SE5a CONSTRUCTION BEGINNING TO . . .

[Guest]

Grahame,

I can only repeat what I have said before, this is a truly awesome model, even more so now she is gaining her colours, the weathering so far looks fantastic. I trust this one will be doing the rounds at the shows in the new year because I can see her reaping in the awards.

Keep the pics coming

Regards.....Mark

[Greyhead]

Mark


The only show where I’ll display the model will be my club's annual air show, which is the Teesside Model Flying Club, near Stockton upon Tees. If any one's up this way in June I can thoroughly recommend it as an excellent day out.


Grahame


I’ve repainted and weathered the offending front section of the fuselage and am now happy with it.


The elevators are actually operated by a pair of pushrods but I want it to look as if the scale control cables and pulleys control them. To do this I will run a cable from the top control horn on one side to the bottom control horn on the other and vice versa; to take up any slack I will include springs in each cable run.


The first thing to do is to find out where any slack in the system may be by temporarily joining the elevators together and connecting the control horns with cotton. I did each cable separately to ensure there wasn't any interaction.





Moving the elevators from full up to full down showed that there is in fact no noticeable slackening or tightening of the cables; more by luck than judgement I’m sure! I’ll still incorporate the springs but with just enough tension to stop the cables flapping about


I made up the 2 cables complete with springs; as they won’t be seen I used the easy option of brass tube as crimps, with a drop of cyano just to be sure.





I fitted the cables through the fuselage before threading them through the tubes built into the tail plane, one spring each side.





I then attached the cables to the control horns ensuring that there was equal tension in each cable by the simple measure of ensuring that each elevator was at the same relative angle. There is a little friction introduced by the pulleys and the springs running inside the tubes but definitely not excessive, as I’m using a separate servo for each elevator I’m certain there’ll be no problems.


Just the acetate “windows” and frayed tapes to fit now.

[Greyhead]

Apparently when I said in my last post “ensuring that there was equal tension in each cable by the simple measure of ensuring that each elevator was at the same relative angle” it didn’t mean much; I knew what I was talking about but of course I’d done it! Rather than just explaining the tensioning bit I thought I might as well do a step-by-step account of the elevator set up. If you’re building an SE5a, or similar and want to incorporate the pulleys etc., or you’re a bit “nerdy” like me and like reading technical stuff then the next few paragraphs may be worth reading. Then again you might just be suffering from insomnia and what boring to sleep!

The cables each consist of a spring with “tails” attached to both ends. A short “tail” that is attached to the control horn on the same side as the spring, which I’ll call the sprung cable. A long “tail” that passes through the fuselage and attaches to the other control horn; I’ll call this the non-sprung cable although of course the spring does have exactly the same effect on it.

My original idea was to pass the non-sprung cable through the centre of the spring of the other cable but in practice this wasn’t a good idea. When some tension was applied to the spring and the coils opened slightly the non-sprung cable could get between the coils and this caused a lot of friction; running the cable on the outside of the spring, between it and the tube in the tail plane, caused no problems.

I threaded the cables through the 2 halves of the tail plane bringing the sprung cables out for the top control horns and the non-sprung cables out for the bottom control horns. The choice was purely arbitrary but if done the other way round the following steps would have to be reversed.

The model was turned upside down and the non-sprung cable pulled until the spring hit the fuselage side. With full up elevator (remember the model is upside down) I bent the cable back on itself ¼" past where it met the control horn thus ensuring that in practice the spring would never hit the fuselage side. The cable was threaded through the control horn and fixed by binding with thin copper wire and a drop of cyano. This was then repeated for the other side.

The model was then turned the right way up and the elevators temporarily joined by a length of spruce and clamps. One of the sprung cables was threaded through its control horn and pulled until there was sufficient tension to keep the cable tight and provide enough friction on the pulleys to make them rotate when the elevator was moved from full up to full down. This turned out to also be about ¼" but I tensioned it just that bit more to be on the safe side and then terminated the cable as before.

When I removed the spruce “joiner” the spring contracted and I had one elevator deflected up and the other deflected down.

Now we get the "equal tension" bit! I threaded the other sprung cable through its control horn and tensioned it until both elevators were in line. When operating the elevators together there’s no pulling against the springs as the tension of one counteracts the tension from the other.

[Greyhead]

I used canopy glue to attach the acetate “windows” and then added the frayed tapes. They’ll be painted once the inspection “windows” in the wings and the aileron connecting wires are in place and taped.





I’ve bolted the fin to the fuselage and added the tail plane support wires; they should be solid wires but I decided to use fishing trace because it would make life easier if / when I have to alter the incidence of the tail plane. I don’t know what it is but they just don’t look right, so much so that they’ll have to be changed, if it means more trouble later on I’ll just have to live with it; I think I’ll get some 24swg piano wire and hope that looks better.

[Guest]

The se5a looks absolutely stunning. It's been great to watch the build progress and it's really apparent how much effort and attention to detail has gone into this build.

I remember seeing the initial posts showing the images of those inspection windows on the actual aircraft - the model really does look the part and has really come alive now.

[Guest]

Beautiful job, Grahame! Absolutely beautiful!!

Steve

[wonwinglo]

Grahame you have done the subject proud,and what a great record we have of your SE5a thanks to your kindness,how you keep your workbench so clean and tidy after building such a model beats me ?

Cleaning your model after flying will be a task in itself, with all of that beautiful detail to look after.

The elevator cable springs remind me of the longitudinal trimming system for the Tiger Moth, whereby a tension spring gives a false sense of fore and aft movement,the first time that you see it makes you realise how effectivly simple it all is.

And now begs the question ,what are you going to build next ? we will not deny you a well earned rest,but I doubt that you will for one minute even consider it ?

[Greyhead]

The “windows” were virtually the first thing that I considered when starting this model, they have influenced the design and construction throughout and will actually be virtually the last thing to be added to the model. I’ve replaced one of the tail plane support wires with one made from 24swg piano wire and it’s a lot better, the model shop hasn’t got any in stock but fortunately Mike’s putting in an order this week so it should be there some time next week. In the mean time I can get on with the rudder and aileron control cables.

I have already given some thought to my next project; I quite fancy building a twin, either a Vimmy or a Gotha are favourites at the moment. I prefer the Gotha but it has some serious drawbacks, no the least of which is the “pusher” design, which if done conventionally will make for a lot of lead up front to get the CG right. I’m toying with the idea of a “standard” engine mounting at the front of the nacelle with a lay shaft to the prop at the rear, but as I’m a modeller and not an engineer it might be a recipe for disaster. If I go down that route a lot of experimentation will be called for!

Then again I really like the Pfalz DXII: decisions decisions.

[Guest]

Then again I really like the Pfalz DXII: decisions decisions.

Just thinkwhat a great counterpart the Pfalz DXII would be to the SE5a - and lots of opportunities for some interesting camouflage too - hexagonal camouflage and some vivid fuselage colours too! Can't wait to see it progress - whatever model you choose!

[Greyhead]

It’s been quite a busy week but not a lot to show for it on the modelling front; to start with on Sunday I got my second “badge of office” as an official wrinkly, the first was my bus pass and now I’m a Granddad! Between the cooing I managed to get a bit of time down the shed and threaded the aileron control cables. I’ve tested the top ailerons and they work fine, but of course they’re the easy ones, I’m hoping to test the bottom wings and also connect the top and bottom ailerons tomorrow.


One thing I’m pleased with is the control horns, this is the first time I’ve had them “operational” and I have to say I think they look good.





In the neutral position the shackles are inline with the cables.





It’s only when the ailerons are deflected that it shows that the shackles aren’t actually free to pivot.





Of course the ailerons will be at neutral when the model is being “examined” and if anyone can see the shackles when the model is flying they’re a better man than me!

[Greyhead]

I’ve said before that I like to get the positions for the radio gear sorted out as early as possible in the build so as not to get any nasty surprises at a later stage, after all the whole purpose of the exercise is to produce a radio controlled model! Unfortunately, although I confirmed the principle for the aileron control very early on in the build, the practicalities of actually fitting it into the model could not be worked out then because I had no idea how much spring tension would be needed or how much “slack” the system would have.


This is the design that I tested to prove the principle.





I fitted the spring temporarily using the inserts from an electrical connector strip and adjusted the tension as necessary. Because of the tension I had to reduce the length of the cable joining the top ailerons slightly then all worked nicely.





I was surprised to find that as with the elevators there was no noticeable tightening or loosening of the cables and the tension required was the same, ¼" plus a bit for safety; I’d expected to have to use about double as the one cable controls all 4 ailerons, runs round 4 pulleys and there is a lot more of it.


Fitting the spring the way I have done has given me an idea; I’m going to turn the design “inside out”, that is I’m going to attach the spring outside the servo arms not between them as originally intended. Doing it this way means I’ll be able to move the servos a lot closer together, which will mean less bending of the snake inners, which in turn will make for a smoother and more precise movement of the ailerons.


Having got to this stage I couldn’t resist the temptation to fit the wheels and take a couple of photos.








Looks a bit “naked” without all the wires, Lewis gun and a pilot!

[Guest]

It's the photo we've all been waiting for! The SE5a looks beautiful assembled! I bet you can't wait to don the flying goggles, silk scarf and prepare for take-off!

The white lettering, red wheel covers and markings really do lift the dark green too. It looks superb!

I must admit that those paving slabs look a little incongruous though!

[John]

What amazes me apart from the brilliant job your doing with this build and the helps and tips your giving to others, is the fact you have time to photograph and write about it in such detail.

[Guest]

Grahame,

I am very impressed with the photo's, she does look the part indeed, Somewhat Ironic set against a hexagonal patio background and the Pfalz having already been mentioned as a possible next subject for you !!

I have a feeling those hexagons are going to be haunting you for a while yet !!

Regards.....Mark

[wonwinglo]

Looks beautiful Grahame,it does not seem that long ago that you laid down those few few pieces.