Harness Setup Question

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mccordmw

Look at my overall picture and how the harness zigzags. My lengths are much longer than what you described.

I'm at least 4 body lengths on each section.

I use 5-4x's the length of rocket and always keep the drogue longer than the main. Opinions will differ.
 
I always use much longer harness length between the booster and the payload bay. The length between payload bay and nose cone can be much shorter. I think of it in terms of how much deceleration I'm possibly going to see. Sure, the rocket will be near apogee on drogue deployment, so it won't be falling fast, but that's only on a perfectly straight up and down flight. A tiny bit of horizontal movement will quickly mean your deployment speed is quite fast.

To alleviate the shock, I use a longer line to allow for less snap when the drogue opens.

On drogue, you're likely falling around 18-25 m/s. When the main deploys, that's not as much possible snap as when the drogue deploys. That means you don't need as much harness to absorb that shock.

I've been going with a general length of:
Booster to payload (drogue deploy) = 2-3x total body length
Payload to nose cone (main deploy) = 1x total body length

People have all sorts of preferences though.

That is all good as long as you use a drogue and the drogue is the right size so it keeps the payload well above the fin can.

I've seen many drogueless or very small drogue rockets where the fincan is at or above the payload when the main opens. That is where that long drogue shock cord can hurt. When the main opens with just the payload as weight, it slow much more then if the whole rocket was on it. While it slows down a lot, that fin can keeps falling until it hits the end of that long cord and then your shock loads get very high. This isn't usually a problem on L1 sized rockets and on most L2, but when the fincan starts getting heavy with L3 rockets, I've seen large U-bolts ripped out of 3/4" aircraft plywood centering rings when the fin can hits the end of that long shock cord. Any fin can free falling isn't a pretty sight, but a large L3 one is worse.
 
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