Cantilever parasol wings?

Discussion in 'Hangar Flying' started by cluttonfred, Mar 11, 2019.

  1. Apr 21, 2019 #81

    cluttonfred

    cluttonfred

    cluttonfred

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    I don't see it that way, I think you can have a Fokker-style fun plane that isn't going to be confused with a replica. That won't prevent some people from dressing up the fun plane in WWI colors, of course, but that's fine. Here's a side-by-side comparison.

    [​IMG]
    [​IMG]
     
    Last edited: Apr 21, 2019
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  2. Apr 21, 2019 #82

    Tiger Tim

    Tiger Tim

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    Side by side that little fella really is just a 3/4 scale D.VIII, isn’t it? I love that it was even covered in leftover lozenge fabric, though I’m biased because I just finished painting a wall of my office in Fokker five colour lozenge...
     
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  3. Apr 21, 2019 #83

    Bill-Higdon

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    Cute Little Fokkers aren't they 0:)
     
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  4. Apr 21, 2019 #84

    crusty old aviator

    crusty old aviator

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    The DR-1 had a pretty hefty box spar the cabanes attached to. You could make a scaled down boxspar using geodetic for the webs to make a strong, light spar. I built one in the mid ‘80’s using four 1” x 1” Sitka for the “corners” with 1/2” x 1/8” diagonal strips for the webs. The Sitka had a 1/8” channel ripped into two adjacent sides, the entire length, 1/4” from the edge, to accommodate the diagonals. A 20’ section weighed about 12 pounds and supported over 2500 pounds of sand, simulating 5g’s, overnight (~12 hours) without permanent deformation after the load was removed.

    Laird biplane fuselages have 4130 tubing from the firewall to just aft of the cockpit, then aluminum tube back to the tailpost. The aluminum structure is braced with bicycle spokes that run from the tube intersections to the center of each bay. In the center of each bay is a 3/4” long section of 2” dia. aluminum tube with four holes in it. In each hole is a spoke nut, like would be in a bike tire rim. The bent end of the spoke (that would normally be in the hub) is attached to the fitting at the tube intersection that holds the intersection together. Perhaps this would work in your application. Matty Laird truly took biplane design about as far as it could go.
     
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  5. Apr 21, 2019 #85

    Dillpickle

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    [QUOTE="Victor Bravo,
    Honestly Matthew, the amount of malicious mischief that you cause on this forum by making all of us innocent people stop and think about these cool airplanes and interesting ideas... :)[/QUOTE]


    <<<<This!
     
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  6. Apr 21, 2019 #86

    erkki67

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    88A5F04D-11BB-421C-A198-040BE088AB1D.jpeg

    This critter inspires me for a little more modern layout, as said before a Cub style landing gear and a rudder like on the Dream Classic of Airdrome Aerolplanes or the one of the Flitplane.

    The axle on this V.40 is just a nightmare with those molehills!
     
  7. Apr 21, 2019 #87

    BJC

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    ... with a Verner Scarlett 3VW.


    BJC
     
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  8. Apr 21, 2019 #88

    erkki67

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    Yes yes yes....:D
     
  9. Apr 21, 2019 #89

    cluttonfred

    cluttonfred

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    The 35-45 hp four-stroke range is pretty attractive if you are not trying to stay within Part 103 ultralight weight limits. You have a range of options based on cost up to the Verner 3VW which would be perfect with 42 hp at 2,500 rpm but not cheap at about $8,000 including the prop and electric start plus another $1,000 if you want dual ignition.

    The industrial V-twin option is particularly interesting here, something like the Briggs & Stratton Vanguard 993 cc or Kohler OHV 999 cc gives you 35 hp @ 3600 rpm. Add an Ace 1:1.8 redrive to swing a big, slow, efficient, and vintage-looking 72-76" prop at just 2,000 rpm. Cost including engine with electric start, redrive and prop would be about $4,000.

    You could get a Hummel half VW for not much more, but I doubt that even the biggest half VW would beat the V-twin/redrive combo because of prop efficiency unless it had its own redrive.
     
  10. Apr 22, 2019 #90

    Riggerrob

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    Geodesic construction might be light and only need small pieces of wood, but the disadvantage is increased labour cost.
    I suspect that the majority of homebuilders would cheerfully glue in a bias-cut, plywood spar web. The single piece spar web also simplifies aligning all the ribs.
    A plywood D-spar is great for carrying torsion loads. Glue it directly to spar caps and extend it far enough aft of the main spar to “gusset” ribs.
    Modern CNC machines vastly simplify the process of converting sheets of plywood to airplane parts. They even make multiple different sized rib patterns an easy evening’s work.
    Even if you decide on tapered aluminum wing ribs, CNC machines can route out a dozen different sizes of rib blanks and MDF forming blocks in a evening or two.
     
  11. Apr 22, 2019 #91

    erkki67

    erkki67

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    005534A9-56FB-4963-A891-05B6BEB15D2B.jpeg

    In another thread there is a discussion about the Ultralight Corsair.

    So you might ask what the heck does the Corsair have to do with the Fokker V.40, not much except it’s construction perhaps.

    The Dormoy Bathtub might give a hand on how to build the fuselage too.

    Instead of building a 4 corner fuselage, why not a 3 corner fuselage with carbon tubing or welded or riveted tubes, and keeping the overall design of the V.40.
     
  12. Apr 22, 2019 #92

    cluttonfred

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    Thanks, Erkki, but I think I'd like to keep this a little closer to the original V.40 even if it will certainly diverge in small ways.

    Assuming I wanted to stick with the typical 1918 Fokker two-spar construction for the wing as in the artist's rendering below, what would be the easiest way to ensure a little more torsional rigidity?

    [​IMG]

    I don't really want to go full geodetic, but perhaps diagonal braces between the ribs top and bottom in a zig-zag pattern?

    What about using double X-bracing wires in the outer bays anchored at the top of one spar and the bottom of the other spar?

    It might not be necessary, but I'd prefer a little insurance in that area.

    By the same token, I would probably mass balance the ailerons, elevator, and rudder even if the first two don't have (and don't need at this power and speed) any aerodynamic balance area.
     
    Last edited: Apr 22, 2019
  13. Apr 22, 2019 #93

    TFF

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    Build it as designed or best guess since there are no plans. It’s perfect as is. Improvement rarely are.
     
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  14. Apr 22, 2019 #94

    FritzW

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    You could add torque boxes between the spars like the VP-1 did.

    Is there a problem with the wing? "you can't fix a problem that doesn't exist" With that massive "D" tube and the crazy strut geometry (D-VIII/V-40) it sure looks like it's plenty rigid already.
     
  15. Apr 22, 2019 #95

    Victor Bravo

    Victor Bravo

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    That computer model looks beautiful, but in the last rendering in post #92 it appears that the plywood sheeting on the leading eedge may not go back all the way to the spar. If I am seeing this correctly, that would be an issue IMHO. With a thick wing section, and a plywood skin that is glued solidly to the spar on the top and bottom, you should have a very stiff torque tube / D-section.
     
  16. Apr 22, 2019 #96

    cluttonfred

    cluttonfred

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    If I remember correctly, the original Fokker method used the plywood, spanwise stringers, and the leading edge to maintain the front of the airfoil profile. I read somewhere that the triangular cutouts in the plywood were to reduce wrinkles in the fabric. Note that the spars were not full depth but were inside the rib caps. Using a full-depth spar and D-cell could certainly be done. I could see continuing the plywood to form the little triangle not between the ribs ending at the spars but on the ribs ending at the rib for a classic look. Here is detail drawing of a very similar D.VII wing.

    [​IMG]
     
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  17. Apr 23, 2019 #97

    FritzW

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    With the ply attached to the spars, even with the gaps, it would still give you a nice "D" tube leading edge. But with those big box spars it's probably not required.

    But the scallops lined up on the ribs just looks right...
    IMG_3025.jpg
     
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  18. Apr 23, 2019 #98

    Sockmonkey

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    That strut arrangement looks like it would keep things from warping anyhow even if it did need bracing.
     
  19. Apr 24, 2019 #99

    TFF

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    The Fokker leading edge acted like a sub rib, why they did not go all the way D is a small puzzle. Easier to glue down if not all continues and they did not need the strength. The Falco spars look very much like the D7 and D8.

    The Dr1 spar is a box looking like a Jodel. The Dr1 is essentially two similar spars like a D7 type, front and back spaced that has top and bottom ply boxing them in. 4 shear webs per spar and top ply being drag/ anti drag.
     
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  20. Apr 24, 2019 #100

    TFF

    TFF

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    Note also how wide the cabane strut stance is on a D8. If it was narrow, the center of the spar would have to have more strength; much stronger spar needed at the center. Spaced out, it is broken up into three sections. Load is spread out more.
     
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