with a 30A YEP ESC.

So, which vendor delivers most quickly to the US and which variation should I order. I'm thinking blue from one of the eBay guys.

Many thanks for your time and advise.

Grouser
u should post in the skyangel thread and get some more opinions but imo 1600 is to much battery for the lower power 4300 version .......... i like a 1000 -1200 .

the hi kv ~5000 is all but useless imo way to many amps for batteries u can haul around ...yrmv.
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Old Sep 29, 2014, 07:00 PM
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limodune's Avatar
Australia, QLD, Toowoomba
Joined Oct 2011
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Here is a video of my just completed Windrider A380 1800mm wingspan with 4 x CS 50mm edf and 4200kv motors, runs on 2 x 3000mah 4s batteries, throttle has been pulled back to 75% around 30amps max

Mike

Windrider a380 second flight after maiden (3 min 53 sec)
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Old Sep 30, 2014, 09:18 PM
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Canada
Joined Nov 2000
7,063 Posts
Flys nice.
Not overly speedy. But being an Airbus model is that really an issue?
IMO the cs 11 is a lowish perf rotor which is Fine.. unless one was pretending it was Hi perf.
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Old Sep 30, 2014, 09:54 PM
chuck
santa barbara, CA
Joined May 2009
4,182 Posts
looks good mike .............. u may have already figured it out but imo the 4200 kv is just about right on 3 cells . have u considered a 3's flight? maybe u could save a bit of weight on batteries and still get similar performance ? they pull about 30 amps on 3's at that kv typically. that may be what u did by backing down to 75%?? meaning limited the throttle electronically?

chuck.
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Old Oct 03, 2014, 04:34 AM
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When I carried out taxi test's with this I was quiet surprised how much power/thrust the 4 x 50mm edf's produced, never used the 50mm size before only the 70 mm 10 and 12 blade, the plane seems to have a bit more zip than my other airliners during during roll out for take off, that's when I thought I could pull the throttle back on the TX to 75% , save some battery, and keep the temp's down, I don't have any 3s batteries suitable for this but plenty of 4s available so that's what I went with

Mike
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Old Oct 03, 2014, 10:11 AM
chuck
santa barbara, CA
Joined May 2009
4,182 Posts
very good. imo over 75% wont get u much more thrust anyway . at that kv really all it does is makes heat as the motors are to small for the input current they draw at wide open. as u noted this type of fan excels in nacelles......what is your exit diameter? i currently have a small f22 that i moved the c/s fan on to run a inlet ring and a short thrust tube in free air , it made a big difference in performance but i am thinking a bit smaller exit may be good . i used the tube from a 6blade 50mm fan that is 48mm exit and the thrust is good but at more than 100% fsa there may be some more o/a performance to be had smaller. the airframe is quite draggy so i wont expect much.
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Old Oct 03, 2014, 06:07 PM
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The exhaust is 50mm, I discovered with my 70mm 10-12 blade units that after swapping to a different nacelle with a bigger exhaust I was getting more amps/wts, what exhaust works with the low count blade edf does not work with the high count blade edf

Mike
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Old Oct 03, 2014, 10:54 PM
chuck
santa barbara, CA
Joined May 2009
4,182 Posts
Quote:
Originally Posted by limodune View Post
The exhaust is 50mm, I discovered with my 70mm 10-12 blade units that after swapping to a different nacelle with a bigger exhaust I was getting more amps/wts, what exhaust works with the low count blade edf does not work with the high count blade edf

Mike
except the wemo evo............otherwise agreed, 42mm works well w/ this fan on fast ,sleek airframes and somewhat bigger maybe better for more static thrust / draggy airframes but 50mm seems really big to get much eflux speed. going over 100%fsa may be counter productive ?
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Old Oct 09, 2014, 12:07 PM
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Having an exhaust diam > 100%FSA physicaly reduce the exhaust air speed compared to the speed at the rotor level, this is Bernouilli law.

P is pressure, V is speed, V1<V2 and P1>P2
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Old Oct 09, 2014, 01:21 PM
chuck
santa barbara, CA
Joined May 2009
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Originally Posted by stef France View Post
Having an exhaust diam > 100%FSA physicaly reduce the exhaust air speed compared to the speed at the rotor level, this is Bernouilli law.

P is pressure, V is speed, V1<V2 and P1>P2
agreed, but >100% may increase static thrust which may be useful on a large or high drag airframe.
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Old Oct 09, 2014, 08:54 PM
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Sooo? use a longer take off run OR a Bungee in absence of lots of static thrust.
Problem eliminated :-).
Efflux speed is IMO far more useful than roll down the runway power.
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Old Oct 09, 2014, 09:04 PM
chuck
santa barbara, CA
Joined May 2009
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Quote:
Originally Posted by Bare View Post
Sooo? use a longer take off run OR a Bungee in absence of lots of static thrust.
Problem eliminated :-).
Efflux speed is IMO far more useful than roll down the runway power.
no a longer runway does not fix high drag . u must over come drag w/ thrust not eflux. this was aimed at the poster w/ a airliner not a 100mph sleek airframe . in most cases 90-100% fsa is fine , maybe not in his case.
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Old Oct 10, 2014, 01:16 AM
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Australia, QLD, Toowoomba
Joined Oct 2011
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Quote:
Originally Posted by Bare View Post
Sooo? use a longer take off run OR a Bungee in absence of lots of static thrust.
Problem eliminated :-).
Efflux speed is IMO far more useful than roll down the runway power.
The end of the strip has a fence there--no-no using all the strip
Can you show me how to bungee launch an 1800mm wing span airliner
If I cannot get this off a grass strip what is the point of it 'maybe' flying at 100MPH
Thrust is more important to get it off the grass- top speed comes second

Mike
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