Aileron support spar

I recently added the aileron spar without having any trouble. Although the drawings are almost 100 years old and do not contain any tolerances the parts simply slip into place. We will see if this will change.

Next step will be the wing tip…

Rigging the wing

As I said before, the one rib is used multiple times. This gives me the opportunity to get a pretty impressive wing using three parts:

  • Rear Spar
  • Front Spar
  • Ribs

The front spar was almost the same as the rear spar. It is only a bit different in shape at the tip area due to the washout of the wing.

Click the below image for a better view. Here I allready included the shortened ribs of the aileron part of the wing. Like I mentioned they are the same as the main rib simply cut down.

Wing with two spars

Another from from the tip side:

Short ribs in place

First rib in place

Having defined a reference line using the rpevious mentioned fittings I was able to position the first rib. This root rib is completely closed with spruce on the outside. I will reproduce this using coloured cardboard. I would like to be able to cut all the parts directly without printing anything beforehand.

Positioning the ribs…

…proofed to be a bit complex. All the measures of the plans reference to the main wing fitting and this references the planes‘ centerline. So I was forced to design the fittings. Again since this is a very simplified plane by nature there is only on fitting to be drawn and this is used 4 times. Drawing was easy because provides dwg-drawings for most of the parts.

At this point I did draw it simply as is with material thicknesses of 0,2mm. However it does not seem to be a good idea to use card here. I had some bad experience when building the Komar by Drafmodel. So I will probably change to steel, nickle silver or brass here. Looks better anyway….

A nice home for the ribs

Having finished the main rib, I needed a nice place to put it. The Sg-38 has two main spars and I decided to start with the rear one. Why? Well, this one has less fittings to deal with.

The spars are pretty simple constructions. They are basically a large plate of 1,5mm spruce backed on both sides with enforcements of 8x4mm pine strips. Doing this in card is pretty challenging. The main spar is a piece of card 0,2mm thick ánd 600mm long. The reinforcement strips which take the stress and strain loads of the wing will be lasercut. I might need to make this in several pieces depending on the paper format. However this is the design phase and I will simply design them as is and think about parts arrangement later.

Spar 1

Creating some ribs

The first part to be designed is the rib. I’m saying „the rib“ because there is just one. This one design is used in different configurations throughout the whole wing. So starting here has a few benefits. The part is pretty straight forward. It will be cut from a single piece of 1mm cardboard. The corner and edge enforcements are 1,5mm spruce on the original. These will be cut from regular 160gr/m² paper/card.

Thinking of cutting: Maybe it is not needed to have the corner enforcement and all the other parts in this thickness cut by laser. I might design it to be cut by hand with a clever layout for cutting efficiency. Or I might acquire a cutting plotter like the a Silhouette Cameo by Graphtec. This is a small desktop cutter which should be suitable for a smaller project.

I am also thinking about a layout which makes it quick and easy to position all the parts in one step. Like glueing the rip structure to the enforcment parts which are still in the paper frame and cutting everything afterwards (I think I might need an image to explain that). This would save me from having to number all the parts indiviually.

This is where it starts.

So here I am, with a bunch of plans. What am I gonna do?

Well, we will start with the most complicated part. The wings. Checking dimension I decided on the scale to be used. It came out at 1:8 just because the strips of wood used for the ribs are 8mmx4mm.


Living in a digital world what did I do first? Printing all the plans 😉