Projected altitudes are, in general, rather optimistic. From what you have shared, I’d more likely believe the 800 feet on a D12-5.

It seems that an unhealthy B4-4 (or a sticky launch rod) are the most likely.

But knowing what the models actually are will help.

Per the NAR cert data and time/thrust curves here https://www.nar.org/standards-and-t...ied-motor-list/ the initial thrust spike of both the Estes B4 and B6 motors is about 12 Newtons, and the B4 gets there a little sooner. 105g is a little over the recommended max liftoff weight for B4-4 per the same data…though based on the time/thrust curves I don’t understand why the recommended max is lower than the B6-4.

Estes C6 has a bit more initial thrust, but it takes 0.2s to get there.

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Bernard Cawley
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