Spad VII . C1 ....Airframe Structure .

[John McKenzie]

Hello .

Does anyone know of "any" Structural Failures or any other " Safety problem" , that required alterations to the airframe or hardware , ....which occurred during the operation life of this machine .

[ Not to include the Addition of Aluminium Triangle Gussets etc., to Motor side frames ,...& the wing fabric stripping on early models from use of Tacks ]

Thanks .

JM

[John McKenzie]

Hmmm.
Not much response so far .................( but is not a Fokker)


Of course there was the change also from Alu' castings to steel folded fittings & trunions etc. in the method of wire tightening of fuselage bracing .....probably an improvement , though not certain it was driven by any problem of wires loosening , due to inherent possible fault in this design .( if that ever did happen or how often )
[And M.E. machines added weight !]

[Tomasz]

Doubled post. Sorry

Tomasz

[Tomasz]

Originally Posted by John McKenzie

Hmmm.
Of course there was the change also from Alu' castings to steel folded fittings & trunions etc. in the method of wire tightening of fuselage bracing .....probably an improvement , though not certain it was driven by any problem of wires loosening , due to inherent possible fault in this design .( if that ever did happen or how often )
[And M.E. machines added weight !]

John,

as far as I know aluminum castings were reported to crack occasionally - hence the change to folded steel fittings.

Tomasz

[John McKenzie]

Thanks Tomasz ,

Myself , I prefer the steel Fittings , which , because they may have the additional little wiring lug pieces , ....also make it better method to brace the transverse/cross bays ( from one side to the other ) , in the rear fuselage .

I have not calculated the total weights involved for each type , but probably not a lot of difference between the two methods .

I remember now that I have also read , there have been some cases where the pressed & riveted , sheet Aluminium ( back to back = H section ) with Steel outside strips ,... Motor Side frame braces , have sometimes cracked .
(However today , this potential problem is more easy overcome ).

Tomasz ,...
Any cases of Structure of Wing / Spar Failure etc... known to you ??

Thanks for posting...regards JM

[Tomasz]

John,

do you attempt to build flying replica? Do you want to replicate exact Spad VII subversion or just a best Spad to fly? If you opt for the best flying machine the late ironed out patterns would be the best indeed. Note that steel fittings were better overall. Usage of aluminum was caused by shortages of steel rather than any advantages of aluminum. The bulk of Entente steel industry was located in Belgium and fell in German hands early in the war. The situation was saved by US supplies in 1917.

What kind of engine you plan to install? After introduction of 180hp engines a couple of modifications were added to front fuselage section:
- triangular aluminum bearers were reinforced by thin steel girders bolted to upper edges of the bearers or by wooden cleats (again - due to shortage of steel) bolted to front and rear surfaces of the bearers
- additional horizontal runners between first and second fuselage spars
- additional two planar cross bracing between the runner mentioned above and
the lower part of fuselage truss.
Mann Egerton reinforced the bearers with oblique steel rods but this solution caused their Spads to be nose-heavy.

As regards wings their main construction remained unchanged. However experience proved than in flight fabric tended to by sucked between the ribs near leading edges. It obviously caused deterioration of wing profile shape. So somewhere in 1917 leading edges of the wings began to be covered by plywood fairings. Initially the fairings were added to the bottom surfaces of both wings and later to top surfaces as well. The fairings were initially solid but soon round perforations were to be introduced as a weight saving measure.
As you have mentioned the first method of tacking fabric to ribs caused some fabric tearing. So, under British influence, in 1917 French Spad manufacturers began to add 30mm cotton rib tapes and to sew tapes and fabric to ribs.

Tomasz

[John McKenzie]

Hello Tomasz .
Thank you very much for your reply & to show interest in & answer to my question .....(PM sent) .

First of all I research to find out if it has been necessary for the original airframe , to have had any alteration due to any ,..unknown (so far as to me) , found weakness .

Myself , I do not like so much the Aluminium cast fuselage fittings or the method of wire bracing used with these .
I rather prefer the later method , as used with steel fittings and single "trunnion" tensioners ( also seen on S13) ,..rather than the unusual method of wire bend/loops , (with turnbuckles) of earlier S7's .

I do Not have a drawing ,... or , I believe have I even seen a photo , of the " thin steel girders , bolted to the upper edges of the ( Walnut) bearers" ........OR the "wooded cleats bolted to the front & rear surface of the bearers" .....Therefor , without these , I can make only a guess about these details .

However , I believe I DO have all of the S7 factory drawings of the parts that you describe as "..Additional horizontal (wood) runners between the first & second fuselage spars " and the ..." Additional two panar cross bracing between the runners mentioned above and the lower part of the fuselage truss " .
I also have some drawings showing the Heavy Mann Edgerton Steel motor mount with motor bearer , but I am not "certain" if this include the drawing of the.." oblique steel rods ( tubes) " , ...( From memory ,I believe it does ).
I think this oblique tube is ME method , in place of the above mentioned wire cross bracing etc. as used on later French Spad 7's .

I have some photos of the wing , plywood covering , (upper & lower ), between Leading edge & Front Spar ,( with lightning holes) ...however , all the photos I have are all of British ME manufactured machines ,which never were used operationally ...I have not any French drawing or photo , I believe , that show this for the French made "7" ....(I know it is used for the later Spad 13 ).

Personally , I prefer the Standard Rib , used with Riblet between each main rib , from Leading edge to Front Spar , as used , I believe ,... on C.N or G.Guynemer and other French / Italien ace machines .

Regard to the fabric , I did read somewhere about the described " bandaging" of ribs with linen & the fabric sew to this approx. every (?appx.?) third rib ....However I need to look at more photo's of Befor-restorations machines , to investigate if I have this detail , or not .

After 1917 , with British influence,...the 30mm rib tapes & sewing etc.......:- Is this the same method as the Standard British method & was it used for Every Rib? I wonder .

I like the "Yellow" look , although I know this was replaced by the 4 Aluminised colour (deMarcy) or with added 5 th Black , camouflage , which did give longer fabric life .

Regards ,...John M