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Radio Control Forum => Jets => Topic started by: Konrad on September 11, 2017, 04:50:26 PM

Title: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 11, 2017, 04:50:26 PM
Let me admit that I have this addiction. I as a modeler am ashamed to admit that I’m addicted to foam ARFs. True modeling to me is where one creates a representation of a subject or a simplified testing tool.
What I have here is a no bones example of check book modeling. For $260 (Labor Day sale)I found this Taft Super Scorpion 90mm 8 cell sport jet for the same price as the 80mm 6 cell Freewing.

This is exactly the type of model I like to get. That is one that has a bad reputation on the forums. For about 3 hours of hobby work and $50 to $100 dollars in replacement parts (if any fail my burn in) I’ll have a model that will out perform the $450 FMS 6 cell Super Scorpion. Here is a photo of the Super Scorpion next to the Dynam Meteor. I will say that transportation might be an issue!

Yes, this will become a detailed review of the Taft Super Scorpion. On first blush it looks to be a good value for the current asking price of $299. Everything worked straight out of the box. My JDPower's initial customer quality evaluation is that the Taft Super Scorpion is not up to par with the FMS offerings. Initial quality appears to be much better than what I've experienced with Dynam models. I'd place the quality right around what we might expect from say Freewing. That is good but in need of some work prior to first flight. To be brutally honest the quality we find in the  Taft Super Scorpion really is just half a step below the Freewing models. On balance the Taft Super Scorpion a great value for real modelers who have the skills and fortitude to put a little work into their models.

We shall see if at the end of this exercise I can hold my head up as a real modeler.

All the best,

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 13, 2017, 12:29:14 PM
Keeping with my trust but verify approach to these mass market toy EPO models. I’ve inspected the power system. For the most part I’m pleasantly surprised at what I found. I was really happy to see that Taft added a cap pack to the battery side of the ESC to combat the issue of damaged MOSFETs as a result of the long battery leads. ALL OEMs should ad these if the anticipated battery leads are to be longer than 6” to 8” long! I was also surprised to find dual switch ESC’s included in the power system. Very nice touch.

I was a little disappointed in that I found a mis-marked motor. The sales brochure and the kit manual clearly state that the motor is a 1300KV motor. Unfortunately the motor in labeled as a 1500KV motor. Modeling the fan on 8 cells would indicate that the motor is close to a 1300KV motor the current draw measured of 66 amps closely matched that of a 1300KV motor.

What little I could find about the X-team motor is that this 3674-1300KV has a current limit of 48 amps yet has a power limit of 2.4KW. This isn’t as bad as one would first think. The motor really is designed for “buggy” use. Being as this is in an EDF it is in the cooling blast of the efflux which allows for huge over amping. As measured I’m getting 66 amps but at a voltage of 32V the power output is well below the 2.4KW limit as it is only 2.1KW. That being said the 309g mass of the motor really is a bit on the light side. One really needs to add a finned heat sink to the motor.

I was a bit shocked to find that I could not remove the EDF unit from the airframe without taking it apart. One needs to remove the inlet lip to draw the EDF unit through the hole provided by Taft to service the EDF unit. This cause some issues at the point of manufacture as glue was dripped onto the rotor blades when trying to glue on the inlet ring. This might account for some of the rough running I noticed in my testing.  I’ll try to balance the rotor to see if this smooths things out.

Edit: Current limit is 48 amps per X-Team.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 14, 2017, 06:18:06 PM
Plugging away at the Taft Super Scorpion I’ve found some Good Bad and Ugly points.

What I really like is the look of the anhedral stab. This combined with the splayed out vertical fins make this a great looking model yes even better than the MD F-18 E/F US fighter! On a more practical note I hope it addresses an issue I’ve notice with the other offering of the Scorpion. Having flown the Freewing 80mm Scorpion and the 70mm ROC/FMS Scorpion I notice that the elevator response was a bit lethargic with the straight stabilizers. I suspected that this might be due to some separation bubble on the stab or wake turbulence from the wing. With the anhedral stab Taft is insuring that some part of the stab is working in clean air regardless of the plane’s attitude.
I have to admit that seeing this stab anhedral gave me concern about the attachment points to the fuselage. Clearly Taft is NOT using a through spar (rod) to mount the stab and its associated pivots. Taft has give the stab a nice wide bearing area inside some large plastic load spreaders. What I do have are some grave concerns about the length  of the stub to which the stab is bolted.

I did notice a no fly item and that is the stab push rods. Taft (and most other toy EPO vendors) is using a low grade 1.2 mm wire with stamped thread. This wire is so flexible that Taft added a carbon tube to try to stiffen it from flexing mid span.  This weak wire and the poor quality spherical end combined with the gross course 0.75 mm thread pitch necessitated a full rework of the push rod. I’m using Dubro 2mm Swivel Ball Links Cat# 368. I’ve threaded a 2 x 0.4 pitch thread onto a 0.078” (nominal 2mm) music wire. You might have noticed this means that you will end up with the rod that allows for twice as fine a length adjustment! The wire is 110mm long with [email protected] 14mm long threads. (To thread music wire you need to anneal the wire otherwise you are likely to break you 2mm die).

I do have a concern with the stab elevator servos. Not with the brand or quality of the servo. If Quique Somenzini is willing to put the reputation of his new venture “Flex Innovation” on the line with Potenza, I’m sure he has vetted them well. My issue is with the size/power a 19 gram 2.9 Kg-cm sounds rather weak for this weight and speed of aircraft. With proper geometry it might work. But I read far too many folks are crippling the servo’s performance by limiting the motion of the servo to 50% or less. You should alway try to set up your servo/surface throw so that you are using 100% to 120% of the servo’s normal rotational throw. This keeps the power torque up and improves the surface resolution. MOVE THE PUSH ROD CLOSER TO THE SERVO CENTER LINE!

The battery area appears to be huge, at least 87mm wide and 56mm tall. This space goes all the way 30mm past the wing’s carbon through spar! I can’t understand why so many folks claim to have issue making the CofG with the appropriate batteries.

The ESC mount, well that is just a bad idea!

All the best,

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 14, 2017, 06:20:07 PM
Flight is all about fluid flow.

Over all I’m NOT impressed with the flow ducting on ether end with this large model. The upthrust really has me concerned. I recall having a horrible time with changes in flight trim with changes in power setting with the Multiplex twister (it had down thrust in the thrust tube). I fear that Taft is using upthrust to over come some concerns about being nose heavy. Upthrust is the wrong trim variable to adjust for being nose heavy!

All the best,

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 15, 2017, 01:43:41 PM
Some corrections are needed.
While Taft does provide 2 SBEC they are not redundant. One is a set for 5.5V. I assume this is to power the radio and servos. The other is set at 7.45V with a 2 pin JST connector on the output. I assume this is to drive some other accessories, such as brakes (No brakes are provided on the wheels).

I was in error saying that the FreeWing 80mm Super Scorpion was a flat tail ship. She does have a slight anhedral stab. This is much like this Taft Super Scorpion but at what appears to a lesser angle. (I'd like to make note that the stab pin purchase area appears on the Freewing 80mm Super Scorpion to be twice as large as the area on this Taft 90mm Super Scorpion.)

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 15, 2017, 11:11:38 PM
Cleaned off the glue from the Taft rotor and rebalanced the rotor. Wouldn’t you know it, the glue (weight) was almost 180° away from where I needed to add weight to get a smooth running EDF unit.

I performed my 5 minute burn in on the Potenza DS19 servos and they past with no issues. But looking at the size of the stabilators I wasn’t comfortable driving them with a 2.6 Kg-cm servo. As I had a few HS5085 laying around I felt these were more suitable. Luck would have it that removing the plastic pocket, Taft uses as a screw pad to mount the servo, leaves a foam pocket that fits the HS5085 perfectly. Keeping with my belt and suspenders approach to flight safety I glued in the HS5085 with both Welders contact cement and hot glue. The bond area is close to the same as with plastic pocket. The only down side with this is that it will take some effort to replace the servo should the need arise.

I will reuse these Potenza DS19 servos to replace the 13 gram aileron servos.

Something to be aware of is that regardless of the level of modeling good mechanical protocols need to be adhered to. In the case of these metal servos there needs to be some form of lock washer added. Without the lock washer (star washer) the servo arm screw WILL vibrate out, with the result being total loss of control from that servo.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 18, 2017, 06:45:05 PM
More correction/clarification!
This is the price of doing these builds live.

The power from the stock EDF unit just jumped from a current draw off 66 amps to that of 107 amps with a steady draw of 98 after 30 seconds.
I can only attribute this to better batteries; 25C for the 66amp reading and on the bench, 55C (TP Lightning series) for 107amp and with the EDF in the fuselage.
Will definitely be adding that finned heat sink!!! And limiting the flights to 3 an hour to keep the duty cycle (heat build up) in check.

Well, Taft isn’t making it easy for me to up grade this ship. I wanted to move the Potenza DS19 from their location as stabilator servos aileron servos. While the aileron servo cover/mount will hide the larger Potenza DS19 the aileron pocket and liner Taft provides to hold the cover/mount will not allow an easy upgrade.

It has to be more that the battery impedance! I was messing around with the ESC programing this weekend. Maybe I released some hidden monster in the ESC programing. Re-running the numbers in the predictive programs it is looking like the motor may in fact be a 1550Kv motor (I owe X-Team an apology the motor may not be mis-marked). If it is indeed a 1500Kv to 1600Kv motor the nominal amp limit rose from 48 amps for the 1300Kv to 70 amps the motor 1500Kv labeled)

Not sure I trust any of these EDF simulators. I should just remove the fan and measure the Kv directly. Unfortunately I can't safely remove the fan as there is no motor hold feature on the Taft adaptor and the nut appears to be held on with a very strong thread locker.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 19, 2017, 01:27:54 PM
Well, just incurred my first of what I’m sure will be the first of many added expenses, spare parts.

This has nothing to do with Taft or any quality issues. I just like to have replacement parts on hand for all the models I have in flying condition. And the things that first hit the ground, spinner and landing gear, are high replacement items for me. So I got some retracts.

Again luck would have it that Horizon Hobbies (HH)is closing out their inventory of Taft parts. While HH carried the Viper jet but not the Super Scorpion.
Many of the components are the same between the Viper and the Super Scorpion.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 20, 2017, 02:30:03 PM
Just got back from the machine shop where I fitted a 28mm long (actually the fins are 24mm) finned heat sink to the motor.  I’m using “Arctic Silver Thermal Adhesive” both as the heat transfer compound and as the adhesive to attach the heat sink. I took the opportunity to machine a 4mm long pilot diameter into the finned heat sink. Lacking any other data I machined this pilot diameter to have a wall thickness of 1mm. In hindsight it might have been better to make the wall 0.5mm or 0.7mm thick. The purpose of the pilot diameter is to give added support to the rear of the stators and to add some rear support to the long motor.

I find it odd that most heat sinks are supplied with an anodized finish. This is odd for a heat sink as aluminum oxide (the anodize without dye)is an insulator! I did grit bast the ID of the heat sink to get improved thermal transfer from the motor case to the heat sink. I’m ashamed to say that I kept the blue anodize as it looks good against the red fuselage of the Super Scorpion.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Hank G B Z on September 26, 2017, 05:20:36 PM
" I’m ashamed to say that I kept the blue anodize as it looks good against the red fuselage of the Super Scorpion. "

  I am aghast.  The Konrad I flew with would never let form over function go.  I always heard from you "Form follows function..."  To sad! I hand down the following punishment.

   You must go finish your Guillows Beachcraft Privateer/ Dutchess conversion and end this check book modeling which is clearly affecting your engineering judgement.  I'm supposed to be the one picking a pretty color over something that works right...

  The scorpion is cool thoguh.  Speaking of Scorpions did you ever fix that Cox one i used to fly? 


Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on September 27, 2017, 12:45:46 PM
LOL; (head down in shame)

Lets see if I can recover from this. As aluminum is very susceptible to oxidation the grit blast surface would have been covered in oxides soon enough. So I choose to keep some color as it might aid in the resale of the jet. Now if I had access to alodine I might have grit blasted the outside of the heat sink and applied the alodine treatment to protect the aluminum from oxidation. I think I recovered from the shame of allowing function to follow form. (Alodine is an acid etching process that protects aluminum from corrosion and oxidation.)

The wife is asking much the same question about the Guillow type models. Her opinion is that these foamies are the antithesis of what modeling is, that is the creation on a smaller scale. They maybe fun and challenging to fly and even small, but not really modeling, as one does little creating.

That little Cox Scorpion is being used for templates and as a parts queen for the second Scorpion. (The Cox Scorpion is a small 1/2A pattern ship of old.)

Back to the Taft Supper Scorpion.
A major manufacturing issue has shown up. That is the flaps are badly bowed (warped). I’m not sure if this is a problem with the cooling of the EPO parts after release from the mold. Or as a result of paint shrinkage as it looks like only one side of the flaps has paint (the red side).

I will have to remove the flaps and add stainless steel stiffeners to control this warp (ALA the Multiplex Heron). I might even add some carbon to the trailing edge.


Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Hank G B Z on September 27, 2017, 01:08:32 PM

    You are forgiven for keeping the blue anodize.  I used alodine once, i was not a fan.  We have stopped clear anodizing parts at work for the most part as it doesn't do much.  Hard coat anodize for wear purposes we still do. 

    Your wife is right we should do more modeling.  I haven't done much modeling this year and none of it has been balsa kit.  Well that one Flying flea from bang good, but that was more assembly than building.  Anywhoo. 

    The scorpion looks good, that warp is odd.  Your fix sounds good to me.  Looking forward to hearing about test flights. 


Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on October 16, 2017, 07:24:17 PM
Some annoying quality/assembly issues.

I was flabbergasted that anyone would try to glue a structural component to paint! How difficult would it really be to make a mask for this area prior to painting? It is omissions like this in the assembly process to costs one, one reputation!  Taft you knew better than to try this!

It looks like the pocket for the flap hinges on the wing side are a little too shallow. Easy enough to fix, shave the pad area with a utility knife 0.3mm. I suspect this was a mis-judgement as to the shrinkage rate of the foam when making the molds.

I can confirm that the warped flaps are as a result on uneven painting of the flaps (and ailerons). Taft needs to apply a clear coat to the opposite side (top of the control surfaces).  

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on October 17, 2017, 05:57:25 PM
The severe warps on the flaps has required that a stiffening rod be added to the flap full span. I chose to use a 1/8 (not 3/16) stainless steel tube (K&S # 87111) much like what we see with the Multiplex Heron. This and the addition of some 0.014” carbon to the trailing edge of both the flap and aileron result in a trailing edge that looks to be rather straight. We will see what the flight trim dictates. But I’m sure the control surfaces will now respond much better than if I had left the warp in place. With the Taft Super Scorpion the flaps are a bit more than your standard flap. This is because the manual has you mix in snap flap as a function of up elevator. This is to give the small wings a boost in their lift coefficient (added camber) and to gain some much needed rigged washout at higher angles of attack. With warped trailing edges I’m sure the low and high speed (high “G’s”) flight characteristics would have been compromised.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on March 23, 2018, 02:04:26 PM
After a 6 month hiatus I decided to throw some money at this and buy some wheels. The wheels that Taft supplies are horrible, they are hard and HEAVY. I found a set of wheels sold by Maxx Products that fit the bill perfectly ( P/N AW225). These are foam with a hard rubber like center line compound. I think these will become my standard wheels for my light to mid sized models.

Note: That the plastic bearing that come with the wheels are NOT adequate for the weight of this model. Maxx products sells a set of brass bushing for these higher weight models (P/N AWB04). ( I never understood the need of desire for ball bearing wheels on our models. My roll out distance is already far too long!)

The Dave Brown style of lite wheel while they work often don’t provide enough lateral support, and wear far too fast with my style of landing.

With the 2.25” wheel I had the make some clearance by beveling the rear of the landing gear strut yoke.
Even with the stock wheel there wasn’t adequate clearance in the wheel well. I opened up the wheel well biased towards the rear, after all this is the direction most struts move as the aircraft ages.

Title: Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Post by: Konrad on January 25, 2020, 03:40:08 PM
I’ve been stalled on this project mainly because of transport issues, I have a first gen. Prius. Also I’ve ben focused of FAI F3F racing. And now that the FAA has given us a drop dead date for our hobby I thought I'd try to fly this model befor that date.

Now I’ve heard that there are some concerns with the Taft Scorpion in that she hunts in pitch. I found this a bit odd with that huge stabilizer. Looking closely at the control linkage I found a gross engineering oversight. Taft is using a large set screw as a drive pin to connect the control horn to the stabilizer axle. This results in a horrible amount of slop between the control arm and axle (shaft) as one can’t torque down on the set screw. I’ve read that some guys are trying to use teflon tape and or loctite to take up the clearance. The fix is to allow the arm to clamp down on the shaft. I’ve decided to change the drive mechanism with a cap screw verses the drive pin. To do this one needs to make 2 modification to the arm. First is the drill out the threaded holes to clear the 3mm threads of the cap screw. And then make a trough in the control arm to allow clearance for the cap screw head. Keeping the thread in the shaft allows the head of the cap screw to clamp the arm onto the shaft. This also allow one to add torque to the threads taking up any clearance in the threads. I still add loctite for stability but with the clamping force from the cap screw there in no slop to allow the stabilizers to move.

All the best,