This method is the old, original one for creating layout patterns. I was taught it years ago in an engineering drafting course. It requires very accurate dimensioning from datum planes. Extrapolation from the small scale drawing on a drafting board to a large diameter pipe size, therefore, may result in significant dimensional errors. Also, with the everyday use of computers in drafting, it may be difficult to find a draftsman or engineer who is familiar with this manual method. Nowadays, an appropriate CAD program can turn out extremely accurate cutting templates in a fraction of the time required by this manual method.
I agree that certain technology would help. The availability of equipment to do this is a variable. The sketch on the website was made with a $45.00 cad program however a plotter to make a full size template would be a significate investment. As would a CNC burning machine.
The ordinate lines for the pattern can also be calculated I'm sure but I don't know how.
A soapstone, string, and tape measure may not be as precise or as easy but they are available.
A 3rd party detailing company would be a way to go provided thay are not too proud of their technology.
Have a nice day
Gerald Austin
On templates too big for a regular printer, we often just print out the different parts with reference marks and cut/tape them together. I has worked very well for us.
Ours are printed on 30 x 42 paper and if it is still too big, we cut and tape as GRoberts said they do. Oh, ours were created in XSteel by our sub-let detailer.
John Wright
Just another suggestion--
Unless you really want to layout and cut the pieces yourself, you might try to purchase the pieces pre-shaped so all you have to do is roll and weld.
Many suppliers use burn table programs that cut any shape you want. We use SDS software with our plasma table, which allows us to enter the dimensions, number of gores, weld joint requirements, and etc. Then plates are loaded on the table and burned to size. No hand layout necessary, we even make small notches that accurately mark our quadrants for us.
I'm sure there must be some fabricators or suppliers near you that could give you a price, and you might find the true cost is not that bad.
Chet Guilford