Wednesday, August 10, 2011


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..

Monday, February 7, 2011


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..

Tuesday, October 12, 2010

Frame 10

Frame 10 is another major frame as it holds the attachment brackets for the rear wing spar brackets.It consists of a double frame of U shape and sits under the pilots seat.Material is aluminium of 1.2mm thick.The buttstrap used to connect the webs is the same as Frame8,s although rivet size has grown from 1/8th" to 5/32nd".

Also where the bottom cutouts are for the longeron there are stiffening doublers that differed from early to late Mk Spitfires.Internally is the same spacer arrangment as F8 although at the bottom corners there are U Brackets to help distribute the loads of the wing spar brackets.At the top corners of the port side are holes for fairleads to take the rudder and elevator trim cables.

Sunday, September 19, 2010

Frame 9 and control box

Frame 9 sits just in front of the pilots seat and is fairly complicated as it is the centre structure for the Spitfires control column and rudderpedal assembly.
The assembly consists of three hatsections,one at the bottom and the other two for the port,starboard vertical members.These are 1.5" x 1.5" width and height with a .6" flange out of 20guage aluminium.The tricky part is that the section is twisted slightly due to the curvature of the Spitfires fuselage at that point.
This assembly is diagonally braced with "squared off round tube" of 1"x1"x .036".At the centre are two vertical channels.These are to provide strength for the aileron control drum mounting.Further out are two more channels.These hold a spherical,self centering bearing for the rudder bar slides to move through.
The control box starts at Frame 7 and continues through to Frame9 at its rear using diaghragm members and bracing of 1" and 3/4" square tube.At the front the assembly holds the Spitfires rudderbar which pivots on plates mounted off the F7 diaghrams and longditudal bracing for the pilots heelboards.Just behind F8 sits the second set of diaghrams and bracing of which the pilots control column sits.This pivots in two blocks mounted on the bracing assembly..

Tuesday, July 27, 2010

Frame 8

Update time again.This is Frame 8 which every Spit lover will know as the one below the instrument panel.Actually the instrument panel sits back a bit from the aft edge of frame 8 by about 40mm.
The frame is in 4 main sections,port forward,port aft,starboard forward and starboard aft,These are joined together by buttstraps at the bottom and the compass mount plate at the top.Joining fwd to aft is by c channel brackets that radiate around the frame and by a coaming that wraps around the internal shape.At the top is a capping strip where the Blind Flying panel mounts bolt to.On the webs are the kigass primer,fuel tank selector and pulleys for the Uc locking cables.On the forward side up top is the bracket for the fuel tank bracing tubes.The compass bracket also bolts up and is offset to one side.Think this is to give a pilot a better look as the control column would block the view.At the bottom is the diaphragm attachments for the control column and rudderbar heel assembly.

Monday, June 7, 2010


Next frame back is frame 7 which is the rearmost support for the bottom fuel tank.Virtually the same type of frame as per 6 but a bit deeper due to the drop in the fuselage profile.The top curve is exactly the same as frame 6 due to the mounting of said fuel tank.Also this is the start of the Spitfires cockpit as the diafragms for the rudderbar bracing start here.Just behind frame7 is the cockpit front fireproof bulkhead.A 3D design of the frame and placeholder bottom fuel tank to see if it here...all will fit.

Wednesday, May 19, 2010

frame 6

Working back is the start of the front fuel tank area.Here we have the first frame which is frame6.This is a web at the bottom along with hatsection side members that terminate at the datum longeron.The top curve of the web matches the profile of the bottom skin of the bottom fuel tank.Triangular gussets strengthen the web.