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General control line discussion => Open Forum => Topic started by: peabody on December 08, 2016, 07:00:50 AM

Title: Chord v. span and area sq.
Post by: peabody on December 08, 2016, 07:00:50 AM
As I uncover my toy aeroplane stuff from hibernation, I came upon a wing core set that was for a tuna piped model (.60 size).

I am wondering about shortening the cores to suit an LA 46 powered model.

Should I shorten the cores at the tip, which will yield deeper chord and, essentially, thicker tips?

Or should I shorten the center sections?

I'm thinking of lopping two inches from each, changing overall span from 56" to 52"

Thanks
Title: Re: Chord v. span and area sq.
Post by: Motorman on December 08, 2016, 07:06:53 AM
Take a little off the center and a little off the tips.


MM
Title: Re: Chord v. span and area sq.
Post by: Dave_Trible on December 08, 2016, 07:19:34 AM
Rich I doubt it will matter hugely.  Actually 56" is in the ballpark of many of the .46 era airplanes so if the airplane is light enough you wouldn't really need to cut.  If you are to cut I guess I'd whack the center to get the biggest bang for the buck taking out the larger lift section and not increasing drag out at the tips.

Dave
Title: Re: Chord v. span and area sq.
Post by: peabody on December 08, 2016, 07:32:50 AM
Thanks Dave....that's the direction I was thinking....the measurements are pre-tip....I think most spans include tips? Per plan the tips add four inches to the span.

I was planning on minimal tips....flat, ala Brett, with rounded edges, although I have been toying with the idea of using 3/4" inboard and 1/4" outboard...

Have fun!
Title: Re: Chord v. span and area sq.
Post by: Howard Rush on December 08, 2016, 10:43:51 AM
Depends on whether the wings you have have too much aspect ratio or too little.
Title: Re: Chord v. span and area sq.
Post by: Tim Wescott on December 08, 2016, 11:39:00 AM
Whacking off the tips will decrease the aspect ratio.  Whacking off the roots will decrease it less.  I'd whack off the roots, if anything.

My hand-me-down Atlantis weighs 64 ounces, has 700 square inches of area, and from what little I've had a chance to fly it, does quite well on a 46LA.  Smaller prop = more power; I have an APC 11.5x4 on it that's been cut down to 11.25x4.
Title: Re: Chord v. span and area sq.
Post by: Ted Fancher on December 08, 2016, 03:36:45 PM
Depends on whether the wings you have have too much aspect ratio or too little.

What Howie said!  Assuming the wing was originally in the neighborhood of 5 to one AR (including the planned flaps) the change in aspect ratio will be more of a problem than the reduction of the wing's span will be an asset.  IOW, the increased drag per unit of lift while maneuvering will be a greater thief of thrust than the reduction of span will be an improvement.  Not insurmountable but worthy of consideration.

Ted
Title: Re: Chord v. span and area sq.
Post by: Randy Cuberly on December 08, 2016, 05:40:31 PM
Leave it alone and use a bigger engine!!!

Makes for a more harmonious outcome!   LL~

Randy Cuberly
Title: Re: Chord v. span and area sq.
Post by: RandySmith on December 11, 2016, 01:13:22 AM
Rich 
Cut 1 inch off the  root, and 1 inch off the  tips

Randy
Title: Re: Chord v. span and area sq.
Post by: Air Ministry . on December 11, 2016, 08:17:11 PM
A Genisis 46 is 60 span & has a .40 in it .  S?P
Was gunna puton a pic of a Hallmark , as its a minimilist .46 THING , 58 span .

But , Square Tips & you wouldnt really need to loose any span if its for moderate conditions , not wild winds .
If your in a high Alt. or Hot area it may even be a help !

(http://stunthanger.com/smf/open-forum/f-105-thunderchief/?action=dlattach;attach=49812)

Some Blokes did a Hunt Wing trike gear sidewinder engine , profile nose & inbd doubler with spinner  exposed tank out.
a tapered box aft about chord depth Sq , a dorsal strake , fin & a Canopy . About the minimilist you could get ,
bar the trike gear - which'd be a asset , as your less likely to knock the nose off .

It looked vaugely like this , but a bit simpler . Clean Lines & the minimilism meant the weight was , too .

Power to Weight ismore relevant and a .46 should haul the coal full span , if its Clean .