here is a link on how to go about building a tuber. You can also braze or tack one together but than you have to clean up the joints. The silver solder flows really nice if you know how to use it, but it is spendy for what you get because of the high silver content.
Here is the link, enjoy.
http://www.mindspring.com/~jayk6/rcstuff/tubefab/tubefab.htm
Here is the link, enjoy.
http://www.mindspring.com/~jayk6/rcstuff/tubefab/tubefab.htm