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Old Dec 16, 2012, 12:43 AM
This thing runs real nice...
Nam Lemmi's Avatar
Joined Jun 2012
285 Posts
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Originally Posted by turboparker View Post
However - running your packs to LVC will kill them in a very short time.
Yes that is exactly what I was trying to do. I am aware of 80% rule.

Why? I have decided not to fly UMX anymore so I thought I would push the packs to their limit to see just how far they can go before I dispose of them.

Sadly the MA's did not do as well as I expected.
Hyperions great as always.
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Old Dec 16, 2012, 12:58 AM
Have fun
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Joined May 2007
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I would say that the reason the ma didnt last long wzs becuase of their higher c and higher c per mah ratio(a 25c pack thats 300mah has a higher c-per-mah than a 25c 200 for example). Becuase of this the mig is able to discharge the MA much faster than the hyp, resulting in a rather equal run time, but the MA would have output more power in that runtime than the hyperion did. Does any of this make sense?
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Old Dec 16, 2012, 02:30 AM
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Originally Posted by toys2cars2toys View Post
Are there any "needed" mods? So far I've picked up on tidying wires in the ducts and maybe servo covers
Well yes there are. If you do not plan to land on the wheels you should definitely get/make some nose caps. They will prevent your nose from fragmenting into bits (had at least 10 crashes and the nose is still in one piece) and they're useful to not scratch the paint or get dirt onto it.
It's easy to do, and it's best to do it before you crash. All you need is alginate to make a mold, some plaster to fill it and 85 to 90mm shrink tube.
If the grass o your field is rough, you should also add a strip of tape on the wings for the same reason.
Also, strengthening the elevator/tail wings (or whatever they're called) with either some clear plastic or carbon rod or strip, depending on what you have close by.

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Originally Posted by toys2cars2toys View Post
If you switch in a reversed/mix aileron, it may drive the AS3X nuts ,the aileron servo left connected to the AS3X would be unpredictable as it tried to correct roll
Yes, but I won't use it mid air, landings only.

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Originally Posted by toys2cars2toys View Post
Other ideas
A servo operated arrester hook!
Hmm... Well this could be easier to do than the original mig airbrakes, but finding a mechanism that won't rip the fuselage would be wuite difficult and then again I'd properly have to land near a stretched wire or something. Interesting though

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Originally Posted by toys2cars2toys View Post
I've been on RCG long enough to read between the lines, when you see so many good guys giving the same advice, you really should take note, but then again, we all love to mod!
Yup, I'm trying to improve my landings, as the guys said and snow is especially good to do so.

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Originally Posted by toys2cars2toys View Post
Google "PICAXE" chips, they are little programmable IC's
Now this is a really good one! The best so far is the pers switch (still didn't get an answer if it can transmit signal) and an electromagnetic relay. I'm a but reluctant about the relay as it's still a mechanical switch and tiny ones are just so hard to find!
So, how do I program this chip? Will any of the starter packs do?
Then again I have no clue on how to program this thing, so I'll need a lot of guidance, best to continue in this thread.
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Old Dec 16, 2012, 06:25 AM
Just flew it
Cumbria, UK
Joined Feb 2005
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Thanks for all of your tips guys, I like the idea of the plastic "bra", I wonder if the idea of shrinking a drinks bottle onto a mould would work


Vad
I've added a post in your thread, not much to add though
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Old Dec 16, 2012, 10:02 AM
Gopher huntin' stick jockey
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East Bethel, MN USA
Joined Jul 2009
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Originally Posted by airpower View Post
I would say that the reason the ma didnt last long wzs becuase of their higher c and higher c per mah ratio(a 25c pack thats 300mah has a higher c-per-mah than a 25c 200 for example). Becuase of this the mig is able to discharge the MA much faster than the hyp, resulting in a rather equal run time, but the MA would have output more power in that runtime than the hyperion did. Does any of this make sense?
AP,

Yes. It's all about the pack's internal resistance. Higher C packs have lower internal resistance than lower C packs. Higher capacity packs also have lower internal resistance than lower capacity packs. Therefore, a higher capacity, higher C pack will have an even lower resistance. (Of course - we're talking true capacities & C-ratings here, not the advertized numbers.) As the resistance of the source decreases, voltage at the load increases. Therefore, energy delivered to the load must also increase at given throttle setting. Given that wattage increases at the square of the voltage, a small increase in loaded voltage corresponds to significant increase in available power.

Given that the TP 325 65c pack provides a noticeable increase in performance over the MA 300 30c, and given that the MA 300 30c provides a noticeable increase in performance over the the Hyp 240 25c, we know that the MiG pulls significantly more current with lower resistance packs. Hence, flight-times will be shorter when no throttle-management is used. However, if one uses throttle-management, flight-times will actually increase. Higher voltage under load means that less current is required for a given maneuver, so those who practice strict throttle-management typically see longer flights at higher voltages. For example - my Sbach 3D flies longer on a Hyp 180 3s pack to the 80% discharge point than it does on a Hyp 180 2s pack because I only use a fraction of throttle during a typical flight than I do on 2s.

Of course, we're talking a UM EDF, so "throttle-management" pretty much consists of firewalling it until it's time to slow her down for the approach!

Joel
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Old Dec 16, 2012, 11:49 AM
The Luftwaffle
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United States, FL, DeLand
Joined Sep 2012
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Originally Posted by turboparker View Post

Of course, we're talking a UM EDF, so "throttle-management" pretty much consists of firewalling it until it's time to slow her down for the approach!

Joel
Haha. With mine, I like to make some "low and slow" passes about 2 feet away from my person and then do a circle with my person as the center point. Then I come it screaming and slingshot around right in front of me. Too much fun.

one of the two times I ever crashed the mig was when I had to duck because I gog to close to myself.
The other time was when low airspeed and a violent crosswind, and motor torque actuly got the thing to tipstall. At least it landed in the grass.
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Old Dec 16, 2012, 11:57 AM
Way to many airplanes!
Canada, QC
Joined Oct 2009
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Quote:
Originally Posted by Nam Lemmi View Post
Did some engine runs at home last night with Hyperion 240/25c and Mini Aviation 300/30c packs.

Tested x2 MA packs and x3 Hyp packs. Set full throttle and ALL packs seemed to hit LVC at almost spot on 4:00 minute mark.

Was very surprised and disappointed that the MA packs with a supposedly higher capacity and a higher c rating did not out last the smaller Hyperions.

Anybody have similar results?
How cold was it when you flew? Hyperions are great in the cold. I had mixed results with some 1S MA batteries in the cold (never bought 2S MA, so cannot say anything about those).
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Old Dec 16, 2012, 02:15 PM
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United States, TN, Jackson
Joined Mar 2007
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Some things to remember for extended battery life---On downward lines reduce the throttle to 1/4-idle...For example: At the top of a loop I'm back to 1/2 throttle and once the model starts to arc over I reduce the throttle to about idle...With practice you can make your loops not only the roundest but keeping the same speed throught the loop...(Nothing looks more like an underpowered toy than to pull through a loop, loose a ton of airspeed, and then zoom down at full throttle with a quick yank upward for an egg-shaped loop!!!)...Altitude at the exit is always the same as the entry for the best looking loops....

I like to swap out inertia for throttle...In a split "S" I will back off of the throttle to idle (NEVER to OFF as this causes drag within the duct with a stopped or freewheeling rotor) on the downline and nail the throttle when just about level...The plane maintains about the same speed for a smoother looking flight...With all of that speed you gained for free on the downline and then full throttle when level you can do larger loops using LESS throttle...It's all about inertia and throttle management...I know that it can be hard to use the inertia from a 2.5 ounce model but it can be done!!!

Years ago (about 20) when nitro powered ducted fans ruled I saw BVM rep Garland Hamilton routinely make 15+ minute flights with a Maverick Pro when all of the rest of us were getting 9-10 minutes at best...BV himself once scolded him for flying so long as he didn't want to see Garland ding one of his planes...But Garland was a MASTER at using throttle management, swapping out inertia for throttle, and only using enough throttle to get the manuever accomplished...Even with 15+ minute flights Garland ALWAYS landed with enough fuel for a go around or two!!!

Kevin
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Old Dec 16, 2012, 05:37 PM
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United Kingdom, Yeadon
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Originally Posted by Kevin Greene View Post
I like to swap out inertia for throttle...In a split "S" I will back off of the throttle to idle (NEVER to OFF as this causes drag within the duct with a stopped or freewheeling rotor) on the downline and nail the throttle when just about level...
What is the difference between idle and off with an electric motor? 10% power or less?
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Old Dec 16, 2012, 06:02 PM
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United States, MI, Grand Traverse
Joined Oct 2008
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Originally Posted by SilentPilot View Post
What is the difference between idle and off with an electric motor? 10% power or less?
I think in this context idle means throttle just on enough for the motor to be running and not free spinning.

-Brian
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Old Dec 16, 2012, 11:43 PM
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Originally Posted by kalmon View Post
I think in this context idle means throttle just on enough for the motor to be running and not free spinning.

-Brian
You nailed it---If the throttle is off then the rotor will either stop or freewheel...This causes drag to slow the plane down...

You've gotta remember that a jet has TWO forms of drag---The exterior of the plane and the interior ducting with motor/rotor...On a downline, don't go to the OFF position on the throttle---Carry some "idle thrust" with you on the downline...You will keep the speed up for VERY little cost in battery power as the rotor will be spinning with a little power, causing less drag...

Kevin
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Old Dec 17, 2012, 12:11 AM
Gopher huntin' stick jockey
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East Bethel, MN USA
Joined Jul 2009
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With conventional props, even a prop at a low power setting for the flight-speed will have considerably more drag than a stationary prop. If that's also true with EDF rotors, one could enable the prop brake on the brick to make sure that the rotor contributes the least amount of drag as possible when the power is pulled back on down-lines.

Joel
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Old Dec 17, 2012, 07:31 AM
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United States, MI, Grand Traverse
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Originally Posted by turboparker View Post
With conventional props, even a prop at a low power setting for the flight-speed will have considerably more drag than a stationary prop. If that's also true with EDF rotors, one could enable the prop brake on the brick to make sure that the rotor contributes the least amount of drag as possible when the power is pulled back on down-lines.

Joel
I thought about this as well but how well do inrunners brake? I know there is some significant torque differences from the outrunners that most electric conventional prop planes use.

On my down-lines I usually use about 1/3 to 1/2 throttle increasing throttle as I roll out to level flight.

-Brian
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Old Dec 17, 2012, 08:29 AM
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Kingston, Canada
Joined Jun 2004
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With the amount of blade area covered by the the rotor blades compared to a prop, I think the stopped blades are going to do a good job of blocking the airflow through the jet. Although I just back off on the throttle on the downside through habit. Just my take on it.

Gord.
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Old Dec 17, 2012, 09:32 AM
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United States, MI, Grand Traverse
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Originally Posted by flypaper 2 View Post
With the amount of blade area covered by the the rotor blades compared to a prop, I think the stopped blades are going to do a good job of blocking the airflow through the jet. Although I just back off on the throttle on the downside through habit. Just my take on it.

Gord.
OK, Time to dig a little deeper into the windmilling vs stopped prop. Most data comes from full scale planes, either Piston or Turboprop. in both cases a non feathered windmilling prop creates a bunch of drag. Why? there are a couple forms of drag here skin friction; the air moving over the prop blade, and more importantly the energy absorbed by the engine. This is the main factor. The oncoming air is using energy to turn the prop which in turn is moving the pistons compressing the air in the cylinders and moving all the engine parts. This requires a lot of work, don't believe me grab any of your I.C. RC engines and turn the prop over by hand, Now multiply that as the engine gets bigger. A stopped prop only has to deal with the frontal area of the individual blades. The drag on a windmilling prop is effectively the entire prop disc area!

Now here is my problem: On these small electric motors they spin extremely freely there very little drive-train drag unless it is a geared system. So the largest form of drag in a windmilling prop in full scale is gone as there is no engine to turn. Granted yes there is motor mass that has to rotate but it is so little at this scale I wonder how much difference there really is.

Bottom line even in this small scale a free spinning prop/blade will have more drag than a stopped one. But maybe not much more? Maybe some aeronautical engineer here can chime in and help.

-Brian
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