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frank.goodnight(at)att.ne
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 Posted: Tue Nov 16, 2010 4:44 pm Post subject: Cracked spar on fire star. |
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----- Forwarded Message ----
From: Jon Lockhart <jonlock2(at)gmail.com>
To: frank.goodnight <frank.goodnight(at)att.net>; customersupport(at)tnkolbaircraft.com; kolb-list(at)matronics.com
Sent: Tue, November 16, 2010 6:02:16 PM
Subject: Cracked spar on fire star.
Please review the photos. Thanks, Frank Goodnight
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flykolb(at)pa.net
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| Posted: Tue Nov 16, 2010 6:02 pm Post subject: Cracked spar on fire star. |
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Frank,
There are 2 issues:
Roughly speaking, an HKS has approximately twice the power impulse than a two-stoke because it has only half of the power pulses.
(A 2-stroke piston fires every time in goes down, but only every other time on a 4-stroke.) So the HKS will place a higher stress on the structure than a 2-stroke of comparable power.
Somewhere along the way, the brace gusset from the motor mount got moved to the center of the square tube. Formerly it was welded to the leading edge of the square tube.
On your frame the power pulses are transmitted to the center of the thin wall of the square tube – this will result in a certain amount of flexing which could possible lead to the cracking you have.
A possible fix would be the addition of a gusset to get the forces directly to the corner of the square tube.
If someone is going to sound an alarm about the cracking, I think a distinction could be made between the frames that have the center orientated location vs the edge oriented location.
Dennis
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of frank goodnight
Sent: Tuesday, November 16, 2010 7:28 PM
To: kolb-list(at)matronics.com
Subject: Fw: Cracked spar on fire star.
----- Forwarded Message ----
From: Jon Lockhart <jonlock2(at)gmail.com>
To: frank.goodnight <frank.goodnight(at)att.net>; customersupport(at)tnkolbaircraft.com; kolb-list(at)matronics.com
Sent: Tue, November 16, 2010 6:02:16 PM
Subject: Cracked spar on fire star.
Please review the photos. Thanks, Frank Goodnight
[quote][b]
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jbhart(at)onlyinternet.ne
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| Posted: Wed Nov 17, 2010 8:35 am Post subject: Cracked spar on fire star. |
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| Quote: | From:<Frank Goodnight>
Sent: Tue, November 16, 2010 6:02:16 PM
Attachment Converted:
"c:\eudora\attach\aircraft photo 1.JPG"
Attachment Converted:
"c:\eudora\attach\aircraft photo 1
(2).JPG"
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Frank,
Thank you for your photos. I just came back from checking the FireFly. My
braces weld to the corner of the square tube. I did not find any cracks,
but due to using powder coat, they would have to be quite large to see them.
I flew the FireFly with the Victor 1+, a 313cc one cylinder engine, for 188
hours. One of the advantages of replacing it with the MZ34 was to reduce
displacement and firing impulse vibration. This has been proven out in that
the FireFly is much smoother and quieter in flight. If you are using a
heavy, high inertia propeller, you may want to consider changing to a
smaller, lighter, low inertia propeller. This will allow more firing
impulse energy to be dissipated into the propeller than being transferred to
the mounts and on to the cage.
Jack B. Hart FF004
Winchester, IN
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captainron1(at)cox.net
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| Posted: Fri Nov 26, 2010 8:35 pm Post subject: Cracked spar on fire star. |
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Is that a corrosion crack?
It being a long the seem does not look like fatigue crack.
---- frank goodnight <frank.goodnight(at)att.net> wrote:
=============
----- Forwarded Message ----
From: Jon Lockhart <jonlock2(at)gmail.com>
To: frank.goodnight <frank.goodnight(at)att.net>; customersupport(at)tnkolbaircraft.com; kolb-list(at)matronics.com
Sent: Tue, November 16, 2010 6:02:16 PM
Subject: Cracked spar on fire star.
Please review the photos. Thanks, Frank Goodnight
--
kugelair.com
[quote][b]
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