Maxsurf Structure, problem with calculating stringers, what am I doing wrong?

Question

I'm using Maxsurf Structure Advanced 20.00.05.47. 
 My problem is that I can't seem to get all of the parts, mostly the stringers but also some frames, to calculate properly and produce the right shapes. 
 The model I'm working on is a modified version of a boat I designed using Maxsurf 15 a few years ago. The last time I was working on this design I didn't run into any issues, but I think something about the way I went about making the changes has caused my problems. 
 The model is a 10 m hard chine aluminium boat with integrated superstructure, my process for altering the design is as follows: 
 
 I opened the design in Modeller Advanced 20, and made my changes (an increase in beam from 3 to 3.5 m, change in the shape of the transom by altering a trimming surface and increasing the length of the superstructure) then saved it under a new filename. 
 Then I opened the design in Structure and defined all of my parts from a blank canvas since the design had changed enough to require different frame spacing and so on. 
 
 My problems started on calculating the new structure, it calculates everything without errors, but some of the part shapes don't make much sense: 
 
 The boat includes broken frames that ring webs under a floor deck (defined by a surface and plate) and open side webs above this, the frames calculate but are asymmetrical above the deck even though all the settings and dimensions are symmetrical. 
 Many of the stringers do not break correctly at the bulkheads, instead they form triangular splits on one side, or in some cases produce a part that folds back on itself as shown in the pictures below. 
 
 The shell expansion drawing also shows lots of odd spikes in the region of the superstructure around where my frames and stringers are doing odd things, so I think it is all most likely caused by the same issue with the model. 
 (and yes the bulkhead at the aft end of the cabin is meant to have that extra panel above deck to port) 
 Screenshots: 
 Model render with parts 
 
 Shell expansion 
 
 Lower deck stiffener 
 
 Frame 7 halfway along superstructure 
 
 (note bottom edge is different on each side) 
 Where is my problem coming from, thoughts?

Phil Christensen · Accepted Answer

This is a nice model Jeremy. Regarding the frame, I think you have done as well as you can there. The way you have set up the variable web depth opening looks right. The bevel at the bottom is just due to an interaction between the sloping geometry of the side and the radius on the bottom. 
 For the shell expansion, ensure you set the surface type of all internal surface to "Internal Structure" rather than hull. Also just show the surfaces for the hull itself (no decks, internals or superstructure) and then calculate the shell expansion. It should come out fine.