Have I made a mistake?

[bearwood]

I am having real problems getting my machine to get a stable hover in any sort of breeze.
My set up is a Z20-1470, 13 tooth on motor, 600 tooth front gear, 61 tooth main gear and 19 tooth one way gear 500mm wood blades.
Now I could have sworn that when I bought this motor I had to go to the 13/60 tooth combination to get the headspeed down to around 2000. But when I just checked the Hs calc at http://www.ezfly.se/hscalc.htm it calcs at 1400 which I have real trouble believing cause this thing climbs like a home sick angel.
Anyway getting back to my problem, I have been bumping up the Throttle curve to 82% (trying to get to 85%) at the 0 pitch or 50% position. What I have noticed is a dramatic increase in the rotor noise from the 75% I was at, but also the heli is very susceptable to any wind velocity changes. Tonight I flew 3 packs and the wind was non exixtant to a slight breeze and the heli would climb vertically up to 20 feet quite quickly with each puff. I have to reduce the throttle a resonable amount before the heli starts to descend then I have to feed in almost as much as I took out to arrest the descent. Now I am expecting to have to manage the throttle in a wind but I thought the heli was heavy enough to hold still in a minor puff.
What can I do to tame this beast? Will the Trex 400mm flybar or Raptor flybar help. I have fitted some collets out at the paddles but no decernable difference. Should I downsize the motor to the Z20-980 and standard gears? Would 550mm blades help? I am thinking that with the increased HS that small pitch changes have greater affect. I guess I can refit the original motor (god I'm going to be sick :)) and try that but hopeing one of you more knowledgable gents may have some better ideas.

[Graeme67]

Gday Bearwood,

I am certainly not in the Knowledgable gent category but I can tell you that I have experienced that as well. I am only a newbie & this is my first heli & let me tell you the first time I flew it in the wind I really had a fight on my hands. The heli would just climb beyond belief, & like you mentioned I would nearly kiss the ground before I could get the collective back up to stop the decsent. I was left wondering what all the talk about the Hurri being nice & stable in the wind was all about.

I don't know what level your at with your flying but for me I put it down to collective control. For me that has been the hardest thing to master. I had 6 flights today in mild 15knt breeze and had no where near the trouble I have had. I am getting better with the collective.

I have also given idle up a try and I found the extra headspeed certainly made the heli more of a handful. I have gone back to normal until I feel comfortable with the lower headspeed.

So IMO I don't think anything is wrong with the heli - my skills have just got to improve

Cheers
Graeme

[mjdee14]

Bearwood..

What your describing in a "slight" wind does not sound normal....

it may be the way you have your T and P curves set.

Why not post your radio type and you Th and Pitch curves in Normal....

I also calculate the headspeed at 90% should be about 1982 using the headcalc....

100 less at 85%...

Are you using any Expo to soften the stick ? are you using 0 pitch at mid stick?

If you using a pure linear pitch curve it just might be to sensitive...and although you think it's all wind, it may be added collective also.....

I have initially had a heli so sensitive it did exactly what you describe....once dialed in with some expo and reduced rates in norm it was much better.

I run about 50% expo and 80% Dual Rate in Normal. Once you master the hovering part, it's much better to fly in Idle up. In Norm you could accidently reduce throttle too much and kill the motor at the wrong time. In IU your only controlling blades pitch.

Post your settings and lets see what we come up with.

If you have an experieinced heli flyer available have him check it out...

[Madedon]

Bearwood..

I run about 50% expo and 80% Dual Rate in Normal. Once you master the hovering part, it's much better to fly in Idle up. In Norm you could accidently reduce throttle too much and kill the motor at the wrong time. In IU your only controlling blades pitch.



Hi mjdee

Why we should use the and 80% Dual Rate in Normal mode?

I m experimenting with expo but I did not figgure out why we need the dual rate..

Any quick explaination

Thanks

[mysticmead]

dual rate really isn't needed on heli's...it's useful on planks though

[bearwood]

Ok thanks guys,

Radio is a DX7.
Pitch Curve: 43 - 52 - 100
L 1 2 3 H

Throttle: 0 - 82 - 100
L 1 2 3 H

Both settings at Norm with no exp on the TC or PC. I have 20% exp on Elev and Aile only.

I don't see how expo will help in the collective because its the uncommanded rises that irk me. The control in descent is for me to manage and I just feel if the heli didn't change altitude so much then it would be easier to manage. I really am surprised at how much altitude change occurs will a small change in wind velocity. I must confess that keeping the heli in one place is difficult when it takes off like it does, maybe more expo will help the cyclic control. I'll try that next time out - hopefully this evening.
I went out a few days ago and it was blowing what turned out to be 20-25knts so it was a real handful and thats understandable as I was out of my depth. But yesterday was late evening and the wind was a still with mere zephyrs on the ground. This seems to be worse when i am out of ground effect (just above head height).

mjdee, I wasn't entering the motor KV so hence my results :arggg:

Graeme, yeah practice make perfect. I keep telling my kids that;)

[MartinS819]

82 at midstick is too low for throttle, you want to be 90-100 by midstick.
Try 0-50-90-90-90 or 0-50-100-100-100 and 100 flat for ide up.

For pitch try 40-45-50-75-100 normal and 0-25-50-75-100 for idle up.
By having 52 at mid you have positive pitch at 82% throttle and you're probably lifting off at around 85% throttle with the pitch higher than it should be. I'm guessing because of this your headspeed is too low and you can't have good control with it that low. I'm running 2k right now and she handles perfectly fine in the wind. Was out today in 10+ mph wind and held a good inverted hover for maybe 20-30 seconds.

[mjdee14]

Hi mjdee

Why we should use the and 80% Dual Rate in Normal mode?

I m experimenting with expo but I did not figgure out why we need the dual rate..

Any quick explaination

Thanks

The dual rate just cuts down the total throw available in cyclic...I don't think it affects pitch and I'm not sure you would want it to. So although you are moving the stick say 25% of it's travel....instead of 25% servo movement, you only get 20% (25% of 80%) in normal mode you don't need max throws becuase your not doing radical manuvers...your trying to hover or keep it smooth. In the beginning I flew in Normal....no more...Idle up only...much better.

A properly set up heli in normal should not jump around with small pitch changes and with enough headspeed my 550 handles wind beautifully. As mentioned the more practice the easier it gets...

Remember, everyone has a different feel and style of flying....the settings I have described seem to work ok for me.....when I want full/max throw I use IU2 which has no DR and less expo....expo does not have that much use in IU2 as you are using high servo movements, but when you just FF it softens the cyclic around middle stick.


A lot of people post pitch curves but keep in mind it all depends on how you have your servos and head set up....
if middle stick is not 0 pitch...then 50% is not either. You need to set up your heli with a pitch gauge so you know that you have 0 at mid point...and also know what you are getting at 0 and 100.

[MartinS819]

Yeah can you post your blade pitch's at low, mid and high stck(with 0-25-50-75-100 pitch curve)? I'm curious as to what you're set at. You probably want 0 pitch at center and +-10 at full pitch since you're just starting out. Then you can use your swash menu to change the pitch settings and get more pitch dialed in. I have +-12 right now and it works fine.

BTW did you set the heli up at 50% in your swash settings per the manual? If you have your collective mixing set too high, it could act the way you're describing.

[bearwood]

Ok I have been out all morning and now we have friends coming around so no chance to test anything but as the pitch curve appears to be common element I am going to tear down the head and redo it from scratch.
After that I will post the actual pitch of the blades in relation to throttle and see how it flies.

[bearwood]

I pulled the head down and found nothing really significant. I removed the adjustable link that Finless recommended and refitted the fixed Gaui link.
I now have 9 degrees +/- full travel with a flat pitch curve 0 25 50 75 100. 0 degrees pitch at 50% throttle.
I have set the Norm pitch curve 40 - 46 - 100 which translate to -2 0 9 degrees. It was getting late so I stopped there as I couldn't figure why the 0 point had moved. I was having some difficulty keeping the flybar level whilst trying to measure the angles and thought it wise to stop before I had a humour failure.

[istandalone]

as far as locking the flybar, i just use two toothpics. one wedged into the hole in the seesaw on each side. this keeps it steady enough to get consistant readings. i was using snipped and bent pieces of linkage wire but they gouge the aluminum.

[mjdee14]

. It was getting late so I stopped there as I couldn't figure why the 0 point had moved. I was having some difficulty keeping the flybar level whilst trying to measure the angles and thought it wise to stop before I had a humour failure.


Try playing with the hover trim switch, (ifyou have the DX7) it will adjust trim around the midle stick position and maybe get you back to 50% at 0 pitch.

I use an allen wrench...I think a 2 1/2 mm if fits between the seesaw and the head and locks the flybar in place.

[bearwood]

Got out for a fly this evening and it is a lot better. Hover is a lot more stable and the wind has negliable affect now.On second battery getting the trim corrected the tail blew apart - not real impressed, no damage apart from no tail. Heli was in a 2 foot stable hover prior to landing when it just went bang, piroted 180 degrees and landed on its skids. One blade went sailing past me 30' away and the other stuck in the ground below the heli.Pics attached. The hub spigots have just sheared. The CNC tail unit is a Sonix unit http://www.takeoffandland.com.au/product_info.php?products_id=2584&osCsid=74afe0e3515779af99bfbca7a48c2c63
which is very similar to this one http://www.helidirect.com/product_info.php?cPath=322&products_id=5869 I'll start another topic to show this failure. I have to say I have cut the grass with this tail a few times but that is all.

The toothpicks work a treat, didn't like putting allen keys in there after one got stuck.

Setup ended up be PC 40 - 50 - 100 and TC is currently 0 -83 -100 and working towards 85% at mid stick. Currently running 40% expo on Ail and Elevator

Thanks to all.

[Graeme67]

The CNC tail unit is a Sonix unit

Hi Bearwood, I have looked at those units and when I realised they were'nt Gaui I wondered about the quality. It's good to find out! I'm up to 84 flights on the standard plastic tail with no problems.

Cheers,
Graeme