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  #11  
Old 10-03-2021, 07:31 PM
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bjdecker bjdecker is offline
 
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Originally Posted by scsmith View Post
The reverse bend that you now have to facilitate mounting with the Adel clamps is not so good.
Can do! I already had to "notch" it to clear the throttle cable -- removing the material between the adel clamps shouldn't be an issue, aside from the hazards associated with working with stainless steel :/

The 1 or 2 degree delta in the CHTs was probably caused by an increase in the OAT during the test (Morning vs Afternoon) down here in He-double-L's front porch.
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Last edited by bjdecker : 10-03-2021 at 07:33 PM.
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  #12  
Old 10-03-2021, 08:04 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Just wondering - would this also provide a heat or maybe even flame shield to the bottom of the firewall and floor?
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  #13  
Old 10-03-2021, 08:15 PM
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Originally Posted by scsmith View Post
You can accelerate flow happily around a fairly tight radius.
Steve, What would you consider to be a optimum radius in this firewall application?
Thanks
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  #14  
Old 10-04-2021, 09:17 AM
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Quote:
Originally Posted by scsmith View Post
Making it 'longer' is not really necessary. You can accelerate flow happily around a fairly tight radius. Extra length adds more surface skin friction drag without really doing anything beneficial.
Steve point out this detail in a PM long ago, and I've tried to pass it along. Please note I kept the big internal trumpet seen in posts 4 and 7 because it created a low pressure termination (less than lower cowl pressure) for the ducted oil cooler, which increases cooler deltaP.

Quote:
The reverse bend that you now have to facilitate mounting with the Adel clamps is not so good. The goal is to create a smooth ramp for acceleration, like a trumpet bell. If anything, you would like to roll a small lip on the edge that goes back the other way.
I've added a sketch below for those who may not entirely follow what Steve is describing. Reverse bend on left, not so good. Two examples of rolled lip on right. Large radius lip notched for mount tubes is probably best. If interested in fire protection or floor heat reduction, a stainless steel panel could be extended over fiberfrax felt.
.
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  #15  
Old 10-04-2021, 11:04 AM
scsmith scsmith is offline
 
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Quote:
Originally Posted by dpansier View Post
Steve, What would you consider to be a optimum radius in this firewall application?
Thanks
It would be difficult to identify any kind of optimum. Too small a radius and the flow may still separate. That depends on a lot of details, such as the distribution of incoming flow. Too big a radius and you have a lot of wetted area that is just friction drag. My instinct is that the radius on the standard RV-8 installation is close to the minimum that should be used. The shape in Dan's sketches looks really good to my eye.

Note also that Dan's installation has side panels too.
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  #16  
Old 10-05-2021, 04:49 PM
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Default Radiused...

Bent the "leading" edge over --- now, I think I'll remake the whole darn thing and roll the edge end-to-end.
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  #17  
Old 10-05-2021, 05:08 PM
crabandy crabandy is offline
 
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Getting rid of the reverse bend for a radius makes so much sense, if I ever take mine off Iíll make a new one with the rolled upper edge.
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  #18  
Old 10-05-2021, 05:45 PM
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Quote:
Originally Posted by bjdecker View Post
Bent the "leading" edge over --- now, I think I'll remake the whole darn thing and roll the edge end-to-end.
While you're in there, get rid of the transverse rubber hose, hose clamps, etc. Maybe just relocate it well forward, out of the exit flow.
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  #19  
Old 10-05-2021, 05:52 PM
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Originally Posted by DanH View Post
While you're in there, get rid of the transverse rubber hose, hose clamps, etc. Maybe just relocate it well forward, out of the exit flow.
Gotcha -- I would need to engineer a new exhaust hangar "system"; round cross sections perpendicular to flow are-the-worst drag-wise. Maybe I can find a tear drop shape and use it for the transverse mount/isolation. NACA 0024 would suffice...
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Last edited by bjdecker : 10-05-2021 at 05:58 PM.
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  #20  
Old 10-05-2021, 05:54 PM
Kyle Boatright Kyle Boatright is online now
 
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Quote:
Originally Posted by bjdecker View Post
Gotcha -- I would need to engineer a new exhaust hangar "system"; round cross sections perpendicular to flow are-the-worst drag-wise...
Check the link I posted earlier in the thread. There's a picture on that page which shows how to eliminate that hose.
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