Sub-Min Contrail L800 Build

G_T said:

IIRC, the rule of thumb is about 30G. So if your forward section in front of the shear pins weighs 5 pounds, then you want it to shear out at not less than 150 pounds force.

In a high speed horizontal deployment, you'll still deploy the main in all likelyhood. But for most other scenarios, the front will stay attached upon drogue deployment.

Gerald

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Well the forward part probably doesn't weigh more than a pound so that means the 4x35lbf total of roughly 140lbf is more than enough in that department. But then that doesn't really count the drogue pull itself. I guess in a perfect world that should be about zero unless something screwed up so I shouldn't worry too much. Also, if the main goes at apogee I just have to walk farther so it isn't the end of the world. Does the charge sizing sound about right to you? I used the NASSA ejection charge calculator and that is what it gave me for the volume and pin number.

Those calculators will get you in ball park sometimes but I’d ground test just to be safe.

In my experience if the packing is very tight (which I personally like to do; I like no possibility of shifting mass) then you might need more charge then expected.

Gerald

ArchitectOfSeven said:

Well the forward part probably doesn't weigh more than a pound so that means the 4x35lbf total of roughly 140lbf is more than enough in that department. But then that doesn't really count the drogue pull itself. I guess in a perfect world that should be about zero unless something screwed up so I shouldn't worry too much. Also, if the main goes at apogee I just have to walk farther so it isn't the end of the world. Does the charge sizing sound about right to you? I used the NASSA ejection charge calculator and that is what it gave me for the volume and pin number.

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Keep in mind that the shear pins must withstand the force of not only the nosecone, but also the main parachute, harness, hardware, etc.
As Tim said, be sure you ground test. It’s important to ground test the configuration you intend to fly, so when you test the apogee charge(s) have drogue chute shear pins in place and the main, harness, and nosecone all in place and held by the main’s shear pins.

Well the quarter is finally finished and I have had a little more time to play around with things and try to make everything work right. Last week I got some recovery testing done and got a nice drogue deployment out of 0.8g(cutting 4 #2 nylon pins). It was a little lethargic popping off though so I'm going to test it at least one more time with 1-1.2g. I'm kinda worried that it won't clear properly if there is too much air pressure from high speed or whatever. The charge holders are small pvc pipe caps set down next to the u-bolts. Speaking of that, what do you guys use to retain and compress the powder? I had used a little piece of nitrile glove over a wad of paper towel pressed in really hard and taped down. It worked fine I guess but I'm worried about reliability and blowing out bits of flaming paper and/or plastic. Other than that I've stripped the nose cone and am preparing it for some bondo and sanding and am preparing to make a few more nozzle assemblies to bring it up to an M class motor. I'll post some pictures as I get some things done that I can be happy with. This is so much better now that I'm doing it for fun, not a class...

ArchitectOfSeven said:

I guess but I'm worried about reliability and blowing out bits of flaming paper and/or plastic

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If you are using paper wadding (that's what I use) you can use crepe paper party streamers. Buy them from a reputable supplier (not a Chinese discount shop) and it will have fire retardant in it. Useful at celebrations too

ArchitectOfSeven said:

Speaking of that, what do you guys use to retain and compress the powder?

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Dog barf (cellulose) & masking tape.

Are there any updates to post on this project?

DRAGON64 said:

Are there any updates to post on this project?

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Soon. Got stalled by school bureaucracy and am trying to figure out how to manufacture a graphite nozzle. Safety codes don't have any allowance for small amounts of graphite and another part of my rocketry club got caught making a nozzle so the hammer came down. I think I found someone with an available lathe so hopefully I'll get an update posted soon. Seriously I can't wait till I can buy my own machines and make what I want, when I want.

Just curious, have you emailed Tom?

[email protected]

ArchitectOfSeven said:

Soon. Got stalled by school bureaucracy and am trying to figure out how to manufacture a graphite nozzle. Safety codes don't have any allowance for small amounts of graphite and another part of my rocketry club got caught making a nozzle so the hammer came down. I think I found someone with an available lathe so hopefully I'll get an update posted soon. Seriously I can't wait till I can buy my own machines and make what I want, when I want.

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Yeah they generally hate magnesium too on lathes. When you get your own someday or have the cash to call up a machine shop you’ll enjoy life more. My school had janitors clean up carbon fiber dust. We were all wearing respirators because they assigned us to an indoor room. Then we took our rocket stuff to a friend’s house because of osha crap. School was able to plasma cut one thing. Otherwise we had to contract machine work out due to no tool bits or odd sh^t behavior on school part.

I've not had any cleanup required machining graphite on a lathe, with a strong vacuum right at the cutter. YMMV. There is no way I'd machine graphite without the vauum though! Best is probably vauum through a water tank.

Gerald

Well I found a lathe and made the insert happen. It came out pretty good considering it's a 1905 lathe with worn out screws and not much in the way of indicators. It ran slow as well which meant no dust. Just a few operations to finish up at school in a few weeks and the motor will be ready for testing round 2.

That’s quite impressive. And almost weapons-grade. I’m surprised with all the paranoia that the FAA has about drones, that you could get away with flying that vehicle. It’s nice to have a lathe, that’s for sure. Keep us posted on your headway/testing.

slothead said:

That’s quite impressive. And almost weapons-grade. I’m surprised with all the paranoia that the FAA has about drones, that you could get away with flying that vehicle. It’s nice to have a lathe, that’s for sure. Keep us posted on your headway/testing.

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Why, it is just a rocket flying with a waiver? Drones could fairly readily be weaponized with a little creative thought. A rocket not so much.

Frankly, I am still surprised to see drones flying at rocket launches.

Flight training was always a pain when we’d call flight service station up with flight plans for Cessnas and they’d moan about UAV predator drones in X areas. We’d just avoid those areas, lol. Predators didn’t carry transponders making ATC life difficult to identify and the FAA just let it go. So the problem was knowing where the military drones were. I’d assume some were armed for overseas missions.

Making some progress on things but for the moment I'm trying to piece together my own fill system. For fill and dump I was looking at these solenoids bit am 100% open to alternatives if they are cheaper, better, or safer. Also, how far do I want the tank from the launch pad and does anyone have a sample schematic of what the system should look like?
https://www.summitracing.com/parts/wsn-372115

The system from Pratt Hobbies is probably the simplest way to go.

https://pratt-hobbies.com/proddetail.asp?prod=ULS-M2
Plus gauge upgrade.

We have been using this system for a couple of years now. It’s solid and reliable. We have been using our own fill/dump/launch control system, but there is an off the shelf system from Contrail https://www.contrailrockets.com/GSE.htm

ArchitectOfSeven said:

Making some progress on things but for the moment I'm trying to piece together my own fill system. For fill and dump I was looking at these solenoids bit am 100% open to alternatives if they are cheaper, better, or safer. Also, how far do I want the tank from the launch pad and does anyone have a sample schematic of what the system should look like?
https://www.summitracing.com/parts/wsn-372115

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12v automotive solenoids are not meant be used but for a few seconds at a time. I made (15 years ago) something called a solenoid saver. I did a quick look and could not find the one I made. Here is a link for one https://blackdogrocketry.com/wp-content/uploads/2013/04/SolSav1.pdf

borrowed from here https://blackdogrocketry.com/?page_id=7

A simple google search shows some possible ideas too. https://www.google.com/search?q=hyb...iYreAhXC5J8KHVYHBmMQ_AUIECgD&biw=1536&bih=775

Tony

Thank you for the help on the solenoids. Another minor update is the new nose cone mold is done printing and is currently getting sanded and smoothed. Let's hope having an actual shoulder helps prevent the wiggling issue from the previous version.

Great idea using the solenoid saver. The one mentioned is very old-school, but quite effective. If you are setting up an Arduino or something else to run your fill sequence or launch control you can use a PWM output to control the average voltage to the solenoid. Hit it hard first to pull it in, then back off the voltage to hold it without overheating it. If you don't have the coding skills and are not going Arduino or similar, the hardware version is perfectly acceptable. The only downsides are size, power dissipation (heat) and the fact you need to let the capacitor bleed after each actuation. In the case of the values listed there it would be around a second in the off position before switching it on again, which isn't too bad.

Minor progress update. Nose cone mold is complete and fiberglass is mostly done. I started with 3 inner layers of heavy fiberglass, lathed it back into round, sanded it smooth, and then applied another 3 layers of very fine cloth. Tomorrow I should be able to toss it back on the lathe to correct any thickness discrepancies, trim the ends, and then try and remove the mold. Overall it's looking really good and should come out pretty comparable to a commercially available cone. After that I have to make a new adapter for the shoulder, metal tip, and get back to ejection testing. Should also have a static fire coming up in a week or so. I'll post a video when I can.

Update time! The static fire attempt did not go exactly as planned so it got scrubbed. Next attempt will be next weekend I think if the stars align properly so fingers are crossed. Plumbing system is still under development phase and a control/ignition box is in the works as well. Most interesting thing is that Nose Cone Ver. 1.1 is nearing completion. The surface quality is still a bit low but that will be resolved with a few more rounds of filler and sanding. The aluminum point came out a lot better then I expected though so that is something to write home about.

Man that looks fantastic.

Cool build thanks for your purchase and good luck, if you need anything let me know.

The first motor I sold went to Florida and was then shipped to Anthony at Hypertek in Canada. He had the 98 mm M-1040 and I had released the 75 mm M-2281. I would not have found out but Canada customs held the ORMD package because of the Thermite ignition charge. I later re-certified all my Motors to ignite with customer provided Pyrodex pellets eliminating the ORMD and allowing international shipping.

Is that a 3 inch OD not 75 mm tube?
University of Mississippi is using 4 CNVA in the injector baffle producing 4 Vortex’s with a rotation of 1200 rpm each increasing performance by almost 50%. My new Wax and Black Smoke fuel is another way the Universe of Tennessee is boosting performance both of these projects were done as a collaboration with the students trying to make my Motors better.
Tom Sanders
Contrail Rockets
928-208-5580

ContrailRockets said:

Cool build thanks for your purchase and good luck, if you need anything let me know.

The first motor I sold went to Florida and was then shipped to Anthony at Hypertek in Canada. He had the 98 mm M-1040 and I had released the 75 mm M-2281. I would not have found out but Canada customs held the ORMD package because of the Thermite ignition charge. I later re-certified all my Motors to ignite with customer provided Pyrodex pellets eliminating the ORMD and allowing international shipping.

Is that a 3 inch OD not 75 mm tube?
University of Mississippi is using 4 CNVA in the injector baffle producing 4 Vortex’s with a rotation of 1200 rpm each increasing performance by almost 50%. My new Wax and Black Smoke fuel is another way the Universe of Tennessee is boosting performance both of these projects were done as a collaboration with the students trying to make my Motors better.
Tom Sanders
Contrail Rockets
928-208-5580

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Not 100% sure this message was meant for me but I'll respond to what I can. Yes I did use 3" OD tubing because of availability. What is 4 CNVA? Also what is this new fuel you mentioned and how do I get it?