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About nlappos

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  • Gender Male
  • Location Cedar City, UTAH
  • Interests flying, astronomy, reading, family

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nlappos's Activity

  1. nlappos added a post in a topic Mk iv or C?   

    Matthew, gross weight is by design, sort of, but also what the builder declared and then flew in Phase 1. The FAA paperwork is the final say, but then that means if the builder took a C that Dean Wilson meant to be a 1050 lb C and then flew it at 1200 lbs, a wise next owner should think hard about that. We could get into spar thickness and rib spacing and fuselage member thickness, but I don't know those details very well.
    I think the 1050 is the right design weight for a C, and that your paperwork agrees so that is a good number, and the right one, Matthew.
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  2. nlappos added a post in a topic Mk iv or C?   

    A very important attribute is the useful load, regardless of the model type. What is the empty weight and max gross weight? A good Mark IV is about 550 empty and 1150 max gross, for 600 lbs of useful load. Many C's have about the same empty but only  950 to 1050 MGW
    Here is a site that shows the major changes:
    Here is a list of the MK IV differences:
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  3. nlappos added a post in a topic Cabin Heat   

    It came with the kit, Matthew. Item F-78 on the parts list (I can't find the valve on the list)  I offer mine up for someone to make a splash from, it is fiberglas, about 1/16" thick, nothing fancy. I can also just photo and sketch it in detail, the only fancy interface is the rectangular flanged face that bolts to the radiator, and the circular tube for the orange tubing. More complex is the fancy spring loaded flapper valve that mounts on the firewall.
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  4. nlappos added a post in a topic Cabin Heat   

    The original heater seems to work well. I tried it yesterday and was surprised at its output. I also dammed the space between top of the firewall and the windshield bottom to stop the horrendous drafts, using cardboard and tape.
    I used a car choke cable to pull open the firewall valve, and located the inlet low on the firewall between my feet.

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  5. nlappos added a post in a topic Reduced Dihedral   

    Dihedral is an important contributer to flight stability, and should only be changedwith care and study. Basically, the uptilted wings make any yaw movement (sideslip) into a roll disturbance, so the aircraft stays reasonably straight in yaw, and the pilot sees the roll and corrects it. Dihedral makes the aircraft feel like the rudder and tail are even more effective. A flat zero dihedral would allow the aircraft to just slide sideward, perhaps with really bad results.
    Every time I fly my Avid I can see what a genius Dean Wilson is, and appreciate the way he balanced the design so well. I would not change a basic property without some serious knowledge and careful flight test.
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  6. nlappos added a post in a topic Would you use it ?   

    Only the manufacturer should buy off on those cracks or repairs of them. Those cracks are not primary airworthiness - strength issues, they are trailing edge splits where the drag forces on the blades at high pitch cause a buckling of that area as the blade is bent aftward, so they split open. It seems that few broken fibers are there. I bet a simple repair and rebalance is the fix, but the manufacturer must be the source of this info.
    Send those pics to them and ask.
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  7. nlappos added a post in a topic Cabin Heat   

    It seems that leaving it unattached and providing a gasket-like interface might be best. Welding would stick the two dissimilar materials together, different strengths and stiffnesses. That would mean that the cracks could be induced. Instead, how about a high-temp fabric wrap that fills the gap where the two materials would otherwise touch:

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  8. nlappos added a post in a topic Avid MK4 braking effect   

    Note the two photos, the old fat brake cylinder cannot fit close enough to the pivot point so it has about 1:1 mechanical advantage, and you get weak brakes. The new thin cylinder (with remote reservoir) fits much closer, and the new hole as compared to the old hole farther out on the tab shows the increase in mechanical advantage, about 2 1/2 times more powerful brakes. And it works.


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  9. nlappos added a post in a topic Avid MK4 braking effect   

    We have circled this drain at least 4 times in the last few months! Most Avid brake problems are due to crappy mechanical advantage at the pedal tops, where the brake has a 1:1 ratio to the brake cylinders. Here is one post:

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  10. nlappos added a topic in Rotax and other engines   

    Broken Rubber Donut on C Box
    Here is something we all should know. My rubber donut behind my C Box gave up the ghost 2 flight hours ago, it broke and separated in one place and cracked in another. No real vibrations, but a screetching noise was heard for a second or two, then everything was normal. I still had drive to the prop, and all seemed normal, but I made a landing to be sure.
    On post flight, I saw that the donut was cracked and broken. It was probably the original donut, perhaps hundreds of hours old, and is clearly dried out. On further inspection, I noted that the starter gear had separated so the starter would not spin the engine. The three bolts that hold the starter gear to the damper and the magneto flywheel in the back of the engine had sheared.
    Here's what I think happened: The donut was probably cracked and old, and I can't say that I inspected it. It finally cracked through in one place, and set up a torsional vibration. The back of the engine had the damper plate, it started vibrating and sheared the three bolts, almost immediately after the donut broke. This made the brief screeching noise, and also made the starter no longer spin the engine.
    I pulled apart the C box, (this web site was great:   and replaced the donut with a new one. I dropped the engine, and removed the back plate to expose the starter gear, extracted the sheared bolt ends (left hand drill and an extractor) and then replaced the bolts with new ones. Put it all together, mounted the negine, and have now flown about 2 hours with everything copacetic.
    For those wondering if the 670 caused the broken donut - I doubt it. At 6000 feet and higher where I am, I "only" develop 65 horsepower on the 670, so the donut sees what a 582 gives it at sea level. As proof, the max fuel flow I have ever seen up here is 7.4 gal per hour, the same as what I got on my 582 at full throttle.

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  11. nlappos added a post in a topic tank cap   

    Proof #2 that no welding is needed, this is mine, with Permatex Fuel Tank repair epoxy putty.

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  12. nlappos added a post in a topic On 2-stroke oil...   

    Strangely, I think the rotax folks know what we need, and tell us in their manuals. Radical? Nope.
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  13. nlappos added a post in a topic tank cap   

    The tube is punched right thru the cap, and it points into the wind so it pressurizes the tank at cruise speed a tiny bit, enough to keep the fuel pushing down the fuel feed lines. People who lost a cap in flight have reported a stoppage of fuel flow, so that slight pressure is a real help.

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  14. nlappos added a post in a topic On 2-stroke oil...   

  15. nlappos added a post in a topic R&D Tuned Pipe   

    Armilite, There are 7 columns and 5 headings, what's missing?

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