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  1. larr

    Cantilever parasol wings?

    I think there is a tendency to over estimate that effect of wing sweep at small angles. For example, the 747 has greater sweep than the Antonov and still has dihedral. Dutch roll is an unfortunate side effect of wing sweep, so that airliners all have yaw dampers. Boeing has always used large...
  2. larr

    Cantilever parasol wings?

    Generally, I agree with Clutonfred. It should be 'traditional' in both looks and construction. Even so, there is a lot of wiggle room. Mossie's 3D models are quite nice, but as he stated they are what he imagines they should be. There is no way of knowing the exact construction details. At the...
  3. larr

    Boeing - Design Issues...

    This is from the NTSB report on the Aloha incident: NTSB assigned a high degree of responsibility to the FAA for lax oversight and generalized bumbling. Somehow, that gets left out of the usual discussions about this incident. Claiming that the "real reason" is being hushed up is peculiar. The...
  4. larr

    Replica home builts

    No. Boring History Moment Hugo Junkers used his windtunnel to determine that a thick section wing did not have a significantly different drag profile to a thin section wing, a fundamental fact in the development of a cantilever wing. During WWI Idflieg was unhappy with Junkers ability to produce...
  5. larr

    "Intersting" electric homebuilt

    Didn't Einstein say the difference between genius and stupidity was that genius had limits?
  6. larr

    Other purposes of landing wires.

    Well, on the old biplanes the wing to cabane attachments were hinges. The 'landing wires' were used to set the diehedral. Individual pilots had their own preferences. Also remember, the wings, wires and struts make a complete truss system. You have to consider all the interactions.
  7. larr

    Hurricane Mk103

    I always wondered if there was a place in ultralight construction for Alucabond or Dibond - stiff and light stuff. It can't be bent much but that is sort of the point. Maybe good for a box type fuselage with coroplast to get the outside shape (sort of like the real thing.) Engine-wise what...
  8. larr

    Norms flying Boat

    Glad that you're OK, although it's a sad end to a long time project. Your description of the crash sounds more like a stall though. It's great that you had an idea and saw it through. It's also great that you knew enough, or knew when to ask in order to get it done. Overall, I think you should...
  9. larr

    LSA stall speed

    As usual, didn't respond when I should have. Several important points to make: 1) CAS is derived from the impact pressure on the aneroid capsule. 2) Impact pressure is the sum of velocity and density (keeping in mind that density varies with altitude and temperature.) So KCAS is a particular...
  10. larr

    J3 Kitten Reliant SX version and a tall / heavy pilot?

    Well, these are the specs from all-aero Reliant SX Speed max: 100 mph. Cruise: 75 mph. Range: 120 sm. Stall: 31 mph. ROC: 1100 fpm. Take-off dist: 50 ft. Landing dist: 150 ft. Engine: Rotax 447, 40 hp. HP range: 40-50. Fuel cap: 5 USG. Weight empty: 285 lbs. Gross: 600 lbs. Height...
  11. larr

    Deltic turbo diesels (Triangular engines with three banks of opposing cylinders)

    Well, so again my $0.02. The OP tried to make a logical case between the Deltic Diesel and modern Turbodiesels. There isn't one. Deltics were piston ported, blower scavenged, opposed piston two-stroke diesels. Turbodiesels are turbocharged four stroke engines. It is not possible to draw any...
  12. larr

    Hurricane Mk103

    A really, really interesting project. Personally, I think 75% would be best - but it's going to be tough to make the weight. At 75% it's more than long enough but too tight at the shoulders: Trying to get compound curves out of coroplast is pointless. If you used it for formers and stringers...
  13. larr

    Cracker Jack 2 LSA from Pete Plumb / Wood Wing Specialty

    Thanks for the reply! I was also wondering about the ailerons - if there's no rear spar what do they attach to?
  14. larr

    Q regarding air velocity immediately aft of prop disk

    You can't be serious. You are saying, basically, that if you firewall it then the plane will decellerate until it stalls and crashes. Ideally, your aircraft would accellerate until it reached the airspeed that your prop pitch and rpm should produce. But it won't because drag conteracts thrust -...
  15. larr

    Q regarding air velocity immediately aft of prop disk

    Well, the acceleration of the local air when the aircraft is not moving is at its maximum that is not the whole story. Pretty much all fixed pitch props will be partially stalled at this state so the thrust generated is not the maximum possible. As the prop unstalls (as it accelerates) it will...
  16. larr

    Cracker Jack 2 LSA from Pete Plumb / Wood Wing Specialty

    I think the original Cracker Jack used a Dutch built DAF 2 cylinder engine converted for aircraft use. There were some problems with it and that may have led to the Pegasus project. As for CJ 2, does it have a monospar wing? I'd wonder about torsion issues.
  17. larr

    supercharging a two stroke

    There is a large after-market for small engine turbocharing, apparently anything over 125cc. So I guess the weed wacker and leaf blowing communities are being under served. Otherwise: Turbocharge anything! This is not any kind of endorsement - just using Google.
  18. larr

    Norms flying Boat

    Hi Norm! It probably will be easier to turn (spin) but harder to hold a particular course because of side slip. Additionally, a flat hull will tend to skip on even slight swells which will decelerate your craft.
  19. larr

    supercharging a two stroke

    okay, my $0.02 Billski has covered the issues but I want to expand a bit. In a crankcase pumped piston port design the exhaust port opens first and closes last. There is a small time portion where both ports are open, and the incoming charge helps to push out the exhaust. If you increase the...
  20. larr

    Norms flying Boat

    Hi Norm. It kind of looks like a Sea Flea hull. I'd guess minimal directional stability until you got going fast enough for the control surfaces to work. I think this one is still going to climb the bow wave leading to increased drag and less power as the thrust line goes more vertical.