A

apatti

Well Known Member
OK, I have spent hours researching this to no avail. Where are people mounting the magnetometer in 8(A)'s? The documentation on GRT's site says 12 inches from current carrying wires and 18 inches from ferrous metals. I assume other EFIS's have similar requirements. The only non-wing site I can ID in my 8A is up high in the back past the baggage compartment. That would be difficult to do once the back turtle deck is on and difficult to maintain.

Is it just larger masses of ferrous metals or does this include things like nutplates?

Thanks,
 
Where to put the magnemometer

Hi Tony

I have been scratching my head on that exact subject. Others have built a shelf and mounted in on one of the rear bulkheads. I mounted my strobe power supply just in back of the baggage compartment. GRT says 18 inches from there and as far as possible from ferrous stuff. I was thinking about a shelf just behind the F 809 bulkhead. I saw another picture of one mounted in from on the F 810 bulkhead. You are correct that it would be a PITA to get to later. Do you suppose they require much maintenence? The stobe wiring to the tail would then have to be routed as low as possible to keep it away.

GRT also talks about mounting it in a wing--as far out as possible. That would also be pretty difficult to get to. Hopefully, some of our collegues will have some actual experience.

Regards,

Michael Wynn
RV 8 Fuselage
San Ramon, CA
 
Tony,

I put mine way up high in the fuselage, one bay behind the aft baggage compartment. See photos here, here, and here. Mine is probably a bit of overkill -- if I had to do it again, I'd make a small shelf on the top of that bulkhead in the photos, like Paul Dye and others have done.

Everyone I've ever talked to said that the items to you must stay away from are things like strobe power packs, rudder cables, and the elevator bellcrank and pushrods -- the BIG steel stuff that moves or carries large currents. Nutplates, smalll wires, etc. will not affect it at all.

As far as difficulty of installation -- yeah, it's definitely easier to install it now with the skin off. (One of the unanticipated skills I learned while building an RV-8 QB fuselage is being able to turn off the slight bit of claustrophobia that might be hard-wired in to my brain. There's a lot of work to do back there in that tight little tube, and I'm not exactly a little guy...;))
 
apatti said:
OK, I have spent hours researching this to no avail. Where are people mounting the magnetometer in 8(A)'s? The documentation on GRT's site says 12 inches from current carrying wires and 18 inches from ferrous metals. I assume other EFIS's have similar requirements. The only non-wing site I can ID in my 8A is up high in the back past the baggage compartment. That would be difficult to do once the back turtle deck is on and difficult to maintain.

Is it just larger masses of ferrous metals or does this include things like nutplates?

Thanks,
Click to expand...

I just folded up a little shelf across the longerons in the aft fuse and it has worked well, although it is a PITA to get to. I've seen others do the same with good success.

For many of the EFIS panels, the magnetometer needs to be at the same angle as the AHRS, so design the shelf or bracket accordingly.

The wings are tough, because of the wiring going to the tips, and because of the water pipe/aileron balance weights.

Also make sure your canopy is closed when you calibrate it, because the steel canopy frame can cause a little wobble in the heading as the canopy closes.

A friend of mine folded up a small shelf, and then prosealed it to the upper longerons. This works well and was very easy in a finished QB fuse.

I also considered fastening a small bracket to the floor of the aft fuselage.
 
I mounted the magnetometer approx where Buck did in my RV6, fortunately the 6 has a stiffner running down the center to mount to (my shelf is very small, just the size of the magnetometer). Seemed like a good place, because my AHRS is mounted on a shelf just behind the bagage comp. Hope it all works out. I wonder if you could use a doubler on the skin at the top and make a small shelf to hang from that?
 
....GRT also talks about mounting it in a wing--as far out as possible. That would also be pretty difficult to get to.......
Click to expand...
Mike,

I'm building an -8 and consider wing mounting to be very acceptable location. I would think such access is far more convenient and serviceable than mounting the magnetometer behind the baggage compartment. Imagine having to remove the rear seat and with screwdriver in hand the contortions you will have to endure just to reach it. Apparently, many people are inclined to agree with Dynon's suggestion to the extent that SafeAir sells a special bracket for mounting the unit way out there on the wing. YMMV.

 
GRT recommended the wingtip in my 8

so that's where I put it. Works perfect. It's a maintenance free item once you set it up and lock it down.

I see you say you are spending hours figuring your AHRS stuff up generally.

Sounds like you aren't taking advantage of the GRT users group on Yahoo. I suggest you join if not a member. There's a ton of user photos and documents to leverage off of. Not to mention thousands of searchable emails just on GRT installation and operational matters.

Lucky
 
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If you put it one bay back of the baggage like I did, be sure to have the canopy closed when you swing it.

If I were to do it again, I would might choose the wing, but mine (dynon) seems to work fiine where it is.
 
I made a bracket for mine way back on the F-809 bulkhead.

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Guy
 
I just got done moving mine from the wing root to the wing tip

In my RV-10.

The wing root was absolutely the wrong place (according to GRT). In particular the comm transmit caused big swings in the magnetometer data.

The aileron mass balance on an RV-10 is non-ferrous (which may not be true for other models). I moved the strobe power supply as far forward as possible and put the magetometer as far aft as possible.

After connecting it all up, I checked the radios, the transponder, the nav lights, the landing lights, the taxi lights and the strobes and none caused any deflection in the magnetometer output stream.

As far as servicability, I can't imagine what you might need to do to the magnetometer. Having said that, on the RV-10 the wingtip is held on with about 30 screws -- I would hate to have to remove it on a regular basis.
 
in the back

aft of rear bag area- - small little bracket that attaches between the longerons. not the easiest place to access, but after levelling, there isn't much need to get to it.
 
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