Bathtub Fitting Analysis: Fokker vs Lockheed 88a 2

[inertia4u]

Ladies and Gents,

I am sure a lot of the stressers here have come across the ol' Lockheed Memo 88a dealing with analysis of bathtub fittings. However, I am looking for a copy to a reference that was used in a report that I have in front of me: Fokker Data Sheet Th-3.584.

I presume that this is also a bathtub fitting type analysis, however, I do not have a copy of the reference.

Has anybody seen this and give me some insight on the differences between the Lockheed and Fokker versions? Does anybody have a copy of it that I can read?

Thanks in Advance,

Nert

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Nert

 

[edbgtr]

Hello Nert
I have a copy of the Fokker document, but unfortunately I cannot let you have a copy, it is not possible from where I am to do that.
I have however compared it with the SM 88a. That again is difficult to do without a lot of analysis work because the Fokker document does not use charts, but they seem to have done some curve fitting to the original SM 88a data.
I can tell you that the TH-3.584 is identical to the Bombardier B3903003, which looks like it is a direct copy of the Fokker document, fitted functions and all. If you can lay your hands on that, you will be able to perform a comparison with the SM 88a method.
Hope this helps.
Ed.

 

[Sparweb]

Nert,

I may have what you need. sparweb@hotmail.com


Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

[inertia4u]

Thank you both very much! I happened to find a copy of the Bombardier B3903003 - but I haven't had time to delve into it yet - I really appreciate the help from both of you!

Cheers,
Nert


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Nert

 

[jetmaker]

Sparweb,

I'd be interested in the Folker Data Sheet if you have it. My e-mail is spence7471@yahoo.com

Thanks,

Jetmaker

 

[Sparweb]

It's the Bombardier doc that I have, not the Fokker one, Jet. If you're still interested, I can send it right away.

Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

[jetmaker]

SparWeb,

The Bombardier document would be great. It is often amazing how different companies methods are so similar to eachothers. Hehehe.

Thanks again SparWeb.

jetmaker

 

[johnchance]

I would also appreciate the Bombardier information. My email is mark1@kendra.com

Thanks

 

[crackman]

Hi All

Just a note of caution on the bathtub fitting method. Although the Lockheed method has been around for years and years, it was based on a significant number of tests and the old versions of the SM actually listed the LR test report from which the method was derived. This is important because the SM does not clearly define its limitations in applicability to various designs of bathtub fittings. The sketches in the SM are truly indicative of the types that were tested. Soo, be very careful as to how you implement this method for bathtub fittings that vary significantly in design and geometry from those tested. Alas, you must have the test report to know all this.

Good luck

James Burd
FAA DER - Structures/Fatigue and Damage Tolerance

 

[spike31TFW]

I would like to second the warning from crackman.

I have been using the Lockheed "method" for 20+ years now and I can tell you that in fatigue prone areas this method may not be conservative.

On more than one occasions we have had to completely redesign components using FE fitting models (most times using solid elements, non-linear approaches: large disp, nonlin mat props) due to the oversimplifications inherent in this method.

Given the relative ease with which solid models can now be meshed one should reconsider the usefulness of this method.