2016-01-16: I posted this message on the Cozy- and Canard-group:
“I have searched the archives regarding differences between the large M-drawings and the smaller drawings and found several threads discussing this.
I am now starting to build the wings and found immediately that there were differences in the size of the wing templates when I compare the smaller drawings and the large drawings.
I measured the template for BL 67.5 and found that the overall length from LE to TE is 42 11/16″ using the small drawings compared to 42 1/2″ using the large drawing – 3/16″ in difference.
The small drawings are also 1/8″ higher than the large drawings on the thickest part.
The question is: Which drawing should I use? Does the differences I measure matter at all? My plan is to use the large drawings for all the templates, both wings and jigs. The wings will then have a wing chord that is 3/16″ less than using the other drawings, and be 1/8″ less thick. However, the overall symmetry will be OK I guess. And is it possible to say whether the one drawing is more correct than the other? I can’t seem to find any specification of the overall length of the templates.”
I didn’t get any spesific answer other than that many other builders had struggled with the same problem without finding an answer her. The root cause of the problem is that the drawings where hand-drawn initially, without any written measurements. Then the drawings have been copied and copied and any error in the scaling in the photo-copier will be duplicated further. So – how can we tell which drawings to use?
However – I did find a clue on page 2 of chapter 19. It says something about the dimensions of the inboard block after cutting, it says the the legth on the inside should be 23.4″ and the outboard 25.1″. With these two values I could measure the paper-drawings for the BL31-template to find the version that matches the 23.4″ best. I soon found that the large scale drawing was accurate, just under 1mm in difference. I found the same when measuring the BL67.5 template. The original drawings (the small drawings) was as stated before larger than the large drawings. I will then continue to use the large drawings from now on, but always control the two sets of drawings.
An other important issue I discovered was to check the rulers. I have several carpenters rulers in my workshop, and when I controlled them against each other I found that a couple was way off, approx 5 mm (1/4″) on 2 meters (78″). This is old news, but it’s important to throw away the rulers with errors.