nlappos

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Everything posted by nlappos

  1. nlappos added a post in a topic What oil for rotary valve?   

    I should have added that Rick said to watch the oil level in the small reservoir. If it starts going down, that says you are burning the oil, so then switch to the 2-stroke oil (Amsoil) to prevent any dirty burning. I have about 10 hours so far, the oil level hasn't budged. My old 582 (using Lucas 2 stroke oil) never showed any level change in 160 hours.
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  2. nlappos added a post in a topic MK IV Aerobat speedwing spar gouge/repair   

    Yep, you're right Jeromef, my bad. This time I actually looked at the recommended splice and agree. A real repair splice should have an external sleeve the same thickness as the spar but with a larger diameter so it slips over the spar. It should run about 2.5 diameters long on both sides of the repair (5 diameters total length) and should be bonded to the spar with a structural adhesive (Scotchweld is good, I think). The deep scratch should be blended down to a smooth surface, and the splice fitted over it without scoring any of the material, bonded tightly with the adhesive squeezing out.
    This is probably overkill, because the area is before the strut, so the spar isn't in much positive bending, more likely it is in compression. I think the highest stress section of the spar is immediately outboard of the strut attachment.
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  3. nlappos added a post in a topic MK IV Aerobat speedwing spar gouge/repair   

    That splice will be stronger than the original spar. Go for it. In the future, transport the wings by suspending them lengthwise from the truck sidewall. I hung them at eye level, lengthwise along the sidewall of the truck, using nylon straps around the leading edges. They survived nicely.
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  4. nlappos added a post in a topic Avid B Sheriffs Auction on 10/2/18. 10:30am.   

    "Somewhere in between these two extremes lies your CG range" said Cloud Dancer. Right on. Range, not tolerance. So you do agree.
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  5. nlappos added a post in a topic What oil for rotary valve?   

    Rotax Rick ships with regular 30 w oil, since the rotary valve lube doesn't get burned. Says it is better lubrication, and not compromised by the need to burn clean.
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  6. nlappos added a post in a topic Avid B Sheriffs Auction on 10/2/18. 10:30am.   

    Cloud Dancer,
    The CG range is not really a tolerance band, like + .010" is a tolerance. The difference is that the airplane can operate across a wide band of speed, weight, altitude and CG, and none of them are tolerances, they are approved operating envelope areas, each with a horror story if exceeded.
    The forward CG limit is found by testing the aircraft at slower and slower speeds in landing condition, until the up elevator is no longer able to hold the nose up. This is because the up elevator is fighting the nose down tendency of that forward CG, and as speed reduces, the force the elevator can make to fight the nose down is reducing. Another possible way that forward CG can be limited is by crash loads, which stress the gear unevenly as the weight is shifted across the CG range, especially a nose wheel in a nose dragger.
    The aft CG limit is chosen almost the same way , but in that the elevator cannot stop the nose from popping up as the landing is made. If you fly an Avid at its aft limit, the nose in a landing flare tries to go to the sky, it is a spooky feeling. Some have said aft CG makes the airplane land slower, which is not correct, but aft CG does make the aft stick needed for high angle of attack (slow landing) much easier to get too. Another limit for aft CG is the ability to get out of a spin, because as CG gets further aft, the spin gets flatter, and the forward stick to recover gets less effective. Far enough aft CG and a stall can easily become a flat spin, where recovery is impossible. Test pilots put a spin chute in the tail and pop it out to make the spin stop if they go flat - a wild ride!
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  7. nlappos added a post in a topic W&b doneso   

    Terrific work, Matthew. I always wonder why people shy away from the rotax engines, they are great!
    What is your Max Gross Weight?
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  8. nlappos added a post in a topic Flaperon Control Break   

    I think the loss of one aileron would reduce the control power in half, and on short final, the change would catch many of us by surprise. This could very well lead to the case where the roll control was very sloppy, and ground contact becomes more likely.
    I think the evidence that the right flaperon control rod sheared, and the flaperon went neutral (right on flywise) would be fairly benign if it happened in cruise and you had some time to work it out.
    I doubt that the flaperon breaking at the control rod would make more drag on the broken side, but it would make an unbalanced drag, where the broken right flaperon would have low drag and the unbroken left one would have high drag, with the flap setting. You would think this could make the aircraft yaw left and roll left(strong dihedral effect), but the fact that the left had lots of flap setting would look like lots of right aileron, so the aircraft would roll right sharply. 
    It stands to reason that the rod would shear with large flap input, since the twisting of the rod is how we fight the normal flap force to streamline, so the torsion on that rod would be a maximum with high flap settings.
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  9. 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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  10. 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: http://avidflyer.wikia.com/wiki/Models
    Here is a list of the MK IV differences:  http://www.avidfoxflyers.com/index.php?/topic/540-how-to-tell-if-its-a-mkiv/&do=findComment&comment=3003
     
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  11. 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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  12. 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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  13. 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.
    https://en.wikipedia.org/wiki/Dihedral_(aeronautics)
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  14. 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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  15. 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:
     
    https://www.ebay.com/itm/2-50Ft-Exhaust-Manifold-Header-Black-Pipe-Heat-Wrap-Tape-10-Ties-Kit-HIGH-TEMP/263835573416?hash=item3d6dd35ca8:g:9lsAAOSwbehbxULN:rk:2:pf:0
    https://www.ebay.com/itm/DEI-2-inch-x-15-ft-Roll-Titanium-Header-Exhaust-Heat-Wrap-High-Temp-010129/273315522092?hash=item3fa2dfe62c:g:raAAAOSwZVlXt3z5:rk:4:pf:0
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  16. 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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  17. 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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  18. 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: http://www.aerofixaviation.co.uk/rotax-type-c-gearbox-service.shtml   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.
    Lesson learned - LOOK IN THE INSPECTION HOLES AT THE SIDES OF THE C BOX OFTEN, YOU CAN SEE THE ENTIRE DONUT. REPLACE THE DONUT EVERY 5 YEARS, PER MAINTENANCE MANUAL (PARAGRAPH 10.1)
    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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  19. 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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  20. 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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  21. 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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  22. nlappos added a post in a topic On 2-stroke oil...   

  23. 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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  24. nlappos added a post in a topic Belite Chipper Down   

     
    NTSB Prelim report:
    https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20180524X22838
    "According to the pilot, the accident flight was the first flight since maintenance was performed on the airplane's fuel system. The pilot stated that he departed Runway 32 and entered a right downwind to remain in the traffic pattern. While on final approach to Runway 32, he elected to execute a go-around. After opening the throttle, when about 150 ft above ground level (AGL), all engine power was lost. "
     
    Found this on a press release about Jim's latest sensor:
    "James Wiebe, president and CEO, was involved in an aircraft accident in Anchorage, Alaska, with the believed cause due to fuel starvation. As a result, Radiant Technology LLC, a Belite Enterprises company, is changing and improving its line of fuel management products. Our first announcement is our new Bingo 3 fluid detector.
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  25. nlappos added a post in a topic Rotax 583   

    My 670 from Rotax Rick has a recommended TBO of 450 hours only if you limit the cruise power (through monitoring fuel flow) to 4.0 GPH. If you average higher fuel flow, then he recommends 300 hours. My guess is that is just what Rotax would say if they pared it down that fine. I know folks have better lives than 300 hours, and I bet it is because they limit time at full throttle, and take good care otherwise.
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