Decided to make a pot stand for camping. Going all fancy like and using some scrolls for decrative purposes.

I drew out my scroll, as seen in the bottom right of the photo. I used some string and measured it out. Total length is 11.75 inches, made from 3/4x1/4" flat stock. I wanted to do a taper for the inner part of the scroll, so i did some math, and figured that having a 7/8ths" taper length for both ends of the bar would look nice, so 7/8ths plus 7/8ths equals 1.75", so i started with a 10" long piece of flat stock.

I did my scroll work, bending, curling, and made the scrolls look like what i drew...but then saw that even though both scrolls on the piece matched, the runner between the scrolls was long. I took my string, measured, and found it to be 14.5" long. I thought i had cut my original piece long, so i slowed down, triple checked measurements. I cut my piece at 10", put my first taper of 7/8ths, giving me 10.875" long. Added second taper, and total piece length was 11.75". I proceeded to scroll. Made my scrolls line up, but the runner was on the long side again. Took my string, measured, and again, it was 14.5" long.

So, im stumped.  how am i gaining an extra 2"?

Make a known distance mark on the metal. Make single test tapers and scrolls.  Lay the two test tapers and scrolls on the table and measure how much middle you need.  Add the measured mark to the end of the taper and scroll one, to the measured mark to the end of the taper and scroll two, and then add the middle distance.  Make one prototype to see if the numbers are correct.  

Make several of the finished product, say 1-1/2 times the amount you will need, and choose those that come closest to matching perfectly for use.

 

Not understanding what you mean

Make sure when you measure the length of the scroll, you measure the centerline of your material, not the top or bottom edge.

When you bend iron, the outside is drawn out(gets longer), the inside edge is upset(gets shorter). The centerline does not change length.

As for your tapers, here's a concept to learn. That's learn what transitions are. Transitions are where changes take place. Where your taper starts(where you go from round to taper),and where it ends(the point).

Now stringline your scroll from beginning transition to beginning transition. Next by math or trial and error figure out how much parent stock does it take to make the taper (how much 1/2" round does it take to make a 7/8" long taper). It will take less than 7/8" parent stock(half round), to make 7/8" taper. Add the three together and make a small center punch at each end where the tapers start. I also usually mark the center of my length as well. This aids scrolling each side. Now you have the exact starting length and all your scrolls should come out the same length.

I ways lay out in chalk on my table this linear length full scale, not just the final scroll. This includes where the center punches(transitions) go. Now you have a template to lay out linearly as many scrolls as you need.

So as to your extra length, if you measured your scroll on the outside edge, you will be too long. If you used 7/8" length of half round for both ends of your taper, you will be too long. Thats how you got too much length when done.

This is basically what Glen said. Hope it makes sense.