Cheetah

A bit more finding something to do.
Looking through Thingyverse I found a STL file for a 6 x 3.5 folding prop blade that I might be able to use.

Not that I am in favour of printed prop blades but it is only a 50 W motor.
The HK folding prop hub that the fuselage is sized for uses 4 mm thick roots whereas the STL file creates a 5 mm and the root shape is all wrong too however the blade itself looks reasonable so this morning I wondered what could be done.
The blade is printed with the root parallel to the bed so by scaling the Z axis by 80% and leaving X and Y unchanged the root ends up 4 mm thick. The pitch of the blade is also reduce so it is now roughly a 6 x 3.
You cannot edit an STL file so I was stuck with the wrong root shape but being simply too big it was nothing that a bit of work with some files can't overcome.

According to my jewellery scale it weighs 0.774 g making it 0.052 g lighter than the HK original.
Now whether I will be able make another exactly the same is another matter. :woohoo:
It all helps to pass the time.

And now you have at least three more weeks for experimenting!

The complete printed folding prop.


6" proved to be a bit too much for the motor so 1/2" has been cut off each tip.
Works fine and actually folds closer down to the fuselage than with the HK blades however to be sure for the maiden at least I will use a fixed 5x3 as it generates a bit more thrust.

The replacement 370 mAh 3s has arrived from HK, express Parccel Force and according to the label it was posted yesterday. Can't grumble at the service.
The only problem is the new battery is exactly the same! :woohoo:
1C charge.

1C discharge.

Just in case it was a charger issue I used my other B6 with exactly the same results.
So now the task is to see if it can be 'resurrected' with a full balance charge. I did not do this before as I wanted to put in a claim before doing anything to the battery.
We shall see but of course if it proves possible it will likely work on the first one as well.

All this because I wanted to do an RC conversion on a cheap foamy chuck glider that just happened to look a bit nicer than the earlier cheap foamy Lidl.
Balmy, quite balmy. I blame the 'lock down'.

The saga continues.
Concerned I might be over loading the motor I did a 30 second full power run well it did not get quite that far as the motor started to come loose. The answer was obvious. The motor had got so hot that the mounting screws had softened the PLA in the bulkhead. :woohoo: PLA begins to soften at about 70 Celsius but I suspect the motor got a bit hotter than that.
It appears to run a 3s and keep the temperature within bounds it would have to use a very small prop, 3" or maybe less.
So back to the test stand. With a 5x3 and a 2s the motor only just gets warm and pulls quite hard so my guess is this will be a better combination than a tiny prop using a 3s.
As the bulkhead had to be replaced I took the opportunity to redesign it to give the motor some air.
An intake above the spinner.

And 'cheek' outlets on either side.

More a chipmunk than a Cheetah?

I also discovered that I already had some spare HK 5 x 3 folding blades and these produce quite a bit more thrust than the printed ones. The Watt meter shows 2.6 A and 20W on a fully charged 2 s.
With a 500 mAh 2s it now weighs 184 g which if I have done my sums right will give 50 W/lb so a modest but hopefully adequate performance along with quite a reasonable endurance.

More to protect it from 'hanger rash' than anything else the Cheetah is now 'wall hanging'.

I am so short of space that it is having to share a hook with the Sea Vixen.

My fleet hang as well.

no idea why that picture is 90 degrees out but there you go!

Ok Paul, you got me :whistle: I thought you were doing it all from lying down

Sunny and a mild but chilly breeze so I just had to find out if it flies and it does more or less. Sorry no video my 808 spy cam battery did not survive the long period of no use!
First not very successful glide ripped of the RH aileron horn so from then on it had to manage on one!
Not an ideal way to maiden a plane with a substantial wingspan but managed three shortish flights although with rather marginal roll control made worse by pronounced adverse yaw effects.
The flights were short because the 500 mAh 2s battery is at least 3 years old so of dubious performance.
If it stays calm I will have another go hopefully with the camera.

Nice one! glad it at least sort of flew, not sure about trying with just one aileron though!!!

paul
I had no option really. It was either go home after just a 2 second glide flight (and I had walked to the field!) or at least see if I could find out how it might fly.
All mended now but now the wind has got up a bit!

it's dropping here

Grey but almost a dead calm this morning so an edited video of its first 'proper' flight.

The noise on the video was the camera battery running out. It was only when I down loaded the file I discovered the camera stopped working just a soon as I had landed.
A bit short of power but it glides quite nicely.
It tends to 'wander' all by itself which I suspect is down to the inertia of the relatively heavy outer wing panels which creates several oscillations before it settles down and flies straight. Of course being so light some tiny turbulence disturbs it before this can happen.

On the second longer flight I took it much higher into calm air where it behaved rather better but the wing inertia is still present resulting in a slow roll reaction but a sensitive elevator.

I disagree Simon, I thought it looked perfectly powered considering it's weight and the fact it's a glider.
Bloody well done!!

That looked ok to me, Simon!
A bit of fish-tailing is normal for a long-wing short-coupled fuz. A bit more fin area might help, but that would bring the c of g back!