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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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 Posted: Mon Oct 29, 2007 5:46 pm Post subject: Fwd: Re: Attachment fitting at top of lift struts. |
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All,
Rex wins the award! (Whatever that may be.) He found the
fabled 14g number, (see attached,) associated with a lift strut test.
Using the data shown and my Kitfox IV geometry I calculate a single
strut load of about 6500# at failure. I did find a 1/4x1/4 rod end
with a 6190# ultimate, (AW-4, "
Female Rod Ends, High Strength Alloy - Precision",
) but the only 1/4x5/16 I can find is a GMW-4M-595, "
Female Rod Ends, General Aviation - Precision", which has an ultimate
strength of 3359#. (My rod end is marked MW-4H-12. I've got a message
into Aurora to learn what that might be.) So I'm guessing that Denney
used the high strength rod end with the 6190#, or thereabouts, ultimate.
Therefore, pending confirmation of my rod end design, I
stand corrected, and apologize to all for my calculations. (I assumed
my rod end was the GMW, which as you can see has only half the
strength of the AW, but still gets you over 6 g's ultimate at 1200
pounds gross.)
I also checked the 5/16" rod and it was good to 11g, based
on 1050# gross, (125ksi rod,) which is close enough, and the 1/4"
bolt, which is good to about 16g, based on 1050# gross.
The moral of the story is: when you replace your rod ends,
make sure they are high strength alloy if you want the full 14g
capability. (Now I believe I owe Dave a calculation of the strength
of the outboard section of the wing.)
Guy Buchanan
| Quote: | Delivered-To: bnn(at)nethere.com
X-Authenticated-User: rhefferan.centurytel.net
Date: Mon, 29 Oct 2007 10:00:47 -0600
From: Rexinator <rexinator(at)gmail.com>
Reply-To: rexinator(at)gmail.com
User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803)
X-Accept-Language: en-us, en
To: Guy Buchanan <bnn(at)nethere.com>
Subject: Re: Attachment fitting at top of lift struts.
Guy,
Here are a couple of scans of the load tests that I found in the
newsletters I have. I'm sending GIF files because they are smaller,
but can convert to other formats if you like.
The file "KF2strut-test.gif" was on the front page of a newsletter
that did not have a date printed at the top like the others I have.
However you can see that it must have been around mid-1990 since it
describes the test as having been performed in April 1990 and then a
factory Fly-In was scheduled for Sept. 1990 in another article.
The second file "KFwing-load.gif" was on the back page of "Kitfox
Times" another publication by Denny Aircraft dated Jan/Feb 1992. I
seem to remember details mentioned with this photo from another
printing which defined the weight of the sandbags and the simulated
G load. I may be confused so don't quote me about that.
I hope this helps,
Rex Hefferan
Guy Buchanan wrote:
>At 03:54 AM 10/24/2007, you wrote:
>
>>Guy,
>>I've had a few unexpected things come up and I've been unable to
>>get to my old papers. I now looks like I'll be away from them
>>until next Sunday. I'm sorry about that, but I'll still plan to
>>look for the article then.
>>Rex
>No problem Rex. We've been having some adventures down here in San
>Diego and are fairly distracted at the moment. Thanks for thinking
>about it, though.
>
>Guy
--
Rex Hefferan
SE Colorado / K-II / 582-C / still waiting repairs
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Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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dave
Joined: 22 Sep 2006
Posts: 1382
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| Posted: Tue Oct 30, 2007 1:40 am Post subject: Re: Fwd: Re: Attachment fitting at top of lift struts. |
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Guy, Excellent follow up !!
I have the same document that Rex provided you as well as another one if you look that will read " at 950 lbs maximum , the Speedster is capable of positive G aerobatics, ultimate load limits of 9 g _ and 4.5 G - " it is scanned and poor quality but i will try and get a better scanned copy.
With that being said the Speedster has wings that are 1 1/2 feet shorter each so the outboard flex will be a little less than on the long wing model..
And Guy when calculating this I think that the .058 spar had a longer stiffener inside at the wing strut attach point that the 065 spar but as usual I stand to be corrected.
| Quote: | (Now I believe I owe Dave a calculation of the strength
of the outboard section of the wing.) |
| | - The Matronics Kitfox-List Email Forum - | | | 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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