Introducing the new Stumax 90mm and 100mm EDF units - RC Groups
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May 17, 2010, 12:53 AM
The blade numbers go up to 11
stumax's Avatar

Introducing the new Stumax 90mm and 100mm EDF units

I just thought I'd give you all a quick look at what I've been playing with these last few months, two new fans designated SM100-45 and SM90-45, being 100mm dia and 90mm dia with 45mm hub dia. There's been a demand for a good sounding 90mm fan for a while now, I originally tried trimming down an SM110-52 but it was too heavy. I had a lot of SM110-45 motor tubes sitting around and as it's not such a popular fan (not sure why, it outperforms everything I've tested it against) I thought 'd put them to use. I used the same stator design as well, just shorter blades and then set about designing a 100mm rotor to suit. The goal for the 100mm fan was 5kW using a Neu 15 series motor. Testing shows that my power vs rpm calcs were pretty close, and a 1521-1.5Y on 12S seems to be a good choice, needs a lot of flight testing to confirm, of course. For the SM90-45 it looks like a 1515-2Y will be a good choice on 12S for 3kW, or perhaps a 1515-1.5Y on 8S - again, this needs to be thoroughly tested before I'll put these figures in stone. The rotors are 11 bladed, with the blades being individually injection moulded from long glass filled Nylon. the blades are assembled onto front and rear rings which lock them all together. Once the rotor is assembled, it is attached to a shaft adapter which then mounts to a dummy shaft in the lathe, then the front face is machined flat and the bore at the front is machined out to accept the aluminium ring which forms the locating face for the spinner. A lot of work and fiddling, but this ensure the spinner runs 100% true. As assembled, the rotors are close to being perfectly balanced, and I've actually run them without further balancing. Production rotors will be dynamically balanced.

Thrust-wise, the SM100-45 is almost matching the 110mm fans up to 3.8kW then it tails off a bit as expected. On 4kW it delivers 6.0kg thrust. The static efficiency is up around 92-94%, which is staggering, really, and the reason it's performing close to a fan with much more FSA. The SM90-45 is giving just over 10lb static thrust with just under 3kW, which is still pretty good considering it's a cut down rotor and loses the aerodynamic tricks I've used at the blade tips. BTW, FSA for the SM100-45 is 6264sqmm and 4771sqmm for the SM90-45. I'll post some thrust vs kW curves as soon as I've settled on the right kV and length motors.

The SM90 is basically the SM100-45 rotor trimmed down to 90mm, using the same motor tube (although I'll make them shorter later on for shorter motors to save weigh and cost) and a 90mm dia shroud. The shrouds are carbon/Rohacell sandwich construction, although if they prove popular enough I would like to go injection moulded, as making sandwich construction shrouds is too slow and tedious for my liking, and it means they are black and boring.

I'll be flight testing the SM90 very soon in a HET Super Sniper and the SM100-45 in the FeiBao F5E. I'm pretty confident both fans will be class leaders performance-wise. Sound-wise, the SM100-45 is quieter than the SM110-52 but the sound isn't as interesting, simply because the SM110-52 was designed to have certain pleasing harmonics, and the SM100-45 was designed to be super efficient (hence its quietness).

I'm not into vapourware so I'm not promising a release date. I'm hoping to have first batches done within one month, but don't hold me to it as I won't release them until they are 100% right. Please register your interest with your local Stumax dealer, or if you don't have one in your region, please feel free to email me. There are a few production things to be sorted, such as the shaft adapter which is currently the same tapered collet arrangement from the SM110-45 but I'm finding it's almost impossible to get a grip on the tiny rotor blades to tighten it all up. This will probably mean a set screw type shaft adapter which brings its own headaches as the fit on the shaft has to be perfect with zero clearance. There's also the issue of having mounting rails moulded into the shroud or not - what do you guys prefer? For production it's easier to have the rails moulded in (BTW in the pics you'll notice the sides of the SM100-45 shroud have rough looking patches - they are from the peel ply I put there so I didn't have to roughen it up to glue the mounting rails on), but some people may not want rails at all, preferring a flange mounting.

I hope you like them, I'm pretty excited about them.


Edit: Added Preliminary Owner's Manual to page 1.
Last edited by stumax; Sep 29, 2011 at 04:43 AM.
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May 17, 2010, 12:57 AM
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rorrock's Avatar
Yeehah... now i dont have to sit on this anymore... god its been killing me...
this is what i've been waiting for.. looking at testing a 90mm in a jet-teng L39 and a 100mm in a Fox Composites hawk (or sabre).
May 17, 2010, 01:28 AM
Bypass Ratio = Infinity
scatsob's Avatar
Wow, those are some beautiful fans. The SM100 looks perfect for a Spark.
May 17, 2010, 01:51 AM
corsair nut's Avatar
stu, those fans look AWSOME!!!! man would i love to test fly my cougar on that 100!!!! and my sabre on the 90!

best of luck with the fans.....i may have scrape the pennies to get one!!
May 17, 2010, 02:01 AM
Pursuit of Happiness
Ron101's Avatar
Very nice Stu!!! they look amazing... now these are pullers right? not tractor

I was flying my Spark this weekend at a local jet meet and it's always fun having people come up and ask my why mine sounds so nice

Also heard how long is he going to stay up , is ever going land

that kind of stuff is so fun with your fan!

can't wait to hear more details on power readings and flight test I wish you the best luck and think you are a true innovator in the hobby

This is great news for us all, and I'm one of your biggest cheer leaders

May 17, 2010, 02:05 AM
Pursuit of Happiness
Ron101's Avatar
Stu for mounting I personally like the glue on ply tabs the DS was useing on the DS-94 hdt
you can line up the fan like you want and your good to go... just glue them on
May 17, 2010, 02:51 AM
Speed Demon
GregG's Avatar
Glad to hear that these are finally taking the stage Stu, they look superb!

I'm kinda suprised that they're pullers and not your regular fan. Whatever works!

I'll bet one of these 100's would blast my Yellow A-4 to the moon!
May 17, 2010, 03:14 AM
Registered User
EDF Crazy's Avatar
Way to go Stu, Very nice looking fans. cant wait to try them out. Are these two fans outer shroud diameters what you have mentioned in your post? 90mm & 100mm? or is it the rotor diameter? Just clarifying as i had thought that your 110-52 fan had a 110mm outer shroud diameter and it turned out to be 115mm.

And do you have a bigger size fan like these in the pipe line

Last edited by EDF Crazy; May 17, 2010 at 03:21 AM.
May 17, 2010, 03:17 AM
Jets fly goooood!
felix72's Avatar
Hi Stu,

very nice job on those new fans!
I'll be following and looking close to their development.
I was waiting for something coming out from you because there were fan's segments, the 90 in particular, in which your fans needed to be.

May 17, 2010, 03:44 AM
Registered User
MaHö's Avatar
Really nice done Stu!

reg Martin
May 17, 2010, 04:44 AM
My project: FAIREY DELTA 1
Erik v. Schaik's Avatar
Originally Posted by stumax
The shrouds are carbon/Rohacell sandwich construction, although if they prove popular enough I would like to go injection moulded, as making sandwich construction shrouds is too slow and tedious for my liking, and it means they are black and boring.
never change a winning team. You don't want them to be confused with a TJ or DS. Black is boring!

Beautiful fans Stu!
I'd vote for a flange+gommets. Rails is pretty old fashioned. You might reconsider both tough
May 17, 2010, 05:46 AM
Suspended Account
Originally Posted by rorrock
and a 100mm in a Fox Composites hawk (or sabre).
Yea, that sounds like a good idea.
May 17, 2010, 06:08 AM
EDF Jet Jam 2017, June 15-18
Kevin Cox's Avatar
Me likes!
May 17, 2010, 07:32 AM
Registered User
Tempest's Avatar
Very, very cool Stu! You are the master. I'm looking forward to learning more about these.

May 17, 2010, 08:14 AM
Registered User
jhaywood's Avatar
Stu, you have the sexiest freakin fans! You should make HUGE version of your rotor for use as ceiling fans, or even wall art.

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