Longerons

Not yet I hope..After a horrid winter have been starting to dig myself out of a hole I hope..
The Spitfire is held together by longitudinal members that hold the Frames together.There are three main members,the Spine,the Datum and the lower..
Starting with the Spine this member starts at the top of Frame11 and continues down the top of the fuselage to Frame19.This is a V shape with bent flanges that the top skins rivet to.
The datum is as it sounds a Longeron that follows the Datum line of the aircraft.This is a "U" shaped piece with flanges to rivet onto the side skin.It starts at Frame5 which the top engine mount bolts to and goes back 47 inches to Frame 14 only.Just after frame 13 it tapers back by the centre being cut out and the flanges bent to a single point where it connects to a bracket.
The bottom Longerons are situated at the bottom corners of the aircraft and split into Forward and Aft sections,both of different construction.The Forward section is a fabricated member consisting of an L shape and C shape riveted together.The top inner edges straight and the outer edges curved to suit the fuselage.This starts at Frame5 and using big brackets bolts through the bottom spar to accept the bottom engine mounts.Going back it ends at Frame10 where the rear wing mount sits.There it changes to a single "W" shaped member which curves back all the way to Frame19.In side plan it is straight but in plan view it matches the curve of the fuselage.Also due the curvature of the frames the angles change,same as the datum longeron.The two sections at Frame10 are Spliced together by an angled plate.
Various triangular and angle brackets tie the frames into the Longeron members and all different.some designs are WIP so will update when finished..

Frame11

Well over the xmas break and so back on deck with musings on drawing lines on a computer.Frame11 is probably the most well known of the spitfire frames as it is the main hoop behind the Spitfire pilot.Also it mounts the pilots seat off it and carries the armour plate to protect him/her.The structure is a double frame,the last in the cockpit section and is joined by butt straps,the lower ones also carry the mounting holes for the frames diagonal braces.There are no internal spacers but a reinforcing channel does come down from the frames shoulders internally.This evolved throught the spitfire timeline as more powerful engines came available which nescitated reinforcing.At the datums are butterfly gussets to tie the datum brace and the diagonal braces together.This datum brace held the mountings for the seat mount and armour plate.Just under the shoulders are the cutouts for the canopy rail on each side.The inside of the frame holds an internal C coaming channel and also the top shoulders.On the back of the frame is the mounting plate for the Spitfires Voltage regulator which is held on by 4 bolts.On the front is the pilots head armour plate.On the rear bottom of the frame is brackets and gussets for the elevator bellcrank assembly.Front face of the frame are various angle stiffeners and on the back begin the intecostal brackets for the rear fuselage shape.

The frame changed shape from the MkIX to MkVIII with the internal curve being different.This was to give added  material and strength under the frames shoulders.The inernal channel going from the short shaped piece to the long internal C channel that ties in with the inside C Coaming channel.Here are some pics..