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

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

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. Smile

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]
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--> 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
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PostPosted: Sun Apr 16, 2017 5:09 pm    Post subject: Leading edge bracing; was: Kolb Twinstar (original version) Reply with quote

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. Smile

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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