SE5a CONSTRUCTION BEGINNING TO . . .

Greyhead · 08-02-2006

Introduction

EDIT:

Any “fact” about the original SE5a that appears anywhere in this thead should be read as if it had the caveat “ to the best of my knowledge from the research I have done.” added!

END OF EDIT

This thread is going to be a long-term project; if you have read my Parnall Elf construction thread you will know that I’m not a super fast builder, I took nearly 3 years to redesign and build that model, but in that case the model was completed before I started the thread!

With the decision made that my next scale model is to be an SE5a the search begins for a suitable plan; if someone has done all the hard work for you what’s the point in doing it all again and designing from scratch? I will use one of my trusty Laser 70s but was unable to find a suitable plan for this size engine so first some calculations from a simple 3-view drawing downloaded from the Internet.

The first thing to determine is the size; this may not be quite as simple as it seems, a flick through the plans hand book shows models of a similar design i.e. biplane with rigging wires, varying from 80” span for a 48 – 52 four stroke to 56” span for 80 – 90 two stroke (therefore at least a 90 four stroke). The method I use is to work out a minimum size that will allow the engine to be fully enclosed then go bigger to make it the correct size for commercially available accessories, usually wheels. My argument for this method is that you can never have too much power if you need it, but you can always use less throttle and a larger diameter prop to fly in a scale manner. In this instance it equates to 58” span for 5” Williams Bros. vintage wheels.

The next consideration is how scale? As I was going to have to redraw the plan anyway I chose the most accurate I could find, the plan was ordered and then reduced by Prontaprint. I intend to trace the outline then design my own internal construction as I hope to be modifying the plan to allow for some extra scale detail. Before any design work can start I need to confirm the viability of such modifications by making test parts / jigs etc.

Glider Guider · 08-02-2006

I look forward to seeing the development of the SE5a in 'real time' as it were, if it's as good as the Parnell Elf it should be a lovely model. Are you going to draw up plans this time, rather than the 'back of an envelope' technique and hopefully get them published in the modelling press?

Greyhead · 12-02-2006

David

I have to admit that I was surprised by the amount of interest shown in the Parnall Elf, which culminated in the publication of the article in Radio Model World, who did indeed ask if I had a plan for the model. Although it wasn’t quite a “back of envelope” project, as I said earlier, the model was completed before the thread was even thought of and I didn’t keep many of the smaller drawings. It would have been a major project in itself to redraw all of these, especially as quite a lot of the items “developed” as construction took place. I’ll make sure I keep everything this time and see how things turn out.

Grahame

**wonwinglo** · 12-02-2006

Grahame,thank you for taking the time to give us a unique insight into your new model as it is built,there is nothing quite like seeing the bare bones evolve of a complex model such as this,knowing your knowledge of model structures and the ability to make the many detailed fittings especially required on such a machine, then it should prove to be a most interesting project.
Many people do not realise how much work is involved in producing working drawings for the model press,many years ago I was involved in making one of two prototypes for a small racing aircraft,we made the mistake of preparing the plans later after the model was built,no easy task either,when it was offered to a UK magazine they altered it again to make it compatible with issue as a free plan ! I can now see how errors creep into some of these drawings and make life especially difficult for third party builders,I hear of so many complaints about drawings issued in recent years by magazines,the fact remains that far too many drawings are prepared after the event of building hence the errors,the American market demands that plans should be drawn of the actual prototype,then it must have been built and flown with photographic evidence to substantiate this,it makes sense really but still designs are marketed without being properly test flown and the quirks ironed out.
The S.E.5A is a classic subject deserving of special care,and I cannot think of a better person to reproduce this lovely World War 2 aeroplane than yourself Grahame,also a good stablemate for your Albatross D.V as well.
We all wish you well with this model and look forward to its continual development here,thank you.

Greyhead · 12-02-2006

One of the notable features on the SE5a is the transparent inspection windows for the aileron and elevator linkage. Here is a photo of the full size taken from a French site where they have restored an SE5a. Click HERE if you want to see all the restoration photos

These need to incorporated for scale authenticity so I want to make them “working” if at all practical.

The first problem is the pulleys; at the scale I’m building they need to be 9mm diameter, I’ve been unable to find any available commercially so turned some from circuit board. I’ll not include a photo; after all, if you’ve seen one pulley you’ve seen them all but if you’re interested you can use this link to a thread about them http://www.scale-models.co.uk/t2363-help.html

Next there are the control horns. These a quite thin and as such would be too weak cut from paxolin sheet, metal seems to be the only viable material. My first attempt uses wire as the “outline” in filled with balsa; this means that the holes don’t have sharp edges that would of course quite quickly cut into the control cables

The photo doesn’t give the correct impression of the shape of the horn, because of perspective it appears to be a lot less tapered than it really is. Although this method seems OK I’m not really happy with it, I’m going to try cutting the horn from sheet steel then use a yoke to attach the cable but just how to make a yoke at this scale I don’t know.

At least I’m now confident that I will be able to use the scale linkage so can start the modifications to the plan.

Greyhead · 11-03-2006

The redrawing of the plans is coming along slowly, the majority of the outlines are drawn and a lot of the construction detail for the lower wings completed. Before I commit anything to paper, let alone balsa, I build a “virtual” model in my head, at least for the more difficult parts. It doesn’t always work but usually several ideas are scrapped before the final plan is drawn.

I’ve decided, as I’m going to use scale aileron controls, that the most practical solution is to make the top and bottom wings “plug in” as an assembled unit. Still trying to get some suitable carbon fibre tubes to use as both spars and tubes for the piano wire wing pins.

To keep the interest going I’ve started some of the “engineering” jobs that can be done before the final construction details are worked out. I’d previously made the aileron control pulleys so I’ve started on the shackles.

Here are the components:

I’ve used 0.5mm steel for the shackle body and a small split pin for the “eye”. The pin is 1mm brass rod with a 14BA nut soldered to the end to simulate a bolt, when finally assembled I’ll crimp the other end of the pin to secure it as it won’t be visible.

The assembled shackle

With the body bent to shape and the split pin soldered into place I thick the finished shackle looks quite convincing. Remember that the picture above is about 5 times true size (depending upon your monitor), the pulley itself is only 9mm diameter.

**wonwinglo** · 11-03-2006

Nice detail Grahame,and the usual standard of excellence associated with all of your models,working things out slowly as you do is good practise,then things just come together nicely,thank you for taking the time to take these photographs and explain things,a compendium of knowledge on period biplanes.

Greyhead · 19-03-2006

“DON’T START TO BUILD UNTIL YOU KNOW HOW YOU’RE GOING TO FIX THE TAIL-WHEEL” is a quote from an article by a well known scale designer / builder in one of the model magazines I read quite some time ago.

Whilst I can see the logic I’m afraid that I’m not that patient, although my plans are nowhere near finished some sections are complete, namely the front of the fuselage, and I want something to hold that looks like a piece of an SE5a!!

It might seem a strange choice but I’ve started the construction with the undercarriage. The reason being that the fixing is slightly complicated to allow for the tensioning of the front flying wires so I decided it would be easier to make the fuselage fit the undercarriage rather than the other way round.

The main legs use 2 pieces of 12 SWG piano wire, these needed some careful bending as they are quite a complicated shape, the rear support uses 1 piece of 10swg.

Before I can silver solder the pieces together I must make a jig to hold everything in the correct alignment.

**wonwinglo** · 19-03-2006

Grahame,I think your approach is very practical,I always think that by getting the metalwork assemblies out of the way then you can start cutting timber in earnest for the airframe,you just have to break everything down as individual parts,by doing this maintains interest on what will be a long project,also it is much easier to fit metal parts to wood rather than the other way round,it looks like this is going to be one very nicely built S.E.5A in the end,great planning Grahame.

Greyhead · 19-03-2006

The undercarriage jig is simply a length of 3x1 timber with a centre line; various screws and panel pins are used to hold the separate pieces of piano wire in their correct positions.

Unless you are exceptionally talented at wire bending and / or very lucky the joins will need a bit of tweaking to get a good fit. When all is ready the joins are held with a twist of thin copper wire, if you don’t do this the unequal expansion as you apply the heat will almost certainly “spring” the joins.

The silver solder flux is “active”, that is it physically cleans the metal as it gets to the correct temperature, but don’t use this as an excuse not to thoroughly clean the joins before you apply the flux and after soldering make sure that any flux residue is cleaned off as it is corrosive.

The thin copper wire will also be removed, as it does nothing for the strength once the join is soldered.

Just the anchor points for the bracing wires to be added and then the assembly can be clad with wood.