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Why spillholes in chutes?

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LarryH

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I see it often recommended here that on some kits you should cut a spillhole in the chute. Is this so the rocket will fall faster and land closer to home, or is there another reason? Of all the kits I've built I've never cut a spillhole in the chute(though I have had the recovery charge cut a spillhole at times when I didnt use enough wadding!) and was wondering what kind of advantages I might see if I did, also how and where is the spillhole usually cut, I would assume in the center, just fold the chute and cut off the tip of the spike, when cutting a spillhole how big of a hole should I cut?
 

sandman

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The spill hole is cut in the center (sometimes I just cut an "X" in the middle).

Or cut the "SEMROC, FLISKITS, or ESTES (pick the appropriate logo) emblem out.

It does three things.

Makes the rocket fall a bit faster...not much.

Makes the for much less drift. (sideways motion)

And reduces occelation. (the back and forth pedulum action)

sandman
 

vjp

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I seem to remember reading that spillholes help prevent the side-to-side rocking that many parachutes suffer from.

I think the most stable chute design of all, incorporates a small spillhole in the main chute, plus a band of fabric beneath the main chute, a la the Mars Rover design:

http://www.pbs.org/wgbh/nova/mars/parachute.html


...I'd love to see someone design a "RockSim"-style program for parachutes.
 

LarryH

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Thanks guys, that's sorta what I figured, doesn't hurt to be sure though, I am getting just a 'little' tired of chasing rockets several hundred feet from where I launched them.:)
 

shockwaveriderz

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replace the parachute with a streamer or use a spill hole with the shroud lines "reefed" , ie apply a piece of tape around all the shroud line up towards the top of the canopy so the parachute will not open fully.....these techniques will reduce the drift distance......

a lesser know technique and not for the timid nor inexperienced rocketeer is to tilt the launch rod into the wind and use a short delay 2-3.... this will result in the rocket weathercocking SEVERELY and gravity turning into the wind, reducing its altitude and the chute will open up only a few hundred few above the ground and drift right back over the launch site......

obviously if you do this wrong the rocket will power prang or post hole itself.....hence the caveat.......
 

LarryH

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Shockwave, that's the technique I've been using, except when I want the chute to open closer to the ground I use a longer delay not a shorter delay, but I always angle my launch rod into the wind...... always thought that was the way you were supposed to do it?:confused:
 

wwattles

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Having experienced first-hand an early ejection this past weekend, I'd be more apt to suggest reefing in the chute or cutting a spillhole. Of course, a smaller chute might also be in order. Too short a delay will cause the chute to pop out much too soo, and the velocity can 1) zipper your tube and/or 2) shred your chute.

WW
 

rbeckey

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I live in an area with lots of hills and trees. The largest fields that are available for use are still surrounded by trees. Needless to say, I don't walk too far for rockets, because if they drift very far they are hanging in branches, usually high enough to cause a nosebleed! I HATE when that happens! This caused my philosophy about building and flying to become somewhat conservative.
I build the rockets I want to keep a little stouter than most would and use a smaller chute. For instance, I have a Big Bertha that I use a 12 inch chute on. It has lite ply fins with epoxy fillets. It comes down fast, but it is not damaged because it is much stronger than the usual Bertha. It also is not hanging in a tree like some kind of weird Christmas ornament. On some kits I use wood hardener on the stock fins and cover them with self adhesive paper. Basswod fins on others. The lite ply is tough stuff. I had a 2.6 inch V2 fall from apogee after a shock cord failure without damage. It has lite ply fins and epoxy construction. My Estes Wizard got stock fins. I don't mind so much if I have to replace a Wizard, as say compared to my Deuce, V2 or something I spent some time and money on.
I pay a price in altitude, but I am (usually) not building once and done tree decorations. The toughest rocket I have is a Rocket Vision Check Six, a minimum diameter 24mm bird with phenolic BT, hard plastic NC and G10 fins. It uses a 6 or 8 inch chute and always lands in the large field on a D12 7. On smaller fields or windy days I use a C11 5. It once darted after ejecting the motor and suffered no damage. I swear you could hammer it into the ground.
I think that most Estes chutes are oversized for the job. Try the next size down or cut a large spillhole unless your recovery area is hardpan or pavement. If you do downsize recovery, try stronger fin materials. Basswood is stronger than balsa and can be used without much weight penalty. Lite ply is stronger yet, but is unsuitable for most small rockets as the smallest thickness available is 1/8th inch. It is also harder to work with.
I do not adjust recovery times by selecting longer or shorter delays. In my experience, an improper delay causes recovery sytem damage and failure. If the chute ejects way before apogee, the rocket is still moving so fast that the chute shreds and/or the BT zippers. If it falls too far after apogee before ejecting, it has gained momentum and is again moving too fast for safe deployment. Down size the engine WITH the delay. Instead of insisting on a C6 7 on that windy day, go with the B6 4 and get the rocket back to fly again when things are a little more predictable. Or build a little heavier with a smaller chute and use a C6 5 or even C6 3 as appropriate and don't walk as far.
That is just one person's experience and opinion. As it is free, consider its value before applying to your situation. ;)
 

shockwaveriderz

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larry:
short/medium/long....it all depends on the wind speed,engine characteristics,rocket weight/drag,etc....
thats why I said it wasn't for the timid or inexperienced..
every combo wil be different ....
when you launch into the wind the rocket of course does a gravity turn upwind(into the wind) and flys into the wind...horizontally.....which reduces the altitude..the lower the altitude,the shorter delay show be....so in general we agree, but as I said earlier, it depends on a number of factors....too long a delay using this technique and the rocket meets the ground way too soon... so reefing the chute/spill holes are easier to use and probably safer too...

if you are trying for max altitude you lauch with the wind.......
 
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