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Your operating limitations cover this procedure. |
893 lb 9a
It is possible to build a 9a to meet the 900lb max empty weight. I built my 9a to meet the Recreation Aviation Australia spec's which has the same MTOW and Stall as LSA. The aircraft weighed in empty at 893lb with a 0-235 C2C Lycoming and Kato prop. the light weight gives the 9a a flapped stall of 35 kts and 38 kts clean. You would never lighten up an existing aircraft to get it down to anywhere near 900 lbs but if you keep focused on the goal of building one to meet that weight it is possible as long as you stay focused and don't even deviate for 1/2 a oz. Do your research well and stay focused. As an example there is 41 lb difference between the lightest 0-235 and the heaviest.
Be warned...… the lightest components are usually the most expensive!!!! The most important thing....STAY FOCUSED!!!!!...STAY FOCUSED!!!!!....STAY FOCUSED!!!!!!!!!!!!!! And you can do it. Did I mention STAY FOCUSED!!!!:eek: :D Bob |
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Barnacle Bob😘 |
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What did the O-235 C2C Lycoming weigh with engine mounts? What other key items did you use or skip altogether? No paint? Glass EFIS? No wheel pants or fueselage and pant fairings? Carbon fiber cowling? No interior? Fiberglass bucket seats with air cushions for seats and backs? I would think if one could afford it, using the Rotax 915IS, though expensive, would lose a LOT of weight, quickly, over a O-235? Or a Big Bore kit on a Rotax 912 ULS that bumps it to 120 HP, normally aspirated? The devil is in the details, maybe share some of the big hitter details for putting a RV-9A on a Weight Watchers diet. |
ultralight 9a
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The 0-235 C2C as received (used) weighed in at 245 lb and after re-build and fitment of all the lightest bolt on's weighed in at 217 lb but that was not with engine mounts. Most of the weight savings was in the interior and under the cowls so everything where possible in the aircraft was moved forward for COG. This was a quick build kit but nothing was modified on the supplied build. I studied the RV12 for ideas and cut 45% off the weight of the seats when I constructed them and fitted a D180 EFIS as part of that study. Moved the battery mount over in line with the starter motor, this meant about 50% less cable was required and this as well as the low compression engine meant a smaller cable as well as a smaller battery could be used. The cowls are standard fiberglass. light paint was applied to 25% of the aircraft. first up there was no wheel pants or intersection fairings fitted to the mains but with some further weight savings else where in the aircraft I was able to fit pants and fairings to the mains and still keep the weight under 900 lbs. To give you all details of the weight saving build I would need to write a book. But basically never fit anything to the aircraft without studying it first, looking at the job it has to do and trim off all ballast on that piece before fitting even if you think it is not worth the micro weight saving!! Always, SAFETY MUST COME FIRST!!! The most important things.... Dedication and stay focused on the end product. Back when I first posted first flight with the weight of the aircraft ( April 2011) I had builders from all over the world wanting advise and guidance to build light but most had lost the plot before they were even half way through their build. this is why I keep saying STAY FOCUSED!! I'm not too sure how you would go with COG with a Rotax….. may be longer engine mount and this would mean longer cowls etc and that means adding more weight to save weight. From memory the Lycoming 0-233 LSA engine which wasn't released when I built mine is about 5 lb lighter than my 0-235 C2C. Bob |
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Most RV-12's go 775 # with paint. A really skinny one with no paint and no interior might go 750#, and they start with a 95 HP Rotax 912 ULS motor, only 95 HP due to dual air filters instead of a single air filter. So I don't see under 900 # with 115 HP being much better or worse. It might be a 140 to 145 MPH bird. Of course, if built with a 115 HP 914 Turbo, the 9-A will do much better at elevation, where it shines. The RV-9 will, of course, have more drag than the RV-12, longer wings, and the CG is further aft. In a RV-12, you sit FORWARD of the wing Spars, your butt sits maybe 4 to 5" in front of the leading edge of the wing spars, due to the lightness of the engine. Myself, I would love to see a RV9 built around a Rotax, 915IS Turbocharged motor making 141 HP. But as you said, the plane would need some sort of redesign, or maybe a RV-15 model or RV-16 model, to make it possible. I think that if it was the first turbocharged powerplant available from Van's, and capable of something a bit above utilitarian G load rating wise, so you don't exceed the "envelope" at 15k, it might fill a nice niche. But don't quote me on it, Van's knows more than anyone else, what sells and what it's customers want. I am new to the game, and I'm not impressed with a motor that eats a quart of oil every 6 to 10 hour. A Rotax rarely does that, if at all, if run on Mogas and Full Synthetic motor oil. Or at least mine doesn't. |
No matter what engine you use different people have different opinions of engines. I've flown a lot of hours behind Rotax's and they are a great little engine but I have also flown behind Lycomings and they are my old favourite.
The Rotax is a performance engine that produces more horsepower pr cube than the Lycosauris and it also has the gearbox to help get more torque to the prop. the Lycoming was designed back in the 1940's (from memory mine is a 1956) and their idea back then to get more power was to bolt on a supercharger and increase the cubes. So what you do is up the performance of the Lycoming. I stayed with the low comp pistons but I fitted P Mags (electronic ignition gives a better spark and timing= more power), Fitted a Rotec TBI (that gives better atomisation of fuel-air mixture= more power) 1 1/2" crossover performance exhaust system(=more power). While the "more power" may not add up to much it does improve the 0-235's performance. I have 2 Cato props for the 9a, A climb prop and a cruise prop (it takes me about 15-20 minutes to change a prop). The climb prop with 2 up and fuelled to keep it under 1320 lb MTOW it will climb out at 1000' a minute and cruise at 120 kts IAS @ 2450 RPM sipping 3.7 GPH of Mogas or avgas. The cruise prop with the same load climbs out at 800' FPM cruises at 130 kts @2450 RPM sipping 3.8 GPH. Because oil is cheap compared to engines I change the engine oil and filter every 25 hours. the engine now has just on 600 hrs on it but I never have to add oil between oil changes. Bob |
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