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The Janowski Project - Rethinking the J1B/J2/J3

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Aerowerx

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.... The foam and ply sandwich fuselage pod could be caged by with a rollover structure for a windshield frame and a side door instead of canopy and reinforced with carbon if needed.....
IIRC, the original J-1(not the J-1B) had a steel cage around the seat and pylon.
 

Hephaestus

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Everyone says the J1/J2 is overbuilt but nobody has figured out where all that extra weight is yet.
Well we know there's a fair bit in the wing ribs on the J2, J1B is better in stick built form - just straight up comparing against say the minimax. Not sure why the major laminations of plywood. When on the bigger j1b it shows the more typical plywood gussets. Thicker wood / more reinforced throughout.

Applies throughout the structure, he uses those big planks of 1/1.5mm ply extensively in the vstab/rudder/hstab as reinforcement.

Can I analyze all the flight loads - nope not there yet. Got through the J2s spar loads, seems to follow the old ww2 naca era chart method for sizing spars - not exactly to current norms. I wasn't expecting it to, but hoped for a bit more - and 450lbs seems like the designed MTOW/MAUW, wouldn't push that much you might already be in FOS territory.
 

Tiger Tim

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A couple thoughts that I think would build excitement around this thing like crazy: could us mere mortals make a near indestructible carbon F1-style cockpit tub in our garages, and could it be amphibious? I suspect both would water down the point of this and drag it into some design-by-committee monster that nobody really wants, though. Still, a guy can daydream...
 

Vigilant1

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A couple thoughts that I think would build excitement around this thing like crazy: could us mere mortals make a near indestructible carbon F1-style cockpit tub in our garages, and could it be amphibious? I suspect both would water down the point of this and drag it into some design-by-committee monster that nobody really wants, though. Still, a guy can daydream...
Amphib would probably be a tall order. But I think a very strong CF pod might be practical. My first look would be at those glider keel beams and compare that to a more monocoque approach using sandwich panels with CF corrugation/web in place of foam/Nomex. Anything of this type is going to be heavier than the structure needed to handle flight loads alone, but maybe not so heavy as to be impractical. Maybe...
 

Hephaestus

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A couple thoughts that I think would build excitement around this thing like crazy: could us mere mortals make a near indestructible carbon F1-style cockpit tub in our garages, and could it be amphibious? I suspect both would water down the point of this and drag it into some design-by-committee monster that nobody really wants, though. Still, a guy can daydream...
images (1).jpg

Gotta admit I have looked up some details on the aventura / bucaneer ULs while trying to figure things out on the J2. Sure looks like a J1 with more fabric.

Not my cup of tea at the moment, but tweaking lower longeron, and adding a step shouldn't be impossibly hard I'd imagine. I don't even want to start thinking about water loads though ;)
 

Mohawk750

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Buccaneer is a great looking airplane and if I lived on a lake I would definitely be looking at something like this. Sadly waterfront property where I live is at stratospheric prices and in high demand just like the cost of hangar construction and lot lease at local airports it's out of reach at the moment.

To be practical for me I need to either tie down outside for the summer or share some hangar space. The ability to fold/remove wings and trailer home for winter storage or maintenance upgrades means I'm more likely to be able to afford it and keep it in good shape.

On the other hand, it's five years to retirement and we've always dreamed of a palce on the water so maybe some day........
 

Hephaestus

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Yeah, I'm not really entertaining playing with the J1 or amphibian right now. Maybe if I decide belize is a great winter retreat option that'll change :)

Hunting around for some anisotropic FEA software that'll let me compare CF/FG structures against Spruce/Ply, that doesn't cost 5k$/yr. Then there's a huge learning curve, both on structures and the software to learn.
 
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Ried

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FWIW, while I was looking for something else I ran across a J-1B Builders Manual. I assume this dates from the 1980s when plans were translated to English for sale in the USA. I have not studied it, but there is a list of plywood skin sizes for different areas, thicknesses of 1.5 mm, 2.0 mm, and 2.5 mm.
 

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Mohawk750

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FWIW, while I was looking for something else I ran across a J-1B Builders Manual. I assume this dates from the 1980s when plans were translated to English for sale in the USA. I have not studied it, but there is a list of plywood skin sizes for different areas, thicknesses of 1.5 mm, 2.0 mm, and 2.5 mm.
Thank you for the contribution! I have not previously seen this, good stuff 👍
 

Aerowerx

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FWIW, while I was looking for something else I ran across a J-1B Builders Manual. I assume this dates from the 1980s when plans were translated to English for sale in the USA. I have not studied it, but there is a list of plywood skin sizes for different areas, thicknesses of 1.5 mm, 2.0 mm, and 2.5 mm.
The builder's manual was never finished, as I recall.

Also, I believe there was some disagreement over the right to distribute plans. Whoever did the build manual and was distributing the plans did not have permission.
 

Ried

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The builder's manual was never finished, as I recall.

Also, I believe there was some disagreement over the right to distribute plans. Whoever did the build manual and was distributing the plans did not have permission.
Aerowerx,
That sounds right. This is more of a parts list than a builders manual. Definitely not a complete manual.

I was surprised to note 2.5 mm ply in some locations. I don't recall seeing that on any plan set.
Thanks
Ried
 

Hephaestus

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40 years ago metric ply was relatively unheard of in the NA market... Even 3/32nd - closest fraction would be tough to find (outside rc hobbyshops).

Probably why there's so few flying - wondering what those that were built actually used in north american builds.
 

Aerowerx

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The construction manual I have has only 29 pages. It only goes as far as building the fuselage sides, and I see that it references drawings which are not existant (unless they refer to the original drawings).

Now that I think about it, I seem to recall that the problem was that the creator of the manual was going to sell a parts kit. Janowski objected and the idea was dropped.
 

Aerowerx

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40 years ago metric ply was relatively unheard of in the NA market... Even 3/32nd - closest fraction would be tough to find (outside rc hobbyshops).

Probably why there's so few flying - wondering what those that were built actually used in north american builds.
I remember looking into that problem and found that, given the tolerances on the thickness of aircraft plywood, there was overlap between the metric and equivalent USA plywood. My opinion is that you could use the closest USA plywood if you can't find the metric, but you may have to do some "cut and fit" trimming.
 

Hephaestus

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Pondering monocoque fuselage at the moment. Typical composite construction - 2 fuselage halves, join at center. I mean it's 2 big 1-off female molds to build - but nearly all flat surfaces seems smarter than the alternatives as long as it doesn't get super heavy
 

BJC

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Pondering monocoque fuselage at the moment. Typical composite construction - 2 fuselage halves, join at center. I mean it's 2 big 1-off female molds to build - but nearly all flat surfaces seems smarter than the alternatives as long as it doesn't get super heavy
If you are thinking about composite construction (a la the J-5 and -6), consider a mold for a “tub” or “canoe” like fuselage, where the fuselage bottom and both sides are done in a single piece. That will make system installation much easier and quicker.


BJC
 

Hephaestus

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Don't mind me, just dropping this here so I can find it later. Thinking this might work nice on my revised version.

 
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