Magnetometers Rear Deck?

[Bayou Bert]

Thinking of mounting the two magnetometers on the rear deck
of my 9A in front of the HS/VS. Wiring for elevator trim, position lights
and strobe have to be at the bottom of fuselage. Cables for the rudder too.
Planning on mount the dual AHRS right of centerline just
behind baggage bulkhead. I already have the pitch servo and the power supply for the Whelen strobes there
on other side of center line.
Is this going to work?

[Sam Buchanan]

Originally Posted by Bayou Bert

Thinking of mounting the two magnetometers on the rear deck
of my 9A in front of the HS/VS. Wiring for elevator trim, position lights
and strobe have to be at the bottom of fuselage. Cables for the rudder too.
Planning on mount the dual AHRS right of centerline just
behind baggage bulkhead. I already have the pitch servo and the power supply for the Whelen strobes there
on other side of center line.
Is this going to work?

That magnetometer location has worked flawlessly in my RV-6 for 13 years, first as a beta tester for an unnamed EFIS manufacturer that is no longer with us, and since then for two Dynon mags.

However, having all the other stuff at that location may be a problem for you. Use a Boy Scout compass to see if there are magnetic fields being generated that will upset the mags. If you do end up using the deck, waterproof the mag, mine is wrapped in a plastic bag.

[Tony Rome]

Good morning,
There is also a free iphone app called magnetometer which will measure the
magnetic fields you are trying to avoid. I've found it is quite sensitive and works great.
Good luck on your project,
Tony

[pierre smith]

My buddy, an RV builder assist center, says that some magnetometers have to have a minimum distance from each other to avoid interfering with each other (AFS systems), so do some checking.

Best,

[RVbySDI]

Just to give another point of reference to consider, I fabricated two gussets for mounting my magnetometers on the upper longeron (sp) behind the second bulkhead back from the baggage bulkhead. One on either side. It works great in that location. I used Velcro and brass screws to secure the magnetometers to the gusset. If I can find a photo I will try to post it here.

Know that if you have a slider, that second bulkhead is as far forward as you should mount the magnetometers. If you mount further forward than that when the slider is open the steel frame of the canopy will cause disturbance in the magnetic field.

Update:
I found some pics of my magnetometer mounts that I took during construction. This pic shows the location of the two magnetometers with the gussets riveted to the current bulkhead location.


This pic is a good shot of how I mounted the gussets. However, you might notice it shows the gussets mounted to the baggage bulkhead instead of the second bulkhead back. This position had interference from the steel canopy frame so I had to move it back to the second bulkhead where it currently sits and does great.


P.S. These are GRT magnetometers. You did not state which manufacturer you are dealing with. The magnetometers may be of different design than mine so your setup might require a different mount than mine. At any rate, I wanted to give you a different perspective to consider.

[Dbro172]

Here:

http://www.mykitlog.com/users/displa...g=180922&row=8

[jsharkey]

I have the magnetometer for a Dynon D100 on the rear deck of my RV-6 with the thermometer mounted in the underside of the starboard HS tip fairing. It's a convenient installation.

However exercising the elevator through its full range swings the heading reading on the D100 by a couple of degrees, presumably due to the steel elevator horns moving near the magnetometer. In practice it isn't a problem since elevator movement when you are trying to hold heading is usually small and nowhere near full deflection in either direction.

Jim Sharkey

[Bayou Bert]

Steve that looks like a great idea. The cables for the harness don't
mess with them? I have GRT dual AHRS/magnetometers.
Where did you mount the AHRS?

[RVbySDI]

Originally Posted by Bayou Bert

Steve that looks like a great idea. The cables for the harness don't mess with them?

If you are referring to the seat belt cables, the answer is no. The seat belt cables go forward up high. The wiring for the magnetometers goes down to the floor and forward to the center tunnel. I will see if I have any pics of the harness location. I know that there is no interference with any wiring. I worked hard to make the routing work.

Originally Posted by Bayou Bert

Where did you mount the AHRS?

I fabricated a shelf that I mounted to the bottom of the sub panel and then forward to the firewall. This created a level and plumb surface to mount the AHRS.


As you can see in this pic, I have access panels in front of the windshield so that I have easy access to the area behind the sub panel. (both pics here were taken today as I was working on hard wiring a GDL39 into the airplane.)

[rzbill]

My GRT magnetometer is on the rear deck. Works fine.
One consideration though: The D-Sub mounting screws are a pain because they are up against the HS spar. You have to use a small stubby screwdriver (like a power screwdriver bit) which gets dropped into the fuselage....

If the HS spar would go ahead and crack and fall off, the D-Sub would be easier to install.

Magnetometer pic