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Skunkworks85

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About Skunkworks85

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  • Location
    Illinois
  • Interests
    Engineering, Cars, Planes.
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  1. Skunkworks85

    3D Printed (FDM) Cabin Plugs

    First Set have been sent to Andy A. Looking forward to hear his review. Any others interested, Send me PM. Thanks
  2. Skunkworks85

    CTSW Cruise Speed

    Any guesses at what max climb rate could be on lets say a standard day/altitude?
  3. Skunkworks85

    CTSW Cruise Speed

    Rodger, Have you every set up a propeller for max climb tests? Say for instance, for a STOL competition? If so, what kind of FPM could one expect to see?
  4. Skunkworks85

    3D Printed (FDM) Cabin Plugs

    A wise man once said: Yes, Clear tape is just a functional, But I do not prefer the unfinished/hillbilly solution. These Plugs do pop out with a little grab handle very easily for inspection. I do not see a need to have instant sight of the linkagages. I am working on a plug for the sight gauges with an epoxied in clear window.
  5. Skunkworks85

    CTSW Cruise Speed

    According to Doug Grays, Published academic paper on the matter. This method has been published in many circulars. Using the triangle method, 120 degrees (1/3 of 360) is the max difference you should use between tracks, in order to equal the uncertainty level of the GPS unit itself.
  6. Skunkworks85

    CTSW Cruise Speed

    That is the benefit of the adjustable pitch prop. and mostly what it is used for today. But if you have an engine that can maintain a set RPM regardless of how coarse the prop gets, you will in fact, increase in speed. you are referring to the efficiency of the prop. adding coarseness to the prop to reduce engine RPM to save fuel. My original statement is true. if a prop stays at one speed, a fine pitch will be better for climb and coarse will be better for speed.
  7. Skunkworks85

    CTSW Cruise Speed

    Rodger, I know you are a respected member of the community, and I do like hearing your information, as some of the things you claim can only be learned from lots of experience. but, It is really hard to follow you, Would you agree with, There is an optimal pitch for climb, and on the other end of the spectrum there is and optimal pitch for cruise? These 2 pitch settings are at the opposite ends, and any change in one will directly and adversely effect the other? IF that statement is true, How can you claim that there is a magical pitch that will improve both speed and climb performance relative to whatever current pitch is on the aircraft? Saying "I tested it" does not prove the theory. Although I am convinced you believe you are correct. The physics of the matter say otherwise. And for this reason alone, is why in-flight adjustable props were invented. There is probably one universal pitch on the CT aircraft that averages the cruise and climb of the 95th percentile of all CT's made. And that maybe the pitch you use. Does it make it the right one for everyone? What was your control group for all your testing? What kind of metrics did you record? When comparing aircraft to aircraft was there more than just One variable changed? Or is is possible one weighed a little more? had more aft cg? had some glider tape in different locations? trimmed differently? ect? Being and engineer, I subscribe to, "In god we trust; all others bring data"
  8. Skunkworks85

    CTSW Cruise Speed

    Rodger, That makes sense due to the fact at some point the flap will turn into a spoiler. Since you have done the testing, can you provide the empirical data showing at what degree of reflex is ideal for least amount of drag? Do you have data for the combinations you tested? Obviously, WOT speed is going to be constrained by the operating limitations of the engine. Since peak torque is where peak volumetric efficiency happens and ηv=Va/Vd Where Nv = Volumtric Effiviency Va= Actual filling of cylinder Vd= theoretical (calc) filling of cylinder Since Va is effected by density altitude, and peak torque follows peak VE, this would scale back the toque curve of the above graph. or lower the RPM where peak torque happens. This is mathematically known because VE is always higher than the torque curve to the left and right of where they meet. Since or propellers are fixed(in flight) it would stand to reason, that max speed would happen 5800 rpm at full throttle, and wherever your prop of choice is pitched to achieve that, climb performance will be a function of propeller efficiency and where that ended up along to torque curve. This stands to reason that since we see ≈4800-5000 rpm at max climb,(below peak torque) a variable pitched prop would be a great benefit for climb performance. I believe that Ed may be on to something operating at high density altitudes, as the lower RPM's for him would account for optimized use of the power band he has available.
  9. Skunkworks85

    CTSW Cruise Speed

    I will check it out this weekend, One point to note is that when I cruise, I put the flaps in the "manual" mode which allows for what I am guessing is 2°-4° extra of reflex. I will confirm the extra reflex angle too.
  10. Skunkworks85

    CTSW Cruise Speed

    I dunno, Never tried it.
  11. Skunkworks85

    3D Printed (FDM) Cabin Plugs

    I can do the set for $60 plus shipping. Maybe send a set to first verify fitment, as I question the variation of air frames due to large amount of manual lay-up work in these planes. I will print up a set, Possibly send a set to Andy A (First to respond) so we can get some feed back on fitment/quality.
  12. Skunkworks85

    CTSW Cruise Speed

    Headed right to the airport after work today, Using Doug Gray's method for determining true air speed based on GPS ground speed. Used the excel file available online, the math looked sound, and looks like a largely accepted method for doing this experiment. My 3 Tracks: 180,45,270 at 3,000', I flew 5 mins on each track and recorded the GPS ground speed readings at 30 second intervals, Averaged the results and input them into the calculator. Used the AP for steering. 17 gals in the plane before take off At 5100 rpm, calculated TAS was 126 KTAS Repeated the test at 5400 rpm and yielded at 128 KTAS I also noted the dynon read out of TAS and the 30 sec intervals, and interestingly it showed 4.5 knots faster at the 5100 rpm, and 2.1 knots faster at 5400 rpm. Maybe something to do with the prop wash over the static port at the higher RPM? From Doug Grays paper "Roughly speaking provided the three tracks differ from somewhere about 90° to 120° then the resulting error in TAS will be of the same magnitude as the error in the GPS Ground Speed. An error in GPS speed of ±1 knot and ±1° in track will result in a corresponding error of about ±1.3 knot." Regardless, I am impressed with this, and I am glad I did this test. and i can confidently say that my true airspeed is 126 ±1.3 knots at 5100 rpm and 128±1.3 knots at 5400 rpm. This also shows the cost/ benefit of sucking down another half gallon/hour for 2 knots. FWIW, the latest W&B in my plane states 749lbs. Wind calm tonight . Screen shot of calculator.
  13. Skunkworks85

    3D Printed (FDM) Cabin Plugs

    Using my STL file, I did some online quotes for a 3rd party to print the plugs, that averaged $80-$120 for a set, at a 0.10mm resolution (same resolution I print at) Printed in PETG material. What would you consider a fair price on a set?
  14. Skunkworks85

    3D Printed (FDM) Cabin Plugs

    Sure thing, Just to be clear, all I have designed at the moment are the 2 forward linkage plugs.
  15. Skunkworks85

    CTSW Cruise Speed

    That makes sense, and I will do that test. FWIW I was comparing the Dynon numbers with the winds aloft charts and they were within 10% I will plot a course in the GPS and set up the experiment as described. Thanks Tom!
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