You have to look at it case by case, but for a typical fuselage truss square tubing will be heavier than round if both are optimised.

So in column loading and in bending the square will take 1.7 times the load of the round tubing, for this example. Torsionally the square is about 30% stronger, but it also about 30% heavier. In shear, the sqaure will take a load of 4800 lbs and the round 3775 although tubes like this are of course rarely used in pure shear. Support the same tubes at the ends and the square one will support 73 lbs hung form the center before failing and the round will support about 42 lbs (in reality of course other factors come in such as local buckling etc, I'll ignore these for this example). Used as a strut the square tube will support about 1066 lbs before buckling, the round 625 Lbs. Take as an example a freely supported column of 3/4' x 065 tubing, 36' long, and the 3/4' x 065 round, also 36' long' The round tube wins on a pound for pound basis, usually.

I'm more interested in getting the biggest bang/Lb.Īs always, thanks in advance for input and answers. Square is certainly easier to use in fabrication since no 'fishmouthing' has to be done to intersecting tubes. Maybe the answer is different for torsional strength vs. I was always under the understanding that # for #, round was the stronger shape compaired to square. 3/4' Round, but weighing the same in terms of #/Ft.? basis? Which would offer more bending resistance and handle a higher compression load, a round tube with thicker wall or a square tube, but with the same O.D., ie. How would they compair in bending and compression loads? Considering the round is +/-75% of the weight of the square, is the resistance to bending and strength in compression compairable, higher or less? Is the load comparison somewhat similar to the difference in weight? Tension I would expect to be reduced by the reduction in cross section area.Ī second way to ask the question would be how do they compair on a Lb. I'll qualify that with an example 3/4' X. When considering the resistance to bending and the compression strength of square tube vs round tube, which is 'stronger'.

Rec tube password