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Graphite 2E from Vladimir's Models

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Old 09-06-2012, 01:14 PM
  #1
longsoar
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Default Graphite 2E from Vladimir's Models

Hi everybody!
Got myGraphite 2E crosstail made by Vladimir's Models in Ukraine.
It's an electric version of Graphite 2 glider.
The quality and craftsmanship is impeccable! Absolutely stunning!
Glider is 100% built and requires only equipment installation. So, considering the price of $1,000US delivered - in my book it's much cheaper than Art Hobby's Vortex ($400) as Vortex requires a lot of building to finish the glider.

Considering my lack of hi-end power experience I have a few questions regarding the power plant/prop/ESC etc.
I used a power calculatorwith the following variables:
Model weight: 2.5Kg
Battery: 4000mAh 3S
ESC: Max power 60A
Motor: Hacker A30-18M V2 with 6.7:1 gearbox
Prop: Aeronaut 17x11 no yoke twist

and it showed me Static thrust: 2,387 Kg
Prop stall thrust: 1,363 Kg

I know, motor is an outrunner, not the inrunner but considering it draws 1.9A idle current instead of 3+A on recommended inrunners I am gaining some flight time there while enough power is available according to calculator.
My questions are:
Motor's operating current is 50A and peak current is 70A. How do I choose ESC? By peak current or operating current?
What's the high-end dependable ESCs out there?
Do I use built-in BEC or should I opt to separate BEC? I have Aurora 9 radio with Optima 7 Rx that will let me use separate BEC unit.

I plan on using MKS DS65K for rudder and elevator,
KST DS135MG for ailerons and KST DS125 for flaps.

Also I am researching idea of placing Rx in the wing and run quick connector for tail servos and power connector instead of ailerons and flaps since wing is hollow and has plenty of space there.
I will post some pictures of the progress soon.
Thanks for all the help!
Mark.
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Old 09-06-2012, 04:50 PM
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Default RE: Graphite 2E from Vladimir's Models

just a couple of pics:
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Old 09-13-2012, 05:21 AM
  #3
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Default RE: Graphite 2E from Vladimir's Models

Just a few more pictures before servos and motor arrives.
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Old 09-13-2012, 11:56 PM
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Default RE: Graphite 2E from Vladimir's Models

Hi longsoar, I really love flying my Graphite and have just re-powered it with some Lipo batteries. The first outing with them turned out bad as the battery I had down the field dropped a cell so it was quite a short flight.
I have about 50 flights on mine with no incidence.
I'll get some specs for you.

Cheers,

Brad

Hmmm, just re-read your specs and you have the 2m. Sorry.
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Old 09-14-2012, 12:15 AM
  #5
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Default RE: Graphite 2E from Vladimir's Models

Hi Brad!
Big hello to Australia!
Nope, I have 3.1 meter version.
2 meter is Mini-Graphite and mine is Graphite 2E.
Thanks for the post. Your Graphite looks Hotttt!
Mark
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Old 09-14-2012, 01:10 AM
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Default RE: Graphite 2E from Vladimir's Models

Oh yes Mark I should have realised you didn't say "Mini".
Here is a thread of mine with a gear list and a couple of flight reports.

http://www.rcuniverse.com/forum/m_58...tm.htm#9093516

As you will see I am of no competition standard just an enthusiastic sport flyer.
Enjoy putting it together and flying some nice peaceful flights.

Ask any questions about the build if you like.

Cheers,

Brad
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Old 09-28-2012, 01:16 PM
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Default RE: Graphite 2E from Vladimir's Models

Just received 2 KST DS135MG and 2 KST DS125MG servos (total 4 servos) for US$99.48 delivered from Aloft Hobbies.
Servos are $24 each. Servos for flaps and ailerons.
Two MKS DS65K servos coming next week from Soaring USA ($126 delivered) for the rudder and elevator.
Also HackerB40-12S with 4.4:1 gearbox coming tomorrow.
All of the above will keep me busy installing hardware and I'll be posting images as they come.

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Old 09-29-2012, 06:22 PM
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Default RE: Graphite 2E from Vladimir's Models

Here's the pictures of MKS 65K servos and Hacker B40 12S w/4.4:1 gearbox.
Those servos fit nicely in a Graphite tail and offer plenty of room for installation.
After checking a slop on MSK servos and KST servos I think I'll get MKS DS6125 mini for ailerons and DS6125 for flaps. Price difference is almost twice but this is not a $200 glider either.
The good part is that MKS and KST servos are identical in size, so I can install aluminum servo mounts with extra bearing from Windrider.

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Old 09-30-2012, 09:55 AM
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Default RE: Graphite 2E from Vladimir's Models

Longsoar - I hate to rain on anyone's parade, but I think you're going to find the model underpowered with a B40-S motor. The 'correct' motor for the Graphite would be a B50-L with perhaps a 4S battery. Sure, it'll fly with the motor you have, but the climb's going to be rather anaemic.
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Old 09-30-2012, 12:31 PM
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Default RE: Graphite 2E from Vladimir's Models

Yeap Gtarling,
I am aware of that. It will not produce 5 kilo of thrust. It will only produce 1.6kg of static thrust with 13x8 prop for 2.5kg glider.
In my book (I am not competing)  it'll be enough to climb at about 2 m/sec.
But hey, thanks for noticing!

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Old 10-01-2012, 12:47 AM
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Default RE: Graphite 2E from Vladimir's Models

Longsoar - In that case, I hope it meets your expectations.
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Old 10-01-2012, 12:59 AM
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Default RE: Graphite 2E from Vladimir's Models

Gtarling,
Correct me if I am wrong..
By using this motor I will get 1.47A drain per 8.4V when not using a motor instead of 3-3.5A on B50-L
It'll give me more airtime.
As a trade-off I will not get straight-up climbing but rather 30-40 degree climb angle. Instead of climbing for 10-15 seconds it'll take me close to 30.
I am ready for a trade like that.
Also, if later I feel I need a bigger motor - I can always upgrade.
What do you think?
cheers
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Old 10-01-2012, 01:55 AM
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Default RE: Graphite 2E from Vladimir's Models

Longsoar - sorry, I don't understand your '1.47A drain per 8.4V' statement. What people often fail to realise is that to get a glider of a certain weight to a certain height takes a set amount of energy - simple physics. Now, you can either deliver that energy over a short period or a longer period, but the result will be exactly the same. Until you've flown a large glider with an anaemic climb rate, you're not going to realise the importance of getting a high rate of climb to punch through the lower level turbulence as fast as possible. Now, you don't need a 'rocket - like' climb to achieve this, but you really want to have a climb angle of around 60 to 70 degrees if you can. From Motocalc, your B40-12S is going to be producing around 430 Watts on your 12 x 8 prop with a 3S 3000mAh Lipo pack. Apart from the fact that a 12" prop is on the small side for a model of this size, this is getting close to the 500W/15s limit for that motor, so if you have a climb exceeding 15 seconds duration, you also stand to be running into motor heating problems. My advice would be to return the B40 if you can and get either a B50-S or B50-L with the 3.7:1 gearbox and a 14" or 15" prop. If you're really stuck with the B40-12S, then give it a try by all means, but I feel you'll soon be thirsting for some more power!
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Old 10-01-2012, 02:27 AM
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Default RE: Graphite 2E from Vladimir's Models

Gtarling, thanks for your input!
well, as I understand according to Hacker specs motor will drain 1.47A when it's not spinning as an idle drain.
For B50* this rate is anywhere from 3 to 3.5A per every 8.4V depending on a model. I hope I did not miss anything here.
Also, I'll be using 13x8 prop and according to a calculations it'll produce around 1.6kilo of thrust which is a fair amount for the 2.5 kilo glider. Cruising calculated speed is about 92 km/H (close to 25m/s) - more than fair for that glider.
I assume the climb angle will be about 40-50 degrees at a speed of about 55 km/H. Angle will be less at higher speed.

I remember in 70' I saw an article with picture in one of the magazines where real open class glass ship (glider) took off on it's own from the paved runway on six 10cc (around 1HP each) RC engines.

Yeah, I agree, underpower sucks! But I'll try this setup and if anything - I'll upgrade.
Thanks again for your input!
cheers
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Old 10-01-2012, 05:42 AM
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Default RE: Graphite 2E from Vladimir's Models

Longsoar - the figures you're quoting for the motors are what's known as 'no load current' - sometimes shown as Io. This simply shows how much current the motor pulls with no load and is only one of the factors which help determine how 'hot' a motor is. The B50 has a higher figure than the B40 because it's a larger motor with lower resistance that can deliver more power. Motocalc is showing your setup as developing around 80 ounces of STATIC thrust, which ought to fly it OK, but don't forget that the model ISN'T static, so that figure may or may not be indicative of performance. Do let us know about the performance once you have it flying.
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Old 10-01-2012, 06:51 AM
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Default RE: Graphite 2E from Vladimir's Models

Gtarling,
Yes, I did check the resistance on both of Hacker motors and here is the data:
B40 12S w/4.4:1 Resistance: 0.0213 Ohm
B50 12S w/ 6.7:1 Resistance: 0.0129 Ohm
B40 motor has more resistance, both 12 turns short motors and B50 has 2.39A idle current compared to 1.47A B40 has.
My calculations show 1.6Kg (about 50 ounces) thrust while pulling 28A, with max 40Amps it will be probably around 2Kg.
So, even at 28A glider should have enough thrust doing 50 km/H (way above stalling speed). At least I feel comfortable with those numbers.
I definitely will post my report on performance results. It's almost a week wait until all parts arrive (some of them from Taiwan) so I can put everything together.
I also really re-thinking my servo KST choice and a lean towards ordering MKS servos for flaps and ailerons. KST can be used on some less expensive projects.
Thanks for your conversation and notes!
cheers
Mark

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Old 10-05-2012, 12:43 AM
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Default RE: Graphite 2E from Vladimir's Models

Finally got a powerset together - motor mouting screws (which were not included initially) and a HyperSpinner 38/4/0 by Vladimir's Model. Painted spinner in white.

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Old 10-07-2012, 06:59 PM
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Default RE: Graphite 2E from Vladimir's Models

Today I have finished the silicon mold and made a copy of MKS DS65K servo to create a servo frame for it. Silicone used is Rebound 40 by SmoothON.
Silicone would not stick to anything. It makes it easy to work with. I just poored fiberglass resin into the mold.
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Old 10-08-2012, 09:57 AM
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Default RE: Graphite 2E from Vladimir's Models

Seems like a lot of trouble to me. [link=http://www.hyperflight.co.uk/products.asp?code=DS65K%2DSERVO%2DFRAME&name=hyperflight-servo-frames-for-mks-ds65k-servos-pair]Servo Mount[/link]
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Old 10-08-2012, 07:50 PM
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Default RE: Graphite 2E from Vladimir's Models

Gtarling, could be a lot of trouble but beats ordering from UK to US delivery time and those general servo frames make installation kinda cumbersome.
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Old 10-19-2012, 07:33 AM
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Default RE: Graphite 2E from Vladimir's Models

As chance would have it - I ordered servo frames from Hong-Kong and they arrived with wrong bearing screws. I have KST servos and screws thread included in a kit were for MKS servos. So I ordered 2 x MKS DS6125 for flaps and 2 x DS6125 mini for ailerons ($303 delivered).
Chinese servo frames have a huge slope in bearing. I thought I can make a better frames with external ball bearing. Made a mold and here we have it.
My frames altogether lighter than Chinese ones and offer a bigger gripping surface for epoxy. No slope at all in ball bearings (ordered 3x7x3mm ball bearings online $1 a piece). Carbon fiber I had and epoxy is not an issue at all.
Anchors for mounting 4-40 screws were molded-in.
I am waiting on MKS servos to verify they will fit perfectly before gluing frames in place.
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Old 10-19-2012, 08:12 AM
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Default RE: Graphite 2E from Vladimir's Models

Finished tail section with wiring and controls done. Wiring is covered, connectors are covered above the rudder servo.
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Old 10-19-2012, 09:49 PM
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Default RE: Graphite 2E from Vladimir's Models


Quote:
ORIGINAL: longsoar

Finished tail section with wiring and controls done. Wiring is covered, connectors are covered above the rudder servo.
Good work longsoar. It is a bit of a tight fit in there isn't it?

Cheers,

Brad
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Old 10-19-2012, 10:06 PM
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Default RE: Graphite 2E from Vladimir's Models

Hey Brad!
Yeah, kinda jammed in a tail section. That's the reason I used wire guides to make sure they wont interfere with controls.
How's you flying going?
cheers,
Mark

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Old 10-20-2012, 06:37 AM
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Default RE: Graphite 2E from Vladimir's Models

Looking forward to a flight report.

I have the Graphite 3.4M Dbox ( built up wing, not molded) and it is a great thermal soaring machine.
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