foam core question

[Ron Van Putte]

On Apr 16, 2004, at 8:15 AM, Gray E Fowler wrote:

>
> Mark
>
> The idea behind a rib at the end of the tube is simply to distribute 
> the load of the wing.  Without the rib, there will be a stress riser 
> right at the end of the tube. A violent maneuver such as a snap could 
> easily buckle the balsa skin, since the foam has such low compression 
> strength as does the balsa itself.  I am sure there are people flying 
> without a rib but I would advise against it. When the wing tube is 
> bonded to the wing root and the "false" rib it will carry all the 
> load. Only the portion of the wing past the rib will then flex 
> creating stress at the tube termination. This stress is either 
> concentrated at the very end of the tube OR distributed over the 
> surface area of the rib. Because the stiffest component of the wing 
> will always carry the load (the tube) any kind of stiffening strips 
> inside the rib are dead weight.

Let's ask Tony Stillman to respond about the importance if a properly 
designed and installed wing tube support.  He lost a new Excellence a 
year ago when the wing tube broke out through the wing skin.  He might 
also comment about his satisfaction with the manufacturer/producer's 
response to his comments to them about the failure.

Ron Van Putte

> "Mark Hunt" <flyintexan at houston.rr.com>
> Sent by: discussion-request at nsrca.org
>
> 04/15/2004 09:16 PM
> Please respond to discussion
>
>        
>         To:        <discussion at nsrca.org>
>         cc:        
>         Subject:        foam core question
>
>
>
> Sirs:
>  
> As a newbie to cutting foam cores, I have a question regarding how to 
> strengthen the wing panel.  Does the preferred method include 
> attaching some c.f. strips to the inside of the skins?  Should they 
> extend from the root all the way to the tip?  I know some guys feel it 
> is a must to also use a false rib near the end of the tube sleeve 
> also?  I hear that some guys (r u out there Nat?) are confident 
> without any false rib or c.f. under the skin....?
>  
> I cut the cores earlier tonight (to rebuild my 2M after a mid-air) 
> with the help of a friend, and they turned out just beautiful.  I have 
> a nice plan to machine a drill jig for cutting the spar tube hole...so 
> that's seems to be solved.
>  
> Thanks in advance for the help...
>  
> Mark
> www.geocities.com/markhunt_2000/INSIGHT
>  
>  
>
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