I have seen several drawings sent out with methods of putting the dimensions on the drawings that are somewhat confusing. There are accepted methods of drawing dimensions on mechanical drawings that will help us mathematically deficient builders with what the actual measurements are on whatever is being drawn. This is just a suggestion but may help clarify when you are posting drawings.
is a good basic reference.
Roadjunkie
My past held a position where I did a lot of "detail drawings", ones used by a fabricator to build parts of an assembly, later combined to make a complete part. All of this was done in Autocad, much like what you see on the modern Vans drawings (some of theirs are from Solidworks, but the same idea)
Going way back, when drawings were done on velum with ink, by hand no less, there were some very specific ways developed to show dimensions in a drawing. Unfortunately, Autocad will allow some pretty crazy conventions, especially if you over ride the format or make up your own system. AC will also check your work, making sure dimensions are correct for the drawing, unless you have done a "hard dimension", forgetting you've done it, and moved that line later. Having said that, Vans along the way has produced some drawings with contradicting or wrong dimensions shown. Stuff happens, especially as drawings are modified. Vans has never shined in the "version management" arena. Also, different draftsmen have different styles, so that adds another layer of variability.
I won't make this into a class on dimension-ing a drawing! but be aware that just because a drawing shows a number, it doesn't mean it's correct. Especially if you find dimensions that can be added from both ends (always the risk that tolerance errors will pile up) or something was changed without a thorough check of the other dimensions, so check the numbers yourself.
The next challenge with a drawing from Vans is that they often use fractions vice decimals, or the two mixed together. Decimals are a way to show a dimension exactly, and the number of decimal places infers the tolerance intended by the drawing. Also, adding fractions together can be a pain. Reduce the fraction to common denominator and add. You can also convert all fractions to a decimal and then add, but don't be surprised if the sums are different. Generally no tolerance will be indicated on Vans drawings, so you're on your own to determine whether the intended dimension is a +- or + or - tolerance. I find this very frustrating, but once again, do the math and think thru the application before making your parts. Thankfully most of our planes are not so precise, but issues do arise.
So it turns out that this is part of the challenge, figuring out what the draftsman meant, and building your part to accomplish the task. Good luck, we're all counting on you!
