Trimming 6" of edge off horizontal stabilizer and elevator

Discussion in 'The light stuff area' started by blane.c, Dec 14, 2018.

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  1. Dec 14, 2018 #1

    blane.c

    blane.c

    blane.c

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    See attached below, Fuselage Tube 4" dia. Total width from outer edge to center fuselage tube is 50" (12.25"+12.25"+12.25"+10"+1.25"+2"). Total width of tail 100". Total width of trailer to put it in, inside dimension 90". Bracing cable attaches 11" from outside edge each side.

    What is best way to trim off 6" from each side? Does the loss of area matter? Could the area trimmed off be compensated for by the addition a trim tab?



    Flyer Horizontal Stab..jpg

    Thank you.

    P.S. the 1 5/8" dimensioned is 3/8" short of the center of the fuselage tube.
     
  2. Dec 14, 2018 #2

    pictsidhe

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    Long story short, changing the area does matter. increasing the chord to compensate seems prudent to me. The lower aspect ratio will slightly change the tail behaviour, so you may want to over compensate a bit.
     
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  3. Dec 14, 2018 #3

    Topaz

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    All of what pictsidhe said, plus the fact that adding additional trim-tab area will increase control forces slightly, as well as loads on the hinges and control system due to the increased elevator area.

    Any chance you can just install 5" 'bulges' in the trailer sides, to accommodate the tail? You're flying the airplane, not the trailer, so personally I'd be modifying the thing upon which my life does not depend.

    Change the trailer, not the airplane.
     
    Last edited: Dec 14, 2018
  4. Dec 14, 2018 #4

    lr27

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    This will make your aircraft less stable in pitch. You're reducing the area, plus the shorter aspect ratio means the lift curve isn't as steep. If you haven't already built the tail, you could make up for it by increasing the area to more than it was before. If you have built it, perhaps a couple of end plates can make up for the lost area and span. Or it may be that the stab was larger than necessary. Besides the change in pitch stability, it seems possible that stall and spin behavior might be affected.

    I don't suppose you could fit the aircraft into the trailer with a 30 degree bank, could you?
     
  5. Dec 14, 2018 #5

    lr27

    lr27

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    P.S. Due to the increased forces Topaz mentioned, it might be best to add the increased area to the fixed part of the stab only. That elevator looks pretty generous already. But of course you're still making major changes to the aircraft.
     
  6. Dec 14, 2018 #6

    BoKu

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    In California, and probably most of the US, anything over 8' (96", 2.44m) constitutes a wide load subject to various restrictions. So I'd do that only as a last resort.

    Me, I'd test fly it with the shortened stabilizer, but be prepared to fabricate a full-span stabilizer if I encountered abnormal or undesirable flight characteristics.

    Or maybe better yet, re-engineer the stabilizer to make it easy to remove or fold.

    --Bob K.
     
  7. Dec 14, 2018 #7

    Topaz

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    Good catch. It didn't register with me that the span is more than legal road width.
     
  8. Dec 14, 2018 #8

    FritzW

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    Joe (RockDog) did that on his Legal Eagle (about 6:15 in the video). Hopefully he'll jump in and comment.

    ...I admire Joe's ability to build and fly stuff using common sense instead of getting bogged down in theoretical problems.

     
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  9. Dec 14, 2018 #9

    Dana

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    What aircraft?

    Probably it would be fine, assuming the it was designed with a reasonably static margin. If anything you might run into trouble at the aft end of the CG range. The way the fixed stab comes to a point, you're not losing all that much area. But if it were me, I'd swing the leading edge forward (so it doesn't come to a point) to keep the same area.
     
  10. Dec 14, 2018 #10

    Victor Bravo

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    The aircraft appears to be a Kolb Flyer. So it is entirely possible for you to use the (later) tail folding mechanism that Kolb used on the Firefly, Firestar, and all other Kolbs after the Flyer. This is a better solution than shortening the tail span.

    The good news is that Bryan and Helen will be glad to provide you with those parts form thefactory so you don't have to weld them. All you need to do is call and ask Bryan what you need to fold the tail on the Flyer like a normal Kolb.
     
  11. Dec 14, 2018 #11

    wanttobuild

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    You can legally pull a 102" wide trailer most anywhere.
    Anywhere you see a semi traveling you can roll
     
  12. Dec 14, 2018 #12

    pictsidhe

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    A few states only allow 96"
     
  13. Dec 15, 2018 #13

    Norman

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    If the hinge gap in the plans is open sealing the gap may increase elavator athority more than what you will lose by cutting off the tips.
     
    Last edited: Dec 15, 2018
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  14. Dec 15, 2018 #14

    Rockiedog2

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    TY Fritz. redneck engineering.
    Yeah I clipped my LEU horizontal stab and elevator for same reason. legal trailer width. The LE has a large tail already so I wasn't much concerned about it and it turned out fine. Also the LE had a gap between the H stab roots and I filled that at the same time so didn't lose any HS area but the elevator was smaller. Couldn't tell any difference. I wouldn't hesitate to clip that pointy stab on your plane but yeh the elevator will lose a little. Dunno if that will matter or not. If it was me I'd do my homework best I could and if didn't run into anything alarming would clip it and see what I got. You can always set it up so you can mount a "tip" on each side after you get it outa the trailer in case it doesn't fly like you want it to. Rig it up so you can insert a tube in the HS spar end and the E spar end and build off that fwd and aft. A few screws/clip plates in the end ribs type thing. Quick detach.Another way you might think about is rather than redo for a whole folding tail just clip the HS and E and piano hinge attach a folding tip that folds back into place and secures with several attaches. Or maybe insert a tube thru the tip into the HS and E spar to hold it. Thre's a simple way.
     
    Last edited: Dec 15, 2018
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  15. Dec 15, 2018 #15

    blane.c

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    Yes Kolb Flyer, Either folding or removing HS is a possibility. 102" wide trailer is highway use only which is restrictive.
     
  16. Dec 15, 2018 #16

    blane.c

    blane.c

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    On Rockiedog2's LE there are two flying wires on each side, on the Kolb Flyer one flying wire each side. With the leading edge of the HS landing on a member with a flying wire, if I clip off the triangulation I am afraid the moment on the leading edge will cause the leading edge to twist. I think it is a change one thing change everything scenario, I would have to re-attach the leading edge out at the tip and this would further reduce the area of the HS, so I would need to push the inboard edge forward to compensate. A lot of change for a little width.
    I am not as concerned about the elevator, make the tip removable or foldable or a little longer it has different forces acting on it.
    The folding kit from Kolb may be the wisest as it is factory.
     
  17. Dec 15, 2018 #17

    Dana

    Dana

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    Take a look at the Ultrastar drawings in the KolbUltrastar Yahoo group, basically just a piano hinge as the fuselage tube to stab attachment, and bolts with wingnuts (and safety pins) to connect the elevators and the lower wires.
     
  18. Dec 15, 2018 #18

    blane.c

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    I have those drawings in my 'puter, I'll look more closely.
     
  19. Dec 15, 2018 #19

    Dana

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    The only thing I'd change if going that route is to connect the elevators like they do on the Firestar, sort of a universal joint. On the Ultrastar, after you unfold, you have to install a clevis pin to tie the elevator horns to the bellcrank at the back of the boom tube.
     
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