Articles / Blog - Ultralight Design Concepts

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by DaveD, Oct 21, 2017.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Nov 2, 2017 #41

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Topic for today is controls...
     
  2. Nov 2, 2017 #42

    proppastie

    proppastie

    proppastie

    Well-Known Member

    Joined:
    Feb 19, 2012
    Messages:
    3,885
    Likes Received:
    1,133
    Location:
    NJ
    I was thinking ...... does the tapered wing twist at high AOA and is it in favorable direction for the stall?
     
  3. Nov 2, 2017 #43

    cluttonfred

    cluttonfred

    cluttonfred

    Well-Known Member

    Joined:
    Feb 13, 2010
    Messages:
    6,446
    Likes Received:
    2,287
    Location:
    World traveler
    This is a really great series, fun to read and very engaging, thanks for sharing.
     
    DaveD likes this.
  4. Nov 2, 2017 #44

    autoreply

    autoreply

    autoreply

    Moderator

    Joined:
    Jul 8, 2009
    Messages:
    10,732
    Likes Received:
    2,542
    Location:
    Rotterdam, Netherlands
    Yes.

    Lowering the flap lowers the stall angle of attack (if you don't use sluts or LE flaps). That gives "natural" protection against tip stall.

    That almost got me once, doing a high-speed pass and aggressively pulling up I had a really aggressive wing-drop during an accelerated stall with full negative flaps (-7 degrees, which puts the ailerons at about -4 degrees). If you simply always pull a modest bit of flaps below 100 kts, otherwise "flapped tip stall protection" should be fine.
     
    DaveD likes this.
  5. Nov 3, 2017 #45

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Burning the midnight oil tonight!

    Trim Tabs are today's topic.

    Cheers

    Dave
     
  6. Nov 4, 2017 #46

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Giggi likes this.
  7. Nov 6, 2017 #47

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Propeller theory for beginners! Trying to put prop design in simple terms is a bit like trying to put nuclear physics in simple terms... in other words, quite a challenge. But I do like a challenge.

    https://ultralightdesign.wordpress.com
     
    Giggi likes this.
  8. Nov 8, 2017 #48

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    A couple of articles on Spinning and Design for Spin Prevention are now posted
     
    Giggi likes this.
  9. Nov 8, 2017 #49

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Loading and V-n diagrams will be up in a couple of hours.
     
    Giggi likes this.
  10. Nov 11, 2017 #50

    akwrencher

    akwrencher

    akwrencher

    Well-Known Member HBA Supporter

    Joined:
    Oct 16, 2012
    Messages:
    1,116
    Likes Received:
    402
    Location:
    Gustavus, AK
    Many thanks for your efforts. That's a lot of writing.
     
    Giggi and DaveD like this.
  11. Nov 13, 2017 #51

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Giggi likes this.
  12. Nov 14, 2017 #52

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    For those needing structure I'll try and introduce some! I've added an index to the blog:

    Index

    And for the rest of you, here's where I'm up to (Gust Loading has just been posted):

    Introduction - In The Beginning
    Designing My Own - Design Notes
    Configuration & Layout - Configuration & Layout
    Wing Shape - Wing Shape
    Aerofoil Selection - Aerofoil Selection
    Drag - Such a Drag
    Materials - Material World
    Flaps - All in a Flap
    Landing Gear - Happy Landings
    Stability - Introduction - Are You Unstable?
    Stability - Longitudinal - Perfect Pitch?
    Stability - Weight & Balance - A Weighty Issue
    Stability - Lateral & Directional - Thinking Laterally
    Fuel Systems - More Fuel You?
    Cooling - Keepin’ Cool
    Controls - Control Freak
    Trim Systems - Just a Trim
    Cockpit Design - The Workshop?
    Propellers - Prop Me Up
    Spins - All in a Spin
    Design for Spin Safety - The Spin Doctor
    Aircraft Loads - Shouldering the Load
    Limit Loads for Design - Feel The Force
    Gust Loading - Gone With The Wind

    Enjoy!
     
  13. Nov 16, 2017 #53

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    In response to some feedback I've gone back through my earlier posts and linked the images to the original "supersized" versions. So if you were having trouble with the diagrams being too small to read easily, you can now click them for a big version:

    Article Index

    Secondly I've posted a couple more:

    Biscuits-Jelly-Nylon-Steel - This is a discussion about the four pillars of engineering: Stress, Strain, Strength and Stiffness (the four 'S's). This is a personal bugbear of mine, everyone who ever thought about designing anything (even "eyeball" engineering) should have a grasp of these concepts! You don't need to be a professional engineer to realise this stuff is fundamental (Oh and for those not of an English persuasion, "Biscuits" are cookies!)

    And:

    The Path To Enlightenment - Load Paths, vitally important for any design and require an understanding of "Stress, Strain, Strength and Stiffness"...
     
    akwrencher and Himat like this.
  14. Nov 19, 2017 #54

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    akwrencher likes this.
  15. Nov 19, 2017 #55

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,201
    Likes Received:
    2,401
    Location:
    Port Townsend WA
    The four automatic slats on the Helio operate independently (no interconnection mechanism), depending only on local angle of attack. (Flaps, aileron, yaw, etc.)

    Good summary of the various and confusing "P effects".
     
    Last edited: Nov 19, 2017
    DaveD likes this.
  16. Nov 20, 2017 #56

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    Wow, that's interesting! I assume it must have enough aileron authority to counteract an asymmetric slat deployment even at low speed. The fact there are two separate slats on each wing probably helps.
     
  17. Nov 20, 2017 #57

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,201
    Likes Received:
    2,401
    Location:
    Port Townsend WA
    I don't think there is any asymmetric lift to deal with. They automatically balance the lift. Need to ask a Helio pilot how they work. But as I recall they pop in and out no problem on the ball bearing rollers.
    I have removed them for painting. But never flew in a Helio.
    The Helio ailerons are wide chord but only about 4’ long because of the near full span flap. They have an effective spoiler (interceptor) behind the main spar to augment roll.
     
  18. Nov 20, 2017 #58

    DaveD

    DaveD

    DaveD

    Well-Known Member

    Joined:
    May 28, 2010
    Messages:
    320
    Likes Received:
    152
    Location:
    Perth, Western Australia
    You're right, and my previous post was poorly worded! Slats mostly push up the stalling aoa rather than significanly increase lift at a fixed aoa. So the concern from an asymmetric deployment is presumably having one wing stall at a lower aoa than the other and causing an asymmetric stall (in all probability at low speed and close to the ground!!)

    Trying to save a wing drop with aileron is a bad idea, but if the Helio has spoilers for augmenting roll (something else I didn't know!) then the spoilers may be able to counteract an asymmetric slat deployment even at stalling speeds.
     
  19. Nov 20, 2017 #59

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,201
    Likes Received:
    2,401
    Location:
    Port Townsend WA
    I interviewed the Helio display pilot last summer at Oshkosh. He said it just doesn't stall! No wing drop. No spin.
    Really, everything the NTSB wants to prevent LOC, the number one goal.
    So I went straight to the NTSB booth and told them to check it out. They both had no clue what I was talking about.
     
    DaveD likes this.
  20. Nov 20, 2017 #60

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,727
    Likes Received:
    3,321
    Location:
    Memphis, TN
    No stall does not mean it can't sink at 1000ft a min. You still have to fly it.
     

Share This Page



arrow_white