Sopwith Baby Project

Machinbird · 1 February 2008, 09:07 AM

Joe,
Just a guess, but an oblong section would give a thinner trailing edge than a round tube and with the major dimension of the section oriented fore and aft, would provide more strength against the tendency of the shrinking fabric to collapse the trailing edge forward.
Sid

ulpilot · 1 February 2008, 09:22 AM

Quote:

Originally Posted by Joe Perkel

I have a question regarding trailing edge tubing.

The drawings I have many times need to be interpreted with a magnifying glass. As I am now working on the wing details, I've noted something curious on the drawings.

There is a reference to a "section AP" for the trailing edge and a handrawn figure but, no dimension detail other than 22 g. It is a strange looking oblong affair.

I was under the impression that most fabric biplane trailing edges were circular in section about 1/2" diameter. Something like this skybolt....

So my question is, why an oblong section -vs- a circular one? Anyone have any ideas?

Thanks

Joe,
I think your mistaken on the use of tubing for trailing edge on the Skybolt. I believe it uses this material:

TRAILING EDGE from Aircraft Spruce

This gives you more gluing area for fabric covering.

In fact most fabric light planes use something like that. Exception is the ultralights and scaled WWI replicas that are built of aluminum tube.

Dogtail2 · 1 February 2008, 10:10 AM

Upilot is correct. This is exactly the material on my Pitts trailing edge.

Joe Perkel · 1 February 2008, 10:22 AM

Aha,..you see it pays to ask! I was for the moment going to give up on section AP and draw a circular section as a short-cut,...(no no no!)

That hand-drawn figure on my drawings looks very much like that material at Spruce. I will re-work this now properly!

Thanks, Sid, Vet, & Pete!

Leatherhead · 1 February 2008, 10:59 AM

Joe,

The "section AP" may be refering to Accles & Pollock steel tubing. I have seen this reference on my Bristol M.1C drawings. A&P still exist, but they don't make the streamline steel tubing anymore, at least not in the size they did back in 1916.

Since your Sopwith and my Bristol are both British aircraft, I'm thinking A&P must have been a supplier of steel tubing (streamline, or otherwise) to British aircraft manufacturers at the time.

On the Bristol drawings I have, Accles & Pollock is written, so it is clearly defined; however, the size is just given as "Section 186 x 16 SWG". Actually, the full text on the drawing is:

"Accles & Pollocks Section No. 186 x 16 SWG"

I'm assuming there must have been a table that one could look up the section number.

I hope this helps.

Leatherhead · 1 February 2008, 11:05 AM

Joe,

After my last post, I started thinking. I pulled out some of my Camel and Snipe drawings to see what they had for tubing. Yep, you guessed it. A&P tubing. So, if the Camel, Snipe, Bristol, and Baby all had references to A&P, I think my previous post has some validity.

What is the A&P section for the Baby? It's shown as Section No. 121 on the Camel.

William · 1 February 2008, 11:14 AM

Joe,
That would most likely be Accles&Pollock 121 for trailing edge. Sopwith must have had a job lot of the stuff as it was common to all the original drawings that I have and frequently was used for the rudder and elev. also. A&P still exist but sold their tooling to a company in Canada which refuses to make more. About ten years ago we were at Brunton's in Scotland and gave them feedback about 121 for a run they were trying to make on their ancient flying wire rollers. It was close but not quite perfect; but, you might want to see if they continued. If you need dims email me and I'll look up the csect this weekend. It would be tedious but could be rolled/drawn. Similar to the rollers Achim made for streamlined tubing.
Best regards,
William
Website still down but will return as soon as have recovered data

Joe Perkel · 1 February 2008, 12:10 PM

Quote:

That would most likely be Accles&Pollock 121 for trailing edge

Bingo,..that's it! Accles & Pollock section 121. I am not at home at the moment but yes, I remember the 121 reference now. I had thought perhaps the 121 referenced a drawing I did not have or part number. Interesting, how the edge material at Spruce bears the resemblence.

Quote:

After my last post, I started thinking. I pulled out some of my Camel and Snipe drawings to see what they had for tubing. Yep, you guessed it. A&P tubing. So, if the Camel, Snipe, Bristol, and Baby all had references to A&P, I think my previous post has some validity.

Very,very helpful,..thanks! I'm also now reminded that I do have replicraft drawings for the Strutter and the Pup, so time to break those out tonight when I get home as this will no doubt be there and clear!

So if this company (or anyone else) no longer provides this, then I need to consider drawing up what's commercially available in terms of CAD detail.

Thanks William & LeatherHead!

drrivah · 2 February 2008, 06:09 AM

Hi Joe:
I looked into having a custom outfit (Retrotech Ltd./East Sussex UK) roll some A & P 121/ 22G trailing edge as well as the streamline for LG (A & P 210/18G) and vertical tailpost on a Pup (A & P 5/ 20G). Quotes were UKL50/ hr with about 1.5 hrs to roll one 9 ft length. Plus shipping long lengths from the UK. They do not magnaflux the nonstructural streamline, but tests for components like landing gear streamline would probably be appropriate.

Does anyone on site have the spec/dimensions chart for A & P sections-please post. On plans sets (originals) there are approximate dimensions and in period construction/repair books an indication of which diameter round stock to begin with, but I haven't seen the "official" A & P dimensions of starting round stock or final major/minor axes.

If there is someone out there interested in making the dies and running some lots, contact me offline. Might be a supply item several builders could support.

-pete/Leesburg/Va

Joe Perkel · 2 February 2008, 06:30 AM

Quote:

Originally Posted by drrivah

Hi Joe:
I looked into having a custom outfit (Retrotech Ltd./East Sussex UK) roll some A & P 121/ 22G trailing edge as well as the streamline for LG (A & P 210/18G) and vertical tailpost on a Pup (A & P 5/ 20G). Quotes were UKL50/ hr with about 1.5 hrs to roll one 9 ft length. Plus shipping long lengths from the UK. They do not magnaflux the nonstructural streamline, but tests for components like landing gear streamline would probably be appropriate.

Does anyone on site have the spec/dimensions chart for A & P sections-please post. On plans sets (originals) there are approximate dimensions and in period construction/repair books an indication of which diameter round stock to begin with, but I haven't seen the "official" A & P dimensions of starting round stock or final major/minor axes.

If there is someone out there interested in making the dies and running some lots, contact me offline. Might be a supply item several builders could support.

-pete/Leesburg/Va

Pete,

After yesterday's responses I did go home and also confirmed what you just said reference the "Pup" drawings. I suspect the Strutter is the same. Interesting little dilemma here,... What to do now?

That material posted by Vet from Spruce Aircraft Supply is a likely substitute. At the moment, I don't quite understand the installation with respect to fitting at the ribs, and I need to contact Spruce to find out the radius at the end there,... 1/8" or is it 3/16" or what?

Also, how does one radius this stuff as indicated in the plan views?

I will keep your UK contact in a file,....Thanks Pete!