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The Janowski Project - Rethinking the J1B/J2/J3

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Mohawk750

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Ok folks, This is a new thread dedicated to the designs of Jaroslow Janowski whom I have never met but have grown to respect through the study of his life's work in designing a series of small aircraft that have universal appeal and have been copied time and again in the ultralight world. For anyone not familiar with the J series aircraft I have written a brief history of the designs.

I have also now spent over 25 to complete and verifying my translation of the Janowski J2 Polenez plans set. I've done this with the benefit of google translate, reference to the J1B plans and 30 plus years experience working in aviation. I am posting this now for anyone to download to assist in the study of the J2 plans set. I know The J1B and J2 plans have been posted before but I will re-post my copies, which may be better quality here so everything is in one place.

I invite you let your imaginations run wild with the only expectation that we rekindle interest in this series of light aircraft.
 

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Hephaestus

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J2 to J3 differences -
Conventional landing gear, wortman laminar airfoil, and added spoilers.

Cockpit lines seem a little smoother.

I don't suppose anyone archived the Yahoo group before it died? I don't see any reference to it being moved to groups.io or anything.
 

Mohawk750

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Well that's a good question. Since only one was ever built we would have to compare the J3 in Poland to the J2 plans we have on hand. From pictures I can see a few obvious differences and from various articles and web sources some information is stated but would have to be validated.

1) J2 engine mounts in a notch on the back of the pylon, J3 engine appears to be mounted on top.

2) J2 stabilator plans have two counterweight booms and the J3 pictures show one in the center.

3) J2 plans are mono-wheel, J3 is conventional gear. (Pictures show J2's have been pictured with conventional gear)

4) The J2 is rather short coupled but pictures of the J3 would seem to suggest a little more length in the boom.

5) The J2 has a flat bottom but the J3 has a center belly stringer which gives the bottom some more contour.

5) J2 wing span 7.6m (~26') and the J3 in 7m (~23')

6) J2 uses 1/4 span ailerons, J3 full span ailerons that may actually be flaperons.

7) J2 uses a NACA 23015 airfoil and the J3 has been reported as a Wortman.

This is great info if a person wanted to create a J2 or try to recreate the J3 but as I have stated in one of the other threads there would likely be enough deviation in a build today that it would essentially be a new design. That's kinda the point of this project, re-think the J series.

I believe it would be possible to build a J3-ish UL utilizing lots of foam and wood and 2X engine to get to Part 103 weight but the aircraft would seriously out perform Part 103 numbers. You would have to put a draggy high lift wing on it to make stall and keep cruise down and that kinda ruins the idea for me.

Originally I thought I wanted to recreate the J3 just because it is so rare and unique but the J1T idea is growing on me. If you forget about Part 103 your options really open up and for me here in Canada Part 103 is irrelevant anyway. So what about a J1 based design with the J2 T-tail? Ideally for me I would want it just a little bit bigger in the cockpit to suit "full sized" pilots, a little bit longer to address the short coupling and a folding single strut wing for storage and transport. If it is a little bigger and stronger you can use the larger VW engines or 4X snowmobile conversions to get the 60-80hp needed.
 

Vigilant1

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With the relatively cheap and readily available CF pultrusion rods available now (and not when the J-1 was designed) I'd think a full cantilever wing of the later J birds is preferable to strutted J-1 approach for an updated design. And, a low wing shortens the load paths in the fuselage (the wing spar and landing gear attachment points will be close).
Construction material? I like Boku's little CarbonMax project's ideas a lot. A little semi-monocoque fuselage with a CF skin and CF-over-foam stiffeners/longerons could be laid up in some very simple female molds if we are okay with something other than compound curves. Use almost flat sheets to make a curved pod with corners that meet at slightly obtuse edges (like the early Janowski canopies). Female molds formed with cut curved sheets of AL trim coil from Home Depot in plywood cradles to define the shape.
 
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Aerowerx

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With the relatively cheap and readily available CF pultrusion rods available now (and not when the J-1 was designed) I'd think a full cantilever wing of the later J birds is preferable to strutted J-1 approach for an updated design.......
I once visited a builder over near Akron Ohio. He used to be a member here (Carribeanbound????) and was building a glass/foam sandwich J-1B. Never heard if he finished or not. Last I heard is that he moved back to Florida.

Anyway, he told me that he had an engineer look at the original design and was told that it was over built. Probably because 1970s Communist Poland did not have a Aircraft Spruce outlet, and he had to use what was available.

So there is certainly room for improvement with modern materials.
 

Riggerrob

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What if you combined Janowski's configuration with the simplified construction of the Monnet Monerai glider?
Monnet's cockpit is built almost the same way as Janowski's later designs, but he simplified tail boom construction by using an aluminum tube. Monnet also displaced the V-tails slightly to make them easier to install.
Monnet's other advantage is that his aluminum skins on flying surfaces can be built without elaborate female molds.

Finally, if you add a bit of conical curvature to the windshield, you can omit fancy molded canopies and just use a flat sheet of plexiglass. Working from flat sheets is most valuable when you are building at the far end of a long shipping route. For example, a Canadian friend ordered a canopy from Monnet, but it arrived cracked. Canada Customs still insisted on him paying all the taxes and import duties. GRRRRRRR!
 

Vigilant1

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Monnet's other advantage is that his aluminum skins on flying surfaces can be built without elaborate female molds.
That could work, but (in part due to the Moni experience) there would be a lot of reluctance to depend on bonding aluminum for structural use in a homebuilt environment. If we're back to thousands of rivets, that will be another challenge.
Finally, if you add a bit of conical curvature to the windshield, you can omit fancy molded canopies and just use a flat sheet of plexiglass.
The early Janowski canopies used flat panels, they look good IMO. Yes, a conical flat wrap windscreen is also a possibility (Sonex does it), but the junction where the windscreen meets the overhead is a source of much builder frustration. Folks always eventually get it, but it seems to be one of those things that is easily drawn but can be tricky to fabricate.
 
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Mohawk750

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I know virtually nothing about composite primary structures and even less about carbon fiber used for structural purposes. All my composite experience has been with secondary structure, wing root fairings, wing tips etc. Those just need to be light and sturdy so almost anything works.

However the talk above about the Carbon Max project had me go and read a bunch in that thread. That, and I've always liked the look of V-tails and a full flying V-tail with only two control surfaces could really reduce the parts count.

Before we get into a debate about the virtues of a V-tail aircraft I do understand the necessity for equal tail volume to conventional tails and the need for a mixer and the fact that there is very little performance advantage and there can even be some odd dutch roll tendencies etc. Let's just agree for the sake of interest that it has been done on several aircraft and it works, Monnet's Moni and Leon Davis's designs are good examples.

So now we can envision a sort of flat sided J5/J6 derivative suitable for homebuilding. The fuselage could take on a sort of trapezoidal cross section with the widest point being a joggle joint at the upper longeron. The fuselage is constructed in a female mold build from bulkheads, formers and lined with tin sheet and nice fat radius corner from resin and micro balloons. You lay in the carbon with the proper orientation and let cure, an additional core could be added and sandwhuchd where needed, cabin floor, gear area etc. Add some bulkheads and close the tail boom with a top cap that bonds at the joggle. Add a pylon encolsure and bulkheads, canopy frame and nose cover in separate pieces. The V-tail could employ a carbon fiber tube spar, solid XPS foam core and carbon wrap. Main wing with leading edge D-cell formend in a similar manner and carbon rod sparcape with foam or carbon rear ribs. If you wanted you could attach the whole works to a 4130 welded space frame that ties in the cockpit, landing gear, shoulder wing mount and engine mount hard points. No new ideas here except working with carbon at home.

Downsides are allot of time building molds for single use and the builder needs to learn composites and welding and you'll spend the rest of your life debating the merits of V-tails but hey, it looks cool!😁
 

Vigilant1

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Landing gear? If we're gonna open the V-tail can-o-worms, we might as well have all the arguments at once. :)
"Welding is easy, everyone should love it. Better than yoga."
" Monowheel, or you are just an idiot."
Etc.
 

Hephaestus

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Well the J1 and J2 are built a bit beefy yes. 1½x1¼ longerons with 2mm ply inside and out, spars same basic ballpark as a bunch of other vw / 2place designs. Seems to be a fairly standard method for a few larger vw powered designs.

If one wanted to take it on as a design project - it's a nice base, proven, multiple construction material options.

Wish carribeanbound had checked in.

About the only thing I'd change - is the landing gear. Bit more nose, simple nose gear for a tricycle gear, as much as many hate them... oh and a front hinge on the canopy.
 

Jimboagogo

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Well that's a good question. Since only one was ever built we would have to compare the J3 in Poland to the J2 plans we have on hand. From pictures I can see a few obvious differences and from various articles and web sources some information is stated but would have to be validated.

1) J2 engine mounts in a notch on the back of the pylon, J3 engine appears to be mounted on top.

2) J2 stabilator plans have two counterweight booms and the J3 pictures show one in the center.

3) J2 plans are mono-wheel, J3 is conventional gear. (Pictures show J2's have been pictured with conventional gear)

4) The J2 is rather short coupled but pictures of the J3 would seem to suggest a little more length in the boom.

5) The J2 has a flat bottom but the J3 has a center belly stringer which gives the bottom some more contour.

5) J2 wing span 7.6m (~26') and the J3 in 7m (~23')

6) J2 uses 1/4 span ailerons, J3 full span ailerons that may actually be flaperons.

7) J2 uses a NACA 23015 airfoil and the J3 has been reported as a Wortman.

This is great info if a person wanted to create a J2 or try to recreate the J3 but as I have stated in one of the other threads there would likely be enough deviation in a build today that it would essentially be a new design. That's kinda the point of this project, re-think the J series.

I believe it would be possible to build a J3-ish UL utilizing lots of foam and wood and 2X engine to get to Part 103 weight but the aircraft would seriously out perform Part 103 numbers. You would have to put a draggy high lift wing on it to make stall and keep cruise down and that kinda ruins the idea for me.

Originally I thought I wanted to recreate the J3 just because it is so rare and unique but the J1T idea is growing on me. If you forget about Part 103 your options really open up and for me here in Canada Part 103 is irrelevant anyway. So what about a J1 based design with the J2 T-tail? Ideally for me I would want it just a little bit bigger in the cockpit to suit "full sized" pilots, a little bit longer to address the short coupling and a folding single strut wing for storage and transport. If it is a little bigger and stronger you can use the larger VW engines or 4X snowmobile conversions to get the 60-80hp needed.
I love the J1B and often thought of building one. It seems very economical particularly substituting Western Hemlock or Douglas Fir for the spruce. I would use a combination of both in all likelihood. 60-80 hp sounds like a lot, but I'm a lightweight at 165 or so on a good day. I might have to add ballast! Lol. Good luck and good building! Our EAA chapter 63 might have instruments to help you out. We have a few spares from our Emeraude project.
 

Mohawk750

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About the only thing I'd change - is the landing gear. Bit more nose, simple nose gear for a tricycle gear, as much as many hate them... oh and a front hinge on the canopy.
A nose gear would sit right under the rudder pedals you could put a rudder bar right on top with a cable each end heading to rudder. Use heal brakes and you've just reduced the parts count. Main gear would have to move back to near the main spar spar position which would concentrate the loads in one structural area.

Good luck and good building! Our EAA chapter 63 might have instruments to help you out. We have a few spares from our Emeraude project.
I'm not ready to build just yet but I'm weighing my options. There is allot to like about the J series and it's good to hear that they are strongly built.
 

Jimboagogo

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Canopy hinge location is always a tradeoff. Side hinge is common on several aircraft including the ASSO 4 Whisky I bought plans for. It's strong and looks ok. Front hinge is necessarily weaker but you could support it with a lift strut from a hatchback or something. Could make a sliding forward canopy on the J1B, or any of the series. That would be interesting!
 

Hephaestus

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J2-rear-question.png
Since I'm bored... FYI - These plans were definitely made in the analog era :) And someone needed a better T-square.

J2 plans page 6 - fuselage view, this is the plan view top down of the fuselage profile @ the tail... Think that's a 160? Scales out to 170, but I can't find another detail on the plan with this width.
 

Aerowerx

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..... Could make a sliding forward canopy on the J1B, or any of the series. That would be interesting!
Except the sides are curved in that area of the cockpit. It would take a bit of hard thinking to use a sliding canopy, and add complexity and weight.
 
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