Depron Boeing 727 build thread - RC Groups
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Jan 01, 2009, 09:58 AM
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fabiofleal's Avatar
Build Log

Depron Boeing 727 build thread

Hello everybody.
This is my version of the Freighter Boeing 727-100

The plane was build the same way as neffwaffe's one (youtube) w/ some small construction difefrences. Here are the specs:

Wingspan - 1.4m
Overall Lenght (including fin end) - 1.6m
Weight - 1.16kg
Total static thrust - 560g
Airfoil S4083 (To compensate the lack of thrust through lower stall speeds)
AoA - 3 (Adjustable by a plastic screw)
Steerable nose wheel w/ adjsutable suspension (coil spring)
Washout - 3 (0 AoA at wing tip)
China made fans (Looks like they are GWS Fans and rotors w/ outrunner C20 3600kv motors)
LiPo packs - 3S2P, total 3000mAh
Current draw (from data sheet, not measured) 2 X 10.5A
Fuselage and fin / stab made from 2mm depron w/ a styrofoam structure (profile + bulkheads) reinforced w/ fiberglass rods
4 e-sky 9g micro digital servos (Rudder + nose wheel, elevators and 1 for each aileron)

For those who master portuguese, the complete build thread is posted in the brazilian forum e-voo:

I'm posting the build steps in english as well during the next days.

See You!
Last edited by fabiofleal; Jan 20, 2009 at 11:25 AM.
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Jan 20, 2009, 03:10 AM
Registered User
Very nice Very realistic

Thank you for posting.
Jan 20, 2009, 06:11 AM
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I'm already applying Varig Log colors to the bird:
Depron Boeing 727 EDF 17 Jan 2009 (3 min 23 sec)
Jan 20, 2009, 10:36 AM
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fabiofleal's Avatar

Beginning the build

This plane was build very slowly to avoid problems w/ my wife who uses to complain that I dedicate too much time to the hobby. So, here we go:

The first step is to calculate all the plane dimensions considering the proportions amongst the parts such as nacelles, fuselage height and width, ground clearance, diameter of wheels and so on.

It's very important to link all of the dimensions and proportions to the wingspan. It will be at the end of the day the most important hard point of the project as it will determine whether the plane will fit to my car (or not) and the wing area, which can make the difference between a relaxing or nervous flight and landing.

Another constraint I had was the thrust to weigh ratio. So, the weight has to be within certain limits. To help on this, both airfoil and the angles (AoA and washout) need to be carefully chosen. In this one I decided to use 0 AoA at the tips and 3 of AoA. Therefore it has a washout of 3.
Jan 20, 2009, 10:46 AM
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Cockpit / nosecone

The greatest advantage of the card models is to see how quickly the critical scale parts such as this one get ready without similarity errors. At this time you can think the model will be put together in a few days... Illusion! For single guys, it may even be possible as long as they don't have anybody to shout because of the lots of time spent cutting, bending and applying glue to the parts.
Last edited by fabiofleal; Jan 21, 2009 at 06:42 AM.
Jan 20, 2009, 10:48 AM
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You do have to be very careful when bending depron sheets or they will certainly get wrinkled. Fortunately most of the commercial jets are painted in white. So, After cutting the parts, I covered my fuselage w/ a good white PVC tape which helped to prevent it from this effect. Epoxy glue to hold the parts together but without "closing the fuselage at this time yet, as the structure is not 100% ready.
Last edited by fabiofleal; Jan 21, 2009 at 06:43 AM.
Jan 20, 2009, 10:51 AM
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Backbone structure

This structure provides both strength to the body and also a large surface to install servos and the reinforcements to hold the wings. Its cut from a side view drawing (I got from another thread here but I couldn't recover it now) over a 15mm foam sheet to be the lightest as possible. To improve the overall stiffness, fiberglass rods glued w/ epoxy in both top and bottom as well as in the sides, glued to each of the bulkheads. The light foam used is also easy to cut w/ any kind of blade in case you need to adjust it to fit inside the cardboard parts.
Jan 20, 2009, 10:56 AM
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Tail fin / rudder

Here the things start to get complicated: Big parts w/ several and complex surfaces to be glued at the same time and somehow deformed by the printing operation from the card model file. I used a rounded edge desk to help on doing the curvatures without wrinkles as much as possible.

Due to weight saving and flight safety reasons one of the basic assumptions of this project is to use only one servo to operate both elevators, which is quite hard in such type of tail.

Besides that, the attachment to the body needs to be the lightest as possible and w/ the largest surface to be glued to the attachment points as the whole body core is made of very light (and therefore weak) Styrofoam.

The servo is epoxy glued directly the fin wall 1 mm rigid steel wire for the command rods guided through soda tubes...the lightest as possible. The command rods are actually one part only, like a "U" passing through the servo arm. Each side of this U will push / pull one elevator.

Also directly glued to the fin wall is the balsa stick that acts as the main structural and attachment element for the tail. The vinyl covering is heavy, ok. But it helps to reinforce the tail.

The nacelle for the engine # 2 is a little hard to be put on its position. If you don't place it very carefully it easily gets crooked. It's recommended to step back and look the plane from something like 4m away to see without distortion.

Rudder hinges if taped are a little hard to build if your fin is vinyl covered. I used the "living hinge concept". It prevents the whole hinge to be in trouble if the tape begins to get off the vinyl. If I knew this before, I would paint the whole tail w/ color glue instead of covering w/ vinyl.
Jan 20, 2009, 11:23 AM
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Steerable nose wheel w/ adjustable suspension

Due the gust winds we use to face down here, hard landings are a constant, what requires some kind of dumping system. As the nose wheel height may impact directly to the scale looking of takeoffs as long as it affects the Angle between the wings and the airflow, its necessary to be ajdustable as well as the angle to rudder.

I did this by using small electric connectors to hold and asjust the wheel shaft and the NW main axis. Each of these connectors has 2 screws that can be used to perform the adjusts.
Jan 20, 2009, 01:26 PM
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Landing gear

The simplest and lightest way I know to build landing gears isn't the most well crafted one. But it works pretty well tought most of the people won't take a closer look at the bottom of your model...

What you have to keep in your mind is that the stress cannot be concentrated in a small area of your wing. Besides that, mainly if you fly in a region where the gusts use to be always present, your gear msut be easily repairable in the field, if possible w/ no tools required.

Once again, the reciclabilty of some materials found in our day-by-day takes place.

To comply w/ all the "requirements" I have mentioned above, a PET/foam/PET sandwich is necessary. The impacts will be absobed by the PET plastic without sink marks to the foam and also the PET platform acts as a fixing element due to its reasonable contact area to the wing. So, the PET triangle shown in the picture is glued to the bottom side of the wing.

At the top side of the wing small pieces of PET are glued and very thin pinholes allow the telephone (1mm thick) wires to reach the bottom side. Then the landing gear is tied to the wing by just doing some "trances" in the top side.

As the landing gear main structure looks like an "L", the combination between its shape and the positioning of the wires that tie it to the wing provide the correct locking of the degrees of freedom as shown in the picture.

To complete the gear, you can either do the same as I did in the nosewheel (which is, BTW, a more "professional" job) or do something lighter, as I did, again using PET and telephone thiny wires, glued w/ CA to get everything firmly held.
Jan 20, 2009, 01:42 PM
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Nothing new on these wings but the patience required to put together 5 panels, 4 fiberglass rods and use some basic trigonometry to place the airfoil templates to the hotwire cut operation in order to get the planned values for the AoA and washout.

The only highlight to build such a "big" wing is that you have to put the fiberglass rods exactly above the other, otherwise they won't work and your wing can "clap" in flight. Let's keep in mind that this is a 1kg+ plane and the sweep angle complicates the things a little bit more than if they were conventional wings.
Last edited by fabiofleal; Jan 21, 2009 at 06:55 AM.
Jan 21, 2009, 07:42 PM
Speed Checked
guiga_x's Avatar
Hello Fabio,

Congratulations with your new B727!!!
The plane is a nice bird. The flight is very cool!!!
Im working on my B777 now again. This week Ill back with the engines and pylons to fixation on the wings. Check in my page.

Hub for you brother!!!

Jan 23, 2009, 02:06 PM
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fabiofleal's Avatar

Naceles for engines #1 and 2

These nacelles were made from 3mm depron. In the areas where it cracks you MUST glue it w/ epoxy to stop the cracks to go ahead and destroy your plane. Later on, you can also apply some gap filler and sand it fot finish.
Jan 23, 2009, 08:08 PM
kelberts's Avatar
You should post this in the foamy EDF forum -

Nice work!
Feb 14, 2009, 06:08 PM
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fabiofleal's Avatar


Originally Posted by atr98
Very nice Very realistic

Thank you for posting.
You're welcome!

Actually this project only came up the real world because Zimmerman has strongly encouraged me. Then, I bought the idea and that's the result.

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