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Old Jan 24, 2013, 04:51 PM
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United Arab Emirates, Ajmān, Ajman
Joined Jan 2010
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Question
Finalizing my Blu-Baby Trainer, Is it a good setup

At last my Blu-Baby is about to complete, I'm looking for a basic trainer and slow flying with short takeoff distance since this will be my first plane in the RC world and I'm learning to fly by my own.

I already have some RC items on hand and would like to make sure I selected the suitable setup for the plane:

Plane Info:
- Blu-Baby 42" KFM3 2" dihedral wing (http://www.rcgroups.com/forums/showa...mentid=1864880)
- Wing Area : 24.5 dm2 (Is this correct?)
- AUW (Estimated) : 500gm

My Setup:
Motor: Turnigy D2836/9 950KV Brushless Outrunner
Prop: 8x6 SF (I used WebOCalc : Thrust 500gm, Max Speed 64.9 km/h)
ESC: Hobbyking SS Series 15-18A ESC (I have also HK Blue Series 40A)
Battery: Zippy Compact 850mah, 35C.


Is this OK for my goal?
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Old Jan 24, 2013, 05:54 PM
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Orleans, MA
Joined Feb 2007
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I would say your motor is much too heavy and powerful for this model. Something weighing about 30-40 grams and rated 1000-1300Kv would be more appropriate for the slow flying you want to do and would be a better match for your 800mAh battery, 18-amp ESC, and 8x6 SF prop while still providing more than enough power. Even a Blue Wonder would probably work well on this plane. I'd check the build threads and see what others have used.

It looks like a nice build! Good luck with the setup and your future flights.
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Old Jan 24, 2013, 06:20 PM
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Livermore, CA
Joined Sep 2004
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What does the plane airframe weigh, inc the servos but minus the motor/esc/batt??
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Old Jan 25, 2013, 02:07 AM
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United Arab Emirates, Ajmān, Ajman
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Quote:
Originally Posted by whitecrest View Post
I would say your motor is much too heavy and powerful for this model. Something weighing about 30-40 grams and rated 1000-1300Kv would be more appropriate for the slow flying you want to do and would be a better match for your 800mAh battery, 18-amp ESC, and 8x6 SF prop while still providing more than enough power. Even a Blue Wonder would probably work well on this plane. I'd check the build threads and see what others have used.

It looks like a nice build! Good luck with the setup and your future flights.
I got your point, I will make a trip to local stores here and check for smaller motor. Something like this one I guess http://www.ultimate-hobby.com/eflite...0kv-p-570.html.

Thanks for the detailed advice
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Old Jan 25, 2013, 02:08 AM
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Originally Posted by Butch777 View Post
What does the plane airframe weigh, inc the servos but minus the motor/esc/batt??
305 gms (10.76 oz)
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Old Jan 25, 2013, 08:31 AM
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Orleans, MA
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Quote:
Originally Posted by Andalosy
I got your point, I will make a trip to local stores here and check for smaller motor. Something like this one I guess http://www.ultimate-hobby.com/eflite...0kv-p-570.html.
Yes, that should be about right. Many similar motors can be found online from many sources. Using that motor and your other components, AUW should be close to your estimate.
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Old Jan 25, 2013, 12:40 PM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
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New motor, no data. I'd take a pass. I don't buy any motors that don't appear in Drive Calculator's database. Web-o-calc is junk, relies on you plugging in the lies found on the seller specifications for the motor. Those are almost always wrong and double wrong for being Hobby King.

With the cheap motors the task is to figure out what the real performance specs are and forget about the fiction on the seller's web page. When the motor is in the Drive Calculator database, that means that real test data is available and predictions provided by the program will be useful.

Web-o-calc predictions on a motor without a track record, or any other motor for that reason, are completely useless. It assumes that all props, speed controls and motors are the same. It then tries to plug all these fallacies into an equally fallacious formula to give you a mathematical model of that motor's performance. It lies.

Unless a program uses motor, speed control, battery and propeller by brand name and model number, you KNOW that the results are garbage. Drive Calculator is free and accurate with submitters of test data such as Dr Kiwi, of RC Groups renown, who submit test data good enough so you can spend your cash knowing your components will work together well.

Why would you want to use anything else?

Here's the deal with a closely related Turnigy motor at 1000kv. Stand by for correction. Okay, let's try THIS. (it's so easy to get one little detail wrong) (crap! now the prop's wrong!)(fixed!)



Your 800mAh 35C battery is good for 28A of draw. At 11.1 volts you would be just above that. This would shorten the life of your batteries. I'd recommend going to a smaller motor and one that has exact test data either in Drive Calculator, or if you insist on paying money, MotoCalc.

If you stay with this motor, you'll have a prop spinning above maximum rated RPM, a battery overdraw situation when at full charge and weight you don't need in the airframe. You could solve the battery problem with a 1300mAh pack but that just adds more weight. You could switch to an APC E prop to have higher RPM tolerance with safety. Slinging a prop blade is instant death for your model and it's a deadly projectile. Don't chance it.
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Last edited by Rockin Robbins; Jan 25, 2013 at 01:37 PM.
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Old Jan 25, 2013, 01:03 PM
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Orleans, MA
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I think your confusing WeboCalc with another program. WeboCalc only requests general motor parameters (type, Kv, overall efficiency) to calculate power required to fly a specified airframe in the desired manner.

I like DriveCalc too for estimating motor, battery, prop and ESC performance.
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Old Jan 25, 2013, 01:32 PM
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Livermore, CA
Joined Sep 2004
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I run several BlueWonders on planes this size, the 24g 1300kv, 8x6 prop and 3 cell lipo.
I get around 14ozs of thrust.
My planes weigh 10.5ozs to just over 14ozs, and up to a 55" wing.

At about 11ozs for your airframe, you be better of with a bit larger motor than 24g's.
Although, if you didn't need a lot of flight time and used a smaller battery, it would fly ok with a 24g motor.
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Old Jan 25, 2013, 09:39 PM
buyer of the farm
United States, FL, DeLand
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Blue Wonders give you an unholy whistle, which you either love or hate! I can't wait to hear one.
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Old Jan 26, 2013, 12:15 AM
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Livermore, CA
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Quote:
Originally Posted by Rockin Robbins View Post
Blue Wonders give you an unholy whistle, which you either love or hate! I can't wait to hear one.
I've currently have about 30 planes, and have sold another 20-30 planes with the BlueWonder, 1300Kv, 1500Kv and 1700Kv and never really noticed any real type of whistle.
Maybe it was the 3000Kv BlueWonder.
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Old Jan 26, 2013, 02:30 AM
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United Arab Emirates, Ajmān, Ajman
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This is not easy as I thought

I just finished the whole air frame without the landing gear yet. The finished weight now is 334 gms.

Then I checked DriveCalc and found one of the available motor here (eflite park 370 1370kv), I selected the closest battery to mine. Within the parameters provided by DriveCalc the 6x4 APC E prop seems fine. the power system thrust is acceptable 384 gms which is more than 75% of the AUW = 490 estimated with landing gear). However I'm not sure about my selection because of the pitch speed (82 km/h!)

So is it suitable power system for a trainer? (eflite Park 370 + 6x4 APC E)
http://www.e-fliterc.com/Products/De...rodID=EFLM1205

Or should I go for a smaller motor? (25 gms)
http://www.e-fliterc.com/Products/De...rodID=EFLM1150
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Old Jan 26, 2013, 07:03 AM
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Orleans, MA
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I think that would be fine. For greater efficiency and reduced pitch speed, you should also be able to run a 7x3 or 7x4 without overdrawing. The heavier Park 370 will give you more reserve power.
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Old Jan 26, 2013, 10:25 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
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Well! That looks like one of a million great combinations. One good thing about having reserve speed (82 km/hr is only 50 mph) is that you have a throttle and using it will extend your flight times.

One thing all of us learn is that too much is just right. You can never have too much power as long as that doesn't give you too much weight. This system is light enough for your plane and plenty powerful. Proceed without too much fear! Don't panic! Proceed with caution: FULL SPEED AHEAD! There I go with the all caps. C4H10 is gonna whack me again.
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Old Jan 26, 2013, 12:22 PM
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United Arab Emirates, Ajmān, Ajman
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Originally Posted by whitecrest View Post
I think that would be fine. For greater efficiency and reduced pitch speed, you should also be able to run a 7x3 or 7x4 without overdrawing. The heavier Park 370 will give you more reserve power.
Very good advice ... I checked the DriveCalc with those props too (Why I didnt in the first place?!!! ) and they gave good thrust and lower in the max pitch speed too!

I shall buy those props with the motor and gave them a test
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