How does it fly?

Discussion in 'Hangar Flying' started by BJC, Dec 7, 2016.

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  1. Jan 9, 2017 #41

    choppergirl

    choppergirl

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    Dem ultralights flies purty gud....

    [video=youtube;6f1j1sY1ecU]http://www.youtube.com/watch?v=6f1j1sY1ecU[/video]

    One group of monkies trash, is another girl's treasure...

    Me thinks I've been fishing in the wrong creek
     
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  2. Jan 10, 2017 #42

    BJC

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    OK Boku, time for a pirep for the HP-18 as well as your HP-24.


    BJC
     
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  3. Jan 10, 2017 #43

    BoKu

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    I'm hardly an unbiased source on that. But for the sake of argument:

    The HP-24 originally started out as a kind of "super HP-18." My thinking was to address the HP-18's limited downward visibility, awkward ergonomics, and mediocre control system design with a new forward fuselage. The original plan was to retain the HP-18's aluminum monocoque aft fuselage and V-tail, and do some sort of Jiran-style moldless foam core trick for the wings.

    However, I really wanted to go a step beyond the HP-18 in terms of its disparity with what you could expect from a new-ish European racer.

    * Taking the canopy off and setting it on the ground next to the glider is something nobody should have to do. I wanted a nice convenient nose-pivot canopy.

    * Breaking out wrenches to connect the ailerons is a complete non-starter. I felt an ethical imperative to implement automatic control hookups. The math goes something like this: Every year on the US contest and cross-country soaring scene, there are about 2000 assembly events where folks hang wings to go fly. About 1/1000 of those assembly events embodies a critical control connection error. About 50% of those critical errors are followed by a fatal crash. That wasn't gonna happen on my watch.

    * A market survey showed that for everybody who loved 90-degree landing flaps for gliders, there are two potential customers who want nothing to do with them. It was clear that if I wanted to sell gliders, they'd have to have Schempp-Hirth or similar airbrakes.

    * The HP-18 sliding side stick is an ergonomic abomination that most learn to accept, but nobody really likes. Having already designed and marketed a center stick retrofit kit, I knew that my glider would have a conventional control stick, and that extra attention would go into having low slop and friction.

    * As much as I love the V-tail look, they offer no particular aerodynamic advantages, and the fold/unfold mechanism can be touchy and prone to wear and slop. The Europeans had shown that a removable T-tail stabilizer can be easier to assemble and rig than any V-tail I'd seen, so I went with what folks are familiar with and accept.

    * With the HP-18, in order to make a pitch input, you move two 12-foot long aluminum tubes; each tube goes through six push-pull tube guides consisting of holes through bare nylon plates. Skreek! Skronk! I knew I needed much lower system friction. I eventually settled on a system where every single push-pull tube guide is a linear ball bearing, and all but a few pivots have low-friction ball bearings. There are eighteen linear ball bearings tube guides in each glider; eight in the fuselage and five in each wing.

    * There is often a perception that if you have a rugged metal glider, you can tie it down out in the weather, and you won't have to rig/derig for each flight. However, a dozen years campaigning an old HP-11 showed me that an ASW20 driver could get their ship out of the trailer, rigged, and onto the flight line faster than I could get my glider untied, get it over to the wash rack, and hose the dust off of it--and with less effort and logistics. So I knew that my glider was going to have the kind of pin-and-thumbscrew, no-tool assembly that the Europeans had.

    * Somewhere along the line, I costed out the parts of the HP-18 wing spar, and found that there was pretty much no way to get them made cost-effectively any more. I decided that I would go with a carbon fiber pultrusion-based wing spar, and engaged Jim Marske to help me develop the tooling and design for the spar. For comparison sake, the aluminum parts for the wing spar for one HP-18 wing weigh about 50 lbs. One HP-24 wing spar weighs about 20 lbs.

    * After trying several different one-off composite methods, I eventually threw in the towel and invested in full female molds for every part of the glider. The wings and horizontal are carbon/foam sandwich, the flaps, elevator, and rudder are kevlar/foam sandwich, and the fuselage shell is pretty much all carbon with foam core only in the vertical fin. The rudder contains a dipole com antenna; it is Kevlar mostly just to let the radio waves out.

    Okay, how does it fly? I can honestly say that it is probably the sweetest flying glider I have ever flown, right up there with the LS4, which is renown for good handling. If you can fly a Schweizer 1-26, you can fly this thing--the hard part is remembering the undercarriage. Not used to flaps? No problem; leave them in the 0 setting and you'll do fine.

    We left a little bit of performance on the table to ensure a fat margin of static stability, and it has definitely paid off. In It has great pitch stability and handling, and a very natural-feeling stick force/g gradient. The full-span flaperons make it easy to keep the wings level even on a downwind takeoff, and the comfortable office and big bubble makes it easy to see what is around you. It thermals like its on rails, and the unballasted gross stall speed of about 40 kts with good roll control down to the stall means you can stay up easily even in light conditions.

    By contrast, I never really like the HP-18 flight characteristics. The sharp-nosed Wortmann airfoil yields a sharp, unforgiving stall, and loses a lot of performance when wet or buggy. The controls feel vague at best; more like a suggestion box than a command input. The landing flaps are great fun, but the somewhat indifferent control system design is not exactly confidence-inspiring.

    Thanks, Bob K.

    Edit Add: That's not to say that the HP-18 is a bad glider. In its day it offered unparalleled bang for the buck, and its aerodynamics were based on the best available information at the time. But we have come a long way since those days. Now it is widely accepted that the thing to optimize is not the sailplane's maximum performance, but rather the pilot's enjoyment of the overall soaring experience from arrival at the airport through disassembly and stowage after the flight. Making the glider enjoyable to fly makes it easy to fly well throughout the day, and leaves you in better mental and physical condition during the critical approach and landing phase. And that makes it more likely you will perform better the following day.
     
    Last edited: Jan 10, 2017
  4. Jan 10, 2017 #44

    BJC

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    Thanks Bob.


    BJC
     
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  5. Jan 10, 2017 #45

    TFF

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  6. Jan 10, 2017 #46

    don january

    don january

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    built 1964, power plant 125HP lycoming (O-290-G) W-Span 25 ft. W-area 108 sq.ft. 900 lb. empty, Max T-O weight 1.500 lb. Rate of climb 1.000 ft. min. Is of all wood construction, Retractable landing gear. Two Place side by side. The CA-65A is similar to the 65 other then swept vertical tail surface and built of all metal, and will take engines 108-150 HP. Max speed on the all metal is stated at 174 mph with the 150 hp engine. Designed for +9g and -6g I believe it had a folding wing option.
     
  7. Jan 10, 2017 #47

    fly2kads

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    I still want to see input from Fritz on this question, as well as anyone else who may have flown one.
     
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  8. Jan 10, 2017 #48

    lr27

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    How about the Pioneer II or other plank style sailplanes?

    I'm afraid I can only advise re model airplanes. Mostly, but not entirely, RC gliders. Don't laugh too much. Imagine flying a sailplane with an aspect ratio of 17, but without any instruments or even seat of the pants feel. If I ever build something full scale, I hope I can find someplace to test it out without having to be inside at first!
     
  9. Feb 3, 2017 #49

    BJC

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    Pou du ciel

    Just watched the video that Matthew posted, HM 293 Flying Flea (Pou du ciel) in action.

    It looks like it would be lots of fun to fly, but I have always had the impression that they have some real quirks, as well as a poor safety record. Note that I said impression; I am hoping that one or more of you will reply with some facts or first-hand experience.


    BJC
     
  10. Feb 9, 2017 #50

    Twodeaddogs

    Twodeaddogs

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    A VP-1 is very stable, to the extent that you can make it turn by sticking out an arm, without touching the controls. They are heavy for what they are, but a lightly built one is just great fun to fly. Care has to be taken for takeoff and landing as they are not overpowered and tend to have a low climb rate; they are NOT STOL aircraft, but will get off the ground (when they are good and ready) in under 250 yards. I have operated one out of 400 yards. Despite being stable, they are quite manouverable and have a tiny turn radius, if you are prepared to get the wing down and keep the power up. Ailerons are heavy and need speed to be really useful; rudder is heavy but effective, pitch is also very effective but is light. Most are flown behind an 1834cc VW, but there are several with Rotax 582s and composite props (huge performance increase!), some with Subarus, small Continentals and even a few with VWs up to 2200cc. They are physically big, with a wide span and chord, that surprises people but they are easy to manouvre by hand and under power. VWs are notorious icers so you'd have to apply carb heat upon any reduction of power, especially (and this is etched in stone, by the way)for approach and landing. On approach, you must maintain an accurate approach speed and keep a bit of power on, as they can develop a sink rate that you don't have the power to climb out of. all that being said, they are great fun to fly and have a dedicated band of followers, self included.
     
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  11. Feb 9, 2017 #51

    BJC

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    Thanks, tdd.

    Now, anyone have experience with another VW powered single seater, the Pazmany PL-4A? IIRC, it has a PSRU, so it may have more thrust.


    BJC
     
  12. Feb 10, 2017 #52

    pictsidhe

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  13. Feb 10, 2017 #53

    Pops

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    My old flight instructor built one and flew it several years until he was to old to fly and gave it to someone down you way. Powered by a 1600 cc, VW engine.

    Read next months issue of Kitplanes on the changes to fix the quirks of going pitch unstable.
     
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  14. Feb 10, 2017 #54

    TFF

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    Battler Britton, BJC and Pops like this.
  15. Feb 10, 2017 #55

    Pops

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  16. Feb 10, 2017 #56

    Twodeaddogs

    Twodeaddogs

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    Just like a firework; light blue touch paper and stand clear. do not approach if fuse goes out.
     
  17. Feb 14, 2017 #57

    BJC

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    There are some brief descriptions of how several WW I aircraft fly in the February, 2017, issue of Sport Aviation magazine.


    BJC
     
  18. Feb 15, 2017 #58

    Twodeaddogs

    Twodeaddogs

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    A lot of the WW1 aircraft were quite marginal, by today's standards, and required constant handling. I recall one flight test of the Shuttleworth Collection's LVG, which was politely damning of it's handling, compared to a Bristol Fighter.
     
  19. Feb 22, 2017 #59

    BJC

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    I may have posted this link before, but it offers so much interesting information about WW-II aircraft that it is worth posting here. Lots of real information about speed.

    http://www.wwiiaircraftperformance.org


    BJC
     
  20. Mar 28, 2017 #60

    BJC

    BJC

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    Anyone here that can tell us how the Thatcher CX-4 and or CX-5 fly?

    Thanks,


    BJC
     

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