The value of streamlining

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Posted

Title says it all. Pretty eye opening

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Posted

Wow, a lot more than I expected!

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Posted

Great video, really opens,the eyes.

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Posted

Forward-facing flats are aerodynamic sin!

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Posted

damn.

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Posted

Cool!!! Great info! Now I know why a Breezy will just fall out of the sky when you pull the throttle back!!!

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Posted

Spend a few pounds on streamlining and lower your throttle setting for the same airspeed, save a gallon an hour and increase your endurance by an hour or 2. 

So 2 or 3 lbs = 20-30 lbs of gas that you don't have to carry. 

I made it to the Kitfox factory flyin last month and talked to Lowell Fitt and saw his beautiful KF4 which has a lot of aerodynamic mods and that is basically his philosophy. 

20190823_195258.jpg

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Posted

Interesting to note that he is not using their Hatz style bush gear but running shocks.  I went to the Roberts Rage gear struts which uses a combination of shocks,  bungees and gear legs of my own design and have been very pleased.  No more bent up fuselage.

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Posted (edited)

Interesting to note that he is not using their Hatz style bush gear but running shocks.  I went to the Roberts Rage gear struts which uses a combination of shocks,  bungees and gear legs of my own design and have been very pleased.  No more bent up fuselage.

Actually, I don't think there are any damping shocks there. Amazingly enough that's the only pic I took at the whole event. I should have documented that plane from top to bottom because it was obviously built by a master but I was busy talking to him, then it was time for dinner then it got dark. I didn't make it the second day.

But pretty sure those are just dual coil springs over a tube to keep them straight.

 

edit 

btw I'd like to see pictures of your setup

Edited by Willja67

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Posted

Looking closer I do see the springs, still very different from what they were marketing under Highwing LLC.

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Posted

Ok so what do I do about the cross wires on my floats?  How would you get an airfoil shape on a 1/8" wire?

I assume something as simple as doubling gorilla tape over it (wire is the leading edge with a "tail" of tape behind) might get a bit of airfoil shape but would probably flutter and cause more problems than it solves?

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Posted

Ok so what do I do about the cross wires on my floats?  How would you get an airfoil shape on a 1/8" wire?

I assume something as simple as doubling gorilla tape over it (wire is the leading edge with a "tail" of tape behind) might get a bit of airfoil shape but would probably flutter and cause more problems than it solves?

Your on floats.... your not flying a Ferrari to begin with.  You have 2 options.  Fly your overpowered beast and love it the way it is or spend some money on SS streamline rigging from something like a tcrate on 1320s.  

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Posted

Haha!  Yeah I am not the guy to make rocket science out of stuff but when I learned (from this video) that those tiny 1/8 wires are causing as much drag as the expensive streamline struts and spreaders I bought then I wondered if there was a simple way to help em "go with the flow" a little better.

First though I better tackle my round tube lift struts that are dragging as much as 10" cross sectional streamline would!  :o

Then I'm doin the jury struts with R/C aileron balsa...

Oh yeah, and then fair that brick of a belly radiator...

Then it'll be a Ferrari, damnit!

:lmao:

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Posted

Haha!  Yeah I am not the guy to make rocket science out of stuff but when I learned (from this video) that those tiny 1/8 wires are causing as much drag as the expensive streamline struts and spreaders I bought then I wondered if there was a simple way to help em "go with the flow" a little better.

First though I better tackle my round tube lift struts that are dragging as much as 10" cross sectional streamline would!  :o

Then I'm doin the jury struts with R/C aileron balsa...

Oh yeah, and then fair that brick of a belly radiator...

Then it'll be a Ferrari, damnit!

:lmao:

the aluminum trailing edge works great on the jury and tail struts.  snaps right on then you can cover as needed or a quick strip of tape works too.  If you are going to be on floats, I am not a big fan of wood touching any part of the strut... lots of pics and documentation on that in the forum.  Wet wood and metal don't mix for shit.

I picked up a hand full of rear struts for a cub that had been replaced with sealed struts.  Most shops will give them way.  This is what I will be making my struts from soon for the Avid.  

The air under the belly is pretty dirty to begin with so I am not sure how much fairing it in will get ya but it might be worth it to try!  Fair in the strut attach points and gas caps while your at it!

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Posted

Ok so what do I do about the cross wires on my floats?  How would you get an airfoil shape on a 1/8" wire?

I assume something as simple as doubling gorilla tape over it (wire is the leading edge with a "tail" of tape behind) might get a bit of airfoil shape but would probably flutter and cause more problems than it solves?

There was a company that made plastic snap on aerodynamic strips for streamlining wires for hang gliders. I don't know if the stuff is around or who makes it but it's worth a look. I think I seen it in a Glider Rider magazine decades ago.

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Posted

Good thinking!  Here's what a quick search came up with.  I'll keep digging.

https://deepwaterbuoyancy.com/product/mooring-line-cable-fairing/

 

There was a company that made plastic snap on aerodynamic strips for streamlining wires for hang gliders. I don't know if the stuff is around or who makes it but it's worth a look. I think I seen it in a Glider Rider magazine decades ago.

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Posted

Thanks!   I emailed them to see if they can produce some in small dia sizes.   Might work good too on the wires that support the horizontal and vertical stab on some planes.

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Posted

Lowell Fitt produces some vacuum bagged fiberglass fairings for the jury struts and tail struts. He said he'd sell me enough for my plane for about $100.

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Posted (edited)

I wonder where one might find solid bladed wire?  Some biplanes have it.  Lots of road bikes use bladed spokes.

On the belly radiator - Its drag, or thru-flow pressure drop causes much air to flow around it instead of through.  The lower-momentum air right behind in its wake does help mitigate the drag of those un-faired, circular-cylinder landing gear struts tucked up against the belly, though.  Those who have IVO props must be aware that the blade angle goes to zero approaching the hub.  This is draggy, and certainly doesn't help in producing thrust.  But again, although the inboard roughly 1/3 of radius almost certainly creates drag, not thrust, it does reduce airflow velocities near the fuselage, helping to lessen the drags of other little nasties downstream, like those lovely lower strut attachments/fold hinges, the belly rad, etc..

Many years ago I was at family day at MacDonnell Douglas, and spotted a little oil radiator standing there naked in the fan duct of a DC-10's engine, downstream of the fan.  I was appalled, but wondered if its lack of a cowling meant that achieving a drag reduction by cowling a radiator is not an easy task, and that just designing something that looks "right" might yield a drag increase or no reduction at all, with a weight penalty to boot.  A-priori intuition can be misleading in the aerodynamics world.  Data talks and theory walks.  There's lots of good stuff in Hoerner, for starters.

 

 

Edited by Turbo
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Posted

I wonder where one might find solid bladed wire?  Some biplanes have it.  Lots of road bikes use bladed spokes.

On the belly radiator - Its drag, or thru-flow pressure drop causes much air to flow around it instead of through.  The lower-momentum air right behind in its wake does help mitigate the drag of those un-faired, circular-cylinder landing gear struts tucked up against the belly, though.  Those who have IVO props must be aware that the blade angle goes to zero approaching the hub.  This is draggy, and certainly doesn't help in producing thrust.  But again, although the inboard roughly 1/3 of radius almost certainly creates drag, not thrust, it does reduce airflow velocities near the fuselage, helping to lessen the drags of other little nasties downstream, like those lovely lower strut attachments/fold hinges, the belly rad, etc..

Many years ago I was at family day at MacDonnell Douglas, and spotted a little oil radiator standing there naked in the fan duct of a DC-10's engine, downstream of the fan.  I was appalled, but wondered if its lack of a cowling meant that achieving a drag reduction by cowling a radiator is not an easy task, and that just designing something that looks "right" might yield a drag increase or no reduction at all, with a weight penalty to boot.  A-priori intuition can be misleading in the aerodynamics world.  Data talks and theory walks.  There's lots of good stuff in Hoerner, for starters.

 

 

Funny Turbo but they still do that cooler thingy on the newest jet engines.

Here's from my walkaround today on a 2018 model CFM56.

If that brick is good enough for 800+ mph flow inside a jet engine then I'm feeling better about my Kitfox belly radiator LOL

 

2019-10-03 13.22.51.png

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Posted

Coll blimey mate!  Ugly or what?  You'd think they'd put some serious effort into finding another way, or enginerring the sh--t out of some kind of cowling!  Looks like that radiator even has the dreaded forward-facing flats, if the backside is any indication!  But note: the flow velocities are relatively low there, and don't really ramp up until the exit nozzle contraction, where it goes through sonic.  Typically the fan flow continues accelerating externally over the core cowl to low supersonic.

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