I was taught, way back before CAD, that the guy in the shop should have to do no adding or subtracting in order to make the part - no matter what reference he chose to use. I was also taught in the shop to never scale from the prints.
Since the pictures are taken from a screen, they may be a scan of printed plans which were full size drawings. There are lots of parts like this on the Hummelbird plans, trace the part, cut it out, drill. Would be nice to have better plans, but it has worked so far.I have seen plans like that where the part is drawn actual size, you just simply trace the drawing onto material, cut and drill on the lines without bothering too much with things like dimensions.
OK, I can not stand it. I AM an expert on this, having been technical leadership in three different major companies in two different industries, neither of which were aviation related (Cars/Trucks and Guns/Ammo). Drawing defects are like rats and ticks. There is never just one - if you have seen one there are almost always lots more that you just have not seen yet. Drawings have to DEFINE what is to be made and make it possible to check the parts afterward too.I'm impressed with the experts who can judge a whole set of drawings by looking at only 10 square inches of them ...with absolutely no context to the rest of the drawing.
Yeah, these plans are pretty sloppy but I wouldn't rag on them too hard without seeing the whole set. You can take a tiny snapshot out of any set of plans and make them look bad.
Maybe the angle is obvious from the drawing right next to this one, maybe the 1/4" measurement is right next to a note that says "Edge distance". There's no way to know without seeing the whole thing.
EVERY set of homebuilt plans starts out with a few problems. Just let the designer know so he can update his drawings.
AHC sadly gone the way of a lot of the old suppliers https://stunthanger.com/smf/open-forum/ahc(-america's-hobby-center)-who-remembers-it/When I started building model airplanes at 8 years old , I also started scaling up the magazine drawings to build the models. Didn't have the money to order the plans.
Just saving my pennies to buy material at the hobby shop or order from AHC. If you don't know what AHC is, you are not an old model airplane builder
Most people today needs to be told how to do most anything and without instructions they just stop. No problem solving skills what so ever.