Dear all
First just want to say that the model I am building came from the Lower Hudson Valley paper model site of J. Leslie and I also found the basic instructions article there excellent.
The process I am using to enlarge the 1/48 model to 1/24 is as follows: I print off the 1/48 model as usual. Then I arrange the parts physical onto pieces of A5 (which is exactly A4 folded in half). Then since A3 is 200% of A5, I photocopy an A5 sheet of parts, enlarging by 200% on A3. This gives me the parts at 1/24 scale. Some parts are so big they do not fit onto A5 and so have the be cut into smaller bits.
One draw back with this method is that colours are a bit "duller" for the 1/24 scale. A better way would be to take the 1/48 scale pdf and take A5 sized regions and print them directly to the printer at 200% onto A3. Unfortunately I do not know how to do this. If anyone knows a really easy way of doing this (that a tech novice would understand) I would be very grateful to learn how.
Ok, now to some things I specifically found when doing the 1/24 F1 engines.
I found that the former for the nozzle extension (part 2 of page 1) and the former for thrust chamber (part 13 of page 11) had to have a larger outer circumference than drawn (about 1mm "further out"). Best to check before cutting triangular joining tabs.
When making the turbine exhaust manifold (parts 5 to 9 on page 6) the red "centre lines" are slightly off when enlarged to 1/24 and it is best to draw new ones and work to them (it makes a difference in the end). Also just for reference I found that for the "petals of part 9" that tabs A,B,D,F,H,J,L are glued to part 6 whereas tabs C,E,G,I, K are glued to part 7. (Really take care lining up petal A since this "fixes" everything that follows).
Finally I found the "lugs" (parts 19 and 28 on page 6) are best attached to the combustion chamber and heat exchanger (parts 12 and 18 on page 11) after you have made the high pressure LOX and fuel duct (pipes from parts 33 to 36 on page 16).
I found it difficult, using just rods and dowels, to roll and make small diameter pipes. So a friend made a "rolling" tool for me (photo below)
It is simply a BBQ fork stem, bent and two dowels stuck on each end as handles. It works great for me and does not hurt finger tip joints. Very controllable and can apply much more pressure than fingertip pressing. It is easy to use for rolling cones as well.
The finished 1/24 F1 engine is approx 25cm high and 15cm in diameter. If you like engines I am sure you would enjoy making one of these.