After finishing all the rolls and fittings I declare the wing design finished. I am now heading towards the building rig. Every plane is only as good as the rig it was built in. And I will incorporate some of the methods used in building RC planes. More on that later.
The fittings for connecting the wing support wires are drawn straight from the plan. They are drawn as simple sheets with one side creased by 90°. The mounting holes get doubled with a piece of welded material. And this is exactly how it was done. I had the markings on the spar allready inlcuded (lucky me), so positioning the parts was easy. To tell the thruth I only made one and the other three were just mirrored. The spars are exactly parallel and same size and the parts itselves are mirror symmetrical.
And the fitting in its natural habitat:
Oh yeah, here you can see a little bracket that gets attached with the same screws as the fitting. These are used to connect the fittings with a steel cable to accomodate some of the load by the support lines. Some of these run to the central wing tower and some are running backwards to the fuselage.
And finally the other other one:
Yepp, forgot to include the bracket here
The inner guide roll in its place. The rolls are the same as on the outer guide. I simply made them of stacks of 0,2mm metal discs. These discs will be soldered together. At least I will try to do it so. The guides will get screws in appropriate scale as axles. The plan says M6, this would be roughly M0,7 in my scale.
Interesting detail here: The small rectangular hole beneath the access hatch is the exit opening for the aileron control lines. These run „open air“ from here on.
As I mentioned before I tried to find readymade hardware. However when I started designing the guide rolls none of these seemed to fit very well. So I started creating these parts in a way that they can be made from etched metal. Well…these guys came out really small:
At least from my point of view. If you ask anyone from the ship-cardmodelling department they will laugh at you. They are using even smaller parts like blocks in 1:250.
The above roll in its working place:
Having finished the corner bracings I moved on to the planking. This was pretty straight forward. I included an offset of 0.1mm as I am planning to use 160gr/m² cardboard for this. My experience for these parts is that the neutral fibre is roughly in the middle for the larger curvatures. Thickness for this material is about 0.2mm. For the root rib I could have used an 0.2mm offset. However ther difference is marginal and the final piece will need a little bit of trimming anyway.
Designing with fully coloured cardboard in mind gives new perspectives. I don’t have to pay that much attention to details. Parts like the planking can be designed a bit larger and then trimmed afterwards. Howver I am aiming to get it perfect 🙂
Remember Pinky and Brain? „What are we going to do tomorrow night, Brain?“
Well, today I finished the last corner enforcement, narf, tedious job.
Alexander included my report in his section „Bauberichte“.
Make sure to check out his website, loads of stuff about primary gliders there. Not just the SG-38.
I designed these two elements according to the drawings and positioned them according to the drawings, and….bam, doesn’t fit:
Problem is, the diagonal struts collide with the upper and lower strips of the bracing wall. And looking closer at the drawings I found that they cannot fit as the strips all run at basically the same height. I wouldn’t be surprised if each and every builder of the SG-38 ran into this problem. The solution is either quick and dirty -> forcing the struts under the strips and thus compomising in stability, or having to rebuild the bracing wall completely. One third solution is possible: The drawings I have are rather foggy from the copying process. So I might have misinterpreted some of the dimensions.
Anyway I redesigned both walls and stretching everything a bit and I was able to sufficiently squeese in the diagonals:
The opening that is visible in the wall is for the aileron control lines.