Snao G's

[Wayne Galligan]

A test on the tube by itself would not be a very good way to assess the total load supporting strength of the wing tube setup in our planes.  The wing tubes loading carrying ability is determined by the distribution along the sleeve and through the bearing surfaces at the root rib and support rib at the end.   The support rib and root rib then spreads that load through the skin and to the leading edge if the rib goes that far.   The weakest point of the wing tube in the setup is at the point between the fuse and root rib where it is really not supported by anything even though this is a very small area.    Ideally to make the tube carry as much load as evenly as possible the sleeve coming out of the fuse would protrude into the wing root rib and the end of the tube at the root would also be supported at the same spot. From some of the posts I have seen the support rib at the end of the tube can be suspect also.  So running the end support rib to the leading edge for max. load spread.  Since I have not been able to bend a wing tube yet I think that the std method building the sleeve structure to be sufficient enough.  But then.... I have not flown 100 reverse avalanches to date.    If your are using an aluminum tube and have any doubts by all means get a c.f. tube.  Like Gray Fowler once posted if not twice, the c.f tube will deflect  and return its original position from being stressed up to its failure point then it will just shatter but an aluminum tube will just bend and stay at the point of deflection or bend to a folded mess.  The point between where the c.f. tube breaks and the aluminum tube bends is significant enough to warrant using the c.f. tube....plus the c.f tube is about half as light.... but you'all knew that.
   Mike Dunphy did some testing on the c.f tubes a while back and had some pretty interesting stats.  Maybe he would chime in here.


Wayne Galligan
  ----- Original Message ----- 
  From: brianyemail-nsrca at yahoo.com 
  To: discussion at nsrca.org 
  Sent: Thursday, January 27, 2005 1:14 PM
  Subject: Re: RE: Snao G's


  For the tube itself that load can be approximated by setting your tube between two chairs resting your hands in the middle and raising yourself off the floor, for me thats a 180lb load. 

  I guess you could do the same test with your plane....... 

  rcaerobob at cox.net wrote:
    Yeaop. That works out to about 147 lba (assuming a 10.5lb plane) distributed on that 7/8" dia wing tube, with complete concentration of the G's likely at the fuse/wing root intersection, with some load distribution laterally, but I'd bet not much.

    How many of us ever "test" our wing sockets to 150 lbs!!!!
    > 
    > From: "Michael Laggis" 
    > Date: 2005/01/27 Thu PM 01:51:34 EST
    > To: 
    > Subject: RE: Snao G's
    > 
    > Very interesting.
    > 
    > Michael Laggis
    > 
    > _____ 
    > 
    > From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
    > Behalf Of Earl Haury
    > Sent: Thursday, January 27, 2005 9:40 AM
    > To: Discussion List, NSRCA
    > Subject: Snao G's
    > 
    > 
    > FWIW, I took a quick look at some snap G's yesterday. Equipment was a Quique
    > YAK (140 size) fitted with an Eagle Tree Systems datalogger with G sensor. I
    > only gathered data from one flight - so take that into consideration.
    > 
    > Flat and level pos snaps @ (nominally) 100mph = 13G, dropping the speed to
    > 70mph = 7G. (A normal pull to vertical @ 100mph = 7G.)
    > 
    > An Avalanche with a neg snap at the top measured -5G @ 50mph.
    > 
    > A Rev Avalanche with a pos snap at the bottom measured 13G @ 95mph. (Masters
    > maneuver - intentionally flown fast.)
    > 
    > An Avalanche from the top (push - F05) with a neg snap and a half at the
    > bottom measured -14G @ 90mph. 
    > 
    > (I normally measure around 5G on upline and downline snaps with my Partner.)
    > 
    > All snaps were executed with rapid / high degree elevator lead and %
    > reduction of elevator during rotation.
    > 
    > I may look at this further as the mood strikes. As expected, controlling
    > speed into snaps is easier on your airplane. None of the observed loads (in
    > my opinion) should damage a well constructed aerobatic model (wouldn't want
    > to ride in it though).
    > 
    > Earl
    > 
    > 

    Bob Pastorello, El Reno, OK, USA
    rcaerobob at cox.net
    www.rcaerobats.net

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