# Intrument Panel Thickness in Aluminum, Glass, and Carbon

Discussion in 'Instruments / Avionics / Electrical System' started by wsimpso1, Jan 2, 2019.

1. Jan 2, 2019

### wsimpso1

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I looked and could find very little on this topic. One thread said sailplanes are using 5-6 plies of 200 g/m^2 (6 oz/yd) glass cloth, while Jarno indicated less in graphite. But these are smaller panels.

I know, I am a composites analysis guru, why do I not just figure it out? Truth be told, if a convention already exists, I like to go there instead... Besides, it mostly comes down to having enough stiffness, and for this, I am betting that empirical processes mean more than my use of SolidWorks...

So, my panel is 46" wide, will have a couple 10" Dynon displays, an IFR GPS/NAV/COM, a backup EFIS, and some smaller stuff. What thickness is being used for this sort of thing in aluminum, glass composite, and graphite composite?

Billski

2. Jan 2, 2019

### Toobuilder

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A typical monolithic aluminum panel is .050 min, .063 very common. If you add a nice return flange on the bottom and the top is secured well to the boot cowl/glareshield it's not going anywhere.

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3. Jan 2, 2019

### Marc Zeitlin

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So the Long-EZ/COZY/ Etc. uses a 3-core-3 layup of 2 plies of 7725 glass at 45 degrees with 1 ply of 7715 glass transversely, with the core being 6 lb last-a-foam. The COZY also has a 1" wide foam/glass stiffener just above the legholes (doubles as a wiring trough) and another about an inch down from the top. VERY stiff and strong.

Now, for the instrument panels that I retrofit into canards, I use 3 mm AL, cut out the existing panel except for the perimeter and the stiffeners, and screw the 3mm AL to the perimeter. Even 3mm AL is just WAY too wiggly, unless you use multiple support brackets for it along the width. On an RV-7 replacement panel, I again used 3mm AL, screwed to the skeleton of the original panel (thinner, but with the original stiffeners top and bottom still extant). I found this to be a bit wiggly, and added a few angle bracket stiffeners to the bulkhead forward of the IP.

Your IP can never be too stiff - the last thing I like to see is the IP move when I twiddle a knob or poke a touch screen.

I'm in the process of planning my COZY MKIV IP replacement (since apparently, I have $40K burning a hole in my bank account) and will have something VERY similar to what you're describing. Here's the current plan: This will be based on the Aeroelectric Connection Z-14 drawing, with dual alternators, dual batteries, and a cross-feed. Each side of the panel will be supported by a separate bus. The panel was designed in Front Panel Express: http://www.frontpanelexpress.com/front_panel_designer/the_idea/ which can import a DXF of the external shape and then add all features, including anodizing, engraving, printing, graphics, etc. and it gives you a running total of the cost. My panel above will be about$625 - a drop in the bucket given the total panel cost.

In any case, given the huge holes that get cut in the panel, weight is not impacted much by going thicker. Since you're building a composite plane, you can build a VERY stiff sandwich framework, attach a 3mm AL panel, and have it look GREAT.

I will be attaching the AL panel to the existing composite panel with nutplates, and ALL the instruments to the AL panel with nutplates. The goal is to NEVER have to use two hands to remove anything from the panel, and never to need two hand access to the back. The panel is drilled/c'sunk for all nutplates and rivets, as it comes from FPE.

Way more info then you asked for, but maybe it's useful.

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4. Jan 2, 2019

### Jerry Lytle

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Nice to have someone refer to it as an INSTRUMENT PANEL! From recent postings I thought all were installing dash panels from left over Chevies.

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5. Jan 2, 2019

### pictsidhe

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I've been looking into building some of my own instruments, using Chevy instrument stepper motors...

It's more fun down and much cheaper here in the Goodwill section of the site

6. Jan 2, 2019

### wsimpso1

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Two philosophies in less than an hour! I appreciate the comments.

TooBuilder, how close do you space the connections along the edges to make an 0.060" panel feel adequately substantial?

Marc, Very helpful. Since you put the photo on, I have to get us talking about panel choices. First some simple questions:

That the standard Rutan layup is used and is stout is heartening. That it also makes a great foundation for 3mm panel is also good news. How close do you space edge connectors?

The standard Long EZ panel - I am guessing 1/4 Divinycel for the core, correct?

Your top center panel appears to have starter switch, masters/alt field switches for left and right buses, and the outermost two are illegible - what are they?

Below that main switch set is a Cockpit set. I am assuming status lights for the canopy and interior lighting control, right? If not what are they?

Left side appears to be Ignition and EFI switches, right side is external lights, correct? Outside of those is pitot heat and the autopilot. Yes?

The rest (except Parking Brake) are illegible, but a couple appear to be landing gear switches and manual control. The panels to extreme right and left are a mystery to me. Please help;

I am looking for fuel pump switches/status and alternator status/breakers (from Z-14). Maybe they are there, but I could not read them.

Now comes philosophy:

I see that you went for the Dynon compact autopilot panel and knob controls for bugs, etc, and the Avidyne Navigator, but you went for a conventional NAV radio and the Avidyne audio panel instead of a low footprint Dynon NAV and the Dynon internal audio panel functions - Why that choice? My suspicion is you already have the NAV radio and audio panel. If not, please elaborate on the choices there.

I am assuming you have throttle quadrant on the console, so other controls only go so far down the center. I like the switches on top of the MFD's and GPS/NAV/COM, but the stuff outboard by your knees, well, I do not get it yet. Perhaps you could tell us the story behind that too.

Mine is more embryonic than yours, which has given me a bunch of thought starters.

Billski

7. Jan 2, 2019

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Last instrument panel I did was 0.080 2024-T3 Clad with a .5" fold at the bottom. However that was full of steam gauges, and wasn't every practical due to the weight with a full avionics fit out and the fact that it still flexed due to the size of the radio stack cutouts.

If I had to do it again with the modern lighter weight, shallow depth electronics I would be looking closely at a two piece honeycomb panel.

Edit: panel thickness was 0.080" not 0.125 as originally posted

Last edited: Jan 3, 2019
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8. Jan 2, 2019

### Mark Z

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I used .063.

9. Jan 2, 2019

### Toobuilder

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I grabbed most of this text from my project page... It will save me some typing:

...Debated simply modifying the existing instrument panel one more time to allow the addition of the SDS programmer, but in the end I decided that it would be almost as easy to build new. The new panel's lower edge is raised about an inch and a half to give me more knee room, so that will be welcome. The large piece of empty real estate on the left side will be occupied by my Ipad mini, which gets it off the floor or side pocket.

The rework of this panel represents lessons learned from hours and hours of cross country time. Its tough to tell exactly how you are going to use an airplane until you've covered a few miles in it.

This shot shows the ragged pie cuts and horrible riveting in the original top brow of the panel, compared to my new version, which employed my recently aquired metal shrinker/stretcher. Im far from an artisan with metal and this airplane is not winning a gold Lindy at Osh, but its a bunch better than before...

So to answer your question about fastener spacing, keep in mind that I've attached a steel brow instead of the aluminum mess so that I could push the edge distance and reduce thickness to save some room. The rivets are #40's on 1 inch centers and the screws that hold the boot cowl lid and instrument panel together are #8's on 1.5 inch centers.

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10. Jan 2, 2019

### wsimpso1

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Funny thing about that. When I met the woman who is now my wife, she was doing product engineering on auto interiors for Ford and talked about the IP. The bosses of the folks who work on dashboards call it an Instrument Panel. Talk about delusions of grandeur ... The instruments take up about the same area as each of the music, the heat/AC, the glove box, and the passenger side airbag, while knee bolsters and other crash surfaces take up even more. Instrument panel! Harrumph. It would more accurately be called Collision Injury Reduction System.

It happens in other businesses too. At Remington Arms, what everyone I know called the trigger group was called the Fire Control Module. Never mind that fire control usually involves estimating range, wind, movement of target and weapon platform, aiming with corrections and then tripping the trigger. I commented during my job interview that I thought the fire control on a sporting firearm was the nut behind the buttplate. Got laughs all the way around, got the job anyway...

Yep Instrument Panels!

Billski

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11. Jan 2, 2019

### pictsidhe

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I will be making my IP from coroplast. Thickness will depend on instrument weight. Possibly reinforced with pultruded carbon rods or tubes. I somehow doubt that $40k of instruments would be found dead in a coro panel... 12. Jan 3, 2019 ### Marc Zeitlin ### Marc Zeitlin #### Well-Known Member Joined: Dec 11, 2015 Messages: 402 Likes Received: 529 Location: Tehachapi, CA By "edge connectors", I assume you mean the screws that attach the new AL panel to the fiberglass sandwich substrate, or the glass flanges along the fuselage sides? If so, then you can see the attachment screw holes around the perimeter - any hole that's about 1/2" from the edge will be a mounting screw, so they're spaced anywhere from 3" to 6 - 7" apart. There will be a few holes in the center as well - I'm piggybacking the angle brackets that will hold the center radio stack as support for the panel to the sandwich as well. these are doubling as a couple of the Dynon screen and controller box screws. I was mistaken above - what's actually used is 18 lb/ft^3 Last-a-foam, not 6 lb/ft^3, and it's 0.2" thick, not 0.25". So the center box has EI 1, Bat/Alt 1, Start/Crossfeed, Bat/Alt 2, and EI 2. The left box is the "ECU 1/2" toggle switch, oriented horizontally and the Fuel Pump 1 and 2 switch. The rightmost box is NAV, Strobe and LL/Taxi lights. The two switches below and to the left/right of the center are A/P servo power on the left, and Pitot heat on the right. The smaller center box is cockpit dimmer and screen dimmer knobs. No "status" lights - all warnings will be discretes into the EFIS's. Yes. So in the center, just to the right of the G5, is the Landing Brake switch. I also have a latching relay system that raises the LB if I go to more than 80% throttle - with the LB blocking the NACA scoop into the engine, you can melt a cylinder fast with it down on a go-around. Below the G5 is the manual landing gear extend shaft, with a switch to turn off the back EMF connection so that IF you have to manually extend the gear, at least you're not working against the back EMF of the motor. Below that is the landing gear switch and a couple of LED's for down / in transit. I also have a circuit that will automatically extend the gear if the following four conditions are met - above 40 KIAS, below 90 KIAS, throttle below 10%, and below 400 ft. AGL. Under the left air vent is the parking brake cable and the retractable step cable. Under the right air vent is a ground power test button and switch for the Nuckolls plans ground power socket. Under the left and right are USB power and 12V Aux power sockets (cigarette lighter type). See above - top row. No breakers - everything is fuses, under the seats so nobody can screw with them in flight. I already have the SL40 radio, so why not, and the Audio Panel is shown as a Garmin 345, but I might go with a PS Engineering PDA-360EZ - haven't decided yet. The Dynon internal intercom is only two place, and the COZY is a 4-place aircraft. Also, Dynon doesn't have a remote audio panel, like the Garmin G3X does (and I'm not a huge fan of doing EVERYTHING through a touch screen, either). If you know of a way to get 4-place audio panel functionality out of the dynon equipment, I'm all ears. Throttle quadrant is below and aft of the center mounting holes, so the LG switch is accessible. I put all switches in places where your pants leg can't snag on them when getting into the plane, although I 'm a BIT worried about the knobs on the HDX screens. The center switches (LB/LG, etc.) will have Steinair's SA-813 switch guards so that they can't be snagged, either. The stuff to either side of the knees has been discussed above. This is still a work in progress, but it's not going to change MUCH at this point. It won't be completely populated upon first installation (the$40K won't appear all at once), but I think I can do it in two big chunks, with all the infrastructure in place for a relatively small time sink to install the 2nd batch. Then, when the EFII system goes on the engine 3 - 5 years down the road, I won't have to change the panel either...

Hope this helps explain what I'm doing and why. I can certainly be convinced to do something else, if the ideas are good .

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13. Jan 3, 2019

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Since people are posting panel pics. here is my aforementioned one.

Its very out of date now (designed in 06). The Panel was designed to accommodate as many as possible whims of marketing which was a right pain in the axx. The panel with the flight instruments and avionics stack is shock mounted which costs a lot of space by the time one allows for movement (1/2" all around) although with solid state panels there isn't any gain from doing this as far as I can tell.

An instrument panel could be a good place to use that 3D Glass Fabric since one isn't worried about moisture ingest / freezing.

I think CB's should be on their own removable sub panel. That way they are removable if required but the loom isn't getting flexed every time the panel comes out for instrument access.

If one has multi dimmers from different OEMs (or separate ones for LED and incandescent) make sure they all turn in the same direction, otherwise you end up with painful solutions like sticking a dimmer in odd places (see the centre console in above pic).

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14. Jan 3, 2019

### wsimpso1

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Marc Z,

Wow, really informative post. Thanks so much for sharing philosophy and details. The why's for your decisions are at least as important to me as the what's - they really help with my decision making.

No, I have no idea how to get a four seat intercom out of Dynon's two place set. I do not have the gear and landing brake issues you have. The switch guards are a great idea.

18# Last-a-Foam is the core? That stuff is not stocked and is pricey. RAF probably spec'ed it for standing crush loading from screws and the like.

I think I will build a sturdy edge frame into the airplane and then add the 3mm panel on top as you suggested.

Billski

15. Jan 3, 2019

### Marc Zeitlin

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https://www.aircraftspruce.com/catalog/cmpages/lastafoam.php

The 0.2" thick, 18 lb. stuff is in stock at ACS East.

Yep - that's what I always assumed.

That's what I'd do if I were starting from scratch - 5 ply 7725 works reasonably well, with click-bond nutplates on the forward side.

But without a previous IP to use as reinforcement, you WILL need a stiffener top and bottom for the IP - leave space for an angle bracket or something to be riveted/screwed in place. Vertically, too, near the center stack.

Shoot me an email with your contact info - I might like to stop by MI on my way to the east coast this year and see your project, if you're game. And you can see the current mishmash BS I've got for a panel .

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16. Jan 4, 2019

### wsimpso1

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I was thinking of the 30 lb/ft^3 stuff.

Glad to see I am not the only guy liking and using Click-Bond Nut Plates. Great product.

I will look forward to seeing your bird.

I am thinking that the panel will attach with screws to face of a ring bulkhead that goes full width. The ring bulkhead will structurally tie the fuselage walls together and tie into the console. I am thinking a 2" flange all the way around, and the flat facing the crew that does not have an aluminum skin will be cored. Since you are figuring 5 plies 7725, that is about the same as 2 plies TRIAX when vacuum bagged. Simple mold on a table with insulation foam forming the base for the flanges. The flanges will stiffen it up, give me a place to attach the top and glare shield, and keep me from having a sharp edge around my legs.

Billski

17. Jan 19, 2019

### BoeveP51

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Billski, The photo shows my carbon panel made by Brian Alley, www.carbonfiberwv.com. I reinforced with a piece of 063 aluminum. It is hinged on bottom so I can do any work with ease. This is in a Wittman Tailwind I am rebuilding.

Hope the photo uploaded. This was first power up.

Merle

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18. Jan 19, 2019

### don january

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For those who want to try something different. I took the fiberglass sheeted foam as used in the construction of the seat bottom of my KR-2 and made a instrument panel for my Taylor-mono. Strength is amazing and weight even better. I like that the holes are easy to get cut and sanded if needed clearance is required and you can coat what ever color Epoxy to the panel.

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19. Jan 20, 2019

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