SE5a CONSTRUCTION BEGINNING TO . . .

[Greyhead]

One problem that has been causing my some concern is the way the top fabric is fixed to the longerons; they appear to use some sort of dome head fixing which shows through the side fabric. The only way I could think of was the “drop of glue” method after all the covering has been applied, but as I said earlier I’m not keen. Why they don’t use flat heads and make life easier for us modellers I’ve no idea!


Whilst searching the shops for something suitable as a basis for making the trim wheel, I came across some very small beads, about ½ mm diameter, which should do the trick if glued to the longerons before the covering is ironed on. These were sold in a haberdashery shop and are for decorating home made birthday cards I think. I must admit that I get some peculiar looks as I rummage through the boxes in these shops, the other customers are invariably women; the things we do in the name of aeromodelling!


Back to the trim wheel, I couldn’t find anything so had to resort to building from scratch; I printed some templates on self-adhesive labels and cut out 3 blanks from 1/32 ply.





These were assembled, the rim marked at 18º intervals and half circles routed out. It didn’t work out as accurately as I’d like but a bit of filling using epoxy and micro balloons made all the difference. After 4 coats of sanding sealer it’s ready for painting.





A coat of silver Solalac, with a few extras the end result is good enough, especially as it will be mounted low down on the fuselage side so only the top section, as shown below, will be clearly visible.

[Greyhead]

With the majority of the cockpit furniture ready I’ve started on the decking from the tank cover to the cockpit, which is not as straightforward as it might be!


The decking from the tank to about 1/3rd of the way back along the cockpit opening tapers up then it tapers down towards the tail; add to this the fact that there are no formers, only stiffeners, and you can appreciate the problem. I decided the only practical way was to make a jig and build it off the model, as there is a transparent inspection hatch for the Vickers I can’t cheat and add hidden formers.





The cut outs are where the stiffeners fit and you can see by the differing formers how the curvature of the decking has to change.


I clamped a layer of 1/64th ply in position on the jig, gave it a generous coating of watered down aliphatic glue, applied glue to another layer of 1/64th ply and clamped them together.





Then I left it overnight to really dry; in the morning I got a pleasant surprise when I removed the clamps, it held its shape, a bonus I wasn’t expecting.





With the success of the layering technique I decided to try making the stiffeners from 3 layers of 1/32nd ply; the first one is a complete “hoop”. The decking is covered with Clingfilm and the laminations held with small wedges.





Once again I’ll leave it overnight; I’ll post an update tomorrow.

[wonwinglo]

Interesting this Grahame,Aliphaetic resin will hold its shape as it cures and dries in a more brittle fashion to standard PVA,the latter tends to be a trifle rubbery,and thus not be as stable,you too have discovered this quite by the happy accident so to speak.

[wonwinglo]

No need to apologise over your trim wheel Grahame,it looks superb !

[Greyhead]

The stiffener has worked well and far more evident is the differing lengths of the laminations; with using 3 pieces of 1/32nd ply the inner lamination is about ¼ " shorter than the outer. When these are glued together it helps to explain how they hold the shape.

Before I can make the other 2 sets of stiffeners I’ve got to cut out the cockpit opening in order to alter the curvature of the decking; transferring the top and side views of the opening onto the curved decking isn’t such an easy task. I’ll tape some paper to the decking and then use a lot of trial and error until I get an acceptable outline, make a template from this and only then commit to cutting the wood after checking again that everything looks right!

[wonwinglo]

And the cockpit apertures are never shown very accurate on scale drawings anyway,one way is to lay a piece of Fablon onto the decking,work out the shape with a Chinagraph pencil ( obtainable from art shops ) straight onto the material,checking in particular the shape from the side view in relation to the actual depth using a photograph,then once satisfied cut straight through the fablon and laminations,this avoids the miralyte ply from having a ragged edge,then carefully peel off the adhesive film.

[Greyhead]

Well I should have read that last post before I started but it’s too late now! I used a paper template in much the same way . I must say that the stiffener looks and does its job a lot better that I thought it would.





But I have inadvertently caused myself a bit of a problem; with the decking being that much stiffer than I thought it would be it’s quite difficult to get the sides to conform to the correct shape.





With hind sight I should have cut the cockpit opening in both layers before I glued them together and clamped them to the rear former as they dried; I’m sure I’ll get it sorted even if I have to make the back section take up all the change in curvature, not quite scale but I’m sure no one will notice.

[Guest]

If you do something and you are not happy with it the only real solution is to do it again.

You will never be really content with the job f you don't. I did an area of decking that just didn't work out well and much as I told myself that it would be OK and no-one would notice, both of which were true, I was only really happy with it when I did it again.

You owe it to the rest of the model and all the time you are putting into this project to be completely happy with every single piece.

[Greyhead]

Richard

How right you are, I think I was a bit hasty with the last bit of the last post; the curvature isn’t that far out so I’m sure I’ll be able to bend the sides to the correct shape. After all we really build these models for our own satisfaction don't we?

It just “took the wind out of my sails” a bit; thinking how well the decking had turned out being that rigid and then to realise that in actual fact it had caused a problem!

[wonwinglo]

Grahame,I have had this very same problem with laminated miralyte,it tends to have a will of its own at times,Dave Boddingtons method was to apply ammonia to the ply prior to bending,a smelly nasty process but it does work,the reason why it has done this is because to a degree the ply has taken its own course and bulged to the natural curvature of the materia itself,what the ammonia does is to relieve the stresses in the ply laminate internally,I am assured that once dry it returns to a rigid state.

How about this method-Whilst you have the internal shape of the formers,why not take it one step further by making a couple of 'outer' ply shaped clamps,these could slide over the two laminations to hold it into shape and make sure it nips the sides cosily,the old woodworkers used to use this idea by making temporary clamps then to discard them,just a thought.

[Greyhead]

Barry to the rescue


Before I tried the ammonia on the real decking I experimented with the piece I’d cut out for the cockpit opening, not that I didn’t trust you Barry!!





As I needed to tighten the curve that’s what I tried, as you can see it did indeed hold its new shape and this was a rush job, not left over night.


What is not evident from the photo is just how pliable the wood became using ammonia instead of water and I only brushed it on, I didn’t leave it soaking as I would have done with water.


Having satisfied myself that this was the way to go I tried it on the decking but this time I will leave it over night to thoroughly dry.





I really like this “reverse” jig idea, I’m sure this method will get a lot of use in the future.

[wonwinglo]

Well there you go Grahame ! it certainly makes a big difference and allows the ply to go supple,the ammonia does not degrade the ply just in case you were thinking it could have detrimental effects,the adhesive bond re-cures in a few hours.

Clever trick.

[Greyhead]

Now that the decking is the correct shape it’s time to try and fit it. In order to work around the cabane struts and bracing wires the holes have had to be made quite large, these will be filled after the decking is permanently fitted, but it’s still a bit awkward.





On full size they remove the cabane struts and bracing wires, fit and cover the decking then re-fit them, unfortunately at this size we don’t have the luxury of being able to climb inside to tighten up the nuts!


The instrument panel is a good fit and looks quite “busy” when it’s buried in the fuselage; this is when the shadows and highlights really bring it alive.





It’ll look a bit busier with the clock,altimeter and throttle, which are fitted on the cockpit coaming, and the switch box fitted to the side decking, not forgetting the control column.

[Guest]

will you be doing the rudder pedals as well?

looks busy enough at the moment!!! lovely work as usual mate.

[wonwinglo]

This is the sort of cockpit that makes you want to hop onboard and fly her.