AeroElectric-List Digest Archive

Sat 12/23/06


Total Messages Posted: 11



Today's Message Index:
----------------------
 
     1. 07:54 AM - Re: Some experiments fail (Ernest Christley)
     2. 07:59 AM - Some experiments fail (Fergus Kyle)
     3. 08:31 AM - Re: Re: Fuse Link At Battery (Robert L. Nuckolls, III)
     4. 08:45 AM - Re: Voltage Across Open Batt Contactor (Bob McCallum)
     5. 10:23 AM - Re: Some experiments fail (Ernest Christley)
     6. 02:05 PM - Re: Some experiments fail (Kevin Horton)
     7. 04:50 PM -  Some experiments fail (Harold Kovac)
     8. 05:08 PM - Re: Some experiments fail (Ernest Christley)
     9. 05:10 PM - Re: Some experiments fail (Ernest Christley)
    10. 05:24 PM - Re: Some experiments fail (Harold Kovac)
    11. 05:33 PM - Re: Some experiments fail (Kevin Horton)
 
 
 


Message 1


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    Time: 07:54:22 AM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    Subject: Re: Some experiments fail
    Gilles Thesee wrote: > <Gilles.Thesee@ac-grenoble.fr> > > >> >> Maybe a better approach would be to engineer a suitable antenna, then >> hollow it out to act as a pitot, > Hi all, > > In my buddy's article at > http://contrails.free.fr/instruments_ant_sonex.php, he says he > designed the antenna out of an aluminum tube, and matched it to the > particular form of the vertical fin, acting as a ground plane. > He as not flown yet, and advises to wait for real world tests. > That would be the intelligent way to do it, but like Bob has said several times, the normal procedure is for structural guys to have their say, then the aerodynamics guys, yada, yada, yada, and somewhere down the list the antennae guys get to say something. In my case, I'm using Dynon's AOA indicator. It doesn't include a static port (which you think it would for $200US), and there isn't a nice place for one on the sides of a Delta, so I had to engineer one in. The antennae experiment proceeded from that point. I tried adding some coils of 22AWG. Wrapped around a drill bit, and held with tape, I put them in series with the element. It made things so much worse that I didn't even bother recording numbers. I've got some ferrite beads, but don't know if it's worth disassembling the coax connector to install them. I guess it couldn't hurt at this point. The ground is basically the entire welded tube airframe. The black wire coming from the coax connetor is grounded next to the antennae's base. The connector is also mounted on a strip of stainless that is riveted to another piece of stainless that is in turn welded to the airframe. Is it possible that some combination of fiddling can bring the SWR down from the astronomical 8.6 to something below a 3? I think something below 3 would be marginal but acceptable. I think.


    Message 2


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    Time: 07:59:49 AM PST US
    From: "Fergus Kyle" <VE3LVO@rac.ca>
    Subject: Some experiments fail
    Ernest, Tying a VHF antenna to a pitot design is very ingenious..... and deserves some serious thought! Kudos to you for the idea. What needs doing is to revise the length of the pitot to match the needs of a 1/4wave monopole OR devising matching circuit to adjust the pitot to 50 ohms impedance at 127 Megs. I don't think devising apitot system from an antenna is the way to go. I am hesitant to believe the matching scheme shown would measure the true impedance/results, but can't offer any advice in that area. The latter would be the easiest if not the best (one always seems to prefer a natural resonance) but it cries out for a suggestion......... It strikes me that the vertical length might be the problem since the greater depth would reduce losses due to some horizontal content - the pitot need. Is this a metal skin or fibreglass? Good luck! Ferg Kyle Europa A064 914 Classic


    Message 3


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    Time: 08:31:39 AM PST US
    From: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
    Subject: Re: Fuse Link At Battery
    At 08:42 PM 12/19/2006 -0500, you wrote: >Bob . . . >The authority rests with experiment. > --Lawrence M. Krauss > >Thanks for the follow up and feedback. The need to experiment at the wrong >time has been averted. > >I appreciate it. Happy holidays to you and yours. >Johnathan Thanks to yourself and others for the kind words. I'll endeavor to remain worthy of them. I've been off line for a few days. Seems the flu bug came to visit and I've been tethered to the commode on a very short leash for the first two days. Dr. Dee and I are going to go for a walk in the park this morning to try and stir up some muscles and circulatory systems that have been setting idle too long! Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > ---------------------------------------------------------


    Message 4


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    Time: 08:45:50 AM PST US
    From: "Bob McCallum" <robert.mccallum2@sympatico.ca>
    Subject: Re: Voltage Across Open Batt Contactor
    Jim; If the contactor is open and there are any loads connected on the downstream side then you would expect to see approximately battery voltage across it, just like any other open switch with a load attached. However if there are absolutely no loads at all attached then you would see no voltage across it as there would be no return path for the electricity to complete your meter circuit and it would read zero. The reading you are getting is so close to zero that you should conclude that you have essentially no loads connected downstream of the contactor, but there is a tiny leakage sufficient to provide a return path and indicate on your meter. Depending on your meter, this resistance would be in the millions of ohms indicating, perhaps, simply the insulation resistance to ground of some component or other. (quite normal) If you turn on anything downstream then you will get a reading of battery voltage if all is well. Bob McC ----- Original Message ----- From: PIAVIS To: aeroelectric-list@matronics.com Sent: Saturday, December 23, 2006 1:30 AM Subject: AeroElectric-List: Voltage Across Open Batt Contactor After connecting the battery contactor per Z-13, is it common to have about .04 V across the contactor when open? I'm sure I'll have plenty of basic Electrical 101 questions as this is sure my weak area on this RV so far. But I'm learning! Jim -7 Redmond, WA


    Message 5


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    Time: 10:23:32 AM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    Subject: Re: Some experiments fail
    Fergus Kyle wrote: > > Ernest, > Tying a VHF antenna to a pitot design is very ingenious..... and deserves > some serious thought! Kudos to you for the idea. > What needs doing is to revise the length of the pitot to match the needs of > a 1/4wave monopole OR devising matching circuit to adjust the pitot to 50 > ohms impedance at 127 Megs. I don't think devising apitot system from an > antenna is the way to go. > I am hesitant to believe the matching scheme shown would measure the > true impedance/results, but can't offer any advice in that area. > The latter would be the easiest if not the best (one always seems to > prefer a natural resonance) but it cries out for a suggestion......... It > strikes me that the vertical length might be the problem since the greater > depth would reduce losses due to some horizontal content - the pitot need. > Is this a metal skin or fibreglass? > Good luck! > > Fiberglass and fabric skins over a 4130 frame with stainless steel rib structure. I've been playing with the position of the jumper from the pitot to connector, and the best I've been able to come up with is a low SWR of 6.5 or so.


    Message 6


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    Time: 02:05:16 PM PST US
    From: Kevin Horton <khorton01@rogers.com>
    Subject: Re: Some experiments fail
    On 23-Dec-06, at 11:52 AM, Ernest Christley wrote: > I'm using Dynon's AOA indicator. It doesn't include a static port > (which you think it would for $200US), and there isn't a nice place > for one on the sides of a Delta, so I had to engineer one in. The > antennae experiment proceeded from that point. > Static ports need to be in a location where the pressure is very, very close to the ambient pressure if they are to provide an accurate static source. Pitot tubes in single-engine aircraft are almost always mounted below the wing. The pressure below the wing is higher than the ambient pressure - otherwise no lift would be generated. This makes a pitot tube a very poor place to locate a static source, unless you are prepared to test a large number of different locations, with several test flights at each location. I've watched one small aircraft manufacturer do this exercise with a Piper pitot tube. They invested many hours of flight testing on several different configurations before finding a location that worked acceptably well with a custom angle on the bottom of a Piper pitot tube - the angle changes the pressure sensed at the static source. Kevin Horton RV-8 (Finishing Kit) Ottawa, Canada http://www.kilohotel.com/rv8


    Message 7


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    Time: 04:50:41 PM PST US
    From: "Harold Kovac" <kayce33@earthlink.net>
    Subject: Some experiments fail
    Hi Kevin, I'm building an RV9A and have installed the Dynon pitot. Besides the ram air,there's a small hole on the bottom for static air, that way I suspect the engineering's already been done. Food for thought at any rate. Harold ----- Original Message ----- From: "Kevin Horton" <khorton01@rogers.com> Sent: Saturday, December 23, 2006 5:02 PM Subject: Re: AeroElectric-List: Some experiments fail > <khorton01@rogers.com> > > On 23-Dec-06, at 11:52 AM, Ernest Christley wrote: > >> I'm using Dynon's AOA indicator. It doesn't include a static port >> (which you think it would for $200US), and there isn't a nice place for >> one on the sides of a Delta, so I had to engineer one in. The antennae >> experiment proceeded from that point. >> > > Static ports need to be in a location where the pressure is very, very > close to the ambient pressure if they are to provide an accurate static > source. Pitot tubes in single-engine aircraft are almost always mounted > below the wing. The pressure below the wing is higher than the ambient > pressure - otherwise no lift would be generated. This makes a pitot tube > a very poor place to locate a static source, unless you are prepared to > test a large number of different locations, with several test flights at > each location. > > I've watched one small aircraft manufacturer do this exercise with a > Piper pitot tube. They invested many hours of flight testing on several > different configurations before finding a location that worked acceptably > well with a custom angle on the bottom of a Piper pitot tube - the angle > changes the pressure sensed at the static source. > > Kevin Horton > RV-8 (Finishing Kit) > Ottawa, Canada > http://www.kilohotel.com/rv8 > > >


    Message 8


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    Time: 05:08:34 PM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    Subject: Re: Some experiments fail
    Kevin Horton wrote: > <khorton01@rogers.com> > > On 23-Dec-06, at 11:52 AM, Ernest Christley wrote: > >> I'm using Dynon's AOA indicator. It doesn't include a static port >> (which you think it would for $200US), and there isn't a nice place >> for one on the sides of a Delta, so I had to engineer one in. The >> antennae experiment proceeded from that point. >> > > Static ports need to be in a location where the pressure is very, very > close to the ambient pressure if they are to provide an accurate > static source. Pitot tubes in single-engine aircraft are almost > always mounted below the wing. The pressure below the wing is higher > than the ambient pressure - otherwise no lift would be generated. > This makes a pitot tube a very poor place to locate a static source, > unless you are prepared to test a large number of different locations, > with several test flights at each location. That's why I copped out and just used the location the plans called for. Heh, I can't run but so many experiments at once!! 8*) After 4 hours of fiddling, I was able to drop the SWR to 7.3 by moving the point where it attaches to the tube. I actually was able to get it to drop to 1 at one point. I installed a T connector...the antennae on the leg, the line coming off one side of the top and a 50 ohm termination on the other side. I don't think that counts though.


    Message 9


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    Time: 05:10:07 PM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    Subject: Re: Some experiments fail
    Harold Kovac wrote: > <kayce33@earthlink.net> > > Hi Kevin, > I'm building an RV9A and have installed the Dynon pitot. > Besides the ram air,there's a small hole on the bottom for static air, > that way I suspect the engineering's already been done. > Food for thought at any rate. > Harold The hole in the bottom rear is a drain hole. The hole at the front on the slant is for the AoA indicator. There's no static.


    Message 10


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    Time: 05:24:49 PM PST US
    From: "Harold Kovac" <kayce33@earthlink.net>
    Subject: Re: Some experiments fail
    Thanks, I don't have the instrument yet, and assumed....it's plumbed to the wing root...probably another year to get a look at the real thing. Harold ----- Original Message ----- From: "Ernest Christley" <echristley@nc.rr.com> Sent: Saturday, December 23, 2006 8:09 PM Subject: Re: AeroElectric-List: Some experiments fail > <echristley@nc.rr.com> > > Harold Kovac wrote: >> <kayce33@earthlink.net> >> >> Hi Kevin, >> I'm building an RV9A and have installed the Dynon pitot. >> Besides the ram air,there's a small hole on the bottom for static air, >> that way I suspect the engineering's already been done. >> Food for thought at any rate. >> Harold > > The hole in the bottom rear is a drain hole. The hole at the front on the > slant is for the AoA indicator. There's no static. > > >


    Message 11


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    Time: 05:33:15 PM PST US
    From: Kevin Horton <khorton01@rogers.com>
    Subject: Re: Some experiments fail
    Harold, 1. I think that is actually a water drain hole. 2. If someone did the engineering and flight testing required to use a static source on a pitot tube, it would be specific to one exact mounting location and mounting angle on only one type of aircraft. It wouldn't be practical for Dynon to do the flight testing required to define a mounting location for each type of aircraft that people would want to mount this pitot on. Each aircraft type would probably require at least a dozen hours of flight testing, with mod work required to move the pitot tube around every two or three flights. Huge job. Kevin On 23-Dec-06, at 8:48 PM, Harold Kovac wrote: > <kayce33@earthlink.net> > > Hi Kevin, > I'm building an RV9A and have installed the Dynon pitot. > Besides the ram air,there's a small hole on the bottom for static > air, that way I suspect the engineering's already been done. > Food for thought at any rate. > Harold > ----- Original Message ----- From: "Kevin Horton" > <khorton01@rogers.com> > To: <aeroelectric-list@matronics.com> > Sent: Saturday, December 23, 2006 5:02 PM > Subject: Re: AeroElectric-List: Some experiments fail > > >> <khorton01@rogers.com> >> >> On 23-Dec-06, at 11:52 AM, Ernest Christley wrote: >> >>> I'm using Dynon's AOA indicator. It doesn't include a static >>> port (which you think it would for $200US), and there isn't a >>> nice place for one on the sides of a Delta, so I had to engineer >>> one in. The antennae experiment proceeded from that point. >>> >> >> Static ports need to be in a location where the pressure is very, >> very close to the ambient pressure if they are to provide an >> accurate static source. Pitot tubes in single-engine aircraft >> are almost always mounted below the wing. The pressure below the >> wing is higher than the ambient pressure - otherwise no lift >> would be generated. This makes a pitot tube a very poor place to >> locate a static source, unless you are prepared to test a large >> number of different locations, with several test flights at each >> location. >> >> I've watched one small aircraft manufacturer do this exercise with >> a Piper pitot tube. They invested many hours of flight testing >> on several different configurations before finding a location >> that worked acceptably well with a custom angle on the bottom of >> a Piper pitot tube - the angle changes the pressure sensed at the >> static source. >> >> Kevin Horton >> RV-8 (Finishing Kit) >> Ottawa, Canada >> http://www.kilohotel.com/rv8 >> >> >> >>




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