Ultralight inspired by Georges Sablier?

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cluttonfred

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Georges Sablier was a prolific French aircraft designer especially active in the 1920s and 1930s with many designs for amateur construction as well as a relationship with Spanish company for commercial production of his designs, though I do not know if any were actually produced, certainly not in any great numbers. For more information see:

Georges Sablier (French) (English)
Georges Sablier - Machines (French) (English)
Georges Sablier Type Designations

Be warned that "sablier" also means "hourglass" in French so Google Translate sometimes gets confused.

A number of Sablier's plans packages/construction guides from the 1930s can be downloaded here. Sort by "AUTEUR(S)" and go down to "SABLIER" and clicking on the links will start downloading the files (some are quite large). There are quite of few other interesting documents in many languages including English in that list.

In any case, one particular early Sablier design caught my eye, the Type 3 glider of 1923. It's a conventional parasol monoplane with an usually low aspect ratio (<4) for the time that was reported to be remarkably stable and controllable. The fuselage and struts remind me a bit of the Kimbrel Banty. It's not clear from the photos below but I would guess that the parallel struts are braced with wires in an X and perhaps the cabanes as well. The cabanes could have wires on one side only to facilitate cockpit access.

I could see a less extreme version of the Sablier Type 3 with paramotor engine on the nose and a bigger rudder making a fine, simple, stable ultralight. Simple aluminum tube/gussets/blind rivets for the fuselage and tail surfaces, maybe wood wings, all covered in fabric, BMX bicycle MAG plastic wheels, tail skid for a little braking without real brakes or maybe the Sandlin approach of wheels at the CG and skid under the nose for glider-like braking.

Type-3_01_Notices_p2.jpg

Span/Envergure 6,80 m
Length/Longueur 5,65 m
Wing area/Surface alaire 12,90 m2
Empty weight/Poids à vide 60 kg

Type-3_02_Notices_p2.jpg Sablier_Type-03.jpg

Hmmm....
 

Tiger Tim

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I could see a less extreme version of the Sablier Type 3 with paramotor engine on the nose and a bigger rudder making a fine, simple, stable ultralight. Simple aluminum tube/gussets/blind rivets for the fuselage and tail surfaces, maybe wood wings, all covered in fabric, BMX bicycle MAG plastic wheels, tail skid for a little braking without real brakes
So split the difference between a Texas Parasol and a Heath Parasol? I'm skeptical of a paramotor engine having enough power to pull around all those struts and wires all while carrying a modern human. On the other hand, if it worked you could really be onto something.

A number of Sablier's plans packages/construction guides from the 1930s can be downloaded here.
...and here I was thinking I'd have a productive day.
 

cluttonfred

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Mike Kimbrel's Butterfly Banty and many other true Part 103 ultralights flew with a 28 hp Rotax 277 that weighs about 30 kg/66 lb. Something like a Vittorazi Moster puts out 25 hp and weighs half as much. Something like the Corsair Black Bull puts out 35 hp and weighs just a few kilos more even with electric start. I would be tempted to make it a low-powered LSA/microlight rather than a Part 103/SSDR ultralight to get a little more speed out of it. Here are some very rough numbers for a 25 hp microlight.

Crew weight 200 lbs
Fuel + baggage weight 50 lbs
A/C empty weight 300 lbs
Total weight 550 lbs
CLmax 1.5
Wing area required 139.9 ft²
Induced drag factor K 1.2
Wing span 28.0 feet
Mean wing chord 5.00 feet
Selected rated shaft power 25.0 BHP
Take off run 360 feet
Rate of climb at 1.3 Vs 697 feet per minute
Max level speed 75 mph
Cruise speed at 75% power 68 mph
Flaps up stall speed 32 mph

With 35 hp it would get pretty sprightly...

Rate of climb at 1.3 Vs 1147 feet per minute
Max level speed 83 mph
Cruise speed at 75% power 76 mph

I would probably go with the 35 hp option despite the additional cost and raise the design gross weight to 600 lb or more to allow for hefty pilots and more rugged structure.
 

Tiger Tim

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Crew weight 200 lbs
Fuel + baggage weight 50 lbs
A/C empty weight 300 lbs
For as dead simple as the Sablier above is, I'd be tempted to target 200 for the airframe and 300 for the pilot. Moving the engine and pilot around on this gets you pretty close:
 

cluttonfred

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Thanks, Tim. Eric Clutton test flew one version of the Ritz and it came apart on him (vertical fin departed the airframe) and he crashed. Unfortunately Gerry Ritz was killed in one. Still, I agree that the basic layout is attractive and pusher configuration would make it even easier to use a paramotor engine.

How about this...a Sablier-style design with a pusher paramotor installation aft of the trailing edge, main wheels forward of the rear CG limit, and a glider-like nose skid. Pilot's seat is adjustable fore-and-aft so you move it back as far as possible to rest lightly on the nose skid but not sit on the tail to adapt to varying pilot weights. You should still be able to taxi with back pressure on the stick to lift the nose, stick forward to brake. I could even see this working well with rudder/elevator two-axis controls and no ailerons like a Sky Pup.
 

Tiger Tim

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How about this...a Sablier-style design with a pusher paramotor installation aft of the trailing edge, main wheels forward of the rear CG limit, and a glider-like nose skid. Pilot's seat is adjustable fore-and-aft so you move it back as far as possible to rest lightly on the nose skid but not sit on the tail to adapt to varying pilot weights.
I'm an engine-in-front-tail-in-back kind of guy, but I suppose that could be doable. Seems like the seat track and movable controls(?) add weight and complexity that's maybe misplaced though.
 

Tiger Tim

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Thanks, Tim. Eric Clutton test flew one version of the Ritz and it came apart on him (vertical fin departed the airframe) and he crashed.
I wonder if it was a design issue or one of construction? That's the hard part to separate out when it comes to airplanes built in basements and garages and maybe why developing something to be ultra simple and cheap would be an enormous liability to take on.

In any case I would think the basic minimal box fuselage of the Sablier, that short landing gear, and even the lack of wing centre section all would contribute to keeping the pounds off.
 

cluttonfred

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Ah, I thought you were suggesting the Ritz layout as preferable, I think both can work. FWIW, Polini offers a specific "tractor configuration" mounting kit for their Thor 200 (28-29 hp) and 250 (36 hp, water-cooled head, optional dual ignition) models. They are expensive at $3,500-5,000 but have a good reputation.
 

Victor Bravo

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It is going to be very challenging to do any better than the Kimbrel Banty for this type of layout and minimalist mission IMHO. The only significant improvement I can quickly think of is using the Texas Parasol or Graham Lee construction methods to build a Banty-like structure... but built for the current 103 or LSA environment. Today you might be able to make a real improvement from the paramotor engines' lower weight than the 277. The difference between the 277 and the equivalent Simonini or Polini (about 30 pounds IIRC) will "pay for" significantly more robust structure AND simplified construction. That's huge to my way of thinking. You might even be able to use aluminum tube and gusset and perhaps still meet Part 103. The Banty configuration (like the proposed Sablier-paramotor lash-up) has a lot going for it in this context. There is essentially no landing gear strut (weight savings and cost savings). The engine is forward of the pilot (crash safety, lower thrust line, pilot weight and load path directly under the spars, etc.). The existence of lighter fabric covering systems, like Oratex, will save even more weight, which can be put back into structural reserve and/or reduced parts count. We even have synthetic fibers which weigh a lot less than steel "wire rope". If these new fibers can be safely substituted for wire bracing, more weight can be saved. The whole thing could possibly be less delicate and easier to build.
 

billyvray

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The first Ritz ultralight shown above was a deathtrap. The second Ritz B was better. Two struts, different spars. Neat as it can be. Indianad761_3-.JPG Ritz+001-.jpg ritz3-sm.jpg ritz4-x.jpg
 

addicted2climbing

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I just had a look at the Kimbrel Banty and its quite cute. For the life of me I cant figure why anything flying this slow would need flaps, but then that's an area to remove weight as well. I have mentioned this before on other legacy designs, but the Skylite wings paired to a Tube and gusset (baslee/sandlin) or Angle and gusset like the texas parasol would work well for a modern version of this. A Vitroazzi engine or similar modified for tractor and your there. Polini even better if you can afford it.
 

pwood66889

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"I just had a look at the Kimbrel Banty and its quite cute. For the life of me I cant figure why anything flying this slow would need flaps..."
Bought Banty plans after seeing Kimbrel fly it out of his place. There were some steep approaches into his strip, so I could see where flaps might be a good thing.
 

BJC

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Space for the flaps on the GlaStar and Sportsman is created by removing a fairing on the fuselage. Removal time is a couple of minutes, but could be quicker if desires by the use of CamLocs. Nothing needs to be done to the control cables, fuel lines, pitot tubing or wiring to fold the wings. A GlaStar with the fairings removed can be seen here: upload_2019-4-12_3-55-41.jpeg


BJC
 

cluttonfred

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The British light aeroplane competitions at Lympne in the 1920s included a ground transport/storage requirement that necessitated folding or removable wings. The were some interesting solutions used that included hinged center-section trailing edge, flaps (for folding only or for in-flight use), removable fairings on the top or bottom of the fuselage, and some clever biplane strut arrangements.

Here is the single-seat Gloster Gannet (1923) with folding center section trailing edges top and bottom.



And here is the two-seat Westland Woodpigeon (1924). I couldn't find a good pic with the wings folded but you can see that the front cabane struts actually go from upper to lower wing like permanently-installed jury struts. The vertical hinge point is at the rear cabanes and there is no true center section. The wing splits down the middle from the leading edge to the center rear spar which supports an upward-hinged trailing edge.

 
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cluttonfred

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Eric Clutton was very critical of the geodetic system used in the Ritz designs, particularly because it was "impossible to repair." When asked to explain he said that the Ritz method involved cutting grooves in the longerons and spar caps into which the geodetic strips slotted. Sounds slick, but Eric said that couldn't easily get damaged strips out of the grooves without damaging the key structural members, and you couldn't install new strips next to the old ones because of epoxy dried in the grooves, so you ended up having to add ordinary plywood gussets and ignoring the grooves. So, in fact, Eric took issue with the groove system and not geodetic construction per se.

The first Ritz ultralight shown above was a deathtrap. The second Ritz B was better. Two struts, different spars. Neat as it can be.
 
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