21st century Volksplane?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cluttonfred, May 8, 2011.

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  1. May 8, 2011 #1

    cluttonfred

    cluttonfred

    cluttonfred

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    I have always been a fan of the Evans VP-1 and VP-2 Volksplane. Yes, they are underpowered and perhaps a little short on wing area (especially the two-seater) and certainly homely. Still, they have a charm all their own, a bit like full-size versions of the Guillow's balsa gliders and rubber-powered planes you can still get at the corner store.

    There is another aspect of the Evans VP designs that can't be overestimated--they LOOK easy to build and that alone has been enough to help many would-be builders stop dreaming and start cutting wood. The same is true in boatbuilding, by the way. My first boat essentially looked like a soap dish with a sail and I was very proud of it. I later learned that it was no harder to make something that looked more like a boat, but that first boat, a Bolger "Brick," served its purpose--it got me to stop dream and start cutting wood. Full disclosure, I have built several boats, but not one airplane yet.

    So, let me put it to this group. I'd like to see a 21st century Volksplane, a little plane that is easy and fast to build and looks that way: constant-chord wings and control surfaces, straight lines, something that makes almost anyone say, "Heck, even I could built THAT."

    I'd still want to use VW power: direct-drive, 60-80 hp, simple and relatively cheap, say a Great Plains 1835cc on the low end and an AeroVee 2.0 on the high end. I'd like two seats and either an enclosed canopy or at least a layout that makes it easy to enclose or not as climate warrants. Docile handling for ham-fisted low-time pilots is essential, though I could see going with conventional landing gear for the short and rough field advantages. A choice between tricycle and taildragger would be ideal.

    I don't want to spend a couple of years of my life with toxic chemicals and itchy fibers, so composite construction is out, though fine for a cowling or a fuel tank. Neither do I want to spend a lot of time with cold, cutting sheet metal or buck a lot of rivets, though again, a little sheet metal work here or there is fine. Spruce, plywood, steel, aluminum, fabric in some combination should make up most of the airframe.

    Nominees from among existing designs are welcome. I'm also hoping some budding designers might share their concepts and projects.

    Thoughts?
     
    Timstertimster, FritzW and Chlomo like this.
  2. May 8, 2011 #2

    Vigilant1

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    Would a tri-gear version of the existing VP-2 meet your requirements? IIRC, some of these have been fitted with canopies.

    If we're going into the 21st century, I'd say it would be best if the design also met the US LSA criteria (so folks could still fly it without a Class 3 medical). Yes, a tri-gear option for this century (As Dave Thatcher has noted, the last high-volume taildragger design went out of production over 50 years ago. Today's students are largely learning in trigear acft).

    I wonder if a 21st century Volksplane would be made of wood. I understand your preferences, but aircraft plywood is dear stuff now, and hangar space has increased considerably in price and getting scarcer these days. I'd hate to keep a wooden airplane outside. A simple pulled-rivet metal design might be the construction material of choice for today. I've also wondered if a "quick-and-easy" composite bird couldn't be built with flat panels laminated all at once and then cut to shape, with a triangular-cross-section boom and empennage section.
     
  3. May 8, 2011 #3

    Hot Wings

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    I've also wondered if a "quick-and-easy" composite bird couldn't be built with flat panels laminated all at once and then cut to shape, with a triangular-cross-section boom and empennage section.

    Kind of a modern composite version of the Flaglor Scooter?

    Flaglor Sky Scooter by Rotor Wings & Flying Machines
     
  4. May 8, 2011 #4

    cluttonfred

    cluttonfred

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    I have often thought that if high quality, factory-made composite panels could be had for a reasonable price (say no more expensive than aircraft plywood), then there would be real incentive to develop fabric-covered composite designs much like a balsa-and-tissue model. Parts could be CNC cut from the flat sheets, complete with slots and tabs, and the builder just glues it all together. Unfortunately, I am still waiting for those inexpensive, high quality composite panels. If I have to do all the nasty, stinky, toxic layup myself, it gets a lot less interesting.
     
  5. May 8, 2011 #5

    orion

    orion

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    We actually looked into doing just that about two years ago. At first look the idea has a lot of merit however only a small part of the airframe is built out of those panels - quite a few other parts have to be molded so in the end the costs weren't as attractive as we first hoped. Our design was based on commercial grade panels (2-core-2 with 7781 glass and aluminum honeycomb - made by an aerospace supplier) but even at that the panels were coming in at about $550 to $700 each. By the time all was said an done, just in panels alone we would have had between four and five thousand into it to start. By the time we added in the CNC router cutting and all the other components one needs for an airframe, the kit cost would've been well past the $20K mark, something we felt was too high given the marginal performance (and ours would've outperformed the VP by quite a bit).
     
  6. May 8, 2011 #6

    davidb

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    The most appealing thing about the Volksplane is you can actually get pretty far into the build with just a few hundred dolars.
     
  7. May 8, 2011 #7

    cluttonfred

    cluttonfred

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    Which brings us back to Mother Nature's composite...wood. One design that I look to for inspiration is Michel Barry's Souricette microlight, which combines spruce, plywood, foam and fabric in a very efficient package. A side-by-side, VW-powered design inspired by the Souricette but with a canopy and the option of tricycle ear might work out very well.
     
  8. May 8, 2011 #8

    Vigilant1

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    Could it be done economically as a plans-built? The plans would include full-size templates (mylar?). All panels would be laminated by the builder while flat (1/2" Divinycell). All parts cut using a Rotozip or (faux!?!) Multimaster. For folds, dig a "V" and leave the outer lamination skin intact, fold to the desired angle and patch on the inside near the seam to hold everything in place. Like "Foldaplane", but no curves and no core or skins under stress. The remaining unused portions of the large laminated panel is available for use as gussets, doublers, etc. Wings and tail surfaces hotwired (simple-strong-fast!) and removable, put the fuel in a large header tank. Enough wing to meet LSA stall criteria. Consider flaperons in lieu of flaps for simplicity and to get stall speed down even further (IMO, low stall speed is one of the best "safety features" one can put in a GA aircraft). Combine gear legs and engine mount for still more simplicity, all available welded up.

    Some folks don't like working with composites, but doing all the laminating at once (maybe two days for the panels?) takes a lot of the sting out of it. If vacuum-bagged and the outside skin put against a smooth tool (e.g. Formica), the dreaded "sand-fill-sand" drama is virtually eliminated and the panel can be fairly light. That addresses two of the biggest gripes about foam-and-glass, and leaves the builder with a fairly easy road ahead with little wet epoxy work to do over the main course of the project.

    It probably wouldn't be beautiful, but it might be fast and cheap to build--which can be beautiful.
     
    Last edited: May 8, 2011
  9. May 8, 2011 #9

    Topaz

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    Weight control is going to be the biggest issue. Much as I love the VWs (as evidenced elsewhere - ahem), they're not very powerful in the scheme of things. MTOW needs to stay in the sub-900# range and still keeping plenty of span if you want to have any hope of a reasonable (and safe) climb rate. Pulling 400# out of that 900 for pilot and passenger (and these days, a lot of people will want more flesh-payload than that) leaves only 500 for airframe, baggage, and fuel. Pull 170# for the latter two items and now you're down to 330# for airframe and engine, and the VW conversions run about 175# installed, leaving 155# for airframe, including avionics. That puts you into "million little sticks" space with wood structures, which increases build time.

    Not impossible, but challenging to say the least. This is one of the larger reasons the VP-2 was pulled from the market. It was just too heavy for the recommended powerplant. If you let the MTOW grow to a more-reasonable 1200#, you're back to a 100hp engine requirement for reasonable spans and wing-loadings. It's a tight trade space.

    I agree that there's likely a market space for the sort of airplane/kit you're describing. You just are going to have to trade speed and build complexity for engine power and cost. Make those trades skillfully and you could do well.

    The comment made earlier about the VP series selling well because they looked easy to build is very astute, especially for the kind of first-time builder we're talking about here.
     
  10. May 8, 2011 #10

    Autodidact

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    For the weight that Topaz is talking about and to get enough performance I think it would need to be aluminum, simple as possible, and maybe a tandem seat cantilever low wing with tri gear and a very long wing. Either that or go the Aeronca C-3 route. Their were some English planes made in the 20s and 30s that were much like you're talking about. But to make the most of the VW's charactaristics, I think it should be relatively clean aerodynamically. I wouldn't even bother with flaps.
     
  11. May 9, 2011 #11

    Vigilant1

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    I agree that weight is going to be a challenge, but there might be a little more leeway. By most accounts the Aerovee (80 HP) Sonex is a fine performer with one aboard and full fuel, and a bit of a dog but not unsafe with two aboard and a MTOW of 1100 (probably satisfactory at low density altitudes, not so good at higher DAs). The factory 80 HP Sonex comes in at an empty weight of 620 lbs (with engine), so it would seem reasonable to assume our "New Volksplane" might be okay at a similar empty weight, particularly if we design with more than the Sonex's 22' wingspan and 98 sqft of wing area.

    I don't know if anyone has ever built a two-place version of the M-19 Flying Squirrel, but that airplane seems to do a good job of optimizing the best characteristics of wood, foam, and fiberglass in an easy-to-build "primitive" airplane. The single-place M-19 is 494 lbs, so if we add another 100 lbs for a two place we'd still be in the ballpark weight-wise. 100 lbs = more fuselage, stronger spar, 2100+cc engine, maybe some brakes, a few more gallons of fuel, some "cooling tin" around the heads, etc). It might not even need more wing, it already has 104 sq ft, a span of 24' and stalls at approx 35 kts.

    [​IMG]
     
  12. May 9, 2011 #12

    BBerson

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    If you think the VP-2 is underpowered, how can a new design do any better with VW power?
    I think the two seat VW powered airplane is not the best idea. Unless the two occupants are quite light.
    Airplane designers are often very small people.

    p.s. I own a VW (Limbach) powered two seater (Grob G109). It is quite underpowered with two seats filled. And it has 55ft span.
     
  13. May 9, 2011 #13

    Topaz

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    A VW powered airplane is never going to be something for two large people, lots of baggage, and lots of range and a high cruise speed. You can have a few of those things, but not all. 65-80hp just isn't enough power for that, regardless of the nameplate oj the engine.

    A two-seater with some modest utility and good for a man and woman? Sure. Two large men, full fuel and baggage, on a VW with a high cruise speed? Not likely. Not on 80hp or less.
     
  14. May 9, 2011 #14

    steveair2

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    I always liked the idea of a VP-1 with Wittman gear, a belted PSRU and larger prop. With a spinner and a more streamlined cowl and canopy.
     
  15. May 9, 2011 #15

    Elmog

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    I would stick with wood construction similar to a VP1/2 and possibly go with a direct-drive Corvair powerplant. The Corvair is capable of lifting two people as demonstrated in the popular 2-place Peitenpol and would work well with a wingspan similar to the Evan's VP planes. When you limit yourself to a particular powerplant like the VW, you limit your design options. If you are willing to open up your engine choices you can have your cake and eat it too! The Corvair would cost more than the VW but it can be built economically if you know what you are doing.
     
  16. May 9, 2011 #16

    cluttonfred

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    Thanks, all for the comments. Would add that I was not expecting cross country performance for two, in fact, I never mentioned baggage at all. With the VW power I was describing, I had in mind a passenger OR baggage, not both. Personally and because of the limitations of the VW, I'd prefer to stay within European two-seat microlight specs, meaning 450 kg gross weight at 65 kph stall speed.
     
  17. May 9, 2011 #17

    Dana

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    One other advantage to wood is again the "I can do that" thing. Virtually everybody has built something with wood at some point in their lives, so it seems doable. Some years ago I was helping a friend build a ski rack for his car, using some square steel tubing. Simple, just hacksaw to length and drill some holes... he was amazed; he knew woodworking but never realized that metalworking could also be easy to do, just requiring some different tools.

    -Dana

    Puritanism: the haunting fear that someone, somewhere, may be happy.
     
  18. May 9, 2011 #18

    Vigilant1

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    So, the original VP-2 meets all your criteria (wood, stall speed, mission, VW power) except that it isn't a trigear and it has a MTOW 22 kg (48 lbs) too much. Adding the nosewheel in place of the tailwheel is going to add a little more weight. On the other hand, there are good VW powerplants now that can reliably put out approx 33% more power (for at least TO and a short climb) than the 60 HP called for in the VP-2 plans, the climb performance issues that dogged the VP-2 might not be so problematic. So, maybe a good starting point is to see where you can modify the VP-2 to lose some weight, possibly using materials or techniques not available when it was designed.
    If not the VP-2 itself, what elements in a wood design would you like to change? I think the material choice together with the desire to get within the microlight limits are going to be a significant challenge. It's hard to build a wood wing big enough that doesn't break your weight budget.
     
    Last edited: May 9, 2011
  19. May 9, 2011 #19

    Topaz

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    Actually, it's easy. Just takes a long time to build. Built-up truss ribs, a built-up I-beam spar, etc. A million little sticks. It'll be very light and strong, but will take more effort to build. Look at the ULF-1 ultralight glider for an example.
     
    Last edited: May 9, 2011
  20. May 9, 2011 #20

    Autodidact

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    If all you need is a bending brake and a drill, it would be relatively easy for most anyone. It's clean and simple and requires (potentially) the least an mount of work and expense.

    But if you insist on a simple to build wood structure, I would suggest going to the Corvair powerplant. Although, I think Mattew's formula could be done for the VW in metal and pulled rivets. You could save weight by making the cockpit Cub-like in the respect that it has only one instrument panel (since there are so few instruments, maybe "dashboard" is a better term) and the POC looks over the front passenger's shoulder - works for the Cub.
     

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