<HTML> In a message dated 11/10/03 7:17:11 AM, mfarrel2@tampabay.rr.com writes: <BLOCKQUOTE CITE STYLE="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; = MARGIN-RIGHT: 0px; PADDING-LEFT: 5px" TYPE="CITE"> I've made myself a little pneumatic contraption for laminating ribs. I see= m to have just about everything worked out for proper function (actually, wo= rks quite a bit better than I had hoped!) except for some excessive jig fl= ex. I have a 1.5-inch-thick Delignit pinblock incorporated into the jig = for stiffness, but I still seem to be getting several millimeters of flex = in the middle of the 5-foot long jig when I pressure up. So I think the solu= tion is to put a couple of angle irons, or steel channels along the length= of the jig. This thing is getting VERY heavy, so I prefer to not use any mo= re steel than needed. </BLOCKQUOTE> I've no science background, but i've made numerous structural steel jigs.<BR= > My first jigs used steel as a monoblock material, a "one piece big enough to= resist" approach. That is off target. What you want is a little teeny bridge structure. In oth= er words, multiple pieces of steel with lots of triangle shapes for rigidity= . This way there is not too much mass, but great rigidity. If you don't want= this large "fab" job, use a steel channel or even an "I" beam, but then it = will be heavy; I store my big jigs outside and paint them. A necessity after= my first 14 foot long soundboard jig. BTW don't order steel from your frien= dly supplier, check the scrapyards for material. You can't pick and choose a= s much, but it's way cheaper. You may consider this close to dumpster diving= , but It is invaluable to the machine builder. At the scrapyard you don't wo= rry so much about the calculations, just buy way over what you need, and sta= rt an outside storage rack area. If you start fab work like this, access a s= awzall for cuts, or a torch. A resinod cutting disc in a tablesaw is a BAD i= dea. If you have specifics shoot them back, happy to answer from no-training= and 12 yrs. of practical experience. Glenn C.</HTML>