PPP - Scratch Build Rear Ejection

I decided that I wanted to build a rear ejection rocket, so I started at it.



Saw where someone had used tape on their Estes fin alignment jig in a earlier post here. Good idea. I did the same thing.



I noticed I was using the wrong nose cone from my design, so ignore the nose in the first pic.



Used 1/8" balsa and sanded down. Used Elmers filler.

Not sure where my primer and Bondo pics went. I had to fix some imperfections in the nose and wanted to smooth out the nose to body line as it was going to be glued permanently anyway. All of this is hand cut with an Xacto. It was a pain getting those CRs just right. My eyes aren't what they used to be and I have never had a real skilled hand when it comes to cutting anything straight or in a circle, but...that is what sand paper is for.

On the motor mount, I measured how much space I would need from the bottom cr to the middle cr to fit the 12" chute easily. This is a BT55 tube and I was surprised how easy everything went in there.

With everything dry, it was time for paint. I decided on purple. I never use purple, so I thought it would be a change. Decided to paint to fins smoke gray and throw a stripe on the body as well. This was using Krylon for everything.



Temp and humidity looked fine to me but look!



Uh huh....yeah. You know what that is if you used Krylon before. I have been running into quite a bit now. On my Big Daddy I blasted it with heat. White glue on papered fins has a limit though. I decided to try a little heat on this one. It was not helping though, and I was smart enough to back off. After it was dry, I whipped out some Meguires #9 (as I just had some around) to see what it might do. It is not too harsh, so....



Yep...getting somewhere. I decided to do the whole thing.



That did the trick. This is a test mule. I am not looking for show quality or anything. When I got done, the paint looked about as good as most of my rockets. I prefer a Carnuba shine over a Zaino shine on my cars, so this worked well enough for me. I did have to sand one fin down and repaint due to me blistering it with the heat gun and you cannot tell it from a polished fin that blushed.



Couldn't forget the washer picture.

I tied some kevlar from the nose to behind the front CR on the engine tube. I then tied some kevlar to the front of the center CR to a piece of shock cord that then went to the chute. I know it is kinda hard to see the config from the pictures. I do not wrap the shock cord, I lay it back and forth long-wise on the tube. As for packing the chute, I fold it like the beginner Apogee video and then lay it on the tube and spread it around as needed. Plenty of room. The chute lines are tied to a one of those Walmart fishing tackle thingies (can't remember the real name) so that the lines don't get twisted.

Time to try it out. Nice Sunday morning with a little breeze. Clear skies though. My son and I went to the local park and gave it a shot. It went up just fine and we heard the pop of the ejection charge. Sounds a little different when you are shooting a long engine tube out the rear. Well...it is coming down pretty fast. Where is the chute? What? THUNK. Reminded us of my first Big Daddy launch.



No damage. Cleaned the nose and all looked good. We came home and I reviewed the video. Well heck...I could see where the chute had come out and went it's own way with the engine, engine tube, and well...everything but the rocket. Based on the video, I went back to the park and searched. After some walking, I spotted it way in the distance and was able to retrieve it. The kevlar failed at one of my knots! I even glued it. I brought it back home and re-tied and glued the crap out of it. After it dried, we went back out and tried again.

Success!



It came down really slow. It took up a big part of the field to come down. The funny thing? It still made a nice hole in the ground! At that slow speed? I guess I need to tell people to steer clear of it when it is coming down...chute or not.

So...I have one more B6-4 engine (I built it to work on a B6-4 in our field) and ask Ryan if he wants to launch it so I can video it. He wanted to see it again too, so off we went to reload. Went up nice and...the ejection went off and... Ahhh heck... At least we were smart enough to track the chute too. The purple guided missile was heading for some kids kicking a soccer ball. I had warned them before the launch but yelled a few heads-up. Everyone was alert. It came down just inches from their soccer ball where they retrieved it and brought it back to us. Now...the chute...well, it went a ways. We searched for some time and could not find it.

The Kevlar snapped at the nose cone (or close to it).

What went wrong??? I'll tell you. I used the wrong Kevlar. This stuff is crap compared to what I have seen online. DOH! I think it was the 50# version from Red Arrow. It's not enough...for sure. I tend to learn by doing.

So...in conclusion...when it works, it worked well. No chute charring or issues like that. No wadding needed. Reload time is longer, but not terribly difficult. Pointy end would hurt if it hit someone on the head. More caution needed. I guess maybe if I didn't use the sharpest looking nose cone I had. The chute opens immediately. You could see orange right as you heard the pop.

Also something funny. On the launch that worked well...the engine still popped out past the engine hook. It landed a couple feet from where my son was taking the video. It distracted him, so he did not get a video of touch down.

Something else funny. When searching for my chute yesterday, I spotted something orange. It was a tiny piece of Estes chute from 2012. I guess someone else lost a rocket in the same area recently.

I did take some video also. Maybe I will splice one together.

Our video taking is worse than our rocket building...

[video]https://thediskwiz.com/ppplaunchtotal.mp4[/video]

Gary Byrum said:

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Nice rocket and thread. I caught the rear ejection bug a while back also. Cure was this: https://www.rocketryforum.com/showthread.php?t=69837. Enjoy!

matthewdlaudato said:

Nice rocket and thread. I caught the rear ejection bug a while back also. Cure was this: https://www.rocketryforum.com/showthread.php?t=69837. Enjoy!

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Nice! Thanks for sharing. Your build is a tiny bit more complicated than my build. Baby steps for me, I guess. I am a sloooowww builder in comparison to what I see here and my stuff is not much past skill level 1. Although I feel it should be at least 3...as long as it takes me to cut basswood and CRs. I enjoyed this build though. Another one I am working is TTW and made to handle more power. I am gaining some basic skills and learned some "don'ts" rather quickly.

My son is getting to see some pretty good mistakes anyway.

No problem. Make sure to check out the build that CZ Brat did also - he commented on my build with a link to his, which I found very helpful.