I think I'm ready for my first DD...

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RocketSquirrel

RocketSquirrel

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Ive spent the last couple months reading and working out any problems i might run into, and still working out a few. I need to put a swivel on the main chute, and figure out how to fold everything to fit neatly in the upper tube. Might need a bigger fwd chute protector as well. The main chute shock cord is 25' 5/8" 1000014535.jpg


one thing im still trying to get ready for the aft end is the ejection charge to push everything down into the body tube. I have the drouge and protector as close as i can to the ebay to keep it from getting knocked around. Still working on optimum spacing of everything on the shock cord. The aft shock cord is 15' 3/8"

1000014534.jpg

The ebay has a RRC3 and RRC2L with two 6LR61 9v batteries. Ill swap after ground testing with new ones before first flight and check everything for continuity and correct voltage. All the tinned wires are connected firmly and in the right spot. But ill still double check!

1000014537.jpg1000014538.jpg1000014539.jpg

I have the RRC3 as the main and the RRC2L as backup. +1 at apogee, and i think its currently set up as 600' for main and 400' for its backup.

I havent calculated the bp changes yet, but im assuming it will be 1 gram for main, 1.5 backup. Also got plenty of ignitors to test with. Everyone says to not ignore ground tests, and to be okay with spending a few dollars on testing vs loosing the rocket.

Im just going to practice setting it up as if im at the table getting ready to launch. Hopefully ill be ready this weekend if weather permits!

If you have any pointers or things you see wrong dont be scared to critique, i would rather wait until its all correct than loose it from something stupid i missed.
 
Looks good to me.

One thing: The ejection charge pushes the Ebay or Nose out of the tube with force. This then pulls the Chute and cord out. Ejection charge does not push out the chute.

I also ensure the Motor ejection charge is sized correctly and this is a 'back up' to the electronic ejection. Motor eject has saved my DD rockets a couple times.

What is the Tube size and length?
Total weight?

And yes, Ground test then add a little extra BP.
 
RocketSquirrel said:
one thing im still trying to get ready for the aft end is the ejection charge to push everything down into the body tube. I have the drouge and protector as close as i can to the ebay to keep it from getting knocked around. Still working on optimum spacing of everything on the shock cord. The aft shock cord is 15' 3/8"
Click to expand...
You may want to rethink having your drogue and blanket that close to the avionics bay/charge wells. Take a look at this article by Teddy (One Bad Hawk):

https://onebadhawk.com/why-a-3rd-loop.html
 
waltr said:
Looks good to me.

One thing: The ejection charge pushes the Ebay or Nose out of the tube with force. This then pulls the Chute and cord out. Ejection charge does not push out the chute.

I also ensure the Motor ejection charge is sized correctly and this is a 'back up' to the electronic ejection. Motor eject has saved my DD rockets a couple times.

What is the Tube size and length?
Total weight?

And yes, Ground test then add a little extra BP.
Click to expand...
Makes sense about the nose cone, im mainly trying to wrap my head aroud the aft end ejection because i have to pack everything backwards from what im used to.

Its a 4" diameter, about 55" long. 2170g as of now. Still need to update the openrocket file for added weight of the bigger parachute i ordered but the plan was to launch with a i205w. might be a little too heavy now.
 
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Everything looks OK, not quite the way I would do it, but that's fine.

My only comments,
I like to have the full length of the parachute between where the chute attaches and where the blanket attaches so when the cord is pulled tight, it will positively pull the chute out of any burrito you may wrap the chute and blanket into.

Definitely ground test. Just don't go overboard with the apogee charge. Remember, when it's in the air, the parts won't be bouncing on the ground so will open further and hit the end of the shock cord harder. The apogee charge only needs to get the drogue out into the air stream. The drag of the drogue will pull all the cords out if any are left in the BT. Too large of apogee charge can cause significant shock loads on the recovery system and the momentum of the main chute and nose cone can cause the them to leave the payload tube and deploy at apogee if it hits the end of the apogee cord too hard.

If you are going to friction fit your nose cone, make sure it's tight enough you can lift the rocket and give it a small shake without the nose cone coming off.

Good luck. It looks like you got this.
 
It looks like you've done a really good job.
Unless I missed it, I'm surprised no one has mentioned your eyebolt. Generally everyone recommends using a forged/welded eyebolt. They're worth their weight in gold if somehow you end up with a high speed deployment. I've seen pictures where the eyebolts open up from the loads involved. Nice to see the locknut arrangement you're using.
Consider upgrading your eyebolt.
 
I was using terminal blocks like you have but changed to these:
1707877082880.png
Much easier to attach in the field... no tools required. These are quite rugged and I can't pull the wire out once it is engaged.
https://www.amazon.com/dp/B01KT91OEW?ref=ppx_yo2ov_dt_b_product_details&th=1

I also noticed the eyebolt. You should use a forged one or weld the ones you have closed (which is what I do)

Good luck on your flight.
 
Tech 68 said:
It looks like you've done a really good job.
Unless I missed it, I'm surprised no one has mentioned your eyebolt. Generally everyone recommends using a forged/welded eyebolt. They're worth their weight in gold if somehow you end up with a high speed deployment. I've seen pictures where the eyebolts open up from the loads involved. Nice to see the locknut arrangement you're using.
Consider upgrading your eyebolt.
Click to expand...
Good eye! Yeah i just got the apogee ebay kit for the 3.9". I probably have forged or welded ones around here. Thanks!
 
Voyager1 said:
^^^^^ This is highly recommended. When you move to redundant DD, there are many more things that need to go right.
Click to expand...
I tried searching for an example for someones checklist to start off, but seems to be something catered to what their system is dealing with. Ive made several but i keep being reminided of things i havent thought of, would you be able to share your checklist? Just to make sure there isnt anything im forgetting
 
Ground testing id call a success, i had to use more than i calculated on the main charge, apogee charge i could have used less.

For main charge i calculated .6g would give 10psi and 1g 15psi, ended up needing 1.6g to barley get the 60 inch parachute out. Might do 1.75g and 2.25g for both the main charges.

The apogee charge i used 2g. I should have used less but i thought after 3 tries of too little in the previous experiments, i just started high. It POPPED pretty loud and shot across the yard. (Should have read closer to what @Handeman said) So i think 2g will be backup and 1- 1.5g for the main altimeter charge.

Only problem from ground testing was when i was doing the last test my dad was distracting me (he was excited for company and an excuse to get off a boring work call) i should have held something softer over the back end but it nicked a corner off a fin. Probably an easy fix.
1000014575.jpg

I do have a question though. A swivel is probably more useful on the drouge since that is what hopefully stabilizes the rocket coming down. Will it be a bad idea to not use a swivel for the main? I dont have one big enough and id habe to do an 1/8" clamp to hold parachute lines to the swivel, another 1/8"clamp for the other side of the swivel, then a 1/4" clamp to secure to the 5/8th shock cord. Thats messy, id rather not. I gues what im asking is would it be better to just forego the swivel or do the crazy setup to make it work
 
RocketSquirrel said:
I tried searching for an example for someones checklist to start off, but seems to be something catered to what their system is dealing with. Ive made several but i keep being reminided of things i havent thought of, would you be able to share your checklist? Just to make sure there isnt anything im forgetting
Click to expand...
When I get to my desktop I’ll retrieve my redundant DD checklist. In the meantime, others will probably share theirs.
A couple of important additions to the standard DD checklist are:
  • If you’re using floating charge vials, separate the primary and secondary deployment charges so that they’re not too close to each other. This is to avoid the primary charge igniting the secondary charge. If using pots fixed to avbay bulkplate as you are, then not a problem.
  • Apply an apogee drogue deployment delay of 1-2 seconds on the secondary drogue charge.
  • Apply a lower altitude offset of 100’-200’ to the secondary main deployment charge.
There might be others depending upon your specific requirements.
 
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RocketSquirrel said:
I do have a question though. A swivel is probably more useful on the drouge since that is what hopefully stabilizes the rocket coming down. Will it be a bad idea to not use a swivel for the main? I dont have one big enough and id habe to do an 1/8" clamp to hold parachute lines to the swivel, another 1/8"clamp for the other side of the swivel, then a 1/4" clamp to secure to the 5/8th shock cord. Thats messy, id rather not. I gues what im asking is would it be better to just forego the swivel or do the crazy setup to make it work
Click to expand...
I have found that I don't need swivels on all but one of my chutes. I do need a swivel on almost all of my fin cans. Here's a video of my L3 bird on a Loki L840 cocktail. At about 1:10 you can see the fincan spinning quite fast as it drops under drogue. Without a swivel, it will twist up the apogee shock cord so much it will twist the drogue chute right up into the cord.

 
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Handeman said:
I have found that I don't need swivels on all but one of my chutes. I do need a swivel on almost all of my fin cans. Here's a video of my L3 bird on a Loki L840 contail. At about 1:10 you can see the fincan spinning quite fast as it drops under drogue. Without a swivel, it will twist up the apogee shock cord so much it will twist the drogue chute right up into the cord.

Click to expand...

Ill have to watch that a few more times, i wasnt ready for that guy to keep bugging you about what grain you used haha you're like IM TRYIN to watch this dude?! Haha it looks like the drouge didnt get to do its thing and luck had it at the right position to not tangle the main, are we seeing the same things?
 
RocketSquirrel said:
Ill have to watch that a few more times, i wasnt ready for that guy to keep bugging you about what grain you used haha you're like IM TRYIN to watch this dude?! Haha it looks like the drouge didnt get to do its thing and luck had it at the right position to not tangle the main, are we seeing the same things?
Click to expand...
Not really. The drogue worked just fine. The upper section stayed at about a 45° angle and the fin can did to. The fin can just spun a lot on the swivel.
The pilot chute with the nose cone opened first and pulled the deployment bag off the main chute, so it was above the main by the time that happened. The pilot, nose cone, and deployment bag is actually attached to the top of the main chute with a small line. That is why when the pilot swung left past the main, it tilted the whole main with the rocket under it to the left also. Usually it stays above the main and the main and rocket come down pretty straight with no swinging at all.
 
I do have a question though. A swivel is probably more useful on the drouge since that is what hopefully stabilizes the rocket coming down. Will it be a bad idea to not use a swivel for the main?

I have one small enough to do a1/8" clamp to hold parachute lines to the swivel, another 1/8" clamp for the other side of the swivel, then a 1/4" clamp to secure to the 5/8th shock cord. The weakest links are the 1/8" stainless quick disconnects. the swivel is rated to 890lbs but the 1/8ths are rated to 300lbs.

Thats messy, id rather not. I gues what im asking is would it be better to just forego the swivel or do this crazy setup to make it work

Handeman said:
Not really. The drogue worked just fine. The upper section stayed at about a 45° angle and the fin can did to. The fin can just spun a lot on the swivel.
The pilot chute with the nose cone opened first and pulled the deployment bag off the main chute, so it was above the main by the time that happened. The pilot, nose cone, and deployment bag is actually attached to the top of the main chute with a small line. That is why when the pilot swung left past the main, it tilted the whole main with the rocket under it to the left also. Usually it stays above the main and the main and rocket come down pretty straight with no swinging at all.
Click to expand...
I had to watch and pause a few times. I see whats going on now. Volume off and being alone makes this make sense. I guess ill just let the drouge shoot do its job and skip the main swivel. Because this would have been a mess:

1000014576.jpg

I like the idea of a pilot chute for the main but im trying to KISS for my first time. Im already wanting to wait until next month and learn more, but ive been saying this for 2 months now and maybe ill just bring it and see what the guys think about it. Shoot something else and watch other guys for once haha thanks for the time sharing that video.
 
Only thing I would say is be very careful with one's deployment electronics if using an RF tracker, I think the RRC products are pretty immune to Rf interference. I've seen a large rocket project go in that used three cheap deployment altimeters with a Garmin dog tracker GPS back in the old days.
Flier didn't ground test adequately and the high powered dog tracker whacked all three altimeters. The altimeters locked out and no events happened. A big 20 inch+ diameter rocket went in and burrowed into the cornfield. (I helped mix the Research APCP engine for the rocket too.)
The old P6K deployment altimeter kit was notorious for this. I still fly one in a rocket that doesn't include a rocket tracker and use engines that keep it in sight. Works fine by itself. Ahhhhh, I had a lawn dart with another rocket that had a P6K and a tracker. Tracker issues piqued my interest after the rocket lawn darted and I learned about deployment altimeter interference by an Rf tracker.
I strongly recommend a person ground test a rocket with bare contained ematches on the terminals. Turn everything on including the tracker and let stand for 30 minutes to an hour. If the altimeter(s) don't shut down or pop the ematches prematurely, should be good to fly.
Of course if one has purchased a combination tracker/deployment altimeter, the maker already made sure the tracker jives with the deployment altimeter. I have a couple of those units too and they work fine. I have a General Ham license so I do 70cm/400Mhz APRS tracking too and the non-licensed 900Mhz band with the commercial rocketry available units.
For a sport flier flying up high, the 900mhz commercially available now rocket GPS trackers will work fine. When I started out, there was only the Walston and the Rocket Tracker units non-directional beacon units and Yagi antenna receivers, (really freaking expensive) that I think the FCC clamped down on so I got my Ham Radio license so I had more options back then including more of the radio spectrum and got into GPS/APRS tracking very early on.
Nice thing is fliers don't have to get a Ham license to do GPS tracking now for their rockets and I think the prices are reasonable if one wants to get their rockets back.

Kurt Savegnago (KC9LDH) NAR and TRA member too.
 
The swivels are usually rated to breaking strength, while quick links are usually rated to WLL, which you multiply by 3-5 to get the breaking strength. You can easily get rid of two of those quick links: there's no reason to have two connected to each other, and you can loop the parachute shroud lines through the welded ring and pass the swivel through the loop again.
 
jmasterj said:
The swivels are usually rated to breaking strength, while quick links are usually rated to WLL, which you multiply by 3-5 to get the breaking strength. You can easily get rid of two of those quick links: there's no reason to have two connected to each other, and you can loop the parachute shroud lines through the welded ring and pass the swivel through the loop again.
Click to expand...
I tried that, the welded ring is too small to fit all the shroud lines through. That worked for me on smaller parachutes. But ill keep trying, i cant get the last one through. 20240215_224900.jpg
 
jmasterj said:
The swivels are usually rated to breaking strength, while quick links are usually rated to WLL, which you multiply by 3-5 to get the breaking strength. You can easily get rid of two of those quick links: there's no reason to have two connected to each other, and you can loop the parachute shroud lines through the welded ring and pass the swivel through the loop again.
Click to expand...
Actually after 2 hours of messing with it, finally pulled them all through and untwisted the shroud lines. It should be all good now! Thanks for pushing me to find a way! Sometimes i just need someone to say its possible
 

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