Question to Sting owners ( cruise )

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Re: Question to Sting owners ( cruise )

Postby Warmi » Mon Jul 17, 2017 11:56 am

Indicated and the temperature was low 70s.
Flying Sting S4 ( N184WA ) out of Illinois

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Re: Question to Sting owners ( cruise )

Postby FastEddieB » Mon Jul 17, 2017 3:06 pm

Again, when discussing cruise performance, TAS is what's meaningful and what most pilots will assume a pilot means unless otherwise specified.
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Re: Question to Sting owners ( cruise )

Postby dstclair » Mon Jul 17, 2017 3:11 pm

OK -- that's probably around 114kts TAS which ain't bad but I think it's a bit slow. Your prop is currently WOT at slightly less than 5500 at 2200'. I'd guess the 2200' is around 4000' DA. My particular Sting S3 with a DUC prop is optimized for MY flying preferences which is WOT of 5600 rpm at 5500'. You should call Bill or Mark back at SportAir and ask how much to adjust to get you around 150 more rpm. Of course, this would be if you want to optimized at 2200'/4000'. Me, I'd go a bit higher as that's where I fly on longer trips. YMMV.

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Re: Question to Sting owners ( cruise )

Postby roger lee » Mon Jul 17, 2017 6:10 pm

I tested 14 props several years ago on 4 identical planes that took off and flew side by side at the exact same time. Only test and research project like it in the US. Took months. Debunked a lot of what some MFG's think.
Bottom line on a Rotax is hull design and prop pitch is a everything. If you only have a ground adjustable prop your only help is the prop pitch. BEST BALANCED setup on ALL props was 5600-5650 rpm at WOT at your AVERAGE altitude. If you specifically need a better climb prop over cruise then a slightly flatter pitch is called for, but you will lose some cruise speed and fuel economy. More rpm on take off may be better for heavy planes, short field work and high DA flights.
There are absolutely no redeeming qualities with and over pitched prop. You lose any good quality. Anything below 5500 WOT in level flight is a loser. If you have an in flight adjustable props you do have some options.
I have the data that was sent to these prop companies to back it up.

Every prop company will tell you that they have the best prop since sliced bread. If you don't believe that just ask them.
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Re: Question to Sting owners ( cruise )

Postby drdehave » Thu Jul 27, 2017 7:03 pm

OMG. I just did a lengthy reply, but lost it, because I wasn't signed in or took too long and got timed out. That's happened before. I'll throw my 2 cents in when I recover later... :cry:
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Re: Question to Sting owners ( cruise )

Postby 3Dreaming » Thu Jul 27, 2017 8:53 pm

drdehave wrote:OMG. I just did a lengthy reply, but lost it, because I wasn't signed in or took too long and got timed out. That's happened before. I'll throw my 2 cents in when I recover later... :cry:

For those long replies you write them in a document program like Word, then copy and paste into your post here.

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Re: Question to Sting owners ( cruise )

Postby drdehave » Thu Jul 27, 2017 9:02 pm

Yeah, I knew that--just forgot. I'll re-group tomorrow... :D
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Re: Question to Sting owners ( cruise )

Postby drdehave » Sun Jul 30, 2017 4:11 pm

I’m sorry I missed the initial discussion. I was asleep. Anyway, here are my thoughts and observations, after putting 2,200 hours in my Sting S3, the last 1,100 of which were with the DUC Swirl Inconnel propeller:

1. Yes, Warmi, I would agree there’s something amiss with your S4 and it's most likely the propeller pitch. You should have better speed than that! How much better depends on your goals in consideration of the associated trade-offs.

2. In my Sting, I am sorry to say, I lack the ideal value for comparisons: TAS. I did buy a temperature gauge years ago, so my Garmin could talk TAS with me, but I’ve never installed it. The only values I can share are KIAS and KGS (ground speed; from two GPSs). On a typical windless day aloft, I easily pull 115 KGS, with 115 KIAS (or more) straight-and-level (SNL) at 5200 RPM. At 5400 RPM SNL, I usually see 120 kts or more for both of these values. During take-off climb-out at 60 kts with WOT, I see 5100-5180 RPM. At SNL WOT I always turn the obligatory 5600-5650 RPM. On days with significant winds aloft in my favor, I enjoy the “rush” of flying up to 140 KGS, usually turning just 5300 RPM, or less. Another performance marker I check regularly is this: At between 1,000 and 2,000 ft MSL, I go to WOT and enter a 95-KIAS climb. I focus on holding that 95 KIAS climb. This normally produces a climb rate of 700-900 FPM and about 5200 RPM. Try that–-just remember to hold 95 KIAS at WOT. All of these mentioned values are most often with a 300-lb load (i.e., me, fuel, & “stuff”) at about 2,000-2,500 ft MSL; and most of my take-offs are at 50-200 ft MSL (except for mountain flying, discussed later), at least around my home airport. Naturally, I experience a wide range of air temperatures here (30-112 F), but I fly mostly in mornings, so I’m usually up when it is 40-80 F.

3. Roger said it well. Your first priority should be to get that SNL WOT RPM up to where it needs to be–-at 5600-5650.

4. I would not focus too much on what you think are universal relationships between coarseness of prop pitch and either speed or take-off performance with this particular prop. Some of that thinking goes out the window. That’s because of the way it flexes, thereby mimicing a constant-speed propeller. And that’s why the DUC manual specifically says (paraphrased): “Set it to the recommended 24 degrees, then go fly it and observe the resulting performance; it is quite normal to have to do this–-and adjust pitch-–several times until you find your sweet spot.” It is also why the DUC manual cautions that this prop is subject to cavitation in various situations, including when static and during initial take-off roll. Furthermore, DUC cautions that you shouldn’t even try your ingrained “short-field take-off procedures,” where you throttle all the way up, then release your brakes. It’s counterproductive! You must instead throttle up gradually and smoothly while rolling, to get the blades flexing and “grabbing” the most possible air without cavitating.

5. That (#4) said, don’t assume that your prop is actually currently set at 24 degrees, as your logbook entry by Sportair, or whoever, may indicate. My friend here with a 2015 Sting S4 had the same 24 degree entry (from Sportair) for his DUC Swirl Inconnel, but after he experienced the same problems you have, we discovered it was actually set at 24.5 degrees (refer to my pitching method below).

6. I see no logical reasons why an S4 should be any slower that the earlier S3 model I have (at least my friend’s S4 isn’t–-i.e., if his pitch was the same as mine). In fact, I would think the newer technology might be faster, all else being equal. We lowered the pitch of my friend’s S4 closer (but not all the way) to my pitch of 23.3 degrees and got him the right combination of improved speed and climb-out performance he is comfortable with. Myself, I’m sticking with the setting (23.3 degrees) that focuses on speed, and I know I am definitely sacrificing take-off and climb-out performance for it! When we travel to the mountains together, he gets the jump on me on take-offs, but I usually edge slowly past him during cruise. I prefer to mitigate my poorer take-off performance in the mountains, especially when density altitudes are high (>7,000 ft), by foregoing the weight of a passenger. Or, if I do take a passenger along to the mountains, it’s when low air temperatures drive DAs way down!

7. You said that we have the “exact same prop.” I’m not so sure. There is a “thin” DUC Swirl Inconnel model and a “fatter” one. I have the thinner one and it really bends and reveals its stretch marks; the fatter one doesn’t show much in the way of such marks and I suspect it provides less ‘constant-speed’ effect–-and quite possibly, maybe less potential speed.

8. If you do actually have the thinner model my friend and I both have, consider that it may get faster over time. I found the critical break-in period to be from about 100-500 hours, when I continually noticed incremental speed improvement. It seemed to stabilize after about 500 hours.

9. If and when you do try to: (a) determine where your pitch is set now; and (b) begin flight-testing various adjustments to it, in search of your preferred sweet spot, I recommend you use my pitch-setting method described below. It’s specific to the DUC Swirl Inconnel prop with its very unique blade design, including that very aggressive blade “twist.” You’ll achieve more standardization, accuracy and hopefully repeatability, than if you try to follow DUC’s abbreviated and vague (in my opinion) procedures. Note that TL Ultralight allows us Sting owners to set the pitch of our props, but we cannot remove or install a prop unless we become an A&P or LSRM.

A. Use a digital protractor, such as available from Aircraft Spruce for about $100;
B. Place a small square block of wood over the bolt-heads on the propeller hub to provide a level surface, then place the protractor vertically
against the board and “zero” it;
C. Move the first blade into position for pitching on the pilot-side of the aircraft and level it horizontally, using a carpenter’s level always
placed on the same place on the stainless steel leading edge;
D. Mark the stainless steel leading edge 20 cm (7+7/8-in) inboard from the blade tip;
E. Extend a line (again, using a carpenter’s level) from that 20-cm mark vertically (i.e., perpendicular to the stainless steel edge) down the
back side of the bade and reference it with the outboard edge of a 2-inch-wide piece of masking or painter’s tape;
F. Adequately “shim up” the digital protractor (to nullify the uneven, slightly convex surface of the back side of the blade) using small strips of
Gorilla tape or other appropriate material;
G. Place the shimmed protractor on the masking or painter’s tape, with outboard edges of both tape and protractor in perfect vertical
H. Clamp the shimmed protractor in place on the blade using a small ratcheting clamp with rubber feet, such as the ones Harbor Freight Tools
I. Measure the existing blade angle (ensuring the angle-–and not its reciprocal-–is measured) or, loosen hub bolts, apply a similar, but larger,
ratcheting clamp to the root of the blade for incrementally moving it–-and begin setting a new blade angle;
J. Repeat the process for the other two blades;
K. Once all blades are set to the same angle, tighten and re-torque the hub bolts per DUC specifications. This can be a tricky, time-consuming
process to get them all just right (i.e., within 0.1-degree, or so, of each other) after final torque-down. Take your time and don’t rush it. The
smoothness of all your subsequent flight depends on it; and finally...
L. Once everything is perfect, go flying and check the performance.
(Note: After I set my pitch this way, to 23.3 degrees 800 hours ago, I took it in for a dynamic balance. The technician told me there was “nothing more he could do-–it was already as perfectly balanced as it could possibly be!” That may speak more to the quality of this prop than to my method of setting pitch, however.)

10. So, in summary, If your Sting S4 was mine, and sitting in my hangar, this would be my “treatment” regime: First, I’d measure and record the existing pitch of each of those three blades. While I was at it, I’d go ahead and check their tracking, too. Then, I’d pick a time of day and temperature that’s somewhat “standard” (that I could count on to be about the same every day) for the area, and go flying, to once again measure all the parameters discussed above in #2. Next, I’d re-set the pitch to either 23.7 or 23.5 (or, 23.3--what the heck!, as starting points), then go flying again under the exact same conditions (or as near as feasible), and record the resulting performance. And I’d keep at it until I found my particular sweet spot that also met the ‘required’ parameters. I’d do all of this myself; however, if I wasn’t already a “wrencher” and pretty well-versed on the subject, I would certainly involve a trained mechanic in the process. Good luck, and please post your findings for the benefit of the next Sting owner with the same issues!

I’m out. There’s a nice, smooth wind-flow aloft, here today. I’m going to go see if I can set a new speed-over-ground record in my Sting!

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Re: Question to Sting owners ( cruise )

Postby Warmi » Sun Jul 30, 2017 5:38 pm

Thank you for such detailed and comprehensive response.

Obviously, all of that is quite new to me ( I bought the plane a month ago ) and trying to soak as much knowledge as possible.
( even signed up for a Rotax owner/maintenance 2 day class .) so thanks again.

Looking at my propeller log-book I see the following:
Model: Duc Helices Swirl
Type: H-SW 3-D-R-I-264

Doesn't tell me much :-) beyond the fact that it is indeed Duc Swirl ( but how do I know if it is the thin version ? )

You may be right on the subject of log-book not having the correct prop-pitch record.
The plane was manufactured in late 2011 but it had only 156 hours when I bought it a month ago so it was very lightly used
( SportAirUSA was using it as a show-room , demo plane - you can actually see the plane, N6503B, in this video

So , looking at the prop log book, the very first entry from 2012 says "checked 24 degrees" , then there is another entry from 2015 stating "changed propeller pitch from 26 degrees to 24 degrees" and then yet another one in 2017 (annual ) just stating "increased propeller pitch one degree" so I guess I won't know until I verify it myself ( which I will )

Overall the plane flies very well , I am having tons of fun with it so the fact that I can only manage 105-110 knots is not a big deal - more of a
"wonder why is that" type of thing...

I am having a bit of a problem with the fuel drain valve - it looks like it is slightly leaking - basically a drop here and there , nothing serious but
I wonder if this is a known problem ?
I found a post here on the forum viewtopic.php?f=19&t=4454&p=42285&hilit=fuel+leaking#p42285 relating a similar problem\ so I will try to mess with the spring a bit and see if I can stop it.

Beyond that, everything seems to work fine , I am fortunate to have Ethanol free 91 Mogas available just 20 minutes away at another airport so I am mostly flying on that + occasionally AvGas.

One more question:
I am looking at handling oil change on my own - I watched the Rotax -owners video which looks , indeed, very easy but that was filmed with a 914 engine. On my Sting , the oil tank is stuck deep "inside" with no easy access to it ( for draining ) and it looks like I will have to take it off of the firewall completely. Will probably wait with that until I am done with my Rotax maintenance class but just wanted to confirm that this is indeed the case when changing the oil.


BTW .. How does one attache images on this forum - if I try to use the "attachments" feature, it always complains about "file being too large" no matter how pathetically small I make my jpg and png files ?
Flying Sting S4 ( N184WA ) out of Illinois

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Re: Question to Sting owners ( cruise )

Postby drdehave » Sun Jul 30, 2017 6:04 pm

No problem, Warmi, I am glad to help. In response to what you just asked:

1. Only a very small trained monkey could get to the drain on the bottom of that oil tank. Just remove the tank, every time you do an oil change.

2. To stop that fuel-sump drain valve from dribbling, do this: Lock it open before 1st flight of the day and drain about a pint into a jar while rocking the wings. This will get out bits of fiberglass debris that constantly sloughs off that composite gas tank. Then, "snap" the valve back to the closed position. This will stop the dribbling.

3. Pictures--yes, they must be downsized to, I think, 256 kb, or less. I use a picture re-sizer to accomplish that.

Also, you will no doubt find these 44 tips and tricks, for Sting aircraft, helpful: ... 7.pdf?dl=0
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