21st century Volksplane?

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blane.c

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My opinion: With enough wing and attention to weight, a large VW can safely fly 2 people. Folks safely fly in Sonexes with two aboard all the time (and receive instruction like that, with a LODA, etc). Sonerai IIs and many other VW 2 place aircraft do it, too. I'm not saying that the Sonex is perfect for this, frankly for the mission of the modern VP 2 I think you'd want appreciably more span than a Sonex or Sonerai to give better climb and to demand less of the engine. Probably 26-28 ft span, maybe 100sf.
Lots of two place planes used to be produced and certified with 65 HP engines. A 2180cc VW engine can give 75 HP reliably for TO and climb. Sure, the prop will be shorter than what a C-65 can swing, but at typical climb speeds the 10 additional ponies will about make up for the difference in prop efficiency.
This is to be a modern Volksplane right? Assume 70-75hp for TO and 65HP in cruise and the engine will live a long time.
Sure, make allowances for other engines, folks may prefer them, may need em for high DA operations, etc. (If you can fit an upright Suzuki in there it will save money compared to a laid down one).
I disagree. A 65p aircraft engine has a lot more cooling fin and mass than a VW. The VW is heat dissipation limited. While a good pilot can manage the VW with two people the average ham handed 25hr a year at most pilot is likely to have problems. Very likely. It is better to outfit the plane with an engine that can dissipate the heat more efficiently for two people especially if the two people care about each other and the pilot is low on time.
 

Vigilant1

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I disagree. A 65p aircraft engine has a lot more cooling fin and mass than a VW. The VW is heat dissipation limited. While a good pilot can manage the VW with two people the average ham handed 25hr a year at most pilot is likely to have problems. Very likely. It is better to outfit the plane with an engine that can dissipate the heat more efficiently for two people especially if the two people care about each other and the pilot is low on time.
The C-65 engine (1800cc) (2785cc, thanks, Blane, for catching that) and the VW Type One 2180cc engine can both make 65 continuous HP. The C-65 can do it with the jugs out in the breeze, the VW will need proper baffling to efficiently get air through the fins.

The VW can still be built from new, inexpensive parts, requires no PSRU, and can be maintained cheaply. IMO, it is a good engine for this project.
 
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Bigshu

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My opinion: With enough wing and attention to weight, a large VW can safely fly 2 people. Folks safely fly in Sonexes with two aboard all the time (and receive instruction like that, with a LODA, etc). Sonerai IIs and many other VW 2 place aircraft do it, too. I'm not saying that the Sonex is perfect for this, frankly for the mission of the modern VP 2 I think you'd want appreciably more span than a Sonex or Sonerai to give better climb and to demand less of the engine. Probably 26-28 ft span, maybe 120sf. 600lb empty weight and a no-kidding 1100 lb MTOW.
Lots of two place planes used to be produced and certified with 65 HP engines. A 2180cc VW engine can give 75 HP reliably for TO and climb. Sure, the prop will be shorter than what a C-65 can swing, but at typical climb speeds the 10 additional ponies will about make up for the difference in prop efficiency.
This is to be a modern Volksplane right? Assume 70-75hp for TO and 65HP in cruise and the engine will live a long time.
Sure, make allowances for other engines, folks may prefer them, may need em for high DA operations, etc. (If you can fit an upright Suzuki in there it will save money compared to a laid down one).
We explored a lot of options and ideas in the 171 pages and over 3,400 posts of this thread. While I have lots of creative itches to scratch when it comes to homebuilt planes, after all this discussion my own thoughts on a 21st century Evans Volksplane VP-2 are pretty conventional:
  • Increase the gross weight a little (say 500 kg/1100 lb) for today's heavier people.
  • Go with a cantilever wing, perhaps a straight 16' center section with dihedral in the outer panels Thorp-style.
  • Increase the wing area and aspect ratio to improve climb performance on modest power.
  • Widen the cockpit for comfort enclose it with a cabin or canopy.
  • Keep the single center stick but the option to solo from the center may no longer be needed.
  • Keep the simple, square lines including constant-chord wing and horizontal tail surfaces.
  • I could go either way on the all-moving tails vs. stabilizer-elevator and fin-rudder.
  • Keep the big bore VW engine (Revmaster, Aeroconversions, Hummel, etc.) as standard but eventually offer Rotax 912 and maybe Suzuki-based options as well.
  • Add optional tricycle gear with a free-swiveling nosewheel and differential brakes, perhaps using dual hand levers on the stick.
  • Keep the fabric covering over everything and the wood wing, but I could see riveted aluminum tube and gusset taking over for the fuselage and/or tail surfaces.
The overall result would be something of a mash-up between the VP-2 and a Pataplume II with a little Siebel Hummel in the styling of the cockpit area.

View attachment 112201 View attachment 112203 View attachment 112204

Someday....
The Pataplume II is really nice looking. I don't remember it being mentioned in the thread, but the Menestrel II is nice also, maybe not as easy to build as we're considering? 1624319078025.png
I think your final list attributes would be an awesome design. When will it be available? Lol
 

blane.c

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The C-65 is not 1.8 liter or 1800cc it is 170 cubic inches or 2.785 liter or 2785cc. The cooling fins are massive in comparison to a VW and it weighs at least 50lbs more sitting in the airplane. The lighter weight of the VW made it a good choice for lightweight single pilot aircraft.
 

Topaz

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My opinion: With enough wing and attention to weight, a large VW can safely fly 2 people. Folks safely fly in Sonexes with two aboard all the time (and receive instruction like that, with a LODA, etc). Sonerai IIs and many other VW 2 place aircraft do it, too. I'm not saying that the Sonex is perfect for this, frankly for the mission of the modern VP 2 I think you'd want appreciably more span than a Sonex or Sonerai to give better climb and to demand less of the engine. Probably 26-28 ft span, maybe 120sf. 600lb empty weight and a no-kidding 1100 lb MTOW.
Lots of two place planes used to be produced and certified with 65 HP engines. A 2180cc VW engine can give 75 HP reliably for TO and climb. Sure, the prop will be shorter than what a C-65 can swing, but at typical climb speeds the 10 additional ponies will about make up for the difference in prop efficiency.
This is to be a modern Volksplane right? Assume 70-75hp for TO and 65HP in cruise and the engine will live a long time.
Sure, make allowances for other engines, folks may prefer them, may need em for high DA operations, etc. (If you can fit an upright Suzuki in there it will save money compared to a laid down one).
This.

It all comes down to mission discipline, realistic expectations, and span. You want to carry two 250 lbs people, full baggage, and fuel for 500+ miles? Pony up for an RV-x with an O-360. You're asking too much for a "cheap" airplane and that's not snobbery or "weight shaming," that's physics.

If you can be disciplined about your expectations - about 1100 lbs gross TO weight, useful load of 350 lbs of total pilot+passenger weight, plus total 50 lb. baggage and fuel for 300 miles - OR - two 200 lbs occupants and zero baggage (meaning a combined total useful load in the <500 lbs range), then you can realistically use a large-displacement VW if you can get span up to about 27 feet or so. Gives you a climb rate at a 5,000' density altitude of just barely 500 fpm - rather like a C-150. Which isn't going to be a skyrocket, but it'll get you there. 32 feet of span will do the job with a higher climb rate of nearly 750 fpm under the same conditions, same motor, same useful load.

If that's "not enough airplane" for you, then you're in the wrong thread. If you need more, you're going to pay more. Because physics.
 

Topaz

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The C-65 is not 1.8 liter or 1800cc it is 170 cubic inches or 2.785 liter or 2785cc. The cooling fins are massive in comparison to a VW and it weighs at least 50lbs more sitting in the airplane. The lighter weight of the VW made it a good choice for lightweight single pilot aircraft.
A C-65 can run WOT all day long. A VW cannot, although it can run at "max continuous power" all day long. That's what the difference in cooling fins amounts to. So an airplane designed with the latter engine in mind has to be able to climb safely, under hot-and-high conditions at maximum weight, at that somewhat lower "max continuous power" setting. For a 65hp VW, that means 57-60hp. Safe climb with that amount of power means limits to payload weight and more span, compared to higher-powered designs. There is no "absolute limit" that says a 65hp VW must be limited to single-seat designs.

It's a matter of designing the airplane to realistic expectations and the engine that will be used. A "safe" powerplant is a matter of those factors being accepted by the designer and the pilot. When the POH says the engine has to be throttled back after 5 minutes to the max continuous power rating, you do that or the "lack of safety of the engine" is your fault, not the engine's. And since VW's were flying two people around in many designs safely in the '60's and '70's, that can clearly be done, even with non-professional pilots. It doesn't take a professional pilot to read a POH and follow its limits. It does take one who doesn't think he knows more than the designer of the airplane.
 

cluttonfred

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While not immediately obvious from the title, this now 10-year-old thread was always about a two-seater. The original Evans VP-2 Volksplane was never intended to be a cross-country machine, just an easy to build, easy to fly, fun machine with room for a friend and so simple that first-time builders think, "Hey, I could do that."

To my mind, those weights you mentioned are too high. Many lightweight, low-speed, wood-and-fabric designs can approach empty weights around 50% of gross weight (the plane can carry it's own weight) and 60% is common. So a 500 kg/1100 lb gross means something like 200 kg/441 lb for people and fuel (2 x 200 lb + 7 gallons of fuel). Every pound you can shave off that empty weight you can add to the fuel capacity or the passenger weight, my goal would be 275 kg/606 lb empty. There is no allowance for baggage, though it would work great for solo travel with a big duffel bag strapped into the passenger seat. Note that these numbers are about 60 lb heavier than the original VP-2 with (in the example below) 2' more span, 12 sq ft more area, and a lot less drag.

My thinking is that the keys to successful two-seaters with modest power are lots of wing area to give low stall speed and good climb regardless of cruise and top speed and fairly low aspect ratio to keep the weight down. Here's a quick spreadsheet design using an airfoil that can manage a CL of 1.5, which means 141.5 sq ft of wing area to make a 45 mph stall speed without flaps. An aspect ratio of 6 seems like a good compromise so we get a little over 29' span and nearly 5' chord for 141 sq ft of area. Lower aspect ratio saves weight but starts eating into the climb rate. I have upped the parasitic drag factor from the base number (I prefer to be pleasantly surprised) and rated the engine at just 75 hp. Climb is pretty good but cruise speed is less than 100 knots, so just install an an airspeed indicator in kph instead. ;-)

I think something like this could be a lot of fun for not a lot of money.

Crew weight440lbs
Fuel50lbs
A/C empty weight610lbs
Total weight1100lbs
Stall speed (flaps up) Vs145mph
Climb airspeed58.5mph(climb speed = 1.3 x stall speed)
Climb airspeed85.8ft/sec
CLmax1.5(flaps up)
CL at 1.3 Vs0.89(at 1.3 Vs, CL = CLmax x (1/1.3²))
Wing area required141.5ft²(L=1/2 rho V² S CL)
Propeller efficiency at take-off7070%
Propeller efficiency in the climb7575%
Propeller efficiency in the cruise8585%
Cd (profile)0.010.01
Cd (parasite)0.02250.015(Speeds between 1.1 Vs and 2.7 Vs)
Aspect ratio6
Induced drag factor K1.2(Cd (induced) = K CL²/π A)
(K = 1.0 elliptical wing, 1.1 moderately tapered, 1.2 rectangular)
Wing span29.1feet
Mean wing chord4.86feet
Selected rated shaft power75.0BHP
Effective flat plate area4.98ft²
Take off run474feet
Rate of climb at 1.3 Vs1208feet per minute
Max level speed123mph
Cruise speed at 75% power111mph
Flaps up stall speed45mph
Glide descent rate at 1.3 Vs480feet per minute

Decide if it is single place or two place. If single place VW is fine if two place it needs a bigger engine to dissipate heat maybe small Aeromomentum . If single place 900lb gross max if two place then may as well go 1320lb. Yes please widen cockpit. The faster it goes the more critical the balance of the all flying tail? Tricycle gear as option for the savages. Toe brakes.
 

blane.c

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What happens is marginality. The VW in a two place airplane (not glider) is marginal. When you take off marginal your options are limited from the beginning.
Another thing is experience and this is an aircraft earmarked for the inexperienced.
So marginality and inexperience ... hmm ... what is wrong with this picture?
 

Topaz

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Blaine, if you're saying "it's impossible," I can tell you that you're simply flat-out wrong. As you note yourself, two-seaters with VW and more span can, and have, flown nicely. The VP-2 didn't have enough span for its power and its weight to generate a safe climb rate, which is why it was discontinued. It was "marginal," as you say. A purposed-designed two-seat airplane, properly designed for one of the larger displacement VW options, would not be "marginal."

What's "wrong with this picture" is the assumption of "marginality." That's a faulty assumption. More span than the original VP-2 is needed, certainly, but not necessarily "a glider." What's needed is realistic expectations and proper design for the mission requirements. Proper design to the mission requirements. Can't just be "eyeballed."
 

cluttonfred

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Henri Nicollier's HN700 Ménestrel II is truly lovely and a good performer on a VW, but more refined and a little more challenging to build that what I had in mind. His HN800 Weekend II loses the curves but it's still more complicated than I'd like for the VP-21.

The Léger Pataplume II is actually about the closest thing to my concept that I know of in terms of plans you can go out and buy right now, so much so that I have had the plans for several years. I still want to build an original VP-2, but the Pataplume 2 is very high on the wish list.

There are two downsides to the Pataplume II for me. First, it was designed to the original 450 kg/992 lb gross weight limit for two-seat microlights so even though it's quite light at 278 kg/613 lb empty, that leaves just 178 kg/379 lb useful load. Second, it typical European style, the wing is built on one piece 9.11 m (29' 11") from tip to tip, awkward without a very big shop. Still, in a pinch, my backup VP-21 would be a Pataplume 2 built as light as possible.

More on the Léger Pataplume 2:
Fabien et Jean-Claude Léger, concepteurs (in French, scroll down for the low-wing two-seater)

More on Henri Nicollier's designs:
Nicollier Henri concepteur (also in French but Google Translate is your friend)

The Pataplume II is really nice looking. I don't remember it being mentioned in the thread, but the Menestrel II is nice also, maybe not as easy to build as we're considering?
I think your final list attributes would be an awesome design. When will it be available? Lol
 

Topaz

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Interesting. Three types of which I've never heard. Still, all three are in the tight little zone we've been talking about, in terms of weight, span, useful load, and power. It's just the math. A US-optimized airplane would probably have a little more span because of the higher density altitudes more common here (especially in the Western US), but these are in the ballpark.

Matthew, it'll come down to using numbers like this and designing an airplane around them. There won't be anything out there exactly like you want until you design it. You have several templates for basic numbers from which to start and to compare your developing design for realism.
 

blane.c

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A last thought. I believe Mr. Evans designed a plane he felt anyone who really put there mind to it could afford and build and it would be a safe airplane. And it is a hard dogma to adhere to over 50 years later and the same engine. I wonder if Mr. Evans would still consider the VW his first choice with all the considerations today?
 

Topaz

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A last thought. I believe Mr. Evans designed a plane he felt anyone who really put there mind to it could afford and build and it would be a safe airplane. And it is a hard dogma to adhere to over 50 years later and the same engine. I wonder if Mr. Evans would still consider the VW his first choice with all the considerations today?
Maybe he'd just build a different wing, one with a longer span? That would solve the "problem," too.
 
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