Recent content by DaveD

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  1. DaveD

    SpinLaunch kinetic throw to orbit

    Heatshield that can withstand piercing the vacuum containment membrane thing at 5000mph! The ground level sonic boom must be fun!
  2. DaveD

    Ion aircraft

    They haven't been used on a production vehicle since the Landrover Discovery stopped using them back in 2004. Great engine though. As someone who drives a 50 year old British car to work every day, I'm slightly hurt at you calling it junk :)
  3. DaveD

    Source for Carbon Rods?

    I agree on the bumpy ride... but making the wing "too stiff" doesn't risk the wing breaking, unless there is some concern around shock loading on the fittings? After all, if the increase in stiffness is achieved by adding material to the spar caps, there would be a corresponding increase in...
  4. DaveD

    Source for Carbon Rods?

    Jim's book says his preference is for "1/25th of the cantilevered semi-span" which he calculates at 8g loading. Personally I don't think the number is that critical, the concern is whether or not your controls will bind or foul some other part of the structure.
  5. DaveD

    EAA spreadsheet for landing gear design

    Designing laminated curved spring gear is a real challenge. The basic beam theory normally used for wing spars and the like is not valid for large deflections. The straightening action of the gear under load induces interlaminar shear and tension loads, hence the delamination failures discussed...
  6. DaveD

    Push-Pull control tube fabrication

    Did it say why? I can't think of a reason why length would have any relevance to the end type.
  7. DaveD

    Source for Carbon Rods?

    Depends on what category you're designing to 4.4g limit is typical for a utility category aircraft. Wiki - Load Factor
  8. DaveD

    Cowling fasteners

    My only concern with screws is, because I'm working on a pusher, if one did happen to vibrate out it would go through the prop. Other than that I agree, camlocs are rather expensive.
  9. DaveD

    Cowling fasteners

    I'm surprised this hasn't been discussed before, but maybe my search skills are failing me! There seems to be quite an array of options, so I'd like to know people's preferences. Dzus, camloc etc. Work well fo aluminium (I'm not a fan of the Dzus spring, so I prefer cam lock style) but what are...
  10. DaveD

    Polymer Bearings

    I'll second this. Delrin is a delight to machine although oil or molybdenum filled nylon may give smoother operation. I'm leaning this way for the rudder pedals and flap torque tube. I'm in two minds over elevator and aileron as any stick-slip behaviour here would be horrible for control feel.
  11. DaveD

    Source for Carbon Rods?

    I'm a bit late to this thread, but for those of you not in the US, DPP Pultrusions (in the Netherlands) will ship worldwide. I brought pre cut lengths to make some trial parts but they indicated they can supply long lengths on a spool on request. They weren't cheap though, and this was a few...
  12. DaveD

    Spring vs Aerodynamic Trim

    Even without all the maintenance headaches a jackscrew seems a bizarre solution for a light aircraft. It must weigh more than double the trim tab method and its not like Cessna take a fanatical approach to drag reduction... I wonder what their motivation was.
  13. DaveD

    Polymer Bearings

    Thanks guys, I might try a mock up with both ball bearings and oil impregnated nylon to see if I can feel the difference. I was a bit concerned with stick-slip behaviour, which is horrible in a control circuit.
  14. DaveD

    Spring vs Aerodynamic Trim

    Thanks, that was a good read.
  15. DaveD

    Polymer Bearings

    Given their light weight and suitability for high load & low speed applications it looks to me like oil filled nylon, delrin, or PTFE filled polymer Bearings would be a good fit for a variety of homebuilt applications, especially in the control and trim systems, but they don't seem to be in...
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