SE5a - another approach

LINNEY · 16-10-2007

I was not too happy about starting another SE5a thread because Graham (Greyhead) is doing such a fine job but he and others said a different viewpoint would be welcome - so....
Actually, I was encouraged because apparently Graham and I come from two different directions. Clearly, he is a craftsman and a very committed one whilst I certainly am not, I am more of a technician and our differences in approach might, just might, be of interest. It is doubtful if there is a simple right-or-wrong, just differences to which there will be different reactions.

Firstly, what is "scratch build"? Some appear to think it is making a model from a kit as distinct from putting the finishing touches to an ARTF. Others say it is starting from a plain piece of paper, drawing up your own plans, buying all materials and getting on with it. I think slightly differently because this aircraft was "scratch built" by the Royal Aircraft Factory from plans supplied by the designer, H.P.Folland, in 1916 so my first job was to find plans. I settled on the 71" span John Simmance plans bought from the U.S. MODEL AIRPLANE NEWS and was provided with 6 sheets each about 5' x 3' !
Actually, 3 of these massive sheets give very excellent full-size plan and, where necessary, elevation details of all the wood and metal work required - and I discovered that there were to be nearly 400 wooden parts from over 120 different designs! Well, if I could look ahead five years I might manage, but even then not to the quality standard required so I went to Leon Cole of Belair Digital and asked if he could laser-cut them for me. No problem, and he has one big advantage, he can cut thick ply so there would be no need for laminating the most substantial parts. The metal parts I am prepared to take on.

The next thing was to study the plans - for very many hours, they are very complex - and work out a production sequence. There are of course no construction details, you work it out for yourself, and I would hate to find that I have built up a section but then need to get back inside it. Actually I always dry assemble everything, with Sellotape, until construction is well under way.

Then the next problem - no point in starting to build unless you know what engine you plan to fit because the engine housing will need to be modified according to that decision. O.K. so what engine? Well, as I have said elsewhere, what prop? Possibly 18lbs of aircraft (I tend to build overweight to benefit strength) with lots of drag - biplane with struts, fixed undercarriage, etc. And what air speed must be achieved to permit healthy take-off? No help from anyone, I cannot find anyone who works from the prop requirements backwards - which to me I am afraid is the only logical way to go. The best I could get was "use a 120 4-stroke and whatever prop goes with that". O.K., then the RCV 120SP seems possible, it apparently has the power to pull that weight and overcome that drag given a 20" prop and the big advantage is that being a radially-mounted "rotating cylinder" engine it fits totally in-cowl. But it rotates at half "normal" revs and has a recommended maximum of 5,000rpm. Now, RCV suggest a 12" pitch which at max. revs would give about 55 mph theoretically. I have no idea what it might be in practice or if that is adequate - does anyone please? The other point is that a 20" prop would have about 2" ground clearance in level flight and since this aircraft is said to have a tendency to tip on its nose (plenty of WW1 photos to prove it) it might be better to use, say, a 15x12 4-bladed prop. Such props were common in actual service. Any views please?

The next approach was to the actual plans. Firstly they are too massive for casual "whilst-working" reference so I had the local photo shop produce quarter-size reproductions for me and I can keep these by the work bench. The next, very common, situation is that the plans show the port side of the fuselage elevation and the port wings plan view and so of course it is necessary to make "mirror images". So I had the same photo shop print out the construction plans 1:1 on transparent material so that when building starboard I only have to turn the plans over. Easy. And of course I cover them with a self-adhesive clear film to which cyano and epoxy do not adhere.

And, for now, the final consideration - and some views would be appreciated. When making a scale model is one expected to reproduce an active service model, complete with wrinkled covering, distorted spars, patches, rust, oil, dirt etc or should one, as I believe, attempt to produce the designer's dream? I asked the Shuttleworth chaps and their view was certainly as mine. They considered that if you reproduce all the blemishes it will be considered to be just an excuse for poor workmanship. So I propose to try to build what Folland had in mind in 1916 and any blemishes will be my failings and not deliberate. But that is a long time into the future.

I wil add to this from time-to-time as matters progress but for now I await, in hope, for some helpful reactions please!

**wonwinglo** · 16-10-2007

Linney,I look forward to reading more of your approach to this subject,as individual modellers we are all unique in our approach to a subject,once more we can all learn something along the way,thank you for taking the time to relate here your experiences in building your S.E.5A.
Incidently you are building from a very cherished master modellers plan,John Simmance was and still is a very respected scale model builder.

Greyhead · 17-10-2007

It will be very interesting to see if your technical approach comes up with the same answers as what we might call the “intuitive approach” used by most modellers.

The problem I can see with the technical approach is that, as you’ve discovered, there is very little data available. If you manage to correlate the data, weight, lift, drag, speed required, engine size, prop size, etc. etc. I’m sure there would be a ready market for the information.

The problem with the intuitive approach is that it can be slow to catch up with improvement in engine design, new materials etc.

However your SE5a is eventually built, I expect in reality it will end up using a combination of technical and intuitive, I’m sure it will make a very useful and informative thread. I’ll watch with interest!

LINNEY · 21-11-2007

I am now getting down to things – but I had to do a lot of investigation first.
To be absolutely clear, using John Simmance plans I am building a Royal Aircraft Factory Scout Experiment No.5, version A (known as the RAF SE5A) designed and built at their Farnborough factory - which later became the Royal Aircraft Establishment (RAE) Farnborough (just down the road from me). The RAE became the world’s most respected aeronautical facility covering everything from aircraft research, design, performance, capability, strength and durability and very importantly the scientific investigation of failures. RAE also covered the same qualities in pilots (except for design!). When I used to visit there on certain projects many years ago the laboratories were still in the original wooden huts. Today the site is blocks of flats within a commercial building site, no more RAE and no longer is Britain a World Leader in Aeronautics thanks to today’s politicians.

During WW1 aircraft were initially intended for “scouting”, locating and reporting back on enemy positions and strengths, and there were no such things as fighters or bombers. The early aircraft, which were generally two-seater for pilot and observer, had no armament except for possibly pistols held by the crew. An uncle of mine spent a fair length of time hanging over the side of such an aircraft with a wooden “bellows” camera and glass plates which he took back to base, developed and printed for the Army. Opposition came mainly from rifle fire - Ack-Ack came later - and because the aircraft had to fly low there were losses. Later aircraft were of course fitted with armaments and even small bombs. At first these were just hand grenades dropped over the side to discourage riflemen..

The Scout SE5A was also built at other factories such as Vickers and so there were various other modifications made both at factory and even at squadron level but they were not given version suffixes so it is not possible to build “an SE5A”, you have to decide which you want.

The variations were many, for example Hispano Suiza or Wolseley Viper engines varying from 150 to 200h.p., full or narrow-chord elevators, metal tube or wooden (strengthened or not) undercarriage, one or two machine guns, “glasshouse” cockpit cover or simple small windscreen, headrest or open space behind the head and even different colours (more on that). And later a few even had radios.

So I had to decide which, and thus whose, aircraft I wanted to build and I decided on one of the Royal Flying Corps top aces (the Royal Air Force did not exist of course until after WW1), specifically Capt.Anthony Beauchamp-Proctor,V.C., D.S.O, D.F.C of 84 Sqdn R.F.C, a South African of such small stature that he had to have his seat especially raised but who managed 54 aerial successes. A success was an enemy aircraft or an observation balloon downed, the latter considered the more dangerous. You fired from up close and if the balloon exploded it could take you too.

So I wanted details of B-P’s aircraft and discovered that the South African Museum near Pretoria had a restoration! Faintly aggravated because I spend quite a reasonable amount of time in SA, must have been close to the museum on several occasions, and knew nothing of its existence! Still, February next hopefully. Meanwhile I wrote to the Museum and had a great response with photos etc and discovered that B-P had Lewis and Vickers guns, tubular undercarriage, no “glasshouse” but a headrest and the Viper 200h.p. engine. They don’t know about radio – yet.

LINNEY · 21-11-2007

Meanwhile I have visited the Shuttleworth lot at Old Warden. Give an extra contribution to the funds and you can go “back-stage” and talk to the workshop guys doing the work and photograph it all. Fascinating. No wings on yet but hopefully before the end of this month. I learned a lot, saw a lot. To me, most importantly, they are restoring to design level not operational aircraft level so it will be without battle damage or “hangar rash”, no attendant rust, holes, poor maintenance and (frequently) poor craftsmanship such as out-of-line stringers, sloppy covering, messy painting etc. That is what I intend, build what it should be not what it became. Well, that is what I hope. Am I good enough?

But I have problems. For example Greybeard talks of 5degree dihedral but others say as little as 3degrees. The Simmance plans have no front elevation and no mention of the dihedral but the wings are attached to the centre section by tubes in both parts mounted on to a rod to hold them together. There are holes in the first 3 ribs of all wings and centre sections to set the positioning of the tubes so by measuring the downward deviation of the holes and applying a bit of trigonometry I calculated Simmance drawings as 5degree. Actually I always measure by wing tip distance above the horizontal, calculating (more trigonometry) from the quoted angle.

I have obtained drawings of front elevation of full-size designs and by similar calculations they all show 5degree. I shall ask Pretoria and Shuttleworth because Simmance plans have a cock-up. Yes, hole positions giving 5degree – but the ones on the wing do not align with the holes on the centre section! In spite of spending hours studying the drawings I did not spot this until I had built both a centre section and a wing.

And again, wing (and stabiliser) angle of incidence. Always quoted as a deviation from the thrust line – but where is that? Some say (sensibly I think) the line of the prop shaft, the majority say prop centre to stabiliser leading edge and others (including Simmance) say prop centre to stabiliser/elevator trailing edge – well, this stabiliser has variable incidence so that makes sense. But was this true in 1916? Well, Shuttleworth guys say that the thrust line on virtually all WW1 aircraft is the line of the top longeron. The Simmance definition works out to be exactly parallel with that longeron line so I have no problems – except that reproductions of full-size drawings show different positions depending upon whether the aircraft is fitted with Hispano Suiza or Viper engine! Actually the Viper engine line, which is to be my version, creates a line which is parallel with the upper longeron so there really is no problem.

But there is still a question. Apparently the angle could be varied by the pilot in flight, accounting for the fabric crinkles seen on many actual WW1 photos. Apparently the pilot could lift the wing T/E which reduced the angle of incidence and caused the fuselage fabric crinkle in that area. But most “wrinkly” photos were taken on the ground indicating that the pilot set up less incidence for landing. Did he? If so, why?

LINNEY · 21-11-2007

And another rigging problem for me. I have seen rigging wires with names, those from, say, the rear of the top centre section to the lower wing tip leading edge (and front upper to wing rear) called “landing wires” whilst those from the lower centre section to the tips of the upper wing called “flying wires”. Again, some photos seem to show a single wire at each point but others show double wires as if they go up, around a pulley and back. Seems sense for setting up but why the names? What does it all mean? Surely these wires were set up by (often ex-navy) riggers before flight and in accordance with drawings but the names seem to imply that the pilot set them according to whether he was landing or flying. I am sure someone out there can put me right.

There is a lot more from my research, colour, covering, finishing and even what I shall buy as distinct from Greybeard who seems able to make anything!
But this is enough for now, a few more queries then on to actual building next time. But are you asking what all this has to do with scale building as a hobby? Well, it has a lot to do with it for me and that is really what it is all about – a different approach. If no one wants to read what I have written then doubtless I shall shortly be thrown off the site!

Greyhead · 21-11-2007

Welcome to the world of WW1 scale modelling! As you have already discovered nothing ever seems to be “black and white”, the more research you do the more different answers you get and in the end it’s up to you to decide what is best for your particular model. I appreciate that with your technical approach this really goes against the grain but unfortunately the information just isn’t reliable enough to get definite answers.

One “up side” is that no one can say with certainty that you’ve done something wrong!

One tip I would give is that when working from plans never assume that they are correct! As the original model develops things have a habit of changing and the plans don’t always keep up.

Greyhead · 21-11-2007

Just realaised I hadn't mentioned the wires!

Flying wires and landing wires refer to the loads that they transfer from the wings to the fuselage.

The wings are not strong enough, mainly because of the thin section, to take the lift that they generate so the top wings have wires joining them to the fuselage; these are the called the flying wires because they handle the loads whist flying. The load from the bottom wings is transferred to the top wings by the interplane struts.

When landing, as the wheels hit the ground the wings try to continue earthwards because of momentum. The landing wires join the bottom wings to the fuselage via the cabane struts to stop this happening and the load from the top wings is transferred to the bottom wings once again by the interplane struts.

On the SE5a the flying wires a double, that is two single wires not one wire around a pulley (16 wires in total).

It’s a bit cumbersome to explain but I hope you can understand what I mean!

**Bunkerbarge** · 21-11-2007

A very interesting read Linney and I'm sure a thread that is destined to become as interesting as Greyheads. It will certainly be interesting to see how the slightly differrent approaches relate to the finished article but I am sure that we are in for another treat of a build thread.

Greyheads build still continues to amaze me with the depth of detail and adherence to relevent materials for his components as well as his appreciation of how far to take the weathering aspects.

All fantastic stuff and I think we are very lucky to have builders of such quality who give thier time to post such amazing threads for us to enjoy.

alan2525 · 21-11-2007

One of the most enjoyable aspects of Greyheads SE5a thread is that the model is pure modelling at it's best. Some of the approaches to the various tasks such as the little tiny metalworking jobs from litho plate, the little jigs and press moulded detail parts, tiny details made from wire and the cockpit details etc and the way every little detail is tackled as a little model in it's own right.

Greyheads common sense, experience and skill along with his explanations which are so insightful it makes the tasks which seem impossible to start with, seem almost (for want of a better word) straightforward!