4" Punisher - (KCCO/The Chive themed) - Build Thread

[rfjustin]

That is a seriously cool build Justin....
If that 7600 case does fit what altitude does it sim to with that case in it ???
One last thing...
You're missing a Onebadhawk sticker on your workbench....lol...

Teddy

Thank you sir. Not sure about the altitude yet with a 7600 load, I would guess at least 25-26K. Send me a decal, I'll put one on the bench!

 

[rfjustin]

Got the switch band glued in place over the weekend, grabbed some stainless steel threaded rod and other misc hardware for the avionics bay, and I drilled out the aluminum plates as well. I also picked up the bolt on 75mm Aeropack as well. More to come this week and weekend...

 

[nh4clo4]

It should comfortably fit a (4) grain 75mm M. It might even fit the CTI 5.3 grain case for the M-3700. :y:

Claude... did you hear that...?


Justin

OMG! I can't believe I missed this thread.

Now subscribed

 

[rfjustin]

OMG! I can't believe I missed this thread. Now subscribed

:grin:

I drilled some more holes in the avionics bay plates for disposable ejection charges. Booster construction begins soon.

 

[tim cubbedge]

What's with the disposable charge wells? Why not something permanent?

 

[rfjustin]

What's with the disposable charge wells? Why not something permanent?

Good question, I’ll try to explain away my OCD tendencies, lol. I really like Dog House Rocketry charge wells and they have served me well. I took the basic design of DHR charge wells and applied that to a throw away system that also mimics my preferred method of routing the e-match inside the charge well. The DHR charge well, PVC caps, copper pipe, etc. all require you to route the e-match wire beside the well, fold it over, add BP, add dog barf, then tape it up. Does this method work well? You bet! I simply came up with a preferred solution (for me) by which I can route one or two e-matches inside the disposable holder by way of offset holes. If I am only routing one e-match to each charge, I only drill out one of the two offset holes. Like I said, preferred solution for me, definitely not for everybody. :wink:

 

[blackjack2564]

Ahhh...... I see what you are doing now.
I noticed that on the bottom pics of holders...only one of side hole was drilled through, now it makes sense.

 

[ECayemberg]

Good question, I’ll try to explain away my OCD tendencies, lol. I really like Dog House Rocketry charge wells and they have served me well. I took the basic design of DHR charge wells and applied that to a throw away system that also mimics my preferred method of routing the e-match inside the charge well. The DHR charge well, PVC caps, copper pipe, etc. all require you to route the e-match wire beside the well, fold it over, add BP, add dog barf, then tape it up. Does this method work well? You bet! I simply came up with a preferred solution (for me) by which I can route one or two e-matches inside the disposable holder by way of offset holes. If I am only routing one e-match to each charge, I only drill out one of the two offset holes. Like I said, preferred solution for me, definitely not for everybody. :wink:

Great explanation. And great motor choice; I think Claude will approve as well! I want to see her go on the 3700!

-Eric-

 

[SMR]

I simply came up with a preferred solution (for me) by which I can route one or two e-matches inside the disposable holder by way of offset holes. If I am only routing one e-match to each charge, I only drill out one of the two offset holes. Like I said, preferred solution for me, definitely not for everybody. :wink:

Great point. There are a hundred ways to do pretty much everything in rocketry, and the best one is ALWAYS the one that works for you.

P.S. Enjoying this build thread and anxiously awaiting arrival of my BSS (Wednesday version) 4" Punisher.

Sather

 

[rfjustin]

True to form, the avionics bay and nose cone are not quite done yet. I have been traveling for work quite a bit in the past couple of months, but hope to get back to this building this week. I need to get a few things done:
- cut 1/4-20 threaded rods to length
- position the 3D printed sled where desired
- drill vent hole and shear pin holes in nose cone
- add tubular kevlar harness to nose cone tip (I may this permanent)

More pics to come as well...

 

[rfjustin]

Got some things done over the weekend...

Avionics bay/nose cone:
- received parachute (58" standard chute with spill hole added)
- 1/4-20 threaded rods are cut to length
- positioned the 3D printed sled where desired and drilled access holes
- drilled vent hole and shear pin holes in nose cone and booster tube as well
- added tubular kevlar harness to nose cone tip (which has been glued in place as well)

Booster
- sanded centering rings, motor mount, and booster tube
- installed centering rings on motor mount
- glued the 1" strap kevlar bridle to top of motor mount
- Motor mount gets glued in the body tube this evening.

More to come...

 

[ECayemberg]

Got some things done over the weekend...

Avionics bay/nose cone:
- received parachute (58" standard chute with spill hole added)
- 1/4-20 threaded rods are cut to length
- positioned the 3D printed sled where desired and drilled access holes
- drilled vent hole and shear pin holes in nose cone and booster tube as well
- added tubular kevlar harness to nose cone tip (which has been glued in place as well)

Booster
- sanded centering rings, motor mount, and booster tube
- installed centering rings on motor mount
- glued the 1" strap kevlar bridle to top of motor mount
- Motor mount gets glued in the body tube this evening.

More to come...

View attachment 285727 View attachment 285728 View attachment 285729 View attachment 285730 View attachment 285731 View attachment 285732

Lookin' good, Justin!

Do the arming holes go through the main airframe, or just through the coupler wall? If just the coupler wall, any concern with pressure differential while inserting the cone after arming? Just curious.

Mini MWP flight?????

-Eric-

 

[rfjustin]

Do the arming holes go through the main airframe, or just through the coupler wall? If just the coupler wall, any concern with pressure differential while inserting the cone after arming?-Eric-

Switch holes through coupler wall only. Not overly concerned with pressure differential while inserting the cone after arming as the coupler has a pretty snug fit. Of course, before P4 is flown, it will be fully bench tested as well as ground tested to make sure they are no areas of concern.

As for flight, planning on mmwp...

 

[patelldp]

Switch holes through coupler wall only. Not overly concerned with pressure differential while inserting the cone after arming as the coupler has a pretty snug fit. Of course, before P4 is flown, it will be fully bench tested as well as ground tested to make sure they are no areas of concern.

As for flight, planning on mmwp...

Inserting the cone will not be the issue, removing the cone will be. If you ever need to disarm the rocket at the car or pad you run a risk of popping your charges.

 

[GRIFFIN]

Inserting the cone will not be the issue, removing the cone will be. If you ever need to disarm the rocket at the car or pad you run a risk of popping your charges.

With no motor installed in the rear of the rocket, there is ZERO chance for any "pressure issues. I have used this method on several rockets and have had 100% success. It's just like anything, learn about how to make it safe, practice that, and it will be safe.

 

[patelldp]

With no motor installed in the rear of the rocket, there is ZERO chance for any "pressure issues. I have used this method on several rockets and have had 100% success. It's just like anything, learn about how to make it safe, practice that, and it will be safe.

Understood. My point is that if the rocket is on the pad and for whatever reason it needs to be disarmed, both pulling the motor or pulling the cone will cause a drop in pressure unless the coupler is super loose. If the coupler is super tight, the bulkhead is completely sealed, and no pressure differential reaches the holes then you're in good shape.

 

[rfjustin]

Dan, I appreciate your concern here. I will bench test and ground test the flight configuration to ensure there are no issues.

 

[patelldp]

Dan, I appreciate your concern here. I will bench test and ground test the flight configuration to ensure there are no issues.

That's all I was looking for! Having had a very similar design pop a charge in my face on the pad, I'd hate to see larger charges pop in your face.

 

[rfjustin]

Build update:
- Motor mount installed
- Fins installed
- All internal injections completed

Current to do list:
- Exterior fillets (small ones, JB weld)
- Mark, drill and tap rail guide holes
- Drogue chute on the way from Spherachute
- (2) RRC+ altimeters on the way from Missile Works
- Finish putting together recovery harnesses
- Test avionics bay switching/pressure
- Ground test

 

[rfjustin]

Over the weekend, didn’t get a lot done, but knocked a couple of items off the to do list. I located and drilled and tapped all rail guide holes. I decided to drill and tap rail guide holes on all three sides of the P4 just in case any given side of the rocket gets bound on a rail or compromised in some way. I’d rather not have to drill any holes in the future through paint. I also completed 2 out of the 3 external sets and also installed the flange mount Aeropack 75.

 

[CzTeacherMan]

Looking great!

 

[ChrisAttebery]

Did you just drill and tap the tubing for the rail buttons or did you back the holes in some way?

 

[GRIFFIN]

Did you just drill and tap the tubing for the rail buttons or did you back the holes in some way?

If I know Justin (and I do) he has installed Pem Nuts

 

[nh4clo4]

Over the weekend, didn’t get a lot done, but knocked a couple of items off the to do list. I located and drilled and tapped all rail guide holes. I decided to drill and tap rail guide holes on all three sides of the P4 just in case any given side of the rocket gets bound on a rail or compromised in some way. I’d rather not have to drill any holes in the future through paint. I also completed 2 out of the 3 external sets and also installed the flange mount Aeropack 75.

View attachment 286527 View attachment 286526 View attachment 286525 View attachment 286524 View attachment 286523

5.3G casing...
:eyepop:



M3700 !
:shock:



Drag race?
:dark:

 

[CzTeacherMan]

If I know Justin (and I do) he has installed Pem Nuts

+1... I don't know him all that well, but yes I'll wager there's PEM nuts on there. I keep meaning to do this on mine. Heck, I bought 20 from MCMASTER, but I keep forgetting to install them... Until such a time that I do, I'll continue to admire Justin's handiwork.

 

[rfjustin]

Did you just drill and tap the tubing for the rail buttons or did you back the holes in some way?

Good question. Originally, I wanted to install PEM nuts. Griffin is absolutely correct that it is my preferred method. Unfortunately, while installing the first of (6) 8-32 PEM nuts (which require a 1/4" mounting hole), it bottomed out and stripped out the fiberglass material inside the tube. I may have simply tightened it down a bit too much. I should have added a nylon washer or small standoff on the outside of the tube under the mounting screw. Oh well live and learn...

I had to bail on the PEM nut idea, but I ended up using the 1/4" holes as my epoxy injection points. Since I had a good 1/4" block of epoxy on each side of each centering ring after all the injections were done, I drilled and tapped through the body tube and cured epoxy. This gave me something solid to drill and tap into without adding a crap ton of weight to the rear.

As I was applying the JB weld fillets over the weekend, I also mixed up a small batch of West Systems to laminate some 4.0 oz fiberglass cloth to cover the 1/4" holes meant for the PEM nuts... I'll post another photo or two tonight to show how this all worked out...

 

[rfjustin]

Looking great!

Thank you sir.

 

[rfjustin]

Here are some pics that show some of the fiberglass cloth patch work not sanded, light sand, and then ready for primer...

 

[rfjustin]

And the last set of JB Weld fillets and fiberglass patches...

 

[rfjustin]

Drag race? :dark: