Nose cone, Vent holes, & Corrosion from charge gas - Advice PLS

[Reid]

I'm inexperienced with electronics and deployment charges and could use some advice.

I have a Minnie-magg that I have been flying mostly successfully on motor ejection and Jolly Logic Chute release. My first launch lawn darted and I had to rebuild the nose cone so now I have a bulkhead/centering ring at the shoulder of the NC and another bulkhead that attaches to it so that I can access the space in the NC. I have mounted a Eggtimer Quasar to the removable bulkhead so that it is in the forward section of the NC.







I know the Eggtimer Quasar must see atmospheric pressure and so the compartment must be vented, the booster is well vented with 3 holes below the collar of the NC, and the bulkhead to the NC compartment is vented to the booster by 3 holes. I plan to use the quasar to deploy @ apogee (motor deploy back up) and rely on the chute release ~300' (I fly at sea level and this altitude has been fine so far)

So these are my questions:

1. Because the Quasar/electronics are vented to the booster, will the ejection gases be a problem for the electronics (corrosion)?
2. Should I vent the NC compartment directly to atmosphere (basically put a hole in the NC above the bulkheads? I am concerned about false pressure readings
3. If I should keep the vents to the booster, are there any best practices to prevent damage to the electronics?
4. Also anybody got a link to bulkhead wiring hardware for the charge well? I'd love suggestions.

 

[Kane]

You should definitely vent the avionics bay directly for two reasons: 1) the vents between the avionics bay and the airframe interior will allow combustion gases into the avionics bay which is no bueno for electronics and 2) I don't think your Quasar will be able to get accurate baro readings via such an indirect route to outside conditions.

The static pressure ports (vents) should be as close to the shoulder / flat part of the airframe as possible. The tapering of the nose cone could impact how well the ports are able to equalize the interior and exterior pressures.

 

[troj]

You don't want to vent your altimeter to where your charges are for exactly the reason you specified - corrosion and damage to your electronics.

You may also get false baro readings from the recovery system shifting within the bay during flight.

The bay should be directly vented to the atmosphere.

 

[PSLimo]

As suggested above put the vent holes as close to the shoulder as possible in the side of the NC as I've done in a Minnie Magg and worked fine.

The other problem is the bond from the plywood centering ring to the plastic NC. LOC plastic doesn't bond well and will likely pull apart during recovery.

I used a piece of allthread epoxied to the NC tip using 2 towels through the top sides of the NC to give the epoxy something to bond to.

 

[Reid]

As suggested above put the vent holes as close to the shoulder as possible in the side of the NC as I've done in a Minnie Magg and worked fine.

The other problem is the bond from the plywood centering ring to the plastic NC. LOC plastic doesn't bond well and will likely pull apart during recovery.

I used a piece of allthread epoxied to the NC tip using 2 towels through the top sides of the NC to give the epoxy something to bond to.

All thanks for the responses! Much appreciated!

PSL,
The NC was flattened on the madden (ballistic) flight. I had to dig it out of 2 feet of mud. Rebuilding was just a project side project and I had nothing to lose. After some heat and some plastic welding glue on the split seam it's more or less back to stock minus the paint and the tail being cut off.

The first MS paint diagram is a bit sloppy. The plywood bulkhead/centering ring is wedged above the shoulder of the NC. I had to squeeze the NC horizontally into an oblong shape to wedge the centering ring above the shoulder and pull it back hard against the shoulder to snap it into place. The taper from the shoulder to the tip also creates a tight fit forward of the shoulder and I mean tight! I would go so far as to say the epoxy is superfluous, unless the NC is squished horizontally a good 4" or it splits in two it can't physically go aft or forward. Putting the centering ring in the NC made it feel ROCK SOLID... since it's under tension and the centering ring is under compression. I am amazed how well it turned out, and I plan to do this with any other plastic NC rocket I make moving forward.

Do you mind if I ask how many and what sized holes you used on your Minnie-Magg?

 

[rharshberger]

I have actually had the static ports (vent holes, sample ports etc) on the curvature of the nosecones itself, the data looks like crap due to the turbulent air but the altimeter knows when its at apogee and will fire the charges at the proper time. That being said there was one instance where I made covers for the static ports (Nike Smoke nose cone) and that seemed to not work well at all, since the port covers might have acted as a venturi type vacuum device...and actually pulled air from the nose cone since the charges fired shortly after boost (this time WAS NOT at drag separation) after removing said covers the rocket has flown normally every time thereafter with the same altimeter in the nose cone. I have multiple rockets with the static ports on the curve/ogive of the nose cone all flown many times.

 

[PSLimo]

All thanks for the responses! Much appreciated!

PSL,
The NC was flattened on the madden (ballistic) flight. I had to dig it out of 2 feet of mud. Rebuilding was just a project side project and I had nothing to lose. After some heat and some plastic welding glue on the split seam it's more or less back to stock minus the paint and the tail being cut off.

The first MS paint diagram is a bit sloppy. The plywood bulkhead/centering ring is wedged above the shoulder of the NC. I had to squeeze the NC horizontally into an oblong shape to wedge the centering ring above the shoulder and pull it back hard against the shoulder to snap it into place. The taper from the shoulder to the tip also creates a tight fit forward of the shoulder and I mean tight! I would go so far as to say the epoxy is superfluous, unless the NC is squished horizontally a good 4" or it splits in two it can't physically go aft or forward. Putting the centering ring in the NC made it feel ROCK SOLID... since it's under tension and the centering ring is under compression. I am amazed how well it turned out, and I plan to do this with any other plastic NC rocket I make moving forward.

Do you mind if I ask how many and what sized holes you used on your Minnie-Magg?

3, 3/16" and flown several times without issue.