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Old Apr 20, 2009, 06:11 AM
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spitfire_Doug's Avatar
Australia, WA, Carlisle North
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Homebuild

Hi all,

Im building a profile Autogyro and was interested in any helpfull tips you all might have. It is only a small model as shown in the pictures.

Thanks

Doug
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Old Apr 20, 2009, 06:46 AM
It was a GLITCH! Honestly!
SafeLandings's Avatar
Stourport on Severn ,Worcestershire, United Kingdom
Joined Dec 2007
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Doug,
Just keep it as light as you possibly can, try not over engineer things.......and make a bigger horizontal stab


Regards Rich
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Old Apr 20, 2009, 10:34 AM
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Australia, WA, Carlisle North
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Rich,

Current estimated mass is 500g (17.7oz) completed but Im still thinking on rotor(s) length. Will have a second look at the horizontal stabilizer.

Thanks
Doug
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Old Apr 20, 2009, 10:44 AM
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Doug,

around 17", I suppose.

Jochen
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Old Apr 20, 2009, 01:38 PM
Suck it and see
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Cromer, North Norfolk Coast, UK
Joined Aug 2008
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Hi Doug,

Can you give fuselage length as shown in pic. to get things into proportion.

Please keep the thread posted as to progress. Always good to see an original idea.

Good luck.

John
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Old Apr 20, 2009, 06:52 PM
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Australia, WA, Carlisle North
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Jochen and John,
I have some at 16" already but can make some new ones. The total length of the fuselage is only 500mm (19.6") including rudder. Everything is made overestimated so I can go back and fine tune later.

Is it ok to make the top part of te DC unit out of balsa or should I mechine one out of aluminium with a spindle turned onto it?

Thanks
Doug
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Old Apr 20, 2009, 07:18 PM
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Doug,

before you build nything new, try the 16" ones first.

No need for aluminium, but I wouldn't use balsa either. Have a look at the head I'm using for my 520 g Minimum:
http://www.rcgroups.com/forums/attac...mentid=1471302

Jochen
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Old Apr 20, 2009, 10:12 PM
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Jochen,

I couldnt replica your exact design shown due to lack of meterials but I have come up with something that should work fine.

Now I have to make the gearbox for it.
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Old Apr 21, 2009, 01:18 AM
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Update

Hi all,

Just some more pics of what Im up to. Neally ready for ground taxi and spin up tests.

Total mass is at 534g (18.8oz) with three 1" 1/2' aerobalsa blades at 16". Can someone help me with disk loading as Im a novice with rotorcraft equations?
I calculated it at 6.52 pounds per square foot(?). Please correct me.

Rich, no I havent changed the horizontal stab yet but Im onto it.

Thanks
Doug
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Old Apr 21, 2009, 01:41 AM
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Baden-Baden, Germany
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Hello Doug..........

Disc loading is calculated this:

mass-of-autogyro / rotor-disc-area

or:

mass-of-autogyro / (rotor-radius)≤ / PI

The disc-loading shall be in the region of 2 or 3 ounces per square-foot. The horizontal-stab-area shall be 4 % to 8 % of the rotor-disc-area, the vertical-stab-area about the half of the horizontal. Thats only a very rough idea, but as you have got big vertical and horizontal areas in front of the centre of gravity, you might need big stabs on the tail to compensate.

Can you adjust the downthrust of your motor easily? This will become important for the first tests...

I hope this helps a little...........

Bye
Mike
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Old Apr 21, 2009, 02:20 AM
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Mike,

Thanks for the info. Just having a spot of trouble. When I use your formula;

rotor-disc-area / mass-of-autogyro
(PI(16/12)^2) / 18.8 = 0.2970 oz per ft^2

and

rotor-diameter * PI / mass-of-autogyro
((32/12)*PI) / 18.8 = 0.4456 oz per ft^2

Is this me doing something wrong or are these the correct answer(s) (there are 2 different answers, what did I do?)?

Yes I can adjust the downthrust easily, and I will do calcs for the % stabilizer surface's area's I have.

Thanks
Doug
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Old Apr 21, 2009, 02:44 AM
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Baden-Baden, Germany
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Hello Doug...........



It was seven in the morning when I wrote the formulas........



I edited my previous post to have the correct formula, I am sorry for the mishap. The other values are checked, no mishap there. Perhaps my old-style steam-driven thinking-machine wasnīt heated up to working temperature this early in the morning.........

Bye
Mike
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Old Apr 21, 2009, 03:00 AM
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Mike,

Cheers, worked it out now at 3.37 oz per ft^2.

Thanks again
Doug
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Old Apr 21, 2009, 03:18 AM
Tannenzšpfle-Terminator
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Baden-Baden, Germany
Joined Dec 2008
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Hello Doug.............

Same result as me. 3,37 ounces per square-foot seems to be okay for a first try.

Doug, where are you living? The distance stated on the forum makes me think that its really late at night at your place....

Bye
Mike
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Old Apr 21, 2009, 03:29 AM
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Mike,

Im in Western Australia, right down on the south coast 120km from Albany. Currently it is about 4:30 pm so about an hour before sunset. We are currently in a thunderstorm so no model flying today, only building for me.

Doug
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