Some design musings

Discussion in 'Hangar Flying' started by rtfm, Jan 14, 2014.

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  1. Jan 21, 2015 #341

    delta

    delta

    delta

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    I'll be using "tub and fabric" in my construction. I think they're kind of sexy, but I may be somewhat biased...
     

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  2. Jan 22, 2015 #342

    cluttonfred

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    Part Facetmobile, part Arup, I like it.
     
  3. Jan 22, 2015 #343

    rtfm

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    Hey Mitja - Chill mate...
    This thread is entitled "Design Musings". Shooting the breeze. Design small talk. Nothing else.

    "Useless work and time"? "to end in a storage somewhere unfinished."? Be fair mate... My journey might not be simple and clear - but little of it is useless, and the fact that my build is in storage is because I have temporarily run out of money. I'm actually a bit pi*sed off at your comments. Play fair...

    Sheesh...
    Duncan
     
  4. Jan 22, 2015 #344

    cluttonfred

    cluttonfred

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  5. Jan 22, 2015 #345

    delta

    delta

    delta

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    I like it too. Thanks man. I keep coming back to this one despite the tail dragger configuration and the lack of visibility at ground angle of attack. It's going to be scary for me when it's time to test it out. I hope to have a BRS by then but I'll have a back pack for sure. I'm making it out of carbon fiber golf club shafts, powering it with a mz202, and covering it with Dacron. I plan to incorporate a wing folding or detachment so I can trailer it to a dry lake bed for testing.
     
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  6. Feb 4, 2015 #346

    rtfm

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    Hi again,
    I'm musing again... All that discussion about Apollo's canard design got me doodling in X-Plane again, and here's where my musings have taken me, Just a first cut, mind you, so don't be too harsh...

    One thing which is a bit odd is the stepped tail. I did that by accident, and kinda liked the look, so I left it. I know it's not aerodynamically optimal, but hey - this is a pleasant cruising 100hp 2-seat Side-by-side Sunday cruiser. It's not meant to be a racer... And it will certainly catch the eye. The steps could even be used as low pressure areas for exhaust extraction.

    I've used the design formulas I worked out for the Razorback tandem wing, paid attention to the two downwashes, specified airfoils which will ensure the canard stalls first. I've even fitted flaps to the rear wing. Oh, and I decided to stick with a "proper vertical fin with an all-flying elevator. I don't trust those wing-tip rudders...

    (If I fudge the CG) my design spreadsheets say it will fly. In X-Plane it flies like a dream. What's not to like for an afternoon's musing at the keyboard? Perhaps turn it into a pusher? With a V-tail? That ought to be fun...

    Enjoy - and comments always welcome.

    Duncan

    RTFM Canard4.jpg RTFM Canard2.jpg RTFM Canard3.jpg RTFM Canard1.jpg
     
    Last edited: Feb 4, 2015
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  7. Feb 4, 2015 #347

    timberwolf8199

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    The sweep on the main wing looks a bit excessive to my eye. I like it...but I also gravitate to non-traditional designs.
     
  8. Feb 4, 2015 #348

    Aesquire

    Aesquire

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    That is a dead ringer for the Hirt Trio. The canard on his was smaller with no control surfaces, and his wing shoulder high and forward swept. 8 degrees. Tail was lower too, positioned out of wing wake clean and with flaps.

    April 1995 Kitplanes magazine. Given a very good review with an O-320.

    Just happen to have that issue in the reading room. I cycle back issues through to re-read the Wind tunnel articles and dream.
     
  9. Feb 4, 2015 #349

    BJC

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    I call that room "the library." :) I grew up with two brothers, and that was the only place to have peace and quiet to read, especially technical stuff.


    BJC
     
  10. Feb 4, 2015 #350

    Aesquire

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    The Trio was memorable because there have been few successful 3 surface planes.

    The B-1b has a small canard used for gust relief at low altitude high speed flight but it's computer controlled.

    I suppose I could say your musing is a distant ringer to a Long EZ with a tractor prop and tail ;)

    Btw... I like it. Perhaps too much sweep unless you put the engine behind the cockpit like a Stemme. ( on my short lust list if I win the lotto )
     
  11. Feb 4, 2015 #351

    cluttonfred

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    My heart and eyes love it, but my brain says that the CG is way to far forward for that wing planform. The canard would be carrying more than half the weight with only a fraction of the area, so its loading would be very high and the main wing would be doing very little. If it were me, I'd duplicate the rear wing forward to make it a tandem, lose the tail surfaces, clip the outer foot or so from the rear wing and add endplate rudders to make it a Mauboussin-type tandem with no tail at all.
     
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  12. Feb 4, 2015 #352

    rtfm

    rtfm

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    Hi,
    The Hirt Trio - I could only find a single picture of it. And not a great one for seeing its lines. Any idea where I could find others?

    Duncan
     
  13. Feb 4, 2015 #353

    rtfm

    rtfm

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    HI,
    As I said in the first post - I had to fudge the CG in X-Plane (and in the SS) to make it fly. Actually, if I put the CG in the vicinity of the cockpit so that adding a passenger wouldn't make too much difference, the main wing has to be swept forward almost 20 degrees. I tried that, but it looks plain silly.

    I also tried it as a pusher, which sorts out the CG issue quite nicely. But pushers? Meh... I'm not so sure...

    Duncan
     
  14. Feb 4, 2015 #354

    delta

    delta

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    As long as we're just musing...
     

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  15. Feb 4, 2015 #355

    rtfm

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    I'm about to turn in for the night, so here's a revival of an earlier design I was doodling with some time back. This time I've done a bit more work on the wing placement, the actual computed CG and have been playing with flaps/elevators and aileron placement. Currently deploying flaps produces a nose-down moment, so I have some more work to do. Oh, and the artwork is a bit shonky too.

    I think this one might actually have some merit for a two-seater (100hp).

    Duncan

    RTFM Diamond wing 1.jpg RTFM Diamond wing 2.jpg RTFM Diamond wing 3.jpg
     
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  16. Feb 4, 2015 #356

    Aesquire

    Aesquire

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    That Trio is a hard to find airplane.... I too have found just the one picture

    http://www.abpic.co.uk/photo/1101818/

    Although I can't believe I forgot the Piaggio p-180 Avanti. Not quite in my budget as a home built, though.
     
  17. Feb 5, 2015 #357

    rtfm

    rtfm

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    A final effort for now...

    I got to thinking how I would build the V-tail, and it seemed like a nightmare to me. So I reverted to a "standard" tail, and put an all-moving elevator at the top. I did this not because it looks cool (it does), but because I wanted it as far from the CG as possible to maximise its lever arm. And because the tail rakes backwards (yes, I know a number of you don't like this, but what the hell...) putting it on the top made sense. It also puts it out of the way of the wing downwash as much as possible. In fact, it gets less than 20% of the downwash angle experienced at the wing TE.

    So, now I have a cross between a tandem wing design and a biplane.

    Front wing:
    15ft span
    Rear sweep 18deg
    Wing area 30.2ft^2
    Airfoil: Eppler E290
    Incidence: 3 deg

    Rear wing:
    15ft span
    Fwd sweep -18deg
    Wing area 30.2ft^2
    Airfoil: AS5054 (selected because it stalls 2 deg later than the Eppler)
    Incidence: 2 deg (giving me an effective 3 deg "safety margin, even taking downwash into consideration)
    Downwash angle at rear wing at the stall: 8.6deg; Downwash at rear wing: 2.15deg

    Stall: 43kts clean

    Power is still the 50hp VE Big Twin (I have yet to test ths claim, but suspect it is overly optimistic)

    Cruise (80% power) should be a respectable 120kts

    Well, there you have it. The latest product of a mind slowly turning to custard while I continue looking and waiting for work.

    Duncan

    PIX:
    (1) The F1-X1 on the drawing board
    (2) On the runway
    (3) Airborne
    (4) On the way to New Zealand...

    F1-X1 on the drawing board.jpg F1-X1 on the runway.jpg F1-X1 airborne.jpg F1-X1 on its way to NZ.jpg
     
  18. Feb 11, 2015 #358

    rtfm

    rtfm

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    Hi,
    I'm at it again. This time I'm inspired both by HITC who has encouraged me to think along the lines of a Part 103 design, because in the horrendously overcrowded marketplace for light aircraft, there seem only to be two niches - STOL and Part 103

    (I'm not sure I mentioned this on the forum, but I had to store my entire workshop in a container and park it on an industrial lot - together with the plugs. Unfortunately, the plugs couldn't fit inside the container, so I had to take my chances and store them on their stands next to the container. I covered them with tarpaulins and plastic sheeting, and just had to hope for the best. Then along came the biggest storm Brisbane has seen for 30 years. Huge hail smashed everything in its path - including my plugs. Water then got in, and the underlying MDF started to swell. Long story short - the plugs are past redemption.)

    I still am not in a position to start building again - but at least we have secured a new place to live, which has one one but two double garages. The second of the two is going to be my workshop. We move next week. But the thought of starting all over again is heartbreaking - but the one good thing is that I have learned some very valuable lessons about how to build a plug. Next time round it will take weeks, not years.

    And hence my thoughts turning once again to designs.

    After having read all 44 pages of the Electric Lazair thread on the RC forums, and speaking to HITC about series hybrid electric planes, I spent most of today playing around with a possible Part 103 series hybrid concept which could be built for under $10k (including engines). It's basically a reworking of an earlier push-pull concept I was playing around with some time ago - but on a very much smaller scale. I think it's cute...

    A 20hp ICE goes up front
    A 15hp or so electric motor on the rear
    Both run flat out for T/O and climb - which should be brisk
    The ICE then does all the honours during cruise, as well as doing double-duty charging the batteries. Charging should take (I'm led to believe) about half an hour, meaning that the batteries should be fully charged for emergencies in prettyshort order. I like the idea of electric power on standby should the ICE quit.

    Wing span: 28ft
    Wing area 105 ft^2
    Stall: 28 mph (clean) - but I'll fit Junkers flaps I think
    Cruise: 75kts
    Empty weight (including batteries): 265lbs

    So I have some more work to do on the speeds and weight fronts - but I'm getting there. I still need to estimate the CG more accurately, and check all my math. But I think it is reasonably accurate as it stands. The fuse will be made of 4mm cork/glass sandwich. Wings D-Tube (2mm cork sandwich) and Depron aft of the D-Tube. Carbon (graphlite) spar.

    Looking for: decent 20hp motor. I hate two-strokes. Might have to just bite that bullet though. Anyone know of a decent 20hp Rotary? Even on paper it is difficult to meet the weight limit. Building will add many pounds I fear...

    Enjoy - and (as always) comments welcome. These are my first drawings - so they're a bit rough...

    Duncan

    F1-e1 on runway.png F1-e1 on runway2.jpg F1-e1 airborne2.jpg F1-e1 airborne.jpg
     
  19. Feb 11, 2015 #359

    Jay Kempf

    Jay Kempf

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    Oh come on Duncan,

    That is way to conservative and sane. What happened?
     
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  20. Feb 11, 2015 #360

    Hot Wings

    Hot Wings

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    It's called experience.
     
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