P-51C at ~70% scale as ultralight?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by J.L. Frusha, Apr 30, 2019.

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  1. May 29, 2019 #181

    Charles_says

    Charles_says

    Charles_says

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    JL,
    Just curious..(not being snarky)Have you ever built a legal Part 103 vehicle?
    My point is that it is extremely difficult to meet the weight limitation, and stay strong, even when following a set of plans .
    " It is the builder who meets the req's not the designer." this quote is from a very famous Ultralight Designer.
    All the greatest plans in the world can't guarantee a legal 103 vehicle.
    This is even stated in Part 103...
    If you have built one that meets all the requirements, Weight, power,
    stall speed and Maximum speed, you would understand the hurdles.
    You say you've found the simplest fowler flap ever... on a 777.
    The 777 uses the finest titanium, for strength, not some 4130 or 6061-T6
    Yes it may be a simple design, and work perfectly when using titanium.
    However it may not work at all when scaled down and using whatever your wing is made of. You are trying to complicate the design on something that is already as simple as one can get.
    Lots of people think that just because it flies slower and is lighter,
    that the forces acting upon it can be forgotten.

    They certainly cannot!

    If you want to design a 70% P51, why not try doing it in the light Sport class? There you are not hindered before you even start, by the 103 weight limits.In LSA you can get as heavy as 1320 lbs...
    and it has been already done!

    https://www.aerospace-technology.com/projects/titan-t-51/
     
  2. May 29, 2019 #182

    J.L. Frusha

    J.L. Frusha

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    No, I have never tried before. I started thinking at 70%, but it would never go Part 103. Why don't I go for something of a higher rating? I cannot pass a Medical Exam for a pilots license. As far as I can tell, there are 2 people in this forum that know why. Myself and one other. Suffice it to say I have survived something apparently none of y'all has had to deal with in person, repeatedly, and it could kill me at any moment. If you want more, message me, but, on condition that you will not mention it unless it is confirmed that I am deceased.

    Now, for what I WILL publicly admit to, I have a screwed up back..., to the point that I cannot legally find legitimate work. They are also likely to be enough to render me ineligible to pass a Medical.

    Medical Work Restrictions:
    No lifting/carrying over 20 lbs
    No standing over 30 minutes
    No sitting over 30 minutes
    No jumping,bending, twisting, stooping, squatting
    No walking long distances (over 1/4 mile)
    Absolutely no running

    Notice, I said "Medical Work Restrictions"... That means OSHA restrictions. It isn't that I cannot DO these things, I cannot necessarily do them repeatedly, on demand, as any normal job might require... There's a difference. Some days I use a cane. I have been stuck in a wheelchair for a while, due to nerve impingement (surgically corrected), but I have residual nerve damage.

    As for the unmentionable, suffice it to say that the cost of health and liability insurance requirements would make the expenses equivalent to hiring a CEO , even if I started at minimum wage.

    It all adds up to me being restricted to FAR Part 103 and fair-weather flying.
     
  3. May 29, 2019 #183

    J.L. Frusha

    J.L. Frusha

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    [​IMG]

    Red is the moving links, the front one (left) is the driven element.
    Yellow is the main wing mount and link bracket.
    Green is the Fowler Flap mount and link bracket.

    The links are sandwiched in a pair of flap mounts, which ub=nsert into an almost bicycle frame like pair of main wing brackets.

    Pic is a screenshot from the Youtube graphic, posted earlier.

    Note the similarity to a pic from a modelers blog on his build of a 777...
    [​IMG]
     
  4. May 29, 2019 #184

    pictsidhe

    pictsidhe

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    You are struggling with the absolute basics, such as the required wing area. That bodes very poorly for the detail design. While we can quickly advise on wing area, tail volume etc with mental calculations and rules of thumb, we aren't going to do complex maths for you. This project will need some fairly complex maths.

    So, you want this to be an aluminium monocoque? Here's a pdf of my goto book on monocoque stress design. Read it, and you can then decide if you are up to this challenge.

    If you ask a question, or even make a statement on here, you will get a lot of opinions in response. Some of those will be useful, some not. I have posed several questions on here and keeping the thread on track can be harder than herding cats. I have had useful responses, but many often tell me to try something that I have said that I already ruled out. I don't pose many design questions here, it can get tedious ;) You really, really need to learn how to design on your own. Questions are sometimes help for isolated problems, not everything.
    The technical ability of members here varies from halfwit to PhD. Responses vary considerably...
     
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  5. May 29, 2019 #185

    mcrae0104

    mcrae0104

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    I don't. I think you have a dream and you're learning. I think we should have more patience for this and not run off newbies. You are not using your posts as a platform for political commentary, or being recalcitrant about some position that is contrary to junior high school-level science. Maybe you've been a little standoffish, but maybe some people have provoked you a little.

    I hope you will carry on. Doing some learning on your own outside of the forum would be a good idea to avoid flak (check the sticky on books or ask on the forum). These don't have to be engineering textbooks (certainly not at the outset). This can also provide a broader overview so that you're not jumping from design topic to design topic without a vision of the "big picture". I also hope others will remember that there was a time when they didn't know anything about this subject, and there may not have been an Internet back then with which they could've exposed their lack of knowledge.

    Usually learning requires humility on the part of the student (somebody might know something I don't) and patience on the part of the teacher (knowledge is a gift to share at the learner's level and not a bludgeon). It's a two-way street that doesn't adapt easily to this medium.
     
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  6. May 29, 2019 #186

    BJC

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    J.L.:

    As others have already commented, it is difficult to build an ultralight in the form of a typical airplane, much less one that needs to resemble a P-51 with extra (non-functional) structure. Fowler flaps typically are heavier than other flap configurations because they add significant pitching moment that necessitated additional structure to resist, their extension hardware is more extensive, meaning additional weight and drag, and their actuating systems are more complex, also adding weight. You may need to add size and weight to the horizontal stabilizer and elevators, which may then dictate additional fuselage weight, which will necessitate a larger, heavier wing, which will necessitate a bigger wing, which will .... make it extremely difficult to build an ultralight that looks like a P-51.

    I encourage you to calculate the weight of an unflapped wing, a plane flapped wing, a slotted flap wing and a Fowler flapped wing, each of sufficient size to meet part 103 stall speed criteria. And when you look at maximum lift, do so at the Reynolds number for post 103 stall speed and your wing, accounting for the variations as the taper reduces the chord length, then also account for 3-D flow.

    Then let us know which combinations, if any, are light enough to provide an adequate weight budget for the rest of the airplane, fuel and pilot.


    BJC
     
  7. May 29, 2019 #187

    poormansairforce

    poormansairforce

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    A simple hinge with its axis below the flap would suffice and be much lighter.
     
  8. May 29, 2019 #188

    pictsidhe

    pictsidhe

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    I'd suggest throwing in a split flapped wing to that mix too.
     
  9. May 29, 2019 #189

    BJC

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    I knew that you would. My only comment about a split flap for an ultralight, low wing, P-51 configuration (or Hurricane) is that it will require a strong, thin structure in the aft, inboard, upper wing surface to allow reasonably easy access to the cockpit. The older you get, the more you think about such things.


    BJC
     
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  10. May 29, 2019 #190

    J.L. Frusha

    J.L. Frusha

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    As I have said, I will not openly state the health issue that could kill me at any time...

    Suffice it to say that I know from experience that it actually prevents me from even comprehending higher maths. I cannot make the step over to real Trigonometric math. Not even well enough to use the functions on a Scientific Calculator.

    I did not ask for help with the calculations lightly. If there's a problem with my asking for help with something I cannot do, then so be it. This dream dies right here.

    I HAVE plans for ultralights, even for an aerobatic all aluminum biplane that can possibly be built as a light sport biplane, or non-aerobatic ultralight. Aerobatics is beyond my capacity now, so I'm not even trying to consider that. If I absolutely MUST, I can build the UL version. I'd much rather pursue the dream, even of a cartoon-style P-51, than the biplane.
     
    Last edited: May 29, 2019
  11. May 29, 2019 #191

    Tiger Tim

    Tiger Tim

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    JL, I may have missed it but have you done much flying before? I ask because just buildin an airplane (let alone designing it too) is a huge undertaking and it would be a shame to finish and find out you don’t even like it. Not to crap on the idea, it would make my day to see someone’s loving the hell out of their little home brew fighter but are you certain it would make you happy?

    If you think it really will, I echo the sentiment of other posters that getting any plane into 103 is hard. If it were me, I would let someone else do the heavy lifting when it comes to math and do a little cosmetic rework to their proven design. I’d start with a Hummel Ultra Cruiser if I liked metal or maybe a Fisher Avenger or similar if I wanted wood construction. My plan would be to tweak the shape of the tail, wing tips, rear turtle deck, canopy and cowl. There’s a catch: as a general rule of thumb expect every change you make to increase the empty weight of the plane. I wouldn’t try to lighten an existing design, I’m too chicken for that. Weight will be your biggest enemy so all changes will have to be carefully considered before committing to them.
     
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  12. May 29, 2019 #192

    J.L. Frusha

    J.L. Frusha

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    I love flying, but hate TSA... My earliest flight was a trip to Nicaragua as a school boy in the late '60s/early '70s.

    My last lesson flying was years ago and the instructor (student with Commercial, working on his instrument rating) panicked when the base dropped and we went into a grey-out. Nothing quite like the experience of an instructor freaking out and repeatedly saying "Oh my God! We're gonna crash!"

    Told him to shut up and fly the plane - "OMG. w..."
    Told him to shut up and let ME fly the plane - "OMG, w..."
    Told him to shut the **** up, or get out. - He shut up.

    I could see well enough to know where we were and knew the turns for the touch-n-goes, so I didn't have a problem,

    We were doing touch-n-goes with the base at ~3,000 ft, when the base dropped to about 900 and we were in pattern at about 1200.

    I flew the plane, landed a bit hard, had the mechanic do an extra check and then refused to go up with that 'instructor'... Unfortunately, he was the only available instructor. After 6 weeks w/o a flight, I ended up moving because of unexpected news... my ex-GF was pregnant.

    She turns 31 in July... So, yeah, it's been a long time. Last ride was coming back from Seattle, WA., after driving my brothers car up from Texas... maybe 15-20 years ago?

    Dad was a Dr., so we flew regularly for vacations.
     
  13. May 30, 2019 #193

    pictsidhe

    pictsidhe

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    I've already thought about cockpit access. A strengthened TE seems easier than a suitably strong fowler or plain flap. The flap needs to be strong enough to take the pilot's weight then, rather than a small portion of wing TE.
    I can run almost full depth ribs out to the TE if I have a way to transmit flap torque across them. Perhaps I'll put a torque tube in rib holes with flap ribs. The inner surfaces don't need to be smooth or pretty.
    The full size Hurricanes have a TE root fairing and the flaps don't extend to the TE until the joint with the outer panels, so I could add a TE spar behind the flap as well as one for its hinge.
     
  14. May 30, 2019 #194

    pictsidhe

    pictsidhe

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    J.L.
    It's not a problem you asking for help, but it's extremely unlikely that you'll find anyone willing to do the many hours of design tedium for you. Especially with your abrasive nature.
    You should be looking for existing plans that can have a cosmetic job done on them
     
  15. May 30, 2019 #195

    BJC

    BJC

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    Common practice is to board with plain or slotted flaps deployed.


    BJC
     
  16. May 30, 2019 #196

    TFF

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    I think you are going the wrong direction. First Loele tried to sell a pt 103 version of their P51. None made weight but I would not really care. Finding one of those kits would get you in the air way faster. Someone in the Nashville area is sitting on a half dozen kits so they are out there. He is not paying much for them.
    Back to the first sentence, your going the wrong way. You really should be building a two person clone p51. Your are Putting a lot of effort into a real physics problem. It’s not a design problem but a physics problem. The physics are against you. Very hard to do on a budget. If your health is as bad as you say, you probably should not be flying 103. Does not mean you can’t fly, just can’t be logging it. Build a substantial two seater worthy of all this time and just be a perpetual student in one airplane. Once you are an known entity, finding “official “ pilots to ride with you will not be that hard. The right people will migrate around. Build a two seater. Much easier to get the look. It willl have some value for the amount of effort it’s going to take. Completion is going to be your biggest problem, not getting to fly under any rules.
     
  17. May 30, 2019 #197

    BBerson

    BBerson

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    No medical is required for light sport. Just a valid drivers license.
    You only need enough instruction to solo. If you fly a LSA solo only over remote areas no one will be harmed.
     
  18. May 30, 2019 #198

    pictsidhe

    pictsidhe

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    That would make it easier...
     
  19. May 30, 2019 #199

    J.L. Frusha

    J.L. Frusha

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    Driver's license and the student pilot certificate:

    • The Sport Pilot rule allows a pilot to fly light-sport aircraft without the need for an FAA medical certificate. However, a sport pilot must hold at least a current and valid U.S. driver's license in order to exercise this privilege. The only exceptions are for operations in a glider or balloon, which does not require a driver's license.
    • A person using a current and valid U.S. driver's license must comply with each restriction and limitation imposed by that person's U.S. driver's license and any judicial or administrative order applying to the operation of a motor vehicle. That person must also meet the requirements of 14 CFR 61.23(c)(2), which states the following:
      • Have been found eligible for the issuance of at least a third class airman medical certificate at the time of his or her most recent application (if the person has applied for a medical certificate);
      • Not have had his or her most recently issued medical certificate (if the person has held a medical certificate) suspended or revoked or most recent Authorization for a Special Issuance of a Medical Certificate withdrawn; and
      • Not know or have reason to know of any medical condition that would make that person unable to operate a light-sport aircraft in a safe manner.

    ( https://www.aopa.org/advocacy/advocacy-briefs/frequently-asked-questions-about-sport-pilot )




    FAA HomePilotsBecome a Pilot
    Become a Pilot
    Medical Certificate Requirements

    [​IMG]
    • [​IMG]
    When do I need a medical certificate?

    You need a medical certificate before flying solo in an airplane, helicopter, gyroplane, or airship. We suggest you get your medical certificate before beginning flight training. This will alert you to any condition that would prevent you from becoming a pilot before you pay for lessons.

    If you are going to pilot a balloon or glider, you don't need a medical certificate. All you need to do is write a statement certifying that you have no medical defect that would make you unable to pilot a balloon or glider.

    ( https://www.aopa.org/advocacy/advocacy-briefs/frequently-asked-questions-about-sport-pilot )

    ...

    When required, what class of medical certificate must a student pilot have?
    Third-class, although any class will suffice. Medical certificates are designated as first-class, second-class, or third-class. Generally, first-class is designed for the airline transport pilot; second-class for the commercial pilot; and third-class for the student, recreational and private pilot

    ( from : https://www.faa.gov/pilots/become/medical/ )

    -----------------------------------------------------------------------------------------------------------------

    Please note, that includes allowable medications... There are NO dosage limitations. Meaning, despite it being a low-dose medication to control a nervous disorder, I would not pass Class III Medical certification... Enough said. I am stuck with FAR Part 103
     
  20. May 30, 2019 #200

    BJC

    BJC

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    BJC
     

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