The Janowski Project - Rethinking the J1B/J2/J3

[Hephaestus]

****, I'm not perfect!

Thanks for the edit, I've updated my master. I will wait to see if any more updates com in before revising the attachment.

Nobody expected you to be, went off the translations and went - this doesn't add up. There's a bunch more but I'll have to dig out a red pen and start making notes as I go. But in some ways this is easier.

 

[Mohawk750]

Well the numbers should translate directly...that looked like a copy paste error from trying to save a few key strokes. There are no shortcuts in aviation!

 

[Vigilant1]

I also like the idea of a J1T......BUT......if i can't easily fold the J1B high wing then I prefer the removable wings of the J2.

For compactness and ease of setup, the H-stab on the MC30 has a lot to recommend it. One piece stabilator entirely forward of the fin and rudder. It detaches easily from its pivot and actuator and lifts right off to be stored wherever you want. The looks of it are unconventional and I admit it bugs me, but it is useful, eliminated interference drag with the V-stab, prevents aero shadowing of the rudder in a spin, etc. Unfortunately, if we already have questionable elevator authority with the J-1, moving the H-stab forward relative to the CG might not be good. Maybe mount it entirely aft of the fin and rudder?

 

[Mohawk750]

The MC30 is a great little airplane and the forward position horizontal stab is a very "French" design element. It there such a thing as "regional design" many European aircraft use this configuration.

I think the low stab on the J1 didn't work well so Janowski went to the T-tail on the the J2, the J3 was a one off but I would suspect optimized in many ways. Later designs went to composite and were designed as powered sail planes as well as sport planes and adopted a V-tail, who knows why?

I still think a wood and foam J2 with an all flying V-tail would be an awesome looking machine. These guys seem to think the V-tail is ok....

 

[Hephaestus]

For compactness and ease of setup, the H-stab on the MC30 has a lot to recommend it. One piece stabilator entirely forward of the fin and rudder. It detaches easily from its pivot and actuator and lifts right off to be stored wherever you want. The looks of it are unconventional and I admit it bugs me, but it is useful, eliminated interference drag with the V-stab, prevents aero shadowing of the rudder in a spin, etc. Unfortunately, if we already have questionable elevator authority with the J-1, moving the H-stab forward relative to the CG might not be good. Maybe mount it entirely aft of the fin and rudder?

Effectively the T tail pushes the HStab back anyway. Leading edge of the HStab on the J2 is 75mm behind the end of the fuselage. Pivot for the Hstab is 260mm behind the rear of fuselage (ballpark - scaling off drawings)

I don't see a bunch of pireps on the J2 polonez, I wonder how much of the elevator 'ineffectiveness' is actually the usual high thrust line pusher transition issues.

That said, 640mm thrust line as drawn to boom, maybe a bit of vertical stretch is needed. So would only fit a 48" prop with about an inch to spare. Guessing this is why his later engines moved the engine farther up.

Vtail would effectively put you out in clear air all the way around, that link of the J5 3d model in the RC model section he's got a proper head on view. But maybe this will make it clear too

 

[Vigilant1]

Vtail would effectively put you out in clear air all the way around, that link of the J5 3d model in the RC model section he's got a proper head on view. But maybe this will make it clear too
View attachment 106893

And, by the same token, a T-tail would put the H-stab in the swirling wake of that rear prop all the time.
There's no perfect answer, of course.
Will the plane have flaps, spoilers, or a speedbrake? The very simplest way to add drag for glideslope control is with use of the existing rudder to perform a slip. And the un-mixed, uncompromised yaw control offered by a pure rudder does a very good job of letting us do a forward slip or maintain runway alignment in a crosswind TO or landing.

 

[Hephaestus]

And, by the same token, a T-tail would put the H-stab in the swirling wake of that rear prop all the time.
There's no perfect answer, of course.
Will the plane have flaps, spoilers, or a speedbrake? The very simplest way to add drag for glideslope control is with use of the existing rudder to perform a slip. And the un-mixed, uncompromised yaw control offered by a pure rudder does a very good job of letting us do a forward slip or maintain runway alignment in a crosswind TO or landing.

Yep, for now, I'm just slowly modeling my way through as is. I think as it sits it's worthy of further examination. But really as is it's not very buildable.

So as is - no flaps/spoilers/speedbrake. That said - it's a 1 banana job if you've gone to a standard gear hoop to add a belly board to a flat bottomed aircraft.

I'm no Rutan/Roncz, if there's specifics about the aircraft aero that's verifiably wrong (not just opinion/changes to make changes) - Well like I said, I'm having v2 thoughts as I wont fit in the original. But that comes later...

 

[David L. Downey]

View attachment 106851
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.

Comment probably not needed and possibly not appreciated . But this is not the result of a bad t-square or drafting machine! this is usually the consequence of scanning; the output data gets skewed a little. also not that the "X" and "Y" scales are very frequently not the same - even possible/likely that the paper original was not X+Y.
When I am doing what you are showiing the image, I like to start with a fresh greyscale scan TIF at 200dpi and fine rotate it until one or more major lines known to fall on the "X" axis are indeed at the same pixel count in the "Y" axis. then i simply use pixel count and calculate X and Y scale factors. find several dimensioned values in each axis and use some type of consensus value for each axis. use the pixel count and scale factor to get the dimension of interest.

 

[David L. Downey]

You're challenging me - 7 laminations of 7x20x4000mm spruce was called for in one drawing of the longerons - might have been the j1b too I was eyeballing them as well. Can't place it right now. So ¾x1⅞ yup I can't math anymore



I can believe it

well, as a sobering reality check, give that task to virtually ANY USA high school student and look at the result - if there is even a result! What we have done to our young people is criminal. many completely useless skills and very few critical skills...and oh, but the way, they also long for that sheepskin (to keep warm with maybe?)

 

[Aerowerx]

We are in fact both correct A/B/C cross sections don't show it, but it shows in the section views for the bulkheads and other details.

Not sure, why I'd asked if someone had backed up the Janowski group somewhere, probably a ton of details in there that are now lost to the ages.

Not the entire group, but I have a bunch of files I saved. Mostly on the J-1B.

I also merged all the J-2 PDF drawings into a single file.

 

[Aerowerx]

As for the elevator authority...

If you use the standard cookbook formula for tail volume, you will find that the J-1B is lower than the typical acceptable value. Hence the need to lengthen the tail by 10 or 12 inches.

As for the guerney flap, I don't know if that is because of the low tail volume or something else. I also recall that it was recommended to seal the gap between elevator and H-stab. I would conjecture that with the lower tail volume any design flaws in the elevator would be magnified??

 

[Mohawk750]

Aerowerx;

I seem to recall there was an issue with the J1B main wing angle of incidence as well. Whether the plans have errors or are just not clear on the subject I can't remember but it was discussed on the Yahoo groups years back. Do you have any info?

 

[BJC]

I would love to see a modern iteration of the -1B, -2, or -3 in fiberglass, using the "fold-a-plane" concept, and up-sized for large pilots and the HKS or O-100 engine.


BJC

 

[Hephaestus]

Comment probably not needed and possibly not appreciated . But this is not the result of a bad t-square or drafting machine!

Well working from what we have, yes imported over a large block (easiest way I've found in fusion) ballpark then fine tune, but - haven't run into scaling differences between X and Y so far.

Working with what I've got, take a look at the pic I I threw out to show the inner ply layer around the fuse formers/bulkheads. If you've got 2 groups of squares side by side at different angles, and the lines aren't square or parallel... (Yes I realize thats the rear spar attach, and there's 2deg of dihedral in there on the right one)

Quality seems to vary page to page, so that's why I'm betting - one or more of those T squares have a wobble or just user who didn't give a crap. The airfoil plots are pretty impressive - I remember trying one in HS drafting and getting frustrated as hell.

If you use the standard cookbook formula for tail volume, you will find that the J-1B is lower than the typical acceptable value. Hence the need to lengthen the tail by 10 or 12 inches.

I was thinking of working through the data and trying to get it all into the Roncz spreadsheets later and see how the sizing ballparks look in there.

KR2 before the big stretching trend started, they often increased the Hstab span to get a bit more authority. But I think as drawn might be the starting point.

I seem to recall there was an issue with the J1B main wing angle of incidence as well. Whether the plans have errors or are just not clear on the subject I can't remember but it was discussed on the Yahoo groups years back. Do you have any info?

Haven't looked into the J1B as much (Yeah I prefer my wings below) on the J2 it's definitely a 23015 at +5deg Wing attach are all leaned to match. So at least on the plans I'm working with that's clear

I would love to see a modern iteration of the -1B, -2, or -3 in fiberglass, using the "fold-a-plane" concept, and up-sized for large pilots and the HKS or O-100 engine.

I think you and me are on the same page Other than the engine. There's a possible wing fold option kitfox style.

 

[Riggerrob]

J1 wings would fold easiest if they fold straight back like a Kitfox.
OTOH if you fold wings leading edge downwards, they can lay flat along the aft fuselage.

My preference would be for a low-wing, with the pivot point near the rear spar. Remove flight lock pins from inside the fuselage, pull the entire wing outboard, rotate it leading edge up, then swing wings back and (ground only) pin them to the vertical stabilizer(s). Control cables or rods need to be routed near the rear spar, because that simplifies quick-disconnect fittings. Ideally, control runs automatically re-connect themselves every time you spread the wings. Stowing wings nose up helps reduce the amount of rain, ice, snow and bird poop accumulating inside wings.

Modern competition sailplanes have T-tails because they are high enough to stay out of the weeds. T-tails also reduce parts count when dis-assembling. An earlier generation of sailplanes had V-tails for similar reasons. I would prefer a Janowski-style airplane to have a V-tail because it reduces parts count on a tiny airplane.

 

[Hephaestus]

Ribs done, other than the aileron, I need to get farther into the spar drawings to get that one sorted out.


They wouldn't be particularly cheap in this day and age. As drawn those top ribs (x12):
~8' of 5x7mm spruce each (2355mm with 0 waste)
2x4' sheet of 1/32nd ply (0.8mm) for every 2 ribs (laser cut you might be able to get almost 3)

J1 wings would fold easiest if they fold straight back like a Kitfox.
OTOH if you fold wings leading edge downwards, they can lay flat along the aft fuselage.

might touch the ground in the original drawn bicycle gear. But they do fit in the space beneath the HStab.

 

[Aerowerx]

Aerowerx;

I seem to recall there was an issue with the J1B main wing angle of incidence as well. Whether the plans have errors or are just not clear on the subject I can't remember but it was discussed on the Yahoo groups years back. Do you have any info?

I remember puzzling over that and finally got it figured out. I don't remember the details, but I recall that the AoA should be 6 degrees referenced to the Chord Line.

Also, the side view on Drawing 2 indicates that there is angle between the ribs and the bulkhead. But the rib profile in Drawing 6 has the spar cutout at a 90 degree angle. Anyone doing a redraw of the plans should keep that in mind.

Just remembered. There was someone in France that took on the project of redrawing the whole thing in a 3D cad program. That the J-2, I recall. Can't remember who it was, and I think it was on the defunct Yahoo group anyway.

 

[Mohawk750]

J1 wings would fold easiest if they fold straight back like a Kitfox.
OTOH if you fold wings leading edge downwards, they can lay flat along the aft fuselage.

I would prefer a Janowski-style airplane to have a V-tail because it reduces parts count on a tiny airplane.

Another Canadian that likes folding wings and V-tails !! must be the rarefied arctic air up here. 6" of snow in Ottawa last night. The Kitfox style wing fold would work best on a J1T and tuck them right in under the stab. You will have to add flaps just so you have a surface that you can disconnect and fold out of the way.

 

[Mohawk750]

Ribs done, other than the aileron, I need to get farther into the spar drawings to get that one sorted out.

Keep up the good work, these renders are looking pretty good

They wouldn't be particularly cheap in this day and age. As drawn those top ribs (x12):
~8' of 5x7mm spruce each (2355mm with 0 waste)
2x4' sheet of 1/32nd ply (0.8mm) for every 2 ribs (laser cut you might be able to get almost 3)

Ya, those ribs look plenty strong but heavy, easy to build compared to stick ribs though. What about doing a J2 wing with LE ribs in XPS foam and plywood D-section to the spar. Rear ribs in XPS foam with ply capstrips. Root rib and ribs on each side of the aileron bay with ply skin on one side for stifness and fabric cover?

 

[Mohawk750]

Also, the side view on Drawing 2 indicates that there is angle between the ribs and the bulkhead. But the rib profile in Drawing 6 has the spar cutout at a 90 degree angle. Anyone doing a redraw of the plans should keep that in mind.

I only mention this so it doesn't get lost. Redrawing the plans would find the inconsistancies.

Just remembered. There was someone in France that took on the project of redrawing the whole thing in a 3D cad program. That the J-2, I recall. Can't remember who it was, and I think it was on the defunct Yahoo group anyway.

Sure would be nice to find this guy and get a CAD copy of these plans....but then Hephaestus would have nothing to practice SW on!