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#11
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"G.R. Patterson III" wrote in message
... Stefan wrote: Effective mufflers already exist, three or four blade props already exist, and it make a huge difference without any negative side effect. They reduce power, add drag, weigh more, and are very expensive. I call those *big* negative side effects. http://www.newpiper.com/FlyerArticleMarch04.pdf Have a read of the section "Quieter Warrior". The "expensive" bit is right though! Paul |
#12
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"Peter Duniho" wrote in message
... Muffler-equipped airplanes are not uncommon in Europe. They don't even look all that aerodynamic...just a big extension to the exhaust, sticking out and along the side of the cowl. http://www.jodel.com/exhaust.htm Paul |
#13
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On Fri, 06 Aug 2004 16:38:31 +0200, Stefan
wrote: Rick Durden wrote: requirements such as slower turning, shorter props and more effective mufflers. It won't be fun. Why won't it be fun? What's the fun of making a lot of noise and embarrassing the neighbours? Effective mufflers already exist, three or four blade props already exist, and it make a huge difference without any negative side effect. Where have you been? There are several negatives. Speed and fuel consumption for a trip. Lower RPM means less HP. The idea is not to make noise, but to gain efficiency. The more blades you add to a prop the less efficient. You do gain climb, but you lose cruise and take more fuel. Going from a 2 to a three blade prop greatly quieted the Deb, but it lost about 4 knots top end. Normally you are talking more HP to swing more blades. Now, if you go to a monster airfoil like the 3-blade used on Rare Bear, it turns slower and makes less noise than the high RPM props at the races, but it is *huge*. BTW, the 3-blade prop on mine weighs 83#. It replaced a 57# 2-blade. It also cost $8800 exchange and that was nearly 10 years ago. The most efficient exhaust system is a tuned exhaust and they are not quite. One example is http://www.airliners.net/open.file/231156/M/ No, this is an example of a muffler on a light, slow, airplane, not something with speed. I travel 500 to 1200 miles. I don't want to do it at 120 MPH. OTOH I normally do it at 5,000 to 8000 feet although my last trip was over a month ago and most of it was at 2800 due to the ceilings and airspace. Just opening the cowl flaps costs me 20 to 30 knots. Imagine what something like that hanging out would do. Putting the gear down feels like some one put on the brakes and turned it into a very expensive Cherokee that burns a lot of gas. With the gear down top speed is less than the 140 MPH gear down speed. With the gear up and cowl flaps closed, cruise is a160 knots true at ~6,000 feet. Currently from Central Michigan I can normally beat the airlines to Denver or Central Florida as there are no direct flights from here. I may be slower than they are and I may have to stop once for a potty break and to top off the tanks, but I'm still usually an hour faster. That was before 9/11. Now I'm probably 2 hours faster but I've not had the chance to get to Denver in a couple of years.. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Stefan |
#14
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On Fri, 06 Aug 2004 17:30:54 +0200, Stefan
wrote: G.R. Patterson III wrote: They reduce power, add drag, weigh more Not really. Oh yes. As I mentioned in a previous post. I replaced a 2 blade hartzel on my Deb with a 3-blade hartzel. The 3-blade weighs 83# and the 2-blade was 57. Stuck that far out in front they certainly make a difference. It also cost me about 4 knots in cruise. and are very expensive. Replacing a perfectly good two blade prop is expensive, yes. But when the prop must be replaced anyway, or factory installing a four blade prop instead of a two blader doesn't cost that much more, if you relate If you don't call $8800 exchange expensive. Actually you can overhaul a 2 blade for about $5,000 so the 3-blade is about $3,000 more. Over the life of the prop at 4 knots, the difference is many thousands of miles. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com it to the total cost of an airplane. Stefan |
#15
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On Fri, 06 Aug 2004 16:29:52 GMT, "G.R. Patterson III"
wrote: Stefan wrote: But when the prop must be replaced anyway, or factory installing a four blade prop instead of a two blader doesn't cost that much more, if you relate it to the total cost of an airplane. That's true in many cases. At the rate things are going, I expect to need a new prop in about 30 years (if I don't get a prop strike before then). Then we also have to deal with certification issues. The manufacturer has only certified my aircraft for one prop. I suppose that STCs would be developed pretty rapidly if 3-blade props were mandated, of course. And if they were mandated they'd probably run between $1,000 and $2,000 each plus the cost of the prop and labor. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com George Patterson In Idaho, tossing a rattlesnake into a crowded room is felony assault. In Tennessee, it's evangelism. |
#16
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On Sat, 07 Aug 2004 06:19:25 GMT, "Earl Grieda"
wrote: "C J Campbell" wrote in message ... I do think that the demands of airport neighbors that airplanes make no noise whatsoever are unreasonable. I personally think that most complaints about noise are really just an excuse to make airplanes go away. Most people are basically superstitious morons who have irrational fears of anything that is even a little bit outside their experience. Making no noise is probably unreasonable. I suppose even a hot-air ballon makes some noise ascending. The airport/neighbor noise issue is difficult to resolve because "resonable/unreasonable" are to subective a term. Would a requirement that an aircraft on departure sound no louder at 500 feet than Here reasonable might take on a different meaning. We are located on the north side of the fair grounds where they hold motorcycle races, demolition derbies, and rock concerts. We had a Falcon 900 three engine jet do a max effort take off the other day. Even scorched all the grass between the end of 06 and the road. He wasn't nearly as loud as the rock concerts and he was gone in 30 seconds. There is also a 4 lane express way between the airport and expensive neighborhood to the south. They often complain about noise that turns out to be trucks on the express way. Some day some one isn't going to make it into the short runways and take out a couple rows of houses all because they wouldn't let the runways be lengthened. Yet we have 30 to 40,000# jet landing with just barely legal distance. We have 5 to 7 jets a week, but none nearly as large as the Falcon 900. Still, if one of those has a problem on a short runway? a 2005 factory Accord sound at full power accelerating from stop onto a freeway with 70 MPH traffic? Not for a new aircraft designed to that specification, but unreasonable for existing aircraft. But since it will take decades before existing aircraft disappear noise will be an issue over and over. Besides on the highway you have all that heavy traffic with big rigs and we can not locally regulate the traffic on the interstate. I doubt if "most complaints about noise" are about making aircraft go away. They probably are about making the noise go away. Wait awhile and I think you will see many just want GA to go away. They don't even want to hear one going over 5,000 feet up. With our short runway (18/36) lining up with a subdivision off each end I only use it when I have to, but when I have to I end up only a few hundred feet high when I go out over the subdivision. I can count the boards in the picnic tables. Had they not fought the runway extension I'd be at pattern altitude. Tremendous difference in noise. They should be happy I spent the $8800 for the 3-blade prop. With the 2-blade the tips were still supersonic when I went out through there. They tell me the dishes would dance in the cupboards. We still get a lot of transient aircraft in with big 2-blade props. The only sympathy I have for the complainers is altruistic. I care not for them, but I do care how the noise bothering them will affect my ability to safely fly. Although I'd not care for the noise myself, were it not for the negative impact on the airport I'd like to see about 20 AT-6s flying 8 hours a day out of there on the short runway. Not that I'm vindictive. I try to be a good neighbor, but I still like the thought of the 20 AT-6s. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Earl G |
#17
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Roger Halstead wrote:
Then we also have to deal with certification issues. The manufacturer has only certified my aircraft for one prop. I suppose that STCs would be developed pretty rapidly if 3-blade props were mandated, of course. And if they were mandated they'd probably run between $1,000 and $2,000 each plus the cost of the prop and labor. Usually it's the prop manufactoter who lets his props be certified for a type of plane, because it's him who wants to sell the prop. So you can buy a fully certified prop. That's how it works in Europe, and how it would in the US, too, I suppose. Stefan |
#18
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Roger Halstead wrote:
Where have you been? There are several negatives. Speed and fuel consumption for a trip. Lower RPM means less HP. Why less RPM? Speed maybe, but why more fuel consumtion? The idea is not to make noise, but to gain efficiency. Noise is wasted energy. So theoretically, a system with less noise is more efficient. Practically, there's nothing less efficient than supersonic props. Mufflers, if well engineered, don't put back pressure to the engine. The exhaust system is a comlex dynamic oscillation system, and well tuned mufflers can even enhance the power of an engine. Rip off the exhaust system from a modern car. You'll be surprised how much power you loose! (Don't ask me why I know.) Going from a 2 to a three blade prop greatly quieted the Deb, but it lost about 4 knots top end. Agreed, this is a trade off. But, frankly, I think a quiet airplane is worth 4 knots. I travel 500 to 1200 miles ... cruise is a160 knots true Let's see. 1000 nm @ 160 kn gives 6 h 15 min 1000 nm @ 156 kn gives 6 h 24 min So with the quiet prop, you loose 9 minutes on that 6 hrs trip. The most efficient exhaust system is a tuned exhaust and they are not quite. They can be quite quiet. No, this is an example of a muffler on a light, slow, airplane, not something with speed. Just opening the cowl flaps costs me 20 to 30 knots. Imagine what something like that hanging out would do. Agreed. But there are also exhaust systems that fit into a cowling. I don't have a picture, though. Stefan |
#19
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"Roger Halstead" wrote in message
... On Mon, 9 Aug 2004 15:35:03 +0100, "Paul Sengupta" http://www.flyflightstar.com/pages/ctphoto.htm Why the javascript? My firewall takes one look and won't let me go there. Um, I don't know. Was just trying to find a photograph. Takes ages to load on my dial-up connection too... Do a search for Flight Designs CT and see what you can find. It's not really a substitute plane for a Deb or Bo though... Paul |
#20
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"Roger Halstead" wrote in message
... Mufflers can not be very effective on big engines without causing back pressure and a reduction in power. What you see in Europe is gained more by the reduction in RPM than the muffler. Lower RPM, less output gasses means the engine is quieter and it is easier to muffle. It is also developing less HP and in my opinion creates a safety concern. Not necessarily. The mufflers/silencers don't. Or don't have to. And the quietest engines are the Rotax 912s which run at over 5000 rpm. Of course they don't produce 260hp! http://www.hliese.de/International/international.html They do one for the Bo. They claim no performance degredation and a weight of 2lbs. "Beech-33, -35 und -36 ( all Versions with Conti. IO-520 )" Paul |
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