Adding a couple inches in the middle

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Woodwings, Apr 11, 2019.

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  1. Apr 11, 2019 #1

    Woodwings

    Woodwings

    Woodwings

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    I'm considering a Druine Turbi, and some advice given in response to my intro post was to make sure I'd fit before launching into a project. Makes scary sense.

    I acquired a set of plans that show the inside width of the rear cockpit as 576mm, or 22.6 inches (the frame behind the cockpit is 610 mm, with a 17 mm longeron on each side). That's about the width of my shoulders. I wouldn't want to be rubbing on the sides, and also would need some more room if wearing a jacket.

    My question for those of you with design experience is whether I would be opening an unjustifiably big can of unintended consequences by adding somewhere between two and four inches to the center of the spars and fuselage to create a little more clearance.

    I really like this design, but if I couldn't be reasonably comfortable I should keep looking for a design that suits me better.

    Thanks.
     
  2. Apr 11, 2019 #2

    don january

    don january

    don january

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    As the builder of a experimental aircraft you can do what you want and at the end of your build receive a AWC (Air Worthiness certificate) that is one of a few things to stay focused on. Planes such as the KR-2 and the Taylor mono have been widened successfully but if at all possible shoulder width and body weight would be the better option.;)
     
  3. Apr 11, 2019 #3

    Woodwings

    Woodwings

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    I'm working on losing a little extra that I've been carrying on my front, but I have no idea how to make my shoulders narrower. They are what they are.
     
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  4. Apr 11, 2019 #4

    TFF

    TFF

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    I would not change the spars. I would lengthen the fuselage 2-3” back and add 1” to the front. Recline or push back the bulkhead at the back of the seat a few inches. A little wider too as long as you don’t change how the wing is mounted to the fuselage, just spread out an inch or two.
     
  5. Apr 11, 2019 #5

    blane.c

    blane.c

    blane.c

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    "Change one thing, change everything" is the saying.

    I got the same front and shoulder challenge's. I want something comfortable. Not something I need to be greased to get into, so I understand. I looked at a Pietenpol and I won't fit, I could probably with care figure out somehow to get in one but stay in it for hours, there is no doubt I would cramp up all over the place and trying to stretch out to relieve the cramping may break something. Flying is about enjoyment not enduring agony.
    The old Cessna Bamboo bomber had plenty of room, some of the Stinsons are pretty roomy, The Aeronca Chief might work as a single seater if you could get plans for one but even changing it to a one person you are back to change one thing, change everything.

    I guess I want a 1 1/2 person airplane if I was just to have a personal ride. and just making something a few inches wider like 24 1/2" or 26 1/2" ain't going to cut it, I mean how you going to reach around in that to find your bologna sandwich? You need more like 3 feet wide to be able to reach around for your lunch and your charts and to be able to crank the trim wheel without busting something.

    But anyway it is going to be faster to spend the time to find something already figured out than to modify something like that.
     
  6. Apr 11, 2019 #6

    blane.c

    blane.c

    blane.c

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    Some specs on the Bearhawk comparing it to a Super Cub, look at the cabin width (it's a tandem), so sure it ain't 3 feet wide but it's closer to 3 feet than 26".

    BEARHAWK SOME SPECS.PNG
     
  7. Apr 11, 2019 #7

    Riggerrob

    Riggerrob

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    You are suffering from the dreaded “yachtsmans’ disease.”
    Hah!
    Hah!
    “It would be perfect if the cabin was slightly longer .......”
    Cabins are always the most expensive part of any boat.

    Seriously, many of us are now larger than the mal-nourished (immediately after World War 2) Frenchman who designed the original airplane.

    If you already have the plans, build a mock-up of the cockpit. Mount your mock-up in front of your TV. Sit in the mockup for an entire football game. Note cramps and pressure points.

    Add spacers and repeat the process until comfortable.

    Review weight and balance with the longer cockpit.

    Review stresses on the wider wing centre section.

    Repeat until numbers make sense.
     
    Last edited: Apr 11, 2019
  8. Apr 12, 2019 #8

    Woodwings

    Woodwings

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    I don't have the background and math skills to quantify and analyze stresses.

    Of course, my main intent is to end up with a safe airframe. If fiddling with the design based on something as subjective as my thoughts of "that looks reasonable" would create more problems than it solves, I may be best off not going down that road.
     
  9. Apr 12, 2019 #9

    blane.c

    blane.c

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    It ain't just the cabin and the spars, how about the landing gear? And the firewall? I mean if all you had to do was "Blister" the seating area there would be a lot of strange looking Pietenpol's and Hatz's flying around I am sure.
     
  10. Apr 12, 2019 #10

    blane.c

    blane.c

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    I think someone is doing a 1.2 sized Pietenpol? Maybe if you can find that it would answer some questions about the Turbi.
     
  11. Apr 12, 2019 #11

    Tiger Tim

    Tiger Tim

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    Original plans for the Turbi or Falconer plans? I wouldn't be at all surprised if Falconer stretched the plane a bit when he re-drew it, so that may be worth looking into.
     

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