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  1. Himat

    Just for discussion, Mechanical fuel injection?

    Once there was another «simple» fuel injection system. Used at least on the BMW 2002tii I think. It did have an inline high pressure fuel pump like and contemporary diesel engine. Fuel was set by a three dimensional “cam” Throttle position moved the cam in one direction, rpm in the other.
  2. Himat

    Pictures of a recent military exercise show the Russians are flying one of our designs

    Supercam S450 UAV, of the smaller UAV’s with 4,5m wing span and a system weight around 20kg. I’ll guess that STEALTH is not that a big priority. A link to civil usage: Gas Leak Detectors | Natural Gas Leak Detection in Main Pipelines
  3. Himat

    Very low aspect ratio planes?

    If the rudder is close to the centre of gravity the airplane does have a short tail arm. I do read that you by a low aspect ratio airplane imply a tail less airplane or a flying wing. If so, the reason for the short rudder lever arm is not that the plane has a low aspect ratio, but that it is a...
  4. Himat

    Very low aspect ratio planes?

    Yes, but Cl = M * g/(0.5*Rho*V^2*S) Decrease S, wing area and necessary Cl rises linear with reduced area. Cdi on the other hand then increase with Cl^2. That Cl squared term show that decreasing Cl reduce Cdi more than increasing AR. Same for the V, speed term that is squared. Fly faster and...
  5. Himat

    Very low aspect ratio planes?

    Well, if we go back to: Cdi = Cl^2/(pi*aspect ratio* efficiency factor) Evaluated at constant span and equal speed the formula for induced drag can be rearranged to: Cdi = k*Cl^2*AR The induced drag is proportional to the lift coefficient squared. Then for a given span, lift and speed the...
  6. Himat

    Very low aspect ratio planes?

    Wing area do not not quite, but pretty close set the stall speed. How much flap lift that is available depend pretty much on how complex the design is. There are differences in how much flap lift that is possible with different plan forms, but again complexity and weight set the limit. There is...
  7. Himat

    Still breathing!

    All well here. Me, wife and daughter did shift to work from home as Norway pretty much locked down. I Work rom home every other week all the time so no big change, wife find it different to be home all the time. My daughter finds the schools remote education ok. Then, last week I got...
  8. Himat

    Very low aspect ratio planes?

    Is really HAR more efficient? When people say a high aspect ratio wing is more efficient, they usually or often fall back and cite the classic induced drag coefficient: Cdi = Cl^2/(pi*aspect ratio* efficiency factor) And skip two underlying assumptions: Constant wing area. Evaluated at the...
  9. Himat

    Basic Torque Question

    First, the key is probably just for location at assembly. The taper and friction should be what opposes the torque. As that is general machine parts, how to calculate what torque the coupling can withstand should be in textbooks. Next, start up moment of different types of electric motors are...
  10. Himat

    "Thrust"

    A prop absorbing 100hp at 2700rpm will make the same trust whatever engine that turn it at 2700rpm. An engine with a PSRU must produce a little more hp than the direct drive to compensate for loss in the transmission. The PSRU loss may be a few %, that is the engine may have to be 103hp if...
  11. Himat

    Making an "obsolete" fighter into an unlimited racer !

    Only targets. Anti aircraft artillerist.o_O
  12. Himat

    Simple pusher pseudo-jet

    Well, if sort of scale I would rather emulate the de Haviland Sea Vixen than the Vampire. Ok, with the canopy on the centreline and no man down in the hole over there.
  13. Himat

    Usable single-seater on 24 hp?

    The Micro-IMP did fly on 25hp.;) What astonish me is that you are talking about designing for 100 to 150kg pilots! Ok, I have grown heavier by the years, but I am still less than 90kg. Not tall, but at 180cm not short either.
  14. Himat

    Pegasus flying car/helicopter at CES 2020

    To the USA DOT four wheels may make it a car, elsewhere maybe not. Norwegian regulations that usually follow EU regulations allow a four-wheel motorcycle. Four-wheel ATV’s are often registered in this group. If they get below the max weight limit. If light enough and have less than a 50ccm...
  15. Himat

    Boeing - Design Issues...

    https://www.homebuiltairplanes.com/forums/threads/broad-new-uas-rules-proposed-today.32815/ Maybe there is hope for less stringent UAS regulations?
  16. Himat

    Boeing - Design Issues...

    And with just a little bad luck, the subcontractors are all gone when they are to reopen the assembly line. To get the production going again will then take time, time for Boing’s customers to buy planes elsewhere. If they need them then. The current corona “flu” may decrease air transport...
  17. Himat

    Experimental sea plane please follow along

    First a reference Snorri Gudmundsson have written the textbook “General Aviation Aircraft Design, Applied Methods and Procedures”. “APPENDIX C3 – DESIGN OF SEAPLANES 1” was released as a PDF on internet after the book was out. This is one of the few recent texts on seaplane design and of the...
  18. Himat

    4500rpm propeller to negate the PSRU

    Some thoughts about designing an airplane for a «high» rpm engine with «small» propeller. First, I would search for and select the engine with the power at the lowest rotational speed. An engine spinning 4500 sound excessive, there must be auto engines that have decent power below 4000rpm...
  19. Himat

    4500rpm propeller to negate the PSRU

    The McDonell XF-88B was fitted with an Allison XT38 in the nose. The XF-88 Voodoo design did not progress beyond prototype stage. Later the name Voodoo was used on the F-101. The XF-84H Thunderscreech and XF-88B Voodoo was similar attempts to combine turbojet and turboprop in one fighter plane.
  20. Himat

    Why so expensive??

    There is a question about what the materials cost and what the kit contains. A look at the few pictures at the manufacturers site, https://www.walstromaviation.com/aero-adventure-kits, it look like the parts are machined, packed and maybe labelled as is the hardware like fasteners, odds and...
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