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Old Jan 21, 2013, 12:22 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
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At 0.5gms for the airframe you are definetly fitting right into the whole indoor building mind set. As I recall that is a very good figure for a model which isn't allowed to use rolled tubes and wing bracing. You're also setting up well for the next one if you're looking at the wood for the blades and thinking "I could go a LOT thinner and it'll still work".

One aspect is the method for locating the wing. "We" used to have, and likely still do, a method for generating a chart for a 0% margin of stability positioning for the wing. The exact method is really fuzzy since I did the last one something like 30 to 35 years back. But it is likely written up somewhere.

It allows you to locate the wing so that the balance point is technically at the neutral stability point. The model then relies on the high center of drag provided by the wing being mounted on the posts for pitch stability. This results in the model flying quite efficiently. To some extent it relies on having a motor in place so you need to pick a motor of roughly the size rubber you'll be using. For EZB's as I recall this is around .045 to ,050. Since the motor is such a big % of the total flying weight it needs to be there for the measurements to locate the wing.

If this is all old news for you then great. It may aid the next person.
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Old Jan 21, 2013, 12:44 PM
TheyreComingToTakeMeAway!
derk's Avatar
USA, ID, Coeur D'Alene
Joined Dec 2003
5,481 Posts
Thayer, i read through the rules, and there is no minimums on dimensions or weight. Max chord is 3in, span is 18in max, stab is no more than 50% total wing area.

So mine is a legal p-nut ezb lol

Bmatthews, i would like that calculation if you can find it. I'm not sure how stable this one is yet.
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Old Jan 21, 2013, 09:48 PM
more balsa please!
dcloin's Avatar
Princeton, In
Joined Jul 2007
793 Posts
Derk,

Thanks for sharing your EZB pics, it looks good. It's also nice to see some indoor duration posts. I'll keep watching for more.

Dcloin
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Old Jan 21, 2013, 10:12 PM
TheyreComingToTakeMeAway!
derk's Avatar
USA, ID, Coeur D'Alene
Joined Dec 2003
5,481 Posts
thanks, i have always loved indoor flying, and building has always seemed second nature to me (not always the best at it but always loved doing it)
after hearing about the free flight aspect of an upcoming event, i just got the nudge i needed to really get into it. next thing you know i'm looking at boron fiber and tungsten wires
though i know i am nowhere near ready to start using such things, thats something to look at in the future i guess.
i do however need to start collecting supplies if i am to continue down this slow floaty path


Bmatthews, i think i found an article talking about what you described: http://www.indoorduration.com/INAVPitchStability.htm
i will read through it and see if i need to alter my plane to help get good flight times.
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Old Jan 22, 2013, 01:39 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,600 Posts
Derk, that article discusses the WHY but not the HOW. I just tried about 10 minutes of online searching to see if I could find the HOW for models such as EZB's and other duration indoor models that use the usual tubes for wing posts. But I came up empty. Hopefully someone has the method for doing this at their fingertips and will post it for you/us.
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Old Jan 22, 2013, 10:05 PM
more balsa please!
dcloin's Avatar
Princeton, In
Joined Jul 2007
793 Posts
I bought some boron, can't have too many supplies. I only used it once, but figure some day.....
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Old Jan 22, 2013, 10:41 PM
Editor - Flying Models
United States, CT
Joined Aug 2003
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Quote:
Originally Posted by derk View Post
Thayer, i read through the rules, and there is no minimums on dimensions or weight. Max chord is 3in, span is 18in max, stab is no more than 50% total wing area.
That sounds a lot like what I remember. Nicely done. Looking forward to a flight report.
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Old Jan 23, 2013, 08:56 PM
Wonderfully Wicked
The Don's Avatar
Willoughby, Ohio
Joined Jan 2002
13,279 Posts
I can calc the CG location for you but will need some more dimensions. You already posted the wing and stab dimensions but I will need the following info.

1) Height of the wing post (looks about 2" from the photos)
2) Overall length of the model (looks about 11" from photo)
3) Distance from the trailing edge of the wing to the leading edge of the stab (looks about 4" from photo).

I am currently building an EZB, should weight about 260 mg. I have photos of my build over at hippocket.

Don
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Last edited by The Don; Jan 23, 2013 at 09:01 PM.
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Old Jan 24, 2013, 05:19 AM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
3,327 Posts
Don, If you'd ever care to do a Peanut or Dime Scale build thread, I'd be very interested.

I spoke too soon. You did!

http://www.hippocketaeronautics.com/...c,10972.0.html
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Old Jan 24, 2013, 11:01 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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I have two peanuts models I need to build. Hope to start them in the near future.

Don
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Old Jan 25, 2013, 05:19 AM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
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That's great Don. Looking forward to it. Any info on optimal rubber motor length/width and prop diameter/pitch would be helpful as well.
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Old Jan 25, 2013, 06:01 AM
TheyreComingToTakeMeAway!
derk's Avatar
USA, ID, Coeur D'Alene
Joined Dec 2003
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Quote:
Originally Posted by The Don View Post
I can calc the CG location for you but will need some more dimensions. You already posted the wing and stab dimensions but I will need the following info.

1) Height of the wing post (looks about 2" from the photos)
2) Overall length of the model (looks about 11" from photo)
3) Distance from the trailing edge of the wing to the leading edge of the stab (looks about 4" from photo).

I am currently building an EZB, should weight about 260 mg. I have photos of my build over at hippocket.

Don

here are some dimensions:
front of motor stick to wing leading edge 2"
front wing post 1.625"
rear wing post 1.375"
wing t.e. to stab l.e. 4.25"
overall length 11.25"
i probably have to much incidence on the wing, but might be able to change that with proper cg and decalage


i also built myself a prop pitch gauge, but then found out my first props rotation is backwards! i set up the gauge to normal rc props without looking at mine; DOH!
guess i should make another with the correct rotation, then i can get the wood thinner too.
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Old Jan 25, 2013, 10:08 AM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
3,097 Posts
The October 1976 issue of INAV has an article on CMOS or so I say (page 144 in BFIMA). I learned more about using CMOS after I did the book and it was relatively simple to calculate but I've forgotten all that now. Finding the C.G. of the plane with motor but no wing using the hang by a thread method and then putting the wing on so that the C.G. is at about 70% of the chord from the wing's leading edge is a good start. After testing the wing tubes can be moved (if they were put on with a reversible cement) to relocate the wing and fine tune the C.G. location.
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Old Jan 25, 2013, 07:04 PM
Wonderfully Wicked
The Don's Avatar
Willoughby, Ohio
Joined Jan 2002
13,279 Posts
I ran your model through my spreadsheet and you want the balance point with rubber to be 2" from the leading edge of the wing. This should allow you to remove most of the incidence in the wing.

Don
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Old Jan 27, 2013, 07:01 AM
more balsa please!
dcloin's Avatar
Princeton, In
Joined Jul 2007
793 Posts
I'll search around for that Oct 76 issue of INAV (indoor News and Views newsletter) and post it. Since the newsletter is currently out of print I see no harm or copyright issue. I have almost every of INAV in digital format and had been thinking of starting a thread and posting them for all to have access to, thoughts.....
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