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Test flew my new FA-61 yesterday.

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Old 04-30-2006, 07:32 PM
  #1
soarrich
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Default Test flew my new FA-61 yesterday.

I built a FA-61 from MB plans, but the only thing I used from the plans was the FA-61 name, I can't use plans, I always change everything.

I used two bladed aerobalsa rotors because two blades are just so much easier to balance than three. I put 1/16 inch shim under the TE of the rotors at the hubs, so I think they are about -3~4*

I have the blade going forward on the inside of the rotors, my thinking is the advancing blades are making more lift than the retreating one and they're closer to the center line. I don't know if it matters though, I think all the lift is being applied to the rotor axle. Any input on this?

I got nervous while finishing the axles and bent them outward some to lower the dihedral, but I think I over did it because the roll response was very marginal.

I think I may need more rotor angle, in the last picture the gyro is climbing, but not that much.

On the one test flight so far the rotors spun up nicely, but the gyro didn't fly itself off the ground, I had to give it full back stick, then it climbed away. I had let the gyro run on the ground waiting for it to lift off for a long time, I should have stopped the takeoff without lifting off. By time I rotated the gyro to get it off, it was a LOOOOng way away, I turned left, but it turned very slowly, so I was even farther away. As you can see in the last picture the gyro is in a slight right roll, but I had lost orientation, I knew it rolled, but I wasn't sure which way, (the air was very choppy), so I cut power, and let it land. The field it landed in has stubble from sticker bushes that have been cut down and the stubble trip the gyro making the rotors break. For a test fight I guess a couple broken rotors is so bad.

Do you guys see anything obviously wrong with what I've got so far? The motor is -10* the hang angle is about -8*, the rotors are +10*, rotors a 36inchs each, I haven't weighed it, but the wankel has more than enough power for it.
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Old 04-30-2006, 08:34 PM
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Default RE: Test flew my new FA-61 yesterday.

What does it weigh? What's the disk loading?
By dropping a blade you have increased the loading per blade by
by 50%, thus it's likely to be fast.
It more than likely is not going to turn without the dihedral.
Your advancing blade is providing the lift to roll into the turn, putting it
inboard further reduces the ability to turn.
What are all the angles measured against?
What angle are the rotors at when it's sitting on the ground? This is key
to takeoff.
mickey
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Old 04-30-2006, 09:25 PM
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Default RE: Test flew my new FA-61 yesterday.

Quote:
ORIGINAL: mnowell129

What does it weigh?
65oz.
Quote:
ORIGINAL: mnowell129

What's the disk loading?
With the 36 inch diameter rotors, 4.54 oz/ft.

Quote:
ORIGINAL: mnowell129

What are all the angles measured against?
Datum line on the fuse.

Quote:
ORIGINAL: mnowell129

What angle are the rotors at when it's sitting on the ground?
It looks to be about 17*

Quote:
ORIGINAL: mnowell129

It more than likely is not going to turn without the dihedral.
Your advancing blade is providing the lift to roll into the turn, putting it
inboard further reduces the ability to turn.
Mickey
It has some dihedral ~4*, but if the advancing blade flex's up maybe less. So you think I should add dihedral and swap the rotor to be advancing blade on the outside?
Rich Border
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Old 05-01-2006, 05:19 AM
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Default RE: Test flew my new FA-61 yesterday.

Hi!
Do you think that it's a good idea to decorate your autogyro with a swastika? Your model isn't scale at all, and so i think you shouldn't use Nazi emblems to beautify your model!
Just think of all the victims of the Nazi regime!

Stefan from Germany
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Old 05-01-2006, 06:07 AM
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Default RE: Test flew my new FA-61 yesterday.

Quote:
ORIGINAL: soarrich

With the 36 inch diameter rotors, 4.54 oz/ft.

It looks to be about 17*

Mickey
It has some dihedral ~4*, but if the advancing blade flex's up maybe less. So you think I should add dihedral and swap the rotor to be advancing blade on the outside?
Rich Border
I try to keep the disk loading to 2.5 oz/ft for reasonable engine out performance.
I'd put the advancing blade outboard myself.
17 degrees is right on the edge, I try to do 20 degrees ground stance.
A footnote:
Once the rotor is up to speed the lift force exerted on the model
is the same for the advancing blade and retreating blade.
This defies common sense but is true.mickey
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Old 05-01-2006, 07:11 AM
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Default RE: Test flew my new FA-61 yesterday.

Mickey

I think I'm stuck with the disk loading I've got on this one, no room to go bigger on the rotors without inter-meshing them. I will try putting more lean-back in the rotor axles to get 20* on the ground, I can't put taller gear on it, they're built in and don't unbolt. Switching rotor rotation is easy, I had a 50/50 chance of getting it right, no Las Veges trips in my future.

Steph

I plan to add more scalish details to it once I get it flying well, and I'm an American, we won and we have freed more people than all the other countries in the world combined, so I, (we?) don't have guilty consciences.

Rich
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Old 05-01-2006, 07:19 AM
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Default RE: Test flew my new FA-61 yesterday.


Quote:
ORIGINAL: soarrich

Mickey

I think I'm stuck with the disk loading I've got on this one, ...I will try putting more lean-back in the rotor axles to get 20* on the ground....
When you break the rotors, try replacing with 3 or 4 bladers. The takeoff will get shorter
and it will fly slower.
mick
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Old 05-01-2006, 07:54 AM
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Default RE: Test flew my new FA-61 yesterday.

I'll have to order more blades, I only have enough on hand for another set of two bladed rotors. Speaking of breaking rotors, I just doped these that I was using, does covering them with monokote or glassing them make them more durable, or just heavier and slower to spin up?
Rich
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Old 05-01-2006, 08:58 AM
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Default RE: Test flew my new FA-61 yesterday.


Quote:
ORIGINAL: soarrich

I'll have to order more blades, I only have enough on hand for another set of two bladed rotors. Speaking of breaking rotors, I just doped these that I was using, does covering them with monokote or glassing them make them more durable, or just heavier and slower to spin up?
Rich
Covering improves the performance, significantly on small models.
I wrote a post on how I cover blades somewhere here or on RCGroups.
Rotor spin up time seems to be a major concern for new autogyro modellers
but is much less a concern more experienced autogyro fliers.
When the geometry is right and the rotor pitch is set correctly the spin up
is very quick. I run 3" of 1/16" lead solder in the tips of my 16" blades for CG
correction.
BTW my 16" 1.5" aerobalsa blades weigh 10-15 grams (1/3 to 1/2 ounce)unfinished
and 18-25 grams ( .6 to 1 ounce ) finished. Spin up is normall not an issue except on
dead calm days on a rough surface (hence the pre-spin mechanism). Normal takeoffs
off a smooth surface are from 10 feet with wind to 50-75 feet in dead calm.
mickey
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Old 05-02-2006, 06:52 AM
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Default RE: Test flew my new FA-61 yesterday.

Quote:
ORIGINAL: mnowell129

When you break the rotors, try replacing with 3 or 4 bladers. The takeoff will get shorter
and it will fly slower.
mick
Mickey

I thought I read the fewer blades the faster the blades turn, but I didn't think the gyro would actually fly slower, or lift off more quickly by adding blades, but in you experience you found that it will?

Rich
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Old 05-02-2006, 07:58 AM
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Default RE: Test flew my new FA-61 yesterday.


Quote:
ORIGINAL: soarrich

Quote:
ORIGINAL: mnowell129

When you break the rotors, try replacing with 3 or 4 bladers. The takeoff will get shorter
and it will fly slower.
mick
Mickey

I thought I read the fewer blades the faster the blades turn, but I didn't think the gyro would actually fly slower, or lift off more quickly by adding blades, but in you experience you found that it will?

Rich
Don't know about the fewer blades/faster connection. Fewer blades are
more efficient for a propellor since the blades don't run in the wake of
the blade ahead. But the gyrocopter blades are running in clean air
since the airflow is from below. Blade speed seems to be more of a function
of the blade design and craftsmanship rather than number of blades.
The blades are making the lift so more of them provides more lift.
My rule of thumb is that you need a disk loading of 1.25 ounces/sq foot per blade
to have good performance. 2 blade = 2.5 oz/ft, 3 blade = 3.75 oz/ft, 4 blade = 5 oz/ft
mickey
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Old 05-02-2006, 08:42 AM
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Default RE: Test flew my new FA-61 yesterday.

Mickey

Thanks for the help, I ordered enough blades to make a couple of 4 bladed rotors, because I'm at 4.5 oz loading.

Rich
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Old 11-21-2008, 10:38 PM
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Default RE: Test flew my new FA-61 yesterday.

Could you provide some contact information for the plans you used on this model? Nice work by the way, and as for the comment about the aircraft markings, and the "Not Scale" comment, I wouldn't worry too much about it. The aircraft may not be scale, but your markings weren't either. LOL. Germany produced some of the coolest aircraft in history, well ahead of thier time. In Germany it is against the law to display a Swastika, even on a true scale aircraft. I am in the U.S. Military, and I was stationed in Germany for several years. I am also an avid scale plastic model builder. I once bought a kit from a hobby shop, and the kits have all been pre-opened and the markings are removed from the kits, the pictures on the box have been blacked out ect. Fortunatly for you, guys like me serve in the Military to give you the right to put anything you like on your aircraft, so enjoy. I for one don't feel like having an appreciation for the outstanding German engineering of the era implies you condon any attrocities that occured in that era. Anyway, no need to explain yourself, you've built a nice model. Any info you could provide would be appriciated.
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Old 11-21-2008, 11:38 PM
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Default RE: Test flew my new FA-61 yesterday.

Model Builder Magazine plan # 4751. I'll look to see if I still have them. I really didn't use them much, about the only measurement I used off the plans was the fuse length. I'm a scratch-builder at heart and I told my friend I was going to build one and he said he had the plans for one. The plans show trike gear and just a bent aluminum bar for the outriggers, the used cox .049 crankcases for rotor-hubs.

This is a good site to look through.

http://www.autogyro.com/models/models.htm
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Old 12-04-2008, 02:56 PM
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Default RE: Test flew my new FA-61 yesterday.

I think you will find that 3 bladed rotor will spin up easier & faster than 2 as 1 of the 3 blades is always in to the oncoming breeze.

J B always swore that the inside blade moving foreward works better. That is what I did with my Gyrace & it works well after 7 years of flying it. I don't know why.
His info is still posted at the old autogyro.com web site.

You appear to have a lot of dihedral in your rigging. Is that per the plan?

Also, there was an addendum to Skip's plan in M.B. a few months after it was originally published. A few recommended improvements.

What did you use for spars?

Goodluck,
Bob
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Old 12-04-2008, 05:00 PM
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Default RE: Test flew my new FA-61 yesterday.

Good point.

It should be an inverted pentagram.
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Old 12-04-2008, 09:01 PM
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Default RE: Test flew my new FA-61 yesterday.

I used 1/4" wood dowels to make the outriggers. I started with the MB plans, but the only thing about the MB FA-61 and mine is they are both about the same length.

I made a new set of rotors 3 bladed with the blades pivoting. I think it had too much diehadral it was VERY roll sensitive in the air.
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Old 12-05-2008, 11:02 AM
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