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Old Feb 24, 2009, 07:38 PM
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I asked this question earlier and didn't get a reply. But why is no one using the inlet ring? You are robbing yourself of power.

I'm sure it can be made to fit with some modification.
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Old Feb 24, 2009, 07:41 PM
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Quote:
Originally Posted by Buzz Bomb
I asked this question earlier and didn't get a reply. But why is no one using the inlet ring? You are robbing yourself of power.

I'm sure it can be made to fit with some modification.
I agree.
Old Feb 24, 2009, 07:43 PM
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Quote:
Originally Posted by AirX
The end result will be the airframe will only fly so fast on 1300 watts no matter what fan you use, because the force that 1300watts represents is ~6lbs in both fans so it will be the airframes drag that will ultimately let the plane fly faster or not. If you want to go faster without the added effect of an outlet tube then you will have to add more power.

Eric B.
I suppose if that is true than I should just make it easy on myself and use the 96mm fan as it is a drop-in fit and pretty cheap @ 29.00. I could probably still use a Mega 30/3 I have on 8s for 1300W.
Old Feb 24, 2009, 07:57 PM
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This is the case with any fan, if you want to change the dynamics all you need is either add power or change outlet dimenions to minimum of 85% as a gerneral rule as some fans can work with smaller percentage outlets providing the inlet can provide the air for the fan to process.

Eric B.
Old Feb 24, 2009, 08:00 PM
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I understand that choking down the exhaust will increase eflux.

What about the effect of RPMs on eflux? If the 90mm on 8s spins faster, say 34k compared to 32k, then . . . ?
Old Feb 24, 2009, 08:41 PM
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Quote:
Originally Posted by Socomon
I understand that choking down the exhaust will increase eflux.

What about the effect of RPMs on eflux? If the 90mm on 8s spins faster, say 34k compared to 32k, then . . . ?
Power is the only thing that means anything in fans, if you add more power you will move more air and efflux velocity will rise. Now for two similar fans and the same power in will move a similar ammount of air volume so changing the outlet size within reason will make velocity rise or fall depending on smaller area or larger area change. The power requirements change with the area change but only slightly.
To directly answer your question, to change rpm will take more power no matter what fan you have, but the difference in the FSA is minimal between the Himax and the Midi and both will be similar in performance with similar input power fan for fan barring any added features(outlet, inlet lip, etc).

Eric B.
Last edited by AirX; Feb 24, 2009 at 08:41 PM. Reason: spelling
Old Feb 24, 2009, 08:58 PM
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Then you are saying the Himax on 6s or Wemo on 8s will have essentially the same performance if both are getting 1300W in. The fan diameter and voltage differences won't make any meaningful difference.

Another question for the group at large:

The manual says to epoxy the front and back halves of the fuselage together (rather than just bot them together). It appears to me that the fan, motor, rotor, etc will no longer be removeable once that is done. Is that correct? If so, did everyone epoxy theirs together?

Steve

.
Last edited by Socomon; Feb 24, 2009 at 09:04 PM.
Old Feb 24, 2009, 09:04 PM
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I just bolted mine.

James
Old Feb 24, 2009, 09:09 PM
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I'm a lead farmer Mother ^%$^%
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Bolted
Old Feb 24, 2009, 09:10 PM
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Well, since your planes didn't fall from the sky, I guess I will bolt mine with some loctite too. I hate the thought of not being able to get the fan out.
Old Feb 24, 2009, 09:15 PM
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>Then you are saying the Himax on 6s or Wemo on 8s will have essentially the same performance if both are getting 1300W in. The fan diameter and voltage differences won't make any meaningful difference.<

Not in air moved(force being provided). If the motor used in either fan has decent efficiency then 1300watts in one will move the same ammount of air as in the other. 6mm difference is a very minimal change in area so the two are virtually the same. The Himax motor might be crap and in that case the midi with a Nue 1415 in it will be better. Someone posted numbers on the Himax for 6s, 7s and 8s. ON each test the Himax current went from acceptable to high and then to unacceptable for an average 36mm motor, the motor has its limits. Both fans are limited mainly by the motor/power being run thru them as CN and Carl have shown.

Eric B.
Last edited by AirX; Feb 24, 2009 at 09:18 PM. Reason: Added information
Old Feb 24, 2009, 09:45 PM
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Quote:
Originally Posted by Socomon
Well, since your planes didn't fall from the sky, I guess I will bolt mine with some loctite too. I hate the thought of not being able to get the fan out.
I also found it necessary to use a little threadlock on the landing gear bolts as they vibrated loose to the point of almost coming out of their socket during test run. Don't want them sucked into the fan.

James
Old Feb 24, 2009, 10:27 PM
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On yet another topic, I think a close look @ the manufacturer's picture is a bit telling about the nose gear. They have the spring all the way against the fuslage and they shortened the overall length by bending it back at a 45 degree angle above the wheel. Obviously they realized the nose had to be lower too.
Old Feb 24, 2009, 10:48 PM
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Good observation. Lowering the nose gear does help.
Old Feb 25, 2009, 07:28 AM
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Quote:
Originally Posted by AirX
>Then you are saying the Himax on 6s or Wemo on 8s will have essentially the same performance if both are getting 1300W in. The fan diameter and voltage differences won't make any meaningful difference.<

Not in air moved(force being provided). If the motor used in either fan has decent efficiency then 1300watts in one will move the same ammount of air as in the other. 6mm difference is a very minimal change in area so the two are virtually the same. The Himax motor might be crap and in that case the midi with a Nue 1415 in it will be better. Someone posted numbers on the Himax for 6s, 7s and 8s. ON each test the Himax current went from acceptable to high and then to unacceptable for an average 36mm motor, the motor has its limits. Both fans are limited mainly by the motor/power being run thru them as CN and Carl have shown.

Eric B.
Eric:

The other difference between the Himax and the Midi is the blade count. Himax has 4 blades and the Midi has 6, I believe. Is this of no effect either?

Steve


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