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About Turbo

  • Rank
    Advanced Member
  • Birthday 05/07/1945

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  • ICQ rthrpwll@gmail.com

Profile Information

  • Gender Male
  • Location Columbia Gorge, WA
  • Interests Avid model C, windsurfing, hunting

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Turbo's Activity

  1. Turbo added a post in a topic Throttle cables   

    I bought a 1/4" brass rod, and found that the bike cable can be securely soldered to a small hole drilled perpendicular to the rod's axis.  This allows you to make up Bowden cables of any length.  I used a propane torch, then cut the slug to length, and cut & filed off the excess cable.  I would be tempted to use leadless solder next time.  I need to make up a double-ended Bowden for my OI pump.
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  2. Turbo added a post in a topic The unquenchable EGT   

    Thanks, Nick.  That's nice and clear, unlike some other sources. 
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  3. Turbo added a post in a topic Building New Wings   

    I've got to agree with Manu here.  It would be dangerous to go beyond the span of the STOL version without a stress analysis.  In my opinion, the STOL version's airfoil has too much camber, which conspires to limit top speed.  I'm not the greatest tailwheel pilot, and am thankful for the lower landing speed with the greater span and area of the STOL  Camber does not translate directly to max lift and low stall speed, but more wing sure does.  I think you're nicely set up to get the best of both wings, cruise speed closer to the smaller speedwing, and a lower stall speed for easier landings, and improved safety if you ever need to make an outlanding when the prop stops turning.  If you have the tri-gear config, or lots of tailwheel experience, and see your bird's primary mission as getting from A to B, and fly in a place where there are lots of good spots for emergency landings, maybe the speedwing is your ticket.  This is what's so great about experimentals!  Of course, we'd all love to see some pics!
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  4. Turbo added a post in a topic Building New Wings   

    Manu, that's what I thought.  Metric sizes!  Japowell, if you decide to extend the span, make sure your span extensions are 6061-T6,, 2024-T3, or 7075-T6.  The alloy of aluminum used is important, as some are much stronger than others.  The 3 listed here are among the best.  The original design uses the first one.  It is the weakest of the 3, but is very corrosion resistent, and is safe, as the wings will take a permanent set if overloaded long before they fail.  
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  5. Turbo added a post in a topic The unquenchable EGT   

    Wow! Another clear-as-mud discourse on where to drill the damn hole!  It'd be tempting to just get a new Y-manifold with the holes pre-drilled, but for the doubtless exhorbitant price!  Isn't EGT really only about keeping the plugs clean without melting a piston?  If mine read high due to the probes being too far downstream, i reckon it's conservatve if the probe tips are centered in the ducts.  I think I'll validate the latter, then call it good enough!   Thanks for digging into this, Vance!
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  6. Turbo added a post in a topic The unquenchable EGT   

    Just to muddy the waters even more, the 1990 build manual says to drill the holes for the EGT probes 4" away from the lower edge of each flange, measured along the bottom centerline of each branch of the "Y" (this is indicated in a sketch).  It also says, in a footnote: "Absolutely precise location of EGT probes is not critical.  The attaching bands will 'effect' {affect} exact location.".  Oh Boy!  It appears likely that new things have been learned since 1990!   My probes are certainly not 38mm out from the flange center, more like 50mm.  So Vance, where did that drawing come from?  Does anybody else want to chime in here?  I've been believing that my EGTs were significant.  I was even contemplating a T-compensated digital gauge to replace my analog ones.  If location of those probes is more critical than it says in my 1990 build manual, I at very least will be more careful about keeping my EGTs away from the 1200F limit.   My probes are about 3-1/8" out from flange bottom, measured along the bottom of the Y branches on centerline.  Any further out, and the bands wouldn't fit.  . 
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  7. Turbo added a post in a topic Manu's Avid C   

    Very well done!  I look forward to your flight testing, with your improved wings, and this excellent trim installation!  I suspect that the standard Avid trim tab is bigger than it needs to be, so it will be very interesting to see if your "add-on" tab approach works adequately.  I have only a stick-force mitigation setup, similar to JimChuk's, which almost works, but there's no substitute for a real trim system..
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  8. Turbo added a post in a topic Soggy Plugs   

    My starter allows about 20 cm of line to pay out before engaging the engine.  You may have to experiment with how much line you put on the starter reel, or where you tie the knot on the starter handle.  This improves the biomechanics of starting.  
    I have an unused fine mesh SS screen filter for the fuel, which I will test for pressure drop and leave in place if it passes muster.  I will also start looking for a similar screen filter in 5/16" for the oil line.  Thanks for the heads-up.  I gotta say, though, I was not too impressed with the plastic-element Pro-Line filter.  The possibility of clogging is why I chose such a large paper filter for the oil, plus pressure drop concerns since the oil is so viscous relative to gasoline.  The oil flowrates are very low, (2% of fuel flow) however, so I can't see there being much drop thru even a paper filter.  Maybe I'll do a simple test to validate its viability.  So what is the concern?  Water in the oil tank via thermal respiration, like in an airplane's fuel tank?
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  9. Turbo added a post in a topic Soggy Plugs   

    That big paper filter will filter oil for the OI pump.  Left upstream end of tubing open for a few days, and sure enough, a bug crawled in!  First big chunk to be filtered out, I guess!
    Oh, and on the fuel system, I also have a paper filter, the smaller kind.  Tested its pressure drop at max static RPM and found it negligibly small!  Flow speeds inside 1/4" fuel line at max power are less than 10 "/sec!
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  10. Turbo added a post in a topic The unquenchable EGT   

    I was mistaken.  the 1990 version of the 582 manual states, on page 15: "Cylinder head temperatures are measured at the spark plug seat.  Exhaust gas temperatures are measured at 100 mm (3.94 in.) from the cylinder sleeve."   It would seem logical to use the flange as the reference for these probes, but no!  I had now better check the locations of my EGT probes. Thanks for the correction.
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  11. Turbo added a post in a topic Soggy Plugs   

    It occurred to me that your airframe may not have the pully and rope guide mounts welded on.  Here is a picture of mine.  They are welded on to the V-strut.

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  12. Turbo added a post in a topic Soggy Plugs   

    Hi Manu,
    My plane has a pulley allowing the pull-starter to be operated from inside.
    With this set-up it's easy to do the pull-start while seated inside the cabin.   At first I thought I had to do it from outside, but not so!  It's much easier with shoulder belt slipped down; usually I un-clip the seat belt for the start.  I push with my foot against those two slanted tubes in between the rudder pedal sets.  Effecting a re-start while flying could be challenging, though - not enough hands to fly the plane too.  Maybe if I had a better trim setup...  I'll be keen to find out how well your trim tab works.
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  13. Turbo added a post in a topic The unquenchable EGT   

    I thought the EGT probes were supposed to be 10cm out from the flange!  
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  14. Turbo added a post in a topic New prop was a flop   

    Great news!  Glad it's working out!
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  15. Turbo added a post in a topic New prop was a flop   

    One has to wonder if the prop's design twist distribution missed the sweet spot for our airplane/engine combo.  I'm thinking it may be too flat, if the smaller engines used in single-place planes turn their props faster, or these birds fly slower. Too little twist would tend to unload sections in the lower radii in cruise, making it easier to overspeed your engine, since their contributions to torque would be less.  Just a thought.  Slow airplanes, like Quicksilver, require flatter props, while faster airplanes demand twistier props.  One fact most people are not aware of is that a given airfoil shape will have a significantly higher AOA at stall (and CLx) on a propeller than on a wing, due to rotational effects.  So it may be better to have a little too much blade twist than to have too little, especially in cruise.  Flatter props will, of course, climb better.
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