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Green Models 50" Tiger Moth Conversion

Old 09-15-2006, 09:41 AM
  #51  
Geoff_Gino
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Tim

Thanks for that link. E-mailed Alex and had a reply within the hour with a promise that he will look into my problem and check with the factory floor.

Sounds very sincere.
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Old 09-18-2006, 09:42 AM
  #52  
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Hi All

Alex from Green Model requested some pics of my problem wing which I have sent.

Mike and Piperfan have you guys been able to look at your top to bottom wing alignment? If so please let me know what your thoughts are.

Last edited by Geoff_Gino; 01-31-2008 at 12:33 PM.
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Old 10-06-2006, 04:39 AM
  #53  
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Exclamation 50" Tiger Moths available Australia

Just a quick follow on from an earlier post I made, the first shipment of e-Tiger Moths from Green RC Models has landed, and were all sold before arrival. The electric versions have a brushless motor mount and battery tray as per the Hoby Lobby kit.

I will be ordering another shipment based on orders, so if anyone in Australia or New Zealand would like one, please contact me so you can reserve your colour scheme. The sell for A$240.

I also bought in the Tiny Tiger Moth and Butterfly kits. The build quality of these kits is equally as impressive!

I really am enjoying this thread - any updates or flight reports anyone?
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Old 10-06-2006, 07:31 AM
  #54  
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Hi Tim

I would really be interested in seeing how the top and bottom wings line up with your new shipment.

Been speaking to Green R/C and they have admitted that my top wing is out of alignment but have not done anything about it.

Last edited by Geoff_Gino; 01-31-2008 at 12:33 PM.
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Old 10-07-2006, 04:49 AM
  #55  
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Geoff
That is incredibly bad. A quarter inch - maybe - that much mis-alignment is just bad. Bad design, bad parts engineering, bad construction jig - you name it, I cannot believe how bad it is.

Any company with any pride would have a new set of wings to you - wings that are properly built - scrap that offending jig and track down all other buyers to replace their wings / models and make good their losses.

From that end of the world?

Fat chance.

Would like to be proven wrong...

Dereck
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Old 10-07-2006, 05:34 AM
  #56  
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Default Wing alignment

Hi Geoff,

I checked the wings last night - 1 wing set has a bit more sweep back than the other, but they are symmetrical and parallel. I guess that is good for me (& my customer), but it doesn't make you feel much better.
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Old 10-09-2006, 10:42 AM
  #57  
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Hi Tim

Guess you can say that I am relieved for you and your customers and that the problem was only a 1 off.
Your'e right about the sweep - the top wing does have more than the bottom, but in equal amounts.

Hi Mike

Green R/C seem to have given up on me. From appearing to be quite friendly and helpful it has gone to 'dead silent'.

Think I'll post them a link to this thread and see what comes up.
Thanks
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Old 10-10-2006, 04:13 AM
  #58  
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Originally Posted by Geoff_Gino View Post

Green R/C seem to have given up on me. From appearing to be quite friendly and helpful it has gone to 'dead silent'.

Think I'll post them a link to this thread and see what comes up.
Thanks
Geoff,

I have already done so on your behalf (hoping I can add some 'momentum')
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Old 10-10-2006, 07:25 AM
  #59  
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Thanks Tim

No answer yet I'll give them another 'wake up' today.
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Old 10-10-2006, 09:11 AM
  #60  
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Seems like they have their holiday period at this time. Alex has responded saying that that they are back and I should get a reply shortly.
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Old 10-19-2006, 12:58 AM
  #61  
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Need advice... I just finished the HL version with the following motor and speed controller.

E-Flite Power 25 outrunner
11x5.5 APC prop,
E-Flite 40A ESC

The plane barely has any power for take off and flying. Good thing it was a calm evening... Also my Apogee 2100mah battery pack was very hot at the end of the flight. Also I get the feeling the CG is too nose heavy because I had to use almost full elevator to get off the ground after an excessively long roll out. I tried slow flight at altitutude and found at reduced power I could fly at full elevator and the plane would just sink. Any suggestions on the motor set up?

Otherwise its a beauty in the air.

thanks in advance.
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Old 10-19-2006, 02:23 AM
  #62  
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Hi Ram500,

I think you have 2 issues - I will address them seperately.

Battery

The fact that you LiPo is so hot suggests that it is operating close to it's current limit. A couple of questions.....
  • Do you know what current your setup is pulling?
  • What current is your pack rated at?
  • Are you using a 3S or 4S pack?
Running 2 packs in parallel would reduce the load on each pack significantly, and also improve performance noticeably (as well as run time). Twmaster (post #1) is running a 3S2P 3400mAh pack in his.

Propellor

The 11x5.5 prop recommended by Hobby Lobby works fine with the Axi 2820/10 motor, as it is a 1200kV motor. The Power 25 motor is only rated at 870kV, so this motor will not spin the 11x5.5 prop fast enough to be effective. The recommended prop range for the Power 25 is 11x8 to 14x7. Twmaster is using an 11x8 prop on his Tiggie, so that would be an excellent place to start.

If you address these 2 items, you should have plenty of Tiger in your Moth!!

Hope this helps.
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Old 10-19-2006, 03:27 AM
  #63  
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Dimadee,

Thanks for the quick reply, I will admit that I'm not fully equipped for electric flight. If I'm going to stick with electrics than I'll need to get a watt meter or something. I don't know what kind of current I'm drawing. I'm using 3sp and the Apogee is rated at 10.5C (22.8A) continuous. I do have another pack that I could hook up in parallel.

Not sure I understand the prop though. The 11 x 5.5 has less pitch than a 11 x 8, shouln'd the 11 x 5.5 spin faster?

Thanks again, I'm still learning electrics....

Power planes I have no problem, been flying over 20 years, go figure!

Gus
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Old 10-19-2006, 04:26 AM
  #64  
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Hi Gus,

The set up you have would be pulling more than 22A I expect (I wish I had my copy of MotoCalc at work!). If your other pack is exactly the same spec (i.e. Apogee 2100mAh 10.5C) then it will be fine to hook up in parallel. If they are different packs, please don't hook them up together. I generally ony run to 75% of the maximum constant capacity of a LiPo pack to ensure longevity and performance. For your pack, that would be 17 amps (double that if you have 2 packs in parallel).

To make your plane fly it needs a combination of thrust and pitch speed. The Power 25 spins substantially slower then the Axi motor (870 rpm per volt vs 1200 rpm per volt), so it is developing less thrust, but more importantly, at a much lower rpm. Combine this with a low pitch prop, and the pitch speed is very low.

Heaps of thrust with no speed is perfect for 3D planes that want to hover, and heaps of pitch speed with less thrust is great for high speed racers, but in this case you need a balance of both. As a general rule, the pitch speed needs to be 2.5 to 3 times the stall speed of the aircraft.

A Watt Meter would be an excellent investment if you plan to stick with electrics.
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Old 10-19-2006, 04:37 AM
  #65  
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Tim, thanks a bunch, makes sense...

Tomorrow I'll be looking into a watt meter... So far I've been flying a E-flite mini funtana with stock set up (no hassle, fly's great), Hobby Lobby F-86 Sable with stock set up (no hassle, fly's awesome - not a bullet but plenty of fun), my "need for speed" days are long behind me....

I love scale modeling, the HL Tiger is such a beautifull done example of a Tiger Moth. Especially the functional rigging and controls. The plane, even on the smaller scale at 50", presents well in the air. Looking forward to dialing everything in and getting a lot of enjoyment out of it.

I guess this is how I'll learn more about electrics, deviate from the recommended set up.

Gus
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Old 10-19-2006, 09:51 AM
  #66  
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Hi Gus,

I plugged some numbers into MotoCalc tonight and have attached the results in the zipped (html) file. I have assumed you have 3S packs, and have used 20C LiPo cells for the calculation.

The first column is the Hobby Lobby power system to use as a baseline. The next 2 columns show the Power 25 running a single 11x5.5 and 11x7, and as you can see it would be pushing your batteries beyond their practical limit, hence the toasty warm feeling. You can also see why your Tiger was struggling to fly with the 11x5.5 when you look at the rate of climb number, and it confirms that the 11x7 would be much better.

The next 4 columns show what happens with 2 packs in parallel - the voltage, current and power all increase, and the load on each pack is much less (it will be 1/2 of the total current). You can now see that the 11x7 does a pretty good job, and the 11x8 and 11x8.5 will give you a bit more for a few extra amps. I would expect that with the 11x8 and 11x8.5 props you would be mooching around quite happily on 65-75% throttle.

Obviously this is only a prediction, and real world testing will help you find the result that suits you. You also have the option to go to 4S with this motor if you wanted more in the future!
Attached Files
File Type: zip
HL Tiger Moth.zip (2.2 KB, 282 views)

Last edited by dimadee; 10-19-2006 at 11:41 AM.
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Old 10-19-2006, 03:27 PM
  #67  
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Thanks Tim,

This really gives me something to work with..... Appreciate all your help

Gus
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Old 10-19-2006, 11:57 PM
  #68  
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Gus,

Please let us know how it goes.
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Old 10-20-2006, 01:04 AM
  #69  
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Well, tonight on the way home I picked up the Astro flight Super Whatt meter, 2 x 2100 Thunder power 3sp packs and an 11 x 8 apc prop. I will measure actual performance with the original set up as a basis for my comparison.

My only concern now is that I noticed the TP packs are rated at 15C continuous. Not sure if I should take them back before I open them....
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Old 10-20-2006, 01:18 AM
  #70  
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Hi Gus,

The 15C rating equates to 2.1A x 15 = 31.5A continuous (2100mA = 2.1A).

Apply a safety factor.......75% x 31.5A = 23.6A.

If you then double this for the 2 packs in parallel, that gives you 47 amps continuous.

You're laughing!!

(Sorry if I sound like your Maths teacher!)
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Old 10-20-2006, 01:48 AM
  #71  
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I think I just figured the same thing out..... your 20C example just threw me off a bit. Lessons in electric flight!

Once the kids are in bed and the Mets are playing, I'll be soldering away.....

this might be a ligitimate stupid question... with a Y harness, can I charge both packs in parralel at the same time? I use a triton charger
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Old 10-20-2006, 02:31 AM
  #72  
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Gus,

Good question. Importantly, when you connect 2 packs in parallel, they need to be at a similar level of charge (e.g. both fully charged), as they will balance their voltages off against each other. In an extreme example, if one pack is flat and the other fully charged, the full pack will charge the flat pack until they are both at the same voltage, but with an unrestricted current flow, it would all get very warm and you would probably have a thermal incident

Once the packs are connected in parallel, they will effectively act as one, so you can charge them as a single pack at up to 1C, which would be 4.2A (2 x 2.1A) in this case. If you are making your own parallel connector, you need to make sure that the wire is heavy enough to flow the combined current of both packs.

Beofore connecting them however, I would strongly recommend charging and balancing each pack individually. Do you have a LiPo balancer? If you don't, you can balance them manually, but it will take a while.

To balance manually you will need a charge lead with a female servo connector on it. You slice off the plastic sheath to reveal the 2 pins, which just happen to be the same spacing as LiPo balancer plugs. You can then charge each LiPo cell individually. It is not as accurate as a balancer, but it is better than no balancing at all!

Last edited by dimadee; 10-20-2006 at 02:57 AM.
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Old 10-20-2006, 04:02 PM
  #73  
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Here are some actual figures from last night.

Common elements: Eflite 25 outrunner and 40am esc

(4 scenarios)

1.
Apogee 2,070 3sp 10.6C (single pack)
11x5.5 apc prop
20 amps
200 watts
7900 rpm (digital tach)

2.
Apogee 2,070 3sp 10.6C (single pack)
11x8 apc prop
22 amps
200 watts
7200 rpm

3.
Thunder Power 2,100 3sp 15C x 2 (parallel)
11x5.5 apc prop
26 amps
300 watts
8900 rpm

4.
Thunder Power 2,100 2sp 15C x 2 (parallel)
11x8 apc prop
33 amps
375 watts
8300 rpm

A big jump in amps between 3 and 4. I'll see what the difference will be in actuall flight this weekend.

Tim, thanks again for all your help. Let me know your thoughts on these figures.

Gus
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Old 10-21-2006, 02:52 AM
  #74  
dimadee
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Hi Gus,

Although the actual current values vary a bit, the relative difference is pretty well just as MotoCalc predicted. The single packs are being pushed past their practical limits, and as a result the voltage drops off and along with it the power.

The higher rated parallel Thunder Power packs are able to flow more current because they are not working very hard (16.5A each with 11x8 prop = 8C), so the rpm, voltage and power are much higher. This should give you a huge difference in flight performance! I love it when a plan comes together!!

Another thing I always do is to sand the leading edge of my props with some fine (800 or higher) wet&dry sandpaper. Prop blades are actually airfoils, and there is always a small feather of plastic left along the leading edge where the mould joins. If you sand this off so the leading edge feels smooth with your fingers, I find the prop will be quieter, and therefore more efficient.

I look forward to a flight report!

By the way Gus, where are you from?
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Old 10-21-2006, 06:42 AM
  #75  
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I'm from Pompton lakes, New Jersey. About 30 minutes west of New York City. Actually I just got home from there a few minutes ago. Beautiful cool night in the city...

I'll follow up with actual flight performance, hopefully this weekend.

Thanks again
Gus
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