Sopwith Baby Project

[Brad]

Originally Posted by Joe Perkel

Hi Brad,

I need a frame for 1,250 lbs empty, 1,750 gross. Anything you can think of close to this I can use as a guide?

My "military load" will be taken up by a passenger. The Norwegian two place Baby removed the aft reserve tank and placed a bench seat, I would likely use a reserve tank only while dual. The plane would no doubt do most of it's flying solo. But once built, it would fly quite a bit.

A problem that I am dealing with at the moment, is that the rugged simplicity of steel tube seems to be nagging at me again.

In looking at Storo's Brisfit, I see it really did not rob much from the authenticity of the machine, it is in fact a flying / working version, obviously Jackson liked it enough!

The discussions are helpful Brad, precious little time at the moment to hit the books hard. I can pop in and out of here and think about what you all have to say as I go through the day.

Thanks!

Yeah, several come to mind. Stolp Starduster II, Acro Sport II... they are lighter, but stressed for full acro. Piper Pacer/Tri Pacer. Pitts S1. (ALL of those are welded steel fuselages) If you aren't planning an aerobatic bird that can handle 9 g's, then the loading isn't as high, so something designed for say 1200# at 9 g's would be fine at 1750# at 5 g's or somewhat more. Most fuselages are overbuilt anyway... Graham Lee's tiny aluminum tube birds are WAY over the required strength in the fuselage. Of course "incident" safety is also a consideration... you want a structure that protects the organic parts of the payload in the event of a, ahem, "hard landing."

Since you have the Beaujon book, use the info in there to help you decide. It has information on strength of various tubing, how load paths are transmitted through structures, etc.

To the "uninitiated" (like me) engineering of structures looks like voodoo. How loads transmit though the structure makes sense, but it is hard to believe the numbers sometimes. It is shocking how light and spindly a structure can be, and still be AMAZINGLY strong if designed properly.

Brad

[Joe Perkel]

Originally Posted by Brad

Yeah, several come to mind. Stolp Starduster II, Acro Sport II... they are lighter, but stressed for full acro. Piper Pacer/Tri Pacer. Pitts S1. (ALL of those are welded steel fuselages)

Brad

Off course and I know these!,... a mental lapse here for a moment!

I am super distracted at the moment by a major home build. Once out of the way, I'm going to start the ribs late this year.

Grahams designs rekindled my lost interest in aviation early in this decade. He preached "simplicity" to me,...Geez I've lost the faith!

Thanks Brad, will refer again to this shortly.

[Joe Perkel]

I never cease to be amazed at the sheer variety and complexity of hobbyists worldwide.

Discovered tonight the genealogy of the Rotec Radial in a 1930's hobby design called the Hodgson 9 Radial.

Model Engines at Old Warden, 2001

May be old news but a surprise to me!

Note well also the various other rather WWI(ish) looking designs such as the Kinner Radial and Bently BR2 Rotary.

These guys are no doubt premier hobbyist machinists.

[drrivah]

Joe:
For any noice at machining or metalwork in general, both the Lee Hodgson and Blackmore books are great. They describe in detail how a scaled-down fully operational (Bentley) rotary (and prop) is machined, fitted, assembled and run-in, and are well worthwhile.

Hodgson is especially good on materials and current sources of scale pre-fabricated bearings, for example. However, a little familiarity with machine shop, lathe-work and milling would help if these sorts of projects are anticipated. Blackmore has fewer shop blueprints, but more photos of the milling set up for detailed parts. Makes you want to drop what you're doing and get into machine shop. On second thought however, it is a bit more complex than that.

Nahum's history on rotaries is "the" book, but for people online who like to get into what "real" materials and methods were used, probably have to go to original blueprints, and hope the xeroxes haven't cut off the material spec block.

There was quite a bit of fuss on another thread about engine metallurgy, especially rotaries. Thing is, most of the disputants were right to a greater or lesser degree. Gnome rotaries used a lot of nickel steel. Others (LeRhone) used mild steel, cast iron for some parts and forgings. The Union Switch and Signal (US licensee) LeRhone 9C was "upgraded" in the US version and some parts use different materials from French LeRhones. Some rotaries had steel cylinders with liners. The Bentley used aluminum pistons, which were quite a novelty at the time and a big improvement over the Clerget engines that Bentley worked to improve.

So, generalizations about (rotary) engine materials are difficult as engine technology was changing very fast. Each type has its own peculiarities.
In fact, as Nahum points out, rotaries really had only a 10-year run from the Paris Arshow in 1908 until 1918 when the last and best rotary was introduced.

Finally, there is a company that sells (or sold?) scaled down "historic" engines, including a Gnome, an OX5 and others (Oppenhauser), not as kits but as "runners". I think the name was "Warner" but I'd have to dig out the actual contact info. They may not have a web site.

Maybe someone online here has built one of the scale rotaties from scratch.
Would be great to hear from them.

Harry's Bentley, describes a model project that morphed into a full scale, fully aeronautically viable Bentley (1:1). Harry has designed a geared oil pump that is better than the LeRhone oscillating plunger on the original. For any who think about making a full-scale rotary from scratch, study Harry's Bentley: warning-don't try this at home, folks.

-pete

[Joe Perkel]

Pete,

Thank you for those valuable references and your take on them.

I am amazed at what machinists can do with a casting! Likely never to get to such a level but I will give the guns a try and some fittings here and there. I do like to learn stuff though, and I will take a closer look at the items you mentioned.

I do see the appeal of these little motors!,..these and the steam driven ones seem to be perfect home machine-shop fodder!

Thanks again!

[ECramer]

Originally Posted by drrivah

Joe:
For any noice at machining or metalwork in general, both the Lee Hodgson and Blackmore books are great. They describe in detail how a scaled-down fully operational (Bentley) rotary (and prop) is machined, fitted, assembled and run-in, and are well worthwhile.

Hodgson is especially good on materials and current sources of scale pre-fabricated bearings, for example. However, a little familiarity with machine shop, lathe-work and milling would help if these sorts of projects are anticipated. Blackmore has fewer shop blueprints, but more photos of the milling set up for detailed parts. Makes you want to drop what you're doing and get into machine shop. On second thought however, it is a bit more complex than that.

Nahum's history on rotaries is "the" book, but for people online who like to get into what "real" materials and methods were used, probably have to go to original blueprints, and hope the xeroxes haven't cut off the material spec block.

There was quite a bit of fuss on another thread about engine metallurgy, especially rotaries. Thing is, most of the disputants were right to a greater or lesser degree. Gnome rotaries used a lot of nickel steel. Others (LeRhone) used mild steel, cast iron for some parts and forgings. The Union Switch and Signal (US licensee) LeRhone 9C was "upgraded" in the US version and some parts use different materials from French LeRhones. Some rotaries had steel cylinders with liners. The Bentley used aluminum pistons, which were quite a novelty at the time and a big improvement over the Clerget engines that Bentley worked to improve.

So, generalizations about (rotary) engine materials are difficult as engine technology was changing very fast. Each type has its own peculiarities.
In fact, as Nahum points out, rotaries really had only a 10-year run from the Paris Arshow in 1908 until 1918 when the last and best rotary was introduced.

Finally, there is a company that sells (or sold?) scaled down "historic" engines, including a Gnome, an OX5 and others (Oppenhauser), not as kits but as "runners". I think the name was "Warner" but I'd have to dig out the actual contact info. They may not have a web site.

Maybe someone online here has built one of the scale rotaties from scratch.
Would be great to hear from them.

Harry's Bentley, describes a model project that morphed into a full scale, fully aeronautically viable Bentley (1:1). Harry has designed a geared oil pump that is better than the LeRhone oscillating plunger on the original. For any who think about making a full-scale rotary from scratch, study Harry's Bentley: warning-don't try this at home, folks.

-pete

The company that builds miniature Gnome engines is called "Replica Engines, Inc." and can be found here: Home

In the past they offered a Harley knucklehead engine, an Offenhouser, a Flathead Ford V-8, and an OX-5. Currently the Web site lists only the Gnome and the Oldsmobile Aurora engine. These aren't toys, and are quite pricey, with the Gnome costing just less than $4,000, plus another $2,000 if you want the running stand for the engine. I guess four 1/4 scale Gnomes would power a full size project, but the prop arrangement would be a little strange <grin>.

[Joe Perkel]

Gentlemen,

My wife and I have recently been having a friendly "discussion" regarding finish options for the project

I've posted a poll for the two finalists and would appreciate opinions. Here are the two candidates.



Serial No# 8165 has the advantage of "Name Recognition on the vertical stabilizer.



Serial No# 2071 Blackburn built, has an interesting mix of colors and armament but, lacks the "Sopwith" Brand name as it were.

What do you think?

[Joe Perkel]

Gentlemen,

As recommended by several experienced builders, I have been acquiring plan-sets for comparison purposes.

My take on the following two aircraft as a result. Any follow up input is as always welcome and appreciated.

Redfern Nieuport.

Super nice plane! I like the steel tube and wire braced fuselage enough to re-consider again departure from the original. If I go that route, I will change the floats to a more modern compartmentalized version with lightened ply vertical webs with bulkheads in lieu of transverse rib structure while maintaining external dimensions.

Goal here would be simple,...durability!

Redfern DH-2

Not really a plan-set but a collection of seven G.A. drawings and one airfoil drawing (the RAF 15).

Interesting aircraft,...clearing turns you say?...who needs them! Must be a spectacular view and what looks like would be a pretty snappy little roll response. Also looks like a real narrow speed range,..a fine line between flight and no flight!

I don't quite like what the gun could do to your face in an off airport situation and don't even want to think about wires!

Can't get the view out of my mind though, like I said,..an interesting little bird!

[brisfitworks]

Joe:

I am not sure I am reading which is dbl'd correctly, but if you mean the dbl strand is running from front spar at root, to rear spar at outboard end of bay, then this makes perfect sense with what I am about to describe.

It is all about force directions and lever arms.

Consider a wing panel stripped down to only a rear spar and the attached aileron. Deflect the aileron and it pulls back on the spar. Thus a bracing wire from an outboard station along spar running forward to the fuselage braces the entire wing against this and all other drag loads.

Other than general rigidity requirements, there are few forces as large as drag loads trying to push a wing forward (i.e. "anit-drag" loading. Yes, tail slides and nasty spins would be examples of such fwd aerodynamic loads).

Since drag loads are considerably higher, designers save weight by sectioning down anti-drag wires and other parts. Thus Anit-drag wires tend to be a gauge or two smaller especially in the bays closest to the fuselage.

Loads build up along a wing from tip to root. Again the simple lever, an aileron load has a small lever arm on the interplane strut (about 15" arm on Camel lower wing panel) but, on Camel again, a 10ft of lever arm from aileron to root attachment to fuse. This makes for almost 10 times larger a load. Thus wire gauges and all parts get stronger from tip to root.

Again on the Camel Lower wing, Drag (D) vs Anti-Drag (AD) bracing, in each bay,from tip to root is as follows:
D = 16ga Music wire / AD = 16ga Music wire
D = 12ga Music wire / AD = 14ga Music wire
D = 2BA RAF wire / AD = 12ga Music wire
D = 2BA RAF wire / AD = 12ga Music wire

I've seen a number of British designs with double wires as drag bracing on inner most bay. The reason for double wires has to do with the gauge of the wiring plate the bracing attaches to. Due to pull-out strength (the metal that keeps a clevis pin from tearing out the hole) it is sometimes decided to simply leave a plate the gauge required for the smaller load instead using a larger bracing wire which needs doubler plates, or brazed on washer and other annoyances.
(I think the Tigermoth wings hanging on the wall at our museum are an example of dbl wires, I am curious now and will take a look tonight when I go to trudge through the task of forming root spar boxes for our Camel wings AAARRG!)

Consider, the rear end of the first compression strut in a wing (the joint between a inner bay and next outoard at rear spar). When we design the wire lug at the base of the compression strut for the attachment of the two wires, we may have 4BA tierod on the outboard side of that strut and 2BA on the inner side. 2BA would likely lead us to choose 10BSWG plate but such a thick plate would not fit into the width of the 4BA fork-end. Use 12BSWG plate to fit the 4BA fork (1050 lbs rating) and the radius of the wire lug to keep the clevis pin from tearing out is too large for the depth of the 2BA fork-end (1900 lbs rating). So instead of frustrating over this (or more likley the engineer hates drawing up complicated wire lugs) you simply double up 4BA tie-rods in parallel on the inner bay for drag wires and make a simple, flat wiring lug with one hole outboard and dbl-holes inboard. Then, being British and not the guy machining the stamping die, you design a pretty outline to reduce all the unnessecary weight.

Sorry for the overly long treatis, just not sure how to describe this in few words.

Hope this is helpful,

Bill.

Originally Posted by Joe Perkel

Ah...OK, now I know what to look for as far as rigging is concerned.

I am unclear about something else. If in fact these wires (drag / anti-drag) perform both functions in this X configuration. Why then double the strands on the wires angling outboard (fore spar to aft) while leaving the others single?

Did Sopwith do this on the Snipe? I've noted that the PUP did not double the cables but, did go to 12g on those wires.

Thanks Nick!

Not looking to change anything, just trying to understand this wing design.

[Joe Perkel]

Originally Posted by brisfitworks

Joe:



...... The reason for double wires has to do with the gauge of the wiring plate the bracing attaches to. Due to pull-out strength (the metal that keeps a clevis pin from tearing out the hole) it is sometimes decided to simply leave a plate the gauge required for the smaller load instead using a larger bracing wire which needs doubler plates, or brazed on washer and other annoyances.



Hope this is helpful,

Bill.

Well then, another piece of the puzzle placed! This makes sense to me, very helpful Bill thank you!

Your simple visual explanation of a lever and drag forces associated with surface deflections, cued my memory on the subject from way back.

Most helpful because I now know where to look for further references.

Thanks again for taking the time for such a well thought out response!