A low power ducted fan

[skyman]

Originally Posted by foamjetpilot

Nice design. For more thrust and minimal weight, try extending the thrust tube 3" and have the exit opening be 15% smaller than the inlet..

I agree, this would really help. You might even want to make it 20%. Congratulations and great work

[quorneng]

This is a 'pusher' fan. There is nothing aft of the blades.
The existing 'thrust tube' is effectively just a spinner and goes round with it.

I think of it as a shrouded multi-blade prop rather than a ducted fan and this probably explains why it performs as well as it does at low power settings. It will maintain height on half power.

I hope the next video will show its full 8 minute duration.

A video from a pilots point of view?
Now you could say that's exactly what an on board video is.

[FlyingMonkey]

Originally Posted by quorneng

A video from a pilots point of view?
Now you could say that's exactly what an on board video is.

But in this case, you're the pilot, on the ground...

they/we want to see it from the ground view.

[quorneng]

Not that it proves very much but this morning I wanted to see just how long it could stay up. Rather windy (note the steam plume from the power station) and turbulent making this already twitchy plane difficult to fly smoothly but nevertheless 9:30 on a cheap 1500mAh 3s is not too bad.

YouTube Video

Hopefully when it is properly sorted it should be good for over 10 minutes.

[dkrhardy]

OK, 1st off CONGRATS on thinking out of the box. There were a few naysayers but you did what you set out to do .... AND you're trying to improve on it! 2nd .... what happened to your "house colors"? You repainted it?

[mclarkson]

Originally Posted by dkrhardy

OK, 1st off CONGRATS on thinking out of the box. There were a few naysayers but you did what you set out to do .... AND you're trying to improve on it!

^^THIS

Way to go, Sir.

[JetPlaneFlyer]

Originally Posted by quorneng

Not that it proves very much but this morning I wanted to see just how long it could stay up. .....9:30 on a cheap 1500mAh 3s is not too bad.

Not a bad duration I have to admit.

Out of curiosity, to gauge this model's fan efficiency against a 'normal' prop.. The other similar model you pictured at the start of the thread with the pusher prop; same span, similar weight, same battery.. how long can that one stay up when flown is a similar manner?

Steve

[quorneng]

Steve
No quite fair as the pusher is 1oz lighter, has a slightly greater span (40" versus 36") with a higher aspect ratio and a smaller motor but in terms of performance there is no comparison.
It will practically go vertical on 10A and can easily manage 20 minutes although I have not specifically tested its maximum endurance.
In this video just 20 seconds full power gives a 2:05 glide.

YouTube Video

You could say the prop is at least twice as efficient.

The final experiment on the Ductfan will be to remove the fan & duct, move the booms outward and see how it goes on a 7x6 pusher prop.

[mclarkson]

Originally Posted by quorneng

The final experiment on the Ductfan will be to remove the fan & duct, move the booms outward and see how it goes on a 7x6 pusher prop.

:popcorn:

[Insomniac]

But please, get some ground view of the plane. Stick your keychain camera on the brim of your hat or something, but we'd all love to see it from a different perspective.

[JetPlaneFlyer]

Originally Posted by quorneng

Steve
No quite fair as the pusher is 1oz lighter, has a slightly greater span (40" versus 36") with a higher aspect ratio and a smaller motor but in terms of performance there is no comparison.
It will practically go vertical on 10A and can easily manage 20 minutes although I have not specifically tested its maximum endurance.
In this video just 20 seconds full power gives a 2:05 glide.

You could say the prop is at least twice as efficient.

The final experiment on the Ductfan will be to remove the fan & duct, move the booms outward and see how it goes on a 7x6 pusher prop.

Ok.. that's' close to what I thought.. I guessed a good prop would be 3 times more efficient and it sounds like I was not too very far away from the truth (some see factual statements as naysaying, which i never quite can understand )

It was certainly an interesting experiment and it will be fascinating to see how the very same model goes with a properly sized prop on. I'm guessing you will get over 20 minutes duration. I wonder if you fly gently if the 28 - 29 minutes would be possible that would indicate 3 x more efficiency? I'd also expect a lot more performance with the prop.

Steve

[quorneng]

Steve
You are probably right. The video shows a 0:20 burst giving a 2:25 flight.
It has a full power duration of more than 7 minutes so 7x60/20=21 bursts of power which means over 40 minutes.
I do not know if a 'climb and glide' technique is more efficient than a continuous minimum power cruise. The prop is probably more efficient at low power but the motor and the ESC may not be.

My own record for a 40" span, no lift, continuous cruise power flight stands at 1hr 36mins with this version of my original Wing Dragon.

It had a 5000mAh 2s weighed 19oz and I ended up with a rather sore neck!

[dfwdad]

Great job and I love what you have done with the WD4, me and my son are getting this plane I hope this week, and would like to in the future make a FPV rc out of it. I really am going to have to cut weight and increase the glide ratio to get good battery life. Looking at what you have done I think I may be able to get 30 mins once the cam and all the transmitters are in the plane.

[quorneng]

dfwdad
Nothing wrong with planning ahead but "walk before you run". FPV is quite an ambitious target on a WD size plane. Take it in gradual steps.
Please keep us informed on how you get on.

[dfwdad]

Like you said I have to walk before I crawl, oops, well you the other way, but we have to get the flying of the plane down before we can ever turn it into a FPV. I was looking at your wing designs, and the other upgrade you did and it was very inspiring. I know I do not have the aeronautical knowledge you have, but I feel I do feel I do have the knowledge to make this work with enough reading.

[Bill G]

The first thing I thought when reading the thread was the Edgely Optica, and then saw others had posted it. It would be a challenging build, that I thought about many times.
Quorneng your build reminded me about the FW190TL. Not at all a conventional EDF, and it flies.

[quorneng]

Bill G
Now that it is .....er.....interesting!
I assume the fan exits are either side and look to be quite small compared to the inlet so it relies on the fan creating a significant pressure ratio.

My next test is to completely remove the fan shroud from the Ductfan. The shroud does increase the static thrust a bit but I have a suspicion that when it the air it will perform just as well as a 7 blade prop.

[JetPlaneFlyer]

Originally Posted by quorneng

My next test is to completely remove the fan shroud from the Ductfan. The shroud does increase the static thrust a bit but I have a suspicion that when it the air it will perform just as well as a 7 blade prop.

That will be an interesting experiment. I would expect you would see a loss of performance right accross the operating range, greatest loss at low speed but probably noticable at all speeds.....but I've been wrong before..

The main reason for the duct/shroud on a ducted fan is to prevent air spilling round the tips of the blades. This is especially important when the blades are short and wide (low aspect ratio) because tip losses are much greater on very low aspect ratio blades (exactly like low aspect ratio wings). Normal props get around this by having long slender high aspect blades.
Of course in forward flight the duct/shroud itself causes drag and eventually this drag cancels out any benifit derived from the shroud, my gut feeling though says you arent flying fact enough with this model for that to happen... time will tell.

Please keep us informed on how the tests go.

Steve

[Bill G]

Originally Posted by quorneng

Bill G
Now that it is .....er.....interesting!
I assume the fan exits are either side and look to be quite small compared to the inlet so it relies on the fan creating a significant pressure ratio.

My next test is to completely remove the fan shroud from the Ductfan. The shroud does increase the static thrust a bit but I have a suspicion that when it the air it will perform just as well as a 7 blade prop.

There's one on the bottom also to make the needed exit area, but it proved to be problematic. I had to add a clear defector plate to straighten the airflow along the fuse, with Coanda helping a bit. Before that, it had a pitch-up under power problem. It flies with a bit further forward CG than the prop flyers are using, but it's a good flying plane and not difficult to fly.

I'm thinking of trying it on 4s with a UBEC, as I believe the current will still be within reason. As of now, it's certainly not the fastest "jet" model out there.

It's amazing what you can get from small props, if you spin them fast enough. I did some calcs and decided that an SM64 may have a chance, with a small outrunner and prop. The prop size was determined by the wing clearance, as it was a pusher-tower setup, so there was no trying a larger prop. The plane flew, but not overpowered. Launch was very exciting.
http://www.wattflyer.com/forums/show...3&postcount=19

[quorneng]

Well it certainly flies ductless

but rain stopped play before I had a chance to do very much and to make matters worse a whacking great Atlantic depression is on the way!

[NJSwede]

Ah! I love this thread! It took me from grumpy from a crappy day to smiling ear to ear in just a few minutes! (It also took me from "This guy is *$&*$&-ing nuts" to "This guys is WAY cool"... )

Big applause for a really cool and successful project!

[babylon5]

Originally Posted by Bill G

There's one on the bottom also to make the needed exit area, but it proved to be problematic. I had to add a clear defector plate to straighten the airflow along the fuse, with Coanda helping a bit. Before that, it had a pitch-up under power problem. It flies with a bit further forward CG than the prop flyers are using, but it's a good flying plane and not difficult to fly.

I'm thinking of trying it on 4s with a UBEC, as I believe the current will still be within reason. As of now, it's certainly not the fastest "jet" model out there.

It's amazing what you can get from small props, if you spin them fast enough. I did some calcs and decided that an SM64 may have a chance, with a small outrunner and prop. The prop size was determined by the wing clearance, as it was a pusher-tower setup, so there was no trying a larger prop. The plane flew, but not overpowered. Launch was very exciting.
http://www.wattflyer.com/forums/show...3&postcount=19

I have been experiment on small propeller APC4.5x4 or APC 4.5x4.1 propeller on a n Align motor 3.55KV. and a 30amps ESC . At stationary, the current runs around 27-30amps on 3 S lipo and probably spins around 27,00-30,000 rpm. My friend has the exact same setup but only difference he put it on a DIY depron Su27 while I put my in my 24inches SPAD interceptor.
During flight, my Spad interceptor was screaming like close to 100MPH and gives me 4minute flight with 1750mah till battery flat(motor cut off.) while his barely run over 2minutes with a 2200mah 3S and was flying at trainer aircraft speed at full throttle.
When we landed, his motor was overheated while my was barely warm.
How is it possible? The reason is in the airframe.
The Spad has a very good airfoil almost reaching ideal with both tapered cord both thickness and widthwise. This mades the SPAD inteceptor low drag so it can fly at speed. At speed, the propeller unloading takes into effect drawing a lot less current .

My friend Depron DIY SU27 has little or no airfoil...almost flat . The Lamina airflow will not flow smoothly over the airframe hence creating a high drag situation.

After the incident I built another SPAD interceptor and transfer his electronics motor that was on his Su27 to the newly built ,28 inches wingspan SPAD and now he is happy with the performance.No overheating, plane flies with generous speed.( He does not want to try the 24inches wing span SPAD interceptor because the speed scares him)


Therefore , if you are using small propeller and running at high rpm, you need a low drag airframe. It will run more efficient.

watch this early experimental SPAD

Scratch build corroplast (Spad ) radio control aircraft crash before succes

You can forward the video time line to 2.40 , The plane is very fast

if the plane moves 44.4 Meters in one seconds , this will translate to 100MPH.


Cheers and hope you have fun with small propeller setup.

[quorneng]

Here we go with a longer 'ductless' flight unfortunately terminated a bit early as one cell of the LiPo failed.

YouTube Video

so far I can't really detect any difference in performance duct on or off!
More testing once the new battery arrives.

[mclarkson]

Cool. That's somewhat surprising, but that's why we do tests.

[Bill G]

Quorneng I'm not surprised that the fan blade performs as well without the duct at the flying speed it is at. My FW190 TL would probably be just as fast with a 70mm prop sticking out of the front of it. It would look pretty silly that way though.

Originally Posted by babylon5

watch this early experimental SPAD

Scratch build corroplast (Spad ) radio control aircraft crash before succes

You can forward the video time line to 2.40 , The plane is very fast

if the plane moves 44.4 Meters in one seconds , this will translate to 100MPH.


Cheers and hope you have fun with small propeller setup.

Go back and look at the launch of my small prop Savoia S64 video. It was almost as difficult to get the initial hang of it, as your SPAD was. Very responsive.
The FW190TL I showed has an Align motor also. It's a 430L. I'm convinced it should hold up on 4s, as it doesn't warm much on 3s. I may try it with 4cells for more speed.