Here are the first photos of how I built the camel back gas tank. Photobucket insists on reversing the order that the photos were taken so the last ones are first. I added information on the bottoms of the photos.
I'll repeat it here. I used a piece of poster board that I bought at the Dollar Store. It's 19" long and 8" wide and it's marked off in 1" squares. I haven't decided just how to list the measurement yet but I'll add them tomorrow.
I measured from the right to the left on the grid. You'll need a ruler that is marked in 16th's of an inch. I used an adjustable square. Measure up from the bottom on each line of the grid. Just draw a small pencil line across the line on the grid like you were crossing a t. When your finished mark each intersecting line with a Sharpie. I used a red one to make it stand out in the photos.
The Sharpie mark is where you need to drive a nail in. Mine are 2-1/2" long and they need to be set into a piece of plywood or MDF or some suitable wood so they can't move. Make sure they are straight.
I use an old metal yard stick to bend around the nails. Use double nails at each end to hold what ever you used to bend around the nails in place. Make sure the piece bent around the nails is in full contact with them. Run a pencil in between the nails along the bent piece and this will give you the shape of the tank. You may need some nails to hold whatever you bending around the nails up against them.
You will see a straight line with no nails. This is the part that goes up against the seat stay. You just need to draw the line to join the top and bottom of the tank. This angle was made for my bike frame and the angle on your seat stay may be different. The bottom line for the tank should stay the same and you will need to shorten or lengthen the top tank line to match your bike frame.
I'll post the information for the oil tank soon in case you decide to add one.
If you see something I've missed or done wrong or if you have a question please let me know here or PM me by clicking on my name and choose the Personal Message prompt I'll get back to you as soon as I can but it will be quickly.
Thanks for staying with this build. It's been a long ride.
Steve.
http://i866.photobucket.com/albums/ab228/speedydick/Indian Tri-car Build/DSC_0013_zpsfzsurp73.jpg