L1 Build: Wildman Darkstar Jr

Jarhead said:

I like the look of Crazy Jim's method. I am presuming the coupler is epoxied to the NC and the rest is secured with the threaded rod. I don't have any eye-nuts, but they should be available.

thanks again guys.

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No epoxy needed (though you could if you wanted). The beauty about doing it CJ's way. Is that it doesn't permanently alter the nosecone at all, so if you wish to make changes later on it's really easy to do.



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Thanks everyone!

Jarhead said:

Very nice work.
My son is building a wild thing for his L1 which is very similar to yours. He has a question that I can't answer; how best to secure the nose cone to the coupler. He has the bulk plate epoxied (he poured CF fortified West in his coupler).
Did you epoxy the coupler into the NC? Or did you use mechanical fasteners (rivets/pem nuts)?
He is complete minus the nose cone and wants to fly his jr L1 on Saturday at thunderstruck.
He is cutting against the grain and flying naked, I hope this doesn't grow into something with dire consequences for him.
Beautiful work again. Thanks for sharing.

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I did a glueless nose cone. I used a long piece of all-thread to run from the aluminum tip down through the coupler. Then used a washer and an eye nut to fasten the coupler to the NC. This lets me be able to remove the coupler if I ever want add a tracker.

Don't have pics but there are several other threads on it.

Edited to add should have read rest of thread before responding!! Yes I did exactly what was done in CJs thread. No epoxy needed. Super easy to do. And you're not hijacking feel free to post. We're all here to help rag other out!

Time to resurrect this thread. High power launches with my club didn't really happen in the spring, and then once summer came around it was hot as can be and I had switched focus to ironman training, so didn't do much with rockets. So finally getting back to this to hopefully attempt my L1 next weekend.

Haven't decided on whether I'll do dual deploy for L1, but want to get the charges and logistic worked out in case I do, or if I fly again the same day and try dual deploy then.

For others who have built these Jr kits, what's a good starting point for amount of BP for top and bottom for testing?

And as for ground testing, the top part is easy enough, but what about the bottom part? Should I test it with the motor case in? Should I seal up the top of the motor case to prevent the gases just going out the rear? Not really sure how best to recreate how it will be in the bottom of the rocket at apogee? Wasn't able to find much searching (but maybe I just missed it in a thread somewhere).

blueapplepaste said:

Haven't decided on whether I'll do dual deploy for L1, but want to get the charges and logistic worked out in case I do, or if I fly again the same day and try dual deploy then.

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I would suggest bagging the L1 on a motor deploy flight. Eliminate the learning curve/risk of the DD setup from the cert flight. Build it for DD but go with motor eject for the cert flight. I think I used a CTI H110 2-grain White motor for the cert flight...low and slow. It's not a bad idea to fly the same motors for the first DD flights so you can see what is happening at the events.

blueapplepaste said:

For others who have built these Jr kits, what's a good starting point for amount of BP for top and bottom for testing?

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Start with one gram, expect that it will be pretty energetic. CTI uses 1.3 grams for the motor eject charge in their 38mm motors, that's not enough to hurt the DJ Jr. and enough to push out a pretty tightly packed chute in my experience. I have not tested the lower limit, but others who have told me that .75gr may be enough.

blueapplepaste said:

And as for ground testing, the top part is easy enough, but what about the bottom part? Should I test it with the motor case in? Should I seal up the top of the motor case to prevent the gases just going out the rear? Not really sure how best to recreate how it will be in the bottom of the rocket at apogee? Wasn't able to find much searching (but maybe I just missed it in a thread somewhere).

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You hit it on the head - try to recreate the conditions as close as you can. Plug up the top of the motor casing with something and pack it exactly like you will at the field. Long motor tubes take up space, so maybe less powder is needed. Tightly stuffed parachute bundles - they might act as a piston when the charge is below, but the DD charge is on top and the shock cord needs to pull the package out of the tube. The DS Jr. was my first L1 project and my first DD project, and I figured that since it was strong as heck, I didn't need to get too cute with the "perfect" soft deployment charge, I just used ~1 gram top and bottom (since I think that is what Tim suggested) and let 'er rip. Never had an event failure.

And why should I, when there are so many other failures I can make.

Jarhead said:

Thanks for the suggestions guys.
I may be hijacking the thread so if I should move this please let me know.
If I use fasteners through the NC into the coupler what is the impact on altimeter venting in future DD situations? Will turbulence from the screw heads cause erratic pressure in the av-bay, possibly giving erroneous altimeter readings? I personally like using Pem-Nuts and button head cap screws because they function well and are aesthetically pleasing. I don't however want to have issues with DD later on because of a poorly planned decision today.
I like the look of Crazy Jim's method. I am presuming the coupler is epoxied to the NC and the rest is secured with the threaded rod. I don't have any eye-nuts, but they should be available.
If the fasteners will not impact the avionics, I will likely have him go that route because I can teach him something I am already comfortable with.
thanks again guys.

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Couple of notes for you to consider:
(1) Altimeter will live in the AV bay coupler, not in the nose cone, in a typical build. Tim's instructions give pretty good advice on how to align those holes. Basically, you don't want the fasteners pinning the AV bay to the payload (upper) tube to be directly over the AV bay vent holes. Align them 60 degrees out of phase so that the hardware is over the mid-point of the two vent holes below it.

(2) As noted, CJ's method relies on a central threaded rod to replace the bolt holding the nose cone in. This works fine, but I reverted my DS3 to a traditional permanently attached shoulder when I added a tracker to the NC. There were two reasons for this. After a K-motor flight on an extremely hot day (110+ at Black Rock) I found that the coupler was wedged so tight into the NC that we could not remove it. I tried everything short of heating it back up to 120 degrees--we could not get it to budge. And the shear pin holes were no longer aligned, since it had shifted upward about the diameter of a shear pin. Since I had effectively a fixed coupler in the nose cone, I just added some JB weld to the inside seam and called it a day.

The other reason to think about ditching the threaded rod is that if you plan on flying trackers in the NC, the proximity of the threaded rod to the antenna of the tracker will degrade the usable range. Using an Eggfinder system (900Mhz), we observed a 20% degradation in usable range with the antenna parallel to the rod vs. being nowhere near the rod. Test was done line of site over the ground, which is not exactly the same as transmitting through clear air, but it was enough for me to ditch the threaded rod in the NC - to me it is just a solution looking for a problem.

#EndingHijack

I may oversize my charges, but I used 1.5 grams for apogee and 2.7 for the main. That chute was guaranteed to come out.

blueapplepaste said:

Time to resurrect this thread. High power launches with my club didn't really happen in the spring, and then once summer came around it was hot as can be and I had switched focus to ironman training, so didn't do much with rockets. So finally getting back to this to hopefully attempt my L1 next weekend.

Haven't decided on whether I'll do dual deploy for L1, but want to get the charges and logistic worked out in case I do, or if I fly again the same day and try dual deploy then.

For others who have built these Jr kits, what's a good starting point for amount of BP for top and bottom for testing?

And as for ground testing, the top part is easy enough, but what about the bottom part? Should I test it with the motor case in? Should I seal up the top of the motor case to prevent the gases just going out the rear? Not really sure how best to recreate how it will be in the bottom of the rocket at apogee? Wasn't able to find much searching (but maybe I just missed it in a thread somewhere).

Click to expand...

Dad Man Walking said:

(2) As noted, CJ's method relies on a central threaded rod to replace the bolt holding the nose cone in. This works fine, but I reverted my DS3 to a traditional permanently attached shoulder when I added a tracker to the NC. There were two reasons for this. After a K-motor flight on an extremely hot day (110+ at Black Rock) I found that the coupler was wedged so tight into the NC that we could not remove it. I tried everything short of heating it back up to 120 degrees--we could not get it to budge. And the shear pin holes were no longer aligned, since it had shifted upward about the diameter of a shear pin. Since I had effectively a fixed coupler in the nose cone, I just added some JB weld to the inside seam and called it a day.


#EndingHijack

Click to expand...

Yes this happened to me....I have since revised the method by gluing in the NC a stop, made of a 1/4 wide section of the NC coupler....for the shoulder to butt up to. Preventing it from moving and mis-aligning the shear pin holes. I've seen stops made of several items, including wood & nuts epoxied in as stops.

The next step of evolution was Making the shoulder another bay, by putting a small 1/2in vent band on it.....also prevents forward movement of the coupler and allows using it as a bay. Yes the threaded rod is now gone and an eyebolt goes on the metal tip to attach shock cord to if need be.

The one thing the glue less NC did was keep the integrity of everything with out glue, so further development could happen, with out being stuck with a glued in shoulder.:grin:

As far as BP...that depends on how tight a fit you have and how many pins.

I use 2 shear pins 2-256nylon and 1.25 grams for main.
For apogee 1-1.25 depending on how long a motor I use. With long ones there is very little room left over for gear, so no need to make a cannon charge. I've use as little as .75 gr

As always, ground test. Everyone builds a little different so that must be considered.

Dad Man Walking said:

I would suggest bagging the L1 on a motor deploy flight. Eliminate the learning curve/risk of the DD setup from the cert flight. Build it for DD but go with motor eject for the cert flight. I think I used a CTI H110 2-grain White motor for the cert flight...low and slow. It's not a bad idea to fly the same motors for the first DD flights so you can see what is happening at the events.



Start with one gram, expect that it will be pretty energetic. CTI uses 1.3 grams for the motor eject charge in their 38mm motors, that's not enough to hurt the DJ Jr. and enough to push out a pretty tightly packed chute in my experience. I have not tested the lower limit, but others who have told me that .75gr may be enough.



You hit it on the head - try to recreate the conditions as close as you can. Plug up the top of the motor casing with something and pack it exactly like you will at the field. Long motor tubes take up space, so maybe less powder is needed. Tightly stuffed parachute bundles - they might act as a piston when the charge is below, but the DD charge is on top and the shock cord needs to pull the package out of the tube. The DS Jr. was my first L1 project and my first DD project, and I figured that since it was strong as heck, I didn't need to get too cute with the "perfect" soft deployment charge, I just used ~1 gram top and bottom (since I think that is what Tim suggested) and let 'er rip. Never had an event failure.

And why should I, when there are so many other failures I can make.

Click to expand...

Yes, I think you're right to skip DD. Launching it on H225, so it will get up there but should be anything too crazy.

And advice on BP charges is great. Thanks for the help! Looks like I have some testing to do this weekend.

blackbrandt said:

I may oversize my charges, but I used 1.5 grams for apogee and 2.7 for the main. That chute was guaranteed to come out.

Click to expand...

You may want to ground test this, as too big a charge can be as bad as too small. If you "overcharge", you might need a crazy length of SC or you might damage the guts of the bird. Google the web, as there are a few calculators out there for the amount of BP needed to pressurize a given diameter and length

Quick question; this is my first time using a chute protector (I've always used dog barf/recovery wadding). I was practicing packing the rocket and was trying to do it "burrito" style, but I can't get the chute small enough to be fully wrapped in nomex (9x9) and fit into the rocket.

I can get it to fit if I just wrap one half of the parachute. My thought is if the wrapped half is pointing towards the ejection charge, that should suffice as the back half doesn't need to be protected as it won't get hit with any ejection charges/hot gases. Correct?

Would this work?

Might work, but I'd suggest starting with a larger blanket (12x12) and doing the full burrito that way. I've had mixed results, and some burnt chutes to show for it, when I tried using the nomex as a "blast shield" below the parachute, even with some dog barf in there underneath the nomex.

I think that the size recommendations that come with the nomex are just starting points anyway. Depends on what type of chute/how big it is, whether you need to pack it very short or have room for it to be a longer/thinner package, your folding technique, etc. I can make 12x12 work for a Darkstar 3" main, just barely (and it might take a couple of tries to get it right). But I also can use the 12x12 on a Darkstar Junior main, and have a little easier time packing with less worry that I got it perfect.

Dad Man Walking said:

Couple of notes for you to consider:

(2) As noted, CJ's method relies on a central threaded rod to replace the bolt holding the nose cone in. This works fine, but I reverted my DS3 to a traditional permanently attached shoulder when I added a tracker to the NC. There were two reasons for this. After a K-motor flight on an extremely hot day (110+ at Black Rock) I found that the coupler was wedged so tight into the NC that we could not remove it. I tried everything short of heating it back up to 120 degrees--we could not get it to budge. And the shear pin holes were no longer aligned, since it had shifted upward about the diameter of a shear pin. Since I had effectively a fixed coupler in the nose cone, I just added some JB weld to the inside seam and called it a day.

The other reason to think about ditching the threaded rod is that if you plan on flying trackers in the NC, the proximity of the threaded rod to the antenna of the tracker will degrade the usable range. Using an Eggfinder system (900Mhz), we observed a 20% degradation in usable range with the antenna parallel to the rod vs. being nowhere near the rod. Test was done line of site over the ground, which is not exactly the same as transmitting through clear air, but it was enough for me to ditch the threaded rod in the NC - to me it is just a solution looking for a problem.

Click to expand...

I also had a "glueless nosecone" setup that had issues. This is in a 3" FW fibreglass cone.

The first being that my shear pin holes didn't stay aligned as the coupler/shoulder shifted even the tiniest bit in use. So I ended up gluing the shoulder in as per usual.

The second being tracker issues that I believe were caused by the long length of all-thread running through the cone, along with that big aluminum tip (I use a BRB900 transmitter wrapped in bubble-wrap and stuffed into the cone). I'm currently re-working the nose-cone setup, going back to the standard tip attachment and getting rid of the all-thread.

So, really I'm going back to a "standard" build on my nose cone. Glueless looks cool on paper, but in the end I'm going with good old epoxy.

s6

Looks good nice build.

Dad Man Walking said:

Might work, but I'd suggest starting with a larger blanket (12x12) and doing the full burrito that way. I've had mixed results, and some burnt chutes to show for it, when I tried using the nomex as a "blast shield" below the parachute, even with some dog barf in there underneath the nomex.

I think that the size recommendations that come with the nomex are just starting points anyway. Depends on what type of chute/how big it is, whether you need to pack it very short or have room for it to be a longer/thinner package, your folding technique, etc. I can make 12x12 work for a Darkstar 3" main, just barely (and it might take a couple of tries to get it right). But I also can use the 12x12 on a Darkstar Junior main, and have a little easier time packing with less worry that I got it perfect.

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Ok. Thanks for the help. I have to pack the chute longer to keep it thin and the 9x9 nomex won't fully cover it. No time to order new nomex so will probably use an ironing board cover fabric if I can find some at Joanne's. Or just cut up and ironing board cover.

Should that be good enough if chute is fully wrapped in that fabric? Or maybe use nomex as blast shield and keep chute fully wrapped in the ironing board material?

Bagged my L1 yesterday! Everything was uneventful. Flight was on a CTI H225. Simulated to 2100 feet, but only went 1604. No idea why there was such a big discrepancy (simulation was done with exact weight of rocket). The motor was right at a year old, and instructions said not to use a motor over a year old. Could that have played a role and the motor wasn't fully up to snuff?

The wind was picking up on my flight, so 500 less feet meant that much less of a hike, so wasn't a big deal.

Next up is some dual deploy action. Going to fly the hell out of this thing for a while; no immediate plans for L2 anytime soon.

My wife managed to snap a pretty decent pick of the launch with her cell phone.

OUTSTANDING! Congrats on a job well done.

blueapplepaste said:

Bagged my L1 yesterday! Everything was uneventful. Flight was on a CTI H225. Simulated to 2100 feet, but only went 1604. No idea why there was such a big discrepancy (simulation was done with exact weight of rocket). The motor was right at a year old, and instructions said not to use a motor over a year old. Could that have played a role and the motor wasn't fully up to snuff?

The wind was picking up on my flight, so 500 less feet meant that much less of a hike, so wasn't a big deal.

Next up is some dual deploy action. Going to fly the hell out of this thing for a while; no immediate plans for L2 anytime soon.

My wife managed to snap a pretty decent pick of the launch with her cell phone.

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Congrats. I just built one of these (actually still building the Av-bay), except as the two stage version.

I love the paint job you used, very unique indeed.

Also, I've never had an issue with using a motor that's over a year old. I've used some that are 2.5-3 years old.

blackjack2564 said:

OUTSTANDING! Congrats on a job well done.

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Thanks!!

T34zac said:

Congrats. I just built one of these (actually still building the Av-bay), except as the two stage version.

I love the paint job you used, very unique indeed.

Also, I've never had an issue with using a motor that's over a year old. I've used some that are 2.5-3 years old.

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It's such a great kit. Just love the look of it. And the 2 stage Is gonna be insane!

Good to know about the motors. Maybe it was just "one of those things." I'm curious how close the sim and next flights will be

blueapplepaste said:

Bagged my L1 yesterday!

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Congrats on the cert flight. And as our LCO says after every successful L1 cert flight - "Welcome to high power rocketry. Now open your wallet!"

How did things work out with the chute packing?

I did L1 on the DS Jr with a 2-grain CTI motor as you did, added dual deploy and flew it a bunch of times to get the kinks worked out, and then flew the same rocket for my L2 cert on a CTI J290 to 5700+ feet. Biggest flight has been 7200 feet on a CTI J354. We've had a lot of fun with it. Enjoy yours, and get ready to shell out a lot more money for motors that you were doing up until now.

Yeah. My wallet is definitely going to be a lot lighter!!!

Chute lacking went fine. Was one of those things I was making more complicated than it should have been. Did some googling and reading through old threads and made a larger chute protector using ironing board fabric from fabric store. Was $12 for 2yds, which is going to be a ton of protectors! I just sewed two layers together so both sides were the protective side facing outwards. Was able to fold chute long and skinny and easily fully wrap it up.

And I don't think I'll be able to use the DS Jr for level 2. We have a 5k foot ceiling so it would be close. For level 2 I want to do a short and fat rocket for something different. But again, that's a long way off.