Depron Folland Gnat

I had intended to take the Gnat to the DVMFC open day last week end. Although I had test flown it successfully a week earlier a final check showed its 50 mm EDF had failed.
 
Very light it was my first attempt at printing the full duct.
 
As you can imagine replacing the EDF right at the back surrounded by the tail plane and fin is not going to be a simple job.
The replacement EDF is a QX50. I selected the 4s version with a low kV motor although In the Gnat it will be used on 3s to keep the amps within the capabilities of its small battery. Even so it will be a bit more powerful then the 50 mm EDF it replaces.  

Very powerful and beautifully balanced with a 12 blade fan. The bell mouth is removable.
 
The fan hub has a relatively small 20 mm diameter but the motor, stuck on the back, is 26 mm diameter!
This represents a problem. It the exhaust duct has the same internal diameter as the EDF case then past the motor the duct area would be a bit less than the FSA so speeding up the airflow where it is not needed.
The bluff end of the motor is a common issue with small EDFs. It certainly creates additional turbulence and losses in a duct hence my addition of a 'cone' in LW-PLA. stuck on the motor to improved the airflow aft of the motor.
My printed exhaust duct for the QX50
 
It fits on the end of the EDF case with a matching ID but it then increases in diameter slightly to account for the larger motor diameter. It finally smoothly transitions to a nozzle that has a area 90% of the FSA. Such a nozzle size gives the maximum static thrust. An Important issue with a delicate hand launched EDF.
I have just got to fit it into the Gnat, as soon as work on the big Skyray permits!   

Gentle reminder - decreasing the volts INCREASES the current draw! 

Really!
That statement is only true if you are trying to achieve the same level of power.
For any given setup reducing the volts reduces the amps and thus the power it generates.

I feared the EDF of the Gnat was blown so I bought a replacement..
 
After a bit more testing it was the ESC that was at fault so I am in the process of replacing it as I have a direct replacement. 
However I am now left with a brand new 50 mm seriously powerful EDF with no home and I promised myself the Lippisch was my last 'new build' plane until I had more space/   

Problems, problems..

It's tough, isn't it! I have six different-sized e-power gliders here,ready to go, and the other day I dug out my old U2 and dusted that off. Apart from a few 'dings' of hangar rash, and lacking a reciever , it is also ready to go! - Now that lipo's are better than - when was it - 12 years ago - I'm thinking should I - or not?
Then, of course, are all the 'short-wing' models, ten in number, and a couple part-built.
Not counting all the 'retired but useable's' up in the loft, and the heli's!
-
We'll have to learn to crash them more thoroughly, so they aren't worth repairing!