cd vs wetted area

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flyingwombat
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Joined: Thu Sep 07, 2006 7:08 pm

cd vs wetted area

Post by flyingwombat »

Hi Guys
any budding aero engineers want to comment??

In the chase for the best cd, where is the point where
added wetted area loses you more than you gain on cd changes

eg you could build a 70 foot long streamliner with a cd of .1
but a laymans guess is that it would be less efficient than a 30 footer
with a cd of .2.. this may be total crap lol

ps I hope me wanting to be an ameteur aero engineer doesnt get me
into as much trouble as wanting to be an ameteur gynocologist when
I was 15.

pps yeah, I know I should research this myself but, hey the boards
have been quiet for a while and we may get some great ideas flowing
hawkwind racing
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Post by hawkwind racing »

my understanding of what you are refering to is a type of drag called 'skin friction' it is mostly not a concern for the majority of us , its effects are most pronounced with very low Cd vehicles that go very very fast , like 350+++ in this case skin friction is equal to or greater than form drag , yes the greater the wetted area the larger the friction drag ,for us bottom feeders , form drag is our major concern
cheers
Gary
flyingwombat
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Post by flyingwombat »

thanks

Dont think i will be quite that fast lol
DLRA
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Post by DLRA »

hawkwind racing wrote:in this case skin friction is equal to or greater than form drag ,


Why did I think of Bob Ellis when you were talking about this...........
Keep the shiney side up........
DLRA WebMaster / Editor
Dr Goggles
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Location: Right behind you Chief !

1/4 mile dress-ups , Bob's yr uncle

Post by Dr Goggles »

DLRA wrote:
hawkwind racing wrote:in this case skin friction is equal to or greater than form drag ,


Why did I think of Bob Ellis when you were talking about this...........


Jeez get off his back he's just trying to express his inner feelings, you know Chev in a Ford ....Bloke in a dress...........oh oh Goggles in a pickle!!!

:lol: :lol: :lol:
...few understand what I'm trying to do , but they vastly outnumber those who understand why..
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BOB ELLIS
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Post by BOB ELLIS »

Goggles in a pickle? How ya gunna get thru scrut? Now you're in a pickle!WHO CARES. i look better in drag than you anyway (don't know about our beloved webmaster tho , he may look pretty good!!) Cheers ,Bob. #66 C/GCC.
Dr Goggles
Posts: 1315
Joined: Tue Jul 05, 2005 11:23 pm
Location: Right behind you Chief !

Schumacher

Post by Dr Goggles »

BOB ELLIS wrote:Goggles in a pickle? How ya gunna get thru scrut? Now you're in a pickle!WHO CARES. i look better in drag than you anyway (don't know about our beloved webmaster tho , he may look pretty good!!) Cheers ,Bob. #66 C/GCC.


I figured you'd just be making up a pair of "just add water" concrete boots for me to put on Bob....... :shock:

now , about gettin' thru scrut'.....I'm going to the fatherland in a fortnight Bob(and the N Island too) so can I pick you up a bribe? :wink:
...few understand what I'm trying to do , but they vastly outnumber those who understand why..
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