<html><head></head><body><p dir="ltr">The minimum moment of inertia of the combined section of the stiffener plus an effective length of the pressure boundary shell may be specified by design, but in any case is to be calculated in consideration of the minimum at the locations where any holes exist. Holes in the flange are far more detrimental than holes in the web, with the mininum impact hole being a hole which is coincident with the neutral axis across the combined section. (i.e. holes drilled in the center of the web of an I-beam have the least impact).</p>
<p dir="ltr">Better than drilling holes would be to simply clamp to stiffener rings, or weld on brackets or studs such that no material is removed from the stiffener section. Otherwise you do have to account for the reduced moment of inertia of the stiffener section at the hole location in your buckling, inter-stiffener strength and stuffener tripping calculations.</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On September 7, 2017 6:51:03 AM PDT, Steve McQueen via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">All, as most probably know a K-250 has internal angle stiffeners (L). <br /><br />In my rebuild I have avoided drilling any holes in the web portion of these stiffeners (actually had some existing holes from the original build welded up/filled). However, I am finding it would be nice if I could drill a few small (1/4") holes to help mount some interior parts. I believe I am looking at 1 to 3 of these holes max. in any single stiffener web. <br /><br />Calculating any reduction in functional strength that might result from a few small holes isn't straight forward. I guess I am looking for some feedback from those who understand the web function of an L stiffener better than I.<br /><br />My guess is this wouldn't be a significant issue and I an being too anal.<br /> <br />Thanks,<br />Steve<br /><hr /><br />Personal_Submersibles mailing list<br />Personal_Submersibles@psubs.org<br /><a
href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br /></pre></blockquote></div></body></html>