Which fastener to choose

[snoopyflys]

Does anyone have a primer on how to determine the proper fastener? While not being an engineer, I have been trying to understand the how come?s and what for?s a particular screw, bolt, blind rivet, etc. is chosen/used in assembling the various components on my airplane. I?m hoping that a builder before me has had a similar quest for knowledge and is willing to share what they were able to find.

[Vlad]

I started with Jepp A&P technician general textbook then got a hard copy of AC 43.13 - Acceptable Methods, Techniques, and Practices. Then Tom had a promo for Genuine Aircraft Hardware Book. Spruce has great catalog with detailed descriptions for free. And this very forum of course. It has MASSIVE ( as Iron put it) archives.

[pierre smith]

Just this week, I had to remove my cowl at an airport 300 miles from home and the d*** top cowl has philips screws about 2 1/2 inches apart on the top rear and I didn't have my electric screwdriver either. I almost had cramps removing those screws by hand, in 38 degree weather. Camloks would have been sooo much easier! Like we did on our -6A we built, so what goes there is your choice, one that 43.13 doesn't cover. I didn't build this airplane but I can assure you, the screws are gonna be gone shortly.

Some places need screws that are up to the loads and that's where tech manuals may help.

Best,

[Ironflight]

As Vlad said, AC43.13 is a great place to start. I was given a copy when I was 13, and digested the whole thing - all the secrets of how airframes shoudl be maintained and repaired. Lots of good stuff there - I always have a copy close by.

Paul

[terrye]

This is not the work of a moment! To properly understand the subject, first you need to know what the loads are, then design the fastener for the loads. Luckily the primary structural fasteners have already been specified by the kit manufacturer. I assume you are thinking about secondary structures like brackets, cowls etc. Vlad's recommendations are a good starting point. If you want more try your library for Bruhn's "Analysis and Design of Flight Vehicle Structures". Most college texts on machine design will have a good treatment on bolts but not so much on screws and rivets.

[David Paule]

Here are three references that cover aerospace fasteners from a technical point of view. They are all aimed at the working aerospace structural analyst.


There's a huge amount of data in FAA's version of MIL-HDBK-5, now unsupported. The FAA version is at:

http://www.apesolutions.com/spd/public/AR-MMPDS-01.pdf

The fasteners are in Chapter 8. Chapter 1 is quite valuable for explaining the various underlying characteristics of metals and their properties.

Caveat, I am still downloading the 73 meg document. The table of contents follows MIL-HDBK-5 closely and I'm basing my comments on that and my familiarity with MIL-HDBK-5.

For a good structures manual, the Astronautics Structures Manual,

http://euler9.tripod.com/analysis/asm.html

is decent enough. It covers roughly the same data as Bruhn but without the tutorial content. For fasteners, see Section B. The overall document is especially good in some areas and poor in others, it's not nearly as general a book as it might have been. But it's a free download. Nothing against Bruhn, it's one of the classics and my copy is well-worn.

Neither resource adequately covers the effect of preload on a fastener or how to obtain a reliable preload. That's covered here, still incomplete but they did catch about half of it, maybe two thirds, and once you digest this the remaining third isn't too difficult to figure out.

http://snebulos.mit.edu/projects/ref...08307_RevA.pdf

[rvbuilder2002]

Originally Posted by terrye

This is not the work of a moment! To properly understand the subject, first you need to know what the loads are, then design the fastener for the loads. Luckily the primary structural fasteners have already been specified by the kit manufacturer. I assume you are thinking about secondary structures like brackets, cowls etc. Vlad's recommendations are a good starting point. If you want more try your library for Bruhn's "Analysis and Design of Flight Vehicle Structures". Most college texts on machine design will have a good treatment on bolts but not so much on screws and rivets.

Exactly right.

A determination can't be made of a proper fastener unless you know what the intended load of that fastener is. The only real shortcut for this is if you are just substituting and you choose a fastener that is equivalent to the one originally specified.