I am going to cert L1; need mentor/witness

[Geof Givens]

The 29/240 fits in the motor tube which I designed for 29/60-120, but sticks up beyond. The nose is mostly full of weight. Aside from a bit of empty space around the motor casing and around the nose weight, this leaves 4 inches of vertical space @ approx 4in diameter, which is absolutely 100% filled with recovery gear.

Using EMRR’s calculator, 4×4 => 0.26g for 10psi, 0.51g for 20psi

That’s reassuring. As mentioned above, the worry is that the nose cone has greater mass than the rocket. I suppose Newton’s 3rd law implies that that doesn’t matter.

[Bruce R. Schaefer]

I suppose Newton’s 3rd law implies that that doesn’t matter.

Regarding Newton, there is one famous and infamous expresision that we’ve all heard and used, “Well, in theory, it should have worked.” Let me say something about Ken before I go on, he nailed his L1 and L2 with perfect flights, first time on both. And, I’m sure when the time comes, he’ll do it with his L3. I, or anyone who certs you–Ken’s a good choice, too, BTW–will have to see your rocket in person. Did you ground test in anyway? Because of your unique and really cool design, that is advisable. Though you couldn’t do it without a motor casing and separate charge canister. I can bring the stuff you need except for the motor casing to OF, just let me know. Don’t trust a heavy nose to keep it on. In fact, and this goes along with Newton, if the nosecone is the heaviest part of your rocket, it will move away from the booster due to momentum and the fin drag of the booster. The pressure change is due not only to altitude, but a sudden change in pressure. And, it’s more than you really think. Plus a loose fit causes gas from the ejection charge to escape without doing its job, i.e. a pressure leak. Not good. I’ve shot nosecones off twice and stuck the chute with a charge, not lack of vent holes–don’t be conservative with ejection charges. I can’t imagine anyone who would certify a rocket with a nosecone too loose and not able to stand up to being held by the nosecone without separation. There are exceptions but few. All certs are heads up. But be sure you tell all this to whomever is going to certify you, so he can make sure it’s pointed away from the crowded areas. Then again, Geof, all your opinions and calculations may be right for this particular rocket. You are ultimately responsible for the rocket’s flight and safety. Only takes one successful flight to certifying at any level. However, what’s been mentioned by Ken and me will have to be followed at some point for you to grow and get higher power. I also saw your glider(s), and they were fantastic! You have the skill you need, just listen to what others have to say and look at their rockets. Ken and I are only two people, and there are a lot more with great advice.

[Geof Givens]

In fact, and this goes along with Newton, if the nosecone is the heaviest part of your rocket, it will move away from the booster due to momentum and the fin drag of the booster.

Plus a loose fit causes gas from the ejection charge to escape without doing its job, i.e. a pressure leak.

These are good points. Okay, I’ll tape the shoulder a bit for a more snug fit.

–don’t be conservative with ejection charges.

The ejection charge is 5x the level recommended by the calculator (see a previous post).

[Bruce R. Schaefer]

The ejection charge is 5x the level recommended by the calculator (see a previous post).

I’m sure you’re right. If you have such a small area to pressurize, 1/2 gram or less. Your call. Since you’re going to fly the rocket with a G or two, find out what the ejection charge is in the G’s you’ll be using. If they work, that’s the charge you need.

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