One of the neat things about building an RV-3B is that you get to do a LOT of internal design from scratch. Another is the fact that the airframe was originally designed with a fuselage tank ahead of the instrument panel, and since the -3B has wing tanks, all of that volume is now nothing but empty space! Combine these two neat things, and you have a chance to build in some fascinating places to mount such things as avionics and their related sensors.
Taking yet another page from Randy Lervold’s playbook, I had long ago decided to add a “shelf” of sorts extending from the firewall back to the instrument panel. This shelf would be a convenient place to mount remote avionics, relays, and other electronic and electrical components. In addition to this shelf, we are also building a center avionics stack, and I figured that the two items could work together structurally to make a very light “space frame” of mutual support. In fact, I began building the avionics rack without a firm plan for how it would be anchored at the top (the bottom is picking up existing nutplates on the F-303), figuring that the answer would eventually become obvious.
Well, it all worked out. What I did was to use a piece of 1” angle laid across the longerons to support the top of the avionics stack, and also serve as the aft end of the AHRS/electronics shelf. The shelf itself is simply two pieces of ¾” angle that rest on (and are bolted to) the top cross-frame of the firewall, and the aforementioned 1” angle. The angle is bolted to the longerons. Since the avionics stack vertical angles aren’t actually vertical, but lean forward, they don’t contact the face of the 1” angle, making anchoring them to this cross-piece problematic. But once I laid out the shelf design, I had my answer – I simply extended the side “rails” of the shelf beyond the cross-piece, forming two “ears” to which I could bolt the stack. Voila! Instant framework!
The Avionics Stack and Shelf are a common structure:
The shelf “ears” support the top of the avionics stack:
The bottom of the AHRS shelf is a piece of 0.040 I had in the shop, with two ¾” angles riveted on the bottom to make it nice and stiff. This will serve as a stable platform for the AHRS. The rest of the shelf will provide a very handy place to mount relays, wiring junction, MAP sensors, etc. It should make for a tidy wiring bay when it is all done. I haven’t decided exactly where the AHRS is going to go yet – forward or aft on the shelf – but as I gather more components and start building harnesses, it should find it’s natural spot.
I recently saw pictures of a gorgeous RV-3B that used this space as a forward baggage compartment ala’ the RV-8. I thought about how neat this would be, but then I thought about custom-building a door for it (with no prefab parts at all), and decided I’d just put the luggage in back. Maybe we’ll do the forward baggage on our next one….
Paul
Taking yet another page from Randy Lervold’s playbook, I had long ago decided to add a “shelf” of sorts extending from the firewall back to the instrument panel. This shelf would be a convenient place to mount remote avionics, relays, and other electronic and electrical components. In addition to this shelf, we are also building a center avionics stack, and I figured that the two items could work together structurally to make a very light “space frame” of mutual support. In fact, I began building the avionics rack without a firm plan for how it would be anchored at the top (the bottom is picking up existing nutplates on the F-303), figuring that the answer would eventually become obvious.
Well, it all worked out. What I did was to use a piece of 1” angle laid across the longerons to support the top of the avionics stack, and also serve as the aft end of the AHRS/electronics shelf. The shelf itself is simply two pieces of ¾” angle that rest on (and are bolted to) the top cross-frame of the firewall, and the aforementioned 1” angle. The angle is bolted to the longerons. Since the avionics stack vertical angles aren’t actually vertical, but lean forward, they don’t contact the face of the 1” angle, making anchoring them to this cross-piece problematic. But once I laid out the shelf design, I had my answer – I simply extended the side “rails” of the shelf beyond the cross-piece, forming two “ears” to which I could bolt the stack. Voila! Instant framework!
The Avionics Stack and Shelf are a common structure:
The shelf “ears” support the top of the avionics stack:
The bottom of the AHRS shelf is a piece of 0.040 I had in the shop, with two ¾” angles riveted on the bottom to make it nice and stiff. This will serve as a stable platform for the AHRS. The rest of the shelf will provide a very handy place to mount relays, wiring junction, MAP sensors, etc. It should make for a tidy wiring bay when it is all done. I haven’t decided exactly where the AHRS is going to go yet – forward or aft on the shelf – but as I gather more components and start building harnesses, it should find it’s natural spot.
I recently saw pictures of a gorgeous RV-3B that used this space as a forward baggage compartment ala’ the RV-8. I thought about how neat this would be, but then I thought about custom-building a door for it (with no prefab parts at all), and decided I’d just put the luggage in back. Maybe we’ll do the forward baggage on our next one….
Paul
Last edited:
