L2 Kit Recommendation

[loopy]

Yes !

That motor didn't exist back when I had my Iris but an AT RMS 38/720 J500G should fly a just little higher and quicker than the J350W in a 4-inch Iris.

And I REALLY want to fly one in my 1.9 inch "T'Pring's P'Toy" when I've got the right site and weather ( 170 ft/sec off an 8-ft rail, Mach 1.37 near burnout and 7,500 ft apogee )...

-- kjh ( whee ))

It's SUCH a great motor. I flew it in my LOC Expediter for my L2 (I turned the transition into an altimeter bay), and it absolutely lasered off the pad. Incredible motor.

 

[JackC]

You want to certify at LDRS... which is in three and a half weeks... and you haven't even ordered a rocket.

Your gumption is impressive.

LOC Warlock with 54mm motor mount. You could probably even build it with wood glue and skip the epoxy, which should speed things up.

I second Antares JS. The Warlock is an easy L2 cert bird. A baby J motor, a rocket that can be built with wood glue and an awesome drag queen (keeps her low and slow, easily seen during the flight and recovery). What’s not to love about her?

 

[jqavins]

[M]y 1.9 inch "T'Pring's P'Toy"...

Wouldn't it be easier to just call that Stonn?

 

[jqavins]

There are a few good J-Motors for your level 2 -- like maybe the AT DMS J435WS ... or ... if you have access to AT RMS 54/852 motor hardware, an AT J460T looks good too.

I did a look on ThrustCurve.org for motors in the low to mid J range, without crazy or very low thrust, and came up wit five. Three of them are CTI motors. When I thought I would design from scratch I planned to design around those. Now that I'm using a kit, I need to download the RS file from LOC and do some sims to decide on a motor.

I'll be buying a case as well as a load (or an SU motor) so CTI or AT really doesn't matter much. I focused on the CTI motors initially because all my other hardware, 24, 29, and 38 mm three grain, six grain, and spacers, plus a 54 one grain are from them; I'm a CTI guy, but it doesn't need to stay that way. Also, if I go with 38 mm instead of 54 then I wouldn't need to buy a case, but I would need to order or make an adapter in a hurry. (Hmm, I have a 54 to 38 adapter from Aeropack, so I could order an Aeropack retainer for this and just toss the LOC one in a drawer when it arrives. And I'd only need to buy the fixed part.)

 

[kjhambrick]

Wouldn't it be easier to just call that Stonn?

Yes but that wouldn't confuse the RSO / LCO like T'Pring's P'Toy does

 

[tsmith1315]

You got this in the bag, Joe!

Yes but that wouldn't confuse the RSO / LCO like T'Pring's P'Toy does

And it wouldn’t make as good of a companion to Spock’s Johnson…


https://www.rocketryforum.com/threa...twenty-eight-year-old-i357t-and-lives.184872/

 

[NTP2]

I did a look on ThrustCurve.org for motors in the low to mid J range, without crazy or very low thrust, and came up wit five. Three of them are CTI motors. When I thought I would design from scratch I planned to design around those. Now that I'm using a kit, I need to download the RS file from LOC and do some sims to decide on a motor.

I'll be buying a case as well as a load (or an SU motor) so CTI or AT really doesn't matter much. I focused on the CTI motors initially because all my other hardware, 24, 29, and 38 mm three grain, six grain, and spacers, plus a 54 one grain are from them; I'm a CTI guy, but it doesn't need to stay that way. Also, if I go with 38 mm instead of 54 then I wouldn't need to buy a case, but I would need to order or make an adapter in a hurry. (Hmm, I have a 54 to 38 adapter from Aeropack, so I could order an Aeropack retainer for this and just toss the LOC one in a drawer when it arrives. And I'd only need to buy the fixed part.)

On the CTI, maybe consider the availability of their motors.

 

[jqavins]

Yes but that wouldn't confuse the RSO / LCO like T'Pring's P'Toy does

OK. I'm just concerned that it's tempting the rocket gods to impose a T'Prang.

 

[jqavins]

On the CTI, maybe consider the availability of their motors.

Well, of course. Once I know what I need given the real weight, I'll contact vendors to buy one for on-site pickup (an advantage of doing this at a major event) and I'll have a few alternatives to match up to inventory.

 

[-Slick-Ice]

I loved my scratch 4-inch Iris @jqavins

LOC says their Iris weighs 5.5 lbs which seems a little light but maybe that's just me and mine with an Av-Bay and TTW fins with the 12 filets I applied ?

As for nose weight -- mine didn't need any, even with 1/4 inch thru the wall fins flying RMS 54/1706 motors.

I would believe under 6LBS. Mine is 7.5lbs but the electronics bay is probably 1.5lbs by itself and I would attribute another .5lbs for the kevlar shock cord. Absolutely no reason for nose weight. It is over 2 cal stability with a K550 in it.

 

[RobertH3]

Larger diameter equals less altitude. You get to see it at work. If the day is calm y

 

[ksaves2]

Am against planned out of sight cert flights as a rule. Yes I realize they're legal if that's what a flier wants to do but...... A flier should plan them to be within sight when certing. Practice that way so the events can be seen and the flight parameters can be tested and adjusted before the attempted certification flight. Sometimes it just takes one test flight to dial the rocket in. Once certed can do the outa-sight stuff and depend on electronics and the launch sight size to recover the future rockets.
I've seen Rf, GPS and APRS/GPS rockets go lost before with an intact tracker. Tracking devices increases the chances of getting a rocket
back but it doesn't lower the risk of loss to "zero". Also seen several lawn darts where the tracker survived and took the flier to the hole in the
ground that completely swallowed the rocket. Should be easy to find a lawn dart but sometimes it isn't. A tracker that survives allows one to dig out hardware back that is still usable.
A main chute at apogee can result in a total loss if the rocket hits a thermal and is taken out of range. If it then lands in a body of water sight unseen, will most likely be a total loss.
It's sometimes hard to get a bearing fix with Yagi antenna/attenuator tracking before a rocket drifts out of sight or radio range. Best to make plans if expecting to track with a radio and a vehicle. On road, best to have a driver and an experienced person running the tracking receiver and plan for that eventuality if there's a strong prospect it could occur during a given flight.

Oh one addition. I saw some hard-core trackers that had a car seat with a seatbelt bolted into the bed of a PICKUP facing backwards! Tracker would belt in and direct the driver with a radio handi-talkie while trying to get a fix with the Yagi antenna/attenuator. This was before widespread GPS tracking.

 

[jqavins]

That all sounds like good advice. My plan is pretty well set at the moment.

• I will be flying with the lowest impulse motor that gets me good rail exit speed.
• I will be flying a GPS tracker.
• I will be using a JLCR to unfurl the main at 300 ft.

 

[NTP2]

That all sounds like good advice. My plan is pretty well set at the moment.

• I will be flying with the lowest impulse motor that gets me good rail exit speed.
• I will be flying a GPS tracker.
• I will be using a JLCR to unfurl the main at 300 ft.

What about the fins?

 

[jqavins]

I'm still waffling over that, but leaning toward building it stock.

 

[loopy]

I think stock is the way to go here, especially given your compressed time frame. You'll have plenty of opportunity/time to use those custom fins and take the time to make sure you're doing it right after you get the cert.

If you already have the AP 54/38 adapter, then yes - get the AP 54mm retainer and call it a day. That is what I use, and it's wonderful.

The 38mm J loads can have decently high thrust, but it's a relatively short duration (other than things like the J570), so any 38/720 J load should be fine and not get that big of a rocket out of sight. My LOC Expediter when just over 4000' on the J500, so it stayed in sight the whole time for my cert, and it's a relatively light rocket.

 

[jqavins]

[A]ny 38/720 J load...

If I don't buy a new case, it's either CTI 38 mm or single use.

 

[loopy]

If I don't buy a new case, it's either CTI 38 mm or single use.

Ah - my bad...I misread and thought you had the AT 38mm cases.

 

[ksaves2]

That all sounds like good advice. My plan is pretty well set at the moment.

• I will be flying with the lowest impulse motor that gets me good rail exit speed.
• I will be flying a GPS tracker.
• I will be using a JLCR to unfurl the main at 300 ft.

Try deploying the main up higher. Shoot you're using a GPS tracker to find the thing. Trying to purposely recover it in sight is insane. If trying to recover in sight, no need for a GPS tracker with the lower impulse motor!!!!! I usually use 1000 to 750ft main deploys at venues that allow it. I'd rather lope to an intact rocket than walk to a close "slam dunk" to pick up the pieces with a too low or too small main chute. Especially on a CERT flight!!
Sure if you're doing multiple test flights to see if the JLCR has time to get the harness and chute fully deployed before touchdown on the cert flight o.k.
But crack a fin or break something and your sponsor's may refuse to sign. Cert flights are not the time to try and do heart stopping recoveries. Save that for when the "cert" is in the bag and the launch is sparsely attended for flights thereafter.
I saw many a JLCR certification flights fail because the flier chose something like a 300 foot main deployment and the rocket slammed into mother
earth as the deployment harness failed to fully deploy. The larger the mass of the rocket and deployment devices become, the worse the problem will be along with the need for higher main deployment altitude. Kurt

 

[cerving]

My recommendation is the Giant Leap Vertical Assault. It's a 3" FG kit, but it has an ACME fin can so it's super easy to build.... and it's nearly indestructible. It's designed for dual-deploy, but you don't have to fly it that way... with a J motor you can get away with single deploy. Just about everything except electronics comes with the kit, including Nomex and parachutes.

 

[Art Upton]

I think 300 feet is too low. It's a close call even on an Estes Asender sometimes.

Watch, and Watch how to fold the JLCR chute on John Bean's videos. If you just chose random videos you get others doing it their way and not the maker's way.

When I used my JLCR the first time I didn't watch a video, "I've been packin' chutes for decades, I know how to do it" Well that was Not the way to do it, release opened but chute did not catch air. Got a bend in the tube by the fins on my "test" rocket. [A 2" Estes Majestic on 29mm BP motors ]

Tried again, bend got a little worse on the test rocket. OK OK, watch the video, watch them pack it, learn the way to do it...

Then it worked on the test rocket and then my intended rockets. Next launch I get to go to, I am watching the video again, its been since 2021 that I got to fly so I will learn "That's the way you do it" all over again.

Best one in 2018 bringing back my LOC Caliber ISP painted like a D-Region Tomahawk, even the decal said D-Region ISP The I-65 is a plugged 54mm motor an took it to just touch 1 mile, so the payload bay had a Strato Logger fire only an Apogee charge, and the JLRC was set for a 700 or 500 main, I can't remember. I did not want to turn that rocket into Dual Deploy. I like the JLCR method now.

edit: Weight of the rocket with no motor was 3.0 pounds. Fin can built with Gorilla glue, tube slotted to fit over fin can. No outside fillets. Fins only sealed to tube to keep air out.

RSO was wanting 20 degree tilts into the wind, due to wind. Rocket weather cocked really bad into the wind. I would have tilted it with the wind , it would have gone mostly straight up and got a lot more altitude.

 

[ksaves2]

I think 300 feet is too low. It's a close call even on a Estes Asender sometimes.

(Snip for brevity's sake)

Art's been around longer than me and am heartened he agrees with me that 300 feet is too low. Well if a flier has a well behaved rocket on a chute release, they don't mind trashing, I can't slam them for testing up to a 300 foot JLCR main deployment for the wow factor as long as they can get it to work 100% of the time.
I saw a 300 foot main JLCR deployment one time that was successful but it was blind luck of the flier. The harness was too long, the rocket was "smallish" which was a plus and I don't know why he carried such a long harness in such a small rocket.
The main charge blew, the harness took forever to come out and the fins were inches off the ground when the chute fully deployed and saved the recovery.
I went up to the flier and told him emphatically, "You need to shorten that harness!" He replied sheepishly, "Yeah, I know now." I had a good time discussing possibilities and some sim parameters he could try to keep the "rocket alive" for future use. He appreciated that. He admitted he was "blindly" enamored with a sim and realized he was lucky to get a flyable rocket back to fly after a first time flight. Time is variable for a deployment system to deploy people!

 

[bad_idea]

I nearly always set the JLCR to 300', albeit it in fairly small rockets with parachutes 36" and smaller. I've set it to 200' a few times when the wind was high. That gets exciting but has still been successful.

 

[Upsrocketman]

If I don't buy a new case, it's either CTI 38 mm or single use.

Are you going ro Ldrs? If so you are welcome to borrow my 38-720 case.

 

[jqavins]

Yes, I'll doing this at LDRS.

300 feet is what one flyer after another that I've observed uses, successfully time after time. That's the only reason I have for picking it, and I will certainly take all your comments into consideration.

As for keeping it in sight and also having the GPS tracker, I want to see the whole flight, but I'm also sick and tired of losing rockets in tall grass and the like even when I watched them all the way down. I decided some time ago that I'm just not flying any motor bigger than an E12 without a damn tracker.

 

[Banzai88]

So the Inverse Tracker Principle will immediately and forever be invoked.

"If you can fly with a tracker, you should fly with a tracker...and the rocket will often land in a close and/or easily recoverable location.

IF you don't fly with a tracker when you could have, even low and slow.....prepare to lose even the largest of rockets!"

 

[Art Upton]

So the Inverse Tracker Principle will immediately and forever be invoked.

"If you can fly with a tracker, you should fly with a tracker...and the rocket will often land in a close and/or easily recoverable location.

IF you don't fly with a tracker when you could have, even low and slow.....prepare to lose even the largest of rockets!"

I agree with that, but there is also this issue if I did not mention it before.

With a GPS or RDF tracker, you can know exactly where your rocket is, but not be able to get to it*

* Treed for example, or Treed in a Bog/Swamp.

 

[cerving]

I agree with that, but there is also this issue if I did not mention it before.

With a GPS or RDF tracker, you can know exactly where your rocket is, but not be able to get to it*

* Treed for example, or Treed in a Bog/Swamp.

Yeah, I tracked one to a great big gravel pit... not getting that one back.

 

[Lord Rory Gin]

Try deploying the main up higher. Shoot you're using a GPS tracker to find the thing. Trying to purposely recover it in sight is insane. If trying to recover in sight, no need for a GPS tracker with the lower impulse motor!!!!! I usually use 1000 to 750ft main deploys at venues that allow it. I'd rather lope to an intact rocket than walk to a close "slam dunk" to pick up the pieces with a too low or too small main chute. Especially on a CERT flight!!
Sure if you're doing multiple test flights to see if the JLCR has time to get the harness and chute fully deployed before touchdown on the cert flight o.k.
But crack a fin or break something and your sponsor's may refuse to sign. Cert flights are not the time to try and do heart stopping recoveries. Save that for when the "cert" is in the bag and the launch is sparsely attended for flights thereafter.
I saw many a JLCR certification flights fail because the flier chose something like a 300 foot main deployment and the rocket slammed into mother
earth as the deployment harness failed to fully deploy. The larger the mass of the rocket and deployment devices become, the worse the problem will be along with the need for higher main deployment altitude. Kurt

Sorry, I have to disagree with your logic here. If using a JLCR and its is going to fail to operate, it doesn't matter one iota if it fails at 300' or 1000'. If it fails, the speed and force of impact on the ground will be the same. Changing the opening height isn't going to change the failure rate of the mechanism. The only difference is your "heart stopping" wait for opening.

It takes about 50'-100' for a chute to open. All you really need is for the chute to open and slow the rocket to a safe landing speed. Some might say even opening at 200' is going to work. I've previously set it to 400' and 500'. I think I shall continue to use the 400' mark for deployment instead of 500' especially in breezy conditions to minimize the walk.

 

[Art Upton]

Sorry, I have to disagree with your logic here. If using a JLCR and its is going to fail, it doesn't matter one iota if it fails at 300' or 1000'. If it fails, the speed and force of impact on the ground will be the same. Changing the opening height isn't going to change the failure rate of the mechanism. The only difference is your "heart stopping" wait for opening.

It takes about 50'-100' for a chute to open. All you really need is for the chute to open and slow the rocket to a safe landing speed. Some might say even opening at 200' is going to work. I've previously set it to 400' and 500'. I think I shall continue to use the 400' mark for deployment instead of 500' especially in breezy conditions to minimize the walk.

I will say that 400 is not a bad setting. But I've had and seen a few close calls at 300; Dual Deploy Chute Cannons or JLRC. [more DD than JLCR fyi]

How many here have seen a Pop at the Top rocket not get the chute to catch air, only to finally open just in time.