SE5a CONSTRUCTION BEGINNING TO . . .

[wonwinglo]

Grahame,this undercarriage is a model in its own right,I love the way that you have executed the litho panel which hides the bungee sprung cross axle,are you going to make the wheels 'live' this stops any tendency to ground loop as the axle is running and not the wheels ? just a thought but I suspect that you will go for the originals construction with the axle in a sprung state via the bungee cords.

I can see that you are enjoying this project and there lies a point,never ever build something that you never have your heart and soul in,you just got to love your subject matter to get the very best from it.

Was it soap rubbed onto the litho to allow it to be worked,followed with heat ?

 

[Greyhead]

Barry

I’ll definitely go with the original bungee sprung axle and let a heading hold gyro sort out the ground looping.

To anneal the litho plate I smooth soap as evenly as possible over one surface, let it dry completely, heat until the soap turns a dark brown (almost black) then allow to cool naturally. I use the largest ring on the gas hob to heat the litho, holding it quite a way above the flame; a blowlamp has a too concentrated flame and you tend to get hot spots so the annealing isn’t even.

A point about litho is that it all varies; my new supply won’t emboss the hex head bolts without splitting so I’ll resort to gluing on small slivers of suitably sized hex plastic rod. Most of the nuts and bolts are actually hidden by the bungee cord fairings so they needn’t be added.

Grahame

 

[wonwinglo]

A heading hold gyro,now there is a thought for tricky ground loopers,so you switch the device off in flight to make full use of the rudder when airborne,have I got that right Grahame ?

I have some litho so will have a play with the annealing process which makes it malleable,I once covered a FW.190 wings with this it looked excellent,I would imagine that the quality varies a bit that is why some worked better than others.

 

[Greyhead]

Ground Looping and the Heading-Hold Gyro.

A heading–hold gyro is definitely the answer for any model that has poor ground handling. The gyro generates a signal when it is moved in a particular plane, not a model plane but horizontally for example. By mounting the gyro accordingly it can monitor yawing, pitching or banking, in this case we use yaw and set the gyro to apply opposite rudder.

A standard gyro only generates a signal while the model is actually moving in the monitored plane but as this correction signal is virtually instantaneous it is quite adequate to smooth out any affect from gusty wind conditions in the air and would possibly be OK on the ground if taking off from smooth Tarmac. Taking off from grass is another matter all together and “ground looping” often occurs before the model has gained enough speed for the rudder to be very effective.

A heading–hold gyro “remembers” it’s orientation as it is switched on and holds the signal until it returns to it’s original heading; they obviously have to be able to be switched on/off using a spare channel otherwise the model would take off and fly straight until it was out of range!

In practice the model is switched on with the gyro switched off at the TX, when ready for take off the model is pointed directly into wind and the gyro switched to “heading-hold”; as soon as the model is airborne the gyro is either switched off or to “standard mode” if the wind is a bit gusty. If the model needs rudder as well as aileron to turn then the gyro needs to be off for the model to turn satisfactorily so in gusty weather there is a lot of “switch throwing” to be done.

As yet I’ve never landed using the gyro as “ground looping” isn’t such a problem as the model is slowing down and isn’t about to leap into the air cross wind but I see no reason why the gyro shouldn’t be used, it would certainly make for a dead straight landing approach!

Barry

If you think this post would be more suitable for a different forum (tutorial??) feel free to delete this last bit and move the rest.

Grahame

 

[Greyhead]

I decided not to make a separate “piano hinge”; there are two reasons for this:


1) The hinge will not be used that often so the litho plate will be strong enough.


2) The sections of the hinge are fairly long, about ½ inch.


The first job is to make the top cover allowing enough extra material to form the hinge and the front section, mark the sections then cut the front free. The cover is backed with 1/64th ply and the appropriate sections bent down, these will eventually be cut off but for now they will ensure there is sufficient clearance when the other sections are bent around the wire hinge pin.








Here is a photo showing the top cover completed with hinge wire in place; the front section is yet to be started.





The front section is bent around the hinge wire and then the completed top cover glued to the axle fairing.


With the cover closed





And open





With the axle fairing fixed in place the bracing wires can be fitted and a coat of etch primer applied to the litho plate ready for a coat of PC10.





The undercarriage is now finished as far as it can be; the axle is awaiting the arrival of the Williams Brothers 5" Vintage Wheels and the tops of the legs need to be made an exact fit when the fuselage is made.

 

[wonwinglo]

Splendid workmanship Grahame,it really does now look the part,thank you for these detaild descriptions of your build,this is normally the thing that we just have to guess at how the modeller has gone about things when looking at his model,the application of litho after being reworked looks most realistic.

Thanks also for the low down on these heading lock gyros,we had a raw beginner come out on the field once with one fitted to a trainer,he installed it in a fixed state and the model was last seen heading due south never to be seen again ! at the time he never told anyone about it,that was until the model did not turn and then all was revealed.

Is the one that you are using the one intended for helicopters ?

 

[Greyhead]

The gyro I use is made by Futaba and is designed specifically for aircraft; I’ve no idea what the difference is between this and the helicopter type.


The fuselage consists of a fairly substantial front end with a rear section framework from ⅛" square spruce; the front section is built first as a unit and then the rear framework added.


Although the current trend is for interlocking “Liteply” formers I still prefer to use birch ply for these high stress areas. The formers are “notched” to key into the fuselage side doublers; this greatly increases the strength (even though the fit isn’t up to the standard found in CNC cut kits!!).





F2 has a hole cut to suit the fuel tank and consists of 4 pieces glued together for extra strength at the front cabane and front undercarriage mounting points. The rear undercarriage mounting cross member is also made from 4 pieces of ply.





Ply doublers will “tie” the formers together to form the front section.

 

[wonwinglo]

Dont know so much about CNC cutting Grahame but your formers look fine to me,remember those awful die-crushed things that Top-Flite and such used to churn out ? nothing to beat neat hand fretted ply parts nicely sanded,the internal bits take the time dont they ?

Well you are really progressing well, and I can see that you must have given the front end equal thought as to the most ideal method of construction,fuel tanks are always a right pain especially as they often leak and go wrong as well,good access is always needed.

Regarding Liteply,it is fine for some jobs but where accurate alignment is needed as here,the LP tends to need extra stiffening,which sort of defeats the whole exercise,I agree.

Nice work as always Grahame,you are building up a first class record of your project.

The gyro must be an heading lock type I would imagine,keeps the nose straight as a die into wind,the wonders of modern technology,we have enough to think about when flying our tricky models and these devices certainly help,although having said that,and knowing what a shopping trolley my own Parnall Elf is on take off, I have never used one myself.

I think that 'Greatplanes' did one ?

 

[Greyhead]

The front section assembled.





If you’ve read my Parnall Elf thread you may well notice the similarity in design; why change a winning formula? One difference is that I’ve reverted to my preferred method for mounting the engine, which wasn’t the most practical with the highly tapered front on the Elf.


The “engine” bearers are glued and screwed directly to the side doublers; the engine is mounted on a Paxolin plate, which in turn is bolted to the bearers. This method gives great rigidity to the front of the fuselage and also makes changes to the thrust line easier if required.


With undercarriage attached.





The front position for the undercarriage mounting is fixed by F2; this has to be accurately positioned because it is also the mounting for the front cabane struts. Having built the undercarriage first it was an easy job to make small adjustments to the position of the rear mounting cross member to ensure a good fit (in practice it needed to be about 1mm further to the rear than I’d drawn on the plan). Done the other way round, bending and silver soldering the piano wire to fit the fuselage, would have been a lot more problematical!


Showing “engine” bearers.





Another shot showing the wide spacing of the bearers.

 

[tigertc]

Se5 turning into a work of art....totally awesome work dude.

 

[Bunkerbarge]

An absolutely beautiful job and a pleasure to watch traditional modelling techniques used throughout.

Thanks for the postings.

 

[Bluewavestudios]

Just had a Browse to keep me up to date,

This one is just getting better and better as it goes along, a real credit to Grahame.

Keep up the good work and looking forwards to the next installment.

Regards..........Mark.

 

[Phoenix]

keep up the good work

its looking good already :D

 

[Greyhead]

A Change of Plan


I decided that I’d complete the front section of the fuselage, as far as practical, before attaching the rear section thus alleviating the need to swing a 3-foot fuselage around in the confines of the workshop; always a recipe for damage!!


The radiator consists of 2 separate units joined by pipes, the top pipe also incorporates the filler cap, the intervening gap has a metal cover plate; as I intend to use the radiator cap as a convenient fuel filler point I needed to model the 2 header tanks. When trial fitting them I realised that the cover plate would have quite a “double curve” to fit to the rear radiator former (see post #29) and this didn’t seem right. Checking photos showed that in fact the rear radiator former should have a flat top, the transition to curve taking the entire length of the cowl. Wonderful thing hindsight! Now I know the shape of the radiator it’s quite clear on the 3-view drawing, what a difference that thin line makes when you realise what it is!


Luckily the former wasn’t glued in place so a replacement was made and the plan changed.





The grills are made of aluminium mesh from a car accessories shop, stretched to open the slots to more closely resemble the true hexagonal shape of the original. I’ve not yet decided whether to cut the former out behind the mesh or just paint it dark, I my compromise and cut out the top section, which shows above the radiator shutters, and paint the rest.





This shows the undercarriage front fixing; it’s recessed up into the fuselage to allow the front flying wires to pass through the fuselage sides via dummy attachments and be tensioned inside using turn buckles.





I’ve also made a correctly dimensioned “bullet” at the cross over point of the undercarriage wires. The SE5a certainly took streamlining quite seriously, the undercarriage bungy cords are encased and the pilot foot holes have cover flaps.

 

[wonwinglo]

Grahame,I had no idea that you flew helicopters ? the correct term for the bullet a la WW1 style is Acorn,these prevent singing of the wires with the subsequent chafing.

Nice work as ever and the radiator grill looks good,amazing how much there is to think about with a model like this.

If you are learning to fly helicopters then this is the best way ever to sharpen up your rudder skills for your old timers !

 

[Greyhead]

Barry

The helicopter is a small electric “indoor” model called the Humming Bird that my son bought from a trader at our annual club air show in June this year; I have to admit that helicopters don’t really interest me that much.

On the box it reads in large print:

1. Open the box

2. Charge the battery

3. Fly your Humming Bird

If only it were that simple!! It’s now more carbon fibre tows and super glue than original model.

My son can now fly it for about 20 seconds before he “loses it” and has to make a quick landing but I still can’t get it safely off the deck. These things are certainly for the young with quick reflexes, but I suspect that as with most things aeronautical small equates to more difficult to fly.

 

[wonwinglo]

A friend passed his Humming Bird onto me Grahame,could not get the thing to fly for love or money,finished up making my own blades for her in the end,she would resonate on the ground with barely enough power to get off.

My Twister Bell 47G flies like a dream by comparison.

 

[Greyhead]

The next thing I want to do to the fuselage is to fit the cabane struts, but I don’t like to put my trust in geometry for this critical job, especially if it’s my geometry!


This means that before I do this I’ll make the top wing centre section, hold it in position with a temporary jig and then fit the cabane struts thus ensuring that the wing incidence etc. is correct.


If I’m fairly confident that what I’ve drawn on the plan will translate into the actual part when built then I usually make a “kit “ of parts.





The 2 outer ribs are 1/16th ply the others 1/16th balsa made using the “sandwich” method and then the inner ribs are shortened to fit the trailing edge cut away.


The hardwood blocks have a hole for the wing location wires drilled at 5º [ EDIT: information received later suggests that the correct dihedral angle should be 3º 20’. I hope to be able to modify the model accordingly. Information received even later suggested that the dihedral angle was indeed 5º; because of this conflicting information I decided to leave things as I'd first designed] to give the correct dihedral and grooves routed to fit onto the 1/8 x 1/4 spruce spars. The yellow “pegs” are in fact snake inners tapped 2mm that will have grub screws to lock onto the wing wires to hold the wings in place.





The build starts with the trailing edge.

 

[wonwinglo]

Centre section layout,everyone has their own way of doing things and very interested Grahame in your own approach,temporary jig is the only way forward as you are preparing here,have tried different versions one version is two templates fitting saddled to the upper portion of fuselage,the forward one governs the wing incidence whereby the centre section ribs fit,I have tried fitting piano wire frame first locking this to the centre section ribs via the overhead jigs,the jigs can be torn free once everything is set up,should you need removeable centre section then flattened brass tubes can be screwed into ply side pieces and ply outer centre section ribs,the usual balsa cladding is then added fore and aft,Don Stothers had some great ideas for his lovely biplanes and used self tappers with head removed and drilled out for rigging wires,on his large models he used lots of car bundy tubing with suitably flattened ends,all ideas to be food for thought.

But no doubt you will have a good mental picture in your mind of the way you are tackling the centre section strutting,no easy task whichever way that you choose.

 

[Greyhead]

The centre section is at the stage ready for the fitting of the cabane struts, the top and bottom sheeting will be added later. The carbon fibre leading edge really adds to the torsional strength; the wings with carbon fibre leading edge and carbon fibre spars should be as stiff as a board!





The hard wood wing retaining blocks / spruce spars have had a few wraps of carbon fibre tows, very little weight but tremendous increase in strength for this crucial area.





The cap head set screws will be replaced with grub screws before the top sheeting is added; these are just for a test to make sure that they will hold the wing in place and they certainly will. They only need to be “finger tight” to make the wires solid so a “nip up” with an Allen key and the wings will be going nowhere!





Now the jig to design and get the cabane struts fitted, but first a few days away in the caravan, complete with electric glider of course.