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Century Hawk - Falcon - Raven - Predator > Falcon 50 SE II - Center of Gravity

Lift
Elite Veteran
Location: Houston, TX

Can someone suggest to me proper angle or position that they have their CG set at on their Falcon SE V2?

I have been having a terrible time getting my Rolls axial. It doesn't appear to be pilot oriented because I can roll my R60 pretty cleanly. I will add that the roll performance has dramatically reduced since I went back to the woodies. Most likely due to the pitchy-ness I assume.

When the heli is fueled up it is taking quite a few clicks of Forward Cyclic to get it stable in an upright hover. But, an inverted hover requires quite a few clicks of Back Cyclic. To me this means that the heli is tail heavy.

So, could someone please advise on how to get this bird balanced properly?

Sorry for the newbie type question but this is the first heli I have owned that has displayed this. Mainly because this is the first heli I have owned that I have spent more time inverted on.

09-06-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

1" huh?

Ok, I have currently about 3/8" slope from front to rear currently. So, I got a ways to go.

I have tried to keep my model's weight to a minimum. I have a 4.8v 2700mah NIMH battery pack up front. They are not much heavier than an 1100mah 4.8v NICD pack. But, with all digitals I am NOT going to the equivalent mah that I have now in NICD. I will have to build an extension on my radio tray or add weight.

Or, lose the rear servo mount setup. Which IMHO is kinda disappointing. I love the smooth operation I have now and I couldn't get the the stock pushrod smooth enough to my liking. So, I hate to go there.

How do you balance the heli laterally?

09-06-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

Payton,

Our helicopters are almost identical, and I have not noticed a rolling problem with mine. You know most of my setup, but I will give you the details to see if it helps.

Painted canopy - adds weight to the nose
Gyro mounted up front with added plywood mount - adds weight
1700mah nicad mounted as far forward as possible under tray
Reciever mounted as far forward also.
Stock tail blades on it still - don't know if they weigh less then NHP's
Vblades - these are great blades, the Falcon said thank you when I put them on. There was a guy on here that had a set for $65.00. I paid $85.00 for mine, but then turned around and sold the Hurricane's for $50, so it only cost me $35, got them on here.

When I lift (hey that's your handle) it from the flybar, rear of skids lift off slightly before front. But only about 1/8".

Now my question is: Do carbon fiber torque tubes weigh less then aluminum. The cost probably is more, but if it saves weight, I may look into getting one.

09-06-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Falcon CG

Glenn et. al,
I have found that an EXCELLENT set of 600mm blades are the Gamma 600 CF. GR8LakesRC.com sells them for $55! You have to call them though. Mine weight 137g, fully symm, beautiful white gel coat like the SABs but fly a WHOLE lot better. I have flown Vs and you are correct. They are VERY tuff to beat. The only thing better is IMHO is the MAH blades. But, I despise high priced blades for my current experience level. Hence the woodies............

Also, doesn't Century sell an extended radio tray with their CF lower frame upgrade? I wonder if you can get it separately?

I haven't weighed them but you can tell by hand that the NHP blades are lighter than the stock blades. I have a set of 95mm on now and the tail is set tight in fast backwards flight!

09-06-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

NHP lighter: Good, the mail man just arrived with a set for me to put on. Sounds like yours is already lighter in the tail then mine, 3/8" vrs. 1/8".

I also do not like the cost of finer blades on a practice machine. I am going to put the woodies on for practicing auto's. I am not quite ready for inverted hover, but that should be soon. I think I should put them on for that also. I like the price of those Gamma's, I will have to try them if I demolish the V's.

09-06-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Woodies and autos....

Glenn,
I had my first boomstrike the other day. It was hot, still, and woodies on. I am flying the wonderful AeroTech 600mm woodies. For woodies these are about as good of quality as I have found.

Anyhow, I have some work to do with my autoing ability but I am shooting autos from 75 - 100 coming from the left and right trying to land near me. It is tricky with the woodies. They just don't have enough weight to make it easy on the beginner and intermediate auto shooter. So, using quality composite blades will make it easier. A comparison using the stock woodies and the Hurricanes is that on an equivalent flare and landing I could at least 2x the hang time with the Hurricanes. The Gammas add even more than the Hurricanes.

So, be advised that you have half the reserve at the bottom. But, due to the lighter weigh you can build up some nice rotor speed on the way down!!!!

09-06-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

Ah, well I need all the help I can get with the auto department. So sounds like I would be smart to leave the better blades on and practice carefully.

09-06-2002 Over year old.

Inspector Fuzz
Veteran
Location: Austin, TX. Where fat chicks succeed.

Falcon CG..

Howdy!!!
This is one of only a few things that I consider funky on this model.. I have quite a bit of weight up front and mine still acts a little tail heavy with a full tank of fuel.. It does seem to roll allright, but I usually have to "bump" the fore aft cyclic to maintain continuous rolls, one after the other.. With 8 gallons through this machine, I have had to do very little maintenance, and I am enjoying "fear free" flying... My Futura is getting lonely sitting on the shelf..

09-07-2002 Over year old.

oldfart
Elite Veteran
Location: Vancouver, Canada

fore/aft trim

Lift,

A rearward CG will do the following. As gravity always works in the same direction, a nose down trim (canopy forced away from the rotor) to counter the tail down weighting of the rearward CG when right side up will result in a nose up trim when inverted, plus a tail down force from gravity to compound it. Both the trim and gravity will cancel each other when right side up but will add to each other when inverted. This will cause the tail to drop during the inverted part of the roll, causing you to lose your forward speed and for the roll to look rather ugly. To make them nice, one would have to pump the fore/aft cyclic in proper time with the collective.

Conversely, a more foreward CG will work in your favor. Trimming nose up (canopy towards the rotor) to counter the nose heaviness when right side up will result in a trim that is still pulling the nose towards the rotor when inverted. This means that the trim is working to keep the tail from dragging (keeping the tail up) so that there is no drop in speed etc.....result nice rolls with less workload.... less fore/aft cyclic stick movement required.

Also with the proper cg, there will be little trim difference between hovering right side up and inverted.

Of note is that woodies all lead (including the better ones like the Aerotech) when rotating because they all have a rearward CCG (as do many composites I have tested). This will make the trimming even more complex, specially if there is any change in rotor speed as one goes through maneuvers. This also will render the blades less efficient in an autorotation as energy will be absorbed in the forward trim required to overcome the pitch up tendency of "leading" blades. Not to mention that these woodies are also a fair bit lighter then the gammas or the Hurricanes. I am sure you will find the inexpensive FunKeys great blades for practicing autos,

09-07-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

I saw a post a few months back in the Fury section of the forum, and Dr. Ben stated the following about adjusting cg, and it's effects on flight:

Quote:

The most Ideal way to trim out a Fury (or any heli) is to find a calm evening and fill the tank half full. With the swash level, adjust the CG fore or aft until the model hovers with no trim. This takes some work, but if you carry fore or aft swash trim into FF, you will induce a corkscrew into your rolls. Forward swash trim can cause a pitch-up when the model rolls inverted, with the reverse holding true for aft swash trim.

The optimization of trim around half-tank full avoids having a model which starts off a flight at one extreme of trim and finishes in the opposite direction. I used to fly Pro2's which shifted trim very little from full tank to empty. Set up as described, my Fury's trim shift from full to empty tank bothers me very little indeed.

Hope this helps some.

09-07-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Thanks...

Thanks guys. I will play with it some.

I absolutely despise adding weight but my options are:
1) buy a huge 2000+mah NICD battery to in place of my nice and light 2700mah NIMH pack

2) relocate my boom mount tail servo back to the factory location. (arrgh!!)

3) Add some lead to the nose of the canopy (arrgh!!)

So, since I am a cheapo I will go to the local fishing supply and find a single large saltwater weight and screw it to the canopy. After playing with it some I will have to add quite a large amount of weight to get that 1" slope on the skids.

I'll post back my finding if once I get a chance to test it out. Tropical storm FAY killed the flying here in Houston over the weekend and the next few days.

09-09-2002 Over year old.

oldfart
Elite Veteran
Location: Vancouver, Canada

Payton,

Your forward CG will also depend a bit on your flybar set-up and the blades you use. So experiment a bit with it. First try with just a slight nose down CG, maybe a 1/4 inch slope on the skids.

Phil

09-09-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Phil,
As posted above I currently have a 3/8" slope from front to rear. That is the the setting that is causing all the trouble as it is now.

I am using the MA White 3D paddles with Aerotech 600mm woodies running the stock flybar mixing ratios.

09-09-2002 Over year old.

oldfart
Elite Veteran
Location: Vancouver, Canada

Payton,

If I understand you correctly you are saying that you have a 3/8" slope etc. meaning that when you lift the heli by the flybar, the front lifts first and the back will only come off after the front is 3/8" up from the table top / ground (tail heavy)?

Alexander is saying to set it for 1" opposite - where the back of the skid comes off 1" before the front of the skid comes off (nose-heavy).

By experiment (due to different blades, flybar set-ups etc.), I mean to balance initially for 1/4" nose heavy and see how that works. Then play it from there.

In my earlier posting I referenced blades and their differing natural tendency to dynamically pitch the heli towards the rotor (tail down) when right side up (any woodie blades and many composite ones that "lead"). This will result in a "trim" to push the nose back away from the rotor to keep the tail up and nose down. This is all fine and dandy when flying right side up (except the trim reqirement will change with varying speeds and lift requirements).

But as with cg balance, this is compounded when inverted because the dynamic pitch will now try to push the nose away from the rotor resulting in a boom down attitude (screwed up roll) and so will the trim that was required when right side up add to this boom down attitude when inverted, as it is now commanding such an attitude.

This is why dynamically stable blades are so important for a "low workload" 3D or aerobatic flight.

P.S. You would be surprised how few rotor blades out there are not very dynamically stable. (I have tested some Carbon Fiber units from Korea that were dangerously bad, worst then any woodies I had ever tested). To check, hang both from a table with the their trailing edges back to each other but not touching. Now note how far from each other are the tips. The closer the tips are to each other the better. This isn't the only test but any blade that is dynamically stable will have to have a properly situated ccg. They will also have to have their CL properly located, but that is more difficult to check. No blade can be dymamically stable if it has a CCG that causes the blades to lead.

09-09-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Good info...

Phil,
That is all good information. And I agree with what you are saying. I didn't respond to your previous post regarding blade stability becuase I don't think that is the primary cause.

I have checked the CCG (Chordwise Center of Gravity) and both blades are well matched and have the CCG very close to the bolt hole location. Again these are Aerotech woodies which as you know are surprisingly very stable blades.

Now back to the model's static center of gravity. What I am describing is that when I place the blades parallel with the boom and lift the model via the flybar I have ~3/8" lift in the rear when the front of the skid lifts the table. This is where I am without any balancing attempted.

So, when I do a roll the tail is obviously being pushed down further because of the FORE cyclic trim from the upright hover. This compounds an already static weight distribution problem on the model which brings me to this thread about how you guys are balancing out on your Falcons. Yes, I do understand how the blades can amplify the problem. Actually, the Hurricanes rolled MUCH better than these woodies. But, the trim differences were still substantial.

Now, I do have some CF tailfins, boom supports, aluminum boom clamp, tail servo boom mount, ect. The weight savings from the CF is being offset by having the 9253 digital servo back there. But, I know others have mentioned here that they have experienced some off-balance conditions as well. My main question is at what point, skid tilt, ect. did they find the best stability(upright/inverted) and axial rolls.

As it stands I am going to try to statically balance the model to achieve the recommended 1" slope from front to rear on the skids and then go fly her. Since I am already at 3/8" just by looking I bet the 1" would probably do it.

Am I making sense now?

09-09-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

Makes total sense to me. It would be interesting to know what that 1" lift on the back of the skids becomes with the tank half full. If you check it out, please let me know.

And by the way Payton, you were correct about the NHP tail blades being lighter than the stock blades. Stock blades weigh 7.1g and the NHP's weigh 5.1g. Just got me a gram scale today to I am having fun checking things out.

09-09-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Off topic and then some.....

GForce,
Which gram scale did you get and how much? I would love to have one but don't know where they can be obtained and a reasonable price. Any tips?

I will try to remember to check the CG with a 1/2 full tank

09-09-2002 Over year old.

jimmyhua
Veteran
Location: Guam

Hey Lift,

I follow you!

To summarize, when hovering your heli, it seems tail heavy. However, when you measure it, it measures out a little nose heavy.

Simple Solution: Add more nose weight & get rid of that forward trim.

Complicated Solution:

Question. Do you fly in an area where there's a constant wind in the same direction? Do you hover into the wind all the time?

I'm asking this, because it's possible that, you should just get rid of that forward trim, and don't change the CG. Just get used to hovering, and always pushing a little forward cyclic.

I think the true root of your problem is that the Raptor rolls over so quickly, it doesn't have a chance to show you any bad tendencies. On the otherhand, you're doing slo-mo rolls on the Falcon with flybar weights. This is just a guess on my part

.

I am always pulling a little aft cyclic during an inverted hover. But that's cuz I have the heli trimmed out to hover properly upright into the wind. If I had it trimmed out correctly, I'd have to push a little forward cyclic on the upright hover AND a little aft cyclic on the inverted hover. The wind can be annoying.

If you want to solve this "problem" of heli always balooning into the wind, You need the right paddle+mainblade mixing combo. This will take some trial and error. (I have never bothered to do this

Too much work!!!)

You've chosen Aerotech woodies. Okay, stick with them. Because woodies baloon more than CF blades, you need to either change the paddle mixing ratio or the paddle itself to counteract the balooning. First I would try increasing paddle to blade mixing, as it's cheaper. Then, try different paddles. Keep trying different paddles, until the heli stops pitching up in fast forward flight, and is now instead completely neutral in fast forward flight. Now, re-trim and you should be done.

The catch now is, once it's like this, if you decide to switch to CF blades, the heli will pitch down in fast forward flight, so watchout!

I think they got the Falcons tuned out, so they work perfect with the Vortex CF blades, and A-arm to short balls on swash. It's pretty close with the Hurricane's though, that I don't even mess with it.

Btw, I do believe that the simple solution will solve your problems. So you can go that route first. MORE nose heavy please

.

Jimmy

09-09-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

Digital scale

Got mine from Cyberscale for $54.99. It is good to 1/10th gram, but only goes up to 250grams, so you can't weigh anything substantial, but it is excellent for balancing blades and such.

Here is a link:

http://www.cyberscale.net/catalog/p...75b1681d26d0d39

09-09-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Jimmy,
Thanks for the tips. My main concern is the static CG. Although, with the White MA 3D paddles (20 grams) and Aerotech woodies there is some work to be done to stablize the flying disk vs. the control disk. I want to first get the CG sorted out and then go back to the Bell/Hiller mixing. Initially I found that the Hurricane/Gamma blades work great with the 3D paddles. But, without some flybar weights they are NOT ideal with woodies!!!!

First I want to get the model back to a more neutral trim. I am 4-5 clicks forward trim upright hover and 4-5 clicks trim inverted hover off center. With a properly balanced model I don't know if it is possible to achieve a perfect balance for both orientations. But, if I can get the gap reduced to 1 click forward for upright hover and 1 click back for inverted hover then I will be happy. I actually am more than 4-5 clicks off. I just can't remember how much. But, I set my swashplate up level on the bench. In flight I trim it out and then go back to the bench and make mechanical/Cg changes to get it right.

Glenn,
Thanks for the link!! That is exactly what I was looking for. I have always wanted either a digital scale or an OHaus triple beam. They carry both!!! I can see it now, "lets see how much this weighs, and this, and this,............"

09-10-2002 Over year old.

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Century Hawk - Falcon - Raven - Predator > Falcon 50 SE II - Center of Gravity

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