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Design & Build Junkers F.13

An ugly plane but it grows on you

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Robert Parker10/06/2020 19:28:07
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1069 forum posts
1496 photos

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

junkers f13 2976340.jpg

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

Working from a plastic model and three view drawings

dsc08126a.jpg

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

J D 810/06/2020 21:35:23
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1765 forum posts
88 photos

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.

Robert Parker12/06/2020 17:51:20
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1069 forum posts
1496 photos

Hi All,

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

dsc08130.jpg

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

Robert Parker17/06/2020 20:44:09
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1069 forum posts
1496 photos

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

Robert Parker14/07/2020 21:21:44
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1069 forum posts
1496 photos

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

Robert Parker15/08/2020 17:10:19
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1069 forum posts
1496 photos

Hi All,

I have just ordered all of the balsa, ply, and accessories to make the model, and now that I will have cleared my workbench of what I thought was going to be a quick little project which took a little longer than I thought.

So hopefully by the end of next week, the build will commence at last.

That's all for now

Regards

Robert

J D 815/08/2020 17:20:12
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1765 forum posts
88 photos

Interesting project, post some more pics when you have some structure built. How are you going to do the corrugated surface?

Robert Parker15/08/2020 17:37:06
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1069 forum posts
1496 photos

Hi JD,

I'm not going to even try to replicate the corrugated sheeting. I did think about it but all of the bends/leading edges the corrugate sheet would crumple.

Regards

Robert

Robert Parker22/08/2020 18:50:23
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1069 forum posts
1496 photos

Hi All,

The Junkers has now entered the construction stage smiley

All timber has been weighed and allocated its parts.

Tail feathers built and fuselage started.

dsc08224a.jpg

There does not seem to be a great deal of wood, but there again most of the construction is open framed.

dsc08225a.jpg

And were off fin, rudder, tailplane, and elevators all made

dsc08226a.jpg

The first part of the fuselage.

This is taking no time at all at this rate.

That's all for now

Next, I will be making the second rear section and cutting out the formers

Regards

Robert

Robert Parker27/08/2020 22:20:07
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1069 forum posts
1496 photos

Hi All,

The fuselage is coming along nicely with no major issues. I do need to add engine cooling via the front have positioned the engine in the fuselage I'm going to have to open up the front where I had intended to have a dummy radiator, have to cool the engine details can follow.

dsc08228a.jpg

dsc08229a.jpg

Left and right side dry fitting

dsc08230a.jpg

Gluing up as a pair

dsc08233a.jpg

The full-size aircraft had a very boxy fuselage with a curved roof which has made it easy to make. That said the cockpit area will require some thought, more on that later.

dsc08234a.jpg

The fuselage really pulls in at the nose. the front former has not been glued in yet.

The RCV 58 looks quite small compared to the spacious fuselage at just under 6 inches wide at the widest point, plenty of room for the servos.

Next, is to make the formers for the top of the mid to rear fuselage and sheeting/planking.

That's all for now

Regards

Robert

Robert Parker03/09/2020 21:17:20
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1069 forum posts
1496 photos

Hi All,

After posting my last post I looked again and decided not to close in the fuselage at this stage as I would be making things difficult for my self for sorting out the wing mounting.

So I have made a start on the wings.

Cutting out the ribs took a little longer than I had hoped but all done and now that I am happy with them I have drawn them on the plans

dsc08237a.jpg

Starting on the centre section because I wanted to match up the wings and the fuselage and having a small centre section will make it easier to fine tune the fit between them

dsc08238a.jpg

The central four ribs are 3mm lite ply whilst the outer two are 2.5mm balsa

dsc08236a.jpg

Once the centre section was made it was time to start the outer panels

dsc08239a.jpg

I have tapered some balsa sheet to give me 5mm to 0mm of washout

dsc08240a.jpg

Underside of centre section

dsc08242a.jpg

Top side sheeting started.

That is as far as I have gone this week.

Next I'll continue with the wings.

That's all for now

Regards

Robert

Robert Parker06/09/2020 16:59:17
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1069 forum posts
1496 photos

Hi All,

I have completed the center section and fettled the wing seat to the wing, I thought it would be easier with a small wing rather than the completed wing less chance of damaging it. After some consideration, I opted to band the wings on I have also started the other wing panel.

dsc08243a.jpg

A nice fit between the wings and the fuselage

dsc08244a.jpg

Second wing panel glued up again building in the washout.

I have ordered the covering, looks like I'm going to need it soon.

Next, is to finish off the second panel and get it off the building board then it's time to make a start on the main undercarriage, metalwork is not my strong point.

That's all for now

Regards

Robert

Robert Parker13/09/2020 18:04:42
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1069 forum posts
1496 photos

Hi All,

Wing panels completed, however, progress on the u/c has come to a standstill due to working longer hours and need to fully get a grip on how it is going to go together.

That's all for now

Regards

Robert

Robert Parker20/09/2020 12:42:09
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1069 forum posts
1496 photos

Hi All,

Main u/c made and fitted looks the part especially with a pair of Flair wheels which I had for a Fokker DVII but were perfect for the Junkers.dsc08247a.jpg

Box artwork

dsc08248a.jpg

The kit which was a help to work out the geometry of the parts

dsc08249a.jpg

The end product still in need of some fine adjustment and the scale detailing but not bad. The basic construction is the same as the Flair Scout kits

dsc08250a.jpg

The wheels are a little on the large side but close enough.

Next, it's back to the wings and join them together

That's all for now

Regards

Robert

Edited By Robert Parker on 20/09/2020 12:42:24

Edited By Robert Parker on 20/09/2020 12:42:38

J D 820/09/2020 13:30:05
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1765 forum posts
88 photos

Nothing wrong with band on wings at this size, can save a lot in a whoopsy and quick to assemble..

Robert Parker03/10/2020 17:57:29
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1069 forum posts
1496 photos

Hi All,

I have progressed fairly well since my last post.

Wings joined, tail group fitted and hinges fitted, and fuselage roof made and the cockpit formed.

dsc08302a.jpg

The clamps are holding the aileron servo hatches

dsc08303a.jpg

Not as much room as I thought but enough to get the flight crew in. The floor is sitting on the tank

dsc08304.jpg

With all of the major parts made I could not resist putting it all together

dsc08305a.jpg

Still to attend to the nose

dsc08306a.jpg

dsc08307a.jpg

I am a little concerned about the size of the fin. rudder and stabiliser given how big the fuselage is in comparison and how much will it shield the prop wash.

dsc08308a.jpg

Looking good. The main reason I assembled her is that I was getting quite concerned over the weight, no not mine too late for that, but the aircraft seemed very heavy with the engine in place.

dsc08309a.jpg

Well no worries here then, all servos fitted, flight battery still to fit but it should go just in front of the u/c.

CoG set at 1/4 cord.

I have also weighed the airframe plus making an allowance of 1 5m roll of film and it came out at 6 1/2lbs, that's a whopping 1 1/2 pounds below my questimated weight.

dsc08310a.jpg

The servos are tucked in behind the last former as a starting point but this will be their final position

dsc08312a.jpg

Hinges fitted and pinned ready to cover.

junkers f13 2976340.jpg

And before anyone questions the position of the exhaust on the model, it is almost in same position as the full size.

Next is to finish off the nose and prepare the model for finishing

That's all for now

Regards

Robert

 

 

Edited By Robert Parker on 03/10/2020 17:59:50

Eric Robson03/10/2020 19:58:11
552 forum posts
126 photos

I like it a lot, back in the 1980'sPeter Neate I think I have the name right built a Ju52, he made rollers and formed litho plate panels for the whole model . He said the worst part was that the full size had different widths of corrugation which he copied , the wings being the hardest to cover. I don't blame you for not going down that road it looks great as it is now. Looking forward to seeing it finished.

Eric r.

Timo Starkloff04/10/2020 11:58:19
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447 forum posts
951 photos

That's going to be a nice one

Airliners are rare on model airfields, no matter what age. Looking forward to the finished model!

There once was a small German company called "Titanic Airlines" and they sold foam imitation for the Ju 52 surface. Light and with a good scale appearance, but only suitable for electric models.

Timo

Robert Parker04/10/2020 17:03:22
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1069 forum posts
1496 photos

Thank you, Timo, yes there are few airliners to be seen this will be my second and hopefully more successful than my last which did not get past the maiden.

my condor 2.jpg

My FW200 condor, massive CoG issue.

Regards

Robert

Robert Parker22/10/2020 19:21:27
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1069 forum posts
1496 photos

Hi All,

Well we're on the home run with this one.

Covering completed all servos installed and some detailing added.

So here are a few photos before the final photoshoot just to whet your appetites

dsc08321.jpg

I added the mock suspension units and painted the u/c and wheels

dsc08323.jpg

dsc08324.jpg

The twins are settling into their new office

dsc08325.jpg

Windows and doors added and painted on.

Just a couple more weeks for the decals to arrive from Callie graphics and then I'll let you see the finished model.

That's all for now

Regards

Robert

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