Decent Rates

[Robfire75]

I recently have gotten myself back into the high power realm and flying again after a 12+ yeah hiatus. I certified(again) in August. My questions come from the launch last weekend and having electronics to give me an idea of flight profile. The rocket I was flying is a modified PML Miranda, I did build photos of it here many years ago and the rocket weighs somewhere between 7 and 8 pounds depending on the motor. I flew on an I-175 on Sunday to 1150', the Altus Metrum deployed right at apogee and main came out about 450'.
On to the topic....the decent rate under drogue was 51 fp/s I am guessing this is an ok value, however when the main deployed the decent rate was 26 fp/s. I am thinking this is a little fast still, the rocket is built like a tank but still....I am just curious if I need to bump up the main chute size(currently stock PML 36" chute). I do not remember it coming down so fast last time it flew.

 

[tim cubbedge]

You're going to get many answers here but I shoot for 20-25 fps under main. A lot also depends on the field you fly at. We fly in open area which at times has deep weeds and makes the landing pretty soft. Landing on a road or hard packed dirt at that speed might cause some damage depending on construction.

 

[Nytrunner]

I agree with Timb

Also, 51 ft/s could be considered a little slow under drogue. Could go a little faster and reduce your drogue descent time (and decrease drift accordingly)

 

[Flyfalcons]

That sounds fast but I usually get a bigger chute than necessary. At that weight I'd use 45"-50" minimum.

 

[teepot]

I recently have gotten myself back into the high power realm and flying again after a 12+ yeah hiatus. I certified(again) in August. My questions come from the launch last weekend and having electronics to give me an idea of flight profile. The rocket I was flying is a modified PML Miranda, I did build photos of it here many years ago and the rocket weighs somewhere between 7 and 8 pounds depending on the motor. I flew on an I-175 on Sunday to 1150', the Altus Metrum deployed right at apogee and main came out about 450'.
On to the topic....the decent rate under drogue was 51 fp/s I am guessing this is an ok value, however when the main deployed the decent rate was 26 fp/s. I am thinking this is a little fast still, the rocket is built like a tank but still....I am just curious if I need to bump up the main chute size(currently stock PML 36" chute). I do not remember it coming down so fast last time it flew.

I have a 8 foot chute in my 7 pound rocket. Expect 12 fps decent. We fly on a hard as cement dry lake bed. Used a parachute size calculator to get the size/decent rate I wanted.