Design & Build Junkers F.13

Hi All,

Well, I thought I would dust off my drawing equipment once again whilst I'm waiting for some decals to arrive from across the pond.

I came across Pete Crosby's earlier post, a very big build and it got me thinking and doing a bit of digging around the web.

First built in 1918, it was the first all-metal transport plane and carried 2 crew and 4 passengers, the crew sat in a semi-enclosed cockpit whilst the passengers were in the cabin.

The prototype had a wingspan of 14m later aircraft the wingspan grew to 17.050m.

So a 1/10th model comes out at 1700 mm (67" wingspan and a length of 970 mm (38"

Materials: Balsa & ply

Power: It is calling for IC and a four-stroke at that I have an RCV 58 sitting in a box looking for a bit of action. My initial thoughts were electric but being as I have a spare engine or to lets put one to use, eventually

Not my own work, but an idea where I want to get to

Working from a plastic model and three view drawings

After a total of 8 hours and a partial redraw, I ended up with this. I made a simple error, I worked from different references which gave me conflicting information due to variations of the aircraft being built between 1918 and 1932. As can be seen, I have drawn two stabilisers, having drawn the wide narrow one yesterday I found that the narrower but wide one being used more so I'm going for that option as well as the narrower one will be less prone to damage.

I have made a start on the wings this afternoon but wasted too much time looking at aerofoils. The full size had a really deep section. For it to be to scale, which it does not have to be for me, it works out at 65 mm deep with a chord of 320 mm

That's all for now regards

Robert

There is a full size flying replica of this interesting aircraft. It is though powered by a Pratt Whitney Wasp for operational needs and is fitted with a tail wheel. Based in Switzerland I think.

Hi All,

I have completed the basic wing drawing, quite straight forward really.

I'm putting a 6mm washout in the wing along with the 5 degrees of dihedral.

A little undecided about the sheeting whether to go partial sheeting and cap strips as per left-wing or fully sheeted just thinking about weight issues. The ribs in the center section will be 3mm liteply and the outer panels 2.5mm balsa. Main spars in the center section are to be 9 x 6 hardwood and hard balsa in the outer panels and the rear spars to be 6 x 3 hard balsa

I give a little thought to the undercarriage and basically going for a practical solution that is not far from scale.

I can confirm power will be from my RCV CD58 which fits very nicely in the engine bay and I can even use the exhaust in the scale position, like a chimney! I can now draw the firewall bulkhead now I have finalised the power source and draw in the tank position as well.

I'm guesstimating the AUW to be around the region of 8 lbs or so

Next, Ribs

That's all for now

Regards

Robert

Hi All,

I have drawn the tip and root ribs and made templates for them and form the rest of the ribs using the sandwich method.

I have also done a provisional CoG calc using an online CoG calculator based on estimated weights of 8lbs and then 10lbs for a starting point.

Wing area 696 sq in

The 8lb model has a wing loading 26oz/sq in and a stall speed of 25mph

whilst the 10lb model came with a wing loading of 36oz/sq in and a stall speed of 28mph

That's not a bad starting point, however, could any of you out there advise me on what static margin would be acceptable for this type of model. With the 8lb model, I went with 10% with the static margin which gave a CoG of just over 3".

That's all for now

Regards

Robert

Edited By Robert Parker on 17/06/2020 20:44:39

Hi All,

Life has got in the way a little bit with the Junkers, I started the drawings when I was put on furlough. However, my wife didn't fancy the idea of me being at home and being paid so she suggested that we (I) rip out the bathroom as this would be a good opportunity being as we could not go abroad on holidays. Well, this has turned out to be a much bigger/more complicated project with walls being hacked off and re-rendered then tiled and then fit the new suite which when unpacking the wc was broken and the supplier is not responding to emails let alone phone calls.

In this last month, I have bearly done any building to finish off my present build to clear the way for the Junkers.

Still, by doing the bathroom I should earn some brownie points to go flying.

That's all for now

Regards

Robert