SE5a CONSTRUCTION BEGINNING TO . . .

[Greyhead]

As Barry pointed out the stain has really brought out the grain; unfortunately, hoping not to sound too much like British Rail, it’s the wrong type of grain!


For such a high stress part of the aircraft the wood had to be close, straight grained. The way to simulate this is first to give the whole unit a dusting of matt white.





Then "stroke" the painted wood with 120 wet & dry in the direction of the "grain" that you want. Although not very clear from the photo, if you do ever try this technique you’ll find that it’s fairly obvious when you’ve done the right amount of "stroking" to produce the desired effect.





Then apply the stain, again in the direction of the "grain". This is only the first coat but I think it shows that the "grain" is now close and straight.

[wonwinglo]

Grahame,this technique reminds me of the old graining tools used by decorators etc,they consisted of a type of rubber comb,you applied the two tones of paint and dragged and moved the comb from side to side,your undercarriage looks most convincing,thats a neat trick.

[Greyhead]

Time to add a bit of metal work.


First the outline and fixing points are drawn onto thin card that is then covered with sellotape, which both strengthens and protects, before cutting out. The shape is then transferred onto litho plate as many times as required; this is where I hit a problem, I am certain I had another sheet waiting to be annealed but can I find it! I need 4 but 1 will have to do until after Easter when I’ll visit my local friendly printer for a bit of grovelling.


The shape can be cut out quite easily with kitchen scissors, not the wife’s best, it’s a good idea to buy a pair especially for this job. Once the shape is cut out turn it over for final sanding of the edge, this shows up any slight imperfections that would be “masked” by the drawn outline.





The fixings are embossed from the reverse side; “rivets” using an old ballpoint pen, the bolt heads using a nut soldered onto a bolt.





The undercarriage legs are looking a lot better now with a few coats of stain.

[wonwinglo]

Grahame,that undercarriage is a model in itself ! the representation of rivets is excellent,they look so realistic,those legs have come alive since the treatment mentioned in the prior posting,I enjoy your constructive postings immensely.

[Greyhead]

The axle fairing is quite a complicated affair consisting of hardwood leading and trailing edges fixed to the undercarriage legs with metal covers top and bottom. The lower cover is fixed but the top cover is hinged for access to the axle and to allow for excess movement of the axle in the case of a heavy landing.


The lower cover is simple to make from litho plate; the strengthening ribs are pressed into a “mould” made from a piece of scrap spruce using soft balsa as a tool and the rivets embossed using a dress makers copy wheel





The LE and TE are joined with cross grain 1/16 balsa to strengthen the litho plate as this area will be subject to quite a battering during take off and landing.





To complete the unit I’ve got to make a “piano hinge” to attach the top cover, then the legs will have the inner litho plate added, the fairing glued and pinned in place and finally the outer litho plate added to the legs.

[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.

[Guest]

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