oh..'chute

[moocrew]

im getting ready to construct my parachute for my 3ft long 2 in diameter rocket.
I have Spacecad so it had done the math and says i need a 3ft chute!
Now the rocket will fly less than 200 ft and its weight at light off will be 1lb 6 oz
....so will a chute this large really be nessecary?.....i don't want the thing to drift 800 ft either....so could i mabey make it a bit smaller?

any opinions?

 

[BlueNinja]

Go with the 3ft and reef it.

 

[lalligood]

3 factors to determining proper chute size:

1) Weight of rocket without motor (since rocket usually only weighs slightly more with used motor casing).

2) Altitude above sea level where the rocket is being launched. (This doesn't need to be precise but just a general idea...)

3) Surface that the rocket will be landing on. (Soft grassy field? Hard as concrete playa?)

Having the answers to those 3 items can help greatly.

 

[moocrew]

1) 14.55 oz.
2) The highest point in Ohio is about 1,500 ft ...my area is roughly 500-600 ft
3) corn field/pasture basically just dirt not to hard.

 

[MetMan]

moocrew,

Mind if I ask why your 3' 2" diameter rocket is so heavy? Also, what motor do you plan to launch it with?

MetMan

 

[moocrew]

its wall thickness is about 1mm but its made of incredibly hard/dense plastic.
It was used as a shipping tube for a large roll of paper for a plotter/Scanner.

And I'm using fins that would fit into a box 350mm tall and 100mm wide made of 3mm basswood. not including the six smaller fins at the top of the rocket. They are half the size of the bottom ones.

And because I want a very low flight Im using 3 Estes B8 engines. 18mm wide.


I know it seems like it will never launch but this is more of a "concept/Test" rocket...thats why I want a low flight height.

 

[sandman]

1 pound 6 oz!

3 18mm motors!

Yer gonna need more motor!

sandman

 

[Stones]

With B8's.....
works out to about 48 ft. ....

 

[sandman]

works out to about 48 ft. ....

That's about what I thought!

sandman

 

[Neil]

Do they even *MAKE* B8s any more?

Go with 29MM. thatll be much better Get yourself a nice reload case and let er rip!

Where are you going to get your chute from? (just asking.... Are you going to try making one yourself?)

Make sure you get a kind of glue that sticks to plastic (or whatever your tube is made of). You dont want a blow-through!

 

[moocrew]

I found a nice 29mm and reload.
And the chute I might attempt to make myself...not likely though.

 

[Missileman]

Another factor is the shape of the chute itself.
A hemipherical chute has a much slower descent rate as a flat or X form chutes.
I use a 24" Hemi. chute with a spillhole on my Amraam. the rocket is 2"x41" it weighs in at 2lbs 1oz.
I saw a descent calculator somewhere that took into account type of chute but can't remember where.

 

[Stones]

Originally posted by missileman
...
I saw a descent calculator somewhere that took into account type of chute but can't remember where.

ROL has a few calculators for chutes.

Recovery Calculators

 

[Neil]

Well, I have a nice 36" 12 shroud line chute in stock if you get too fed-up with your sewing machine .

I would use ripstop nylon, with twisted nylon shroud lines. It helps a lot if you sew the sides under. If you dont, that stuff will frey like mad, and before long you will notice it go from 36" to 30" to 24" to 12" to a streamer

GOOD LUCK!

 

[DPatell]

May I suggest braided nylon, or Kevlar thread from Pratt Hobbies...the twisted stuff is a PITA and low quality...

 

[edwardw]

I personally like Braided Dacron. It is a dream. The 250# stuff I use is about 3/32 in diameter. The 100# is about 1/16. Great stuff.

Edward

 

[Neil]

Whats wrong with the twisted stuff? I have been using it for a year or two, and it works very well for me. What are the benifits of getting the braided stuff? Sounds more expensive to me... And does it come wrapped around a tube that is the exact same size an a 29MM coupler/motor? And the ID of these tubes is exactly 24MM, so its a good adaptor in a pinch!

I really dont see anything wrong with the stuff Ive got. Its plenty strong (#150 rated), and is easy to work with.

 

[edwardw]

If your chute twists a lot or the shroud lines twist - they can come untwisted. Then it starts to separate and then it starts to fray. It's nasty. I had a chute that had 200# twisted and after 4 flights the lines were starting to auto-tangle. I replaced with the 250# braided and have not had a problem. The twisted stuff has one way it likes to be - and if you twist it opposite then it comes undone a little, then twists back - most of the time not correctly and then it gets messy. The braided dacron I have is actually cheaper than the twisted stuff that I used to have. You actually have to work to fray it - with a needle and some patience.

The tube it comes on - I don't know what size it is and will be a long time before I find out - I bought a 5000' roll.

Edward

 

[Neil]

So where do you get it, again? Do you have a link?

 

[edwardw]

I got it from a friend who was clearing out a lot of old stuff. It was a great buy. I'll ask him where he got it.

Edward