rotax618
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Everything posted by rotax618
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If you want to have any endurance using current battery technology I suggest that you aim for the highest aspect ratio that you can build within structural/weight restraints, you really need a L/D of >18. There is a place for very low aspect ratio aircraft, they can be built lighter, more compact, stall free, stol performance BUT you will not get sailplane performance.
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To see the sketch can be viewed by clicking the thumbnail on my previous post. I would need to build and fly more larger scale models of the concept, alas I am limited by my health these days.
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The attached is a sketch of a possible low aspect simple aircraft. I placed the pilot below the wing to address the access, visibility and undercarriage length problems associated with this planform. I admit that it would be better looking and more efficient to sit in the wing, with transparent floor and retract U/C.
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I have found using models that an inverse zimmerman planform has a better L/D than a circle.
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The UC has to be long because the wing does not stall at the 12deg that a conventional rectangular planform does, these low aspect ratio circular (curved) planforms can maintain boundary attachment at angles of attack at 23deg AOA so they dont stall, they just attain a high drag controlled sink. The fin and rudder is not blanketed by the wing, at high AOA large vortices form on the top surface of the wing and maintain airflow over the rudder. As you can see from the video the aircraft has exceptional performance considering the modest 503 power, is stable and controllable. I would say that if developed this type would make an ideal sports aircraft.
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If you look at the RCgroups forum they have quite a bit on circular wings, experiments have shown that circular planforms are inherently stable at all angles of attack, can maintain upper surface attachment at high angles of attack irrespective of the airfoil used, but work best with a sharp leading edge which seems to create a vortex. There are several successful examples of circular wings. The aircraft industry has pretty much ignored these low aspect planforms because they look weird. Google "inverse zimmerman", "Arup aircraft" (semi circular) , "TWIT" (the wing is the thing)
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Most Sav ASIs read incorrectly as most don't have a working static and unless you have a rear door catch the doors get sucked slightly open at the rear which generates quit a vacuum inside the cockpit, raising both the altitude and airspeed. I have yet to see a static which works 100%, If you find how and where to put a static vent that works -please let us know. I could not get a static to work any better than an open vent behind the instrument panel, my ASI seems to be relatively accurate but I have 3 point door catches.
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G'day, this is my pitot setup, I changed the original setup after nearly poking my eye out and after reading an article by Bill Whitney concerning the positioning of the pitot relative to the leading edge, Roger Weston showed me the article. The new setup is a bit "agricultural" but is much more accurate at all angles of attack and makes it impossible for the pitot to cause eye injury - I used two of the screws holding the inspection cover to attach the bracket.
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Give him a ring, I can send mine if you have no joy. You need to get some 1.6mm x 1/2inch stainless steel strips guillotined. They twist so you have to straighten them. The jig consists of 2 parts, the first is a drilling jig and the second is a forming jig. They are self explanatory once you see them. If I was at the Hangar I could send you a photo.
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Jimbo, the Boorabee ailerons are superior and easier to build than Drifter ones. I have dies and jigs to make the drifter type hinges, I think Danny made a die set. If you need them let me know.
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G'day Jimbo, the trim motor has been working for me for around 9years on the Savannah with no probs. I built my trim position indicator from a Dick Smith led level meter funway kit years ago, Dick Smith alas doesn't have that kind of thing anymore.
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Yep its me.
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G'day Mark, I believe Roger Weston has pulled a module to pieces and has a circuit, Ask Danny Leach. Cheers
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Note: the throttle linkage above won't work with the VG bed mount, it is too flexible, may be able to get it to work with more slack in the outer cable. They sure make carbs sync easier and stay in tune longer.
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A photo of my modified throttles
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G'day, I have been enthusiastically following your progress and wish you success, we certainly need an engine like yours. The only concern I have is the gear ratio, 2:1, if I read correctly. All PSRUs that have an even reduction ratio have failed (Honda CAM 100 being one example) as the same gear teeth are subjected to the maximum torque continuously. It does not change your design to change the crankshaft coupling reduction ratio to an uneven ratio so the max torque is applied to all of the gear teeth. If I have not correctly understood your design please ignore this post. Cheers
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The firewall on all of the Savannah models ( VG, XL & S) are the same size as is the bulkhead behind the seat. The difference is that the firewall has about 6deg more rake on the VG. ICP decreased the angle, it may explain why XLs are having more nose wheel problems because they have much less camber i.e. the nose wheel is more upright and is subject to greater loads when steering at speed. I used an XL engine frame, with spacers to make up for the greater rake, and ring mount but I will be building a new engine frame. The cowl needs a little bit added to make up for the increased angle. Cheers
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Great photos thanks. Anyone pick the model of the Savannah, its a VG with an XL front. Cheers
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G'day, the Savannah was mine, flew down on Friday before the action. I'm not offended. Cheers
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G'day, there is a good explaination of 2 stroke failure here two strokes from my experience this article is spot-on Cheers Tom C
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G'day, I fly out of Evans Head NSW, and am a member of the Casino Aero Club. I built and am currently flying an ICP Savannah Bingo. I have built a number of aircraft over the past 40 odd years - a primary glider, a couple of Gyros, a Volksplane, a flying flea, a couple of Drifters, I designed and built a few Boorabees, and an ICP Savannah. I still have a couple of aircraft designs I wish to try. Cheers Tom C
