Welcome! Becoming a registered user of ShortWingPipers.Org is free and easy! Click the "Register" link found in the upper right hand corner of this screen. It's easy and you can then join the fun posting and learning about Short Wing Pipers!

Page 2 of 20 FirstFirst 123412 ... LastLast
Results 11 to 20 of 200

Thread: Rigging

  1. #11
    Jinkers's Avatar
    Join Date
    Feb 2008
    Location
    Greeley, CO
    Posts
    193
    Post Thanks / Like

    Default Re: Rigging

    Not so much you need a "ShortWing Guru" as you need a "rigging Guru".
    Any one know one of these in or near Colorado?

    Thanks,

  2. #12

    Join Date
    Dec 2007
    Location
    Upstate New York
    Posts
    900
    Post Thanks / Like

    Default Re: Rigging

    Ahhh, the things we as otherwise "thinking people" can find that we have never "thought about". Ain't life Grand?

    Scott; sorry, can't help with that...Colorado is just a teeny tad outa my stompin' grounds. Someone will know somebody, wait and see. Probably you should ask other pilots locally, and see who's name gets thrown around the most.

  3. #13
    Tadpole's Avatar
    Join Date
    Apr 2009
    Location
    Franklin, IN
    Posts
    651
    Post Thanks / Like

    Default Re: Rigging

    Quote Originally Posted by Jinkers
    Not so much you need a "ShortWing Guru" as you need a "rigging Guru".
    Any one know one of these in or near Colorado?

    Thanks,
    I'll check down here in the Springs. I know a mechanic that I truly trust and he's rebuilding a Tripe. I'll see if he's a rigging guy or not.

  4. #14
    Andrew K's Avatar
    Join Date
    Apr 2008
    Location
    Dallas, TX
    Posts
    154
    Post Thanks / Like

    Default Re: Rigging

    I am wanting to check the rigging on my plane this weekend after reading this as I seem to be having to be (what I believe) an excessive left turning tendency described in some of the posts and have a question regarding the washout.

    When you measure the washout with the wooden block are you trying to have the same angle of incidence as the wing root measurement displayed on the level when the wooden block contacts the wing and level at 30 inches/rear spar?

  5. #15

    Join Date
    Dec 2007
    Location
    Upstate New York
    Posts
    900
    Post Thanks / Like

    Default Re: Rigging

    Quote Originally Posted by Andrew K
    When you measure the washout with the wooden block are you trying to have the same angle of incidence as the wing root measurement displayed on the level when the wooden block contacts the wing and level at 30 inches/rear spar?
    No. The angle of incidence "of the wing with 2 1/2 degrees of washout" is built into the wing butt attach ("wing hinge") fittings, "fixed" and at the design number of degrees to the "HRL" (the Horizontal Reference Line) of the aircraft, "as lofted". More than "just me" [here] know the actual AOI that Piper used, and it is easily "found" in the Drawings, but if you are going to "follow the instructions", you can do nothing except "confuse yourself accidentally" -OR- "learn for yourself" that the "real and true answer" is totally NOT germaine to Rig. In truth, you APPEAR to be looking for a "shortcut" that isn't really there...You HAVE TO "level the airplane" to do a proper rig (OR "rig check"). When you do THAT to get your "HRL" to "work the way you want to go" to see for yourself why the answer is "no"... well, you OUGHT to be just taping the block on one end of your level.

    Here's the equivalent of the "shortcut" you seek: DON'T "cut a piece of two-by-four" to be 1 3/8" "tall". Use a "chunck" of 2X4 that is the "full 1.5" thick". On the OTHER END (the _ZERO END" of the "zero to 31 in" gap on the level") tape a garden variety El Cheapo wooden "paint stirrer" stick. I have NEVER seen one "far enough off" of being 1/8" thick to make a difference that you can resolve with the naked eye on the spirit level. The paint stick, you can "snap off" in a vise, and your "2X4" pice can be 1" to [as long as you can hold up].

    There is NO NEED WHATSOVER to "shoot your wing root" for rig. IF it IS "wrong", you aren't going to fix it unless you put in in a known "right" jig and reweld the hinge fittings on. All you can do ANYWAY is to "rig out the "mistake". So "stay away fron the AOI, unless you WANT to make your head hurt.

    DO NOT avoid "leveling the aircraft" because you think that is UNnecessary. It IS necessary, because there is NO OTHER WAY to check the rudder post (hinge line) and the horizontals, for being "Plumb", and "Level" (in other words: RIGGED CORRECTLY). Nine times out of ten, if whomever originally rigged it was "GOOD ENOUGH" to have set the empennage "square" correctly, you get a real good chance that the whole rig was correctly done. TOO BAD MOST of the "out of rig airplanes" that I have dealt with... NOTHING was "close", from start to finish. There are only TWO possibilities for this being true, either the airplane has taken some kind of HELLACIOUS WHACK to the airframe...or... it was done by someone that SHOULDN'T be doing "Friggin' an' Riggin'".

    One thing you can pretty much "take to the bank"...if the LAST GUY that rigged (or "re-rigged") your airplane did NOT place a legal logbook entry in your logs...Then I don't care HOW MANY YEARS he's been doing it [wrong!], he shouldn't be doing it. (Same line of thinking...you could only "count on" it having been done IF it were signed for. Sorry if I have stepped on ANYONE's TOES about this -but- no matter HOW "Professional "he" may be, if he was conscientious and careful about rigging the airplane RIGHT, he should have been PROUD that he did it, and put his name to the signoff. If it ISN'T in the logbook, it either wasn't done correctly, or else... IT WASN'T DONE!)

  6. #16
    Administrator Steve Pierce's Avatar
    Join Date
    Nov 2007
    Location
    Graham, Texas, United States
    Posts
    15,454
    Post Thanks / Like
    Blog Entries
    1

    Default Re: Rigging

    Quote Originally Posted by Andrew K
    When you measure the washout with the wooden block are you trying to have the same angle of incidence as the wing root measurement displayed on the level when the wooden block contacts the wing and level at 30 inches/rear spar?
    Yes, the block is the amount of twist the wing should have.

  7. #17
    Kurts's Avatar
    Join Date
    Jun 2008
    Location
    Roseville, CA
    Posts
    390
    Post Thanks / Like

    Default Re: Rigging

    Funny. Same question, one guy answers No and the next answers Yes... Ok which is it?

    It would make sense to me, a long time R/C model airplane builder/rigger, that if you checked the angle of the underside of the wing at the wing root, then attached the block to the level and placed the level in the appropriate spot outboard on the wing, that if the washout is set properly the level will read the same in both locations.

    The question was also posed as to whether or not changing the amount of washout would affect performance and to what degree. This wasn't answered that I saw. It would seem to make sense that the greater the washout the greater the drag but also the better the stall characteristics (up to a point).

    It also brings up the question with me of the proper setting of the TE of each aileron. On my Colt, both ailerons droop below the TE about 1/4". This should give the effect of slightly more lift as well as more drag. If the ailerons were both reflexed up slightly I would expect to see a bit more speed at the expense of a slight loss of lift. My airplane requires left rudder in cruise or else the ball will hang out about half a width to the left. It also then requires right aileron to keep the wings level, so it's in need of some professional help in the rigging dept. It also does decent, coordinated steep turns to the left but requires opposite aileron in a steep turn to the right because if you center the ball and the ailerons while in the turn, the bank angle keeps increasing. Weird...

    It would be interesting to have data on "fast" PA-22s vs "slow" ones to know what their dihedral, washout, and aileron droop settings are. We might be able to come up with the ideal settings if we had some good data collection because I'd be surprised if Piper's boys didn't draw this thing out in chalk on a garage floor (ala Benny Howard) and use the "TLAR" (that looks about right) method!

    Kurt
    63' Colt

  8. #18

    Join Date
    Dec 2007
    Location
    Upstate New York
    Posts
    900
    Post Thanks / Like

    Default Re: Rigging

    [quote=Steve Pierce]
    Quote Originally Posted by "Andrew K":1sgcgk2x
    When you measure the washout with the wooden block are you trying to have the same angle of incidence as the wing root measurement displayed on the level when the wooden block contacts the wing and level at 30 inches/rear spar?
    Yes, the block is the amount of twist the wing should have.[/quote:1sgcgk2x]

    Steve did not answer the question that was asked, and I did. Steve says that the block is the amount of TWIST THE WING SHOULD HAVE. Steve is correct! It is, but the question WAS involving the "Angle of Incidence", the answer to which IS, IN FACT..."No." which is totally unrelated to the otherwise "correct answer" that Steve supplied (which is an actuality, for a different question. Steve was in error for answering a question NOT asked". Neither answer is "incorrect". Mine is "necessarily long, and complete" and relates directly to the question as asked. So, neither of us was wrong...although his "Yes" is in one respect wrong, since the question was "ill stated" and my "No" correctly speaks to the mistake implied. This "question" illustrates nicely how MANY PEOPLE do NOT understand the definition of Angle of Attack, versus Angle Of Incidence. AOI is FIXED and unchangeable in almost every aircraft design, while washout or wash-in is adjustable in MOST designs. AOI is almost ALWAYS defined at a certain degree "positive" AT THE ROOT, and "Washout or wash-in" is defined as a specified change of Angle of Attack "across a wing's span".

    YOUR question, Kurt, also "ignores the difference between AOI and AoA", The AOI of the ShortWings is ONE DEGREE [positive] at the root. The wash out is [plus] 2.5 degrees ACROSS THE SPAN. YOU "perpetuate the mistake" in your reply "...that if you checked the angle of the underside of the wing at the wing root, then attached the block to the level and placed the level in the appropriate spot outboard on the wing, that if the washout is set properly the level will read the same in both locations." Sorry, you are mixing your peanuts and your bananas. Your measurement at the root (because of the "hinge fittings" being welded in with the wing ROOT of ONE DEGREE positive to the Horizontal Reference Line during assembly). The "height of block" Piper recomends in the Riggin Instructions TAKES INTO ACCOUNT that referencing this by settin up the spirit level AT THE PRESCRIBED LOCATION will resuylt in your settin up the PROPER 2.5 degree washout. This, to me, is a TERRIBLE MISTAKE that people without a FULL UNDERSTANDING of what they "Are actually doing" with a digital "level", or "protractor", as opposed to "the Math that Piper did FOR the "Rigger in the Field". A little bit of knowlege is a very "dangerous thing". MOST PEOPLE (unless they ARE IN FACT "as smart as they believe themselves to be) should "Stick with" the "simplified procedures" (along with the "antique tooling" that Piper was dealing with!

    The "One Guy says one thing, and the Other says the other"...is an incorrect evaluation. I'm genuinely sorry, but Kurt, you missed a very important
    fine point". While I believe Steve to have answered "honestly" and believed his brevity "fully answered" the question, I unfortunately disagree. Steve MAY HAVE "oversimplified" his correct answer... but I THINK he MAY HAVE "missed" the tying together of the AOI and AoA, incorrectly.

    I don't actually SEE your "other two questions" to exist in the "question posed", but they are valid, "as your extensions" of the question. The aileron "droop" is an issue I have spoken to many times over the years, in recommending how to rig the ailerons. Actually , I "openly challenge" ANYONE to Post any "true and correct" rigging proliferated data from Piper, specifically for PA-15, 16, -17, -20 or -22 airplanes. I have NEVER found a Piper "cable tension setting" published for these airplanes. Only "earlier" or "later" Piper models. I cannot "subscribe to" the common belief that the cable tensions claiming THESE TENSIONS to be being CORRECT for the ShortWings! When the ailerons are rigged "looser than the specified tension" (which are "specified WHERE, for -15s through -22s, again"???) so that they "feel silky", and then are rigged 1/8 to 1/4 inch "drooped" statically, then they will "fly up" into trail when the airplane is AT CRUISE. I have PROVED THIS on every single airplane I have EVER rigged.

  9. #19
    Kurts's Avatar
    Join Date
    Jun 2008
    Location
    Roseville, CA
    Posts
    390
    Post Thanks / Like

    Default Re: Rigging

    Man my head hurts...

    The original question by Andrew mixed terms up a bit but we know what he was asking and Steve's answer accurately answers the question that was intended to be asked. What might have been a better way to ask it, rather than:

    "When you measure the washout with the wooden block are you trying to have the same angle of incidence as the wing root measurement displayed on the level when the wooden block contacts the wing and level at 30 inches/rear spar?" is:

    When you measure the washout with the wooden block, are you wanting to see the same reading at the wing root as you do when the wooden block contacts the wing and level at 30 inches/rear spar? And the answer to that is yes.

    AOI doesn't matter because the fixtures are welded to the fuselage. We know what AOI is, but in this case it's moot. Whether that is 1 degree of positive incidence or not, we can't change it. What we can do is measure the angle of the bottom of this flat-bottom airfoil at the wing root using a long piece of metal placed against the front and rear spars the way Steve showed in his first picture. It makes no difference at this point if the aircraft is level or not, it could be pointing straight up for all we care because at this point we are only checking the wing's washout angle, and I am only talking about checking the washout of the wings, not rigging the entire airplane. Why would I only want to check it? Because my airplane flies funny and I want to see if unequal washout angles could be contributing.

    Service Memo 20 says:

    Wash Out: Place a 1-3/8 inch block under the wing at the rear spar location at the
    outboard aileron rib. Place a 30 inch level chordwise across this block with the front end
    of the level at the front spar location. The bubble will center if the wing has the proper
    2-1/2 degree washout. Adjust the rear lift strut forks in or out to bring the bubble to
    center.


    This can be interpreted as meaning there should be 2.5 degrees of twist in the wing (washout, which causes the inboard section of the wing to stall before the outboard section because the outboard section will fly at a lower angle of attack to the relative wind). This 2.5 degree difference should be from the wing root to the outer aileron rib if you use the stated 30 inch level with the end at the front spar location.

    You don't need the block, you don't need the aircraft to be level. Measure whatever angle is at the wing root and check to see if the angle at the outboard aileron rib is 2.5 degrees different using a digital level or an analog angle meter. Why would Piper say to use a wooden block with the aircraft level? Maybe because you can't accurately check degrees using a bubble level without the aircraft itself being level and a properly placed block of 1-3/8" wood to fool the bubble. You can however with modern digital levels du jour and so that negates the need for a block of wood. Isn't technology great?

    Kurt
    63' Colt

  10. #20
    Gilbert Pierce's Avatar
    Join Date
    Nov 2007
    Location
    Germantown, Tennessee 01TN
    Posts
    4,427
    Post Thanks / Like

    Default Re: Rigging

    Great explanation Kurt,

    I used a machinist bubble level with the airplane not leveled once in accordance with your explanation. Saved a lot of time since all I needed to do was check the washout. I had changed the rear struts and needed to verify I set the length the same as the old ones.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •