- This topic has 14 replies, 5 voices, and was last updated 18 years, 1 month ago by
MikeS.
MikeS.-
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MikeS
A rocket I am going to fly at oktoberfest is 7.75′ X 5.5″ and is wieghing
in at about 9lbs wo/engine.It came with a 60″ chute. I will be adding a 18″ or 24″ drogue.
It floated down very well under the 60″, before the electronics bay. When
it weighed 6.5lbs.Is the 60″ and the drogue going to be enough?
What size drogue is the best? Most seem to be 18″
Is one 78″ better that two 36″? I would have to buy a 78″ but not two 36″
I also have two 60″….How bad of an overkill is that?
I will not be going real high with the launch (1650′). And the Primary will come out at 1000′.
Thanks:Mike
elviss_boy
My Denali wieghed in about 15 to 20 pounds. I had a 15′ chute and 3 ‘drouge. For a 9lbs rocket 60″ may be a bit on the small side. Maybe a 84″? And I would try to avoid two chutes. If one does not open your coming down on a 3′ main and 3’ drouge and that would be below average.
Chris LaPanse
Keep in mind that area, not diameter, is what matters. So, a 72″ would be the equivalent of 4 36’s, not 2. I also agree that a single 60 sounds a bit small – I would go with a 72 to 96 incher, depending on how slowly you want it to come in. A Rocket Rage RRQS15 would be ideal, though a bit more on the expensive side (best quality chutes I’ve ever seen though).
Doug Gerrard
A Rocket Rage RRQS15 would be ideal
Mike, you should greatly oversize your Rocket Rage chute if you like your rocket to land softly. The RRQS15 will bring it down but more on the 25 fps rate. I have a RRQS30 you could borrow at Oktoberfest.
Doug
MikeS
Advice well taken. I will build ahead as I do most of the time. Bigger is
better. I quess at this point. I would rater launch a couple Js with a shorter
bird.I’l see what goes on between now and then.
I’l probably slow down and get my level 2 out of the way then decide.
Thanks
Chris LaPanse
A Rocket Rage RRQS15 would be ideal
Mike, you should greatly oversize your Rocket Rage chute if you like your rocket to land softly. The RRQS15 will bring it down but more on the 25 fps rate. I have a RRQS30 you could borrow at Oktoberfest.
Doug
With 9lbs?
The 15 would be fine- it would come in at 10-12 fps.
Doug Gerrard
With 9lbs?
The 15 would be fine- it would come in at 10-12 fps.
Chris, how many times you’ve used Rocket Rage Chutes? Did you measure the descent rate using them? I have used them and I can tell you it won’t come down slower than 12 fps. I love the chutes and I agree it will come in fine at with the RRQS15 but not at 12 fps. But I’ll do more than talk. Are you willing to put money behind your claim?
At Oktoberfest, if Mike agrees we’ll use his rocket and fly it with a RRQS15 I’ll provide and measure it’s descent rate. If it comes down faster slower than 12 fps Mike keeps the chute. If it comes down faster than 15 fps you buy him a RRQS30. If it comes in between 12 and 15 fps we call it a draw. Are you game? We’ll even get an independent judge to download the altimeter data and declare the results. Consider it a good way to help out a beginner since we’ve both been flying for such a long time.
Doug
Chris LaPanse
I have never measured the descent rate on the 15, no. My 50 however comes in at about 9-15fps with 29lbs of load at the north site. The 15, assuming similar drag characteristics, should come down even similarly with 9lbs. I’ve dropped 14lbs perfectly fine under the RRQS15 (though without a recording alt unfortunately), and it appeared to be descending in the 20fps range from eyeball guesstimation. I won’t claim any level of accuracy with that though.
As for money behind my claim? Not right now – I don’t have the money to risk. I’m trying to build my L2 project for MHM, and between that and college, I can’t afford another $130 chute. Sorry. I would love to see data about the chute if you have some implying that I’m wrong – though if their published numbers are correct (15lbs at standard conditions at 22fps), 9lbs at the north site (5400 feet) should be about 15fps. My experience has shown that the chutes tend to come in even slower than this, as on my measured flight with the RRQS50 should have come in at 15fps as well, when the measured values ranged between 9 and 15fps.
Ed Dawson
Those RocketRage chutes are the best. I’d gladly trade every piece of PML, LOC, and Army surplus junk I own in for one.
I borrowed Doug’s RRQS70 for my L3 and it was a thing of beauty….. No, wait…. any parachute deploying on an L3 is a thing of beauty.
Really, thanks again Doug!
Ed Dawson
Your descent rate questions got me thinking, so I went back to the altimeter data from my “Just Do It” flight.
The descent rate under the RRQS70 main was right at 20fps for a rocket that would have weighed 38 lbs 6ounces after propellant burnout.
Ed
MikeS
elviss_boy
Chris LaPanse
Doug Gerrard
Ed Dawson
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