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Very Hot Topic (More than 25 Replies) Let's Build a Paradigm (Read 13557 times)
Michael Heinrich
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Re: Let's Build a Paradigm
Reply #28 - May 9th, 2011 at 5:21pm
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   Interesting stuff. --Who's this Hudsonduster dude, he sounds like he's ripping ME off!
   Three years hence, the four pages of this thread are a really pleasant bit of nostalgia; and a good dicussion, giving a real overview of the tangled dynamic in the sometimes-contradictory tenets we press into our service. --As THIS thread is, in a complementary way.
   Pretty cool, bumping this up. Thanks.
   Michael
  
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Sky9pilot
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Re: Let's Build a Paradigm
Reply #27 - May 9th, 2011 at 9:17am
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Thanks Bargle....that link worked for me.

Tom
  

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Bargle
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Re: Let's Build a Paradigm
Reply #26 - May 8th, 2011 at 8:30pm
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I think the old link is just outdated.
Try this one.
http://www.smallflyingartsforum.com/YaBB.pl?num=1210338579/0
  

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thymekiller
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Re: Let's Build a Paradigm
Reply #25 - Sep 16th, 2008 at 10:27pm
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Small world. I had that saved in my refrence file. I need to go through that file. I have several articules that I was going to read later but I havent gotten back to some of them. 
The sfa thread grew since I saved the link. Its a good thread. I have saved a few on airfoils and a few on props, ect, but I havent got to props yet. Looks like I will soon. If there is anything of note I will post it here.

eric
  

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HudsonDuster
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Re: Let's Build a Paradigm
Reply #24 - Sep 16th, 2008 at 6:19pm
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A friend on SFA reminded me of the discussion over there-- (LINK NOLONGER AVAILABLE-Moderator)-- and it nicely dovetails into what we're saying over here on this thread. Worth reading through.
  M
« Last Edit: Oct 27th, 2011 at 11:56am by Sky9pilot »  

Michael J. Heinrich

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thymekiller
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Re: Let's Build a Paradigm
Reply #23 - Sep 14th, 2008 at 9:01pm
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Thank you Tim. I'v been ignoreing everybody.  Sorry to all any and all. I might make some wild claims, but smart ain't one of them.... Grin Grin

eric
  

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Tim the Inspector
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Re: Let's Build a Paradigm
Reply #22 - Sep 14th, 2008 at 8:27pm
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TK,

Go to your User Panel (it's in the bar just under the Stick and Tissue banner at the top of the page).  From the user panel select "Profile" and from there click on "PM Preferences."  It'll ask you to confirm your password then it will show you your "Ignore list" among a few other things.  FWIW, the ignore list exists to ditch PM's from people who typically harass you or you otherwise don't want to hear from.

-Tim

p.s. No one's on my ignore list (yes, I'm assuming I'm both a friend and worthy of compliment).
  
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thymekiller
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Re: Let's Build a Paradigm
Reply #21 - Sep 14th, 2008 at 8:18pm
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Whats a pm setting. Dont mean to be dumb, but.... What should they be set at and how do I set them. I did not know there was an ingnore setting.

eric
  

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HudsonDuster
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Re: Let's Build a Paradigm
Reply #20 - Sep 14th, 2008 at 6:50pm
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   Okay, reality check: could some of you frequent guys please look at your PM settings? I wrote a compliment to one fellow I think of as a friend, and got bounced as on his "ignore" list. He'll know who he is, if this was in error. Kinda would hope so. If not-well, can't be helped. But just checking.
   M
  

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thymekiller
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Re: Let's Build a Paradigm
Reply #19 - Sep 9th, 2008 at 11:27pm
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Thanks. That helps put some things in perspective.

Panache. 3 blades do look better on some models. Soon I will take a shot at my first 2 blade.

eric
  

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C.L. Chennault
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Re: Let's Build a Paradigm
Reply #18 - Sep 9th, 2008 at 8:04pm
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Good stuff Michael,

Don't forget the big advantage of three and four bladed props.  Panache. Cheesy

John
  

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HudsonDuster
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Re: Let's Build a Paradigm
Reply #17 - Sep 9th, 2008 at 6:14pm
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thymekiller wrote on Sep 9th, 2008 at 12:17am:
Lets try another one about prop size. what is the minimum size [percentage wise]for a scale plane.
   Prevailing wisdom is, one-quarter wingspan min, one-third reasonable maximum.
   Contest winners have put enormous props on scale models, half and more the wingspan. They win contests. When you learn how your model flies and how to make it scream straight up, you will look at big props too.
   Re-read what I said earlier about low-pitch props on draggy models.
Quote:
I guess this changes if there is more than 2 blades.  If I want a 3 blade prop  is there a general rule of thumb for dia. and pitch as compared to a 2 blade?
   It does change. Guys lately have written much about how multi-blade props are just as good since they can create more lift with available power than two-bladers. Great, but rubber power is a finite energy-return system, necessarily slow-turning; and more power also means more friction in the shaft and bearings, a point which most guys don't mention. Again, finite.
   And it hasn't been proven to this curmudgeon that a multi-blade prop gets out of its own cavitation enough to show its advantage over a two-paddle.
   By far, most winners in every event are using two-blade props. Again, get your skills well in hand and then you may do your own experiments. Basics first.
   Michael
   
  

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thymekiller
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Re: Let's Build a Paradigm
Reply #16 - Sep 9th, 2008 at 12:17am
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Thanks guys thats exactly what I was looking for.  Lets try another one about prop size.
what is the minamum size [percentage wise]for a scale plane. I guess this changes if there is more than 2 blades.  If I want a 3 blade prop  is there a general rule of thumb for dia. and pitch as compared to a 2 blade?
Remember, we are still using a rubber powered hi-wing as a standard for comparsion. I believe that things change a little for different setups.

Thanks for mentioning the thrust line in relation to down thrust. I hadnt thought about that. I forgot that thrust line isnt always simply the center of the fuse. Guessing at that.

eric
  

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HudsonDuster
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Re: Let's Build a Paradigm
Reply #15 - Sep 7th, 2008 at 5:49am
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   Tim's got it. My starting numbers for scale (I'm assuming you meant "if a person wasn't building deadnutsEXACT scale?") are just that, stab 25% wing area/fin 12%, dihedral 1" per foot span PER SIDE, incidence wing 3deg. stab zero. Washout at least 1/16" per foot, both wings, more with taper. Prop no bigger than one-third to start.
   Others vary from these numbers a little; some set the wing incidence different for high to low wings for instance but I don't, although you can lose dihedral as the wing goes up--think 3/4" per foot per side at shoulder, 3/8" for high, maybe nothing for parasol. Just keep tips above thrustline (including downthrust).
   Starting with these numbers gets you pretty much a guaranteed flyer, then you can tweak each airframe based on what you see with this.
   When you figure area, include what's inside the fuselage. It counts. For fins too--sort of fudge a line dropping down the side view and add it to the fin area calculation. I get fancy and make my line sort of mirrored to the angle of the fin's leading edge, or further back towards the rudderpost. See how it looks and make my best guess.
   Michael
  

Michael J. Heinrich

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Tim the Inspector
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Re: Let's Build a Paradigm
Reply #14 - Sep 6th, 2008 at 10:31pm
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Sorry Eric, life's not that easy.  Personally, I like the stab to be about one quarter of your wing area and your rudder should be about half of that.  Unfortunately as you scale down below a sixteen inch wingspan or so, aerodynamics get funny (Hudson Duster has often said 'a small model never flies out of its own turbulence') and your tail surfaces could stand to be even bigger than that.  Of course, the distance between your wing and tail can and will make a difference as will the side area and width of the fuselage in front of and behind the centre of gravity.  Complex stuff.

As for propellers, on a high wing I like to go with somewhere between one quarter and one third of the wingspan but others may argue.

Hope this makes it all clear as mud.

-Tim
  
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