Taking a shot at the G record

Adrian A

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I got my G12 motors a couple of weeks ago, and Northern Colorado Rocketry is finally going to get to launch this weekend (albeit at the Atlas site with a 12k waiver), and I have a new and improved tower, so let's make a record attempt rocket!
I have a mandrel for a nice skinny Von Karman nosecone, and a very worn-out silicone mold, but I'm going to take the easy way out for now and just use the Apogee 29mm plastic cone. If the altitude is disappointing I'll invest the time to work on a the VK. I think I'll want it for the H record attempt because of its faster max speed.

For tubes, the Apogee 29mm cardboard tube isn't a bad choice. After all, it appears to have been used for the H record recently. It weighs almost exactly 1 gram per inch in length. Today I made my own thin-wall carbon tube so that I could integrate a little boat tail, and sand it down smooth. I'm also curious how the mass compares. For the mandrel, I'm using a CTI 6-grain case with a tapered rear closure, covered with mylar:
IMG_0204.jpg
This time I remembered I needed to tape the mylar together with the sticky side out. For the tapered rear closure, I used some separate flash-breaking tape and a bunch of grease between the closure and the motor case. I taped the mylar down at the other end to make sure I didn't get any epoxy underneath it.

Next, a simple single-layer braided sleeve. I taped it down at the forward end, which I will discard. Taping it down helps to stretch it lengthwise to take out the slack. The +/- 45 degree fiber orientation is far from ideal, but in this application we're talking about a cardboard replacement where it's not going to be stressed much at all. It just needs to be light and smooth.
IMG_0205.jpg

After the shrink tube:
IMG_0206.jpg

I used Soller 1.25" light carbon sleeve, and one of their shrink tubes, which did a pretty nice job on this tube. I taped it on the front end and found that it helped to keep some tension on it while I used a hot air gun to shrink down the tube, which went down smooth and pushed the epoxy along the length of the tube as I went. But every layup has to have some moment of desperation. In this case I let the excess epoxy pool up at the back and, and then when I tilted the tube the other way, the epoxy ran down inside the motor case that I'd like to use again. I washed it out with some acetone and a bottle brush while the wet layup was still going on the outside.

I the tube into the oven at 125F, went out to put up Christmas lights, and came back in to a finished tube that came off the mandrel pretty easily. After I pulled out the mylar, the tube came out to 12.8 grams for about 12" of length. So no mass savings over the cardboard tube, but the boat tail is already taken care of.

Packing in the electronics is where things will get interesting, but that's for tomorrow. I'll be using a Featherweight GPS Tracker and a Blue Raven prototype altimeter.
 

Adrian A

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After sleeping on this, I decided I can’t justify the time to get this rocket done this week, considering the software I need to get done for the Blue Raven. The next nearby launch for me with a high enough waiver for the G record will be February. This Saturday I’ll fly my 29mm testbench rocket to get some more Blue Raven flight test data.
 

Adrian A

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Why do you think you need a waiver for this record attempt?
Good point. The maximum propellant weight for an FAA model rocket flight is 125 g, and this has 80-something, so in theory I could exceed the high power altitude waiver at an event with this rocket without violating the FAA regulations. If the prefect and LCO are o.k. with that.
 

boatgeek

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I don't want to derail the thread, but I've always felt kind of squishy about exceeding the waiver altitude with a Class 1 rocket. Mainly it's that outside observers (if any) that saw the rocket go past the waiver altitude wouldn't know that particular rocket is Class 1. That might bring unwanted scrutiny on the waiver holder.
 

astronwolf

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Good point. The maximum propellant weight for an FAA model rocket flight is 125 g, and this has 80-something, so in theory I could exceed the high power altitude waiver at an event with this rocket without violating the FAA regulations. If the prefect and LCO are o.k. with that.

It's not just a theory. FACT - the FAA does not require a waiver for flying Class 1 rockets. There's not even a gray area in the regulations to get all "squishy" about. Go for the G record!
 

Adrian A

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It's not just a theory. FACT - the FAA does not require a waiver for flying Class 1 rockets. There's not even a gray area in the regulations to get all "squishy" about. Go for the G record!

Sure, but the FAA isn't the only stakeholder. The considerations like recovery area and surrounding landowner attitudes are site-specific. I'd like to end this side topic here if that's o.k.
 

bad_idea

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How are you dealing with the thrust ring of the G12? I believe it's the same one as the G8, which I've measured at 32.2mm in diameter.
 

David_Stack

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Curious whether you weighed the carbon sleeve prior to the ‘layup’, and then calculated what percentage of the finished weight was epoxy?
 

mbeels

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Looking great, this will be interesting. Do you have an optimum mass you're targeting? Or with that motor, is it just as light as you can?
 

Adrian A

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Curious whether you weighed the carbon sleeve prior to the ‘layup’, and then calculated what percentage of the finished weight was epoxy?
It was about 5.5 grams before epoxy, so the CF is a little under 50%. Less than ideal.
Looking great, this will be interesting. Do you have an optimum mass you're targeting? Or with that motor, is it just as light as you can?
It's as light as I can. I'm estimating about 65 grams without motor.
 

watheyak

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It's not just a theory. FACT - the FAA does not require a waiver for flying Class 1 rockets. There's not even a gray area in the regulations to get all "squishy" about. Go for the G record!

I hate to be "that guy" but...

The Prefect, LCO and the FAA would all have a problem with that. Once there's a waiver in place, you can't go arguing semantics.

This horse has been beaten before.

My advice to Adrian would be to take a road trip to Phoenix and fly it with TRAPHX. You'd have your pick of board member's guest rooms to stay in!
 

rockets

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Following! Looks like a fun project..

On a side note, how active are the clubs in CO during the winter months? Hoping to come out to a launch at some point, although my work schedule mostly limits my Saturdays
 

Adrian A

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Following! Looks like a fun project..

On a side note, how active are the clubs in CO during the winter months? Hoping to come out to a launch at some point, although my work schedule mostly limits my Saturdays
Here's the Tripoli All-Colorado launch schedule calendar.

SCORE is in Pueblo (5400 feet, 8k waiver). NCR is in Northern (12k waiver) or Very Northern (5500 feet altitude, 20kft standing waiver plus call-ins) Colorado plains, Tripoli Colorado is in Hartsel (a very cool launch site at 88000 feet, 7k waiver with call-ins to 14kft), San Luis Valley Rocketeers is near Alamosa
 

Adrian A

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What do you envision for fin stock? Carbon plate, fiberglass? Vacuum-bagged carbon over airfoiled rohacell cores? :cool:
I make my own carbon plate stock from unidirectional fibers. It's so easy and inexpensive that I'm sad whenever I see 1/8" thick fiberglass used for fin cores. I just sandwich the wet uni material (from Soller) between 2 granite floor tiles from Home Depot. Sometimes I vacuum bag the sandwich but it also works to just clamp it. The fins on my L3L rocket (went over 32,000 feet on an L) with a 4" span are about 0.090" thick after the tip-to-tip layup, and I can confidently stand on the rocket supported by the fins. This rocket's fins will probably be around 40 mils thick.
 

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I have been making my fin material for some time using E-glass fabric. It works well and is inexpensive, I do put it between 2 mylar sheets and always vacuum it. Would it be possible to get more specifics on yours? Which Soller Uni, how many layers and orientation of layers? Thanks, George T
 

Adrian A

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flyguy614

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What altitude are you getting in simulations so far? Gotta know what I'm going to have to beat next year 😉
 
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