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        Discussion Newbe, Foam MD-80, 2.3m long.

#1 chochmah Dec 10, 2009 05:43 PM

Newbe, Foam MD-80, 2.3m long.
Hi, I’m new to RC-Groups and new to RC-Planes. However, I have been watching Dave Powers with his Foamies for quite some time and always wondered: How hard can it be.

To get It out of my system I’m going to try building a MD-80 out of Foam. What I’m aiming for is something that resembels a plane, takes off and would potentialy fly. Flight characteristics are largely unimportant since I’ll crash it at first flight anyways. Provided my Plan is feasible I'll do a build-video around New-Year.
  1. Step:
    I took this picture here http://www.ph2.net/md80/b0.jpg

    from the Internet and made a blown up 3D Model. (Length is about 2.30m)

    • Red=Servos/Engines
    • Violet=Batteries/Receiver/etc?
    • White/Gray=3mm/6mm Depron/EPP
    • Black=Carbonrods
  2. Step Equipment:

  3. Step Questions:
    • 2KG Thrust means MAX-Weight 6KG. Is that correct and will that be enough?
    • Are the Wings/Fuselage stiff enough?
    • Weight of Depron is aprox: 20gr per Liter
    • Weight of EPP is aprox: 33g per Liter
    • What speed controls do I need.
    • What servos do I need?
    • What Batteries do I need?

Thanks a Lot and Please keep in Mind that helping me will almost certainly result in a nice Crash-Video fo everyone to enjoy :)

#2 jhaywood Dec 11, 2009 08:14 AM

are you going to publish plans?

#3 chochmah Dec 11, 2009 01:54 PM

Structural Design
The structural Design is finished as far as I can tell. I found the Radio in my Attic. It's an Graupner FM440 without Receiver or cristals. Can I use any Analog Receiver and any cristals with that?

ps. If there's interest I can certainly make plans, but I have to remind you that I have never build an rc-plane before and will most likly crash and burn.


6MM Depron Parts:


#4 chochmah Dec 11, 2009 09:15 PM

So, basic electric Setup:

For to EDFs I should be using 2 ESCs and 2 Batteries. Is that Correct?

If someone with more expertise then I have sees major flaws with the setup below, please correct me:

EDF&MOTOR: EDF70 with 3800kv Motor Assembled 2 472g=2x236g @ 11.1v
Current: 34A
Thrust: 28.9oz
Power: 377.4W http://www.hobbyking.com/hobbyking/s...idProduct=7887

Batteries: 2 344g=2x172g AHA
33A http://www.epp-versand.de/showartike...rn=a_akkus.php

ESC: TP W30A Brushless Speed Controller. 2 70g=2x45g Spec.
Current max: 33Amp
FET: 15
BEC Current: 1.5A
Timing: Auto
PWM: 8k
Lipo: 2-3
NiMH: 4~12 http://www.hobbyking.com/hobbyking/s...eed_Controller

Receiver: Corona 4Ch Single Conv. Rx 35MHz 5g http://www.hobbyking.com/hobbyking/s...ithout_Crystal)

Crystals ?

Servos: HX5010 2 78g=2x39g Dimentions:
Weight: 39g
Speed: .16sec/60Deg
Stall Torque: 6.5kg
Dead Bandwidth: 4us
Voltage: 4.8~6v http://www.hobbyking.com/hobbyking/s...idProduct=3743

Servos: BMS-380 Micro Servo 2 27g=2x13.4g Weight: 13.4grams / 0.49oz.
Dimensions: 26 x 13 x 26 mm / 1.16 x 0.51 x 1.02 inch
Torque At 4.8V: 2.5kg/cm , 35 oz/in
Speed At 4.8V: 0.13sec / 60 deg at no loa http://www.hobbyking.com/hobbyking/s....13sec_/_13.4g

TOTAL: 996g

#5 chochmah Dec 12, 2009 01:40 PM

I attempted to calculate the Wing-Loading:
Length: 245cm, width: 172cm

This is kind of fun. As soon as someone approves the electrics I'm ready to order foam/electronics etc. :)


#6 Xpress.. Dec 12, 2009 09:02 PM

Dave Powers is a very experienced pilot. If you're new to radio control aircraft, don't attempt to fly this. I've been flying for 10 years, and even I would be really nervous to fly it, even if it was mine.

Seriously, if this will be your first plane, then all you will do is crash it about 10 seconds into the takeoff. EDF jets are very horrible trainers, infact, IMO, they should never be considered a trainer, ever, or a first rc plane. You need to go a route that will lead you to success, not failure ;)

#7 chochmah Dec 13, 2009 05:07 AM

Thanks for your Reply and your Concerns (in both Threads)

10 seconds into the takeoff seems optimistic, you have more confidence in me then I have ;)
I do realize that we will not be able to "fly" that plane although the other person involved has more experience with flying RC-stuff than I have (combustion Engines). It's really more about spending new year together and building a "real" RC-MD80. We don't have time in our daily routines to pick up a new hobby anyway. - It would be nice to at least pop a wheelie and make a short hop or something similar daring though.

so a quick look on the setup would be very appreciated. Just tell me if the components blow up when connected together. :)

sincerely yours Chochmah

#8 chochmah Dec 13, 2009 08:01 PM

Wiring as far as I understand it:

#9 chochmah Dec 15, 2009 10:50 PM

Stiffend up the airframe a little bit and moved the servos forward into the wingbox. The CG in general is a few % behind the front of the wingroot?


#10 chochmah Dec 17, 2009 04:31 AM

The First Shipment of "Stuff" has arrived. I went with a local Internet Store instead of that Chinese Hobbyking-one. It was alsmost 3x as expensive, 300e instead of 110e but to make up for that they forgot to ship the second EDF. :mad:
Well anyways. The Receiver works with my Radio the external BEC and the Battery. All Servos seem to be alright. I did not test the EDF yet because I suppose I'd have to mount them somewhere before connecting it to a LiPo.
Not quite sure how to connect the wires. Different Plugs or no Plugs at all.

#11 chochmah Dec 21, 2009 02:56 PM

Wingbox Bulkheads:

#12 68Strat Dec 21, 2009 06:29 PM

Very nice! I am watching. There doesn't seem to be much interest in nice scratch builds in this forum anymore so this is nice to see. Your cutting work looks very precise and clean!

#13 chochmah Dec 22, 2009 06:20 AM

Thank you! I'm using a template made out of cardboard. Makes cutting a lot more precise.

Solderd all electronic components together. Everything, including both EDF work. Batteries and Motors are now connected with one set of wires and two selfmade Y-Junctions.
I disbanded the original Plan to have the Powersupply of EDF1 and EDF2 separately because of the weight of the cable. 1m of 2.5mm Copperwire weights about 100g, that would have made 300g of powercables alone in the Dual-Wire Configuration. The large distance between Engines and Batteries really is a Nuisance, especially since the U-BEC has to be solderd on somewhere in the middle to connect to the receiver which is located in the Wingbox.
On a positive Note: Speed Controls and Batteries remained almost icy during the 2 Minute Test. :)

#14 chochmah Jan 04, 2010 09:42 AM

I run out of Uhu Poor and have to reorder it before I can continue since Uhu Hard seems to desolve the EPP.
Some Pictures showing Progress:


#15 alpea 41 Jan 04, 2010 10:06 AM

Nice progress . I am also watching

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