Heya,

I'm completely new to frame building. So new in fact, that I've never actually built a frame!

I'm about to buy a fairly inexpensive set of tubes with their appropriate lugs, and braze em all together. The first hurdle I've seemed to have hit is seat tube length. While reading the Paterek Manual, a formula is given to help find an approx. seat tube length. I'm completely confused and not sure how to get a result which seems about right.

So for myself:A = Inseam length in centimeters with stocking feet

B = Bottom bracket height in centimeters

C = Crotch Clearance 4 centimeters for touring and 6 centimeters for racing

D = A-(B+C)

E = Seat tube angle

F = Complement of angle E

After measuring the rider's inseam and finding the other variables (B & E will be covered later), 2 sides and three angles will be known. With that knowledge, the Pythagorean theorum can be applied to find the seat tube length. The following formula will give the seat tube length. All that is needed is a hand held scientific calculator:

D [sec (F)] = Seat Tube Length

A= 85cm

B=6cm

C=6cm

D=73cm

E=72 degrees

F=18 degrees

So using the formula:

73 [sec (18)] = seat tube length.

My result = 76.76

This is wayyyy too large for a seat tube. Not sure where I'm going wrong.

Any suggestions?