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jbhart(at)onlyinternet.ne
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 Posted: Sat Sep 05, 2009 6:13 pm Post subject: Tail Wire Tangs Breaking And other Tail Brace Issue Contin |
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Kolbers,
Got to wondering what the loads would be on the upper tail cables and tangs.
I scaled out the FireFly drawings for the horizontal stabilizer and
elevator. By drawing this up and cutting out the combined profile for one
side, I could find the centroid of the area. This is the spot that one
could place all the load that is equivalent to the load being spread over
the whole surface. I know this is not real but for purposes of finding the
table tension under load it works.
The triangle made up of the cable and tangs, the vertical tail post and
stabilizer attachment points make up a right triangle of 25.5 inches high,
34 inches wide with a 42.5 inch long side. The load point turned out to be
15 inches from the inside hinge point.
If one assumes that the FireFly horizontal tail surfaces must hold up 100
pounds in one G flight, then the load on one side would be 50 pounds. By
summing moments and forces and applying a little trig, one can calculate the
cable tension. In this case it turns out to be 37 pounds. If one pushes
the load on up to six G's, the cable tension will increase to 222 pounds.
This is far short of the 2,000 pound load carrying capability of 1/8 inch
cable.
The compression load on the horizontal stabilizer rear member will go from
29.4 to 176.4 pounds. The rudder post has to work a little harder because
it must sustain the load of both sides, so it will go from 61.2 to 367
pounds at six G's.
It looks like Dennis did a good job, in that, there is plenty of reserve in
the design. The cables and the tangs should be adequate as long as one does
not over tighten the cables.
Pre-flight inspections are good.
Jack B. Hart FF004
Winchester, IN
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jlsk1(at)frontiernet.net
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| Posted: Sat Sep 05, 2009 6:23 pm Post subject: Tail Wire Tangs Breaking And other Tail Brace Issue Contin |
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NICE JOB !
Jim Kmet
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henry.voris
Joined: 02 Mar 2007
Posts: 116
Location: Pueo Field, Kula, Maui
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| Posted: Sat Sep 05, 2009 9:49 pm Post subject: Re: Tail Wire Tangs Breaking And other Tail Brace Issue Co |
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Clear thinking...
Thanks Jack.
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Henry
Firefly Five-Charlie-Bravo
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