Mayday - Mayday !!

L

Lucas-Lei

I'm a 15 y/o fanatic of aircraft. I live in the are of Leiden (and in Meerkerk during the weekends).
I commited to build and test an RC bi-motor airliner as a project for the school.
I have no former experience neither building nor flying an RC.
In consequence: I'm in a big mess and have little time to finish.
I have dimensioned my airliner to be something like: Fuselage = 120 cm; Wingspan = 124 cm; Used materials: foam and wood for structural parts; Total approximate mass = 3.4 to 4.7 kg.
I won't include retractable wheels nor a rudder.
Since I'm short in time, I have already ordered the following elements (though I'm not sure they are fully consistent or adequate): => COULD ANYBODY ADVISE?

- 2 - Engines: FMS 70mm 12 Blades Ducted Fan EDF With 2845 KV2750 Motor For RC Airplane RC
- 2 - Hobbywing Skywalker 2-6S 80A UBEC Brushless ESC With 5V/5A BEC For RC Airplane (one per motor)
- 1 - RC Plus Skysport regelaar - 20A - 2-3S - BEC (BEC for receiver electronics supply) - Question: Do the servos require a BEC supply?
- 1 - 8CH DSMX High Speed AR8000 Receiver Extended Antenna For Spektrum DX7s DX8 High Quality Accessories
- 1 - 10 stks/partij 3.7g Mini Micro Servo RC Vliegtuig Vliegtuig Helicopter Boot Auto Model Onderdeel Groothandel + Gratis Verzending
- 1 - 7600MAH 7.4V 2-CELL 25C LIPO BATTERY
- 1 - RadioLink T8FB 2.4GHz 8CH Radio Control System

I tried to make simulations using Kerbal Space Program by creating parts of mass and thrust similar to the one of my projected model, though the system does not support such a light downscaled parts. Is there any simple and easy access simulator you could know?

I would like somebody to help me in this critical moment: The plane should be manufactured and tested before mid August !!

PLEASE HELP
I'd much appreciate if anybody could contact me thought the forum or by emall to: lucaslei2003@gmail.com
........
Kindest regards,
Lucas
 
Design and build a twin engine edf from scrap is.. a nice challenge.

Calculate the trust from your engines with the battery's you want to use. ( or make another choise of engine / battery for the trust you need)
Choose a "delta"-shape plaine with a simatrical wing-profile. (A delta-shape plane does fly quite easy)
Try to keep your "weight to trust"-ratio below (some where) 70%.
100% is perfect, 50% is ... not to much.
 
Laatst bewerkt:
An plane equipped with edf engines is a special type of plane..
Even for the experienced pilots, it will be a special one..

For a normal plane, these engines are to fast.
2750 kv = 2750 rpm per volt, so if the battery is 8 volts, 8x2750=22.000 rpm.. most propellors break at these speeds

The BEC in the two speed controllers need to be disabled. two power sources in a electrical circuit means trouble.
at least, one of them.
the controls (servo, receiver) take there power from the BEC unit.
as long as the model stays small, servo's simpel.. maybe it can work with the BEC inside the speedcontrol.
A seperat one is better..

For the servo's, you have selected 3,7 gram servo's.
this can work, is the model stays simpel, slow, normal.
with the edf motors, it will be a fast plane.. not suited for simple servo's..

You could better work the other way around.
- first, build a simple, proven plane.
- Learn to fly.
- Design the new plane
- ask experienced people for there opinion over the design
- choose the electronics according to your designed plane. all things need to be strong enough.. or the plane will self destruct.

as mentioned above, flitetest can help you..
 
Student zei:
For a normal plane, these engines are to fast.
2750 kv = 2750 rpm per volt, so if the battery is 8 volts, 8x2750=22.000 rpm.. most propellors break at these speeds
Klik om te vergroten...

No props will be hurt during this experiment :hammer:
4S EDF units running on a 2S battery will most likely mean that they will hardly generate any thrust at all....

onno10 zei:
What you do is buying stones, cement, wood and nails to make a pizza. That is not going to work.
Klik om te vergroten...

That's even the gentle way to say it.
 
Like what the others have said already, a very ambitious project for a raw beginner, and even one with a time constraint.....but I will reserve judgement.
Besides the comments the others have made, two more:
- Judging by your description, the Skysport is another ESC on top of the two Skywalker ESC's , which you don't need. And in case you meant a separate (U)BEC to power the Rx and the servo's, you do not need that, your ESC's have a built-in UBEC to do that job. Only one should be operative, take the red wire out of the plug on the wire going from the other one to the Rx.
- I don't see why you would need the Spektrum antenna extension, it probably will not fit your Rx that comes with the RadioLink set anyway.

And another thing, publishing your email address like you did is asking for the spam crawlers to find it and inundate you.
 
This is indeed a very ambitious project, not something you will finish in just a couple of weeks. This will take some months at least.
The best way to get good advice and help, which you will really need, is going to a model flying club. In Leiden is a club and not far from Meerkerk is also a club you can go to. You will find the website of the Leidse Luchtvaart Club here: http://www.leidscheluchtvaartclub.nl/
The club close to Meerkerk is the Air Fighterclub Gorinchem and you find the website of this club here: http://airfighterclub.nl/
 
Sorry this project totally makes no sense to me.
No experience you shouldn't even think about a project like this.
But your component choice is really really weird. Did you even read some specs at all.
Most EDF's run on high voltage. You could read it in the EDF spect. 4s 1.6kg thrust.
with two of them you neve could use those cheap 3.7 grams servo's

So first of all buy a trainer and start reading and find someone to help.

Leave this EDF project. just start with a simple proppelor plane as your first build.

Did make a EDF foam plane just for fun but I allready had some experience but never with EDF and this even causes me enough issues to get the EDF a bit running. Changed the inlet several times.
 
Laatst bewerkt:
And then a plane, 124 cm wingspan, weighing between 3,4 and 4,7 kilo?????

Really????
 
I think we all agree this is an over-ambitious project, to put it mildly. But rather than debating this further, can we not restrict ourselves to providing any help the TS has asked for when that is within our capabilities? I am not familiar with designing jets, so I think I have provided everything I can. Who knows, maybe his school project is about setting yourself reasonable goals that can be achieved in a relatively short time, and by now the TS may have understood that this is not the case with his proposed design. So it is up to him how he can/will proceed.

Max.
 
brutus zei:
Is that a beginners plane????
Klik om te vergroten...

No, it isn't. Where did I say it's a beginners plane?????

By the way, this topic is about building an EDF, which isn't a beginners plane anyway. And for an EDF, 124 cm wingspan, weighing between 3,4 and 4,7 kilo isn't strange at all.

If you want to say something about weight/wingspan ratio, you should compare it to similar planes. Don't compare EDF's with beginner planes. The fact that the topic starter is a beginner, still doesn't make the plane he wants to build a beginners plane.
 
Opgeschoond. Gelieve ontopic blijven en rustig wachten tot de topicstarter weer reageert.
 
Thanks to all! As of now I have changed the plane a little bit, I am not using the EDFs which I mentioned in my initial message (I'm using 4 EDF's, which are less powerful, instead of two of more power, and an adequate 4-cell battery) and the weight of the aircraft will be less (around 2.5 kg). Other changes that I have made include the ESC/BECs and the servos, which are bigger. Here-below I attach some photos showing the progress.

Now I have a question. I cannot cover the fuselage with the foam material because otherwise it becomes too heavy. Instead, I would like to wrap it with "Japan" paper or something similar (the paper that is sometimes used to cover a balsa fuselage and wing skeletons), but I can't find this kind of paper nor the adequate varnish anywhere.

=> Can anybody suggest how/where to find it and/or how to wrap it so that it stays sturdy yet light?



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I forgot mention that my experience with flying these RC's is minimal, so the day that I finish my model and I were ready to make the maiden fight, I definitely need an experienced pilot who knows how to fly EDFs together with me to take the lead on it and share the experience. I intend to do it at the Air Fighter Club Gorinchem, which is very close from where I live. I still did not contact anybody there, but will do soon in order to ask for access and usage of their air space.....
 
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