SE5a CONSTRUCTION BEGINNING TO . . .

[Guest]

I completely agree with Barry, I think taxiing in a scale manner is all part of the experience and further enhances your complete operational skills.

Nothing looks more proffesional than seeing the model line up with the runway before starting it's take off run and returning to the pits after a successfull landing.

I guess it wouldn't be able to after an unsuccessfull one!!!

[Greyhead]

If you’ve read this thread from the beginning then you’ll know that I have been giving some thought as to how to make the control horns, which are quite thin; with the tailskid being steerable now is the time to put the thoughts into practice.


Thin steel is really the only option for the horn itself but attaching the cable to it is the problem, a standard clevis would be way too big and a cable passing through a hole would quite quickly be worn through. I hope I’ve solved the problem by bending a “yoke” from thin brass rod.





A thin brass pin goes through the hole in the horn, it’s peened over at the ends and finally the whole lot is soldered to the horn so that the pin isn’t taking the load. The only problem I can see with this is that the attachment point is slightly in front of the horn but I can get around this but slightly altering the angle of the horn and mounting it slightly to the rear.


The skid has a balsa TE extension and is then shaped with lightweight filler where the litho plate shroud will go.





The control is transferred from the horn to the skid via a thin pin to give the servo some “shock protection”, I might also use springs in the cables but from past experience I find these tend to make the steering a bit erratic.


With the shroud fitted that’s the skid virtually finished.

[wonwinglo]

Grahame have you seen those 1/32 split pins that Nexus supply in packets ? they come in very handy for closed loop systems and jobs like this.

[Guest]

A degree of protection can be offerred to the servo by incorporating a 'Z' in to the linkage without loosing too much control and it of course allows a degree of adjustment of the linkage length.

Possibly a bit more reliable than a spring link.

[Greyhead]

Barry

I’ve used small split pins before for the pulley shackles for example; they weren’t suitable for this job as they would have to be bent “the wrong way” around the pin and putting a twist in the legs made them too long, but I may use them for the rudder control horn because that has 2 cables attached both sides.

Richard

All the controls are operated by cables and so far I’ve failed in my attempts to bend them into a “Z”!!

Being serious that’s a really good idea; I could insert a short length of thin piano wire with a “Z bend” into the cable runs, probably use it as a connector to the servo arm, thanks for that idea.

Grahame

[Greyhead]

The hinge is a short length of brass tube soldered to a brass strip, which goes around the tube as a safety measure in case the solder joint fails. The pin is 22 swg piano wire and will have a brass “keeper” soldered behind the rudder LE when in position.





The rudder is recessed to allow the hinge line to be central to the radius of the LE which has additional strengtheners added.





The brass strip will be riveted to the fin TE either using brass tube or rod, I’ve not decided which as yet, I’ll be doing some experimenting tomorrow.

[wonwinglo]

Those hinges are not going to come adrift in any hurry Grahame,I oonce lost the rudder on my Parnall Elf at Old Warden in flight,the model came down flat with the rudder hanging,a few feet above the ground the model recovered just buckling the undercarriage,it was a very lucky escape as the hinge had fatigued with vibration,you can never be too careful with things like this.

[Greyhead]

The hinges are riveted to the fin TE using brass tube, given a final drop of cyano to securely lock them in place then faired in with some 1/32nd balsa.


As I explained earlier, at this scale “true” rib stitching doesn’t look as good as simulated in my opinion; for the wings I used a compromise which holds the covering to the under camber but looks OK but I can’t use this method for the fin and rudder because of the thin section and the core method of construction.


To simulate the rib stitching a simple jig makes life a lot easier. The thread, I’ve used brown here to show up, is laced around the pins, which are set to the correct spacing, and over the top of the Solatex; to hold them in place I use a tiny drop of thin cyano then give the whole lot a coat of Clearcoat.





Thin strips are cut and tacked in position over the ribs and when the top frayed rib tape is ironed on it bonds everything together. The finished rib tape looks near enough like the real thing for me!





I should have been more careful with the heat gun when shrinking the LE tape around the top of the fin because the covering has pulled back from the TE, but it doesn’t really matter as there will eventually be a litho plate cover running down the length of the TE.

[wonwinglo]

You should see some of the WW1 British aircraft Grahame,quite common to have S.E.5A's with stretched sagging fabric aft of the cockpit area,what they used to do was lace up the underside as a bag with leaded cleats,they used cord drawn through beeswax which takes cellulose dope,so the fabric was replaced in its disturbed state annd sometimes looked a right mess,so I would not worry too much about a few fin wrinkles,as ever aircraft on the front were short lived,if they did not tip onto their noses with novice pilots they would be quickly written off in spinning accidents.

[Guest]

I think 'perfection' with such coverings would actually not look as realistic.

I don't know what your thoughts on weathering this model are but the odd crease in the fabric to me will make it look more like, well 'fabric'!

[Greyhead]

I quite agree with your comments on “perfection”, in fact I deliberately introduce the odd scratch and / or dent on my models but what’s happened here is that I let the heat work too much on the covering whilst shrinking the edge tape. Luckily the TE is fairly wide so there’s still enough contact to hold the covering and it will eventually be covered.

[Greyhead]

When finishing the fin / rudder assembly I turned up the heat on the iron to shrink the edge tape around the curves, with the covering only attached to the 1/16th edge of the rudder I couldn’t afford any shrink back as happened on the fin. The litho plate shroud conveniently covers that fault and really finishes it off; the hinges and incidence adjuster now look the part.





Incidentally the tapes on the rudder are in fact parallel, for some reason they just look that way on the photo.

[wonwinglo]

Yes you get that distortion sometimes when doing close up work Grahame,the lens tends to show up the convex nature more.

This is one of the most detailed tail fin/rudder assemblies that I have seen in a long time.

That strip really sets things off.

[Greyhead]

The tail plane presents several problems, not the least of which is how to operate the elevators. I prefer to use the same method as the full size aircraft even if this is quite complex, as with the Elf; in that case the linkages were external so easy to check and maintain, but I have reluctantly decided that using the scale closed loop system is not practical for the SE5a tail plane, I still intend to use it for the ailerons. With the rear of the fuselage being open I should be able to hide the non-scale linkage.


The main spar, made from 4mm carbon fibre tube, will have a piano wire pin into the fuselage held by a grub screw similar to the wing fixing; it also acts as a pivot point for the variable incidence. I’ve also used a carbon fibre tube for the TE; this is short because the tail plane tapers towards the tip.





The ribs are cut long so there is sufficient strength around the hole for the carbon fibre TE during construction and are trimmed back later for the addition of a 1/64th ply facing.


Here’s a photo of one half, complete with piano wire pin, ready for the hinges and bracing wire hard points.





The tail is 2 separate units so I’ll connect them with a short length of carbon fibre slid into each TE to ensure that any adjustment to the incidence is equal both sides.

[Greyhead]

I’ve used the simple but effective core method for the elevators. With hindsight I shouldn’t have cut the lightening holes in the 2 outer bays; because the tail plane tapers down to just 1/16" at the tips there is very little strength left.





I’ve added some carbon fibre tows, which help. The carbon fibre TE joiner is only glued on one side to allow the 2 piano wire pins to slide into hard wood blocks in the fuselage, which are then held in position by 2 bolts tightened through holes in the bottom. If I can find a 0.9mm Allen key long enough I’ll replace the bolts with grub screws; I might have a go at extending the one I’ve already got.





The photo is blurred where it matters; the camera insisted on focussing on the very rear of the fuselage and not the blocks!


Finally a photo of the finished tailskid in position.





For practicality I’m going to bolt it in position, this will mean that I’ll be able to easily remove the skid, fin / rudder and tail plane halves from the fuselage if it becomes necessary. Once every thing has been thoroughly tested and proven, then I may attach the skid permanently as per full size.