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Smoke nozzle placement.

Old 05-17-2022, 06:59 PM
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BDK74
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Default Smoke nozzle placement.

Hi all. Installing a smoke system in my Ultra Flash. Iíve put smoke systems in lots of my piston planes but this will be first install in a jet.

Where would be the best placement for the nozzle? A bit behind the turbine or would it work at the end of the tailpipe? I can easily do both but good smoke is my priority.

thanks!
Old 05-17-2022, 09:03 PM
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Dave Wilshere
 
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Just behind the turbine tailcone, depending on the smoke tube you are using the end needs to be inside the turbine tail pipe cone dia by around 10mm and spray across the efflux.
Old 05-18-2022, 05:14 AM
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dr.tom
 
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We all heard/seen many models with different placements...
but Lighter side of RC made a video just about that and he concludes (in comments below) that right after turbine gives best smoke, thats why he went for that way in video.

Old 05-18-2022, 05:43 AM
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BDK74
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Thanks all!
Old 05-18-2022, 02:31 PM
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Desertlakesflying
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Originally Posted by BDK74 View Post
Hi all. Installing a smoke system in my Ultra Flash. Iíve put smoke systems in lots of my piston planes but this will be first install in a jet.

Where would be the best placement for the nozzle? A bit behind the turbine or would it work at the end of the tailpipe? I can easily do both but good smoke is my priority.

thanks!
Put it out of the back of the airplane
Old 05-18-2022, 03:53 PM
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Viper1GJ
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I've done it both ways on several jets. Pros and Cons for both ways. Just some of my observations below:

Right behind the turbine is hotter and gets better smoke most of the time especially at or near idle power. It is possible to torch the fluid if especially if you are spooling up the turbine when turning on the smoke. Fluid is more likely to spill, drip, or leak inside the fuse if you have a accident or malfunction.

Out the back of the tail pipe gives good smoke as long is it is hot enough to vaporize the fluid. However, several times I've seen smoke density drop off as thrust is reduced toward idle and almost no smoke at idle even though the fluid is spraying out into the exhaust stream. Running the smoke tube between the walls of the pipe is a great way to preheat the fluid. Having the smoke nozzle at the rear eliminates the possible mess inside since all the fluid is sprayed behind the fuse unless there is an internal malfunction.

I always drill weep holes usually before and aft of each former where any fluid that may spill inside can drain out and not puddle. Seen a couple of bad fires after some puddled fuel got lit after a bad start. Just my two cents worth.
Gary

Last edited by Viper1GJ; 05-18-2022 at 03:55 PM.
Old 05-19-2022, 01:11 PM
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BDK74
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Thanks for the info. I’m going to start off with it in the rear. I’ve brazed an atomizing nozzle (bad dog smokes)on the end of a stainless tube so vaporization should be good, especially with the pre-heat.
The following 2 users liked this post by BDK74:
Desertlakesflying (05-19-2022), Viper1GJ (05-19-2022)

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