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  #1  
Old 01-19-2023, 05:37 PM
MrTwisty MrTwisty is offline
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Default Dissolving parachute/nose cone link

....out of Lifesaver candy.
We got tired of losing rockets in hundred foot trees so we brainstormed on some type of dissolvable link (credit to the daughter for coming up with lifesavers)
With high humidity and no rain it can dissolve in 2 days, rain will of course accelerate that.
If you're in a dry area your mileage may vary. But in that case hopefully you can find an area without trees.

Pretty simple idea. It may look like it will unravel but we've had zero failures during many, many launches.

First you need the classic Lifesaver candy.
Cut the shock cord about 5 inches from the nose cone, at an angle (the angle cut makes it much easier to thread through the candy).
You don't want any actual knots- they can get hung up on bark or a crook on a tree branch.
Easiest if you loop the parachute cord through the candy first.
Thread once piece of shock cord through the candy and repeat for 2-3 wraps depending on shock cord size.
Then thread the other piece in the opposite direction (that way if one starts to loosens it tightens on the other cord).
One candy can be used for multiple launches in a day but be sure to remove at the end of launches because it will dissolve in storage and make a mess.
Don't eat the used candy

Hopefully someone can benefit from this and save a rocket.
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  #2  
Old 01-19-2023, 07:22 PM
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LeeR LeeR is offline
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SWEET!

(Pretty clever, too!)
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  #3  
Old 01-19-2023, 08:35 PM
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That is quite the interesting idea!
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  #4  
Old 01-23-2023, 04:19 AM
Linville86 Linville86 is offline
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That's a great idea. I wonder if water dissolvable thread or string would work as well. You can buy it from Amazon. I may try this to see how it works. Trees and humidity, Kentucky has both.
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Old 01-24-2023, 11:17 AM
MrTwisty MrTwisty is offline
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Quote:
Originally Posted by Linville86
That's a great idea. I wonder if water dissolvable thread or string would work as well. You can buy it from Amazon. I may try this to see how it works. Trees and humidity, Kentucky has both.

My first idea was biodegradable plastic bags that break down in UV light.
My buddy thought of dissolvable sutures for surgeries.
Lifesaver works pretty good. Just recovered a rocket yesterday that was only stuck at the top of a 60 foot oak for about a day.
Unfortunately we had a heavy rain come through instead of just humidity and the motor is swollen and stuck but the BT dried out well and is still rigid.
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Old 01-25-2023, 05:58 PM
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luke strawwalker luke strawwalker is offline
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Great idea...

The Discoverer spy satellite film buckets that had to return the spy sat camera's film to Earth used a similar system... it had a dissolvable plug installed on it so that if it didn't get caught in midair and landed in the water, after a few hours or so the plug would dissolve, flood the film bucket with seawater, and sink. That way the Navy had a shot at recovering a wayward film bucket if they could get to it quick enough, but if it landed off target or the Navy couldn't get it for whatever reason, it would sink before the Soviets could get it. The plug was basically a hollow bushing threaded into a hole in the film bucket, which had a plug cast into the center of it made of salt... the seawater would dissolve the salt plug over a given number of hours and then presto-- she sinks.

Have you had any of them lifesavers break on you from deployment forces?? That'd be my luck! I had a brand spanking new Estes Maniac decades ago that I'd gotten at a local electrical supply that sold rocket and model airplane stuff because the owner was into it, and it had been on a display rack in the sun a bit too long-- the stupid rubber shock cord Estes used had degraded from sunlight but LOOKED A-OK, until the rocket ejected at altitude and the thing popped-- she streamlined in and the tube end dug about 2 inches deep into the clay soil of the pasture before she would go no more, and the tube started accordioning itself... it crushed for a few inches until the trapped air in the tube finally pressurized enough to exceed the seam strength of the spiral tube and it EXPLODED with a very loud bang! Split the tube from the accordion folded section (about 5-6 inches long IIRC down to about 2 inches above the fin can. I cut the tube off there and installed a coupler to make it a first stage for one of my other Maniacs (which I flew Astrocams on back in the day because the Maniac was the only rocket that used the same tube size as the Astrocam... the former Cineroc "Challenger II" booster tube BT-56). I contacted Estes and they sent me a new Maniac free of charge, which was nice. Had to chase the nosecone and parachute for a half mile or so but managed to get it back too.

I was thinking you were using a pen tube and some kind of anchor slid into it, melting the candy, and then pouring it in there to harden or something.

The UV trash bags or whatever is a good idea too, but takes longer... I once tried "Greenfield" biodegradable baler twine on the farm-- it's basically plastic baler twine without the UV protectants that preserve the plastic in it. Supposed to break down in a year, so you don't get stray twine everywhere making a mess on the farm. Problem is, it breaks down and you move the bales and they fall apart, UP TOP where the sun shines on them the most. The twine on bottom where it's covered and out of the sun, is perfectly intact even a year later... if it's buried or mashed into the ground, it will NEVER disintegrate because there's no UV exposure... back to the drawing board! Stuff is IMHO worthless for the job, and I see TSC don't even sell it anymore.
Later! OL J R
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Old 01-25-2023, 07:11 PM
MrTwisty MrTwisty is offline
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That maniac is about the worst crash I've heard of, but then I don't actually know anybody in the real world that does rockets- I'm on my own out here.

As for the lifesavers I've had zero failures, even with Kevlar shock cords. I've gone through a couple packs so far. I will repack if I'm doing multiple launches on a rocket in one day but I won't reuse a Lifesaver a second day. Heaviest rocket was 205g.
I don't modify the Lifesaver, I just keep a roll in the garage fridge and pop one out when I'm loading the motor.
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