- Joined
- May 19, 2022
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Hello, building a 4in Cherokee 98 from Wildman and want to ground test my ejection charges. First time using ejection charges, want to do it right.
Using https://rocketrycalculator.com/rocketry-calculator/bp-estimator/ to estimate BP required - with 2x 4/40 nylon shear pins.
Empty, the payload bay is roughly 10 inches between the bulkheads - so at 4in diameter, 10in length, 10psi and 2x 4/40 the suggested BP charge = .61grams.
When I stuff the bay with my harness, chute and chute protector, the entire cavity is basically filled (tightly) and the chute protector sits just on top of the ejection wells (Firebird3g) - so I'm wondering if I need to reduce the weight of the BP charge, given it's not an empty space, full (and densely so). This is a fiberglass airframe and I certainly don't want to blow a hole in the frame, maybe that's dumb and it doesn't work that way, but I wanted to ask and see what folks generally do about this. Like what is the appropriate adjustment factor, if that's even necessary. I would note, the rolled chute covers the vent holes from the inside - given the amount of space the recovery components occupy, I don't see a way to clear the vent holes....
Thanks!
Using https://rocketrycalculator.com/rocketry-calculator/bp-estimator/ to estimate BP required - with 2x 4/40 nylon shear pins.
Empty, the payload bay is roughly 10 inches between the bulkheads - so at 4in diameter, 10in length, 10psi and 2x 4/40 the suggested BP charge = .61grams.
When I stuff the bay with my harness, chute and chute protector, the entire cavity is basically filled (tightly) and the chute protector sits just on top of the ejection wells (Firebird3g) - so I'm wondering if I need to reduce the weight of the BP charge, given it's not an empty space, full (and densely so). This is a fiberglass airframe and I certainly don't want to blow a hole in the frame, maybe that's dumb and it doesn't work that way, but I wanted to ask and see what folks generally do about this. Like what is the appropriate adjustment factor, if that's even necessary. I would note, the rolled chute covers the vent holes from the inside - given the amount of space the recovery components occupy, I don't see a way to clear the vent holes....
Thanks!
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