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CARF Ultra Flash Evo build thread +

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CARF Ultra Flash Evo build thread +

Old 11-11-2021, 08:08 AM
  #176  
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Originally Posted by Canadian Man View Post
David, Depending on when you come up I will have one here as well!
Fantastic Jonathan…. What scheme are you getting…. And which Swiwim size turbine ?


Old 11-11-2021, 11:01 AM
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Originally Posted by LA jetguy View Post
Fantastic Jonathan…. What scheme are you getting…. And which Swiwim size turbine ?
It's eventual home is to one of my customers in the US. It's the scale scheme. Getting a Swiwin 240.
Old 11-11-2021, 11:46 AM
  #178  
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Originally Posted by Canadian Man View Post
It's eventual home is to one of my customers in the US. It's the scale scheme. Getting a Swiwin 240.
Perfect.. look forward to seeing it when I come over...
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Old 11-17-2021, 03:07 PM
  #179  
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Default Thrust tube + heat

Thrust tube + heat

I was worrying about nothing.
Did a little test run today with the Aerodesignworks B140F turbine today: the outer tube stays absolutely cold to the touch as long as the turbine is running.

It gets a little warm during shutdown and cooling, because of the reduced venturi effect at the rear.

I doubt I need the NACA inlets without the full bypass in the EVO.
I may test the temps at the rear with the wing and stab installed, but I doubt it's needed.

Gotta love the way this turbine runs! The Aerodesignworks B140F is one rev-happy unit!
Under 3 seconds from dead idle to full power, without any discernable flames and without overshooting target rpm.
Absolutely stable.
Old 11-17-2021, 09:56 PM
  #180  
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There is a reason why things are done…you do need the Ducts, this former means there is no airflow into the cool wall front opening without them.




Old 11-18-2021, 02:24 AM
  #181  
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I figured that's what the four holes in the former are for.



The Evo manual makes no mention of extra cooling for the rear end of the fuselage.
I suppose the current manual is kinda written for people who have put together Classic Flash and pre-Evo Ultra Flash airframes in the past, as it is rather skinny IMO.
I'm not a "seasoned" jet flier, so I tend to (over)think about everything 😋

I did find a manual on the internet for the pre-Evo ultra flashes, that does mention the NACA ducts.
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Old 11-18-2021, 11:30 AM
  #182  
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Cables, they have always been there, but they are not large enough and probably just feed warm air from the turbine area.
If I get time while I’m in Scotland shortly I’ll write some more info. The idea was always to use the original manual in conjunction with the Evo reference

Dave
Old 12-06-2021, 02:03 PM
  #183  
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Hey guys would you trim back this plastic little bit that’s hanging beyond the end of the thrust tube? I would rather do it now then wait till it’s a gooey melted plastic glob. I can’t imagine it gets that hot right there that it would but just a thought.


Last edited by 737Driver; 12-06-2021 at 05:34 PM.
Old 12-06-2021, 02:05 PM
  #184  
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Red circled part

Old 12-06-2021, 02:58 PM
  #185  
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I would trim it off. You will lose less thrust
Old 12-06-2021, 03:31 PM
  #186  
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Originally Posted by Dave Wilshere View Post
I would trim it off. You will lose less thrust
Will it make a noticeable difference? Just wondering. Thx!
Old 12-06-2021, 10:02 PM
  #187  
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When you have a large difference in the two tube lengths you don’t get a clean exit of the gasses. It’s a small difference, but it is there.
My first Bandit ended up with a huge difference between the two pipes and it only came alive when I changed the inner tube to one 12mm longer.
Old 12-07-2021, 08:29 AM
  #188  
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If you have too much overhang, it will start to move huge amounts of air between the inner and outer tube.

A guy in Germany does a lot of testing and makes YT videos about it.
So he tried to measure the airflow in a double wall tube: with a 10mm overhang at the back, there was just over 40 km/h airflow between the tubes. With an overhang of 20mm, this jumped to over 110 km/h (this is quite a lot of air being moved).

It won't get hot though, not at that short distance. The inner hot flow will not mix with the outer flow enough in that distance.
Old 12-07-2021, 08:54 AM
  #189  
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Originally Posted by Dave Wilshere View Post
When you have a large difference in the two tube lengths you don’t get a clean exit of the gasses. It’s a small difference, but it is there.
My first Bandit ended up with a huge difference between the two pipes and it only came alive when I changed the inner tube to one 12mm longer.
Originally Posted by Rudeboy View Post
If you have too much overhang, it will start to move huge amounts of air between the inner and outer tube.

A guy in Germany does a lot of testing and makes YT videos about it.
So he tried to measure the airflow in a double wall tube: with a 10mm overhang at the back, there was just over 40 km/h airflow between the tubes. With an overhang of 20mm, this jumped to over 110 km/h (this is quite a lot of air being moved).

It won't get hot though, not at that short distance. The inner hot flow will not mix with the outer flow enough in that distance.
That’s really interesting and I never thought about it. Thanks!
Old 12-07-2021, 09:50 AM
  #190  
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It makes lots of drag, that’s the point, the distance does vary with pipe-cool wall gap, but 8-10mm is what aim for.
Old 12-07-2021, 11:11 AM
  #191  
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Just move the trust tube to the rear till flush with the end cone
Old 12-07-2021, 12:24 PM
  #192  
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It’s bolted in place!
Old 12-07-2021, 12:56 PM
  #193  
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I switched my order for a Rebel Classic to a Ultra Flash EVO.
How long has this model and its other variants been around?
I know a few people that have had several. One fellow told me he went through more than a dozen over the years. I guess people get them and then sell or wreck them and end up getting another because they miss it.
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Old 12-07-2021, 01:19 PM
  #194  
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First Ultra Flash was 2010.
There are over 1000 out there. I’ve flown over 50 in the last 11 years, I think I’ve built nine including four of my own-all around it’s just about the best sport jet ever. Len’s issues don’t seem to exist here…
Old 12-07-2021, 01:51 PM
  #195  
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You could shorten the fiberglass tailcone to get the 8-10mm of space so as not to create turbulence and drag of the air swirling around the exhaust gases.
A steady hand and fiber cutting wheel on the dremel and sand to sand it smooth. I had to do this with my Viper
Old 12-07-2021, 02:31 PM
  #196  
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Originally Posted by Dave Wilshere View Post
First Ultra Flash was 2010.
There are over 1000 out there. I’ve flown over 50 in the last 11 years, I think I’ve built nine including four of my own-all around it’s just about the best sport jet ever. Len’s issues don’t seem to exist here…
Who is Len?
Old 12-07-2021, 03:10 PM
  #197  
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Originally Posted by scoeroo View Post
Just move the trust tube to the rear till flush with the end cone

that would require the bell mouth to be to far aft of the former that it’s screwed into. I thought about re-riveting the bell mouth on the thrust tube, but there is zero material to work with that is extra. That bell mouth is mounted on the very end of the thrust tube. You would think they could make the thrust tube longer!

Old 12-07-2021, 03:13 PM
  #198  
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Skunkwrks

most likely gonna do that.
Old 12-07-2021, 10:51 PM
  #199  
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Originally Posted by jvaliensi View Post
I switched my order for a Rebel Classic to a Ultra Flash EVO.
How long has this model and its other variants been around?
I know a few people that have had several. One fellow told me he went through more than a dozen over the years. I guess people get them and then sell or wreck them and end up getting another because they miss it.

I’m enjoying my new Ultra Flash evo…. Hope you got to see it at the field…. I went small on the power plant (M122NG) and it’s more relaxing. I’m sure with the new X180 it will be a different jet…. 😜





David
Old 12-08-2021, 07:56 AM
  #200  
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David,

I put a Jet Central Lynx, 130N, in mine as well. Still hit 202 mph which is perfect. Lighter and a bit more relaxing for sure.



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