Phil_P Posted December 31, 2008 Share Posted December 31, 2008 I know that we tend to fly at, or above top weight on our wings and that this will tend to give us a higher top speed. However, I am interested to hear other peoples thoughts on routes to obtaining a higher speed. Some wings, such as some of the Dudek range have some quite high accelerated speeds, but is it always the case that a higher speed is going to need a substantially greater amount of thrust, or are there wings that really do give you the best of both worlds, with both lift and speed? I'm aware that I could go faster than I do on my current wing (Swing Arcus) by adding ballast, but I'm already at the point that with full speed bar, and with trim fully out, which should in theory give me about 30mph, I require almost full throttle and hence my fuel consumption suffers. I'm also aware that in nil wind, a fast wing makes for higher speed landings, only yesterday I found myself still travelling quite fast even with trim right in and a big haul on the brakes. I'm not looking for black/white answers here, but welcome opinions and thoughts on your particular route and other options. Quote Link to comment Share on other sites More sharing options...
Guest Posted December 31, 2008 Share Posted December 31, 2008 My view, More of an extended trim range, is one way to go. The very latest reflex wing is both 'faster' and 'slower' then it's predecessors. If the development curve continues as it is, I think fast landings will be a thing of the past for all in a few years. SW Quote Link to comment Share on other sites More sharing options...
t_andrews Posted December 31, 2008 Share Posted December 31, 2008 Simon's right about speed range access to pilot. Used to be to slow down it was on the way to full flare... Wings have been a long way coming to this point to change (effective) wing loading in flight. I've seen photos of wings that shorten along their length in flight to achieve what the reflex profiles do today. From http://www.expandingknowledge.com/Jerome/PG/History/Strange/Album.htm That said, I think it will always be a challenge to maintain altitude when one increases sink rate / wing loading / speed regardless how they do it. Eventually we'll see something get published that is an effective "Thrust polar" so a pilot will be able to judge whether the motor or thrust they currently fly with will be enough under wing 'x'. Right now they are happily separated from any mention of motor. How many times have you heard someone upgraded once they got a faster wing? I'm not holding my breath for that, but it's a natural progression. Now, if that aixro xr50 http://www.woelfle-engineering.com/ (4stroke, clutched, and 48hp @ 33lbs) wasn't $5000 out of the box, and came with an in-flight adjustable this would all be moot... It is the future like reflex was to keep full trimmed pilots climbing. Quote Link to comment Share on other sites More sharing options...
Phil_P Posted December 31, 2008 Author Share Posted December 31, 2008 Now, if that aixro xr50 http://www.woelfle-engineering.com/ (4stroke, clutched, and 48hp @ 33lbs) wasn't $5000 out of the box, and came with an in-flight adjustable this would all be moot... It is the future like reflex was to keep full trimmed pilots climbing. I too rather like that Aixro, very nice looking bit of kit, and an impressive power to weight ratio. Wankels are a sort of two stroke/four stroke hybrid, and certainly do the biz for Mazda. As you say, £3000 or thereabouts for the power-plant isn't cheap, but if you were mating it to an existing chassis, not too far out of the bracket of a new motor complete. I'm already running a ground adjustable prop, so it would only be a case of sorting appropriate reduction gear and fuel supply system if running an underslung tank. Quote Link to comment Share on other sites More sharing options...
bathboy Posted December 31, 2008 Share Posted December 31, 2008 A few moons ago I chatted to MCJ about slow (take-off) v fast top wing speed. He told me that 'most' aircraft have a ratio of about 1:3 for takeoff and top speed. This can be improved for jets by swing wing and paragliders by reflex etc. but the basic ratio still exists. So the top speed of a foot launched paraglider is finite until we can run faster or grow wheels. Trim, loading etc can all help, but the faster the top speed of the wing the faster the take-off. Unless... From my experince, a Compact parajet with my 100kg on a smallish Action take-of speed equals my running speed! With reflex trims out and full speed bar it uses about 7 litre an hour. The same motor on a non-reflex large Nova Rotor was a lot slower to launch, 10-15 mph slower top speed and loads better on fuel, about 4 litre and hour. Air cooled Wankel aixro xr50 http://www.woelfle-engineering.com/ does look very interesting. I've seen water cooled Wankel and two stroke motors leak steam, so carrying super heated water is another complication I don't fancy. Cheers Paul Quote Link to comment Share on other sites More sharing options...
pete_b Posted December 31, 2008 Share Posted December 31, 2008 Also with wankels look in to the fuel economy as I don't think they are very good. Pete b Quote Link to comment Share on other sites More sharing options...
t_andrews Posted December 31, 2008 Share Posted December 31, 2008 first off, mods please redirect as needed - this little motor will be subject of a great deal of talk I imagine. Another thread on the go now? I asked wolfe about fuel consumption curve or anything they had to offer, but probably got dismissed as some internet kook or they simply didn't have the data. They did note that most of the use it's seen has been on/off throttle as one would expect from a kart engine. It is a water cooled engine, and I don't think the cooling system (rad/hoses) are included in weight as they usually are part of a kart. Water pump I think is external - manual suggests jack-shaft driven from wheels (section 5.1http://www.woelfle-engineering.com/GB/Produkte/Betriebsanleitung.pdf). I asked about thermostatic regulation and never got answered. Likely no friendly answer. I think it's a sweet engine, but it remains as a "cool to have" in my book until some plain questions get answered. 1) Fuel burn curve 2) total weight (cooling system, optional starter) 3) cooling system integrated or home grown? 4) insert things you'd like to know I can get a mini2 engine ready to bolt up for 3.2k CAD, and everything I read about the aixro xr50 suggests it starts @ 5k CAD with no redrive or cooling. This is no shock for a race specific engine, which is what it was developed for, but still keeps fiscal sepraration between proven engines and what may be next. Wolfe was working on a smaller displacement to possibly field the needs of 100ccish paramotor users today, but that's not what interested this more massive fellow. Imagine how smooth and *relatively* vibration free a rotary powered ppg would be. 4 stroke - even though it's a wankel it should sip fuel in comparison to a 2 stroke. With an inflight adjustable, you could dial it up for a blast into the air and tune it back for torque curve @ X cruise rpm. Looking forward to Gilo's offering as he's the first I've heard to be working on a paramotor implementation. Probably a spin-off from the everest expedition and the contacts/friends made through that effort. Exciting times. Giddyup 2009. Quote Link to comment Share on other sites More sharing options...
t_andrews Posted December 31, 2008 Share Posted December 31, 2008 From my experince, a Compact parajet with my 100kg on a smallish Action take-of speed equals my running speed! With reflex trims out and full speed bar it uses about 7 litre an hour. The same motor on a non-reflex large Nova Rotor was a lot slower to launch, 10-15 mph slower top speed and loads better on fuel, about 4 litre and hour. This comparison is missing range, or time to destination. Did you intend to imply these measurements for the same trip in similar conditions? It's a slippery slope consumption is when comparing different things with more than one variable. I'm not trying to question your measurements, rather to ask for qualification. One almost needs a flight commute at cruise to determine fuel burn comparison. That is, the small action covered a fair bit more ground burning 7lph all other things being equal (which they never are). Cruise flights for identical wing loadings averaged are probably the best way to get an efficiency reading and even then, they have to be the most boring flights ever to maintain steady cruise. Hit some throttle adjusting sink, meet a gust front or wind direction change and kablooey goes the data set unless it's averaged into larger pool. My gps (garmin 76cs) with the garmin mapsource data provides a flight graph showing alt and distance. If some repository online could consume these and categorize, we might eventually have some baseline for what to expect from any recorded wing, motor, or combination thereof. Even suggest a combination for upgrading pilots based on flight characteristics and weight... Like any database though - garbage in = garbage out Neat idea with a lifetime of work behind the pretty interface... Quote Link to comment Share on other sites More sharing options...
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