Building fins

Water Rockets NSW

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water rocketry man
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Building fins

Postby water rocketry man » Wed Feb 20, 2008 3:39 pm

Hi everyone i want discuss fins for water rockets in the past few days im

have being trying my best to make light fins that will make a stable rocket
but so far all my fins i made have failed and im pretty much stuck here

under a 40 meter celling that i have not broke yet with a water rocket and i really need some tips on material shape and size.

Can somebody tell me where i can get a simulator that i can get where i can build water rockets.

from asher

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Postby krusty » Wed Feb 20, 2008 11:09 pm

Have you seen this?
http://antigravityresearch.com/

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Postby water rocketry man » Thu Feb 21, 2008 6:15 am

no but thanks hey would the fin set fit on a normal soda bottle

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Postby krusty » Thu Feb 21, 2008 8:36 am

Hi, they are designed to fit onto a normal bottle, but might give you some ideas.

You should also check out : http://www.aircommandrockets.com/

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Postby air.command » Thu Feb 21, 2008 10:16 am

Asher,

If the rocket is fairly small then a ring fin is probably the easiest (and lightest) to make out of another bottle. They work very well and tend to make the rocket spin less as well. We have found that skewer sticks work well as cheap struts. We have flown 1.5L bottles with these to well over 100m.

http://home.people.net.au/~aircommand/rocket_gallery.htm#Clifford
or
http://home.people.net.au/~aircommand/rocket_gallery.htm#DY

For larger rockets we use flat fins, but make them removable so that they can easily be swapped from rocket to rocket should the rocket become damaged.

http://home.people.net.au/~aircommand/day37.htm#diag_removablefins
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water rocketry man
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Postby water rocketry man » Thu Feb 21, 2008 3:22 pm

would the fins be usefull in windy conditions because on terranora its very windy :shock: also can you use four scewers for the fins.

one more detail i dont use a garden hose nozzle i drill a hole in the cap that is a 5 to 6 mm hole, its reasonably fast take off.

also does the nose cone really count on the rocket and the flight cp because when ever my rockets fly they always crash so i dont want to $$$ alot on the recovery system.

thanks for the fin design i will use it definetly also will two litre bottles go higher than smaller ones :?:

thanks from asher

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Postby air.command » Fri Feb 22, 2008 7:35 am

water rocketry man wrote:would the fins be usefull in windy conditions because on terranora its very windy :shock: also can you use four scewers for the fins.


The ring fin will experience similar weather-cocking behavior in windy conditions as regular fins. Best wait until the wind dies down a bit. Use as many skewers as you like as long as they keep the ring as rigid as possible.

one more detail i dont use a garden hose nozzle i drill a hole in the cap that is a 5 to 6 mm hole, its reasonably fast take off.


5-6mm is pretty small, that can be used in small rockets, but for larger rockets you definitely need bigger.

also does the nose cone really count on the rocket and the flight cp because when ever my rockets fly they always crash so i dont want to $$$ alot on the recovery system.


Not exactly sure what you are asking. The only reason you need a nosecone is for aerodynamics to have much less drag. As far as a recovery system goes that is up to you. If you build a good one, then your rockets won't always crash.

The cheapest way to recover your rocket is not to have a recovery system at all. You can build your nosecone out of soft foam that will cushion impact. This only works for very light rockets and often results in buckling of the bottle regardless. It is also quite dangerous if it hits someone, the rocket still can do over 100km/h on the way down. For larger rockets a parachute is highly recommended.


thanks for the fin design i will use it definetly also will two litre bottles go higher than smaller ones :?:


Depends on the weight of the rocket, the amount of water, pressure, nozzle size etc. Some designs allow a 2L bottle to go higher, other designs allow smaller ones to go higher. Although bigger bottles have more capacity, they are heavier and have a larger diameter and hence more drag, and generally can withstand less pressure.

Best way to find out is to run it through a simulator such as this:

http://cjh.polyplex.org/rockets/simulation/
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Postby Kryten » Fri Feb 22, 2008 11:51 am

air.command wrote:The cheapest way to recover your rocket is not to have a recovery system at all. You can build your nosecone out of soft foam that will cushion impact. This only works for very light rockets and often results in buckling of the bottle regardless. It is also quite dangerous if it hits someone, the rocket still can do over 100km/h on the way down.

Umm - this is the type that I was going to launch on Saturday.
But I won't be using more than 50psi
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Postby Rhodes » Fri Feb 22, 2008 11:55 am

You could also experiment with a set of canard fins to reduce the weather cocking. The rocket will still travel along with the wind but it should help at keeping it pointing straight up.

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Postby air.command » Fri Feb 22, 2008 12:48 pm

Kryten wrote:
air.command wrote:The cheapest way to recover your rocket is not to have a recovery system at all. You can build your nosecone out of soft foam that will cushion impact. This only works for very light rockets and often results in buckling of the bottle regardless. It is also quite dangerous if it hits someone, the rocket still can do over 100km/h on the way down.

Umm - this is the type that I was going to launch on Saturday.
But I won't be using more than 50psi


Looking forward to it Kryten!... you are more than welcome to use our launcher if you like. You should be able to get a bit more than 50 psi in it :D What are the specs on your rocket?
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Postby water rocketry man » Fri Feb 22, 2008 3:33 pm

Yes i heard of weather lock bad thing to sended my solid powered rocket into a RET :( (rocket eating tree).
well im puting about 1/4 or 1/3 ( 500ml to 700ml) of water sometimes

with foam i get a better flight :D also i belive the two liter sprite bottles are best for nose cones cause their more areodynamicly shaped i think

you should try making nose cones with spite bottles im going to try it to see weather the sprite ones are better. :D

Well 6mm isnt that small is it,well i think i will just stay with making 6mm holes with caps :)

hey hows the paloron IV rocket going have you found out a way to attach the gluon boosters are you also launching the rocket on the new launch pad

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Postby Kryten » Fri Feb 22, 2008 5:05 pm

air.command wrote:
Looking forward to it Kryten!... you are more than welcome to use our launcher if you like. You should be able to get a bit more than 50 psi in it :D What are the specs on your rocket?

My "nozzle" is just the spout on the bottle, so I'll need to use my own launcher. I might get RSI from the foot pump, though
Last time I tested it it went straight into a tree, so I'm hoping it'll survive pressurisation tomorrow
As for specs, I probably won't even bother you with those.
You can be suitably impressed when you see it for yourself :lol:
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Postby air.command » Fri Feb 22, 2008 6:18 pm

If it is just the neck of the bottle, we can screw in our nozzles as well. The big hole though will give you a nice acceleration. :D

See you tomorrow!
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Postby astroboy » Fri Feb 22, 2008 6:39 pm

Good luck guys, have some soggy fun action!
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Postby wimma » Mon Dec 01, 2008 9:49 am

Fins - You should have a look at this site and I also wanted to recommend you to another site in my bookmarks, but unfortunately it 404'd.
Anyway, the crux of it was that the best fin design for sub-sonic model rockets (I'm assuming a bottle rocket is subsonic... prove me wrong!) is 3 fins 120 degrees angular spacing, parallelogram shaped (angled down of course) and double-airfoil. Have a look [url=http://willem.110mb.com/wiki/index.php/Yet-to-be-named_big_water_rocket] here [/url for the fins I made for my WR.
Recovery - assuming you're just using a regular 2L soda bottle, just sticky tape a tennis ball onto the top. Works like a charm. If you're using spliced bottles, consider putting a counterweight inside of one of the bottles towards the bottom (work out CG and CD), and try out a backgliding recovery (this will require a specific fin design... here I would urge you to look at Robert Youens site, but hometown AOL has been shut down for some reason).
Otherwise go for the garbage bag parachute with basic inertial deployment... anything more complex is a waste unless you are building a spliced or FTC rocket.
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