I wanted to use a 4x6 for a beam for two swings, with eye bolts with washers through the whole beam vertically. However I do not have access to 4x6. I can buy two 2x6, but how would bolts work? Since bolts would be in between of two 2x6 I am thinking the holding capacity is not as high as through a 4x6 because of the gap between two boards.
Any thoughts on how to hang two swings on two sandwiched 2x6?
Yes, you can, if you fasten them together well. The whole is greater than the sum of the parts, as they say, because stiffness and twist resistance are a matter of the cross-sectional aspect ratio. This would also result in a lamination, which is actually an improvement over a single timber because of the variation in grain and knots.
Use pairs of 2½" corrosion-resistant screws every 12-16", or use staggered, galvanized or stainless bolts at the same intervals.
