No but we ARE talking about a high blade count CS10 in this thread. All others are irrelevant.
So it is unimportant that Stu's does better, or not.
The comparisons are ANY other fan TO a CS10. And it is less efficient when compared against any other low blade count fan - even cheap Haoye.
But it is still quieter..... which is its main claim to fame really.

"All others are irrelevant." .... "The comparisons are ANY other fan TO a CS10"

So are we comparing to others, or just making broad overgeneralisations?

A 3 blader doing 1.2kg off 1.2kw. http://www.rcgroups.com/forums/showthread.php?t=1284782

Good design is the key, not the number of blades.

Comparisons are only TO the CS10.
There are enough tests/comparisons of GOOD low blade count fans to already show the CS10 is 'sub standard'..... below typical. Not massively, but enough to call 'costly' (eg 5% to 10%). And it pretty well has to be due to design, so that is nothing amazing to find out - but it is also irrelevant as it is what it is and we are comparing to that. Not worried about why, seeing you can't do anything about that part anyway.

That 3 blader you listed wasn't much use as an example, the fan itself is actually fine - I have one. (bound to be the exact same 3 blade Wemo clone). That thread just has someone running it with a bad setup. He doesn't list anywhere near enough information to know exactly what is wrong, but is is badly amiss. Then later he says 'yeah it is hot'..... DERR. Still need numbers to work out exactly what is wrong, but that is the big clue.

I don't think I have had a 'bad' low blade count fan.... which the reference for them is the CS10, which they are all better than, in thrust per power terms. (all mine and tested ones).

I am new to this forum but have just purchased several of the CS-10 units to experiment with using different motor & lipo combinations. I admit I bought these purely for the addictive sound. So far using 2 different 5s setups on both a Turnigy 2350kv outrunner & a NTM prop drive 2200kv have shown around 950- 1050 watts on the power analyser but have given slack performance in the 2 jets I have used them in (Durafly Vampire & Lander Panther)
I have also tried the recommended Turnigy 2855 2800kv motor & another 2750kv motor that came stock with the Vampire on 4s with similar slack performance. I haven't yet tried the higher kv motors on 5s for fear of burning out the motors.
The 2350kv Turnigy burnt out after 3 flights on 5s in spite of its lacklustre performance. As soon as I went back to a 5 blade impellor on 5s the performance jumped back to where it should be.
My conclusion so far is that the 10 blade impellors are far less efficient than their lesser bladed cousins.

well this should stir the pot again

Originally Posted by warbirdzfan

I have also tried the recommended Turnigy 2855 2800kv motor & another 2750kv motor that came stock with the Vampire on 4s with similar slack performance.

Depends how you baseline slack performance I guess.....

Would you also call the performance in these 2 videos slack?

Durafly DH100 Vampire (1 min 42 sec)

RC Lander Panther F9F-2 CS10 5S (2 min 0 sec)

warbirdzfan....
The 2350kv 5S should have done better in the plane than you appear to have got. The Watts (950W or so.. in-plane I assume?) are plenty. There are plenty of 5S CS10 2300kv's setups in Vampires that are posted to show it works fine, normally. And the Lander Panther is a very similar total aircraft package to the Vampire too.
So something is amiss there and doesn't really add up - as far as flying... while it lasted.
I have tested one of those 2836 motors and they don't like to run over about 800W.... thus probably why yours fried.
A 5S 2200kv (NTM) would be weaker, more like 800W - due to the kv. I also have one of those I tested and they are also a bit weak. Again 800w or so is stressing it a lot.

So you had two motors that are a bit weak. But should still have worked ok, till they fry. hehe.
If you got the Watts, they should have been operating fine in flight terms.
I can't think of a reason they did not.

Then for 4S... I don't like it at all anyway! LOL
But if you got adequate Watts (700W ?? or more) then they should have worked fine too.

Don't show videos, as they are half useless. They make a plane's speed look 1.5x faster than it is..... with X variation according to FOV of the camera.
So unless someone has a video of theirs to compare to another video, it is not much of a reference. And even to do that is just a poor way to do comparisons.

Best would be quote a top level flight speed. Pretty well all other aspects of the flight ability must then match too. For a same/similar AUW plane of that same type.

It is nice to see videos, but as measurement references they are misleading.
Just AUW's..... Watts..... is almost enough to know for that same plane type. But throw in the TRUE top speed and that helps narrow thing a bit more.

Originally Posted by PeterVRC

warbirdzfan....
The 2350kv 5S should have done better in the plane than you appear to have got. The Watts (950W or so.. in-plane I assume?) are plenty. There are plenty of 5S CS10 2300kv's setups in Vampires that are posted to show it works fine, normally. And the Lander Panther is a very similar total aircraft package to the Vampire too.
So something is amiss there and doesn't really add up - as far as flying... while it lasted.
I have tested one of those 2836 motors and they don't like to run over about 800W.... thus probably why yours fried.
A 5S 2200kv (NTM) would be weaker, more like 800W - due to the kv. I also have one of those I tested and they are also a bit weak. Again 800w or so is stressing it a lot.

So you had two motors that are a bit weak. But should still have worked ok, till they fry. hehe.
If you got the Watts, they should have been operating fine in flight terms.
I can't think of a reason they did not.

Then for 4S... I don't like it at all anyway! LOL
But if you got adequate Watts (700W ?? or more) then they should have worked fine too.

The 2350kv motor on 5s I trialled in my Panther which I hand launch. It flew but needed full power on the launch & was noticeably slower than the previous 5s setup I used which was a 2750kv with a 5 blade impellor. I have also flown the same plane with the CS-10 using that same 2750kv motor on 4s. Still felt much slower than the original original 5s 5 blade setup.
I'm not seeking to rubbish the CS-10 unit. I want to continue to experiment & find the best motor combination for it either 4 or 5s. I love the sound of it.
Certainly my reference to "slack performance" was compared to 5 blade fan setups. The watts being pulled as per the power analyser come up as similar but the performance (or thrust) seems less on the multi blade unit for some reason. It is purely a seat of the pants comparison on my part as I don't have thrust or speed measuring equipment.
Am I correct in assuming that watts don't always equate directly to thrust? Isn't it possible that the 4, 5 & 6 bladed fans are more efficient therefore pull less watts for a given amount of thrust:

In the SAME fan they Watts will equate quite closely to thrust.... only useful for direct comparison if used in the same situation. eg bench, same plane etc.
Then there is a bit of variation over motor, wiring, ESC etc. but as long as things are/were done within some sensible reason the outcomes are not too far astray.
So you can fairly safely say 1000w is 1000w.... just allow a bit of tolerance leeway.

Your outline has too many 'grey perceptions' rather than specific values, to really pin down much. You have to test and write things down - be detailed and have all the needed factors/values. Even one important one missing, or erroneous, can mess up an analysis.

how many times do we have to discuss this...

maybe the arguments get shorter if we remember two things:

- the CS high-blade fans are a only a little bit less efficient than the low blade fans only IF

- they are getting good airflow IN, and

- the exhaust are not too small, e.g., in case of the CS70, not below 58-59mm. Bifurcated exhaust usually cause a further drop in efficiency.

if you haven't already, watch this

http://www.youtube.com/watch?feature...&v=qLuydmx9xWs

Both requirements are fulfilled in bench tests (with inlet lip providing good inflow!), results will be worse in a real model, how much worse depends on the inlet diameter, exhaust diameter, and if it's smooth or a bifurcated exhaust causing reflexions etc.

Taking the examples of the Vampire & Panther in turn: For higher power in the HK Vampire, the CS70 is not getting enough air IN (exhaust more than large enough), several mods described in the Vampire thread; in the Lander Panther, there is both not enough air IN (especially with bottom cheater closed), and the stock exhaust (56mm) is too small for the CS70 to work properly. With several kW however even badly setup CS70 will perform, as many videos testify. Efficiency is a different matter.

Bottom line: If you want your cheap high-bladers to perform you have to work out how to get the air in and out efficiently, Not easily possible with all airframes, but if you want a quiet fan and not a howler you have to invest some thought and do some modding (in many cases).

Is there more to it than that?

Thanks for that explanation Mopetista. I am fairly new to edfs & haven't had the chance to go through the entire 393 pages of posts on the CS-10. It goes a long way to explaining why the CS-10 is underperforming for me in these 2 planes compared to previous 5 blade fan installations as I have done no modifications at all to improve airflow. Would you recommend some sort of exhaust thrust tube to improve airflow in the Vampire if it allowed the optimum 63mm diameter to be maintained as per the youtube test data?

Various mods and discussions about how to make the CS70 perform in those airframes can be found in the respective threads.
Since my Panther is still in the build phase (but I am going to do top/side cheaters as discussed in the Panther thread recently, including pics) and my ultralight 3s 400W Vampire performs great (since the fan doesn't need so much air at that power level, and for my taste 60mph is enough on my Vampire flying in a tight space) I cannot provide any first hand experience what opening the cheaters more or the canopy hole mod might bring, neither have I tried a thrust tube...

That's really interesting, I wonder if my Phantom wasn't getting enough air in.

Pressumably if air-in is being restricted the power would be less than you might expect?

Andy

But if you quote WATTS when in the plane then that tells the airflow story too.
eg If it was 800W on the bench and 600W in the plane = airflow resistance.

Warbirz didn't specify, but is sounded like he was saying IN the plane - which I doubt as it does not add up mathematically.