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Old Sep 21, 2012, 04:24 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Build Log
(5.2m) 205" MQ-9 Reaper RPV / FPV and UAV

Hi all,
as of monday i will be Designing and building a 5.2m (17ft) MQ-9 Reaper using the ArduPlane board For the UAV Control Side of things.

I Have given myself 1 year to complete this project From Planning to Finish
so sit tight Because your in For the Long haul....
also i have attached a Screen Cap Of the Cad plans in Autocad (measurements are in mm)

This 1/5 scale General Atomics Reaper UAV Will be optimised for 3 things.... Loiter time, payload Ability and if and when needed All out Speed.
Also for less Drag i plan to incorporate semi-scale Retracts
as i am Currently halfway Through Designing this In CAD i am able to measure internal payload spaces ...

The payload bay of the Reaper is sized to carry an 10,000 MAh of Lipo's
a second Video Tx and secondary Rx (to pan and Tilt the cameras) and a GPS/OSD with Pitot tube
alongside a BEC and 2200mah 2s Lipo

I have attached

Though i will need some advice for servo's and the Motor
Servo wise i was thinking some 9g digi Metal gear (good enough or do i need more Grunt ?)

Motor wise i need something to swing a 3 blade 19x4 or 19x6 prop on 4-6 cells for long sustained periods of time

any ideas?


P.s im looking for around 3-4 hours of loiter time initially (6 hours with the Aditional Flight Pack in the Payload bay )
Would 20,000 Mah be Sufficient ?

K



The U.S Customs and Border Protection Livery is the paint-scheme i'd like to do her in

^ Purdy!

Lookin Mean..


Awesome!





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Last edited by Keenan smith; Sep 23, 2012 at 05:37 PM.
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Old Sep 21, 2012, 05:03 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Almost done With the Plans, i have Done all the airfoils and am halfway through the Fuselage profiles.. (some Will be later modified)

I will Also Be picking my power setup soon and will need some help with that (for Running on 5s) i need a Motor to Efficiently Swing a 19x 4 or 7 Prop at less than 140A
And on the Upside the Wing-loading is in the Range of a Trainer-Sport plane So it shouldn't Be Too much of a beast to Fly either

K
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Old Sep 21, 2012, 05:06 PM
Tim
United States, AR, Fayetteville
Joined Sep 2012
47 Posts
Looks awesome! What's your budget for this?
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Old Sep 21, 2012, 05:08 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
Originally Posted by loneboat View Post
Looks awesome! What's your budget for this?

Around £1K GBP All up.. However that will be spent over the Course of a Year

K :Cool:
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Last edited by Keenan smith; Sep 21, 2012 at 07:02 PM.
Old Sep 21, 2012, 11:54 PM
I like to fly!
United States, WI, Monona
Joined May 2011
227 Posts
What are you looking at for final weight? 20,000mAh is going to be a lot of weight with a high cell count. The plane I'm working on right now flies on 10,000mAh split between two motors, each running off of 9s. Battery weight comes out to about 5.6lbs, and that's just for the power, not including the receiver battery.
The weight of the plane can make or break flight times, cost of the motor, and performance.

Alex
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Old Sep 22, 2012, 01:33 AM
York Electronics
Gary Warner's Avatar
Dallas Tx USA
Joined Apr 1999
2,505 Posts
As to the questions...

9g servos ain't going to cut it. Don't skimp here. Tons of trouble just waiting in the wind if you do. In the grand scheme of things, the extra weight is negligible.

For power/duration take a look at the watts per pound. To climb with any authority (Read: slow yet manageable), plan on 50 watts per pound. Once at altitude, something around 20 watts per pound will keep her afloat assuming you have chosen an efficient prop for the lower airspeed AND a conservative flight attitude, airspeed and reasonable wing loading for the Reynolds numbers.

15 pounds might be a bit high if you were to put the airframe on a serious diet.

So, an example would be 10 pounds and 5 cells at 10Ah.

CLIMB:
50 watts per pound = 50 * 10 = 500 watts
500 watts at 18.5 volts = 500 / 18.5 = ~27 Amps
10Ah / 27 = ~.37 hours or 60 * .37 = 22.2 minutes of climb

LOITER:
20 watts per pound = 20 * 10 = 200 watts
200 watts at 18.5 volts = 200 / 18.5 = ~10.8 Amps
10Ah / 10.8 = ~.93 hours or 60 *.93 = 55.8 minutes of loiter

Glide time after battery exhaustion can be "free" and considerable if altitude gained is high and attitude control is optimized. Glide time - ???

These are best-case numbers with a high AR wing, correct airfoil and excellent attitude control. The lowest watts per pound I've actually flown for loiter (outdoors at the flying field) was using a motor glider and it was 9 watts per pound in near perfect conditions. If you (or others) want to assume other watt per pound figures, just plug them into the above and see what you get.

EDIT: Other "food for thought"...

Assuming the 10Ah 5 cell pack is "FIXED" AND the overall flight profile used an average of 20 watts per pound AND 3 hours of flight was expected...

The total weight would need to be:

10Ah / 3 hours = ~3.33 amps
3.33 amps * 18.5 volts = ~61.5 watts
61.5 watts / 20 watts per pound = 3.075 pounds

A "3.075 pound" project might be a bit hard to come up with at this scale.
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Last edited by Gary Warner; Sep 22, 2012 at 02:39 AM.
Old Sep 22, 2012, 08:30 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
Originally Posted by alexkmmll View Post
What are you looking at for final weight? 20,000mAh is going to be a lot of weight with a high cell count. The plane I'm working on right now flies on 10,000mAh split between two motors, each running off of 9s. Battery weight comes out to about 5.6lbs, and that's just for the power, not including the receiver battery.
The weight of the plane can make or break flight times, cost of the motor, and performance.

Alex

I May UpThe mah to 15,000mAh and Down The Cell Cont to 4
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Old Sep 22, 2012, 08:46 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
Originally Posted by Gary Warner View Post
As to the questions...

9g servos ain't going to cut it. Don't skimp here. Tons of trouble just waiting in the wind if you do. In the grand scheme of things, the extra weight is negligible.

For power/duration take a look at the watts per pound. To climb with any authority (Read: slow yet manageable), plan on 50 watts per pound. Once at altitude, something around 20 watts per pound will keep her afloat assuming you have chosen an efficient prop for the lower airspeed AND a conservative flight attitude, airspeed and reasonable wing loading for the Reynolds numbers.

15 pounds might be a bit high if you were to put the airframe on a serious diet.

So, an example would be 10 pounds and 5 cells at 10Ah.

CLIMB:
50 watts per pound = 50 * 10 = 500 watts
500 watts at 18.5 volts = 500 / 18.5 = ~27 Amps
10Ah / 27 = ~.37 hours or 60 * .37 = 22.2 minutes of climb

LOITER:
20 watts per pound = 20 * 10 = 200 watts
200 watts at 18.5 volts = 200 / 18.5 = ~10.8 Amps
10Ah / 10.8 = ~.93 hours or 60 *.93 = 55.8 minutes of loiter

Glide time after battery exhaustion can be "free" and considerable if altitude gained is high and attitude control is optimized. Glide time - ???

These are best-case numbers with a high AR wing, correct airfoil and excellent attitude control. The lowest watts per pound I've actually flown for loiter (outdoors at the flying field) was using a motor glider and it was 9 watts per pound in near perfect conditions. If you (or others) want to assume other watt per pound figures, just plug them into the above and see what you get.

EDIT: Other "food for thought"...

Assuming the 10Ah 5 cell pack is "FIXED" AND the overall flight profile used an average of 20 watts per pound AND 3 hours of flight was expected...

The total weight would need to be:

10Ah / 3 hours = ~3.33 amps
3.33 amps * 18.5 volts = ~61.5 watts
61.5 watts / 20 watts per pound = 3.075 pounds

A "3.075 pound" project might be a bit hard to come up with at this scale.

Wow Thats alot of Math.. .Well I I will Use your Math to Select my power System
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Old Sep 22, 2012, 08:50 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
9g servos ain't going to cut it. Don't skimp here. Tons of trouble just waiting in the wind if you do. In the grand scheme of things, the extra weight is negligible.
Ill be using Digital Mg (15-20g) slim wing servos

K
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Old Sep 22, 2012, 09:04 AM
RC = Empty wallet
InvalidUsername's Avatar
Australia, VIC, Melbourne
Joined Jan 2005
356 Posts
Quote:
Originally Posted by 3DDFHobbies View Post
Around £1K GBP All up.. However that will be spent over the Course of a Year

K :Cool:
A model of this size will need above average gear. And with a budget of around £1k I think you will be lucky to get a good power system, still you need an airframe, radio gear, cameras etc. What type of construction will you be using for the airframe? Have you thought about how you intend to transport this aircraft to the flying field? Don't waste time with 9gram servos you should be looking at standard size servos. Do you have radio gear suitable for operating the aircraft and its functions? Not trying to put you off in anyway but there is more to just designing a big model and using sub par electronics
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Old Sep 22, 2012, 09:40 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
Originally Posted by InvalidUsername View Post
A model of this size will need above average gear. And with a budget of around £1k I think you will be lucky to get a good power system, still you need an airframe, radio gear, cameras etc. What type of construction will you be using for the airframe? Have you thought about how you intend to transport this aircraft to the flying field? Don't waste time with 9gram servos you should be looking at standard size servos. Do you have radio gear suitable for operating the aircraft and its functions? Not trying to put you off in anyway but there is more to just designing a big model and using sub par electronics
Hi InvalidUsername I hope this Post answered your Questions

Quote:
What type of construction will you be using for the air frame?
For the Wings Hot-wired Foam Core With Balsa Sheeting
and For the Fuselage ill Be Carving A Fuse Plug And Molding it in Fiberglass

Quote:
Don't waste time with 9gram servos you should be looking at standard size servos.
I Know I said in an Earlier post That in The Wings ill Be using Slim Wing Digital Metal Gear Servos .. (with 3kg of tourque) for the Flaps and Ailerons..
and i'll be Using Futaba Digital Standard Sized Sized Servos... For the Rudder And Ruddervators.. (and 1 11g MG Servo For Nosewheel steering.. )

Quote:
with a budget of around £1k I think you will be lucky to get a good power system, still you need an airframe, radio gear, cameras etc.
I'm Gonna Use a Nice NTM prop-drive Motor, A Castle 110A ESC Opto and a Gens Ace Or A grade Nano tech 5s 5000mAh 40-60C Lipo Swinging Either a 16x8 prop or.. a 19x6 Prop
In terms Of Radio Gear Im Getting Rid of My 9x and Will Be upgrading To a Hitec Aurora 9 Very Soon
and For the FPV stuff i'll Be using the immersion RC EZUHF With an Immersion RC 700 TVL Camera

and I'll Be Posting The Power System I may use in The Next post ..
K

P.s For a Wingspar i'll Be using a Huge Carbon Fibre spar..
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Old Sep 22, 2012, 09:49 AM
Straight up is all I ask
Fairfield Ct USA
Joined Apr 2002
2,323 Posts
At 15 -16 lbs this is a "what I would call a 120 size airplane " maybe more like a 50cc airplane . So all parts should be in this category .Your power system should be 1500-2000 whatts and get the cell count up to 9-10-or 12 so your amps stay lower . 5 cell lipo is all the rage in .40 size airplanes 4-6 lbs .
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Old Sep 22, 2012, 10:00 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
Originally Posted by jmolwitz View Post
At 15 -16 lbs this is a "what I would call a 120 size airplane " maybe more like a 50cc airplane . So all parts should be in this category .Your power system should be 1500-2000 whatts and get the cell count up to 9-10-or 12 so your amps stay lower . 5 cell lipo is all the rage in .40 size airplanes 4-6 lbs .
Ill Go up to a 6s .. .

K
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Old Sep 22, 2012, 11:18 AM
York Electronics
Gary Warner's Avatar
Dallas Tx USA
Joined Apr 1999
2,505 Posts
Quote:
Originally Posted by 3DDFHobbies View Post
For the Wings Hot-wired Foam Core With Balsa Sheeting
If it helps you, the best I could get with this technique using white EPS foam, epoxy bonded balsa 1/32" sheeting in a vacuum bag and iron-on covering material (without an internal spar) was 75 square inches of wing per ounce. This was exceptionally light for a 72" wing span sailplane. The extra thickness of the airfoil, needed internal structure and likely thicker sheeting would suggest the target weight of the wing will fall close to 40 square inches per ounce for you design IF it's done well. That being the case, your projected wing weight alone MIGHT be a low as 3+ pounds but I'd consider something closer to 4 pounds as being the final practice weight of the wing.

Just sharing what my experience has been with this topic.
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Old Sep 22, 2012, 12:00 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,851 Posts
Quote:
Originally Posted by Gary Warner View Post
If it helps you, the best I could get with this technique using white EPS foam, epoxy bonded balsa 1/32" sheeting in a vacuum bag and iron-on covering material (without an internal spar) was 75 square inches of wing per ounce. This was exceptionally light for a 72" wing span sailplane. The extra thickness of the airfoil, needed internal structure and likely thicker sheeting would suggest the target weight of the wing will fall close to 40 square inches per ounce for you design IF it's done well. That being the case, your projected wing weight alone MIGHT be a low as 3+ pounds but I'd consider something closer to 4 pounds as being the final practice weight of the wing.

Just sharing what my experience has been with this topic.
yeah im Gonna Go for 40 inches per ounce.. Since ill be using a nicely sized spar..
Hopefully My useful Payload weight will be around 5Kg
and i have allocated 1kg for my Power system (minus Lipos... )

K
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