Orientation does matter. For a given same cross section of the same type lumber, the horizontal layering in a beam is about 15 percent stronger according to a Forest Service handbook that I read about 25 years ago when I was contemplating the same construction on my KR-2 spars. The basic reason why is: Putting the layer lamination vertical will induce shear stress in each piece of lumber when it is loaded ( pulling g's, hard landings, turbulence, etc.). That is in addition to the compression or tension load that the spar pieces would be handling. This tends to break the grain along the length of the lumber. The glue (epoxy) that you will be using is much stronger than the resin bonds that the tree has put between each individual wood fiber. So, the horizontal layering can handle the shear stress much better. And the thinner the layers for the same built-up cross section, the stronger will be the finished product. There is a limit regarding how much epoxy gets added versus the volume of timber in order to keep the weight to strength ratio in bounds.
Sid Wood Tri-gear KR-2 N6242 Mechanicsville, MD, USA smw...@md.metrocast.net ------------------------------ I'm about to start laminating the timber to form my centre section spars from pieces that are 19mm (3/4") thick. Is the orientation of the laminations significant? I'm not sure why but all the laminated timber beams I've seen have the lamination layer horizontal. I can do this but in this case I'd waste less wood if the laminations were vertical. Does it matter? Cheers, Tony King ------------------------------
