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Leading edge bracing; was: Kolb Twinstar (original version)

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ceengland7(at)gmail.com
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Posted: Sun Apr 16, 2017 5:03 pm Post subject: Leading edge bracing; was: Kolb Twinstar (original version)

You're right about the little tubes       cracking. One of my wing leading edge tubes had some corrosion       & a big crack about half way around it near the root rib.       After drilling it free, the diagonal tube tying it to the main       spar showed cracks in the bends on both ends. I'll be adding new       diagonals, either of larger aluminum, or some 4130 tubes the same       size. (Easier to form safely, by using a little heat.)

       

       Thanks for the addtl info. You may well get a call from me before       this project is finished. 

       

       Charlie

       

       

       On 4/16/2017 5:35 PM, John Hauck wrote:

     

     [quote]                       <![endif]-->   <![endif]-->                

Actually,             the two 5/16" tubes are fabric braces to keep the fabric             from pulling the aluminum rib nose inward.  There is no             lateral bracing of the leading edge tube except a long 5/16             alum tube that is in compression.         

          

The             bow tip doesn't do much for lateral bracing of the leading             edge tube.  That's all you have to keep the rib noses in             column.  Once they get pulled out of column, they will             probably fail.         

          

The             small 5/16 tubes are flattened, bent, and riveted.  They             tend to break at this point from vibration with not a whole             lot of time on them.         

          

I             used two 1/2" alum tubes, one inboard and one outboard,             diagonally working with each other, attached to the leading             edge tube and the main spare.  Wish I had a photo of my wing             handy.  If I can find one I will share it.         

          

I             may be overly cautious, but it makes me feel more             comfortable, especially when I get caught in extremely rough             air.         

          

Sorry             for the delay in responding.  Just got home from a 4 day             trip.         

          

If             you need more info, call me.  334-567-6280         

          

john             h         

mkIII         

Titus,             Alabama         

          

          

                     

From:               owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)               [mailto:owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)] On                 Behalf Of Charlie England

               Sent: Thursday, April 13, 2017 11:05 AM

               To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)

               Subject: Leading edge bracing; was: Kolb               Twinstar (original version) info request         

         

                                                 

John,             

                            

              

                            

You mentioned leading edge bracing.                 This is all I see in the Twinstar I'm restoring. There's                 nothing along the rest of the leading edge that                 triangulates/ braces the leading edge.              

                            

              

                            

Would you consider this adequate?                 It's easy to add now, with the cover coming off.             

                            

              

                            

Thanks,             

                            

              

                            

Charlie             

                            

              

                            

Thanks, John. I wasn't sure about how                 rugged the tubes would be when driving out mandrels,                 etc. I use similar tricks on the heavier experimentals                 I've owned. I've got a spring loaded center punch that I                 ground to a flat nosed, straight shaft, & use it to                 punch out driven rivets after drilling the heads. I also                 use small, flush cutting 'dykes' (diagonal  wire                 cutters) to grab pop rivet heads

                 

                 On 4/9/2017 5:58 PM, John Hauck wrote:             

             [quote]                	  Quote: 	
		  --> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com> (jhauck(at)elmore.rr.com) Charlie E/Kolbers: I have recovered a bunch of them.  All that I tore up and a few I didn't. Drilling rivets can be accomplished once you have the mandrels removed.  It takes a 1/16" punch, or you can use a pulled mandrel, grind the end flat, hold with vise grips, and knock out with a hammer.  The rivet needs to be held to prevent spinning.  I grind a V in the end of a hack saw blade with sharp beveled edges.  Use that to push up under the rivet to lock it in place while drilling. 4130 airframes should be tube sealed when fabricated.  99% of Kolbs probably have never been tube sealed.  Their builders probably never heard of tube sealing.  4130 rusts from inside out if not sealed.  That would worry me with an old fuselage, especially a Twinstar.  I can't remember exactly what the fuselage looks like other that the root tube that seats and stuff are attached to.  This I would make sure is rust free on the inside.   	
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ceengland7(at)gmail.com
Guest

Posted: Sun Apr 16, 2017 5:09 pm Post subject: Leading edge bracing; was: Kolb Twinstar (original version)

Thanks, Richard; I'll look at doing that mod, as well.



BTW, my plans just mention '1/8 x 1/8 pop rivets'. What's the rivet of 

choice? Just a typical 18-8 stainless, or 304 stainless? the 316 

stainless are pricey enough that  enough to do the whole plane might 

cost as much as the whole kit. 



Charlie



On 4/13/2017 9:17 PM, Richard Pike wrote:

 	  Quote: 	
		   



 I'm not John, but if you scroll down to page 21 in the MKIII Yellow Book, you will see what Kolb though to be a very useful reinforcement.

 http://oh2fly.net/oldpoops/Lexan%20rear%20enclosure.html



 --------

 Richard Pike

 Kolb MKIII N420P (420ldPoops)

 Kingsport, TN 3TN0



 Forgiving is tough. Being forgiven is wonderful.




	




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