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View Full Version : Posted on Helifreak and got ignored. Can someone here answer?


Curtis
01-13-2008, 08:05 PM
I posted this on Helifreak and got totally passed over - evidently I'm not in the club or something? Could someone be so kind as to give this newbie some basics on blade selection for 500-600-class (41" rotor) helis?

I know that with fixed-wing aircraft certain airfoil shapes have certain aerodynamic qualities: Flat-bottomed, high camber airfoils have high lift at low speed and relatively high drag; good performance when all lift is 'up' in the vertical axis, full symmetrical high lift at high speed equally on each side of the airfoil, etc.

Which would be the best blade for learning, i.e. hovering, scale-like flight? Flat-bottomed (thanks to Queen I always want to say, 'Fat Bottomed' http://www.helifreak.com/images/smilies/icon_lol.gif ) airfoil, or a semi-symmetrical shape?

Do blade manufacturers sell blades by model, or do you have to know the specs to buy non-OEM blades? For example for an Ikarus Royal/Eco 8?

Thanks!!

firemanbill
01-13-2008, 08:50 PM
I wish I could answer but Ir eally can't. Just posting to show you won't be ignored here!:D

I'm sure one of our Heli experts will pipe in here soon!

Good luck!

Curtis
01-13-2008, 08:58 PM
Thanks, Bill :) I feel better already!

rcflyair
01-13-2008, 09:40 PM
Hey Curtis,

I would stick to flat bottom for learning, semi for learning or mild aerobatics, and symetrical for aerobatics. You can certainly use any type of blade for any type of flying though. You're right in the airplane airfoil similarity though - flat bottom for a trainer, semi or sym for aerobatic.

I would get the recommended length and chord blades. Really the hardest part about getting 3rd party blades is fitting the blade into the heli's blade grips. The blade root has to be just the right thickness, or shimmed. Same with the hole in the blade root, just right or shimmed. If you're starting out, you'll save much aggrivation by just getting inexpensive, manufacturer recommended blades. When I was starting out, blades didn't last long anyways:<:

Welcome to wattflyer, lots of good help here....

Curtis
01-13-2008, 10:53 PM
Thank you kindly for your response!

I would imagine the blade grip connection is absolutely critical and not something to be trifled with.

Flat Bottomed Girls it is :)

HeliG
02-12-2008, 07:50 AM
Fat bottomed girls make the world go round! :Q

geekdisk
02-27-2008, 10:41 PM
Trying to find flat bottom heli blades is pretty tough. I've looked myself for the t-rex 450, HDX 500 and T-rex 600.

I fly scale, not 3D so I want long lasting flights with all forward flight. Maybe a few rolls or a loop but nothing tough.

I gave up looking for flat bottom blades and just went with what is available.

For the 450-size heli's the 325 wood blades offer the best performance/price point. I've gone through about 15 sets so far in ~200 flights and am very happy. They turn to dust in a crash, but also eat lots of energy saving the rest of the heli.

CF blades are better for heavy heli's but are at least $30 per set for 325mm and do more damage in a crash to the body and servo's. Can speak from experience in 4 crashes.

You also want to be careful of the RPM that you spin wood blades, anything over 2700 rpm may be dangerous.

Curtis
02-28-2008, 01:26 AM
Thanks!

Yeah, I think even the woodies that came with my Royal are semi-symmetrical. The Royal has a max recommended headspeed of 1650, so I think I am pretty safe there. I noticed they didn't even recommend epoxying the blade holders to the blades.

Thanks for the reply!

write2dgray
03-19-2008, 01:00 AM
Yep, flat bottomedds are nearly impossible to find for larger (450+) helis. For long flights I would recommend starting out with woods and then eventually upgrading to some nicer CF blades. I have found that efficiency improves measurably with CF blades, even with a similar profile, mostly IMO due to the stiffer rotor disc and decreased drag.

- David

brnyrbbl
03-19-2008, 01:29 AM
Thanks!

Yeah, I think even the woodies that came with my Royal are semi-symmetrical. The Royal has a max recommended headspeed of 1650, so I think I am pretty safe there. I noticed they didn't even recommend epoxying the blade holders to the blades.

Thanks for the reply!
If I understand, you mean the blade grips right? If so, you never want the blade so tight that it doesn't have any swing in the grip. I snug mine up just to where they don't move freely but can be pushed with little effort using one finger. That way in the event of a crash it will give a little resulting in less head damage since the blade will fold away somewhat absorbing the shock. I agree to sticking with the wood blades as they will also absorb the impact by breaking away hopefully saving a feathering/spindle shaft and other head parts (or even a main drive gear). Semi semetrical seems to be what I have seen also. If you could find truly flat bottomed blades, that would be best for starting off. You nailed it with your airplane comparison. Flatter = more stable, Semetrical = maneuverability/tricks. If you want even more stability, you can add more weight to the flybar paddles to help with the gyroscopic effect which also increases stability and decreases squirreliness. Good Luck!

vortex05
03-19-2008, 06:04 AM
Thanks!

Yeah, I think even the woodies that came with my Royal are semi-symmetrical. The Royal has a max recommended headspeed of 1650, so I think I am pretty safe there. I noticed they didn't even recommend epoxying the blade holders to the blades.

Thanks for the reply!


Ok it's a big misconception that helicopter blades are stiff along the grips and don't move at all. In fact blades move both along the vertical axis (with the see saw) and they should be allowed to lead and lag naturally. This is a good thing for self centering and improving stability. This is a good thing considering you can never setup the blades for perfectly centered by hand, unless you spin it up before epoxying but then the epoxy will throw off the balance. The usual test is that the blades should be snug enough to not fall on their own weight but you should be able to move them 2 inches by flicking it with your finger.

If you tightened it too tight you'll find vibrations on spin up. Pilots doing 3D will need a tighter setup to respond quicker, and learning pilots will do well to leave it relatively loose to dampen inputs, and improve hover characteristics. I'm not sure if it makes that much difference in large sized helis but in the blade CP the blade grip tension really changes the flight characteristics.

Old Sloppy
04-13-2008, 07:54 PM
I am a beginner (well sort of ) and I went with HeliMax CF 600 mm blades.
I find them real easy to fly with on my Trex 600e.

Flat bottom blades like lower head speeds and will give longer flight times, but are more difficult to maintain a stable hover.

I have read that flat bottomed blades will climb on you in a slight breeze and I think that will mess up a beginner pilot.

Symetrical blades like higher head speed, this adds stability for a newbie pilot.

So really you do not want flat bottomed blades for a beginner.

Harry :tc:

neilg.
04-13-2008, 08:01 PM
Fat bottomed girls make the world go round! :Q

no comment ;-)

Old Sloppy
04-22-2008, 12:36 AM
So Curtis, Have you found any flat bottomed blades to fit your heli ?
Harry

HeliG
04-22-2008, 01:51 AM
Harry,
I was looking at your pics a few posts up... Very impressed!!! How do you get that heli to stay in the air with the main blades not moving?!? :tc:

Old Sloppy
04-23-2008, 12:03 AM
Harry,
I was looking at your pics a few posts up... Very impressed!!! How do you get that heli to stay in the air with the main blades not moving?!? :tc:




It must be the camera's shutter speed matching the mainblades....

see my avatar for an actual head speed demo.( about 60 rpm)

Or else I photoshopped it. ( a fake pix )

Harry :tc:

HeliG
04-23-2008, 12:16 AM
It must be the camera's shutter speed matching the mainblades....

see my avatar for an actual head speed demo.( about 60 rpm)

Or else I photoshopped it. ( a fake pix )

Harry :tc:

Harry,
You took the fun out of it! I knew the real answer but...

Anyway... the moving avatar is cool. How did you do that? Is there an avatar program? I think I'd like to try making one even though it will eat up more of my time.

Old Sloppy
04-23-2008, 12:31 AM
My avatar is not moving, it must be your imagination ......
or else you have been drinking.....L.O.L.

Harry :tc: