I flew my Warlock for the first time today using a CTI I218. I used the Thrustcurve-suggested delay of 6s using the CTI drill (removed 8s from the 14s base delay). I was kind of alarmed that the rocket started coming down ballistic for maybe 200-300 feet before the chute deployed. Everything went fine after that and it didn't zipper, but I'm curious why the delay seemed too long.
1) Manufacturing issue with the CTI drill? The point of the drill is about 1/4" below the edge of the plastic housing...can anyone verify that's correct?
2) Random weirdness with the rate of burn on the delay?
3) Does the Warlock's stubby profile throw a monkey wrench in the Thrustcurve delay suggestion?
4) I kind of thought the nose cone was a little snug...is it possible for a snug nose cone to delay deployment rather than completely prevent it? Like the pressure pushes it out slowly rather than just popping it out?
My OR sim for my Warlock on an I218 says the optimum delay is 7.6 seconds, and the delay estimates have been pretty accurate in the past for this rocket. So, if anything, it sounds like the Thrustcureve estimate of the delay should be short, not long.
My guess is that the delay went long, not that the sims were too long. Either the grain burned slowly, or the delay was not drilled accurately.
On my 54mm DAT, I think the drill bit is recessed even further than 1/4”. Let me know it you want me to measure it. It varies with the delay setting, so maybe you can post your own measurement from the tip of the drill to the lip of the plastic when the drill is set to -8 seconds. I actually haven’t used my new 54mm DAT yet. I just built my first rocket with a 54mm mount, and the shakedown flight was on a smaller diameter motor, so I’ve only used the DAT made for 29mm and 38mm motors.
Is it possible you made a mistake and set the drill to 6 instead of 8? I almost did it once — nearly set the drill for what I wanted the delay to be, not what I wanted to remove.
One one thing I usually do when drilling delays is to rotate the drill until I think I’ve reached the right depth, then remove the drill, shake off the excess shavings, put the drill back into the delay grain, and give it a few more twists to be sure the hole is clean and that it’s drilled to the full depth.
Your question about the nosecone is probably not the problem. The ejection charge pressure does not slowly force the cone out. One thing that could have happened is that the ejection charge did not fully blow the cone out, but blew it out enough that it did fall out a few seconds later. Are you supplementing the black powder charge? The Warlock has a lot of volume to pressurize, so you need more than the standard charge. I use a total of about 3 grams. The 38 and 29mm motors have a standard charge of about 1.5 grams, and I add another 1.5 grams to that.
If you are flying the rocket over 2,000 feet, you should drill a few 1/8” holes into the airframe to vent out extra pressure that can force the cone out as the rocket gains altitude. You don’t want an early deployment either — just as bad as late! The holes will relieve pressure, but will not affect the ejection charge pressure.
Hopefully, you you can get the delay problem figured out. It was probably a fluke. You might want to fly an altimeter to get good data on when the events are actually happening. And watch the action at apogee with binoculars. If you are still not sure about the accuracy, you could use a chute release. That way, if the ejection charge happens while the rocket is moving fast, popping the nose cone will slow it down, and the chute release will deploy the chute at a safer speed. A small drogue might help too, but it’s probably not necessary.
I see you are planning to use the Warlock for an L2 attempt, which I think is a great idea! I got my L2 last week with a Warlock. I’ve had fin damage in the past when using the stock parachute, so I used an oversized chute to bring it down gently, and used a chute release to avoid too much drift on the big chute. I set the chute release to 700’, so the rocket fell with the NC out from 2,100’ to 700’, which is a long, unnerving time to watch it fall, but the chute deployed fine, and the rocket landed gently nearby. Worked great!
