There is a lot of discussion on the Yahoo GRT forum about the magnetometer placement so I am posting where I mounted mine on an RV-6A. More folks may see it here and I can ref this site to the Yahoo guys.
Mine, for a Dynon, does well there also. I used a bracket to get the angles in alignment but I think I used non-ferrous screws rather than zip-locks, for mounting but I did the plastic bag thing also....I packaged the magnetometer in a plastic bag prior to final mounting to prevent water from running down the vertical stab onto the mag. The mag is attached to my bracket with zip-lock ties.
The mag for my Dynon (and even earlier the mag for a BMA alpha test unit) has resided on that deck on my RV-6 for several years. There are no issues with ferrous interference. I suggest the mag be mounted on a bracket that will allow you to incline the device a few degrees to match the inclination of the EFIS for enhanced accuracy. I packaged the magnetometer in a plastic bag prior to final mounting to prevent water from running down the vertical stab onto the mag. The mag is attached to my bracket with zip-lock ties.
Would using nylon washers and screws work also for attaching and adjusting?
Ron Burnett
RV-6A finishing
The mag for my Dynon (and even earlier the mag for a BMA alpha test unit) has resided on that deck on my RV-6 for several years. There are no issues with ferrous interference. I suggest the mag be mounted on a bracket that will allow you to incline the device a few degrees to match the inclination of the EFIS for enhanced accuracy. I packaged the magnetometer in a plastic bag prior to final mounting to prevent water from running down the vertical stab onto the mag. The mag is attached to my bracket with zip-lock ties.
I have not ordered the magnometer yet, but am at the point of figuring out where to mount it before installing the top skin (on the back deck or btwn the 706 and 707 bulkheads . Do you have a picture of your mounting bracket for the back deck? Is it easy to access if ever needed back there?
Jim, maybe I wasn't clear enough with my description. The deck is the "shelf" under the leading edge of the vertical stab that is exposed when you remove the emp fairing. This makes the mag very assessable without having to crawl back into the tailcone. Also is convenient for locating the OAT probe under the horiz stab since the probe connects to the mag.
I don't have a photo, the bracket is just something I whipped up out of scrap stock in a few minutes using the TLAR school of engineering (That Looks About Right).
Obviously, from the other posts, the rear deck works, but in my case, this did not meet the conditions spelled out for my magnetometer or the ahrs. There are high-tension strobe lines running out to the rudder, and the rudder cables are also moving ferrous material. Both were to be avoided by more than 24".
Movement of the stainless rudder cables had absolutely no effect on the compass needle.
As a result of this test, I feel pretty confident that strobe cable EMI (electromagnetic interference) will not be a problem that will affect the magnetometer in my proposed location. Nor the rudder cables. Thus my magnetometer is going on the HS deck. No extra bracket to fab, and no extra weight
I decided to mount the magnometer for the AFS EFIS behind the baggage area on the vertical support about half way up. This put me over a foot from any metal cable or canopy rear bow. After spending a lot of time on a bracket, I got it mounted and checked it out. Unfortunately when I slide the canopy back I get about a 4-5 degree turn on the EFIS. It is very repeatable when going open or closed.
Why is this a problem....unless you fly with the canopy open?
Just make sure your canopy is closed when you run the calibration routine and you should be good to go.
You're correct, I won't be flying with the canopy open. Although normally I might adjust the DG on my old Cessna on the parallel taxiway so I don't have to do it while sitting on the runway or on the roll. If it's a hot day and the canopy is rolled back and then I close it just before takeoff I would now be out of calibration. It's a lot of key presses on the AFS to reset it so I'd prefer not dealing with that.
There was a topic on the AFS forum about the bolts connecting the horizontal stab causing issues when mounting on the back deck. So how do you test for that short of removing the bolts and putting them back in? I now understand why the instructions indicate 2 feet from anything metal. It's unfortunate that it's almost impossible to do.
... Unfortunately when I slide the canopy back I get about a 4-5 degree turn on the EFIS...
...normally I might adjust the DG on my old Cessna on the parallel taxiway so I don't have to do it while sitting on the runway or on the roll...
Why put a DG in? The Dynon is very reliable. If I did anything, I would put a whiskey compass in as a backup; simple, light, and I've known gravity not to work. Or in my case, my Garmin 496 is my backup since it can be run independent of all the aircraft systems.
BTW, I also mounted mine off the 707 bulkhead.
No, I'm not installing a DG in the RV. I currently have a vacuum DG in my Cessna (which the RV will replace some day soon) and my routine is to adjust it while on the parallel taxiway to the runway heading. So that routine won't work in the RV if the slider is open during taxi. So I'll just move the magnometer so the canopy frame doesn't affect it. Thanks for the input.
No, I'm not installing a DG in the RV. I currently have a vacuum DG in my Cessna (which the RV will replace some day soon) and my routine is to adjust it while on the parallel taxiway to the runway heading. So that routine won't work in the RV if the slider is open during taxi. So I'll just move the magnometer so the canopy frame doesn't affect it. Thanks for the input.