EDF 3 Blades or 4 Blades?

[mirage2k]

Hi everyone. I am new to EDF and have tested under a layman concept of the 3 blade fan and a 4 blade fan. Need help & assistance / comments

I have the followings:

1) 3 blade fan & 4 blade fan with the same pitch
2) BL motor 4400KV with efficiency of 85%
3) 2650mah 30C 3s lipo

1st setup
------------
4 blade fan with BL motor. When i hold the fan unit in my hands, full throttle and it shoots up 30cm away from ground. 2.30mins max to 3.65V

2nd setup
------------
3 blade fan with BL motor. When i hold the fan in my hands, full throttle and it barely lift up, perhaps 10cm from ground. 3.00mins max to 3.65V

Though the lift is not as great as the other setup, i am still able to feel the pressure & wind powerfully generated. But looking on other threads in the forum, the one under 6 blades to 3 blades convertion, isnt the 3 blades setup supposed to bring my plane to a higher speed?

Does the 4 blades setup = more torque = more speed = more static trust= more acceleration?

Static trust
------------

If my plane weights in total of 600g.
3 blade static thrust = 700g. = 100g more than the plane
4 blade static thrust = 900g. = 300g more than the plane

which will make my plane faster? or i can just ignore the additional more grams as long it covers or equals to the plane weight?

Please help. Deaply appreciation for any replies post on thread.

Cheers

[Babylon5]

Hi Mirage2K, using a 4050Kv motor on the 3blade and 4 blade is not a good way to compare. Obviously the 4blade will load the motor than the 3blade and produce more static thrust.


In my experiment I use a 6 blade with a 3055KV motor than check the power and current.
I cut down the 6blade to 3 blade by removing 3 alternate blade and use it with a 4050KV motor.

It appear that both setup uses about the same power .
I tested both setup on the same aircraft.
The aircraft with 3 blade fly noticeable faster at level flight.
You can do a search on the internet. Lots of flyer does this experiment too.

Although higher blade count arrangement EDF generate more static thrust ,it does not necessary translate to higher flying speed.
Depend on your preferences higher static thrust setup or higher flying speed.
Some may not agree.
There a lot of debate on this issues.
Go to the internet to do a search on 3blade versus 6blade or higher blade count EDF.

Cheers and all the best.

[mirage2k]

thanks for your advice on your experiment. by the way i am having a motor of 4400kv not 4050kv.

any other ones for advice?

cheers.

[viper1990]

Higher thrust is not equals to higher speed.
There are 2 main things you should take note about EDF. Thrust and Pitch speed.

Thrust mainly is like a gear one on a car, you accelerate fast but you won't achieve top speed.

Higher pitch speed is to acheive top speed, just like you will need gear five on the car. Lower torque (low thrust) but higher speed.

Example:
Plane A has 300grams of thrust, 100km/h pitch speed.
Plane B has 600grams of thrust, 50km/h pitch speed.
Both planes has the same weight.

Plane A will definatly travel faster than plane B , but Plane A will need a way longer runway to accelerate to flying speed.

Next is you don't need 1:1 thrust ratio for a plane to fly. EDF planes can even have 0.5:1 thrust ratio to get it up flying, but you'll need a more powerful hand launch,bungee. (But of course,more power the better right? )

Ok, so to anwser your question, i do not have enough infomation to determine which of your edf will make your plane go faster. It base on KV, pitch speed of each blade, number of blades , how your duct is designed , air exit area, air intake area.

But if i give a good guess...i'd say the one with 3 blades running on 4400kv

Some extra info to help you.

[edmond22]

Hi Mirage2K, using a 4050Kv motor on the 3blade and 4 blade is not a good way to compare. Obviously the 4blade will load the motor than the 3blade and produce more static thrust.


In my experiment I use a 6 blade with a 3055KV motor than check the power and current.
I cut down the 6blade to 3 blade by removing 3 alternate blade and use it with a 4050KV motor.

It appear that both setup uses about the same power .
I tested both setup on the same aircraft.
The aircraft with 3 blade fly noticeable faster at level flight.
You can do a search on the internet. Lots of flyer does this experiment too.

Although higher blade count arrangement EDF generate more static thrust ,it does not necessary translate to higher flying speed.
Depend on your preferences higher static thrust setup or higher flying speed.
Some may not agree.
There a lot of debate on this issues.
Go to the internet to do a search on 3blade versus 6blade or higher blade count EDF.

Cheers and all the best.

So did you reach supersonic speed with 1 blade?

If anything at all, a complete myth not worth mentioning at all. What you have done is resolved poor edf efficiency due to bad design or power setup. You have only restored what it is truly capable of, definitely not realise any new invention or miraculous increase in efficiency.

Just buy a better fan and power combo that works.

[Babylon5]

So did you reach supersonic speed with 1 blade?

If anything at all, a complete myth not worth mentioning at all. What you have done is resolved poor edf efficiency due to bad design or power setup. You have only restored what it is truly capable of, definitely not realise any new invention or miraculous increase in efficiency.

Just buy a better fan and power combo that works.

Well said, if you have plenty of cash by all means buy the best EDF money can offer...then again who is to judge if the EDF it is a poor design.
If it is poor in design so what. Question is ,can it be modified it to make it run better?
Personally I just like take something ordinary and modified to make it runs better.


But there are people who like to try out or curious to find out for the fact. I must say I admire people who like to experiment and do something challenging.


I must admire Mirage2K for wanting to learn more.


cheers

[edmond22]

Well said, if you have plenty of cash by all means buy the best EDF money can offer...then again who is to judge if the EDF it is a poor design.
If it is poor in design so what. Question is ,can it be modified it to make it run better?
Personally I just like take something ordinary and modified to make it runs better.


But there are people who like to try out or curious to find out for the fact. I must say I admire people who like to experiment and do something challenging.


I must admire Mirage2K for wanting to learn more.


cheers

I very much agree with you, there are some who are SMARTER and buy it right the first time round too. They do experiments too, and reach new frontiers with proven video records and proper scientific software analysis. Unlike some, a lot of troll posts under different nicks dragging the same old shit story is not called learning, that is called stubborn.

Think before you decide to drag this further. Better yet, post videos you claimed years ago that never materialise here and on RCgroups. Dun even try to pass Wemotec or HET fans as expensive, they are considered inexpensive already. If you think they are not worth their price, that is a personal thing and opinion, a lot of us here and in rcgroups dun have to agree with you as evidenced by its prevailing popularity not only on youtube but on the Internet generally. Just give me a break and give this story a end, why rehash it every 6 months telling people that cut down blade theory works?!?

TS: nothing against your thread or you, just do not want you to go wasting time experimenting on something that is already well debunked to be a myth here. I am just sick of hearing the same story of going supersonic on a cut down 1 blade theory that was never backed up by any videos or data analysis.

Read this, 2006 till now, we are going into 2010 soon! And still this....

http://www.rcgroups.com/forums/showthread.php?t=557209

[Babylon5]

I very much agree with you, there are some who are SMARTER and buy it right the first time round too. They do experiments too, and reach new frontiers with proven video records and proper scientific software analysis. Unlike some, a lot of troll posts under different nicks dragging the same old shit story is not called learning, that is called stubborn.

Think before you decide to drag this further. Better yet, post videos you claimed years ago that never materialise here and on RCgroups. Dun even try to pass Wemotec or HET fans as expensive, they are considered inexpensive already. If you think they are not worth their price, that is a personal thing and opinion, a lot of us here and in rcgroups dun have to agree with you as evidenced by its prevailing popularity not only on youtube but on the Internet generally. Just give me a break and give this story a end, why rehash it every 6 months telling people that cut down blade theory works?!?

TS: nothing against your thread or you, just do not want you to go wasting time experimenting on something that is already well debunked to be a myth here. I am just sick of hearing the same story of going supersonic on a cut down 1 blade theory that was never backed up by any videos or data analysis.

Very interesting reply.
If you think that it is a waste of time in the experiment then why bother to join in this forum?
If you like to debunk or debate so much you should join the debating society.
And I realy sick of listening to you your sacasm. You can take your sacasm elsewhere.

[edmond22]

Very interesting reply.
If you think that it is a waste of time in the experiment then why bother to join in this forum?
If you like to debunk or debate so much you should join the debating society.
And I realy sick of listening to you your sacasm. You can take your sacasm elsewhere.

I never say it is a waste of time to experiment. I SAID your theory is a waste of time.

I have no interest on your opinion about joining whatever society, you can create a mass delusional blade cutting fan club (you have been trying for years actually, how many followers?) for all I care.

Finally, this accusation of sarcasm is amusing at best. You attempted to do just that and because you suck at it doesn't mean you can turn around, act innocent and start kicking your legs on the ground crying foul.

I will only have this to say to you only, THE SAME as what others in RCgroups asked of you too:

- PROVE your theory with evidence like video or doppler analysis
- Then come back and talk
- If not, just let that theory drop dead

I am not going anywhere, you know it, So.... be prepared for more.

[fuse]

guys cool down. Cut or dont cut is up to each person. Andrew is the edf guru and had many experience in fans. Just that some work some dont work. Anyway edf is a dark art. Till today my m2000 is still hanging on the wall hehhehe. Lets move on..

Ed lets fly our motor glider la, leave edf alone. Unless u wanna try, u can have my m2000.

[mirage2k]

hi viper, i really appreciate your info, it had helped me to understand finally how it works though the graph is to vague to me.

cheers

[mirage2k]

from edmund22

''did you reach supersonic speed with 1 blade?

If anything at all, a complete myth not worth mentioning at all. What you have done is resolved poor edf efficiency due to bad design or power setup. You have only restored what it is truly capable of, definitely not realise any new invention or miraculous increase in efficiency.

Just buy a better fan and power combo that works.''

it seams you cant define 'better fan & power combo'

if it is easily defined, then such test will not have even persists. hobby shops will then sell one type of fan and one type of motor only.

[mirage2k]

edmund22, i am new to edf and dont understand. i dont even understand the forum's thread discussed earlier. that is y i have one post here. if i would have understood, i would have not wasted time typing here. i would have save my time to sleep. i didnt even cut blades to do tests, i went to purchase 2 type of fan thats all.

edmund22, i understand that you have done well understanding the techinical engineering etc of the edf fan. but u cant expect people to understand like you did. if you dont wish to help i cant do anything too, but do not comment we are stubborn. makes no sense ya?

no one wants thier jet plane to hand luanch and dive down or to see thier plane to fly like plaing rc kite. i am not wanting more or wanting to acheive the best of edf, at least a can do 70%. my plane fan unit cannot be removed once mounted, thats y i test first. nothing wrong.

[mirage2k]

edmund22 - 'I very much agree with you, there are some who are SMARTER and buy it right the first time round too. They do experiments too, and reach new frontiers with proven video records and proper scientific software analysis. Unlike some, a lot of troll posts under different nicks dragging the same old shit story is not called learning, that is called stubborn.'

where got people buy first time right one? and not everyone can have software analysis at home to do experiments. can i ask have you tested? or you went to buy a fan ONCE and got it right? if so i think you are really LUCKY.

[mirage2k]

CAN YOU PLEASE READ MY POST BEFORE COMMENTS????????? eeeeeedmond?