Sopwith Baby Project

[Nick]

The Snipe Spars are routed except for both the top wing inner bays are left solid.
The Riblets are a metal pressed fitting (Dural I think) on both wings (top camber only).



This is the lower wing.

Cheers, Nick

[Joe Perkel]

Originally Posted by drrivah

Joe:
My archivist just back with results below:

Pup: Source-Original Plans
Spars routed, all four
Riblets Top Camber only, both planes

Camel: Source-Tallman Camel (original airframe)
Spars not routed (top fwd, aft; bottom fwd-aft not visible in photo)
Riblets Top Camber Only, Lower Plane Only


Note Camel full nosewebs (upper) with small lightening hole, and unrouted spars compared with Pup less massing webs and spar routing. OK Nick, so,
what about the original Snipe LEs and spars?

-pete

Pete,

Thank you for those references. What escapes me, is why did they make this mistake on the SDASM Pup? That threw me off the trail a bit.

In reviewing my drawings, I now see a previously missed notation regarding fairlead routing on the bottom wings which I need to look at more closely.

Thanks again!

[RobW]

Joe,
I'm following your thread with a lot more interest... well, I've always been interested... but now I have more focus.

As it turns out... Salmson built Sopwith 1 1/2 Strutters before building the Salmson 2A-2... and there are a lot of components between the two aircraft that seem to be very similar. The wings especially seem to have a lot of Sopwith influence.

As I've been going through and translating the rigging notes I've come across something that translates as "Hip Rafters"... and I think they are referring to the angle braces in the wing... see the picture below...

So, what are these angle braces called? What would be a good translation for Hip Rafters?

[Joe Perkel]

Originally Posted by RobW

So, what are these angle braces called? What would be a good translation for Hip Rafters?

Rob,

I've not yet finished the authorized biography on Tom Sopwith "Pure Luck" but, yes... I think I recall Salmson mentioned as one of the contract companies. Either in that book or in the Mick Davis text Sopwith Aircraft.

These "Hip Rafters" are apparently a term borrowed from architecture, and describe the corner 45 deg rafter of a roof line....



In my wing plan view, Sopwith refers to these simply as "1/2" Spruce Stiffeners." The purpose is to keep the wingtip bow supported against the shrink tension of the doped fabric.

I want to see you do this two seater. As time is passing here, and I am learning more design details, I find myself rapidly coming to a likely conclusion of building the Baby or (Schneider if I use a flat opposed) as a single. Aside from the practicalities of power and weight issues, it would seem I've been infected with a particularly nasty strain of authenticity disease!

I do so want to get started but, my house contractor (and his subs) of course,..have taken the month of December off! Do you think if I strangle the guy that they would allow me to build a plane in the prison wood shop??

[RobW]

Thanks Joe,
Those stiffeners are located throughout the wing... are they called the same thing throughout?

Rob

[Joe Perkel]

Originally Posted by RobW

Thanks Joe,
Those stiffeners are located throughout the wing... are they called the same thing throughout?

Rob

Rob,

This may be something different then. Perhaps another construction method using a truss arrangement of some sort. I can't speak this but, the Pup diagram, was as I described.

[RobW]

Maybe "throughout the wing" is an exaggeration... but they are in several places througout the wing...

For instance... here on one of your Baby shots... are another pair...

and I suspect there are some at the wing root...

does this make more sense?

rob

[Joe Perkel]

Originally Posted by RobW

Maybe "throughout the wing" is an exaggeration... but they are in several places througout the wing...

For instance... here on one of your Baby shots... are another pair...

and I suspect there are some at the wing root...

does this make more sense?

rob

Rob,

These are also noted as (1/2" spruce stiffeners) on my drawings. Yes, I also have them at the root. I think early on it was ULpilot who educated me on the function after my own inquiry.

When you follow the load path, it's fairly easy to see which member is the one intended to be supported and at what points. When you mentally apply a lateral load (such as fabric shrink), then it makes more sense.

[Joe Perkel]

Schneider Cup racer photo and it shows the SPAD S.20 as entered in the 1919 race at Bournemouth. Pilot was Sadie Lecointe but it never started during this year and the next year it was already outdated! The plane was fitted with a 260 hp Hispano-Suiza 42 engine.

Slightly off topic but, of enough interest to share a surprising find today while further researching the Schneider Cup races. No mistaking the family lineage in the rudder shape, stagger, and cowl.

[Joe Perkel]

Getting back to CAD work recently, I am revisiting an earlier issue with the spar boxes. Some may recall, that I was missing original details and I used the Pup drawings on my website as a stop gap until I acquired the new drawings.

Of course, Sopwith did things distinctly different on the Baby as opposed to the later Pup knowing full well that 94 years later they would give me a headache! (Ok a stretch there).

For one thing, the center section spar drawing plainly notes that the dihedral is to be set at 2.5 degrees on the short center section spar which is "cut to suit." This is in contrast to the Pup, where the dihedral is set at 2.5 deg on the main spar which is also "cut to suit."

So, in the images below, I can now show you the spar box assembly drawing, and my interpretation, of how it should fit, in order to obtain this dihedral. ( You may have to fully expand the drawing in the lower right corner in order to see my notations).

Question of the day then is, did I interpret this correctly?

Note also, what is to be done with the drift strut socket in order to maintain alignment. In this case, I left it fixed in space, while rotating the part underneath to get the 2.5 deg.