Trimming out a new heli need advice

[totalgeek]

How do you trim out a new heli? This is my first build and even though I measured everything and dotted my i's and crossed my t's what is a good trim in procedure? Just get it light and see what it does? My fear is that I mis-measured and as soon as the heli gets "light" it bee-hives it into a wall or just tips over quickly and I can't catch it fast enough on the tx.

I guess I'm just scared. If anyone has any good tips I would like to hear them.

[fllyer]

You don't need to be scared of your heli at any point, but you do need to be cautious of your flying lawnmower. :fly

My best suggestion would be to find an experienced pilot that's close to you and ask him/her to check out your heli and trim it (if it's at all possible).

If you can't do that, don't try to hover and trim at the same time (don't ask how I know). It's best to land it and move the trim lever the opposite direction one or two clicks at a time. Testing after each adjustment until it's hovering hands off for 1 - 2 seconds.

Once it's trimmed out, your golden! :glasses2:

[vera]

Training gear is a comfort in such a situation.

Cyclic trim is for fixing a swash that isn't quite level with no trim. So if the swash is level and (the CG is correct) then it's isn't going to go nuts. If you don't have a swash leveling tool you can measure the blade pitch on one side of the heli (left or right) and then the other side of the heli (same blade) and adjust the fore/aft tilt of the swash to get the values the same. Likewise, measure the pitch with the blade out front and then in back and adjust the left/right tilt of the swash to get the values the same. In summary, if the blade pitch is the same all around the circle the swash is level.

Pep talk: Remember, the trim is a device for making it comfortable to fly the heli, but you are the pilot. If you have to put your foot on the stick to keep the thing under control, then do it. Keep the thing under control even if it isn't comfortable. If a friend asks you why you crashed, you don't wanna have to say, "It was because I wasn't comfortable."

I used to be a flight instructor and I made my students fly with the trims all messed up to get them used to the idea of being in control regardless of comfort. Fly first, and as soon as you can, get comfortable.

When you lift that thing off, be paying attention to your rotor disk. The heli is going to go whichever way it's pointed. Keep it somewhere near level... need a little right tilt to compensate for the tail, but aside from that just don't let the rotor disk get any wild angles no matter what you have to do to the stick to do that.

And like fllyer says, if you need to mess with the trim, set it down first.

A heli in a hover is basically an unstable thing. But at least for a few seconds, if the thing is in a steady hover and trimmed right then the tilt angle of the rotor disk (which will be slightly to the right with a CW rotor) will stay put with the cyclic stick centered. If the rotor always starts increasing a tilt in some direction when the cyclic is centered then the swash isn't quite level and you need a dash of trim to fix that.

Even just by eyeball, if the swash looks to be pretty much "level" (perpendicular to the main drive shaft) then the heli isn't going to do anything radical. You will easily be able to keep it under control. You'll just have to hold a bit of stick in some direction.

[kgfly]

Take a look at RADDs flight school, it could save you a lot of repairs: http://www.dream-models.com/eco/flying-index.html

[totalgeek]

Thanks everyone I took fllyer advice. I took it to my LHS which is owned by a cool HELI guy ( Hi, Mark for HC & M in Reno) and he trimmed it out and adjusted my gyro. The only problem I have with this is, what am I learning? I was there over his shoulder the whole time and asked questions but I don't know if I would be able to repeat the process.

The good news is its now hovering! YEAH!!! This is so much more solid then my Axe CP, that model almost made me give up flying, but with this new copter all set up it works great!

I just want to be able to trim and setup my copter on my own but I don't think I can do that :( What if the guy at my LHS goes away? Then what? Thats why I built the kit and went to him as a last resort. I wish I went sooner because I totally made a noob mistake by switching channels on my swash servos so when I thought I was rolling right it was really going left - broke a servo. Important lesson learned - pre-flight checks! :oops:

Vera thanks for the advice and words of wisdom. I guess I was just timid and took it to my LHS. But your advice is great and I have it saved on my computer for future reference. Maybe one day I can trim out my own copter.

Vera you also bring up a point, and this quesiton is directed to anyone else. My guy at HC&M, whose help I totally appreciated and in no way is my intention to offend him, but I need to ask more expierenced pilots and get their opinion, said not to fully compensate for the tail, my copter tends to drift left if left uncheck. Do I trim this out, or do I leave as is and compensate on my cyclic/pitch stick to keep it in one spot? It can stay in the air for about a second with hands off and I have to compensate by pushing right on takeoff, is this the correct way to fly the heli, or do I need to trim that left drift out?

[kgfly]

totalgeek,

I don't use the trims at all. If you build a heli properly with a level swash, the CG under the main shaft, blades balanced and tracked and gyro tuned then no trim is needed. So the key is learning how to build and setup a heli, then you never need to learn how to trim it. For build and setup you can learn a lot from the Finless build videos.

Compensating for the leftwards push of the tail rotor with a little right cyclic input is normal and becomes quite automatic. In a stable tail-in hover your heli will be leaning a little to the right.

[fllyer]

Thanks everyone I took fllyer advice. I took it to my LHS which is owned by a cool HELI guy ( Hi, Mark for HC & M in Reno) and he trimmed it out and adjusted my gyro. The only problem I have with this is, what am I learning? I was there over his shoulder the whole time and asked questions but I don't know if I would be able to repeat the process.



The main reason I said to take it to an experienced pilot was to get you in the air and learning.

Once your comfortable flying (or at least hovering) then you shouldn't have any problems trimming out your heli.

Plus any help is better than no help. :arggg:

[vera]

copter tends to drift left if left uncheck. Do I trim this out, or do I leave as is and compensate on my cyclic/pitch stick to keep it in one spot?


I share your desire to understand things. A heli is quite a tangle of interrelated actions. A complete description of any one action requires visiting the whole nine yards. Sometimes we can ignore the rest of the related factors because their effect is small and swamped out by other considerations, and other times the contraption just won't be understood without considering at least some of the rest of the story. On the bright side, one doesn't have to understand all things to learn to control it.

Let's consider a bit of trivia just to introduce the tangle of things. Here we have a perfectly adjusted heli in a perfectly level hover in perfect air. Wow, it's hard to stand all that perfection, but fear not, it's about to go down the drain. You know the tail rotor blows air to the right to stop the tail from swinging right, which it wants to do because of the engine torque trying to spin the heli left, and so that thrust from the tail rotor blows our perfect hover by making the heli start to drift to the left. If we did nothing about this a new complexification would emerge, but we roll the heli just a little to the right to stop this drift. Well now, with the rotor disk tilted to the right, providing exactly enough thrust to stop the drift, look where that thrust came from. We robbed a little of the thrust that was doing battle with gravity. Since our thrust from the main rotor is tilted a little sideways, which is dandy for the drift problem, we now have a little less of it pointed straight up. The heli descends. So now we need a little more throttle to make up for this loss of thrust. That gives more torque. Need more pitch on the tail - more thrust - to combat the additional torque. That's more load on the engine. Need more throttle to feed that hungry mouth. And this results in a need for a little more tilt on the main rotor. This goes around and around like that, eventually reaching a place where everything is happy. This is a trivial example because you probably won't generally notice it. It's almost just theoretical.

A not so trivial sting of events happens when the heli starts to move. In that case the part of the rotor disk that's at the front of the motion, which would be the left side of the heli if it's drifting left, is moving into fresh air and thus it generates additional lift. This "transverse flow" of air tends to stop the motion. You can easily see this happen. Just lift the heli and don't make any drift correction. As it starts to move to the left the left side of the heli gets more lift and rises, tilting the rotor disk to the right, which tends to stop the drift. I'm not suggesting that you wait around for the drift to stop, we just looking at how things are interrelated. Besides, the heli will over-correct because of one of Newtons laws about stuff tending to keep on moving, and it will tilt too much and then start to drift to the right. In that case, the right side will be getting the fresh air and it will then tend to rise, and this process will repeat going the other way. As it oscillates left and right it will also be going up and down (if you leave the throttle alone) if left to itself, for the reason mentioned above. This is not a comprehensive rundown on all the actions going on but you can see that one thing affects another and it kinda goes around in circles.

Moving on. One of the jobs of the swashplate is to tilt the rotor disk. On a fixed pitch machine that's all it does. For the subject of trim, we're only interested in the tilt of the swashplate because that's what tilts the rotor disk. With a perfect mechanical setup the swashplate is "level" (perpendicular to the drive shaft) when the cyclic stick is in the center. If the swashplate is level then the pitch on a blade will be the same all around the circle. Therefore, the lift produced will be the same all around the circle. If the balance point is exactly at the center of this circle then there is no force being applied to tilt the rotor disk.

Now let's look at what happens when you move the cyclic, or add some trim. This is one of those tangles that requires considering a bunch of stuff, but I'm going to ignore all that stuff and so the result will be wrong; in the sense of being incomplete. We'll try to fix that later. For now, here we have a little tilt in the swashplate. It doesn't matter how it got there... trim or stick or goofed up setup. And again, by "tilt" I'm referring to the angle between the rotor disk and the drive shaft, not the ground.

When the swash it tilted the pitch on a blade changes as it goes around the circle... it "cycles" the pitch... which is why it's called the cyclic control. Amazing, isn't it. :mrgreen: So this means the lift is different around the disk. Some part of the disk is going to be pulling up more than another part, and so the part that's pulling up harder is going to roll the disk in some direction. That rolling force stays there for as long as the lift is uneven, which will be for as long as the swash is tilted. The amount of tilt on the swash determines just how different the lift is on one part of the rotor disk as compared to another. That determines the rolling force, which determines the rolling rate.

The point I'm trying to get across here is that the amount of tilt on the swash does NOT determine the tilt of the heli, it determines the rate at which the disk rolls. If you put in just a wee bit of tilt on the swash, the rotor would tilt slowly and keep on tilting slowly and it would do this till it's upside down and keep on doing it till it's rightside up again, over and over. If you tilt the swash a lot then the roll is rapid, but it just keeps on rolling for as long as the swash is not level. It rolls towards the low side of the swash; whichever way that may be.

Now I warned you that the above would not be correct. That's because I've ignored what the heli would do about being on its side, or upside down. But you know that it's going to be going somewhere just as soon as all the forces are no longer exactly balanced in all directions. For example, as it starts to roll it will start to go and that will produce the transverse flow which will slow down the roll but as the roll continues the vertical component of the thrust is pooping out and so the heli starts down and .... But no matter. The point here is just that the swash should be level at center stick and this will eliminate the tendency to roll. It shouldn't be rolling in any direction unless you provide input. Once you terminate the input, by returning the swash to level, the rolling force is removed and the rotor disk will tend to stay in its current plane of rotation. Again, other factors are involved but here we're not interested in that whole saga.

I've said all that blabber to help you see why the swash should be level. When you have correctly compensated for the drift caused by the tail rotor, you will want the tilt of the rotor to stay put; because you got the tilt that works. To make the tiilt of the rotor stay put you need zero tilt on the swash, which means the cyclic needs to be centered. Take careful note, the swash is level when the correct tilt of the rotor disk is established. I'm ignoring aerodynamic action which will invalidate that statement, like in forward flight, but here we're talking about a hover.

If I've made any sense to you then you will see that the trim is not used to correct for drift. Trim (aileron/elevator) is used to correct for a swash that isn't level or a CG that's off. It's better to get the swash as level as possible mechanically and try to get the CG located under the center of the hub. By "best" I just mean that it gives you the same amount and rate of control in all directions.

Assuming you have a level swash and the CG is correct you won't need any trim at all for hovering. You do need a little tilt to the right, and so as you take off you immediately make a brief roll to the right to establish the necessary small amount of tilt to block the drift, and once you have that amount of tilt you center the stick to stop the roll. The tilt stays put. Well... :oops: ... sorta... nothing much really stays put, does it.

If you were to set a little right trim on a perfect heli, then the heli would roll to the right on its own when you lift off, but it would just keep on rolling steeper and steeper and you'd have to be holding left stick to keep it from rolling farther than need be. You only need a brief small "one time" roll to the right to correct for drift and that means you only need a brief small one time tilt of the swash. Once the necessary rotor tilt is established you want the heli to stop rolling and so the swash needs to be "level" (perpendicular to the drive shaft) to even out the lifting force and thus eliminate the rolling force.

Again, I've not considered everything involved in the total tangle of events. One thing we ought to consider in a perfect hover is the fact that the CG is somewhere BELOW the center of lift (CL) of the rotor disk; in a rightside up hover. And in our perfect right tilt the CG is also somewhere to the LEFT of the center of the CL. Nature being what it is, the CG would like to drop down under the CL, pivoting the shaft to the straight upright position in the process. That is, there is a force trying to roll the heli to the left. But that force is offset by the force of the tail rotor which is trying to move the heli left, resulting in a force to roll the heli to the right. These forces cancel in a perfect hover... when the tilt is correct to offset the drift.

In forward flight the air around the heli helps keep it straight and so less thrust - thus pitch - is needed on the tail rotor, and therefore, less tilt on the main rotor. In fast forward flight the tail pitch might be zero, and so no tilt would be necessary.

I share your enthusiasm for details and that's why I ramble on. I hope you can see that the aileron/elevator trims are for dealing with the small remaining things that are not exactly precisely utterly perfect. The trims are used, in a hover, to keep the rotor disk from tending to roll in any direction.... left/right or nose up/down or any combination. You need a calm day so that wind isn't a factor. When you're holding in one spot the rotor disk will hold a steady angle with respect to the ground. With the cyclic stick centered it should stay that way... as best a heli can stay any which way. If it starts to roll and keeps on rolling as soon as you center the cyclic stick, then you need some trim to stop that. Do all you can to get the mechanics set up correctly, and you may need to use a dash of subtrim to do that, and the main trim is to polish off the details that escape the eyeball.

[totalgeek]

So the key is learning how to build and setup a heli, then you never need to learn how to trim it. For build and setup you can learn a lot from the Finless build videos.


I watched the finless vids backwards and forward, the build vids and the CCPM setup. I don't think I would gotten as far without the Finless vids. Well I'm pretty hooked, at least into building a copter. I'm already planning on building my next micro (for some reason I don't have a feeling of going to gas or a 30 or higher type heli just yet), I think I'm addicted to the building process and I love seeing the copter I built in the air. Hopefully, with this one I can trim out on my own.

Thanks everyone all your advice was read and given some thought! I appreciate all the help that was given.

vera I posted this before I saw your post we must've crossed. But thank you for taking the time to write that out and explain it to me! Thats what I'm looking for. I feel if I understand something I'm that much closer to mastering that thing. I am a strong proponent for knowledge is power. Your detailed posts and kind encourging words are more then appreciated. As usual your post is noted on my desktop for further reference.

[kgfly]

Awesome explanation vera :noteworthy

[vera]

I'm in a mood so I'm gonna rattle some more, and the mechanical setup is the subject. You'll find lots of info here about that but there are a couple things that might interest you in the way of details. Here we have a servo arm or bellcrank. These things move in a circular manner. And here we have a pushrod, which ideally moves in a linear manner. Consider the intersection of a servo arm or a bellcrank arm and a pushrod. Let's suppose a servo goes nuts and just goes around and around. The pushrod goes back and forth, but its motion is of a sinewave nature. The motion is greatest and somewhat linear when the angle between the arm and the pushrod is 90 degrees. As we move away from 90 degrees the amount of linear motion of the pushrod is equal to the sine of the displacement angle times the length of the arm.

Let's look at some numbers: sin 10 deg = .17, sin 20 deg = .34, sin 30 deg = .5. Now between 10 deg and 20 deg the change is .17, and between 20 deg and 30 deg the change is .16. So you can see that from zero displacement (the 90 deg meeting angle) to 30 deg we have nearly a linear transfer of motion to the pushrod. Now sin 80 deg = .98 and sin 90 deg = 1, a difference of about .02. So our linear motion to the pushrod goes down the drain at high angles of rotation away from the 90 deg intersection between arm and pushrod. We want the linear motion of the pushrod to be centered around the center of motion of the control that we're messing with.

As you know, servos have splines that lock the wheel to the servo shaft and keep it from slipping. If you have an odd number of splines, then the opposite side of a servo wheel will not fit onto the servo the same way. Let's say we have 25 splines on a servo shaft. Let's mark where a servo arm is pointed. Now lets turn the wheel around and use the arm on the opposite side. That arm is located 12 and 1/2 splines away. But we can't put the servo wheel on the shaft at any fractional values without using a hammer. We can turn the wheel 12 splines or 13 splines but not 12 1/2 splines. With 25 splines around the circle, each spline of rotation is 360/25 = 14.4 degrees. So when we turn this servo wheel around and use the opposite arm, using 12 splines of rotation, it's going to be a rotation of 12 * 14.4 = 172.8 deg, which is 7.2 degrees away from where the other arm was. Now suppose the wheel has 4 arms on it, and suppose we turn the wheel about a quarter turn. Then, we're trying to turn the wheel 25/4 = 6.25 splines. That won't work without the hammer. We can use 6 splines or 7 splines. Using 6, we have 6 * 14.4 = 86.4 degrees. That's 3.6 degrees away from the other arm was.

The point of this ramble job is to show that you may get closer to the desired 90 degree intersection between a servo arm and the pushrod by trying different servo arms that are on the same wheel. You want to get the angle as close to 90 as you can. With a 4-arm wheel that has 25 splines you can get within 3.6 degrees of the desired 90 deg intersection between arm and rod; subtrim the rest. To level the swash adjust the rod lengths. Here's a helpful tool:
http://www.ronlund.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=heli&Product_Code=MA0513

You have to take the head off and slide this thing down on the shaft and almost against the swash. Then you look at the gap between the tool and the swash from a side view and adjust the rod lengths to get the swash level with the tool; same gap all around the circle. You can get the swash pretty close to level without a tool just by eyeballing it but there is a good chance there will be some error. You'll just have to discover that when you fly it and put in some trim to fix it. This kind of fix erodes away at our lovely 90 angle at the servo and it would be better to get the swash level without the trim. If you're crafty you can fabricate a tool. Ok I'm done with my babel... us old people like to babel. :glasses2:

[totalgeek]

vera please babel on! I take nothing from your post but more knowledge from a kind person wishing to help a newbie out. I find your explanation more then I could've hoped for, and it has enlightened me in several ways. I never knew that servo and splines could do so much to make it more difficult for me to fly. As usual your advice is invaluable.

WELL I DID IT!!! :) Almost I hovered almost a whole pack had to touch down once because the copter started coming back towards me very quickly :shock: But thanks to all who have posted in this thread with their kind encouraging words and everyones ability to part knowledge onto someone I feel I owe all of you thanks. Now to do a whole pack and then work on right, left, and :WOW nose in hovering. But first things first I want to do a whole pack of pure hovering. Maybe I should've not gotten Thunder Power 2100mah packs ;) But oh what fun!!!

[kgfly]

Cool! Well done totalgeek. It's a buzz to share your enthusiasm and excitement.

[vera]

My thanks to totalgeek and kgfly.


Well done totalgeek. It's a buzz to share your enthusiasm and excitement.


I wish to second that.

Finless has provided a blizzard of information and there's nothing like a video to get a point across. I can't write anything without noticing that I failed to clarify something and the dandy thing about a video is that you can see for yourself and don't have to rely so much on words. Many others here at the freak have contributed to the bank of info also. There's a wealth of information about putting things together and adjusting and fixing problems. But one of the things that puzzled me is exactly how that stuff above the swashplate works... why is it the way it is. So I thought I'd babel about that in case it's a puzzle to you.

Right away we need to get hold of a key to understanding this thing. The key is, "gyroscopic precession". Check this out,
http://science.howstuffworks.com/gyroscope2.htm

In summary, if you apply a tilting force to a rotating mass, most of the result of that force will result in a tilt which is 90 degrees around the circle in the direction of rotation. Without that awareness the stuff going on above the swash just won't make sense.

Let's start by simplifying things a bit. Your heli would be a good viz aid. Let's imagine the main rotor is gone, and the mixing levers are gone, and the rods from the mixing levers to the swash are gone. We're going to tackle just the flybar. All we have now are the rods from the flybar to the washout levers, and from the washout levers to the swash. The two horns on the flybar - that the rods connect to - are like the two ends of a teeter board in that if one goes up the other must go down by the same amount. Those two horns are locked to the flybar and cannot move independently. If we're going to control collective pitch by moving the swash up and down then we cannot connect the flybar rods directly to the swash because that would push them both up or down and we can't do that without something being loose or busted. So instead, the flybar rods connect to the washout levers. When the swash moves up, one end of both levers move up, and the other end of both levers move down in relation to their mount, leaving the washout end of the rods to the flybar right where they were; the collective pitch is washed out - removed. But if the swash tilts, one lever goes up and the other goes down, a differential motion, and you can see that this changes the pitch of the flybar.

Put the flybar crossways (left/right) to the heli and tilt the swash fore and aft. The pitch on the flybar changes. Tilt the swash left/right. No change. This action won't make sense unless you consider gyroscopic precession. Tilt the swash forward. Notice that the pitch on the left paddle decreases - and of course the pitch on the right paddle increases. So there is a force that's trying to tilt the flybar to the left. Enter gyroscopic precession. The force ends up moving around the disk 90 degrees and tilting the flybar forward. The tilt of the flybar agrees with the tilt of the swash. Mess with the controls and watch the mechanics and get to feel comfortable with how the flybar is controlled. Again, the only stuff we're interested in here is the flybar and the washout levers and the rods from the flybar to the levers and the rods from the levers to the swash. That package of stuff steers the flybar.

Now let's look at the blade holder and its connection to the mixing lever. For now, suppose the mixing lever is frozen - can't turn. So we just have a rod connecting the blade holder horn to the flybar. We'll ignore the other rod on the mixing lever that goes to the swash. Earlier, we tilted the flybar forward. So now put the flybar in the front/back position, blades are left/right. Tilt the flybar down in front and notice that this drives the pitch of the left blad towards negative while the other blade in a positive direction. Here again we have a downward force on the left side - upward on the right side. But once again, gyroscopic force steps in and this force moves 90 degrees around the circle tilting the rotor disk forward.

So now the tilt of the rotor disk follows the tilt of the flybar and the tilt of the flybar follows the tilt of the swashplate. This means we can steer the thing but we don't have any collective pitch input to the blades. So no unfreeze the mixing levers and connect the rod from the mixing levers to the swash. This rod moves no matter if it's because of cyclic pitch or collective pitch, it mixes (or sums) both inputs to the blade. Put the blade in the left/right position and tilt the swash forward. Notice that the front ball of the swash pulls the rod to the mixing lever and rotates the mixing lever which pulls the pitch of the left blade towards the negative direction. And, as the entire swash moves up or down both mixing levers have the same fixed amount of displacement in addition to any cyclic displacement so the pitch all around the circle changes.

Now the inner star of the swash needs to turn with the blades and it would be a bad deal to leave it up to the pushrods to drag it around. That would be an unfair load on the rods and besides the inner star would lag behind where it should be. That would result in a "phasing error". When you apply forward cyclic the rotor disk would tilt forward and right. When the blades or flybar are exactly fore/aft or left/right the balls on the inner and outer star of the swash should be side by side. Something has to drag the inner star around as the shaft turns. Hirobo has a guide that clamps onto the shaft and guides the washout levers and they in turn, with their short beefy rods, are able to keep the inner star correctly phased with the rotor head. The Raptor has the rotor under the flybar and guide pins extend out of the rotor head down to the washout levers to keep them in step, and they keep the inner star in step.

So that's what's happening on the head and if you mess with the controls and watch the happenings on your own heli and keep gyroscopic precession in mind it will all be very clear. :smokin:

[Dave]

Vera,

Great explaination. I have read everything I can get my hands on regarding helicopters and nothing explains it as well as you do here.

What I have wondered about is why do we have fly-bars and large helicopters do not. I have heard the fly-bars explained as sort of a power assist but it seems like large helicopters would also benifit from this power assist.

I guess, in short, I understand why we have fly-bars but I do not understand why large helicopters do not.

[vera]

I understand why we have fly-bars but I do not understand why large helicopters do not.


They can afford to rob some horsepower to run a hydraulic system. Some models don't have a flybar, scale freaks prefer none. Any heli can easily be converted to flybarless. The ratio of movement between the swash and the blade pitch is somewhat geared down, so to speak, with the flybar arrangement and removing it would make the thing more touchy. You would loose some leverage and stronger servos would be necessary. But the flybar also provides some stability, handy for a pilotless machine. For example, suppose a steady hover is going on and you reach out and tip the entire heli - shaft and thus main rotor - forward. Since this action doesn't change the tilt of the swash in relation to the drive shaft, the flybar is not prevailed upon to move, and being a bit of a gyroscope it tends to stay in its plane of rotation, which is now tilted back in relation to the main rotor. This does what it always does, it tries to change the tilt of the rotor to agree with the plane of rotation of the flybar, which tends to restore the heli to its original attitude.

[tmore13]

So let me see if I'm getting this. To trim, I level the swash and leave it that way. When I take off into a hover, I just use a little right cyclic to stop the drift and get up into hover. If I let go of the right stick and cg is good and swash it level, I don't have to constantly add right cyclic?