The Janowski Project - Rethinking the J1B/J2/J3

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Michael Silvius

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Good question though. I have bits and pieces from the site. There is a question on having enough elevator authority at landing. A gurney-flap was discussed, but its not an ideal solution. Some think the aft fuselage should be longer. Maybe 12" longer? Also group discussions on dimensional inconsistencies.
It is an interesting design, but it does need to be carefully reviewed and adjusted before building, I believe.
FWIW I was the alternate moderator for the now defunct Yahoo Janowski group.
My friend Alejandro Zapata of Badajoz, Spain is the builder and pilot of EC-ZKB
He powerd it with a modified VW engine of approximately 50 hp. When he first flew his example he could not get it to rotate out of ground effect when at full power. His tecnical advisor then sugested several modification which he implemented.
1) 1cm high gurney flap on the entire span of the underside of the trailing edge of the elevator
2) sealing the gap between the elevator and horizontal stabilizer.
3) lengthening the main landing gear by approximately 15 cm
4 ) lowering the engine thrust line back to the original defined in the plans
With these modifications he corrected the problem and he reports the plane to be docile and well behaved.

AAE 2009 058-1.jpg

Alejandro EC-ZKB (6).jpg

Gurney flap.jpg

gap seal.jpg

AAE1.jpg
 

Vigilant1

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I think it is a 1mm thick strip laminated to the inside of the skin (top and bottom? Just top?) centered between two ribs of the nose.
. . . . And seems like a royal nightmare to install / would make wrapping the Dtube a lot harder - unless you applied it while it was halfway wrapped?
When I look at the plans, it lists that 16 of those strips are needed. There are 8 rib bays per wing side, so I think that means these strips only go under the top skin of the nose (not top and bottom). Yeah, I guess you'd wrap the ply around the top side, reach a paw in there and stick the stiffeners in, clamp everything and let it set, then complete the underside of the wrap ending at the underside of the spar. That's all assuming there's not something >else< that needs to be installed on the lower skin that can only be reached through the top.

OTOH, we have this from this page on the J2 construction:

The leading edge made of pine slat. The main box girder from pine strips is glued with 1.5 mm plywood. Between the lower and upper girders of the spar, in the place of the main fittings, fillers were filled with multilayer plywood. 5 mm thick pine strips are glued in places corresponding to the spacing of the ribs. Aileron girder in a C-section sash, made of pine slats with a 1 mm plywood strip glued on. Ribs made as a two-part truss made of 5 x 7 mm pine slats. On both sides along the upper and lower side members of the rib, stiffening walls of plywood 1 mm are glued. The trailing edge made of a pine slat with a triangular cross-section, is covered on both sides with 1 mm plywood overlapping the ribs. The part of the wing covered with 1.5 mm plywood, on the remaining plywood l mm, forms a caisson working on twisting. The caisson is covered with a glass-epoxy laminate.
Honestly, I don't see those inter-rib reinforcing strips mentioned in the above description at all.
 

Vigilant1

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FWIW I was the alternate moderator for the now defunct Yahoo Janowski group.
My friend Alejandro Zapata of Badajoz, Spain is the builder and pilot of EC-ZKB
Hello, Michael! Thanks a lot for the information and pictures. Have you posted elsewhere here about Alejandro's J-1B?
 

Mohawk750

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That wing render looks fantastic to me.....I don't have access to any CAD type programs at the moment. I used to have an old copy of Autocad that I taught myself to use well enough to get the conceptual design for a house renovation down. I gave the files to "real" designer and they turned them into drawings that were used for my permits etc.

I spent my evening tonight on the openVSP ground school site just trying to figure out if I even want to learn that! I have lots of ideas that I would just like to explore, most wouldn't likely get beyond the conceptual design stage but I'd like to try.

Thanks to everyone who is contributing to the thread! We are really digging up some "gold" now on the J-series particularly the google drive files, great new renderings and pictures and feedback on real flying aircraft. 👍
 

Hephaestus

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FWIW I was the alternate moderator for the now defunct Yahoo Janowski group.
I don't suppose there's a way for you guys to access the group and export the data? Or is it all long gone now?

ZKB looks fun, how's it perform? We lack pireps on the Janowski's ;)

Honestly, I don't see those inter-rib reinforcing strips mentioned in the above description at all.
I think that's J1(b?) instructions... A quick cursory look says - the words don't match the parts/sizes.
 

Vigilant1

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I think that's J1(b?) instructions... A quick cursory look says - the words don't match the parts/sizes.
It's hard to say, the document appears to be a rough machine translation of some kind. But the title of the page is "J2" and the lead sentence of this paragraph is:
"Single-seat, self-supporting, medium-wing wooden structure."
Later there is something that may be reference to a "T" tail.

It is hard to know wat to make of that reference, just based on the mechanics--some minor points are discussed in detail, but nothing mentioned about the H-stab at all.
 

Hephaestus

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It's hard to say, the document appears to be a rough machine translation of some kind. But the title of the page is "J2" and the lead sentence of this paragraph is:
"Single-seat, self-supporting, medium-wing wooden structure."
Later there is something that may be reference to a "T" tail.

It is hard to know wat to make of that reference, just based on the mechanics--some minor points are discussed in detail, but nothing mentioned about the H-stab at all.
Yeah, I keyed onto 4 ribs in the Vstab - I was just drawing the J2's 3 ribs ;)

Similarities yes, details not as much. I think half these plan scammers just copy / paste whatever they can find to make it look complete whether it belongs there or not.

J1b-4ribs.png
 
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Lendo

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I don't know about the brands mentioned but I am led to believe that Marine Plywood can be used in Firewalls, as Marine plywood is tested in Immersion and the Aviation Plywood is test under steam conditions. To me that suggests there is little difference in quality for what your using it for.
However please confirm this for yourself, I'm going by past advice from a Plans Built designer.
Hope that helps
George
 

Micha

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I've been browsing this forum in passive manner for some time, please forgive me posting without separate introduction. Polish is my native language and I do know a bit of engineering "branch" of English so maybe I'd be helpful when Google Translate fails?
Michal from Lodz, Poland - the city of Mr Janowski ;)
 

Vigilant1

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Micha, thanks very much for the generous offer. I hope we won't make you sorry that you made it!

"Welcome to the HBA board." Or, as Google translate would say:

Wsparcie! Moja stopa utknęła w tosterze.
 
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Michael Silvius

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Michael Silvius

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I don't suppose there's a way for you guys to access the group and export the data? Or is it all long gone now?
Owen Strawn was the owner of the group. He gave me alternate moderator powers as I was translating messages from Alejandro who was the only builder/pilot to successfully fly one of these available to the forum members. It had been pretty quiet for a couple years there before it was shut down. Beyond that I have no knowledge regarding the forum or how to save the messages or files.
 

Bill-Higdon

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Owen Strawn was the owner of the group. He gave me alternate moderator powers as I was translating messages from Alejandro who was the only builder/pilot to successfully fly one of these available to the forum members. It had been pretty quiet for a couple years there before it was shut down. Beyond that I have no knowledge regarding the forum or how to save the messages or files.
Sadly all of the information on the Yahoo groups that wasn't saved prior to Verizon shutting them down has gone to the "Great Bit Bucket in the SKY".

Michael wasn't there a fatal crash where the builder didn't follow Alejandro's suggestions?
 

Mohawk750

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I've been browsing this forum in passive manner for some time, please forgive me posting without separate introduction. Polish is my native language and I do know a bit of engineering "branch" of English so maybe I'd be helpful when Google Translate fails?
Michal from Lodz, Poland - the city of Mr Janowski ;)
Micha, thank you for the kind offer. I am the original poster and translator of the J2 materials list. All of the files I worked with are in post #1. If you would like to review the translation I could send it to you in MSword format so you can mark it up and I would be happy to incorporate your edits in a future revision.

Welcome to the board!
 

Hephaestus

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Spars.png

Trying to get through some math today...

So we do really have 2 spars... That 18x58 poplar nose gets attached with 3 bolts on each side, Laminates to a fairly substantial hunk of Spruce (that would be the cherry colored piece). Hoping it's not really being used as a spar, but 3 attachment bolts makes me think - probably is.

So we start following billski's beam formula's.
Total Lift = (weight/2)*(Gs)*(FOS)
so that works out to (650/2)*6*1.5 = 2925lbs

OmegaR = (4*2925)/(Pi*114) = 32.67lb/in

Lift distribution per aeolus says
Lift-Distribution.png
So that kind of checks out - fairly elliptical. Still not totally sure on this - feels like there should be some washout in the wing but no reference that I can find so far. Not that it makes a huge difference to calculating the spar in this case.

So our root moment works out to 112,000 in-lbs and shear works out to 2293 lbs.

Now to find a walkthrough on calculating spruce/ply box spars for a cantilever wing... Or hopefully a spreadsheet setup to do it already :)
 

Hephaestus

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Moment and Shear Spar Calcs.png
Since I'm a visual guy... So this is 650lbs MTOW, Using 6g's and a 1.5 FOS. (Yes this makes more sense to my brain than the straight excel data that's upside down.

So if I'm extrapolating right, I need to look at each of those stations whether the Spar cross section is greater than the Moment / Shear.

Now I need to find a step by step description on how to do that :)
 

Micha

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Micha, thank you for the kind offer. I am the original poster and translator of the J2 materials list. All of the files I worked with are in post #1. If you would like to review the translation I could send it to you in MSword format so you can mark it up and I would be happy to incorporate your edits in a future revision.

Welcome to the board!
Fast scrolling trough tables I don't see anything obviously wrong or misinformative; you must have definitely put some hours into this document - hats off!
I'll dig a bit deeper and will let you know if there're errors worth mentioning.

Thanks for kind words and once again - good job!
 

Hephaestus

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Here is a primer:
I think I understand - well at least enough to understand I don't understand in proper dunning kruger fashion.

I think it's all the derivative formulas and inconsistent notations and that's killing me... I just go into math overload.

Following the Frati calculations, I was trying to check the spar webs at the root. Either I can't math or I need 9.8mm of birch ply for shear loads. That sounds very wrong.

Putting away math for tonight. I dislike math.
 
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