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Homebuilt Aircraft & Kit Plane Forum

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  1. M

    Slotted wing for propeller ?

    I saw a presentation once from a group of students who had built a model airplane with props in slots in the wings. After some careful performance measurements, they realized that the efficiency of the props (less thrust) there was much worse than in other locations (nose for example).
  2. M

    Flight testing...

    Any flight testing should only be done by a pilot who is proficient and current in the type or similar aircraft. Anything else is stupid and asking for trouble. If you don't meet that requirement, get someone else to fly it who does meet it. Get proficient in an airplane that is flown regularly...
  3. M

    Polymer Bearings

    Sealed ball bearings are best, but there is no reason why other materials including plastic cannot be used. It depends on the allowable bearing stress. This can be very low for plastic, so the bearing surface has to be very large. The bearing stress is the load divided by the bolt diameter...
  4. M

    Flight testing...

    It really depends on what kind of airplane it is and when it was last flown. First, it needs a very thorough inspection to determine that it is indeed airworthy. I would include a fuel flow test to ensure that the fuel gets to the engine in the proper amounts, hoses deteriorate... Then do a...
  5. M

    Experimental Soaring Association 40th Western Workshop

    I am planning to fly to the meeting in Caro 1, smoke permitting.
  6. M


    I still have a few pieces of RG-400 antenna cable for sale, 17 & 16 ft pieces no connector, and 1 x 17 ft with TNC connectors, $1.10 per ft & $8 for cable with connectors.
  7. M

    MOGAS/E85 etc.?

    I think this describes it best. Of course I drain the sumps before the flight and NO water is visible. The engine runs fine and produces full power with the dissolved water. My carburetor is on the cold side and from evaporating the fuel it just seems to get even colder at full throttle. The air...
  8. M

    MOGAS/E85 etc.?

    I have often been using mogas with ethanol in my VW engine and there is sooo much water in it (dissolved, not visible), that I get carburetor ice at any OAT, even now, in summer. I practically have to melt it off for a while with carb heat on after high power settings before I can retard the...
  9. M

    Engine running rough

    Check for obstructions anywhere in the induction system, such as a gasket that has shifted inside a duct and blocks some of the airflow.
  10. M

    Pusher cowling ideas

    When you buy a new, certified Rotax 912, it comes with a shroud / plenum on top of the cylinders for cooling air. It is hard to see in the pictures, but the duct where the air is supposed to go in (tractor installation) in on the engine right side next to the hub, pointed down. It is supposed to...
  11. M

    Pusher cowling ideas

    Pushers are more difficult to cool because you don't have the prop wash to help with getting the air through the cowling. This is particularly bad on the ground. So you need a pretty big opening in the back, preferably up high because hot air goes up on its own. All other considerations are...
  12. M

    First ideas for a mash-up homebuilt.

    The tail arm /volume is rather short and the main gear is too far forward (assuming the cg is at 25% wing chord), it will tip on its tail.
  13. M

    Increased Max Gross?

    Check out my video on "Loads"
  14. M

    Increased Max Gross?

    All good arguments, but you maybe forgetting something. The FAA is not going to check up on you if you fly an experimental over gross, but if you have an accident, you bet the insurance company will look at it, and has a good reason not to pay if you were outside of the envelope.
  15. M

    flaps & flutter?

    For certified airplanes this information may be in the type certificate data sheet (online at the FAA website) or in the flight or maintenance manual. A rule of thumb is that the freeplay at the trailing edge should be less than 2.5 % of the control surface chord aft of the hinge. If it is more...
  16. M

    AIRCAR 2 prototype details

    The pitch control inputs during takeoff are typical for an airplane with the horizontal tail mostly out of the prop wash and a main (rear) gear way aft of the cg. I would be concerned with slow flight/stall effects from a car body of the same width in front of the horizontal tail. That could...
  17. M

    Control surfaces actuators design/preferences

    When you say 6061 you also have to specify which temper condition. In condition -0 the material is too soft to use as control tubes, but can easily be bent for piping. -T6 is what you should get for structural applications.
  18. M

    Automotive V8, Fuel Filters, 100LL

    The Rotax fuel injected engine also requires a filter that easily clogs up. The system has a bypass that opens up to allows fuel to bypass the filter if its pressure drop exceeds a limit. This excludes catastrophic failures from engine stopping from no fuel flow and allows you to fly home and...
  19. M

    spar calculation

    Considering the weight of the wing for loads analysis is not conservative. During a positive load factor, the lift from the wing acts upwards, the weight of the wing acts downwards, reducing the bending moment. So neglecting the influence of the wing weight results in a higher bending moment...
  20. M

    Steps to scratch build a VW

    Pops, do you know a source for the wire style circlips (used for securing wrist pins in pistons)? I lost one. The new ones are different, I could not find the old style anymore other than with the complete set of cylinders and pistons.