A few flights this year, all with the Pro24 dual thrust motors (https://ausrocketry.com.au/hp139g107-12a-w-dt). These have a short 0.25 s burst @ 220 N, followed by a longer ‘sustain’ @ 100 N.
All the flights show a similar ‘wiggle’ off the rail. They seem to yaw 5 or 10 degrees under high power, then the aft fins pull it back straight during sustain. Various forum posts I have found suggest weather cocking, misaligned nozzle or misaligned engine. My personal favourite is the nozzle alignment as the reload assembly seems to have buckled just in front of the nozzle for each of the flights. However, I would have expected the internal pressure to push the nozzle square against the end closure. I doubt the entire engine can be quite so spectacularly off axis, and the rocket yaws in opposite directions relative to the wind in the two launches shown on the link below.
I’m planning a Pro29 launch of a 300 N motor (https://ausrocketry.com.au/206h237-13a-ss) using, in essence, the same platform. If it’s something to do with being somehow ‘overpowered’, I have a whole second of yaw to deal with. That might be a bad thing.
All thoughts or suggestions welcomed.
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