Both events looked fine to me. You want the main out with authority. Kurt
Bay Area Rocketry should be one of the vendors at LDRS, and Mike (owner) has a good selection of TFR chutes. Below a certain diameter (≤18"?) everything he has is thin mill I believe.
On my Go Devil 38 I use a Dog House small charge well on each end, each one holds ~0.6g along with the Firewire initiator, and I've always just filled them. Has worked fine, though I was only friction-fitting the nose and finding that sometimes the main would come out at apogee, other times during descent but before the altitude set in the altimeter. I have about 15' of shock cord in each bay. So I've drilled holes for shear pins for the nose and will be using them moving forward, I've never done any ground testing with this rocket as I couldn't fit my TRS in the bay, now that I have a Quantum I really should do a test just to see if I should perhaps go down a bit on the charges.
Nice set-up Will. You didn't mention shear pins so I take it you friction fit everything?
Will,
Do you think I need vent holes in my sustainer and forward section even though I use shear pins? I don't want the pressure in my bays popping my shear pins before the altimeter wants to do it.
I re-did my main compartment test. I tried 0.5 gm and it did not open. I tried 0.64 gm and it opened. The blue tape on the shock cord worked to reduce the shock from the deployment. I was happy with that. When I opened the chute however I found opposing gores of the chute were melted together. That chute would never have opened.
One new thing I tried today, I had my 12 inch chute protector cut down and made into four 6 inch chute protectors. I figured since I could not get my chute in with the full 12 inches of protector maybe I could with 6 inches. It sure would beat leaving the chute protector out and trying to use blue recovery wadding paper. I had at least three attempts with the blue paper and two more with the 6 in chute protector. Maybe the chute melted in one of the previous attempts.
Here is the test. I initially jumped to a conclusion that this latest test melted the chute. It could have been the previous attempts,
<https://www.youtube.com/watch?v=mM6ILRU-SQ4&feature=youtu.be>
Now I have to do it again and see if it melts together again. I have 20 e-matches I bought from Crazy Jim (thanks for that). I will try his method of using the tips of nitrile gloves to encapsulate the black powder. That seems shaky but this way I get to check it out on the ground instead of in the air. My biggest problem is that I am running out of time. I have full weekends and my work is going to demand overtime. I have products I must get out by June 7 or I must go late to LDRS. That would be a disaster!
I could be wrong, but pins _and_ venting not either/or. No vents makes sad barometers ( although accel only, timers, etc )
For a almost identical size rocket, I use .5 apogee [20ft of 1/8 kevlar] & .7 main. [15ft of same kevlar]
NC is held on with 1 2-256 shear-pin & fit is rather snug.
PS: since there is only 1 altimeter, I use 2 matches per charge.
It takes on average 50 lb(f) to shear (2) 2-56 nylon shear screws. The cross-section of the airframe is 1.77 sq.in. That means an average of 50 lb/1.77sq.in.=29 psi. To insure the screws shear you want at least 25% more or ~>=35 psi.Gents,
I am at that stage. How much BP for the two charges? It is a 38mm. The available volume in the sustainer is 5.5 inches long. There is a 15 ft shock cord and a 12 in chute.
In the forward body it is 6.7 inches. There is a 10 ft shock cord and a 30 in chute.
The formula in Modern High Powered Rocketry 2 says:
BP (grams) = 0.006*D_compartment^2*L_Compartment
That comes out to 0.074 g for the sustainer and 0.090 grams for the forward compartment.
Does that sound right to you?
I will begin testing tomorrow.
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