I've got a torch and I've got space, now I'm stumbling with finalizing my frame design as I keep designing it over and over on paper (and just started using BikeCAD) and I can't get a long enough head tube to allow me to have a horizontal top tube AND ample standover height.
After riding lots of different bikes, reading a few framebuilding manuals and researching the internets, I've decided on what I want my frame to be. I've got a long torso and short legs and usually am comfortable on frames that are "too big" for me but that means I have no standover. This is usually fine but for this bike, which will be doing Cyclocross/off road duty as well as commuting, standover is a must.
This is what I require:
50-52cm (c-c) seat tube
55.5cm (c-c) top tube
Relatively high BB
Clearance for 700x35 tires
Here is my problem: I am somewhat limited by the lugs I have and also by the pre-bent fork tubes I will build my fork from. I could buy different lugs but $ is tight right now and I don't want to spend too much on this first frame as it might turn out junk.
Head lug: 74*
Seat tube: 74* (not 100% sure about this. It isn't marked and I'm measuring with an adjustable set square. Short of using a laser is there any way to tell definitively?).
DT lug: 60*
Fork Rake: 56mm
Here is a screenshot of my design. This design almost works but the heat tube is my absolute minimum length and the standover (with 700x32 touring tires) ends up at about 32". Though this is hard to tell as I can't figure out how to have the program tell me the standover and this is my calculation.
If I give in and make the top tube slope 2*, I think it would work and isn't too bad for aesthetics but I'm worried I wouldn't be able to manipulate my lugs enough to accommodate it.
Here is the design with a sloping top tube and a shorter (50.5) st.
Any suggestions? Grow a few inches, maybe learn to fillet braze?