Baffle trough - FTC vs Bottle

[RaZias]

I read the experience made by AirCommand, that water tends to rise by the sides of the bottle during the flight, so that water is not being ejected correctly:

http://www.youtube.com/watch?feature=player_embedded&v=RlPI1oiRbQQ

I don´t know if that happens to FTC.

Does this happens because the diameter of the bottle is much bigger than the nozzle ?

If so, the FTC by having a much smaller diameter difference (between the nozzle and body diameter) is less affected by the water rising ?

[RaZias]

I know that the water rising was due to the robison coupling that punched through water.

AirCommand later solved the problem by adding a baffle so the air pulse could be equaly distributed.

But the main question I am posting is to WR whose bottles are connected by glue and not by Robison couplings.

[Nick B]

us rockets has a thread somewhere with vid or pics on this issue. They mentioned something about adding a baffle to reduce it.


I really don't see how you can add a baffle to reduce dead weight water and not harm flow.

[Nick B]

It would probably be pretty easy to make a reverse tee nozzle that would work something like a internal aerospike. It would probably need to be kinda long, so you'd lose some launch tube length.

Then you would just have a simple long tee nozzle occupying the pressure chamber and side vents in the bottom to let your determined air and water flow through. Kinda opposite of the mist rocket.

[Nick B]

This would be super easy to do with a gardena coupler driven rocket, I think.

[Nick B]

Another thought that might work for those with robinson couplers without a baffle, just lengthen the coupler dia a tad and plug the ID and drill or notch in side vents, that way the air is not in a straight thrust into the center of the water mass, and you are directing the air along the tube walls.

[Nick B]

It would probably be pretty easy to make a reverse tee nozzle that would work something like a internal aerospike. It would probably need to be kinda long, so you'd lose some launch tube length.

Then you would just have a simple long tee nozzle occupying the pressure chamber and side vents in the bottom to let your determined air and water flow through. Kinda opposite of the mist rocket.

edit:


another option using a tee nozzle would be to only have the tee nozzle take in water from the sides of the rocket and obstruct the centerline opening. just by drilling holes in the edges and blocking the center opening.

[RaZias]

The main question remains answered:

Is the FTC more efficient to eject water because the difference between the body diameter and the nozzle diameter is lower than the bottle one ?

[Nick B]

Then you need somebody with heavy data like us rockets to reply.

And they might not have a complete answer other than conjecture, like us, anyway.


they may not want to touch on the subject due to design secrets.



You should just join us and build some ftc's if you have none.

[RaZias]

It would be pausible to make a static test, having a FTC and a bottle with the same air and water volume.

A camera would film it, after being seen in slow-motion it would be pausible to see wich one ejected it faster.

I don´t know what camera and visual program AirCommand uses to slow down the videos so you can see the water getting out.

[U.S. Water Rockets1]

The main question remains answered:

Is the FTC more efficient to eject water because the difference between the body diameter and the nozzle diameter is lower than the bottle one ?

It seems that there is always less leftover water inside an FTC compared to a bottle. Testing reveals that a small amount of water can be sprayed up the side of the rocket when the air pulse happens and the lower diameter makes the effect a lot less.