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Bulkhead feedthrough wire

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SaturnV_

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Hey all,
I am in the process of redoing my feedthrough wires for my bulkheads. Previously, I had threaded rod studs that used nuts to clamp down wires, but those were a bear to work with. So, I am switching to terminal blocks. However, I have one question: do I need to seal the hole that the wire travels through? If not, it would simplify a lot of things. The reason I'm asking is because one of the Apogee videos (
) doesn't seem to be sealing the hole, which makes me wonder if I even need to.

Any help would be much appreciated!

Thanks for your time.

EDIT: Just in case anyone is wondering about the rocket size, it is a 2.1" Wildman Darkstar.
 

warnerr

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Forgot to seal my wire pass-through hole before launch. The result was my expensive electronics had a splash of grey from the black powder. Very corrosive. Suggest you always seal as best you can!
 

SaturnV_

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Forgot to seal my wire pass-through hole before launch. The result was my expensive electronics had a splash of grey from the black powder. Very corrosive. Suggest you always seal as best you can!
Gotcha, will do! Thanks for your reply.
 

A-N-D-R-E-W

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As Joe mentioned I have used "ticky tack" material, or a hot glue gun to seal up the wires.
 

Rocketjunkie

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I just run the ematch wire through the hole and build the charge on the head. The other end goes directly to the altimeter. With charge holders, just run the ematch into the cup. A piece of tape (I use masking tape) over the hole will keep ejection gases out. This also has the advantage of a new wire every flight and eliminates possible failure points.
 

cherokeej

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I just run the ematch wire through the hole and build the charge on the head. The other end goes directly to the altimeter. With charge holders, just run the ematch into the cup. A piece of tape (I use masking tape) over the hole will keep ejection gases out. This also has the advantage of a new wire every flight and eliminates possible failure points.
What Rocketjunkie points out is all too true. Ejection gasses can wick under the insulation of wires and corrode the copper conductors. Upon visual inspection of a bird with many flights, everything looks fine. But under that insulation... Nasty! I've got the tee shirt, guys. That crap can and will corrode the hell out of the wires.

I fly ARLISS every year. (Heading up to BR this Sunday!) We have some Arliss-M birds with upwards of 100 flights on them. We have learned to replace those feed-thru wires on a regular basis.

Don't let Murphy get you. Given any opportunity, he'll put the whoop on you. Don't let him.
 

OverTheTop

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Consider using hot-melt glue for sealing holes like that. A really useful tool for sealing small holes, putting a small dollop to hold a connector slightly more securely or other uses. It can be sheared off without too much trouble. If you wrap your terminal block with tape (like Kapton) first and then a little fillet for finally sealing the edge around the wires etc you keep the TB clean.

As others' have said, very corrosive.
 

les

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I've used non-hardening modeling clay. Push some around the wires and hole. If you want to replace the wires, easy to pull out, wipe off old clay, put new wires in and seal again with clay
 

Bat-mite

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Even the tiniest piece of ash can ruin an electronic device, which is why people should never smoke while operating a computer.

You may be able to get away with a lifetime of flights with the holes unsealed, but it's that one time that leads to a ballistic descent that you need to avoid.
 

Steve Shannon

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Even the tiniest piece of ash can ruin an electronic device, which is why people should never smoke while operating a computer.

You may be able to get away with a lifetime of flights with the holes unsealed, but it's that one time that leads to a ballistic descent that you need to avoid.
In general that’s a very good precaution especially with the very small circuitry we enjoy now. Old through-hole circuit boards were less sensitive. Before smoking was prohibited in all company buildings, the engineering manager at a company I worked at (more than 26 years ago) used to hide behind racks of electronics that were being burned in before being installed in customer substations. He would wait until someone was passing by and then start blowing cigarette smoke between the cards so it would pour out the front, causing some stress for the passersby. He was quite the joker.
Many of those electronics are still in use.
 

jqavins

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Of course, another possibility (I'm just spitballing) is to continue using studs, and change the layout of things on the bulkhead so they're not such a bear anymore. Stainless steel hardware will hold up longer than "regular" steel in the corrosive atmosphere, and the studs can pretty easily be changes after so-and-so many flights. On the charge side I'd build up:
  1. A washer against the FG.
  2. A nut torqued hard to hold the stud permanently in place. ("Permanently" until you decide to remove it.)
  3. Another washer.
  4. A bifricated lug with the igniter wire crimped in.
  5. Yet another washer.
  6. The second nut
On the electronics side, it doesn't have be a stud at all; you could use a screw. Washer against the FG and wire or lug between it and the screw head.

The lugs are cheap enough to be disposable. We've probably all seen those lugs splay open when nuts are tightened on them, which is the reason for sandwiching it between two washers. Crimping the lug onto the wire is done away from the rocket. At the rocket you just need to get a nut driver in and get the lug into position, which is a lot easier then messing with bare wires.
 

SaturnV_

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What Rocketjunkie points out is all too true. Ejection gasses can wick under the insulation of wires and corrode the copper conductors. Upon visual inspection of a bird with many flights, everything looks fine. But under that insulation... Nasty! I've got the tee shirt, guys. That crap can and will corrode the hell out of the wires.

I fly ARLISS every year. (Heading up to BR this Sunday!) We have some Arliss-M birds with upwards of 100 flights on them. We have learned to replace those feed-thru wires on a regular basis.

Don't let Murphy get you. Given any opportunity, he'll put the whoop on you. Don't let him.
Ah, I suspected that happening. Thanks for confirming it.

Good luck at ARLISS!
 

SaturnV_

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Of course, another possibility (I'm just spitballing) is to continue using studs, and change the layout of things on the bulkhead so they're not such a bear anymore. Stainless steel hardware will hold up longer than "regular" steel in the corrosive atmosphere, and the studs can pretty easily be changes after so-and-so many flights. On the charge side I'd build up:
  1. A washer against the FG.
  2. A nut torqued hard to hold the stud permanently in place. ("Permanently" until you decide to remove it.)
  3. Another washer.
  4. A bifricated lug with the igniter wire crimped in.
  5. Yet another washer.
  6. The second nut
On the electronics side, it doesn't have be a stud at all; you could use a screw. Washer against the FG and wire or lug between it and the screw head.

The lugs are cheap enough to be disposable. We've probably all seen those lugs splay open when nuts are tightened on them, which is the reason for sandwiching it between two washers. Crimping the lug onto the wire is done away from the rocket. At the rocket you just need to get a nut driver in and get the lug into position, which is a lot easier then messing with bare wires.
Your screw idea gives me an idea... I could use a screw standoff. I'll keep thinking about it, but right now I'm leaning towards the sticky poster stuff for sealing the wire.

Thanks for your input!
 

Nytrunner

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I use masking/electrical tape to cover my terminal blocks and holes also. Gaffer tape may work and I've got to try that poster tack stuff
 

OverTheTop

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Before smoking was prohibited in all company buildings, the engineering manager at a company I worked at (more than 26 years ago) used to hide behind racks of electronics that were being burned in before being installed in customer substations. He would wait until someone was passing by and then start blowing cigarette smoke between the cards so it would pour out the front, causing some stress for the passersby. He was quite the joker.
Many of those electronics are still in use.
We used to do something similar. A fine piece of black tubing was snaked from behind the work desk to inside a piece of equipment being tested on the bench. At the appropriate time a smoker subtly made a puff into the tube and the technical officer doing the testing had kittens!
 
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markkoelsch

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I use silicone rtv. Not permanent, and I can get a really good seal with it.
 

cherokeej

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We used to do something similar. A fine piece of black tubing was snaked from behind the work desk to inside a piece of equipment being tested on the bench. At the appropriate time a smoker subtly made a puff into the tube and the technical officer doing the testing had kittens!
You wanna see a guy have kittens...

Diesel heavy rebuild shop. A guy just finished torquing the heads on a Detroit 6V-71, and runs off to his break. The shop joker walks over and drops one of the figure-8 gaskets (part of the head gasket set) in the drip pan under the engine. After break, we all come walking into the shop, and as we pass by, "Hey Richard, what's that?" and point to the gasket sitting in the pan...

One word.

Thermonuclear.
 

OverTheTop

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:):):)

You can do something similar at a launch with a spare quicklink. "Is that from your rocket?", while pointing at a link on the ground after they have put the rocket on the pad.
 

grouch

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:):):)

You can do something similar at a launch with a spare quicklink. "Is that from your rocket?", while pointing at a link on the ground after they have put the rocket on the pad.
Horrible man, just horrible.
 
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