Jungster 1 & 2 aircraft

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Dominic Eller

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Previous owners have flown my Jungster a couple hundred hours before I bought it as a firewall forward project. I thoroughly inspected my wings and they are in great shape. They were extended 2 feet on each side at the roots. I’ve had them on and off a couple times.

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Sweet! I look forward to seeing it finished and flying 👍
That 2’ extension would make quite a bit increase in wing area.
 

M Clarke

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Sweet! I look forward to seeing it finished and flying 👍
That 2’ extension would make quite a bit increase in wing area.

Wingspan extended 4ft in total. There are some notes in my logs next to the first couple flights saying stall speed was 40mph. Stock Jungster 1 stall speed listed as 55mph. Big difference! Cruise speed was reduced quite a bit as well... Seems like my Jungster was built for a slightly different mission and I don’t think I’ll be doing any hard aerobatics in it but I’ll be happy if it’ll do the occasion loop/roll.
 

Fighting 14

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Hey guys, I found a couple interesting things. First found a neat picture of the Moraine Saulnier which probably inspired RK to design the parasol wing Jungster 2. And I went searching for any info on wing washout. Did not find anything yet specific to the Jungmeister, but I did for the Jungmann. There is no washout built into the Jungman wing panel. Steve Beaver has put together a very outstanding website dedicated to the Buckers, which I will forward in a minute. Meanwhile here is a site with detailed pictures of a large scale RC Jungmeister. https://www.paoloseverin.it/download/files/Bu133Eng.pdf
 

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Fighting 14

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My records show the power off stall on my airplane as 51 mph. Wonder if that small amount of washout helps. Most likely just differences in AS indicators and pitot position.
 

Dominic Eller

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That’s a beautiful model! What a monster scale too.
Here is a nice article on Tony Smiths Jungmeister. It explains the incidence difference it has from most bi planes, being the top wing has a slight negative incidence.
Seems the Jungster plans don’t show an incidence but the info pack front page states top at between 0 and 0.5 deg and bottom at between 1 and 0.5 deg


I’m glad I followed Jerry’s lead and put the adjustment on the cabanes, that coupled with the double landing wires and the adjustable rear strut should give me a fair amount to play with to fine tune her. But that’s a fair way ahead still in my future.
 

Dominic Eller

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Those Saulniers loom great together.
M Clark are you going to get some large decals made to dress yours up like a semi military one? Could look very cool.
 

Dominic Eller

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Not sure if you will be able to read this but here is an article from Sport Aviation mag Jan 1985. I randomly got given a bunch of these many years ago and as I was taking the Jungster 1 to bits I had a feeling I had seen something similar in one of the mags I had been given. Well their was Gene Parker’s D-PRKR Jungster 1.
F 14th did you say your one was one of a few Gene Parker built?
CABC3D0B-F212-4B6C-ABF9-ECED62CE1D68.jpeg 64D800A1-365C-493C-97EF-FC893D92BE54.jpeg 2419C8AB-F391-4CD0-83F7-C323DDB0FC12.jpeg 18BE5191-DA11-44C7-A229-64DC00E5BE5B.jpeg
 

Fighting 14

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Thanks for the article. I worked on the carbon fibre gap strip today. Definitely a learning experience. Here are the takeaways. Taping polyethylene over the gap so as to protect the airplane from the lay-up does not work very well. Using peel ply did not work for me. It will not assume a compound curve of any kind. And just the polyethylene will not support the carbon fibre enough to do a smooth job. What needs to happen is an application of thin stiff cardboard. Not sure how that is going to conform to the bend with the 11 degree sweep at the leading edge. Then cover that with the polyethylene sheeting then do the layup on that. You absolutely need something stiff to lay the carbon fibre on. Bending aluminum is probably faster. Why can't things be easy? Any ideas??
 

Dominic Eller

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Yup things are just never easy ! I just spemt a bunch of time trying to bend some metal to my will using trickey until i tried no tricks and simple...and then it worked :)
for your fairing, yes thinish cardboard or thin and cheap houseold aliminium sheet.
You could try watching a few of Mike Pateys Draco and Scrappy build vids. he does a hell of a lot of carbon and has some pretty neat simple tricks for 1 off parts that dont require making moulds.
 

Fighting 14

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Probably need to make a plug which fits the leading edges. Tape it in place then lay-up over it. For some unknown reason I expected the carbon fiber cloth to be stiffer. It is just like fiber glass cloth. Another trick may be to wet it out on a flat surface and let it get nearly set but still ply-able, then lay it on the wing and shape it. I have the bottom fairings already made out of aluminum and I will use them. I will try pre-pregging the next one and lay it on cardboard taped to the wing. If it is semi stiff I think the leading edge will shape. I hope. Not really wanting to carve leading edge plugs. My wife suggests laying the carbon on the flat portion of the top of the wing then forming the leading edge out of soft aluminum and screwing it over the carbon fiber. Probably easiest to order some aluminum bend it then paint it to match the paint scheme. Like I said, three tries before I get it right. TBC.
 

Dominic Eller

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It’s a never ending labor of love this airplane building lark!
Good luck with fairings.
I did play with some composite structural foam sheet for the seat. It comes in various thickness and forms to compound curves. You can lay it on thin plastic like kitchen film then pour on the epoxy, smooth it in a little then lay another piece of kitchen film over it and roller it for hood coverage.
You can then pick it up and move it around without it sticking to things.
You could of course do this with the carbon too, might help forming it up.
image.jpg image.jpg
 

Dominic Eller

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I finally finished racking up the cabanes 🥳 what a mission !
Just need to tweak the left side bushings a little maybe 1/16 to get the alignment back perfect for the wing attach bolts.
Now I can fabricate the new cockpit crossmember so it sits further forward. C8335221-2315-4F5F-8658-6219397CA08D.jpeg 40BF87EF-367D-4DC8-8AE9-6E1321D4B9DB.jpeg image.jpg
 

flitzerpilot

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It's a common assumption that 'most' biplanes feature positive decalage (upper wing at a higher incidence than the lower). This data is repeated in Darryl Stinton's 'The Design of the Aeroplane', but many biplanes have negative decalage, including the Jungmann and Jungmeister, Hawker Fury, all WW1 Nieuport fighters up to and including the 27, although in the latter case the variation is extreme on what are effectively sesquiplanes. All Flitzer types feature neg decalage except the Z-2 for structural and localised aerodynamic reasons.

Regarding the Bucker series, note that virtually all scale R/C models have been built with incorrect slope on the fine leading edge. A quick assessment of any photograph of a real Bu 131 or 133 in side elevation proves that the fin leading edge is 'almost vertical, not sloping backwards and even the fabulous Severin model includes this mistake. This error has perpetuated from the plans drawn by the late G. A. Cox for Aeromodeller magazine (UK) in the late 1950s and everyone seems to have followed suit.

Positive decalage was used on free-flight scale model biplanes to auto-correct a stall and recover from an upset, but the microsecond of difference between the upper wing and lower wing stalling on a full size biplane under normal control is irrelevant and propeller effects have more impact, especially with large propeller diameters.
 

Fighting 14

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I was able to read the article. Thanks! Dom, how much forward movement of the panel are you able to accomplish? Your cabanes and center section look great. I appreciate the suggestion on forming the fairings, and the decalage explanation is very interesting. I plan to head to the hangar again today and will keep working on the fairings.
 

Fighting 14

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Dom, if you can figure a way to place hand holds in your center section I would do it. You will have an easier time getting in the cockpit, and in the event of a bale out you will have a much easier egress. The lack of anything directly in front of and above you to grab on to makes entry and exit more challenging. I added two bullets on the top of my center section in an attempt to give myself some hand holds. They are not very satisfactory. I would make Stearman type hand holds if I could do it over.
 

Dominic Eller

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I should be able to move the instrument panel forward by about 2”
I’m planning on using the Kanardia Indu round combo instrument which is not very deep, only needing 3” from the front face to the clearance needed for the pitot static lines, so fouling the fuel tank isn’t such an issue as it is with traditional instruments. I think that is what drove the design of the original position of the instrument panel. Even 1 1/2”forward makes a big difference for getting in and out, especially for 6+ footer folks like me. I may even look at bulging the carbon instrument panel around the indu round instrument to allow the cross member to be even further forward and still have enough clearance behind for the Pitot static lines.
The panel I’m planing is going to be super simple, the indu combo will do A/S, Alti, VSI only 210g. The engine monitor “Digi” is about 3/4” deep and 140g, I’ll likely put a back up oil P instrument. Flight data systems GT-50 G meter 85g. A few switches, slip ball and that’s pretty much it. The basic instruments will only total about 435g or less than 15oz.

Re hand holds, the original C section did have them, but by the time it got to NZ they had been covered over. I’ve flip flopped over doing them and not.
I don’t really like the idea of encouraging folks to put force onto the TE, I know it’s strong and lots have them, but looking at pics of the prototype Rim built it doesn’t appear to have them.
So far I’ve used the cabanes for support and or the top longerons.
I’ll keep thinking on it. I’m not keen to have the extra hassle of making the covering look neat and tidy in those compound curve holes either 🙄 , lazy I know !
Flutter vids are interesting.
I was stunned at the amount of free play in the aileron system! Interesting they elected to just limit its speed and not attach counter weights in the end.
 
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Fighting 14

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I agree. I think I would have mass balanced and kept the speed down both if it was remotely possible. What a beautiful airplane and the paint is just spectacular. Back to the handholds. My airplane center section was covered with a foam and fiberglass skin on the top and fabric on the bottom when I bought it. So I did not tackle that and left it alone. But my immediate reaction after flying this one back from Georgia was that the cabanes are too far out board to really help a whole lot at pulling oneself up and out of the seat. I know RK did not include them, but they sure would help. I don't mean to tell you how to build yours, just passing along a suggestion from having gotten in and out a bunch of times without them. The fairing process is going well. The cooling temps are making setup time long. I need to remember to take some electric heaters to the hangar. Looks like a three day process. Day 1 pre-preg the carbon strips. Day 2, trim the edges and lay up on wing covered with polyethylene. Day 3, add a coat of resin and lay on peel ply to create a glassy finish. I think it is going to work out ok. Here are a couple pics of what Day 1 and Day 2 involve. The plastic covered sailplane wing is my handy layup table with built in curve. The second shot shows the trimmed semi-hard piece trimmed and shaped. When it is setup I will add the final coat of resin and peel ply.
 

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