So I have never encountered this situation in any of my builds. And I have done plenty.

I decided to build piece milled an old poorly designed quad frame along with other pieces from other quads to make something new. Build log to come.  I broke a few key pieces of the frame  so I couldn't repair it. The stack will be 4 long metal screws. It is for structural and to hold all the electronics. I went with quadrant ESCs and the mounting hole is connected to ground. Since my stack uses metal screws  it will ground the ESCs to the carbon fiber frame.  My question is, will this have any adverse effects? I assume it should be fine.  What are your thoughts.

To my mind I think it should be OK, as long as there are no other / only GND contacts to the CF from other components, but hitting a power line might prove fatal, electronically? 

Just 2 cents, not an opinion formed from any kind of training in the field of crashing quads into power lines! 

Only problem I can think of would be if, for whatever reason, a positive touches the frame and shorts it out. And this would have to be on the sides of the frame as the top/bottom surfaces normally have a clearcoat that aren't conductive. 

I've never actually tested this, but aren't those metal rings (in the mounting holes) isolated? Do you get continuity between the ring and ground pads?

EDIT: 

Quote:I went with quadrant ESCs and the mounting hole is connected to ground

Sorry, you did mention that they are.

Hmmmmmm..........Off the top of my head, I can't think of an issue with it...except maybe your FPV feed?  I'm just wondering if the entire frame is electrically "active", if it may cause interference?  If it were me, I think I would try and avoid that, not because of any concrete reason, but more so that I would feel more comfortable if all the circuits are isolated from the frame.  Things can go bad in a hurry in the event of a bad crash and my concern would be that it may exacerbate any problems (especially if you were to crash into power lines).

Funny, I'm doing pretty well an identical setup on my Cerb build with the same metal screws.  I was also concerned about ESCs grounding to the frame so I checked with Martin at BrainFPV and he informed me that it would have no effect whatsoever.

Everyone opinion has been greatly noted. I was worried about ground noise because VTX antenna are usually mounted on the carbon as sirdude alluded to. Also worried about positive touching the carbon but there seems to be a coating xcalibur mentioned. Thanks for the info RENOV8R, this actually puts my worries away.

(15-Mar-2018, 11:09 AM)Tom BD Bad Wrote: To my mind I think it should be OK, as long as there are no other / only GND contacts to the CF from other components, but hitting a power line might prove fatal, electronically? 

Just 2 cents, not an opinion formed from any kind of training in the field of crashing quads into power lines! 

I think hitting a high voltage power line is fatal regards of grounding. Ha.

I don't know why but I've never liked the idea of using metal machine screws for my stacks, so I use nylon machine screws. Ace hardware, Fry's electronics, Home depot and Amazon all sell them. They may seem flimsy to some but I've never had an issue using them and have yet to break one in a crash. Just throwing that out there.

(15-Mar-2018, 04:29 PM)Sugs Wrote: I don't know why but I've never liked the idea of using metal machine screws for my stacks, so I use nylon machine screws.  Ace hardware, Fry's electronics, Home depot and Amazon all sell them.  They may seem flimsy to some but I've never had an issue using them and have yet to break one in a crash.  Just throwing that out there.

Absolutely I use nylon whenever I can, they're plenty strong.  Only reason I used metal ones is the frame has countersunk holes and I could only find metal counter sunk 

First quad I built had both positive and negative polarity on the screw holes of the ESC. I used metal screws to mount it.

Carbon fibre burns quite nicely.

Personally I would not connect anything to the frame after that experience.

When replacing the battery in a car, you always disconnect the negative side first. Why? because if you don't, the entire car chassis is the ground and its easy to accidentally touch the car with the wrench you're using to disconnect the positive and you could arc weld your wrench to the car or worse.

Applying that logic here, everything should be functionally fine if the chassis is grounded. That's how airplanes are after all. But there is a risk now that anything positive polarity touching the frame will now short out where it wouldn't before. It's probably best to avoid it, but if you do, it should work fine, just require a little more care with batteries and power sources.

(15-Mar-2018, 05:44 PM)RENOV8R Wrote: Absolutely I use nylon whenever I can, they're plenty strong.  Only reason I used metal ones is the frame has countersunk holes and I could only find metal counter sunk 

Yeah, I think those are the harder ones to find.  I do prefer to walk into a hardware store and pickup what I need but when I can't its eBay or Amazon.  I found some.

https://www.amazon.com/uxcell-M3x20mm-Ph...ountersunk

Now I am torn on what I should do now. I have always used nylon screws, but I have to use the metal screw for structure in this build.

(16-Mar-2018, 04:00 AM)voodoo614 Wrote: Now I am torn on what I should do now. I have always used nylon screws, but I have to use the metal screw for structure in this build.

So this raises the question... If the board designers thought it might be an issue why did they ground the mounting holes to begin with? 

You can always try and insulate the screw from the mounting holes somehow. Few options that come to mind:

1. Clear nail polish (not sure about longevity)
2. Heatshrink (if space allows)
3. Silicone modified conformal coating (This would be my go-to if I could find some in SA)
4. Liquid electrical tape

Try a few options and test for continuity between the hole and the screw. 

https://www.amazon.com/MG-Chemicals-Sili...ating&th=1

Thanks for suggestions. You make a great point about design. I think I will just go for it.