jet foaming insert

Rocketry that will literally wet the appetite

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Rocket Flyer
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jet foaming insert

Postby kitestring » Mon Feb 16, 2015 1:24 pm

Hi George
Any chance you have any info on jet foaming inserts?
I couldn't find anything on your site.
PS: looking forward to seeing your launch at Thunda Down Under.
all the best Jeremy

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Location: Sydney, Australia

Re: jet foaming insert

Postby air.command » Mon Feb 16, 2015 1:50 pm

Hi Jeremy,

In it's basic form the jet foaming insert is really just a restricted orifice inside the rocket. The hole should be about the size of the nozzle or bigger, othewise you end up choking the flow from the upper part of the rocket. We used to use these: that would be held in place by the tornado tube. It's basically a lump of delrin that's been turned down to make it lighter. The commercial tornado tubes have a small hole in them so you could use them directly without needing a special insert. You could of course insert pretty much any kind of baffle with a small hole in it between the bottles.

In order for jet foaming to work properly you need to have some air in the lower bottle to mix with the water flowing from the upper chamber to create the foam. We have been using a piece of PVC pipe that extends down to where you want the water level to be, and the pipe has the restricted orifice in the bottom of it. This setup allows the water to self level within the rocket while you pressurise it.


The parts:

You don't strictly need it, but it does give you a consistent distribution of water if you are doing successive comparison flights.

See here for more info on the jet foaming spacer:

Will you bring your water rockets to Thunda as well?

- George
Crop Circles: ... just a bunch of guys looking for their rockets ....

Rocket Flyer
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Joined: Sat Nov 15, 2014 9:39 am

Re: jet foaming insert

Postby kitestring » Mon Feb 16, 2015 6:37 pm

Fantastic George!
Way more than I was hoping for.
Doing my first electronic recovery this weekend at our society astronomy camp ( and will look at adding the jet foaming if all survive, as I love those long burns. I had 3 launches over Christmas. All ended up in a mess of plastic...
I am only using pressures around 80-110psi as launcher etc is plastic hose and connectors and a simple compressor, but I think the foaming will still add to the results.
Hadn't really considered bringing rockets to Thunda as we are only camping, but may reconsider.
thanks again, look forward to meeting you if time permits.

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Re: jet foaming insert

Postby cryoscum » Mon Feb 16, 2015 7:13 pm

Would be good to see you again at Thunda, Jeremy. PLease feel free to bring a rocket or two! The more the merrier :)
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
AMRS Technical Advisory Group

Total impulse for 2016: 32,458 Ns (thus far)
Total impulse for 2015: 84,231 Ns
Total impulse for 2014: 40,757 Ns
Total impulse for 2013: 62,927 Ns

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