Depron Heinkel HE162

Whilst I don't profess to know an awful lot about the subject, I would suggest that the biggest problem is the fact that you have an unknown quantity to start with. For example; the 70mm EDF in the Viggen is off the shelf & all the data on it's 'expected' performance is available. This makes calculations for the thrust tube & exhaust length, taper & diameter a lot easier. In my case I don't need to worry about that, as the models designer has already done the calcs. Correct me if I am wrong, but you have a prop designed to run in free air in a duct, with no data to suggest how it will perform ? To me that only leaves two choices, an awful lot of experimentation or replace it for a proper EDF, which I guess will require a lot more power. It is a bit of a dilemma, isn't it ! Moving the fan forward a bit does sound like a good place to start though. Not only will it allow the exhaust to taper to give the best thrust/ jet flux, but by moving the CG forward, allow a bit of leeway in the battery size & position. I will be interested to see how you solve the problem, & I am sure you will !

I guess there's only one way to find out!

Crash
I tend to agree with your observation, however the motor combination is not exactly untried as it is the same motor and prop I have used in ducts before, 2 on the A350 and 4 on the AN124 all running on 4s.
The major difference between them and the He162 is the inlet portion of the duct is nearly 5 times longer.
It is therefore quite possible that the prop is effected far more by the slight drop in inlet pressure than a fan would be. It is also possible that with forward motion the inlet pressure at the prop face will be restored and something like the 'free air' performance will return.
First I will try Eric's suggestion of blowing into the inlet to see if that helps.

Thinking about it I do have one EDF duct that is proportionally even longer than the HE162 and its only a 3 blade fan! It works well enough but for cosmetic and CoG reasons the fan is right at the front of the duct. It looks like the answer was actually there all the time, I just did not know it! :huh:
However moving the motor/prop to the front of the duct on the HE162 would involve a major and complex rebuild. To make matters worse I have no more 2mm Depron! :woohoo:

If it helps there are places advertising 2mm white depron.

I think before I consider tearing the HE162 to bits I will attempt to fly it. At full power it is not going to pull out of your grip but it is still positively there. You never know but I will pick a pretty calm day!
In the mean time there is some testing that can be done.
First I printed a simple thrust measuring rig.

The weight of the motor/prop is exactly counterbalanced so the scale reads thrust directly.
The motor in free air produces 260 g thrust on a 4s.
I then discovered that the motor appears to 'miss' at maximum power on a 5s. It could be the motor or the ESC I am using. Its a big 60A job rated for 6s (it weighs quite a bit more than the motor!) but it might not be happy with the 42000+ rpm. ESC timing?

As the He162 duct is all printed I easily modify and reprint some of the bits so the motor can be mounted just behind the bell mouth to test how well it performs when compared to 'free air'. If it shows it can produce 500+g thrust on a 6s then it would be worth making a complete new nacelle for the He162 and rearranging all the internal components to account for the motor moving forward by nearly 2 feet!
ps
It would also likely avoid the servo hesitation problem as the longest extension would be less than 500 mm rather than the present 1500! :woohoo:

Impressive work Q.

Did you print the thrust rig in one piece? I cant work out the orientation for printing, motor mount face down on the printer bed??

Regarding motor timing. If you have a program card for the ESC it may well be worth checking the timing. It certainly wouldn't hurt to try setting it a bit higher. You may loose some low down torque & draw a bit more amperage, but gain the top end RPM.

wonder if the blades are flexing at high rpm? that would explain the noise..

Or going trans/supersonic?
There was a guy at our club a couple of years back, had a high performance electric 'missile' that ate a prop every flight, because the tips were going supersonic and shattering!
It made one heck of a row at full chat, in flight, a bit like a circular saw hitting a nail!

not sure I'd be happy with nylon blades at those revs, is there a carbon upgrade avaible I wonder?

Fantastic today, warm and very little wind so it was time to test the HE162.
Just too big to get in the car in one piece which is a pity so put it together at the field, checked every thing worked, the stab on, full power and launch gently into wind.
It flies, very slowly and a bit short of thrust as expected but it simply won't turn! :woohoo:
It just exhibits the equivalent of extreme aileron yaw. It banks but continues in the original direction. Tooand much aileron and it simply drops the lower wing - probably stalled.
First flight (15 seconds) being careful did achieve a 180 turn and just able to recover the stall and land reasonably.
It even got a bit dirty. Mud from the landing.

Second flight (10 seconds) tried to turn with a bit more bank. Gave the same result but this time the wing drop was so extreme it rolled upside down and flopped onto the ground. :ohmy:
Dislodged the nacelle but no other damage.

Have to have a bit of think!

RalphCorrect! motor face down. I could actually be printed with the bottom beam face down but I was anxious that the motor bolt holes were truly circular and the correct diameter.

Note the use of 45 degree angles to avoid needing printed supports.

needs rudder...

I expect it will net both a lot of rudder and fin area too!
I seem to remember the directional stbility and control was not considered the best unless you had the ability of Eric Brown.

First is to install dual ailerons so the differential can be set to 100% if required. I believe my version of the Lemon stab has the stab function on channel 5 as well to allow for dual ail.

In the meantime this is the bell mouth of the HE162 with the motor and prop mounted as far forward as possible .

I would need a spinner.
Mounting the motor forward like this would have some advantages. It would reduce the length (and weight) of ESC to motor wires from 800 mm to 20 for a start!

These are the next steps.
1, Test the HE162 'as is' but with dual ailerons to see if aileron differential can reduce the adverse yaw to the point it becomes flyable even if not exactly manoeuvrable.
2. I have run the motor in the front duct with a 4s without a problem. It absorbs 120.1 W whereas in the back of the long duct it only absorbs 92.6 W. A useful 30% increase.
3. Build a complete new duct but with the exhaust duct made of Depron rather than printed. I estimate it could save nearly 50 g. I will have to source some 2mm Depron to do it. This will be tested 'stand alone' to see the thrust level before proceeding to alter the HE 162.
4. Reorganise the layout of the electrics which will not only save a bit of weight but by reducing the motor wire length should reduce any voltage drop.
5. If I can get its power to weight to approach 100 W/lb, with a 5s battery if necessary, then it should be able to carry the weight of working rudders that hopefully would improve the flight characteristics to an acceptable level.

Well that's the plan.