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  #11  
Old 08-03-2005, 04:53 PM
qmodeling qmodeling is offline
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No the MRS-ROGUE and MRS-WACC had the 18" chute. The MRS-SNOOPER had a 30" chute and again the MRS-ANDROMEDA had a 30" chute packed into a BT-52 tube.


By baffle I mean supplying a parachute C-Ring to form a parachute compartment. My thinking here is the recovery system won't fall to the rear of the tube during acceleration and thus it will be closer to the nose cone.

Does it make sense to move the snap ring closer to the nose cone? Instead of at the shock cord 1/3 spot maybe 8" away?


Again it just seemed like either the Estes engines didn't have enough poop or the gases were just blowing by. The only reason I don't go for the gases going by is because at NERRF we didn't have any trouble and the MRS-SNOOPER was a 30" recovery system pack in a BT-60 tube and it still didn't come out.
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  #12  
Old 08-03-2005, 05:17 PM
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BobCox BobCox is offline
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Quote:
Originally Posted by qmodeling
No the MRS-ROGUE and MRS-WACC had the 18" chute. The MRS-SNOOPER had a 30" chute and again the MRS-ANDROMEDA had a 30" chute packed into a BT-52 tube.

I'm amazed that you fit the 30-inch chute package into a BT-52. It's already a snug fit in a BT-60. It must be packed like a flauta instead of a burrito, huh?

Quote:
Does it make sense to move the snap ring closer to the nose cone? Instead of at the shock cord 1/3 spot maybe 8" away?

That might help pull the chute out of the body. However, on some of my other rockets I found that clipping the chute close to the nose cone increases the likelihood that the nose cone will pass between the shroud lines and cause them to partially tangle.

Q: When the chute got stuck in the body, was the entire recovery package stuck? Did the bundle come out partway? Did any of the shroud lines get pulled free or were they still wrapped up inside the heat shield?

Quote:
Again it just seemed like either the Estes engines didn't have enough poop or the gases were just blowing by. The only reason I don't go for the gases going by is because at NERRF we didn't have any trouble and the MRS-SNOOPER was a 30" recovery system pack in a BT-60 tube and it still didn't come out.

Could the humidity make a difference? I wonder if humidity would make the tubing swell resulting in a tighter nose cone fit. Or maybe it would make the interior of the tubing "sticky" so that the chute package wouldn't slide as easily.
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  #13  
Old 08-03-2005, 06:54 PM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by qmodeling
Again it just seemed like either the Estes engines didn't have enough poop or the gases were just blowing by. The only reason I don't go for the gases going by is because at NERRF we didn't have any trouble and the MRS-SNOOPER was a 30" recovery system pack in a BT-60 tube and it still didn't come out.
I've had problems with one rocket that seemed to crash every other flight. The chute seemed to just hug the wall and let the ejection charge go by. It must have wrecked three or four times with the nosecone popped but the laundry still inside.

My experience with the new 24mm motors (C11s, E9s and recent vintage D12s) is that they have plenty of oomph in the ejection charges. Way plenty. Not that you couldn't have gotten some bad ones, but I think the problem may lie elsewhere.

How good of a seal are you getting in the MMT? Could some of the ejection gases be coming out around the motor? It doesn't take too much of a leak to reduce the back pressure on the BP ejection charge resulting in a poor burn and a wimpy ejection. That can be cured with one or two wraps of tape.

Another thought is to use more wadding. Several sheets layered to form a piston of sorts under the laundry.

You mentioned where to connect the chute. I prefer to connect it right at the NC. If the NC is out, then the suspension lines should be, too. Furthermore, borrowing from HPR, I pack the chute on top of the shock cord so that it's the first thing out after the NC. This is contrary to ancient doctrine, but I've never come up with reasonable explanation why the shock cord should be on top of the chute.

My two cents. YMMV.

Doug
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  #14  
Old 08-03-2005, 07:05 PM
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BobCox BobCox is offline
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Quote:
Originally Posted by Doug Sams
My experience with the new 24mm motors (C11s, E9s and recent vintage D12s) is that they have plenty of oomph in the ejection charges. Way plenty. Not that you couldn't have gotten some bad ones, but I think the problem may lie elsewhere.

I'd agree with you that MOST Estes 24mm motors have an excess of ejection charge. I have seen one E9 that didn't, though, and I have photos to prove it.

Quote:
Another thought is to use more wadding. Several sheets layered to form a piston of sorts under the laundry.

No wadding was used. QModeling kits use a Nomex heat shield wrapped around the chute like a burrito. It fills the body tube pretty full. I doubt that more wadding would help.
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  #15  
Old 08-03-2005, 07:45 PM
A Fish Named Wallyum A Fish Named Wallyum is offline
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Quote:
Originally Posted by Doug Sams
How good of a seal are you getting in the MMT? Could some of the ejection gases be coming out around the motor? It doesn't take too much of a leak to reduce the back pressure on the BP ejection charge resulting in a poor burn and a wimpy ejection. That can be cured with one or two wraps of tape.


This is along the lines of what I was thinking also. The mounts look great, but it seems that they'd pose a higher than normal risk of exhaust leak. I've never built one, mind you, but I've seen all the pics associated with the reviews.
Like Doug says, YMMV.
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Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Gee'Hod, Shrike, SST Shuttle

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  #16  
Old 08-03-2005, 08:54 PM
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BobCox BobCox is offline
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Quote:
Originally Posted by A Fish Named Wallyum
This is along the lines of what I was thinking also. The mounts look great, but it seems that they'd pose a higher than normal risk of exhaust leak.
I've never built one, mind you, but I've seen all the pics associated with the reviews.

I've built three of them -- one BT-60 and two BT-80 designs. I don't know why they would be any more prone to ejection leak than any other design. The balsa "cage" around the mount has lots of holes to cut the weight, but both ends are covered by plates that are sealed to the motor tube and main body tube. The only leakage path they should have is around the engine itself.
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  #17  
Old 08-04-2005, 09:49 AM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by BobCox
I don't know why they would be any more prone to ejection leak than any other design. The balsa "cage" around the mount has lots of holes to cut the weight, but both ends are covered by plates that are sealed to the motor tube and main body tube. The only leakage path they should have is around the engine itself.
Yes, around the motor, that's what I was talking about. Some of the 3rd party, thick walled motor tubes have slightly larger inside diameters. This makes it easier to insert the sometimes "fat" BP motors, but can also result in a loose fit for the non-fat ones. A couple wraps of tape on the motor will seal this up. The first one that comes to mind is the foil lined Totally Tubular T-50mf (IIRC). It's definitely bigger inside than an Estes BT-50.

Doug

PS, please don't anyone get me wrong. I truly like the thick walled 24mm tubes. They're much more robust than the 0.013" walled BT-50 (in MMT applications). But a little extra prep may be required when using them. DS.
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  #18  
Old 08-17-2005, 08:37 AM
jflis jflis is offline
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Quote:
Originally Posted by Doug Sams
Tell us more about the big Porta-Pad. It's pretty kewl. Whose was it? There's a faint idea in the cobwebs of my mind that I've seen that thing before, but I'm not sure.


That's my pad. It's a 3.5:1 upscale port-a-pad. I built it years ago as I had built a collection of upscale Estes kits in the 3:1 - 4:1 ratio and wanted a pad to fly them on

You may have seen it if you ever attened Pearl River MODRoc convention in NY or visited my personal web site. You can see a picture of it here:

http://jflis.com/hobbies/rocketry/photos/collection.jpg

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  #19  
Old 08-17-2005, 05:42 PM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by jflis
You may have seen it if you ever attened Pearl River MODRoc convention in NY or visited my personal web site. You can see a picture of it here:
Jim, I may have seen it on your site, likely because someone posted a link on one of the rocketry forums.

I've never been there, but one of my favorite fraternity brothers at Kentucky was a Pearl River native.

Doug
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