Originally Posted by Stockmanreef
How much of the bolt should stick through the firewall? What is the minimum amount of threads that should show on the end of the bolt after torquing down the nuts?
My upper bolts seem to too short like stated above. I have about 1 thread showing before torquing down on the bolts.
The lower bolt will have lots of exposed thread.
"A common rule of thumb for evaluating whether an installed bolt is the proper length has always been that up to three thick washers are allowed (if more than three are needed the next shorter bolt should be used), and that at least one but no more than three full threads of the fastener are to be showing beyond the nut. This rule of thumb works for the AN365
nuts that have been commonly used on RVs for years.
Some of the newer RV kits use the all metal MS21042
self locking nut. The long standing rule of thumb will not work for these nuts because they are shorter in height than the AN365 nut. For these nuts, modify the rule of thumb to ďat least three, but not more than five threads showing.Ē This rule of thumb will still allow for meeting the 'maximum use of three washers' rule.
You may have to educate any technical councilors or airworthiness inspectors that perform inspections on your project. Some
inspectors are not familiar with these smaller sized nuts."