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jgswartout(at)gmail.com
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 Posted: Sat Jan 03, 2009 11:20 am Post subject: Top Longeron Gusset (7F3-3SP) |
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Wow, that's a long time ago! I'm building an 801, but I assume that the gusset is similar. I remember remaking those over and over again--but I don't remember exactly why. (Probably because of the difficulty of precisely positioning all twenty-some rivet holes to match up with the holes I had already drilled in the longerons and cabin frame tubes.) I made them of heavier stock than the pieces supplied (0.063 vs. 0.040)--because Chris put out a note advising builders to replace the top channel (across the front edge of the rear fuselage top skin--at the top of the door posts--with heavier material than the kit supplied, for structural reasons, and I figured if the channel is heavier then the gussets that attach it to the longerons and top cabin frame tubes should be heavier too. I therefore made the gussets longer, long enough to reach an additional longeron rivet, and filed down (tapered the thickness of) the rear ends of the gussets so the rear top skin, which goes on top of the gussets, would not be bent over a sharp thick edge at the rear end of the gusset.
To answer your question, I would tend to assume that after 24 years, if the structural design of the -701 was deficient, that would have been determined by now. I don't think it would do any harm to make the gusset wider--enough to pick up another rivet in the top channel, but it probably isn't necessary. You may recall that an early prototype of the -801 crashed after apparently shedding its wings in flight in California a few years ago. That plane probably had the thinner top channel, (the advice to make it thicker came out after that crash) and I believe it had the very heavy in-line 6-cylinder 210hp LOM engine and propeller, which would have exceeded the fwf weight limit ZAC specifies now by at least 60 lbs, I'd estimate, and would have required ballast in the tail to balance all that engine and prop weight. Mind you, I am speculating here, but I assume the modification to the top channel arose from that crash. I am not aware of any similar structural failures in the -701. Use your best judgement.
John
On Fri, Jan 2, 2009 at 10:28 PM, Curt Thompson <Curt.Thompson(at)verizon.net (Curt.Thompson(at)verizon.net)> wrote:
[quote]
John,
I'm working on making "Top Longeron Gusset" (7F3-3SP) and I noticed the problems you posted a while back on the Zenith List. Do you think it would be a good idea to make that part about 100mm wide (rather than the 85mm in the plans)?
Curt
Plans building CH701
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john.marzulli(at)gmail.co
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| Posted: Sat Jan 03, 2009 12:50 pm Post subject: Top Longeron Gusset (7F3-3SP) |
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I think what Curt is referring to is the issue I had with the top gusset and rivet spacing.
http://701builder.blogspot.com/2008_01_01_archive.html
John Marzulli
http://www.GenevieveMarzulli.org/
http://marzulli.smugmug.com/
http://701Builder.blogspot.com/
http://www.JohnMarzulli.net/
On Fri, Jan 2, 2009 at 7:28 PM, Curt Thompson <Curt.Thompson(at)verizon.net (Curt.Thompson(at)verizon.net)> wrote:
[quote]
John,
I'm working on making "Top Longeron Gusset" (7F3-3SP) and I noticed the problems you posted a while back on the Zenith List. Do you think it would be a good idea to make that part about 100mm wide (rather than the 85mm in the plans)?
Curt
Plans building CH701
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jgswartout(at)gmail.com
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| Posted: Sat Jan 03, 2009 9:58 pm Post subject: Top Longeron Gusset (7F3-3SP) |
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Sorry---I erred in thinking Curt was writing me directly.
John S.
On Sat, Jan 3, 2009 at 3:47 PM, John Marzulli <john.marzulli(at)gmail.com (john.marzulli(at)gmail.com)> wrote:
[quote]I think what Curt is referring to is the issue I had with the top gusset and rivet spacing.
http://701builder.blogspot.com/2008_01_01_archive.html
John Marzulli
http://www.GenevieveMarzulli.org/
http://marzulli.smugmug.com/
http://701Builder.blogspot.com/
http://www.JohnMarzulli.net/
On Fri, Jan 2, 2009 at 7:28 PM, Curt Thompson <Curt.Thompson(at)verizon.net (Curt.Thompson(at)verizon.net)> wrote:
| Quote: |
John,
I'm working on making "Top Longeron Gusset" (7F3-3SP) and I noticed the problems you posted a while back on the Zenith List. Do you think it would be a good idea to make that part about 100mm wide (rather than the 85mm in the plans)?
Curt
Plans building CH701
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