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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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 Posted: Sun Mar 23, 2008 3:33 pm Post subject: Ultrastar questions |
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I bookmarked some old posts about potential problem areas on the Ultrastar,
which led to some questions as I was doing a pre-season inspection of my plane:
From message #35056 by John Hauck:
| Quote: | Lateral bracing can be broken by vibration during flight,
mishandling on the ground, catching a wingtip on the ground as the
result of a less than level landing or bending and/or breaking a
landing gear leg. To check the inside of a wing that does not have
inspection plates installed, cut a couple small slits in the inboard
rib fabric. One to look through and one to shine your flashlight
through. Should be able to get a good look at all bracing and other
important parts in the wing.
The 5/16" aluminum tube lateral bracing in the older Kolbs is prone to
breaking at the point they are bent to marry up with the main spar and
the leading edge tube.
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I cut the slits and looked inside today. I was happy to see that
everything looked good, and that the later drag strut modification had been
installed on my plane. I'm a little unclear, however, just what parts are
meant by "lateral bracing". The internal diagonal bracing in the wing
ribs? Or something else?
From message #17821 by Richard Swiderski:
| Quote: | Re: safety alerts on UltraStar: The front pivot arm that operates the
belcrank has a notice to be reinforced. There has been cases of it
cracking. this is the vertical arm that has a pushrod attatched to it that
drives the bellcrank. A triangular tab was to be welded to it at its base.
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I'm not clear which pivot arm this is. I assume it's the arm that
transfers the vertical motion of the lower aileron pushrod to fore-and-aft
motion of the upper pushrod (that in turn drives the bellcrank that droves
the two rear aileron pushrods)? Does anybody have a drawing or photograph
of what it should look like after modification?
From message #36046 by Richard Swiderski:
| Quote: | If yours is a very early model, make sure it has a steel collar on
the inboard end of the wing spar, much like the collar at the front end of
your boom tube. The purpose is to keep the spar from going oval when torque
from aileron input is applied. It makes a big difference in handling.
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This, I _don't_ appear to have, just the internal steel bits that attach to
the universal joint. Is this a safety issue, or just a handling one? I
don't appear to have any roll authority issues (though I have nothing to
compare it to), but I _do_ have a sleeve that joins the front spars
(leading edge tubes) which would tend to help keep the wings from twisting.
While I was at it, I moved the rudder cable attachment higher up on the
pedals so I can get full rudder deflection with less foot motion (I find it
uncomfortable and have been meaning to change this for some time), and
fixed some previous owner's strange interpretation of how the seat belt
should be attached. Need to get a few more bits to get the auxiliary tank
installed, have to raid the aluminum stock rack at work tomorrow...
-Dana
--
New safety announcement from the Department of Homeland
Security: Securely duct tape shut any books you may own about civil
liberties or the U.S. Constitution.
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jb92563
Joined: 23 Mar 2007
Posts: 314
Location: Southern California
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| Posted: Mon Mar 24, 2008 11:49 am Post subject: Re: Ultrastar questions |
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Hi Dana,
Do you have a complete list of UltraStar concerns/bookmarks available?
I'd sure be interested to see what else you found.
I will note those and check them out.
The diagonal bracing is a couple tubes that attach to the leading edge at one end and are attached to the Main tube spare at the other forming a triangle between the main spar tube, a rib and the diagonal brace.
They prevent the leading edge from moving towards the tip or root directions from vibration, uneven skin covering tension spanwise, flight loads and rough ground handling.
Your sleeve connecting the two leading edges might help that some if clamped tight.
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_________________
Ray
Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider
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ez(at)embarqmail.com
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| Posted: Mon Mar 24, 2008 1:19 pm Post subject: Ultrastar questions |
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On Mar 24, 2008, at 3:49 PM, jb92563 wrote:
| Quote: | Your sleeve connecting the two leading edges might help that some if
clamped tight.
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On the other hand, if you ever develop even a slight bit of play in
your wing attach points you will
put "extreme stress" on those critical little diagonal braces inside
your wing.
Are you sure that is what you really want to do?
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Mon Mar 24, 2008 2:05 pm Post subject: Ultrastar questions |
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At 03:49 PM 3/24/2008, jb92563 wrote:
| Quote: | Do you have a complete list of UltraStar concerns/bookmarks available?
I'd sure be interested to see what else you found.
I will note those and check them out.
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Well, the messages I was referring to were the only ones I bookmarked
addressing specific concerns.
| Quote: | The diagonal bracing is a couple tubes that attach to the leading edge at
one end and are attached to the Main tube spare at the other forming a
triangle between the main spar tube, a rib and the diagonal brace.
They prevent the leading edge from moving towards the tip or root
directions from vibration, uneven skin covering tension spanwise, flight
loads and rough ground handling.
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Yes, I understand that. I wasn't sure if that's what John was referring to
as "lateral bracing".
| Quote: | Your sleeve connecting the two leading edges might help that some if
clamped tight.
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No, that provides no spanwise support. I imagine it was originally
installed to support the center gap seal, but it would also tend to prevent
relative vertical motion of the leading edges (i.e. wing twist).
-Dana
--
Work is underway on drafting a new constitution for Iraq. Why don't we
send them ours? It worked for 200 years, and we don't use it any more.
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Mon Mar 24, 2008 2:17 pm Post subject: Ultrastar questions |
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At 05:16 PM 3/24/2008, Eugene Zimmerman wrote:
| Quote: | On the other hand, if you ever develop even a slight bit of play in your
wing attach points you will
put "extreme stress" on those critical little diagonal braces inside your
wing.
Are you sure that is what you really want to do?
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The sleeve isn't clamped tight; it's just a short piece of the next size
larger tubing slipped over the leading edge tubes. It stays on one side,
then when the wings are unfolded it slips to the center and spans across
both. There's no spanwise support other than friction, though I expect it
might help to prevent any relative vertical motion (wing twist).
Still, I have to think on this. There's always a "slight bit of play" in
any connection, and although I presume it was added to help support the
wing gap seal, I don't know that it's actually that important... and it IS
kind of a PITA to slip into place. OTOH, it WOULD add some additional
support in the event of a failure at some other point.
-Dana
--
Work is underway on drafting a new constitution for Iraq. Why don't we
send them ours? It worked for 200 years, and we don't use it any more.
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jb92563
Joined: 23 Mar 2007
Posts: 314
Location: Southern California
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| Posted: Tue Mar 25, 2008 6:13 am Post subject: Re: Ultrastar questions |
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EZ does have a point.
If that sleeve was clamped tight it would translate all sorts of vibration and flexing loads into those diagonal braces and accelerate the loosening of rivets or crack them at the bends.
In retrospect I'd leave the sleeve unclamped.
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_________________
Ray
Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider
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travis(at)tnkolbaircraft.
Guest
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| Posted: Tue Mar 25, 2008 7:37 am Post subject: Ultrastar questions |
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> If that sleeve was clamped tight it would translate all sorts of
vibration and flexing loads into those diagonal braces and accelerate the
loosening of rivets or crack them at the bends.
| Quote: |
In retrospect I'd leave the sleeve unclamped.
Ray
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Ray/Dana/Gang:
The braces on the nose of the inboard rib serve one purpose, to keep the
fabric from pulling the nose of the rib.
The leading edge braces are the important ones. I can not remember how many
the plans call for for the US and FS. This is a sensitive area for me and I
go overboard with 1/2" OD braces from leading edge to main spar on both ends
of the wing section.
There was never a requirement in the plans for a sleeve over the inboard
ends of the leading edge of the wings. Would never serve a structural
purpose.
john h
mkIII
Labhart Field, KY
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Tue Mar 25, 2008 9:37 am Post subject: Ultrastar questions |
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| Quote: | > If that sleeve was clamped tight it would translate all sorts of vibration and flexing loads into those diagonal braces and accelerate the loosening of rivets or crack them at the bends.
| Quote: |
In retrospect I'd leave the sleeve unclamped. |
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Well, as I said, it's not clamped; it's just another piece of tubing, about 8" long. Does take some pushing to get it over since there's a very slight misalignment between the leading edge tubes.
Of course, if there IS play in the other wing attach points then stressing it at the leading edge could either help or hurt... hurt, because it's stressed... or help, because the pretension might keep things from hammering back and forth.
| Quote: | The braces on the nose of the inboard rib serve one purpose, to keep the fabric from pulling the nose of the rib.
The leading edge braces are the important ones. I can not remember how many the plans call for for the US and FS. This is a sensitive area for me and I go overboard with 1/2" OD braces from leading edge to main spar on both ends of the wing section. |
The US plans only show one 5/16" brace, on the inboard end (not counting the three braces that support the inboard rib). Thinking about it (and in light of why you consider it a "sensitive area", John) it _does_ seem kinda flimsy.
| Quote: | | There was never a requirement in the plans for a sleeve over the inboard ends of the leading edge of the wings. Would never serve a structural purpose. |
No, as I said I suspect it was added because a previous owner thought it would better support the gap seal. I'm thinking, however, that adding bolts or pins through slots in the sleeve (so there's NO load on the sleeve until/unless the leading edge moves, say, 1/2", which could _only_ happen if the diagonal brace failed) could be an additional safety factor.
-Dana
Here's a picture if it comes through:
[img]cid:.0[/img]
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