---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 05/22/06: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:45 AM - Aircraft performance (was Antennas) (Gilles Thesee) 2. 08:22 AM - Re: Aircraft performance (was Antennas) (Kevin Horton) 3. 12:19 PM - Matronics BBS Forums (Matt Dralle) 4. 12:50 PM - hidden attennae (Ernest Christley) 5. 04:29 PM - Re: Aircraft performance (was Antennas) (Gilles Thesee) 6. 07:25 PM - Alternator Field Breaker/Switch (Mark Chamberlain) 7. 08:25 PM - Re: Alternator Field Breaker/Switch (Dale Ensing) ________________________________ Message 1 _____________________________________ Time: 06:45:51 AM PST US From: Gilles Thesee Subject: AeroElectric-List: Aircraft performance (was Antennas) --> AeroElectric-List message posted by: Gilles Thesee Cher George Mc. Jetpilot, Thank you for replying. Hope the group won't mind this conversation. After all, the initial topic was about hiding or not hiding antennas. > In the US we have large expanse of land and REMOTE > radio outlets. To get ATC for radar, Flight Watch for > weather or Flight Service to open / close flight plans, > a clear powerful radio is so so important. Also we > have many class B and C air spaces that require a > good radio. > Would 100 NAUTICAL miles at 2000 ft AMSL, or 140 NM when above 5000 ft fill your requirements ? I'm quite satisfied with that performance. By the way, in the old continent, towers are more closely spaced than that, and we seldom have to contact anyone that far. Except for the fun of testing actual range. > > > This is what my hidden antenna friends heard all the time: > > AIRCRAFT CALLING WASHINGTON CENTER YOU ARE > WEAK AND SCRATCHY, > Hmm, maybe they would benefit from the Aeroelcectric List... By the way, my radio is loud and clear. > > .... >> industry doesn't believe in the existence of drag. Especially >> in the land of cheap gas and big engines. >> > What land and engineers are we talking about, monsieur. > American engineers? pardonnez-moi > Very few light aircraft engineers anywhere are concerned with cooling drag, internal flow mechanics or drag reduction. Those who really do their homework design faster airplanes. > > Land of cheap gas and big engines? America? > Ever bought gas in Europe ? Then you'll understand what I mean ;-) > > I would say a long EZ, even with 160HP is way more efficient > than a MCR 4S Two of our 5 hangar mates happen to fly Long EZ, and I'm not much impressed by their performance. And believe me, when taking off or landing on our less-than 2000 ft grass strip with no wind, they have their hands full. > ...I also say a RV-9A is more efficient than > your MCR 4S. Looking at the RV-9A with 115HP it has 10kt > faster speed (150kts). Hey, that's cheat ! You're confusing TOP speed (100% power) and CRUISE speed (75%). The RV-9A numbers on their website are phony. We all know that 75 % power speed is 91 % of top speed, that's elementary flight mechanics. So the RV-9A should either cruise at 136 kt, or peak at 159. As very few people will minimize their top speed, I'd say that the little bird tops at 150 kt, and their 75% power cruise is nearer to 90%... And our bird tops at 155 kt true on 100 hp only. Oh, and by the way, that's with four on board and 4 hr fuel... > Not sure what engine you have 80 or > 115 hp. > 115 hp takeoff, 100 hp top speed, 75 hp cruise at 140 kt true. 838 lbs empty, 1100-1200 ft/min @ gross weight. > Want to race my big engined > RV-7 with O360 190HP? > > Why not race with a two-seater ? The MCR 01 top speed is 168 kt on 80 hp. If you really want to cling behind at 80 hp, you better remove those antennas...;-) Regards, Gilles Grenoble, France http://contrails.free.fr ________________________________ Message 2 _____________________________________ Time: 08:22:38 AM PST US From: Kevin Horton Subject: Re: AeroElectric-List: Aircraft performance (was Antennas) --> AeroElectric-List message posted by: Kevin Horton On 22 May 2006, at 09:40, Gilles Thesee wrote: > --> AeroElectric-List message posted by: Gilles Thesee > > > Hey, that's cheat ! > You're confusing TOP speed (100% power) and CRUISE speed (75%). The > RV-9A numbers on their website are phony. We all know that 75 % power > speed is 91 % of top speed, that's elementary flight mechanics. > So the RV-9A should either cruise at 136 kt, or peak at 159. > As very few people will minimize their top speed, I'd say that the > little bird tops at 150 kt, and their 75% power cruise is nearer to > 90%... > Top speed (100% power) will be achieved at sea level, as the power will be lower at higher altitudes (assuming a normally aspirated engine). At sea level, the speed at 75% power should be about 91% of the speed at 100% power. As you said. But, at a given amount of power, the speed increases as the altitude increases. So, the best speed at 75% power will be at the highest altitude at which the engine will produce this amount of power. That is usually around 8,000 ft for normally aspirated engines, and the speed at that altitude should only be a few percent slower than the speed with max power at sea level. The CAFE Foundation tested Van's 160 hp RV-9A demo aircraft, and they found that the speed was higher than Van quotes on his web site (193 mph at 8,500 ft density altitude, vs 188 mph claimed by Van's). Van's claimed 75% cruise number for a 118 hp engine falls pretty much where you would expect given the difference in power, so I have no reason to believe that it is phony. I'd be interested in knowing what test data you have that contradicts the CAFE Foundation results. Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://www.kilohotel.com/rv8 ________________________________ Message 3 _____________________________________ Time: 12:19:05 PM PST US From: Matt Dralle Subject: AeroElectric-List: Matronics BBS Forums --> AeroElectric-List message posted by: Matt Dralle Hello Listers, I just wanted to send out a reminder to all of the Listers regarding the new-ish BBS (Bulletin Board System) Forums that are available at Matronics for the Email Lists. The BBS Forums give you Web-based access into the same email content that is generated by the Email Lists. When an email message is posted to any of the email lists, a copy of the message is also copied to the respective List forum section on in the BBS Forums. By the same token, when a message is posted within the BBS Forum interface context, it will also be posted to the respective email list. Basically, the BBS Forums give you yet another method of accessing the Matronics Email List content. Some people prefer email, some prefer web forums; now you can have it either way or both with the Matronics Lists! You'll have to register for a login/password on the BBS Forum to _post_ from the BBS, but you can view message content without registering for an account. To Register for an account, look for the link at the top of the main BBS Forum page entitled "Register". Click on it and follow the instructions. Site Administrator approval will be required (to keep spammers out), but I will try to get these approved in less than 24 hours. If you haven't yet taken a look at the Matronics Email List content over on the BBS Forum, surf on over and take a peek. Its pretty cool. The URL is: http://forums.matronics.com I want to stress that the BBS Forums are simply an adjunct to the existing Matronics Email Lists; another way of viewing and interacting with the Matronics List content. If you like Email, great. If you like Web Forums, great. If you like both, great. Its up to you how you view and create your content. You will also find a URL link at the bottom of this email called Matronics List Features Navigator. You can click on this link at any time to find URL links to all of the other great features available on the Matronics site like the Archive Search Engine, List Browse, List Download, FAQs, Wiki, and lots more. There is a specific Navigator for each Email List and the link for this specific List is shown below. Thanks for all the great list participation and support; it is greatly appreciated! Matt Dralle Matronics Email List Administrator ________________________________ Message 4 _____________________________________ Time: 12:50:28 PM PST US From: Ernest Christley Subject: AeroElectric-List: hidden attennae --> AeroElectric-List message posted by: Ernest Christley I'm building a tube and fabric and fiberglass plane, and I'm to the point of trying to decide where to put the antennae. Keeping drag down is of upmost importance to me, 'cause I feel that if I wish hard enough I could be a Reno contender some day 8*) Well, back to reality.... How about some comments on this person's work in combining the com antennae with the pitot tube. http://contrails.free.fr/instruments_ant_sonex.php -- ,|"|"|, Ernest Christley | ----===<{{(oQo)}}>===---- Dyke Delta Builder | o| d |o www.ernest.isa-geek.org | ________________________________ Message 5 _____________________________________ Time: 04:29:22 PM PST US From: Gilles Thesee Subject: Re: AeroElectric-List: Aircraft performance (was Antennas) --> AeroElectric-List message posted by: Gilles Thesee Kevin, > ... and the speed at that > altitude should only be a few percent slower than the speed with max > power at sea level. > You're right, we should take air density into account. But at lower altitudes, the angle of attack is less, and so is drag, so the effect you describe is somewhat compounded. I just phoned a buddy aircraft engineer on that matter. A 75% cruise at only 3 % below top speed still seems rather close, but who knows ? Please consider that we only talked about the RV-9A because George chose it for a comparison with our 4-seater. I was not criticizing any of the RV models. > The CAFE Foundation tested Van's 160 hp RV-9A demo aircraft, and they > found that the speed was higher than Van quotes on his web site (193 > mph at 8,500 ft density altitude, vs 188 mph claimed by Van's). How come ? 2 % more speed means 8 % more power. Please note I'm not questioning the CAFE ability to test an aircraft. > > Van's claimed 75% cruise number for a 118 hp engine falls pretty much > where you would expect given the difference in power, 118 hp to 160 hp yields a 10-11 % speed gain. And here we have 14 %... > so I have no > reason to believe that it is phony. Please pardon me for questioning those numbers, but at first sight, they seemed strange to me. I should have said that I always take published numbers with a grain of salt. And there is that tendancy for homebuilts to lose airspeed once they've crossed the Atlantic ...;-) > I'd be interested in knowing > what test data you have that contradicts the CAFE Foundation results. > Kevin, all I know is what you just told us, so why would I contradict ? Hope I didn't ruffle too many feathers. Best regards, Gilles Thesee Grenoble, France http://contrails.free.fr ________________________________ Message 6 _____________________________________ Time: 07:25:57 PM PST US From: "Mark Chamberlain" Subject: AeroElectric-List: Alternator Field Breaker/Switch --> AeroElectric-List message posted by: "Mark Chamberlain" Hi All, I'm just in the process of designing the electrical system for my RV-7 and I'm trying to figure out why we need a field switch and/or breaker for the alternator? I've searched and searched, I can find lot's of information on how to wire it, but as to the questions "why?", or what does the "field" wire do ; I can find nothing. I'm guessing it is a very simple answer and it is just my inexperience showing through. If someone could enlighten me it would be much appreciated. Thanks, Mark RV-7 - Panel DO NOT ARCHIVE ________________________________ Message 7 _____________________________________ Time: 08:25:30 PM PST US From: "Dale Ensing" Subject: Re: AeroElectric-List: Alternator Field Breaker/Switch --> AeroElectric-List message posted by: "Dale Ensing" I'm just in the process of designing the electrical system for my RV-7 and I'm trying to figure out why we need a field switch and/or breaker for the alternator? I've searched and searched, I can find lot's of information on how to wire it, but as to the questions "why?", or what does the "field" wire do ; I can find nothing. I'm guessing it is a very simple answer and it is just my inexperience showing In simple terms......... The field switch supplies current to the alternator field which is required for the alt. to produce electricity. The breaker the field switch draws current from is to protect the wiring in case of an excessive current such as a short. Dale Ensing