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Replacement tail rod...?
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Dan Breitigam



Joined: 06 Apr 2011
Posts: 16

PostPosted: Tue Feb 20, 2018 11:20 am    Post subject: Re: Replacement tail rod...? Reply with quote

I see your point Rick. Perhaps it would work with big fat soft tundra tires.

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John Hauck



Joined: 09 Jan 2006
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Location: Titus, Alabama (hauck's holler)

PostPosted: Tue Feb 20, 2018 11:50 am    Post subject: Replacement tail rod...? Reply with quote

Wouldn't that be defeating the purpose and one of the major benefits of the
spring gear, aluminum or steel?

As an aside, folks would think you were flying a Challenger. Wink

john h
mkIII
Titus, Alabama
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PostPosted: Thu Feb 22, 2018 7:22 am    Post subject: Replacement tail rod...? Reply with quote

Cables are a safety for a hard landing at worst they would lessen a bad landingAnd prevent a gear collapse.
For what it’s worth !
roy 

On Tuesday, February 20, 2018, Rick Neilsen <neilsenrm(at)gmail.com (neilsenrm(at)gmail.com)> wrote:
Quote:
The duty of both steel and aluminum gear legs is to absorb landing stresses by flexing. Aluminum legs flex which is good but don't flex as far before they stay flexed. Restricting the flexing will transfer the landing loads to the plane where other not so evident damage might occur on a hard landing. I don't think you would want brace any Kolb gear leg. There might a benefit to dampen the spring back on some of the more springy steel gear legs.
Rick Neilsen
Redrive VW PoweredMKIIIC
On Tue, Feb 20, 2018 at 12:32 PM, Dan Breitigam <dbrtgm(at)me.com (dbrtgm(at)me.com)> wrote:
Quote:
--> Kolb-List message posted by: "Dan Breitigam" <dbrtgm(at)me.com (dbrtgm(at)me.com)>

Hi guys,

Regarding the gear leg comments; has anyone tried bracing aluminum gear legs with cables?  Would it be worth trying?

Thanks.

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Geo Metro 1.3L
Chattanooga




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PostPosted: Thu Feb 22, 2018 7:59 am    Post subject: Replacement tail rod...? Reply with quote

http://www.jackbhart.com/firefly/firefly140.html

Jack B. Hart. FF004
Winchester, IN


From: "Roy Spangler" <roy.spangler(at)kirtland.edu> Sent: Thursday, February 22, 2018 10:26 AM To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com> Subject: Re: Re: Replacement tail rod...?
Cables are a safety for a hard landing at worst they would lessen a bad landing And prevent a gear collapse.

For what it&rsquo;s worth !

roy On Tuesday, February 20, 2018, Rick Neilsen <neilsenrm(at)gmail.com (neilsenrm(at)gmail.com)> wrote:
Quote:
The duty of both steel and aluminum gear legs is to absorb landing stresses by flexing. Aluminum legs flex which is good but don't flex as far before they stay flexed. Restricting the flexing will transfer the landing loads to the plane where other not so evident damage might occur on a hard landing. I don't think you would want brace any Kolb gear leg. There might a benefit to dampen the spring back on some of the more springy steel gear legs.

Rick Neilsen
Redrive VW PoweredMKIIIC

On Tue, Feb 20, 2018 at 12:32 PM, Dan Breitigam <dbrtgm(at)me.com (dbrtgm(at)me.com)> wrote:
Quote:
--> Kolb-List message posted by: "Dan Breitigam" <dbrtgm(at)me.com (dbrtgm(at)me.com)> Hi guys, Regarding the gear leg comments; has anyone tried bracing aluminum gear legs with cables? Would it be worth trying? Thanks. -------- Kolb Mk III Geo Metro 1.3L Chattanooga Read this topic online here: http://forums.matronics.com/viewtopic.php?p=478137#478137 =========== -List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?Kolb-List =========== FORUMS - eferrer" target="_blank">http://forums.matronics.com =========== WIKI - errer" target="_blank">http://wiki.matronics.com =========== b Site - -Matt Dralle, List Admin. rel="noreferrer" target="_blank">http://www.matronics.com/contribution ===========




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rickofudall



Joined: 19 Sep 2009
Posts: 1317
Location: Udall, KS, USA

PostPosted: Thu Feb 22, 2018 8:03 am    Post subject: Replacement tail rod...? Reply with quote

Roy, Where are you going to put these cables? The aluminum gear leg is solid, where does the cable go? What size cable are you proposing? 3/32" cable has a breaking strength of 960 lb. That's less than a 2G landing load on a MK III. 1/8" cable has a breaking strength of 2000 lb which is less than a 4G load and will most likely still break. 5/32" cable? Go as big as 3/16"? Now you're beginning to talk some serious weight. In the late '70's some hang glider manufacturers began offering swaged 1/8" cable (breaking strength 2,000 lb) hang straps instead of the 1" tubular nylon strap. Much less drag was the claim. No one had any idea of the loading on that cable, it just seemed like a good idea at the time. I don't know how many pilots died when the cable snapped but an emergency message was put into "Hang Gliding" magazine advising pilots to remove the cable and manufacturers took it off the options list. It seems that a pilot flying through the shear around a thermal could generate the necessary loading to snap it. Whoda thunk that?
it's your airplane, do as you like, but do some testing to find out if it would really work as you think. Also give some thought to how you inspect and maintain them.
2 cents worth.
Rick Girard
Virus-free. www.avg.com [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2][/url]

On Thu, Feb 22, 2018 at 9:22 AM, Roy Spangler <roy.spangler(at)kirtland.edu (roy.spangler(at)kirtland.edu)> wrote:
Quote:
Cables are a safety for a hard landing at worst they would lessen a bad landingAnd prevent a gear collapse.
For what it’s worth !
roy 

On Tuesday, February 20, 2018, Rick Neilsen <neilsenrm(at)gmail.com (neilsenrm(at)gmail.com)> wrote:
Quote:
The duty of both steel and aluminum gear legs is to absorb landing stresses by flexing. Aluminum legs flex which is good but don't flex as far before they stay flexed. Restricting the flexing will transfer the landing loads to the plane where other not so evident damage might occur on a hard landing. I don't think you would want brace any Kolb gear leg. There might a benefit to dampen the spring back on some of the more springy steel gear legs.
Rick Neilsen
Redrive VW PoweredMKIIIC
On Tue, Feb 20, 2018 at 12:32 PM, Dan Breitigam <dbrtgm(at)me.com (dbrtgm(at)me.com)> wrote:
Quote:
--> Kolb-List message posted by: "Dan Breitigam" <dbrtgm(at)me.com (dbrtgm(at)me.com)>

Hi guys,

Regarding the gear leg comments; has anyone tried bracing aluminum gear legs with cables?  Would it be worth trying?

Thanks.

--------
Kolb Mk III
Geo Metro 1.3L
Chattanooga




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PostPosted: Thu Feb 22, 2018 8:32 am    Post subject: Replacement tail rod...? Reply with quote

IMHO, and in accordance with what I have learned from engineers, the "spring gear" (steel or aluminum) has the advantage that it is the most simple and lowest parts count for a landing gear that can absorb any sort of impact. It also is often the lowest drag of typical gear systems.

The spring gear is often not the lightest way to do it, and it is definitely not the best at absorbing (mitigating) the impact of landing.

To actually absorb and mitigate the impact of landing, there needs to be some way of changing how that energy is stored/expended after the first impact.That of course is where the oleo struts, hydraulic fluid, metered orfices, check valves, etc. etc. come into play on more complicated aircraft.

The designer(s) and engineer(s) at Kolb made the obvious and correct choice of simplicity and lower cost rather than complexity and higher cost.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Thu, 2/22/18, Roy Spangler <roy.spangler(at)kirtland.edu> wrote:

Subject: Re: Re: Replacement tail rod...?
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Thursday, February 22, 2018, 7:22 AM

Cables are a safety for a hard
landing at worst they would lessen a bad landingAnd
prevent a gear collapse.
For what it’s worth !
roy 

On Tuesday, February 20, 2018, Rick Neilsen <neilsenrm(at)gmail.com>
wrote:
The duty of both steel and aluminum
gear legs is to absorb landing stresses by flexing. Aluminum
legs flex which is good but don't flex as far before
they stay flexed. Restricting the flexing will transfer the
landing loads to the plane where other not so evident damage
might occur on a hard landing. I don't think you would
want brace any Kolb gear leg. There might a benefit to
dampen the spring back on some of the more springy steel
gear legs.
Rick NeilsenRedrive VW
PoweredMKIIIC
On Tue, Feb 20, 2018
at 12:32 PM, Dan Breitigam <dbrtgm(at)me.com>
wrote:

"Dan Breitigam" <dbrtgm(at)me.com>



Hi guys,



Regarding the gear leg comments; has anyone tried bracing
aluminum gear legs with cables?  Would it be worth trying?



Thanks.



--------

Kolb Mk III

Geo Metro 1.3L

Chattanooga









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ewtopic.php?p=478137#478137













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John Hauck



Joined: 09 Jan 2006
Posts: 4521
Location: Titus, Alabama (hauck's holler)

PostPosted: Thu Feb 22, 2018 9:15 am    Post subject: Replacement tail rod...? Reply with quote

Jack H's cables will probably prevent spreading the main gear, but effectively kill the suspension.

It has been proven over and over again, the 1" 7075 aluminum gear legs are inadequate for the FF, as well as the original Firestar. During taxi to take off for the first time in my FS, the 1" aluminum legs bent before I had a chance to fly. I have to admit my airstrip at that time was not the smoothest, but in my estimation should never have bent those little aluminum legs. To overcome that weakness we need suitable replacements that will perform satisfactorily. This will add weight and Jack H does not want to do that I am sure.

I have never been a fan of wire bracing on Kolb main gear legs. Kolbs are prone to nose over because Homer Kolb designed them to carry most of their weight on the main gear and very little on the tail wheel. This gives them the great characteristic of very easy ground handling. Bad enough taxiing on high grass and weeds. Add wires and it is a guarantee you'll put it on its nose, like landing in soy beans. Wink

john h
mkIII
Titus, Alabama



From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Jack Hart
Sent: Thursday, February 22, 2018 9:59 AM
To: kolb-list(at)matronics.com
Subject: Re: Re: Replacement tail rod...?






http://www.jackbhart.com/firefly/firefly140.html



Jack B. Hart. FF004

Winchester, IN


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west1m



Joined: 19 Apr 2014
Posts: 120
Location: Hastings, MN

PostPosted: Thu Feb 22, 2018 6:26 pm    Post subject: Re: Replacement tail rod...? Reply with quote

After bending a couple set of legs I went to Jacks wire bracing but added 4 chevy valve springs (2 per side) in the cables. This has been working well for my lack of gracefull landing talent.

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PostPosted: Fri Feb 23, 2018 4:42 am    Post subject: Replacement tail rod...? Reply with quote

The addition of VGs does more for landing gracefully than anything short of skill.I have the old spring steel tapered gear legs, and I like them.
G.Aman MK3C Jabiru 2200A 1100 hrs
Quote:
On Feb 22, 2018, at 9:26 PM, west1m <west1m(at)hotmail.com> wrote:



After bending a couple set of legs I went to Jacks wire bracing but added 4 chevy valve springs (2 per side) in the cables. This has been working well for my lack of gracefull landing talent.

--------
West1m
Hastings, MN




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Jack B Hart



Joined: 22 Feb 2018
Posts: 9
Location: Winchester, IN

PostPosted: Sun Feb 25, 2018 2:59 pm    Post subject: Replacement tail rod...? Reply with quote

Quote:

John,

I don't understand your statement. The cables are designed to help in the
case of a "plop" and do nothing to prevent the gear from flexing or bending
front to back and/or inward. If you drop a wheel into a hole, the leg will
bend just as it would before the cable system was installed and protects
the fuselage from being damaged. If I recall correctly, the whole works
weighed a few ounces.

I put up the previous jump to show that no modifications need to be made
to the existing structures and that cables could be used to keep the
gear from spreading. $20 spent and the time required to fabricate parts
seemed like a good trade off in comparison to straightening and/or
purchasing and installing new legs.

http://www.jackbhart.com/firefly/firefly134.html

In case you missed it, I put up the above jump so that you can view the
analysis that was done to determine if adding cables would be beneficial.
These calculations indicated the original leg would start to bend at 1.8 G
in a level straight two wheel plop. With the cable system in place and
assuming a plop hard enough to cause cable failure, the cable and gear leg
system will withstand a 5.2 G plop.


Jack B. Hart, FF004
Winchester, IN

----------------------------------------
From: "John Hauck" <jhauck(at)elmore.rr.com>
Sent: Thursday, February 22, 2018 12:18 PM
To: kolb-list(at)matronics.com
Subject: RE: Re: Replacement tail rod...?

Jack H's cables will probably prevent spreading the main gear, but
effectively kill the suspension.





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John Hauck



Joined: 09 Jan 2006
Posts: 4521
Location: Titus, Alabama (hauck's holler)

PostPosted: Sun Feb 25, 2018 4:25 pm    Post subject: Replacement tail rod...? Reply with quote

Jack H/Kolbers:

By adding cables and restricting outward flex of the gear legs, your modification effectively kills the spring in the direction it is needed most, outward. To me, what you have done is change flexible gear to rigid gear.

I went to 1 1/8" 7075 after my initial taxi when I bent the 1" 7075 legs before I got a chance to fly. 1 1/8" didn't hack it either, which proved to me that 7075 rod didn't make good spring gear. Heat treated 4130 has proven much better, although I can bend them too when I try.

Spring gear is much easier on the aircraft than rigid.

From the photo of your airplane, it is obvious you landed on the right gear, putting all the load on one leg. I do that too, but on the left leg.

john h
mkIII
Titus, Alabama



From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Jack Hart
Sent: Sunday, February 25, 2018 4:59 PM
To: kolb-list(at)matronics.com
Subject: Re: Replacement tail rod...?

Quote:
John, I don't understand your statement. The cables are designed to help in the case of a "plop" and do nothing to prevent the gear from flexing or bending front to back and/or inward. If you drop a wheel into a hole, the leg will bend just as it would before the cable system was installed and protects the fuselage from being damaged. If I recall correctly, the whole works weighed a few ounces. John,
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Jack B Hart



Joined: 22 Feb 2018
Posts: 9
Location: Winchester, IN

PostPosted: Sun Feb 25, 2018 9:11 pm    Post subject: Replacement tail rod...? Reply with quote

John,

I believe you have it right. The FireFly gear is rigid by design and the aluminum leg bends so easily. If you apply a 330 pound load in any direction at the axle, the leg will bend at just below the fuselage socket. By adding the cable I have, indeed, reduced one degree of flexsure and gained some freedom from plops.

As for the photo, it is difficult to tell if it was or was not a level plop. At the time it felt like it was. Both legs had to be straightened. It could be that the right tire broke loose from the asphalt first.


Jack B Hart FF004
Winchester, IN
From: "John Hauck" <jhauck(at)elmore.rr.com> Sent: Sunday, February 25, 2018 7:28 PM To: kolb-list(at)matronics.com Subject: RE: Re: Replacement tail rod...?

Jack H/Kolbers:

By adding cables and restricting outward flex of the gear legs, your modification effectively kills the spring in the direction it is needed most, outward. To me, what you have done is change flexible gear to rigid gear.

Spring gear is much easier on the aircraft than rigid.

From the photo of your airplane, it is obvious you landed on the right gear, putting all the load on one leg. I do that too, but on the left leg.


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John Hauck



Joined: 09 Jan 2006
Posts: 4521
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon Feb 26, 2018 6:03 am    Post subject: Replacement tail rod...? Reply with quote

To the best of my knowledge, the only aircraft Homer Kolb designed with rigid gear was the Flyer and the Ultrastar.

The Firestar was the first to have flexible main gear legs. The gear legs were designed to be flexible, to give the aircraft landing gear some spring suspension to take landing and ground handling loads off the airframe.

All Kolb aircraft models from the Firestar on are designed with spring landing gear legs, flexible, not rigid.

The rigid gear on my Ultrastar was not forgiving in the least. On my first landing in my unimproved cow pasture airstrip, my roll out took me across a cow path (rut) that took out the main gear, my prop, and the little turned up nose skid of the airframe.

Del Cross, who flew a Kolb Flyer at Sun and Fun and Lakeland, upgraded his rigid main gear to 7075 aluminum rod, making them longer to get the nose of the Flyer out of its normal level attitude on the ground. Del was killed when his Flyer crashed some years ago. RIP.

john h
mkIII
Titus, Alabama



From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Jack Hart
Sent: Sunday, February 25, 2018 11:11 PM
To: kolb-list(at)matronics.com
Subject: RE: Re: Replacement tail rod...?


John,



I believe you have it right. The FireFly gear is rigid by design and the aluminum leg bends so easily. If you apply a 330 pound load in any direction at the axle, the leg will bend at just below the fuselage socket. By adding the cable I have, indeed, reduced one degree of flexsure and gained some freedom from plops.



As for the photo, it is difficult to tell if it was or was not a level plop. At the time it felt like it was. Both legs had to be straightened. It could be that the right tire broke loose from the asphalt first.





Jack B Hart FF004

Winchester, IN
From: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>
Sent: Sunday, February 25, 2018 7:28 PM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: RE: Re: Replacement tail rod...?


Jack H/Kolbers:

By adding cables and restricting outward flex of the gear legs, your modification effectively kills the spring in the direction it is needed most, outward. To me, what you have done is change flexible gear to rigid gear.

Spring gear is much easier on the aircraft than rigid.

From the photo of your airplane, it is obvious you landed on the right gear, putting all the load on one leg. I do that too, but on the left leg.


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Titus, Alabama
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Jack B Hart



Joined: 22 Feb 2018
Posts: 9
Location: Winchester, IN

PostPosted: Mon Feb 26, 2018 7:30 am    Post subject: Replacement tail rod...? Reply with quote

John,

If the below is so, why is it that the FireFly legs bend in a 1.8 G plop?

Jack B. Hart FF004
Winchester, IN





From: "John Hauck" <jhauck(at)elmore.rr.com> Sent: Monday, February 26, 2018 9:06 AM To: kolb-list(at)matronics.com Subject: RE: Re: Replacement tail rod...?

All Kolb aircraft models from the Firestar on are designed with spring landing gear legs, flexible, not rigid.


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Jack B Hart FFoo4
Winchester, IN
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John Hauck



Joined: 09 Jan 2006
Posts: 4521
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon Feb 26, 2018 8:31 am    Post subject: Replacement tail rod...? Reply with quote

Springs are flexible to a point. When overstressed they bend or break. That's how my springs work. Isn't that how your springs work?

Didn't your gear legs flex to the point you over stressed and bent them?

I've flown with a G Meter since my Firestar days. If you sneeze while taxiing, you'll get 2 or 3 Gs very easily.

Jack H is wearing me out. I quit. Wink

john h
mkIII
Titus, Alabama

From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Jack Hart
Sent: Monday, February 26, 2018 9:30 AM
To: kolb-list(at)matronics.com
Subject: RE: Re: Replacement tail rod...?


John,



If the below is so, why is it that the FireFly legs bend in a 1.8 G plop?



Jack B. Hart FF004

Winchester, IN










From: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>
Sent: Monday, February 26, 2018 9:06 AM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: RE: Re: Replacement tail rod...?



All Kolb aircraft models from the Firestar on are designed with spring landing gear legs, flexible, not rigid.


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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama
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victorbravo(at)sbcglobal.
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PostPosted: Mon Feb 26, 2018 9:13 am    Post subject: Replacement tail rod...? Reply with quote

After having made numerous landing gears out of fiberglass, carbon fiber, etc.... the world's largest manufacturer of landing gears for light aircraft (Grove) uses 7075-T6 exclusively. Using a direct comparison between MATERIAL PROPERTIES, the 7075 has better stress/strain/yield/weight and all that high brain function engineering stuff I don't understand.

But when you put a FIXED CROSS SECTION into the mix, things change. For a given size, thickness, or diameter, then steel starts to show its advantages.

A few years ago I took over the FAA "STC" approval for changing the tricycle gear Cessna 172 back into a tailwheel configuration (like the Cessna 170). As part of that process, I learned a whole lot about this stuff, thanks to an old gray engineer who was kind enough to put up with my lack of a formal engineering education.

We wanted to replace the steel Cessna main gear legs with aluminum, because the exact steel alloy that Cessna used was a special order from a steel mill. So my engineer did a bunch of calculations, and he figured out that to replace a 13/16" thick spring steel main gear, we needed a 1.25" thick piece of 7075-T6 aluminum... to get the same spring properties, energy absorbtion, and impact capability.

How is this relevant to a discussion about Kolb landing gears? Because on a Kolb aircraft the size of the main gear is always limited to the size of the round socket tube that Kolb builds in to the fuselages. With a given size fuselage socket tube, if you want or need a "stronger" main gear than the original 7075 Kolb gear leg, you have no choice but to change materials and use steel. (even carbon fiber wouldn't help you because you would need a 2 inch socket tube to make the gear out of carbon.)

So John H made the only upgrade that was legitimately possible, by moving from aluminum to steel. Kolb figured this out at some point when they wanted to build heavier two seat airplanes,a nd they went to hardened steel as well.

For the people who are obsessed with weight, or who are on a quest to meet Part 103 weight, then aluminum or carbon is worth pursuing, but to really be able to use those materials you would need to increase the diameter of the socket tube in the fuselage. That would be quite a project !

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities


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