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Author Topic: Considering building my first EDF R/C, question:  (Read 673 times)
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Starduster
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« on: February 12, 2013, 10:21:26 AM »

I am looking at Dave Rees' Bell X-5:

http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=4636&mode=search

He calls for a "Red Flame Blaster" for the EDF.

As far as I can tell, this unit is no longer available (no surprise as the plan was drawn in 1997).

What would be a good modern substitute?

TIA

Rich
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Konrad
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« Reply #1 on: February 13, 2013, 11:48:50 PM »

The Blaster was a brushed Speed 400 sized 63mm(?) fan on 7 500 mAh round nicad cells drawing about 70 watts.
 As to a modern fan I would look for one that had the same diameter or one that has no less that 80% of the swept area of the one shown on the plans.

Todays fans are (or should be) much stiffer and should be able to run at a much higher RPM. I would try to size the motor to run on 3 lipo cells of 450 to 800 mAh capacity. With lipos you can make a substantially lighter ship if you can move the equipment around to maintain the CoG.

I think I have a Blaster back home in San Francisco I might be able to measure specs from the next time I back home. I will say I've tried some GWS fans and have had problems with fan (impeller) growth as I tried to harness the power from todays modern brushless systems.


I found that the Rojet fans I was using in my Avitar are in the same class but ran on 12v. I liked the stiffer impeller. With 3 cell lipos this might also be an option but it is not modern!

All the best,
Konrad


P.S. I seem to recall that the Blasters ran around 11k rpm. Modern fans are driven past 30K rpm. I hope you can see the need for a much stiffer impeller. I also hope you can see where the vast improvement in performance comes from!
« Last Edit: February 14, 2013, 12:13:04 AM by Konrad » Logged

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Konrad
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« Reply #2 on: February 25, 2013, 08:01:46 AM »

I've been hearing good things about these.
http://www.donsrc.com/cart/
You might need to upgrade the wings for the power and weight of the batteries.

The Wemotek 50mm with some other less powerful motors might actually work well.
http://www.maxxprod.com/mpi/mpi-267.html
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Bill G
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« Reply #3 on: March 07, 2013, 11:27:59 PM »

I built a similar design, which is the FW250 using a Don's Wicked and EDF64 on 3s-1800 lipo.  Off top of head it is around 16oz AUW and 28" span.  The model uses a GWS 109 replacement wing, which is similar to an Eppler E226 and is one f my best flying models.  Always like the Bell X-5 and I've looked at this plan a number of times.  Should be an interesting project for you.
 I built a somewhat similar airframe Yak23 that had a pitch up problem, where the solution proved to be adding a short duct exit extension which moved the exit slightly away from the fuse bottom, such as on the Bell X-5.  I would definitely maintain the small distance between the top of the duct exit and the fuse bottom.
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Re: Considering building my first EDF R/C, question:
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Konrad
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« Reply #4 on: March 09, 2013, 10:24:27 AM »

Iceman,
I'll be back home in SF later this month. If you want I can look for my Red Blaster (I think I know where it is). I'd be happy to send it to you if you think you would use it. I think on 2cell 480mAh (maybe even 3 cells with a well broken in set of brushes) she should give you adequate performance in the light Reese ship.

Bill,
I have a Aero Graphics FF Hawker Hunter @20" span. I'd like to try to convert it to R/C. The plans show a small 44mm KP fan unit. Are you aware of a more modern (read powerful) fan unit that is this small? I might be able to fit a 50mm Wemotec fan but these are very powerful at 280 to 430 watts. And the supporting batteries might be too heavy for the small 20" wing.

All the best,
Konrad
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Bill G
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« Reply #5 on: March 10, 2013, 06:07:08 PM »

Iceman,
I'll be back home in SF later this month. If you want I can look for my Red Blaster (I think I know where it is). I'd be happy to send it to you if you think you would use it. I think on 2cell 480mAh (maybe even 3 cells with a well broken in set of brushes) she should give you adequate performance in the light Reese ship.

Bill,
I have a Aero Graphics FF Hawker Hunter @20" span. I'd like to try to convert it to R/C. The plans show a small 44mm KP fan unit. Are you aware of a more modern (read powerful) fan unit that is this small? I might be able to fit a 50mm Wemotec fan but these are very powerful at 280 to 430 watts. And the supporting batteries might be too heavy for the small 20" wing.

All the best,
Konrad
I haven't kept up with all these new, pre-motored fan units.  I still would prefer the light weigh of the 12mm Feigao in an EDF40 fan, although the motors are difficult to find today.  The newer outrunner powered setups such as the ELE fans are supposedly more powerful, but the lightweight Feigao can run on a lighter battery at higher efficiency than the outrunner powered setups.  The two approximately 20" EDF30 5866kv Feigao jets I have will fly on a older 22gm 3s-300 with lower C rating than the newer batteries.  I guess if I were to build one today, I would probably use one of the 40mm ELE units however, as they are inexpensive and available. 
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Konrad
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« Reply #6 on: March 14, 2013, 07:05:27 PM »

Thanks Bill.
I have a lot of 12mm motors from various manufactures. I think Neu Motors markets one modeled off the Medusa brand, I think I'd like the 2mm shaft.
http://www.neumotors.com/store/page8/page8.html

EDF40: Is this the GWS unit? If so I've had issues with blade stretch. Has GWS or some other supplier made a stiff impeller for the unit? Can you direct me to the ELE fan?

I have a Feigao 7200kv motor. Would the impeller in the GWS EDF30 hold up to this motor on 2 cells?
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