Honest John L900DM

I recently had an issue with no apogee separation on my Honest John. Same set up it has flown many times is on various M motors. I finally pulled the data off the MAWD. The other altimeter was a Missile works. Looks very strange. What are your thoughts?

Looks like there was a whole lot of shaking at apogee. Was the charge too small or the coupler too tight?

Kevin

Went together fine. Same configuration I have always flown it in. Just a smaller motor. I had two people tell me they heard the apogee charges. Damage was mostly chutes that striped at the main event. Outside of that a couple of 5 inch zippers. Rocket is repaired except for paint and new vinyl from Sticker Shock .

Those two altitude spikes down were most likely due to the apogee charges going off. (also the one around the main chute deployment event).

You need more ejection charge (and better sealing for your altimeter bay perhaps).

Same amount of powder as always. That's what I don't understand. The rocket has had 6 textbook flights on it.

The apogee charges fired and you either had a jam or some way for the pressure to leak away. Open motor tube or hatch in the booster section? The downward spikes are from pressure leaking into the av-bay. My Goblin vents into the main body which then vents outside so the altimeter sees the apogee pressure spike. Perfectflite altimeters ignore events lasting under about 1/4 second.

That could be the charge canisters from Rocketry Warehouse. I have used them the last 3 flights. The e-match is ran through the bottom of them. I covered the bottom with aluminum tape and put their little black cap on them. They were off inside the AV bay but I was not sure if it was from the rough landing. I think I will need to rework them.

Just because it has worked in the past doesn't let you know how much MARGIN you had.

The biggest mistake people make when ground testing to just "test to pass" instead of preferably testing to fail. In other words know the powder level where is fails low (barely getting the nosecone off) and fail high (where the charge violently snaps the shock cord). Then you can set the charge level comfortably in the middle.

PS. I am guilty of not doing this as well.

On rockets that cost me more than $ 100 , I put 2 altimeters, for the backup charge I always go with more BP ( it usually fire when the rocket is open , but if the first one miss, this one will open it for sure ))

My original post shows two altimeters . A MAWD and a Perfect Flight. The apogee charges were heard. Both apogee charges were 6 grams.

Brent said:

My original post shows two altimeters . A MAWD and a Perfect Flight. The apogee charges were heard. Both apogee charges were 6 grams.

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I don't like the design of the Rocketry Warehouse charge canisters. The charge canister pressurizes upon ignition of the BP, and therefore it's expected that the wire holes need to seal the internals of the bay from the direct expansion of the gases.

You said that they were broken off? Assuming that the charges damaged the canisters (6g is a lot of pressure!), two large holes in your e-bay may have been enough to dissipate the pressure out of your drogue bay. What were the dimensions of your drogue bay, and approximately how full is it with the cord/drogue? My impression is that it's not that full, and a relatively large bay. Is this a 6" or 7.5" rocket?

Pictures of the end result would be beneficial for us to help you with a post mortem.

Not broke off, the black plastic caps that are inside the bay on the charge canisters were off. This has not happened before, maybe I was lucky before. I usually go drogueless so about 16" of 7.5" tube with 30ft of recovery harness. I am leaning toward pressure going back into the AV bay from the back of the charge canisters. I am in the process of tapping the e match hole and putting a screw in the to defiantly seal them off. Didn't take any pictures, the damage was remarkably not all that bad. Mostly chutes and a couple of zippers about 5 inches long. One the booster and one the payload. The rocket is fixed just need paint and new vinyl.

Brent said:

That could be the charge canisters from Rocketry Warehouse. I have used them the last 3 flights. The e-match is ran through the bottom of them. I covered the bottom with aluminum tape and put their little black cap on them. They were off inside the AV bay but I was not sure if it was from the rough landing. I think I will need to rework them.

Click to expand...

I think the aluminum tape leave far too much room for leakage as evidenced by your plot. I would consider using silicon RTV instead...you need to leave it setup a bit after running the e-match through it, but getting a good seal should be easy. Also, you could consider, although more time consuming, potting the ematch in the holder with some 5 minute epoxy. Sure, you need to drill out the hole, but it should be sealed.

RTV would work if you pot the leads from inside of the charge well, not on the inside of the bay. Then you'd be utilizing the physical strength of the seal vs the bond of the material to the aluminum.

You could do both, but I agree with you. I do it this way.