Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin (Account/Technical Issues)  |  Contact Global Moderator
December 02, 2021, 02:22:52 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 [2]   Go Down
Print
Author Topic: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)  (Read 4443 times)
0 Members and 1 Guest are viewing this topic.
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #25 on: April 27, 2020, 02:18:16 PM »

Some more setup details. I have to admit I never could get the tiller arm to work reliably with the stock nose strut. This was with both the FMS and Taft Super Scorpions and the other Taft models. My fix was to use the mounting plate itself as a guide (stop) keeping the pushrod from moving up rather than actually rotating the strut. To do that I swapped the spacer and tiller arm block on the strut pin. This brought the tiller arm block closer to the mounting plate but away from the anti-rotation ramp. I then moved this ramp as far forward as the mounting plate would allow. As a safety I added some ramps to the mounting plate to ensure that the tiller arm could not bind on the mounting plate should the rudders be commanded while the retracts were in motion. A weak point in this tiller are system in that there really are no stops to keep the tiller arm moving down. To minimize this issue I bias the “Z” bend so as to have the push rod pointing (biased) to the fuselage bottom at all times.

I was also fighting an elevator induced roll. This was traced to improper Ackermann effects as a result of servo arm geometries.  With odd spline count servo outputs the servo arms are NOT aligned at the same spot with the feed back pot when flipped between sides. One will need to use the "trim offset" in ones radio to make sure that the servo arm geometry is correct and that both surfaces move the same along the surface’s travel. More advance radios such as those running OpenTX can use curves. Also make sure that the end points allow for the same total deflection.  I like elevator differential to help with the feel for inverted flight. As one is working against the camber of the airfoil I find I need more “down” than “up” in my elevator response.

Much the same conditions apply for the ailerons. Make sure that the servo arms are point forward the same amount for the initial mechanical differential.

All the best,
Konrad

P.S.
I see that FMS has added a shelf to keep the stearing push rod in place. This would be more effective than my Z bend bias.
Attached files Thumbnail(s):
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
« Last Edit: April 27, 2020, 02:45:29 PM by Konrad » Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #26 on: April 27, 2020, 04:53:25 PM »

Mainly for transport and storage reasons I’ve made the nose cone removable. I’ve found that magnets never are strong enough to keep the nose cone, on even when I on the rare occasion make a good landing. So I’ve added carbon rods to actually carry the flight and landing loads.

Another issue that I’ve always had with snap on canopies is that they come off in flight, particularly when in knife edge.  To stop that I’ve added a carbon rod that pins the  canopy to the fuselage. It is a bit of a pain having to pull back the nose cone to release this pin. But it is much better than spending most of the day looking for the canopy that is lost in the fields.

All the best,
Konrad
Attached files Thumbnail(s):
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
« Last Edit: April 27, 2020, 06:48:48 PM by Konrad » Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #27 on: April 30, 2020, 09:19:59 PM »

As I mentioned earlier I felt that the Taft Scorpion's inlet system might be lacking. Looking at the small inlets up front and the large cheater hole I was thinking that the air going past this cheater hole might actually be drawing air out of the duct at low or negative angles of attack.

As I had some SuperFil epoxy already mixed up for another project I thought I'd run an engineering exercise. Along with filling in some of the inlet grate periphery for (esthetic reasons) I built up a 2 to 3mm air dam. It was hoped that the dam would allow more air mass into the fan giving me added acceleration.

The jury is still out on this as I've only got 2 test flight in under this configuration. In a shallow dive I do think my top speed is a bit better. In level flight I think my acceleration is better but can't say as I'm seeing a lot of added speed. At low speed in the vertical I don't see any change.

Attached files Thumbnail(s):
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #28 on: May 01, 2020, 02:52:25 PM »

I have to say I really liked how the FMS Super Scorpion was performing even on 6 cells. Like I said I think it can be traced to the inlet. The key is that there isn’t a cheater hole in the FMS inlet.

Here is what I think is going on with the inlet for the Taft Scorpion. The inlets are far too small. As this is a sport jet I don’t understand why they were made so small! The inlet duct gets larger towards the fan. This allows the air to slow down causing a pressure rise in the duct. Right before the fan we have a cheater hole. This cheater hole is in an area of low pressure from the narrowing of the fuselage contours and the high speed air in flight flowing past the opening. This is fighting against the fan’s efforts to draw air in.

At higher angles of attack this isn’t as bad as one might think as the rear of the opening is lower exposing the cheater hole to some ram air effect from the forward motion.  Unfortunately the Taft Scorpion has the wings set at a rather high angle of incidence. Meaning that for most of the flight profile the rear of the fuselage (cheater hole) is not exposed to the incoming air.

I hope that adding a little air dam will add pressure to the cheater hole area. I hope that what I gain in airflow going through the fan makes up for the added drag from the air dam for most of the flight profile.

If anybody has any input on this I’d like to learn what you think. Do I have a large enough air dam (2mm to 3mm high). Is this is a waste of drag? If so, I can sand the air dam off rather easily.

So what do you all think?

All the best,
Konrad
Attached files Thumbnail(s):
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
« Last Edit: May 01, 2020, 03:35:39 PM by Konrad » Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #29 on: May 29, 2020, 02:35:46 PM »

I think I may have found the missing performance. The ESC Taft uses is a Flycolor ESC. This ESC has a thermal protection circuit. This is nice as it gradually cuts back the power to 40%.

I suspect that the flights flown with/against the FMS Super Scorpion were flown with the ESC cutting back on power.

The bad news is I'm flying this with a Spektrum radio and don't have telemetry. If I was flying FrSky it would be super easy for me to add some thermal sensors. (I'll need to look into this a bit more).

Next time out I'll change the ESC frequency from 12 kHz to 8kHz and maybe up the timing from 7.5° to 11.25°. I'll also see what I can do to get more airflow around the ESC.
(You might have noticed that I removed the OEM ESC mounting shelf and have the ESC tucked "nicely" into the turtle deck.

The good news is that at 40% power the Taft Super Scorpion didn't embarrass itself.

All the best,
Konrad
Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #30 on: June 03, 2020, 04:05:39 PM »

That was it! Th ESC was cutting back as a result of over temp.

With the ESC frequency lowered to 8kHz, the motor timing increased to 11.25° and the ESC lifted 10mm into the inlet duct slip stream. I actually allowed some air to flow around the ESC by cutting some air paths into the foam. This was opposed to just relying on the heat sink to carry away the heat.


With the ambient temp being 33°C I was able to run at full power (107 amps, 3 kilowatts) for about 135 seconds. I was also able to fly using energy management for 4 minutes with no thermal cut backs in the motor/ESC power.

I didn't fly against any other FMS 90mm Super Scorpions, but the verticals are now a joy to behold.
Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 39
Offline Offline

United States United States

Posts: 2,313


Topic starter
Measure twice cut once



Ignore
« Reply #31 on: October 27, 2021, 09:31:57 AM »

I often judge how one feels about a product by how it is maintained or if it is purchased again. Here with the Taft Super Scorpion I've purchased another  after having crashed my first one. As I've said before this is one of the best landing EDF jets. It really helps one (me) look good with the high alpha flair.  Yes, there are some control mechanics issues but these are well within the ability of most real modelers to correct.

I want to make it clear that the crash was 100% pilot error. This really hurts as the ship was very stable and easy to fly. With stable aircraft I like to fly low and in close. on the last flight I wanted to present the Taft Super Scorpion as a very majestic aircraft. I did a high power climb after take off to demonstrate the power of the 8 cell over the typical foamy 6 cell set up. I followed this with a tail slide into a dive for the runway, with a  shoulder height pull out. At this point I wanted to be real smooth on the controls so I switched to low rated, or so I thought. With covid restriction it has been a while since I flew with my Spektrum DX9 radio. What I thought was the rate switch was in fact the flaps! So in high speed flight I in effect had thrown out full flaps! the model pitched down. I over reacted and pulled up into the vertical. (She should have snapped, aerodynamically and structurally, but didn't)! Rather than just going up to gain altitude I was flipping switches trying to reconfigure the TX. Well you guessed it, I lost airspeed, retracted the flaps and snapped the model into a low level spin! The attached photo is the result. Did I say I should have just powered up into the vertical and gained some altitude. Cry

Its been a few months since I dumb thumbed my Taft Super Scorpion into the ground. It took me a while to find a replacement airframe as none of the typical importers carry the Taft brand. I found an airframe only on a site in China called Banggood. I hate to shop with firms that I can't interact with. But the Taft Super Scorpion flew so nice I had to replace her. So I took a chance and ordered the airframe. When everything was all said and done the delivered price for the airframe was higher than the close out price I paid for the ARF model (everything other than the RX and batteries) I originally paid from Banana Hobby. Yes, the way Taft Super Scorpion flies really is worth the cost! So I imported the model from China. It took a while but it arrived in good shape.

I know I said that if I lost this ship that I'd likely replace her with the FMS Super Scorpion. But as I had 3/4 of the support equipment and that the replacement of the Taft airframe was about half the cost of the FMS ARF. (Horizon Hobbies doesn't sell an empty airframe of their FMS Super Scorpion). I made the decision to get a replacement Taft airframe. Even though it wasn't as good a value as the fully populated airframe (ARF), it was a little over half the cost. Besides the Taft Super Scorpion has a much better color scheme than those gawd awful "hot rod" orange flames of the FMS Super Scorpion!

All the best,

Konrad

Attached files Thumbnail(s):
Re: Taft Super Scorpion 90mm 8 cell, Sport Jet (Banana Hobby, Thanks Alex)
« Last Edit: October 27, 2021, 09:44:13 AM by Konrad » Logged

Cut it twice and it's still too short!
Pages: 1 [2]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!