# Parachute spill hole and drift distance

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#### Scott Nokes

##### Well-Known Member
Hello all.

I have a two fold question here regarding two different models. The first is.

I have the pratt hobbies D Region Tomahawk that is streamer recovered and its about 4 ft lon and 3 inches wide. Its the yellow caution tape.
I want to replace it with a parachute and i have a small field and rocksim gives me a decent rate of 12fps. If i use a Estes 12 in chute and cut the spill hole out, how much faster would the model descend.?

The second thing is the way to work out how far my rocket will drift. My field is about 500ft x 500 approx.
I'm going to use a B6 which rocksim says will take it to 248 ft so that keeping it low for my small field but i don't know how to calculate the drift. I'm bad at math's.

The model weighs about 1.4 oz's.

Thank you

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The second thing is the way to work out how far my rocket will drift. My field is about 500ft x 500 approx.
I'm going to use a B6 which rocksim says will take it to 248 ft so that keeping it low for my small field but i don't know how to calculate the drift. I'm bad at math's.

The model weighs about 14 oz's.
You're not flying a 14 oz model on a B6. Go recheck your numbers.

Did you mean 1.4 oz?

Hello all.

I have a two fold question here regarding two different models. The first is.

I have the pratt hobbies D Region Tomahawk that is streamer recovered and its about 4 ft lon and 3 inches wide. Its the yellow caution tape.
I want to replace it with a parachute and i have a small field and rocksim gives me a decent rate of 12fps. If i use a Estes 12 in chute and cut the spill hole out, how much faster would the model descend.?

The second thing is the way to work out how far my rocket will drift. My field is about 500ft x 500 approx.
I'm going to use a B6 which rocksim says will take it to 248 ft so that keeping it low for my small field but i don't know how to calculate the drift. I'm bad at math's.

The model weighs about 14 oz's.

Thank you
Decent Rate, see chart below. It is from Sport Rocketr Magazine, May/June 2008

In regard to drift, rocksim should tell you that, once you plug in the wind speed.

Hello all.

I have a two fold question here regarding two different models. The first is.

I have the pratt hobbies D Region Tomahawk that is streamer recovered and its about 4 ft lon and 3 inches wide. Its the yellow caution tape.
I want to replace it with a parachute and i have a small field and rocksim gives me a decent rate of 12fps. If i use a Estes 12 in chute and cut the spill hole out, how much faster would the model descend.?

The second thing is the way to work out how far my rocket will drift. My field is about 500ft x 500 approx.
I'm going to use a B6 which rocksim says will take it to 248 ft so that keeping it low for my small field but i don't know how to calculate the drift. I'm bad at math's.

The model weighs about 14 oz's.

Thank you
Not to difficult and pretty simple math.

Divide your altitude in ft. by the decent rate in ft/sec. This will equal your decent time in seconds.

Multiply wind speed in mph by 3600 (seconds in one hour) and divide the result by 5280 (feet in a mile) and the result is your wind speed in ft/sec.

Multiply your winds speed in ft/sec by your decent time in seconds and that will give you the distant your rocket will drift.

The caveat on this is how many feet into or with the wind will the rocket reach apogee. This will need to be subtracted or added to your drift distance.

Not to difficult and pretty simple math.

Divide your altitude in ft. by the decent rate in ft/sec. This will equal your decent time in seconds.

Multiply wind speed in mph by 3600 (seconds in one hour) and divide the result by 5280 (feet in a mile) and the result is your wind speed in ft/sec.

Multiply your winds speed in ft/sec by your decent time in seconds and that will give you the distant your rocket will drift.

The caveat on this is how many feet into or with the wind will the rocket reach apogee. This will need to be subtracted or added to your drift distance.
If the wind is reported in knots use 6080 feet in a mile.

Why bother with a chute in the first place?

Decent Rate, see chart below. It is from Sport Rocketr Magazine, May/June 2008

In regard to drift, rocksim should tell you that, once you plug in the wind speed.

View attachment 579181
That chart is meaningless, because the rocket mass is not given.

Meters per second is properly abbreviated as m/s, not MPS.

That chart is meaningless, because the rocket mass is not given.

Meters per second is properly abbreviated as m/s, not MPS.
It shows a decent rate deviation of 80% when a spill hole is added. That is one of the questions the OP asked.
... If i use a Estes 12 in chute and cut the spill hole out, how much faster would the model descend.?