RDF1249@aol.com wrote:
> I plan to build a [32 hole rim to a 40 hole hub], skipping
> every 5th spoke on each side of the rear hub.
> How to figure the spoke lengths, that is the puzzle.
Although it is more work, I have done it often enough by just lacing normally, using the length calculated as if it were the correct hub. Then replace some spokes with longer/shorter when it becomes clear how much is needed - which is well before final tensioning. Not a great plan if you have to order in the spokes ahead of time, but easy enough there at the shop with a full selection of spoke lengths at hand. Certainly less extra work than drawing the wheel in 3d in CAD software!
I have also hit it right on the first try by guessing ahead of time how much longer/shorter to go. Where to go longer and where to go shorter is not rocket science: clearly the spokes that angle away from an empty hub hole will be shorter than the norm, and spokes crossing over an empty hub hole will be longer. Spokes not adjacent to an empty hole won't differ much from the norm. Given the tolerance for spoke lengths - they don't have to be exactly right - I recommend just taking a stab at it.
Mark Bulgier
Seattle WA USA