|Jun 27, 2012, 10:24 PM|
FeiBao L-39 EDF version with Schuebeler DS-77-6745-700
After a couple of weeks (12 to be precise) I finally receive today my jet. From this point on I will be building and hopefully posting some pictures of the process. Before I start the thread there's some people people i will like to thank for their time answering questions regarding the plane and other stuff too.
Simon Peckham (EDF Crazy) - Who helped me with some measurings of the
fuselage here and there.
Neil Jarvis (Neil Guildford) - Who shared some measurings of his Viper Jet
because I found a video of him in Youtube.com and
fell in love with the sound of it.
Tam Nguyen - For aswering all my PM's and emails regarding the plane
conversion to EDF.
Stuart Maxwell - For trying to keep my in the right direction in this project.
Mike Warren - For staying there with me all the time even when all the other
persons told me I was trying to use a bigger unit than I should.
Ron Romiti (Ron 101) - For directing me the right way since day 1.
Air Sally - For answering my questions regarding ducting.
I will like to ask everybody to respect other different opinions. I decided my gear based on the info on hand. But I have a pleasant surprise for everybody!! Just wait and see. I will tell you really soon.
Like I said before without this guys this build wouldn't start.
|Jun 27, 2012, 11:13 PM|
Here are the pictures. I have been having an error when I update files from the Mac side of the computer so I'm uploading from the PC side.
|Jun 27, 2012, 11:20 PM|
After having a couple of long minutes un-packaging I manage to lay all the parts in top of the shipping box to snap the pictures. I can say construction quality of this plane is awesome. Paint is high quality and it shows.
This version has removable stabs and vertical fin. Which is a excellent option if your transport means are limited. All the control areas are composite hinged (flexible) and the rudder uses 3 Robart type hinges which I replace for the real Robart hinges.
|Jun 27, 2012, 11:28 PM|
I started assembling the rudder and I guess either I'm too perfectionist or I only found a minor flaw in the construction. While checking the hinges, fit and movement I discover that one side of the vertical fin was rubbing in the rudder binding the surface. I check it with a straight edge, mark it and sanded straight. After that the rudder moved freely 1 1/2" each way which is more than plenty.
|Jun 28, 2012, 12:03 AM|
To my surprise the EDF version comes with 120mm ducting so no further modifications of the inlet ducting are needed.
The Schuebeler DS-700 fits like a glove!!
|Jun 28, 2012, 12:22 AM|
Here's a list of the companies which products will be used in the jet.
Servos - Savox SC1251MG Low profile servos (125oz torque @ 6V)
Retracts - Electron-Retracs ER40B
EDF Unit - Schuebeler DS-77-6745-700 (25 pounds of thrust at 14S)
ESC - FighterCat Racing 300A
Batteries - NeuEnergy 6200 mah batteries
Castle Creations - 8mm Bullet connectors and wires
|Jun 28, 2012, 02:56 AM|
Double check fsa at inlets, it might be made for 120 but might not have the volume to feed the 120 you have. Then measure watts amps out then in to see if it's sufficient.
|Jun 28, 2012, 05:29 AM|
Gamalier, im glad you got your jet, With those electric retracts and that Scheubeler fan it going to turn out to be a nice package. Is your DS-77-6745-700 the new version of their 120mm fan? would you be able to weigh the jet and fan before you start. What have they done with the rear of the plane for the outlet, have they made it larger?
Each inlet half looks to be roughly 60mmx120mm high. which would make a single pipe of 120mm. More then enough FSA for the 120mm fan. and you took the measurement from the inside of the intake, Stu recommends measuring to the lip of the intake, which would give you even more FSA. Its a pity the intakes are't better designed each bend is quite sharp. it might be better to move you fan back a bit and make up a an inlet joiner piece to close it up so that it would give the air some time to smooth out.
I see C&C models have flown this quite successfully on EDF, The performance seems quite good.
I experimented a bit with after lights and managed to create this effect on my L-39.
|Jun 28, 2012, 09:02 AM|
Here are the requirements for the DS-77-6745-700 unit regarding FSA, etc.
Fan Diameter 120
Revs per volt 700
Max Current 175
Inlet Area - min 69
Inlet Area - max 89
Exhaust Area - min 64
Exhaust Area - max 77
Shroud ID 120
Shroud OD 126
Shroud Length 100
Fan Length (- spinner) 206
Mounting width 137
Max fan width 151
Suggested Lipo 14S
Max Model Weight 13000
This the FSA I have right now in the plane as it is:
Inlet width - 62mm from center of lip to wall
Inlet height - 126mm from center of lip
Inlet lip thickness - 6mm (which minimum Stumax recommends for his 110-52)
FSA Calculation (From center of lip) - 62² x 3.14 = 12,070 mm² or 120cm²
If you look closely I have more than the FSA needed by the fan. Don't know if that's a good or a bad thing using this unit because I based everything on the old design of the plane with a inlet radius of 55 mm that gave me 9,498mm² FSA which still above recommended FSA. I'm contacting Schuebeler to see how this could affect the project.
In the exhaust I have a diameter of 95mm which gives me 7,084 mm² FSA or 71cm² FSA and Schuebeler recommend from 64cm² to 77cm². I can increase this if I want because this is the diameter of the former in the back of the plane not the fuselage. (That's 105mm).
With this change in the Inlets, Exhaust and mounting are the possibilities with this fuselage are great. I decided to use the Schuebeler because it required less FSA than other units with the same shroud diameter. (Dynamax, Vasafan 120, Tams TJ 120, Stumax 120-48).
|Jun 28, 2012, 09:20 AM|
Neil is the newest version of the DS-77. (1320g)
I sent Schuebeler an email regarding the FSA (previous post) because I have more than I need. The current intake lip is 6mm thick which is the minimum Stumax recommends in his 110-52 fan. If Schuebeler says it can post some problem because of overfeeding the unit I can reduce the FSA by making a bigger radius with fiberglass cloth or epoxy and microballoons mix which will benefit me in both areas (less turbulence and bigger/better radius thickness). On the back the fuselage has 105mm diameter and the exhaust former has 95mm (Good for 71cm² FSA).
I guess now that Feibao addressed the issues Tam suggested them years ago to increase the inlets for EDF usage paid off!!
Lets see what happens!
|Jun 28, 2012, 11:15 AM|
Looking really good
you picked out some really nice hardware, I think it's going to go great!
Now with that said we are always looking for ways to make it the best it can be... I see the down fall being the ducting, it had a very sharp inner bend to the fan.
When I was doing my DS-94 HST Daniel recommended that I go with open ducting... I wonder if he still feels the same?
You could always back the fan away from the ducting to the very back of the fan mount and put a bellmouth on the fan.....
I'd try the closed ducting setup also, just because I don't like open ducting for the fact that a screw or rock could end up in the fan...
But just something to think about
looks great and looking forward to more progress
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