whatmovesyou
In evaluating the gap between the hub and blades, most of the lower end EDF's have a real wide gap. In a fluid mechanics course that I took, the larger the gap, the lower the efficiency of the EDF. This robs you of thrust and I looked for a way to reduce the gap and gain thrust.

I ended up using Scotch 3M magic tape as my solution. Here is how I did it.

1) Removed the impeller and used alcohol to clean the inside hub.
2) Using a Sharpie, wound Scotch tape at the end of the Sharpie pen until I had a little better that the circumference (C = 3.14 x Dia.) of the hub.
3) Make sure you cut the end of the tape perpendicular to the edge.
4) Very carefully place the start of the tape in front of one of the vanes.
5) Unroll tape from the Sharpie and place it in the same plane as you go around. Otherwise, the tape wrinkles and will probably hit the blades. Do it very slow and be precise. I used a very sharp knife and guesswork to cut the end so I wouldn't lap over the start of the tape. I practiced 5 times on a 3" tube before I felt comfortable to try it.
6) Make sure you still have a gap when you install the impeller back on. Remember, at high rpm's, the blades will grow and you still need clearance.

Okay, how do you tell if there is an increase in thrust. I have a JR PCM10x that shows the throttle setting from 0 - 100. Before the change, it hovered about 74% throttle in the cellar. After the tape was added, it hovered at 68%.
I am looking for an easier way to install the tape. Hope someone trys it and finds a better way
I like to design and fly unique planes.
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JettaManDan
most of the EDF's i've seen actually have the blades hitting the outside housing when new..no gap and an interfearance issue..and a steady low throttle break in is needed to trim the blades back and not let them interfear...if yours had a big gap then it would be the 1st i've heard of it needed soem more "meat" on the housing to close up the gap...

good idea..though if this is the case..

Dan
My YouTube Channel - 250+ Video's! http://www.youtube.com/jettamandan09

I'm an R/C Junkie! 40+ planes - 12 Heli's - 6 multirotors - and ground vehicles galore! I've got issues.
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all4smallrc
Great tip! Blade clearance is extremely important for maximum performance. And if you're trying to increase speed, add a thrust tube with an exit diameter of about 85% of the inside diameter of the fan itself. This may actually decrease static thrust, but it will increase the air velocity significantly, thus increasing speed. If thrust is what you want though, a thrust tube can still help by focusing the ouput airflow, but keep it the same diameter throughout instead of making it cone shaped.
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Argonath
I was looking at this and oddly enough, the 40mm EDF size is exactly the same diameter as a paper towel roll... Go figure...
D.I.L.L.I.G.A.F.
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DavePowers
Wow, a 6% increase aint bad. Worth it for planes where you really need it.

If you get a chance, can you post a pic or two of this mod.
Dave Powers
The Parts I Use
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Foam and Tape
Quote:
most of the EDF's i've seen actually have the blades hitting the outside housing when new..no gap and an interfearance issue..and a steady low throttle break in is needed to trim the blades back and not let them interfear...if yours had a big gap then it would be the 1st i've heard of it needed soem more "meat" on the housing to close up the gap...

good idea..though if this is the case..

Dan


, ive only seen that on some really Cheap EDF fans. The more expensive stuff I have in the EDF catagory has even spacing on the fan from the shroud.
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MoTheG
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ive only seen that on some really Cheap EDF fans. The more expensive stuff I have in the EDF catagory has even spacing on the fan from the shroud.

It may have to do with the materials you've used.
The cheap ones use plastic, but the expensive ones use carbon-fiber+epoxy.
Obviously there are differences in elasticity and abrasiveness.
This is another example of why it would be nice to get some info on the units. The faster you run the unit, the more space you need between the housing and the fan to allow for the fan's expansion. If you run the unit slower, it would be better to have less clearance.
If it can not fly with NiMH it is not a plane.
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LukeWarm
Some more info on the same subject: An EDF thrust tube
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whatmovesyou
Back in 2010, I found the gaps between the EDF blades and housing too much. So after doing some research, found that closing the gap adds thrust to the 64's. Over the year's, I have even added it to the 70 and even the 80 edf's. Out of about 10 different edf's, no failures, and in the worst case, I removed some of the tape by squeezing the housing by mistake. So if your EDF is crap in power, try it.
Can your 64 take off vertically by itself? Off a 45 degree table? The magic Scotch tape made it possible.

I redesigned Alpha Jet to go with a 64 taped EDF. Made it weighed with in 16 grams of the original. With my taped EDF, it really hauls with full throttle. It will even hover.
I like to design and fly unique planes.
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whatmovesyou
Here is a couple of videos showing that taping is the way to go.





The last is my favorite. Having only 80 x 160 range and for 2 3/4 min the thrust is there to do what I want to do. I use thrusters to increase high alpha and if you watch real close, I got it to hover due to the thrusters. Battery died right at end. Glad I wasn't high.
If you still don't believe me about the tape, have a bunch more videos.
I like to design and fly unique planes.
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