Stumax 110-52 installed in CompARF Spark EDF - RC Groups
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Nov 05, 2007, 02:18 AM
2018 EDF Jet Jam June 14-17
Robert Belluomini's Avatar

Stumax 110-52 installed in CompARF Spark EDF

I decided to use the new Stumax 110-52 fan unit in the new Composite ARF Spark sport jet. Stu's fan is virtually a drop-in fit in place of the DS-75 that the airframe was designed around.

Stu's fan offers the following features:
1 High efflux velocity
2 Excellent thermal transfer via the aluminum IGV stage
3 Oustanding efficiency
4 Lower operating rpm/quieter operation
5 Neu Motor 1912/1915 motor series

For a complete understanding of this new unit:

So what exactly was involved to fit this unit?
The OD on the DS-75 is 115 mm, the SM 110-52 is 116.5
This meant adapting the ducting to the SM 110-52.
I first considered splitting the ducting to fit around the the slightly larger OD of the SM110-52.This involved splitting the seam almost along its entire length to go around the fan shroud. The other option was to remove the lip and make a new one.
I chose to cut off the lip and make a new one. This route was the better choice as the ID on both units is the same and I wanted a smooth flow of air into the SM110-52, splitting the ducting would have meant a sizing
So off with oringinal flange it was. I squared up the surface and decided I would use a piece of .010 G-10 glass board cut 15 mm wide and long enough to wrap around the perimeter of the fan shroud.
I then used parting wax on the exterior and interior and front edge of the fan shroud. No need having all the parts stuck together when we get done .
A wrap of extremely thin Tamiya paint masking tape was wrapped around the front edge of the fan housing to allow a controlled gap for the ducting to slide on easily when done. I then waxed the tape. A second piece of G-10 was cut and taped to the inside of the fan housing to form a shelf that would locate the duct ID to the fan housing ID this was also waxed. I then took the ducting and place on the shelf I created and oriented and centered it on the fan. I taped it from the inside to the fan housing. I noticed a small gap between the ducting and the fan housing about 1/3rd of the perimeter and used Hysol to fill this gap prior to sliding the new inlet lip in place.
The inlet lip was now slid in place and the width was split between the fan housing and the ducting. I took the glue gun and filled the gap between the new inlet lip and the ducting and then smoothed it with my finger dipped in Denatured alcohol to make a smooth fillet. I stood the unit on end and allowed the glue to cure for about 7 hours before I seperated the pieces.
I now had a perfectly sized lip that matched both the OD and ID of the Stumax 110-52.
Last edited by Robert Belluomini; Nov 06, 2007 at 06:26 PM. Reason: Text added
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Nov 05, 2007, 02:51 AM
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YellowAircraft's Avatar

That's really exciting! That fan looks great. Good luck!
Nov 05, 2007, 03:06 AM
2018 EDF Jet Jam June 14-17
Robert Belluomini's Avatar

Mounting the SM 110-52

The next step was to mount the fan. I removed the flanges that come on the SM fan as they are too long to work in the Spark and their "T" shape would require widening the bearers that are installed in the Spark.
I decided 1/8" marine grade ply would be used to make the new flanges.
I cut two pieces .5" x 2.375" long. I drilled ahole .375" in from each end and centered on the length. Next I had to locate the fan so it was centered on the efflux opening at the rear of the Spark. The former at the trailing edge of the wing saddle is radiused and I used it as an alignment gauge.
I determined that three pieces of 1/8" dowel taped at the 9, 12 and 3 o'clock positions around the fan and then a strip of 1/8" ply placed on the remaining side would locate the fan in the correct position. I double checked that I had located the fan in the correct position and then I taped the fan to the ducting and the ducting the the inlets of the airframe. I did want anything to move as the next step was to place the mounting flanges into place and glue them to the fan housing with CA. I now took my drill with same 3 mm bit I had drilled the mounting flanges with and made a starter "mark" into the fan bearers in the model. After removing the fan unit I then drilled 4 mm holes for the blind nuts. By making just a "mark" with the 3 mm bit and then drilling the hole with the 4mm bit I achieved perfect alignment between the parts.
I then used machined blind nuts. These are sourced from the Vario Helicopter company and are far superior to the screw machine types. I reinstalled the fan into place and bolted it down with 3 mm bolts and washers that are supplied in the kit. The beautiful SM 110-52 is now installed in the Spark.

The balance of the this thread will be the insatallation of the radio gear, retracts ,and batteries. I plan to have this done next weekend and report my results so stay tuned.
Last edited by Robert Belluomini; Nov 05, 2007 at 01:44 PM.
Nov 05, 2007, 07:14 AM
Registered User
Gordon's Avatar
I've been looking forward to this thread Bob! It looks like a pretty "compact" fuselage despite appearing large wrt the wings in the photos we've seen before. Hope everything else fits as good as the fan.

Good luck with the project

Nov 05, 2007, 10:07 AM
2018 EDF Jet Jam June 14-17
Robert Belluomini's Avatar
Thanks Gordon. Being a 90 mm user up until now, I forgot just how large the 110-120 fans are. There is plenty of room for all of the components. I'm waiting for my elevator servos that are on B/O but should have those this week. I have to decide which brand battery I will use too. I was planning on going with the EVO 30C but Neu Energy has new 30C in a 5000 mah.
Nov 05, 2007, 01:39 PM
smug in granny panties
monkamarm2000's Avatar
you can also save a few grams with the evo 4900's. there just like the 5000 but tad lighter but almost same duration and same c rate's. might be worth taking a look at.

Nov 05, 2007, 01:46 PM
Tear down the WALL!
ralf dvorak's Avatar

that's the way it should be built!

way to go, Bob, nice clean installation. That's how a plug in should be: clean.
Same to do on the thrust tube, I've always disliked mylar, wrap around and tape fixings...

Hey, real european blind nuts, couldn't believe it!

Nov 05, 2007, 02:05 PM
2018 EDF Jet Jam June 14-17
Robert Belluomini's Avatar
Thanks Ralf,
I'm a hardware nut. Washers under every bolt or screw and they must fit concentric too.
I started using these back in the early 80's on my helis.
I remember the first time these came in a Schlueter kit, I was spoiled, I hate use the crappy screw machine type.
Nov 05, 2007, 03:06 PM
Registered User
ChrisAttebery's Avatar
OK Bob, where'd you get those blind nuts? I'm sure I'm going to find a use for them and just have to have some.
Nov 05, 2007, 04:37 PM
The blade numbers go up to 11
stumax's Avatar
Cool! I can't wait to see how it goes. It should have over 5kg static thrust with about 4.5kg AUW - good numbers! BTW, this fan has a 1912-1Y in it, good for 9S and about 3kW.

Nov 27, 2007, 09:16 AM
Registered User
Jim Phelps's Avatar
While waiting on the fan I've been putting all of the servos in mine. The instructions are very detailed and layed out well so everything goes together pretty quick. If you use the JR DS3301 servos as specified it all fits perfect.

The quality of this jet has been flawless so far. It even comes with all of the hardware that you need.

Attached some photos of the rudder servo install.

Nov 29, 2007, 08:09 AM
Registered User
Jim Phelps's Avatar
Wing and horizontal stab are done.

I used some titanium struts and aluminum axles rather than the steel that came with the Spring Air 301 retracts. I'm not sure what the steel weighs but the titanium w/aluminum weigh 11g each. I don't think it makes a big difference, I just like the titanium.

The finished wing weighs 2lbs.-2oz.
The horizontal stab weighs 8oz.
Nov 29, 2007, 10:29 AM
2018 EDF Jet Jam June 14-17
Robert Belluomini's Avatar
Great work Jim!
I'm doing the servo install and hope to finish my model early next week.
I'm hoping we'll see some decent weather so I can make a test flight before the snow flies.

Nov 29, 2007, 11:35 AM
Registered User
Jim Phelps's Avatar
Thanks. I didn't mean to steel your thread, just thought I would post some progress. It's gone together just like the instructions call for, no re-engineering or trying to figure out what to do next.

I hope we have a few more nice days but it's not looking good. Makes you envy the guys that live in southern California and Florida!

Dec 13, 2007, 11:06 AM
2018 EDF Jet Jam June 14-17
Robert Belluomini's Avatar
Here's a how I aligned the main gear to each other.
I took two pieces of straight 5/32, cut them so they do not overlap in the retracted position and a piece of 5/32 ID brass tube,
slide the brass tube on to one of the wires then retract the gear and slide the wire to join the two mark the holes and you have perfectly aligned retracts.

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