Evening All,
I think that I have mastered the finer points of uploading images on to a host site without having to wait for my photographic library to be loaded first, so here is the latest on my current build.
I have been able to spend a little more time on this project lately and am able to report some new developments with specific reference to the wings. The model will have one half "solid" i.e. it will look just like a normal aeroplane with the external surfaces and colours, but the other half will be exposed to show all of the structural elements - that is why I have only moulded one half of the nacelle covering. The starboard (right) wing wings will be "solid" and it is these that I have been steadily working on recently, but I have also carried out an experiment for proof of concept for the port (left) wing halves.
I started by moulding the solid parts of the wings as upper and lower surfaces - I have described the procedure already. For the lower wing I had to put a rib in at the fuselage end as there was a small gap between the nacelle side and end of the wing. The rib was made from 15 thou card and two holes drilled and squared off to allow the spars to pass through. I also butressed the rib with some scrap card:
Blocks of scrap plastic were glued to the lower wing shell to provide support for the brass bar spars and to ensure that where I will have to drill rigging holes later, there will be continuous plastic otherwise the rigging thread is likely to disapper into the cavity and I will not be able to pull it tight:
To protect the nacelle I wrapped it in a plastic bag which had been slipped over the brass bars: that was to stop me from accidentally damaging the nacelle and attached rigging wires, and stop dust and other muck getting into the cockpit areas where it would be difficult to remove later. I cut a small strip of plastic to fit into the wing tips: experience with the top wing had shown me that a gap is likely to appear there when I shape this area and I wanted to ensure that there is enough plastic to allow for much filing and sanding. The spars were epoxied to the wing:
and the top half of the shell glued into place. The structure was held with hair clips while the resin cured and glue dried out:
Much scraping, filing and sanding followed to get the tips to the correct shape and shape the leading edge and thin down the trailing edge. Some filler was needed to sort out some unwanted depressions at the tip, but the aerofoil section is close enough:
With the wing shaped to the correct size and profile I could drill the holes for the booms. I do not like to let good, practical ideas go to waste so I employed the same basic technique to drill the holes for the booms as I have used on my 1/72 scale pusher builds. First I draw a line which runs from the undersides of the leading and trailing edges of the wing to a point vertically beneath the rudder post. The angle between this line and the boom on the side elevation drawing gives me the angle that I have to hold the drill chuck against the wing when I drill the hole. I taped the sub-structure to the plan drawing so that the wing is exactly in the correct position and then held the hand chuck so that it is in line with the boom on the plan. A piece of paper with the correct angle as measured from the side elevation diagram steered me to a nearly correct angle to the horizontal for drilling. I used a smaller diameter bit than the brass rod which I will eventually use for the boom
and then gently enlarged the hole with a needle file:
By offering the brass rod to the hole I could use the plan to make sure that the alignment was correct. To achieve the correct final angle of the boom from the horizontal I placed a block of wood 22mm high, 12.6cm from the trailing edge of the wing (actually the front edge of the block was laid over the leading edge of the horizontal tail unit on the plan: that is 12.6cm from the wing). The hole in the wing could then be enlarged until the rod rested on the wood block: voila the rod has the exact angle and orientation.
The above procedures had already been carried out on the upper wing, and I had added the ribs and filled and sanded them, so I was able to check the alignments of the booms by resting the tip of the upper wing on a paint pot and the other end on the nacelle. The tips and leading edges of the wings were squared using a small set square and the alignments of both booms checked: the upper boom should be exactly in line with and above the lower one, although their respective angles in relation to the wings are different.
Please do not let anyone ever tell you that scratch building a pusher is a) difficult, b) complicated, c) needs expensive tools and jigs: I am demonstarting that they do not. All of this was done on my work tray and desk top!
The ribs were made from 10 x 30 thou strip glued with liquid cement after the ailerons had been cut off:
Mr Surfacer 500 followed by Mr Surfacer 1200 was used to fill the sides of the ribs and riblets, and then the sanding and filling began. When I thought that they were almost ready I applied a thin coat of primer and continued with the filling and sanding....
They are now ready to paint.
The wing structure on the port (left) side has been given some thought. It looks complicated, but when broken down it is not really. I had some spare wing ribs becuse when I was making them I forgot that some ribs have two gaps between the spars, and some three. I had only made ribs with two gaps.... hence the spare ones. I started by sliding the ribs on to the brass bars which represent the spars on the real aircraft. When the ribs had been aligned over the plan of the wing they were superglued to the brass bars. A lenght of 40 thou rod was glued to the front ends of the ribs to represent the leading edge:
and 10 x20 thou strip was cut and bent gently with tweezers before being cemented with liquid cement to the rod to make the riblets:
A coat of thinned Revell acrylic ochre (88) was applied before the next part of the assembly:
That was adding the rigging. I used monofilament thread and passed it between the rib and spar at the relevant points. I had drilled some holes in some of the ribs because I thought that I might fill the gaps between the ribs and spars with paint, but that did not happen and I will not be drilling holes in the ribs which i will put on to the wings:
Now the structure could be completed by adding the narrow reinforcemnt pieces from 10 x 20 thou strip on the top and bottoms of the ribs, and the wire trailing edge. I used thin copper wire for the latter but it is too bendy so on the actual wings I will use some slightly thicker wire:
Concept proved. So now to paint the solid parts of the wings, add the roundel on the underside of the lower wing and drill the strut and rigging holes. The I can take off the nacelle cover and continue to add more interior details there.
Thanks for looking.
Stephen.
