Quantcast

The Janowski Project - Rethinking the J1B/J2/J3

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
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?
Think the Legal eagle is 3/8", but they also don't have 30/45mm wide plywood flanges covering each one.
Belite-CF-Wing.jpg
You know I hate wood and prefer to order jugs of resin and rolls of fabric from china right? :) I think some simple vacuum bagged fiberglass or CF would be my preference. (That pics stolen from belite)

Kind of why I'm wondering about getting someone to help with the loads / design verification... Of course I realize my error here in that there's about 0 data on the J-2 to derive that from, I couldn't even get through the basics of the roncz spreadsheets - so I guess that figuring out some basic numbers is probably the next step.

J2 Wing.png
Looks pretty right? Except they don't fit. I've got to take a look, Somehow I'm just under 3mm shorter than the spar. but they were derived off the spar. Gotta admit my head hurts 🤦‍♂️
 

Mohawk750

Well-Known Member
Joined
Jan 1, 2021
Messages
111
Location
Ottawa, Ontario
Great Job! Errors and misfitting aside this really helps visualize the structure. I suppose a person would have to get the dimensions figured out on the main structural members and calculate their loads to know where you can afford to modify to save some weight.

For me, if something is simple economical to build then I'm willing to take a weight penalty and adjust the CG and power accordingly. If you are striving for maximum efficiency in the design, minimizing all weight and powering with the smallest engine that provides adequate performance then its likely to get complex and expensive. That and I know nothing about composites other than I built an ais scoop and a couple of wheel pants with box store cloth and resin once but that was all none structural.
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
Great Job! Errors and misfitting aside this really helps visualize the structure. I suppose a person would have to get the dimensions figured out on the main structural members and calculate their loads to know where you can afford to modify to save some weight.

For me, if something is simple economical to build then I'm willing to take a weight penalty and adjust the CG and power accordingly. If you are striving for maximum efficiency in the design, minimizing all weight and powering with the smallest engine that provides adequate performance then its likely to get complex and expensive. That and I know nothing about composites other than I built an ais scoop and a couple of wheel pants with box store cloth and resin once but that was all none structural.
I'm more about holy crap aircraft spruce wants how much to ship it? ;) I know it's on par for ltl truck freight since it's not usually UPS/Fedex sized pieces - but... Scottish side of me wants to go ballistic. You might not be so bad in ontario. Pretty sure there's a - he lives in alberta, nail him to the wall tax for me :)

Not so much bleeding edge of performance - more economy, even at IPP here, the per foot price for the 'house' 3k 200gsm/5.7oz 2x2 carbon twill - 16' per layer with tons of scrap you'd still be able to do 2+ layers of carbon before you got to the AcSS wood cost (before shipping). order a 50yd roll off ebay/alibaba and you're even farther ahead. And carbon's way more expensive than fiberglass. It's that ability to pickup resin locally, rolls of materials aren't cheap - but ship cheaply, and you only need a few varieties. It's the shipping that tips it way over into composites are actually more affordable. Rant over...

Anyway - if one of those aero / structures people is feeling like teaching us wrenchbenders...

J2 Numbers:

Wingspan - 7144mm / 218.25" / 23.44'
Chord - 1000mm / 39.37" / 3.28'
Area works out to 76.88sqft
Aspect ratio if math works today - is 7.15
23015 Airfoil at 5deg incidence.

Hstab/elevator - 15.58sqft - located at 4275mm/168.3" back from datum (nose) WL is +750mm/29.5"
Vstab is 5.68 sqft - located 3250mm/127.9" behind datum
Prop located 2700mm/106.3" behind datum
Engine C/L (VW 1600 - 55hp/185lbs dry) 2450mm / 96.5" behind - 600mm/23.6" above WL.
Wing LE - 1450mm/57" behind Datum
Ballpark pilot bellybutton/cg - 1250mm/49.2" behind datum - pretty much on WL.

Don't have any weight data. I'd peg MTOW at 650lbs. If it was trying to hit US ultralight rules, that'd be 555lbs with a 275lb pilot and 5g of go-juice. Lets start with utility category, so +4.4 / -1.7g
 
Last edited:

Ried

Active Member
Joined
Dec 30, 2010
Messages
27
Location
Downers Grove, IL / USA
Data from Jane's all the World's Aircraft 1975-76[2]

General characteristics

  • Crew: 1
  • Length: 4.88 m (16 ft 0 in)
  • Wingspan: 7.6 m (24 ft 11 in)
  • Height: 1.4 m (4 ft 7 in)
  • Wing area: 7.5 m2 (81 sq ft)
  • Aspect ratio: 7.7
  • Empty weight: 163 kg (359 lb)
  • Gross weight: 270 kg (595 lb) or 293 kg (646 lb) with 37 kW (50 hp) engine
  • Fuel capacity: 18.2 litres (4.8 US gal; 4.0 imp gal)
  • Powerplant: 1 × Janowski Saturn 500B 2-stroke 2-cyl. horizontally-opposed air-cooled piston engine, 17 kW (23 hp) or 37 kW (50 hp) VW conversion
  • Propellers: 2-bladed Janowski wooden fixed pitch pusher propeller, 1.06 m (3 ft 6 in) diameter
Performance

  • Maximum speed: 135 km/h (84 mph, 73 kn) or 207 km/h (129 mph; 112 kn) with 37 kW (50 hp) engine
  • Cruise speed: 120 km/h (75 mph, 65 kn)
  • Stall speed: 58 km/h (36 mph, 31 kn)
  • Never exceed speed: 180 km/h (110 mph, 97 kn)
  • Range: 250 km (160 mi, 130 nmi)
  • Service ceiling: 2,500 m (8,200 ft)
  • g limits: +4 -1.5
  • Rate of climb: 2.0 m/s (390 ft/min) 3.99 m/s (785 ft/min) with 37 kW (50 hp) VW conversion
  • Wing loading: 36 kg/m2 (7.4 lb/sq ft)
  • Power/mass: 0.083 kW/kg (0.05 hp/lb)
  • Take-off run: 200 m (660 ft)
  • Landing run: 150 m (490 ft)
Data from Google search on "janowski j2" to Wikipedia page on Don Quixote referencing Janes Aircraft. For what its worth!
 

Ried

Active Member
Joined
Dec 30, 2010
Messages
27
Location
Downers Grove, IL / USA

Urquiola

Well-Known Member
Joined
Aug 23, 2013
Messages
132
Location
Madrid, Spain
Fine job! Anybody has experience in the use of 'Marine plywood', or 'Royalite' in homebuilt airplanes?
Thanks. Blessings +
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,758
Location
US
Ref below: It looks like they may have an error in the "Never Exceed' speed of the J1, since it is less than the listed "Max Speed."

Also, she scoots along pretty well on 50hp (129 mph max). That's a big increase from the max speed with the 23 hp engine (84 mph). It indicates that the design is aerodynamically pretty clean with a low Cd and that induced drag still probably makes up a significant portion of the drag at 84 mph.
That 4.8 US gallon tank is a limiting factor. About 75 minutes of total running time on that 50 hp VW at WOT, and the 23 hp 2 stroke wouldn't be a whole lot better. The modest max range (160 sm) listed seems about right.
Data from Jane's all the World's Aircraft 1975-76[2]

General characteristics

  • Crew: 1
  • Length: 4.88 m (16 ft 0 in)
  • Wingspan: 7.6 m (24 ft 11 in)
  • Height: 1.4 m (4 ft 7 in)
  • Wing area: 7.5 m2 (81 sq ft)
  • Aspect ratio: 7.7
  • Empty weight: 163 kg (359 lb)
  • Gross weight: 270 kg (595 lb) or 293 kg (646 lb) with 37 kW (50 hp) engine
  • Fuel capacity: 18.2 litres (4.8 US gal; 4.0 imp gal)
  • Powerplant: 1 × Janowski Saturn 500B 2-stroke 2-cyl. horizontally-opposed air-cooled piston engine, 17 kW (23 hp) or 37 kW (50 hp) VW conversion
  • Propellers: 2-bladed Janowski wooden fixed pitch pusher propeller, 1.06 m (3 ft 6 in) diameter
Performance

  • Maximum speed: 135 km/h (84 mph, 73 kn) or 207 km/h (129 mph; 112 kn) with 37 kW (50 hp) engine
  • Cruise speed: 120 km/h (75 mph, 65 kn)
  • Stall speed: 58 km/h (36 mph, 31 kn)
  • Never exceed speed: 180 km/h (110 mph, 97 kn)
  • Range: 250 km (160 mi, 130 nmi)
  • Service ceiling: 2,500 m (8,200 ft)
  • g limits: +4 -1.5
  • Rate of climb: 2.0 m/s (390 ft/min) 3.99 m/s (785 ft/min) with 37 kW (50 hp) VW conversion
  • Wing loading: 36 kg/m2 (7.4 lb/sq ft)
  • Power/mass: 0.083 kW/kg (0.05 hp/lb)
  • Take-off run: 200 m (660 ft)
  • Landing run: 150 m (490 ft)
Data from Google search on "janowski j2" to Wikipedia page on Don Quixote referencing Janes Aircraft. For what its worth!
 
Last edited:

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
SparFitment2.png
SparFitment.png

So it's right in size... But I missed this detail (note to self - stop overlaying too much information), guess the intention is to do a little sanding/planing to make the spars match the ribs. Wonder how many designs this has left builders scratching their heads for days as to how the numbers didn't work out. Glad its in electrons - lot harder to move them when physically building.
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
That 4.8 US gallon tank is a limiting factor. About 75 minutes of total running time on that 50 hp VW at WOT, and the 23 hp 2 stroke wouldn't be a whole lot better. The modest max range (160 sm) listed seems about right.
One of the nice things about swapping that mono wheel for a conventional gear- is it opens up a lot of space for fuel.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,758
Location
US
One of the nice things about swapping that mono wheel for a conventional gear- is it opens up a lot of space for fuel.
Other advantages of either conventional or trigear over the monowheel:
-- With a larger "deck angle" available for TO and landing, we could probably reduce what appears to be a fairly high wing angle of incidence. That will put the fuselage in better alignment with the relative wind at cruise, particularly if we are cruising at relatively high(er) speeds.
-- Better ability to absorb crash energy in a flat impact. Just a lot more "stroke" available.
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
J2-Spar.png
Spar details in case anyone gets there.

@clanon Thanks for that.

The J3 really starts to look like a J2 with conventional gear, full span ailerons, and motor moved forward/up the more I look at it. Going full span could allow flaperon mixing...
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
Nice spar! looks a bit like here: REALISATION LONGERON | MAGIC 2
Buy a roll of 0.5mm (wonder if 1mm would be rollable enought) pultrusion from alibaba (like Rol Klingberg for his wing) and don't pay a fortune for shipping (or even, in an international context, just finding) spruce!
That's an interesting Spar design.
Longeron-magic.jpg
Just for now want to ensure it's overall safe / buildable. Optimizing is a much later date thing :)
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
This afternoons... "What detail am I missing?"
NoseRibReinforcement.png

#18's listed as nose rib reinforcement. 1x20x250 - Birch ply.

250mm could do the bottom or the top, from spar to LE poplar. I'd imagine it's used on top surface. Just trying to understand the purpose - as a extra lamination of 1mm onto the 1.5mm there that's not tied into anything else doesn't make a ton of sense to me.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,758
Location
US
This afternoons... "What detail am I missing?"
View attachment 106956

#18's listed as nose rib reinforcement. 1x20x250 - Birch ply.

250mm could do the bottom or the top, from spar to LE poplar. I'd imagine it's used on top surface. Just trying to understand the purpose - as a extra lamination of 1mm onto the 1.5mm there that's not tied into anything else doesn't make a ton of sense to me.
I think you're probably reading it right. 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. It supports the skin against buckling, like the "false ribs" that are frequently placed forward of the spar. I guess a complete false rib with a web and tie-in to the spar wasn't found to be needed. The "nose rib reinforcement" label is a little confusing, maybe a translation issue. "Intermediate skin reinforcement" or "nose reinforcement strip" would be better, if I've got this right.
 
Last edited:

Mohawk750

Well-Known Member
Joined
Jan 1, 2021
Messages
111
Location
Ottawa, Ontario
There were lots of translation issues, sometimes the google translation made absolutely no sense at all but I agree the reference to a rib when there is no rib is misleading. Maybe that detail needs a new name...I struggled sometimes trying to fully describe certian parts but I can just call it a "reinforcement" and be done with it.
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
2,041
Location
YMM
I think you're probably reading it right. 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. It supports the skin against buckling, like the "false ribs" that are frequently placed forward of the spar. I guess a complete false rib with a web and tie-in to the spar wasn't found to be needed. The "nose rib reinforcement" label is a little confusing, maybe a translation issue. "Intermediate skin reinforcement" or "nose reinforcement strip" would be better, if I've got this right.
Yeah, getting it, just not seeing the load path I guess you could say. 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?

Just asking seemed off to me eyes.

J2-Roncz.png
That's with a 275lb sasquatch in the front seat and 2hrs fuel in the stock location. I need to go back to the articles and make sense of a bunch of fields, and figure out where @rtfm has them tucked away in this version :)

Yay autodesk finally un-screwed-up the renders! (looked like crap every time I used it since ?sept/oct?)
Janowki J2 Wing.png
(used transparent plastic in place of plywood so you can see)
 

Latest posts

Top