Joharvey1
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- Joined
- Mar 8, 2021
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So I had a puzzling result at the range this past weekend, and after consulting with several experienced rocketeers, I am still at a bit of a loss as to what may have cause this issue. It was suggested I post the results here to see if the forum had any more ideas.
Lets start at the beginning. I purchased secondhand a PML Endeavour, which I repainted and added a third rail guide to, along with an Aeropak retainer and Aeropak Adapter down to 38mm from 54mm. Now, other than that, the rocket is as it was when I purchased it. No additional nose weight or significant modications have been done under my ownership.
Now, as I looked at the rocket prior to launch in Open Rocket, it simmed to around 3412 grams or approximately 7.522 lbs.
Individual component weights were: Nosecone (325 grams), Payload (881 grams), and Fin Can (2206 grams.) At this point, the rocket had a stability in Open Rocket of 2.93 calibers.
It was noted prior to launch that any motor below a J460T would result in a caliber rating above 2.0 calibers. A J420R registered about 2.1 calibers. Ultimately however, I was advised that certain motors can straighten out a rocket path well enough off the pad as long as the thrust to weight is something above 7:1. Closer to 10:1 was best as I was told. Taking this information with the goal of a lower altitude flight, ultimately we settled on an I500 single use. Which, as I was told, would "straighten anything out off the pad," and that stability really shouldn't matter much except when the rocket was "higher up" in this case.
I should also note there was very little wind that day, if any.
When the rocket came off the pad however, it almost immediately pitched several degrees north and altered the flight path. It came down some distance from the pad on a chute release, whereas most of the flights of the day had been coming directly down near the pad. A subsequent flight on the same pad did a similar pitch for no apparent reason.
It was suggested several times that I add more nose weight. However, the computer simulations suggest that adding more nose weight actually makes the stability problem worse.
Interestingly, the motors that simmed the best stability wise prior to launch were: J460T (1.82 calibers), J540T (1.65 calibers), and K535 (1.55 calibers)
I guess my question is: does anyone know what might cause an I500 to wobble straight off the pad in this way?
View attachment Endeavourflight1.mp4
For now, I am puzzled.
Perhaps I should fly it again on a more powerful motor with a better computer stability rating to see if that improves it.
Lets start at the beginning. I purchased secondhand a PML Endeavour, which I repainted and added a third rail guide to, along with an Aeropak retainer and Aeropak Adapter down to 38mm from 54mm. Now, other than that, the rocket is as it was when I purchased it. No additional nose weight or significant modications have been done under my ownership.
Now, as I looked at the rocket prior to launch in Open Rocket, it simmed to around 3412 grams or approximately 7.522 lbs.
Individual component weights were: Nosecone (325 grams), Payload (881 grams), and Fin Can (2206 grams.) At this point, the rocket had a stability in Open Rocket of 2.93 calibers.
It was noted prior to launch that any motor below a J460T would result in a caliber rating above 2.0 calibers. A J420R registered about 2.1 calibers. Ultimately however, I was advised that certain motors can straighten out a rocket path well enough off the pad as long as the thrust to weight is something above 7:1. Closer to 10:1 was best as I was told. Taking this information with the goal of a lower altitude flight, ultimately we settled on an I500 single use. Which, as I was told, would "straighten anything out off the pad," and that stability really shouldn't matter much except when the rocket was "higher up" in this case.
I should also note there was very little wind that day, if any.
When the rocket came off the pad however, it almost immediately pitched several degrees north and altered the flight path. It came down some distance from the pad on a chute release, whereas most of the flights of the day had been coming directly down near the pad. A subsequent flight on the same pad did a similar pitch for no apparent reason.
It was suggested several times that I add more nose weight. However, the computer simulations suggest that adding more nose weight actually makes the stability problem worse.
Interestingly, the motors that simmed the best stability wise prior to launch were: J460T (1.82 calibers), J540T (1.65 calibers), and K535 (1.55 calibers)
I guess my question is: does anyone know what might cause an I500 to wobble straight off the pad in this way?
View attachment Endeavourflight1.mp4
For now, I am puzzled.
Perhaps I should fly it again on a more powerful motor with a better computer stability rating to see if that improves it.