Lower Wing: Aft Drag/Anti-Drag Wire Blocks and Aileron Leading Edge interference

Discussion in 'Skybolt Wings' started by fidot, Aug 15, 2014.

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  1. Aug 15, 2014 #1

    fidot

    fidot

    fidot

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    Folks;

    Modeling drag wire blocks on lower wings. Aileron well area; stations 68 1/4 and 101 1/4 seem to be problematic...

    Look at the pictures below. As you can see, with aileron deflected upward; and leading edge downward; there's interference between leading edge of the aileron and drag/anti-drag wire blocks... Double checked the dimensions; and they seem to be to plans...

    Also, I can see how blocks will present a problem for the aileron well ply trailing edge glued on those little rib tails....

    How did you guys solve this?

    .. i thought about relieving them for clearance; but it seems that that will eat away a lot of the block...

    drag-wire-blocks-1.jpg

    drag-wire-blocks-2.jpg

    drag-wire-blocks-3.jpg

    drag-wire-blocks-4.jpg

    block-dimensions.jpg
     
  2. Aug 15, 2014 #2

    cwilliamrose

    cwilliamrose

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    Are you sure the hinge point is in the right place? Looks way too low to me compared to Pitts ailerons.

    ScreenHunter_953.jpg

    ScreenHunter_954.jpg
     
  3. Aug 15, 2014 #3

    wandersen

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    Hinge point looks right, or I have mine equally wrong :).

    You need to ease off the block. I used about a 45 degree angle. You may be able to tell us the optimal angle.

    Yes - it does hit if you don't.
     
    Last edited: Aug 15, 2014
  4. Aug 15, 2014 #4

    fidot

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    Bill: ya, the hinges are where they're supposed to be, at least according to plans...

    Ward: if that won't trouble you much, can you post a close-up when you get a chance?

    Sorry guys; I know this is probably a silly question.... Im just a bit concerned about relieving 'cause of compression loads on these things..
     
  5. Aug 15, 2014 #5

    Beej

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    Better still...come see my easing off of the blocks when you drop by, tomorrow. Same as Ward describes...
     
  6. Aug 16, 2014 #6

    taff

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    This is interesting.

    Because I will be building my wings when the material comes from Steen.

    Also, the scrap wings I have (the original builder made) had this problem, I figured it was a mistake he made. (they are scrapped because of the glue and not this problem)

    Do you think this is a botched engineering issue?
    If it is then all who have made the Skybolt wings, to plan, have come across this same dilemma.

    It will be interesting to see photos of this and how folks have tweaked the blocks to accommodate the aileron nose.

    Could the leading edge (nose) be modified to accommodate the blocks rather than the blocks be sacrificed?
     
  7. Aug 16, 2014 #7

    cwilliamrose

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    I believe it's a case of maximizing the aileron's chord. The corners of the blocks don't really contribute to resolving the drag/anti-drag loads.I'd rather remove the corner of the block than disrupt the airflow at the LE of the aileron.
     
  8. Aug 16, 2014 #8

    Ed T

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    The lower edge of the blocks is normally cut to a radius to provide needed clearance. Just swing an arc from the hinge line that gives you the space you need.
     
  9. Aug 30, 2014 #9

    fidot

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    Folks,

    sooo.. now Im having another problem with that same area. After adding all the hardware, it's clear that it's way too close to the aileron leading edge. Pictures below -- top one shows what you're looking at, and bottom one is of an interest. At some aileron positions it's a touch under 1/8! And that's *not* counting fabric, extra glue Ill certainly build up when gluing things together, and, most importantly, the aileron cove cover.

    Realistically, my feeling is that the gap on finished aileron in the tightest spot should be no less than 3/32. So, counting:

    3/32 + 1/16 x 2 (fabric + paint, twice -- cove and aileron) + 1/16 (ply cove cover) = 3/32 + 1/8 + 1/16 = 3/32 + 4 / 32 + 2 / 32 = 9/32 -- more than double than what I have! I just fail to see how I can get that extra space there...

    Now, I spent about an hour browsing various threads on aileron cove -- I see Smizo and one other guy completely covered the aileron coves with Carbon Fiber and Ply respectively -- I know Beej'es are covered as well (but I haven't seen them yet Beej since Im not taking your ailerons off your plane ;) ).

    I know my ailerons are right sized, I quadruple-checked everything.

    How did you guys manage to do that?

    aileron well.jpg

    zoomed.jpg
     
  10. Aug 30, 2014 #10

    wandersen

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    Okay - looked at my wings and looked at the CAD.

    The CAD looks like the drag wires are drilled exactly on center line of the spar. They actually need to be staggered up and down 3/32" or slightly more (for 3/16" wires) so as they cross inside the spar and don't interfere. The drag wires in the aileron cove inside happen to be staggered upwards, and thus don't interfere with the aileron. Sorta magic!
     
    Last edited: Aug 30, 2014
  11. Aug 30, 2014 #11

    taff

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    Hi Ward.
    I am still trying to conjure the freekin rabbit out of the hat!
    Can't even shuffle a pack-a-cards.

    Any chance of posting a picture or three?

    One of these days I will be wrestling with the same issue :)
     
  12. Aug 30, 2014 #12

    wandersen

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    Hello Eric,

    lots of drag wire threads. Search for "drag wire" and you get 14 pages worth :D.

    Here is one

    http://www.biplaneforum.com/showthread.php?t=169

    Steen manual says the following:

    Holes for the drag/anti-drag wirels may now be drilled. Consider carefully which wire should go on top to provide maximum clearance for rib diagonals. Steen Aero Lab recommends the following layout for wire position:

    Lower Wing:
    (front) Drag Wire 2-1/4 - lug, 35-1/4 - bottom, 68-1/4 - bottom, 101-1/4 - center
    (front) Anti Drag Wire 2-1/4 - lug, 35-1/4 - top, 68-1/4 - top, 101-1/4 - center
    (rear) Drag Wire 2-1/4 - lug, 35-1/4 - bottom, 68-1/4 - bottom, 101-1/4 - center
    (rear) Anti Drag Wire 2-1/4 - lug, 35-1/4 - top, 68-1/4 - top, 101-1/4 - center

    Contrary to the Steen manual, I staggered the 101-1/4 ends to prevent interference at the wire cross-over points.

    The upper wing also has a stagger template as well. I believe I used the Steen method and it this worked well. The upper wing stagger template seems to nicely resolve the possible aileron cove wire interference problem that I didn't know I could have until today.

    Attached is a picture of the upper wing wire interference that Fidot was concerned with. Note the wire is not on centerline, but would be displaced slightly high, thus no interference with the aileron.

    001 (640x449).jpg
     
    Last edited: Aug 30, 2014
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  13. Aug 30, 2014 #13

    taff

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    Very nice.
    Thank you Ward. I feel this will help a bunch.

    Eric
     
  14. Aug 30, 2014 #14

    fidot

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    Ward,

    First thing, you mention that the CAD looks like the blocks are all drilled on the CL... you're actually looking at three different drag wires on that picture; one of them is "over", another is "under" and the third one is on the CL (see picture at the end of this post).

    Now, looking and reading more, I *think* I have misidentified what's a drag wire and what's an anti drag wire. :)

    Here's my current layout (according to how HFW has it in the Steen's notes and my understanding of which wires are drag and which are a/d):

    [​IMG]

    I was under the impression that a wire marked (1) is a drag wire. I now think it's an anti-drag wire, meaning everything should be flipped.

    Can you guys confirm please that (1) is an anti-drag, and (2) is a drag wire? That's how they're marked on a set of Firebolts plans that I have... Sorry for a stupid question here.. :(

    Now, what happens then is the orientation gets flipped - everything marked O ("over the spar CL)" becomes U ("under the spar CL"). This clears some space around the bellcrank nicely :)

    Ward -- I don't see why not use centerlines on the 101 1/4 station blocks :)

    However, this doesn't solve the aileron well problem. Aft station 68 1/4 wire block, drag wire (A) moves to "over" position, but drag wire (B) moves to "under" position. I will still have at least one "under" drag wire in the aileron bay no matter what -- and that's what is generating most of the problems. (see picture further down).

    Now, after posting last night's message, I read more threads (including Taff's very first one :) ); and the Manual section on wires, again. Not sure how I missed Randy's multiple notes on using dual jam nuts in the aileron bay area. That clears some space.

    Here's the picture. Drag wire blocks are not visible. Washers are transparent (and can be cut to fit :))

    The clearance is 11/64 now.. still very tight :(

    [​IMG]
     
  15. Aug 30, 2014 #15

    smizo

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    Because mine is an acrosport 2 and the problem doesn't really exist.
     
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  16. Aug 30, 2014 #16

    cwilliamrose

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    #1 is indeed an anti-drag wire.
     
  17. Aug 30, 2014 #17

    wandersen

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    Yes - anti-drag wire. Needed another cup of coffee.

    Ah! I do see the interference. Lower wing, station 68-1/4 outboard.

    Would it surprise you if I said - ease the washer?

    I hate to post these pictures. I had some extra Polyfiber epoxy primer left over one day and dabbed these ends (not very carefully it seems). Yes very ugly. I'm embarrassed....

    Notice that I eased both washers. However, one of the washers got repositioned incorrectly and had the very narrow gap On the side I eased and positioned correctly, I have plenty of gap. On the side where the ease on the washer in not positioned correctly, it is very tight. I don't have my feeler gauges here at home as they are at the airport. However, the gap is between 1/16" and 3/32" where the ease is not correctly positioned. I would gestimate the gap on the side that was eased at closer to a 1/4".

    (Boy those things are ugly.)

    Edit: I spent 30 minutes and repositioned the washers. I need to re-trammel the wings. After taking this apart and reassembling, I remembered a couple of additional items. Steen plans calls for a single AN970 washer. Field experience as I understand has found that these washers will cup in service and relieve drag / anti-drag tension. One school of thought is to make these washers out of 4130 0.100" or 0.125" and make them square or rectangular (thus not to interfere). I decided to just double up the AN970 washers and ease the edge. The bottom washer is eased very little. The top washer is eased a fair amount to prevent interference.

    "Measure with a micrometer, mark with chalk, cut with an ax..."

    002 (640x491).jpg

    004 (640x480).jpg

    005 (640x480).jpg

    003 (640x480).jpg
     
    Last edited: Aug 31, 2014
  18. Aug 30, 2014 #18

    raymoeller

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    From the stearman.net:

    The names of “Drag Wire” and Anti-Drag Wire” are fairly self-explanatory. Drag wires run from a point inboard and forward in a bay to a point outboard and aft. In this position, the Drag wire is there to RESIST drag forces that would tend to pull the wing tips aft as the airplane travels through the air. Anti-Drag Wires oppose the drag wires running from an inboard aft location to an outboard forward point in its bay. As the name indicates, these anti-drag wires oppose forces in the reverse to the direction of flight.

    So, the way I'm reading fidot's drawing, wire 1 is running from the front spar at the wing root to the rear spar in an outboard direction... would make it a drag wire.. right?
     
  19. Aug 30, 2014 #19

    fidot

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    Bill: thank you. Is there anywhere where there is a standard definition? Am I failing at Google? :)

    Ray: Yes! I used the same exact description and it made sense. However, Firebolt plans (which are essentially "skybolt screwed up") have them exactly the opposite, with (1) being marked as anti-drag. :confused::confused:

    [​IMG]

    Smizo: haha :)

    Ward: Thanks for posting pictures. I see what you did now. You have the blocks inside the aileron well, and cover being closer to the rear spar, with cutouts. Question: are you planning to leave them as is and just stick fabric around them, with cutouts as well?

    That's the backup plan for me as well -- but what I am hoping to achieve is what's on the picture below.This is a very rough sketch (grain's oriented all wrong too, i know) and the drag wire blocks need to be profiled more, and the curvature itself changed, but it shows the idea, with all the drag wire HW hidden behind cove cover. Only the hinges will protrude. Sorta like what Manuel Benito describes in his post here.

    The reason Im planning this now is Im considering modifying aileron well ribs' section aft of rear spar rear edge to become a support for that ply, essentially being a single piece of 1/4 ply 'tail block' curved to accept that plywood cover rather than capstrip buildup. Gotta decide before I start making those ribs ;)

    [​IMG]
     
  20. Aug 31, 2014 #20

    cwilliamrose

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    It seems I have had the definition wrong for long enough I'm not sure I can correct it. I'm doomed.
     
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