Originally Posted by
DCB0
No, they are not. The cut (mitred) end of one tube is shaped to closely fit onto the face of the adjoining tube. There is usually a vent hole cut in the adjoining tube, but not a hole the tube fits into.
True for the TT/ST and TT/HT and DT/HT joints, but I've had lugged bikes where the ST and/or DT joints with the BB were open. Any ideas about this sort of construction?