"beefing up / modifying" structures a BAD idea???

[flywise 169]

Hi guys,

I have always wondered how some very talented builders are able to modify primary structures in our light aircrafts....are you all high end aircraft structure designers/engineers??? Have you inputs from Dean Wilson?I have read a good article about this very subject and I would like to have your appreciated comments...

Everyone who is considering a "beefing up" should read this I believe...

Cheeers, Laurent

P.s I would like to ad that this post has absolutely no intention criticizing anyone doing modifications on their birds. I am only trying to figure out if there is / are good ways & tricks to stay safe doing it. 

 

Edited 21 Nov 2017 by flywise

[akflyer 1427]

When a known failure point is under my ass you can bet I am going to beef it up.  These planes have evolved over the years and yes, one must think about the affects of changes to other areas of the structures.  We are in the world of experimentals and as such, we get to play around in areas that certified guys don't without tons of paperwork etc.  Lots of people build boats who are not marine architects etc.  

 

[1avidflyer 1983]

If you look at how many seat trusses have folded up on Avids and Kitfoxes, using the factory bungee gear, you know it's a weak area.  At that point, it's asking for trouble if you don't beef it up.  Even Avid eventually recommended infilling with plywood.   As far as widening the fuselage at the doors, Lots have done that before me as well, Murhel  Williams comes to mind.  He sells a kit/add on you can do yourself.  And in the end, I'm the one taking the most risk.   JImChuk

[EDMO 1078]

If you look at how many seat trusses have folded up on Avids and Kitfoxes, using the factory bungee gear, you know it's a weak area.  At that point, it's asking for trouble if you don't beef it up.  Even Avid eventually recommended infilling with plywood.   As far as widening the fuselage at the doors, Lots have done that before me as well, Murhel  Williams comes to mind.  He sells a kit/add on you can do yourself.  And in the end, I'm the one taking the most risk.   JImChuk

Totally agree Jim - "it's MY ass"!  Not all of us are Aeronautical Engineers, or even Engineers, but most have enough common sense to see that something could be made stronger when it has failed so many times before. 

On the more professional side, as an AMT/A&P, just look at how many ADs, STCs and changes have been made to factory and experimental planes.  If there was no dream or scheme, then how would the Stits Playmate have ever become the Van's RV - How would Avid become Kitfox and so many others that have been modified?  How would John Larsen ever made the Pursang and Airdale which brought the Fat Avids, Avid+, etc, and started the idea of me trying to put separate flaps and ailerons on my bird?  Keep on changing, IMO. 

I am sure that Budd Davidson had some valid points, although I wrote this without reading his article, but after reading what Jim Chuk wrote - Got to be honest in writing this.  EDMO

Edited 22 Nov 2017 by EDMO