Which Ducted fan plane to recommend?

[Crabby]

Hi guys..
Is there any ducted fan unit & plane that consume very little power & fly well? Like the DF electrajet??? Coz I am looking for a DF unit+fan that onie require me to use a 1800mah 20C discharge lipo. If there is, what is the setup like??? Thankz as I do not wish to charge up two battery pack juz for one flt... & also at the same time looking for a power efficient airplane...


Happy FlyingZzz

[ER69]

Hi guys..
Is there any ducted fan unit & plane that consume very little power & fly well? Like the DF electrajet??? Coz I am looking for a DF unit+fan that onie require me to use a 1800mah 20C discharge lipo. If there is, what is the setup like??? Thankz as I do not wish to charge up two battery pack juz for one flt... & also at the same time looking for a power efficient airplane...


Happy FlyingZzz

Yo Crabby,

Perhaps you can consider of making those profile planes something like wat Zenith's or babylon had built. They are for 50-55mm fan and profile plane has totally no worries on ducting issue Simple and nice for a start..
But dont expect it to fly as fast as your Align Sports Glider
Anyway, there are two kind of set up which you might like to know.
1. High amp/ low current or
2. Low amp / high current

Cheers
Catch up with you soon....

[Invisible Angel]

Is flying F16 ducted fan more advisable for beginner ducted or
SU27-Flanker?

Which is better?

Is it advisable to go brushless for first timer on ducted?

Thanks

[Warbird]

I think the SU-27 will be better for you. The F-16's usually need a lot of power due to the complicated and small intake ducting. A SU-27 is much much easier build as it has more or less straight intake ducting. Means with the same power setup you will get most likely more thrust from the SU-27.

Go brushless. Unless the plane is really really light a brush motor will not bring proper performance (especially in this climate). As you WILL get hooked on EDF (we all are ) your brushless investment will not be wasted as you will get a bigger plane very very soon

BTW, are you keen in building kit planes (balsa)?

[Invisible Angel]

SU27 ducted

Thanks for the advice.

I just got myself the SU27 Flanker from JetHobby.

Will invest in brushless in the coming months as I won't be flying the plane yet.

Look forward to flying with all ducted flyers soon.

[Babylon5]

EDF stuff

For the Electra jet, I have seen some flyer flying the Tahmazo Motor and fan unit(60mm dia EDF) on this jet at around 16Amps or 3 cells lipo.
Flight is moderate.

Would be more spirited flight with the 68mm fan on 3.3 to 3.5KV speed 400 size brushless but current goes up to over 20amps , you need 2200maH at least 10C with this set up.

Try Align 430L 3.55KV on the 68mm EDF available at Jet Hobby and a 10C 2200maH 3 cells packs.
Flight is about 4-5 minutes with this setup and motor run hot so limit max power to 30 seconds or less flight.

If you want lower power and longer flight, use the 55mm EDF with 3.3KV -3.8KV motor 20D-40L series with 2mm shaft.(D= diameter L= length)
Can have 7min flight on 8C 1800maH and a smaller Jet plane with a wing area of 200 to 250 sq in . Don't know any plane but a modified Micro Jet for EDF is possible with this setup

Cheers
Babylon5

Hi guys..
Is there any ducted fan unit & plane that consume very little power & fly well? Like the DF electrajet??? Coz I am looking for a DF unit+fan that onie require me to use a 1800mah 20C discharge lipo. If there is, what is the setup like??? Thankz as I do not wish to charge up two battery pack juz for one flt... & also at the same time looking for a power efficient airplane...


Happy FlyingZzz

[Crabby]

For the Electra jet, I have seen some flyer flying the Tahmazo Motor and fan unit(60mm dia EDF) on this jet at around 16Amps or 3 cells lipo.
Flight is moderate.

Would be more spirited flight with the 68mm fan on 3.3 to 3.5KV speed 400 size brushless but current goes up to over 20amps , you need 2200maH at least 10C with this set up.

Try Align 430L 3.55KV on the 68mm EDF available at Jet Hobby and a 10C 2200maH 3 cells packs.
Flight is about 4-5 minutes with this setup and motor run hot so limit max power to 30 seconds or less flight.

If you want lower power and longer flight, use the 55mm EDF with 3.3KV -3.8KV motor 20D-40L series with 2mm shaft.(D= diameter L= length)
Can have 7min flight on 8C 1800maH and a smaller Jet plane with a wing area of 200 to 250 sq in . Don't know any plane but a modified Micro Jet for EDF is possible with this setup

Cheers
Babylon5

YO Babylon5,
Thankz for the recommendation... think some of them are good references... However the flt time u mentioned is abit short...so... perhaps I'll have to stuck with my Align Glider for awhile... As for the speed I dun think it is fast enuff as some VIP pylon racers I've seen. Ah Boon flies very well too So sad that my VIP R.I.P now. Else can ask Edmund, YZY & we have a mini plyon race. Kelvin has one rite? Never seen him fly leh... How Kelvin???

[Unorthodox_Sniper]

YO Babylon5,
Thankz for the recommendation... think some of them are good references... However the flt time u mentioned is abit short...so... perhaps I'll have to stuck with my Align Glider for awhile... As for the speed I dun think it is fast enuff as some VIP pylon racers I've seen. Ah Boon flies very well too So sad that my VIP R.I.P now. Else can ask Edmund, YZY & we have a mini plyon race. Kelvin has one rite? Never seen him fly leh... How Kelvin???

Hi Jason,

The Align speed glider can be very fast but you must reinforce the wing as it will flex if you pull at that speed. I reinforced both sides of the wing with CF rod & CF strip. We have tried mega 16/15/4 & warp 3T in it and the speed is very good & with a good spinner & prop it flies very quiet & you can hear the swoosh sound I can show you when we meet up. Kelvin is building a new speed glider now hehe.

I brought in a few sokol and according to Ah Boon it flies better than VIP & has a nice whistle sound that the VIP doesn't have but the sokol is a floater so landing is very hot & more difficult than VIP. The Dynamic 400 is another good pylon, I'll be bringing in a few direct from manufacturer in a month's time

[Babylon5]

Small EDF setup

Hi, if you are using 1800maH 3 cells and want to have longer flight than go for the 55-60 EDF and the Himax 2025-40 ,3.2KV up to 3.8KV or equivalent.
Most 55-60 mm EDF uses the 2.0mm shaft only so check your EDF and motor first.


For first time budget entry ,try at Jet hobby 55mm EDF .
My EDF with the jet hobby 55mm edf runs on 3 cells 1800mah pack takes only 13amps with a 3.2KV Himax equivalent 2025-3.2KV giving me 7minutes full power flight with plenty of reserve left.
Thrust exceeding 450gms
With only 13 amps a 8C packs will do. Cannot tell difference in performance between 8C and 10C Lipo packs.

Don't go higher than 3.8Kv because you are likely to exceed max current rating of the motor with this size of EDF(max curent of the 2025 size motor is around 16amps with a few exception.)

For models, you can do a profile jet with a wing area of 200 to 250 sq in.
Will fly great.


Once you get the hang of it and wants to go for higher performance than go for Wemotec and better graded and more powerful motor like Hackers, Het ,Mega motors and Astro Brushless motor. Ace Hobby has a few selection of Wemotec Fan and motors.

Happy flying and
Hope this will help you.

Babylon5

Hi guys..
Is there any ducted fan unit & plane that consume very little power & fly well? Like the DF electrajet??? Coz I am looking for a DF unit+fan that onie require me to use a 1800mah 20C discharge lipo. If there is, what is the setup like??? Thankz as I do not wish to charge up two battery pack juz for one flt... & also at the same time looking for a power efficient airplane...


Happy FlyingZzz

[DT8666]

For first time budget entry ,try at Jet hobby 55mm EDF .
My EDF with the jet hobby 55mm edf runs on 3 cells 1800mah pack takes only 13amps with a 3.2KV Himax equivalent 2025-3.2KV giving me 7minutes full power flight with plenty of reserve left.
Thrust exceeding 450gms


Babylon5

Hi, what do you recomend to replace the 60mm fan unit for the Alfa F86? I screwed that fan. now looking for replacement.

My AUW was 566g. so looking for something that can give me 1:1 trust! the MiniFan is 69mm so too big for this plane.

[Babylon5]

EDF Fan

Hi, how badly damage is the fan.
If you break a blade say if it is a 6blade, you can remove the other 2 and convert it to a 3 blade. There are some innovative guys who convert a 6blade to a 3blade and claim higher thrust and lower current consumption. How true ..not sure the claim. However you need higher KV motor to drive a 3 blade fan to get back the equivalent thrust.

If 69mm fan too big , try the 55mm EDF from Jet Hobby and use a 3.7KV Tahmazo motor Reno Class From SHS, u need the 2.3mm adaptor from GWS to fit the Tahmazo. It will run at 15-16 amps on 3 cell slipo and give you approx 500 gms of thrust. That 15-16 amp is also the max limit of the Tahmazo motor. Any higher KV will probably fry the motor.
You need a rimmer to rim out the 55mm fan carefully to fit this motor...a bit of work but worth the effort.

In addition, the 55mm EDf does not have a butterfly mounting so you have to glue the mounting your self. Need to sand the side of the fan, sandwitch with wood and 1.5mm ply and apply epoxy to the fan.

If you want to save the hassle just get the Tahmazo mtr and the 60mm fan unit from SHS ...quite Pricey

If you want more thrust than 500gms you need to go for Wemotec micro fan class and a better motor.

Cheears

Babylon5

Hi, what do you recomend to replace the 60mm fan unit for the Alfa F86? I screwed that fan. now looking for replacement.

My AUW was 566g. so looking for something that can give me 1:1 trust! the MiniFan is 69mm so too big for this plane.

[DT8666]

Micro fan only 50mm. seems too small to get a trust of close to 600g!

the stock fan is gone case. the motor mounitng housing MELTED!

May try to cut out the fuse of F86 and force fit in the mini fan and fit a 20W-3W?? and run with 4S!

Hi, how badly damage is the fan.
If you break a blade say if it is a 6blade, you can remove the other 2 and convert it to a 3 blade. There are some innovative guys who convert a 6blade to a 3blade and claim higher thrust and lower current consumption. How true ..not sure the claim. However you need higher KV motor to drive a 3 blade fan to get back the equivalent thrust.

If 69mm fan too big , try the 55mm EDF from Jet Hobby and use a 3.7KV Tahmazo motor Reno Class From SHS, u need the 2.3mm adaptor from GWS to fit the Tahmazo. It will run at 15-16 amps on 3 cell slipo and give you approx 500 gms of thrust. That 15-16 amp is also the max limit of the Tahmazo motor. Any higher KV will probably fry the motor.
You need a rimmer to rim out the 55mm fan carefully to fit this motor...a bit of work but worth the effort.

In addition, the 55mm EDf does not have a butterfly mounting so you have to glue the mounting your self. Need to sand the side of the fan, sandwitch with wood and 1.5mm ply and apply epoxy to the fan.

If you want to save the hassle just get the Tahmazo mtr and the 60mm fan unit from SHS ...quite Pricey

If you want more thrust than 500gms you need to go for Wemotec micro fan class and a better motor.

Cheears

Babylon5

[Warbird]

Hi Babylon,

The micro fan peaks at around 550grams with a very hot setup.
the 2025-5300 at 3S and the 2025-4200 at 4S generate around 440-470grams of thrust.

Hi DT8666,

You could try the micro fan with a 2025-4200 at 4S or a 2025-5300 on 3S but you would need to reduce your intake and exhaust ducting. A two big ducting will reduce efficiency the same way as a small ducting as the air flow is not laminar but very turbulent.

If you reduce your ducting down you can still use the same diameter at the intake but slowly and smoothly reduce it towards the fan (0.3mm foil could be used). The reduction angel should not exceed 10 degree to keep the airflow laminar.

Exhaust ducting should have the diameter of the fan at the fan and drop down to a 40mm diameter at the exhaust for best efficiency. Also here drop it gradually from fan -> exhaust

Last but not least make sure your intake has a nice round lip to increase the effective area (either sand the foam or use micro balloons and epoxy to shape and later sand).

Alternatively try to get either the replacement fan from Alfa or a similar sized fan from one of the hobby shops.
Try and add some cooling holes to the motor mount and reinforce the front plate with metal. You could also wrap the motor in a thin copper shield that extends out behind the motor to increase the cooling area. Together with the cooling holes this might be enough to keep the mount from melting.

Sorry that I can’t help with the right size of fan for the Alfa.

[joe yap]

Guys, don't go over zealous about this thrust thing. It's just the static thrust that you are measuring which only mean how fast the plane accelerate to it's terminal velocity. Lower thrust simply means that you'll just need a bungee to accelerate the plane to it's flying speed.

Dynamic thrust, which is proportional to the efflux ( exhaust ) velocity is the thing that makes the planes fly. To make a plane fly, the efflux velocity must be way above; the stall speed of the plane and to overcome the total drag of the plane. Once the fan reaches it's maximum efflux velocity, it'll not accelerate anymore, and if it's not enough to overcome the total airframe drag and the plane's stall speed, it'll never get off the ground.

The biggest mistake of most duct fan plane design, lies with the ducting, instead of the fan. The useful work done is only happened when the efflux velocity leaves the entire length of the exhaust duct, NOT THE FAN. All calculations should start with the fan sweep area, not the total area within the fan shroud, meaning the total area within the shroud at the fan station MINUS the area occupied by the spinner hub. Afterall, the air only enters through the fan, not including the spinner and motor.

Now, when the accelarated air leaves the fan, and reaches the back of the motor, the area suddenly increased as the shroud outer diameter never change! The area behind the motor becomes the vacuum and the air needs to quickly occupy it, causing drop in velocity. This is what happens if you leave the exhaust duct straight all the way to the exit. This is the same theory of gasses flowing through a venturi. As volume increases, velocity decreases. In short, you may be burning 40 amps to keep the fan running at high RPM, but in fact, 10-20 amps of it are used to produce noise. YOU ARE MAKING A VERY EXPENSIVE HAIR DRYER.

Using diameter and angle is just a very lay man rule of the thumb. In Bernoulli's theorem, we are assuming fluids ( including gasses ) are incompressible in subsonic speed, and thus, the air which left the fan must be kept as the same area from the fan to all the way to the exit, in order to keep the velocity constant. However, in practical, some losses will be incurred and thus, most designers will reduce the exit nozzle area at 80%-90% of the fan sweep area, especially for long exhaust ducts.

I hope you guys understand what I've said so far. OK. Ideally, the duct size should transit smoothly from the fan area all the way to the exit, paying attention to the 'area rule', that is if you were to section anywhere in the middle, the area of the section should be the same as the fan sweep area. As such, at no time the air inside the duct will have to expand or being compressed, which leads to changing in velocities and disrupting the airflow. A compromised way is to have a straight duct all the way till just before the nozzle cone, which will have the exit area reduced to achieve the above mentioned area.

The next issue lies on the air which passes behind the motor. If there is no fairing cone, the efflux air will form turbulence and changes in velocity and direction. For best efficiency, the air should travel throughthe duct as straight as as possible so that the reaction will be impinged in a single direction, producing maximum thrust. The same reason as you have to punch somebody straight in the face to inflict maximum damage. If you punch his face at an angle, you'll unlikely to cause as much damage.

The lip of the inlet is also important, which should be kept rounded in order not the disrupt the airflow. For best results, for single fan with split intake, the air on both intake should never meet until it reaches the fan. The spinner may have to be removed and replaced by the fixed fairing for smooth airflow transition.

Hope these help in same basic understanding but not burn you out.

Note that I did not use terms like turbulent and laminar airflow in this case as they have totally different meanings in terms of fluid dynamics. These terms are usually used to describe boundary airflow near the surface.

[joe yap]

These are some illustrations on exhaust duct design.