Level-3 high-performance design and build thread

So the L3 flight may happen this month? That'd be very cool!

That case needs a couple miles on it; I think my flight only frustrated it.

-Kevin

Your case will still be frustrated, I'm afraid, but the closures could be happy. The flight this weekend will be with a 4-grain L. The goals of this are:

1. Get some experience with 3" rockets in general
2. Fly something more fun than my 38mm 2-stage this weekend
3. Build some of the L3 components (chute, chute holder)
4. Make my TAP more confident that I'm ready for my L3 build
5. Set a Tripoli L single-motor altitude record

The sims say 33kft, or at least they did before I had any weighed components.

You think you could set a L record in a 3" rocket. Seems like a 54mm L935 Imax would be better record holder.

Bryce

bandman444 said:

You think you could set a L record in a 3" rocket. Seems like a 54mm L935 Imax would be better record holder.

Bryce

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If I can fly it successfully and submit my record application, then yes, I'll automatically qualify for a record, since that impulse category is currently blank due to the new record rules. An L935, may do better, but maybe not since it only has about 60% of the total impulse of the L1115 I'm planning to fly. I haven't simmed it, so I'm only guessing. At any rate, I'm about to have a 3" rocket to fly it in, and RASAero, which I trust, predicts that this one would beat the old archived record as well, which was 31316 on an Ellis L330. So I'll give it a shot and we'll see how well it does. Anything better than catastrophic should beat my personal best of 25k, which is another goal I forgot to mention above.

Adrian A said:

Your case will still be frustrated, I'm afraid, but the closures could be happy.

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It'll get over it.

The flight this weekend will be with a 4-grain L.

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I have that case, too. But no time to get it to you; my guess is you can find one out your way to lay your hands on.

The sims say 33kft, or at least they did before I had any weighed components.

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Only 4K over twice what I flew an M to this past weekend.

Should be cool!

-Kevin

troj said:

It'll get over it.

I have that case, too. But no time to get it to you; my guess is you can find one out your way to lay your hands on.

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Yes. Mike Shinn, aka Mr Helpful, is going to let me use his case.

troj said:

Only 4K over twice what I flew an M to this past weekend.

Should be cool!

-Kevin

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I just put a little more realism into the sims, accounting for a somewhat longer nose tube to accommodate my longer electronics bay. RASAero predicts 33066, and Rocksim predicts 22359.

Adrian A said:

I just put a little more realism into the sims, accounting for a somewhat longer nose tube to accomodate my longer electronics bay. RASAero predicts 33066, and Rocksim predicts 22359.

Click to expand...

The sims for my 3" rocket at Balls this past weekend were 21K in Rocksim and 31k in RASAero. I hit 29k even after the Mach 2.7 flight made carbon fiber tassels on the ends of my fins.

James

PS- I used the magentic arm switch on this flight, pretty slick Adrian.

Burner said:

The sims for my 3" rocket at Balls this past weekend were 21K in Rocksim and 31k in RASAero. I hit 29k even after the Mach 2.7 flight made carbon fiber tassels on the ends of my fins.

James

PS- I used the magentic arm switch on this flight, pretty slick Adrian.

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I'm glad you like your mag switch.

Thanks for the good data point on the altitude predictions. I bet you were using a Von Karman cone, too. Rocksim should really fix its drag model for that.

I'm very interested to see how the fins fare this time. The layup this time is better than what I had on my 38mm Mach 2.5 flight, but I'm just using Aeropoxy rather than the Cotronics resin. After I get the final layer of finishing on, I'll do a post-cure bakeout at 200 or 220 for an hour or so.

Kevin,

I hate to break it to you like this, but... Your forward closure has been assimilated.



It turns out resistance was futile.

This rocket design might make a good kit... but the av-bay would need to be a hell of a lot simpler. Cramming a Beeline GPS, a Raven, 3 batteries, a Telemetrum, 2 magnetic switches, and making it assemble-able without a soldering iron is not for the faint of heart. It just barely fits... I think. I still need to solder 2 wires to the battery terminals and I need to do some probing and poking to make sure nothing will get fried when I connect the power.

:y:

you could seriously market that as a package!

the most densely packed object rocket money can buy!!!

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would be a great way to market it

can't wait to see the full setup.

hows the nosecone design coming along? have you created a casting mold yet?

The whole set of innards under the nosecone, minus the charges and the protective front cap, weighs 658 grams. It breaks down as follows:

40' of shock cord 81 grams
Chute: 79 grams
piston: 36 grams
avionics core: 137 grams
central bolt and washer: 62 grams
Avionics bomb shelter and chute cannon: 266 grams

Looks good, Adrian!

And that forward closure needed to have its attitude adjusted, anyway.

-Kevin

edwinshap1 said:

:y:

you could seriously market that as a package!
would be a great way to market it

can't wait to see the full setup.

hows the nosecone design coming along? have you created a casting mold yet?

Click to expand...

For this weekend's flight, I'm going to use the Shockwave fiberglass cone as-is, glued to a forward section of airframe. I'm expecting a little under Mach 2.5 so I'm not too worried about heating.

Absolutely loving this thread!! Good luck with the flights Adrian, it looks incredible!

Patrick T

Won't you eventually need redundant altimeters for the L3 flight?

COrocket said:

Won't you eventually need redundant altimeters for the L3 flight?

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Raven + Telemetrum = redundant:wink:

new2hpr said:

Raven + Telemetrum = redundant:wink:

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Indeed. However, I'm not using the Telemetrum for deployments on this L2 flight, just the Raven. By next fall I hope to have my own version of a GPS tracking altimeter that could allow the av-bay to be a bit shorter. I should be able to easily fit 2 copies in there with batteries for the L3 cert.

Since it's there, why not go ahead and use it?

Personal preference thing. I have 100% confidence in my Raven and less than 100% that I won't screw up the connections or something to the TM and wind up with a premature deployment.

Adrian Wow I'm really impressed with how got everything to fit into such a small space! Good luck with your flight this weekend.

Adrian A said:

By next fall I hope to have my own version of a GPS tracking altimeter.....

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Looking forward to it. :smile:
Randall

I've been busy today. Let's see, I ...

Potted the shear pin/vent ring onto the av-bay tube
Glued on the nosecone tube
Cut the nosecone tube to length
Drilled holes for shear pins, altimeter venting and nosecone venting
Filled the nosecone joint
Sanded and filled the fins
And most recently, I made the chute protector cap. This goes on the end of the main chute tube to protect the chute from the apogee charge:

The tube sampler pack had a 1/4" OD FG tube that was just the right size to shove the harness through to form a seal against the deployment charge, and to fit into 1/4" holes from the mandrel of the hole saws I use. The harness will be folded around the outside of the tube, go into the chute compartment, go through a piston attachment, and then end at the chute. So there has to be transition somewhere from the outside where the charge is, to the protected inside. In the past I have epoxied the cord into place on the charge holder, but the transition from epoxy to no epoxy on the shock cord can be pretty weak. We'll see how this goes.

I also used another tube from the sampler pack for a charge holder. Normally I pot my charges into a cardboard tube, but Jim Jarvis's results of his vacuum charge testing have convinced me that a narrow, rigid container is probably a good idea for high-altitude deployments. Both the harness tunnel and the charge holder will see a lot of stress during deployments, so I added many layers of thin FG cloth to attach them to each other and to the top of the chute protector cap:

Isn't Bdale one of your locals? If so, might it be worth having him do a once-over to make sure you've got the Telemetrum hooked up properly?

That would allow you the benefit of a backup set of charges, just in case something goes awry with the Raven.

-Kevin (who likes to fly two alts whenever possible, just in case....)

Last night I couldnt find my shear pin screws so today I went to the local hobby store looking for some. I didn't find any there, but I did pick up some 1/16 square bass wood rod. I tried it twice tonight using spare airframe and coupler material. I pushed the coupler into the airframe on top of a bathroom scale. I used 4 shear wooden pins and the broke cleanly right at 105 lbs each time. That's about the holding force I'm looking for, though I'm a little worried about how much of a charge that will require. I'll find out tomorrow. I actually like the idea of wooden shear pins better than nylon, because the nylon strength varies with temperature so dramatically, and these will get quite hot from aero heating.

I test fit the cone tonight with all the harness installed, and found that I will need to wrap it and tape it carefully to get a clean fit of the cone. And no cord within the last 2" of the end of the chute holder.

Tomorrow morning I will ground test for charge sizing and put in any finishing touches. Then pack up and head out into the rain, which is supposed to last all day and into tomorrow night. I'm hoping to launch Sunday, when it's supposed to clear up.

I finally got to the ground tests, and they worked great on the first try. for the apogee charge, I put 0.8 grams of powder in the charge holder in the main chute cap, and I decided to use 3 shear pins:

[YOUTUBE]QtZ_n6YLeXI[/YOUTUBE]

I think I'll go up to about 0.9 grams for the flight. For the main charge I used a 0.3 gram charge. The video looks kind of funky because I used scraps from my main chute construction that weren't tied to anything, in case the rather loose piston suffered blow-by.

[YOUTUBE]ZvArlXVj88s[/YOUTUBE]

I would reduce the charge somewhat, but this will work fine and I already have more of this size made. If the apogee charge doesn't get the cone all the way off, a larger charge on the main chute should complete the job.

Here are a bunch of of other photos documenting the build:





After doing the above, and anticipating needing to do it several times as I fine-tune the charge sizing, I decided to make a little fixture to speed things along:



With the finally-complete electronics core inside the av-bunker (It fits!):



Prepping the deployment test wiring:
https://i281.photobucket.com/albums/kk205/adamsona/Level%203
/IMG_3089.jpg



The sun came out just in time for the deployment test, and the optical illusion shot of the fins, which look horribly un-smooth due to in-plane waviness of the uni carbon fibers (They're actually smooth and flat):



This is after baking the fin can in my kitchen oven for a couple of hours at 210F. I'll be interested to see how they fare at Mach 2.5 or so tomorrow.

Now for the avionics core:

Raven, Raven battery, magnetic switch and Beeline GPS antenna on the left.

Beeline GPS board on the left

2 parallel 350 mAhr cells for the radio battery

Telemetrum and magnetic switch on the left.

Looks like the batteries have recharged now, so it's time to get back to prepping for tomorrow. I hope to get the av-bay assembled with shock cords in place, and then just bolt it down and load the main chute once I borrow the 4-grain case.

Looks awesome, Adrian. Best of luck on your flight!

Thanks, Mike.

The total weight, minus the motor, is 2076 grams, 4.6 lbs. The airframe by itself is right at 3 lbs, and the innards add the rest. It came out a bit heavier than I was expecting or wanted for this flight. But it's still going to do well, I think. The stability margin is a little over 6" on a 46" rocket, so it should be a straight flight. Except for that imperfect fin, which may cause some coning.

RASAero is predicting 31,800 feet, assuming 6 mph cross wind and 50 F launch temperature, the expected conditions around noon tomorrow. Now to pack up.

Adrian A said:

...I decided to make a little fixture to speed things along:

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Great idea. That is one of those tasks that needs four hands to accomplish. The jig makes it simple with repeatable results. Well done.

Best wishes & good luck on this flight. Looking forward to great report on a successful flight.

May your rocket see Black Sky!

Jim :dark:

100% successful flight today. Raven says 31,514. Telemetrum says somewhat higher. I haven't tried downloading the beeline GPS yet. Perfect recovery 2 mi north of the pad.

Yay!:marshmallow:

Adrian A said:

100% successful flight today. Raven says 31,514. Telemetrum says somewhat higher. I haven't tried downloading the beeline GPS yet. Perfect recovery 2 mi north of the pad.

Yay!:marshmallow:

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:clap:

Excellent! Congrats, Adrian!

Looking forward to that next flight.

-Kevin