Hello Keith,

Well, could a servo worn-out in this little time?
I think I about 125 Flight in total on this servo. ( not even one year old )

I’ll try later to tighten them a little, and see what will happened.

And could you explain to me what a dead band is. (Means)
I think that it has to do with the range off the servo movement.


Regards,
Danny Koolman
www.arubarcclub.com

I am running my OS 1.60 FX's with OS 1.40 RX pumps and OS 140 Mixture carbs on my Impacts. A couple of time I have left teh mix screen open and when I pressed the timer button I cleard the carb to mix servo settings. B=Notthat that was too big a deal because I keep a full copy in and adjacent memory, but it did play on my mind a bit as I drove to the field today.

While the "old but keen guys" were tiring themselves out I swapped in a standard OS 1.60 FX carb, Fitted a remote needle with a 4-40 head on it and drilled a tiny hole to allow for idle adjustment etc.

You set the idle screw on an OS 1,60 withe carb closed. You screw it in till it stops and then back out 1.5 turns as a start point. Then you set the main needle at around 1.5 turns when using a pump. It started up just fine. The arm on the std. carb matched the mix carb throw perfectly. the engine then ran way too fat. even with the needle all of teh way in it would not run at WOT.

OK, put on thinking cap!....... Must be a needle problem? Did the usual checks and then looked in the spares box. I compared the needle with four of the spares that were in the box. They all looked the same, but one had a longer tip. Then it dawned upon me that I had used an OS 1.40 needle. I have a bunch left over from the original 1.40 pump backplate conversions. The OS 1.60 needle was put in the engine and it ran like a watch.

I did notice quite a few diffferences.

1. 200 less rpm with the Mejz 18 x 12.
2. A better idle - no fluctuations
3, A leaner mid range - The curve on the mix carb 10X graph is always richer in the mid 40% for my 1.60's
4. Still ran solid but a bit louder.
5. Did not quit once top end was set using a tach.

You save the weight of a servo, leads and pushrod. You add the weight of a neelel and bracket.

You also get a simpler system to operate.

I still prefer the mix carb. I am hearing that Webra mixture carbs are being turned down to 15-mm OD and used on the 1.60's with good results. You need to tap them for 3.5-mm screws.

Regards,

Eric.

Eric, what RPM are you getting on the Mejz; and does it meet AMA sound or FAI?

Thanks.

I run them around 7500 rpm. They are very quiet at this speed. The engine "mechanicals" are louder than the prop. The pipe is an ES medium length OS 1.40 with a Karl Meuller header.

The prop is lighter than the APC's If it is blowing a gale I switch to an APC 17 x 13. That runs at about 7800 rpm and is way below the limit.

Regards,

Eric.

Danny, How quickly they wear out will have a lot to do with how much vibration they are under, 125 flights seems a little low, but I'd say it's not out of the question that they could have worn to the point you have oscillation.

Has this servo been in this plane for 125 flights? If so, how long has it been oscillating?

The dead band is the neutral area when the servo is centered. The servo is constantly trying to keep the rudder from blowing right or left and the dead band is the area that the servo considers the center. So if the servo has a dead band that is too narrow it will constantly be fighting itself moving the rudder back and forth trying to hit that center point. Horizon can adjust this dead band when it is too tight.

Troy Newman has some good threads on JR servo life and repair as it relates to pattern planes here on RCU. You might try doing some searches to see if you can find them.

Keith B

Been working frantically on my Impact over the last 6 weeks.
Test flew it a week ago, and have been out a number of times since. All going very well so far, with 160DZ in the front. No signs of any rudder problems (touch wood !!!). I've been watching this post through the whole build, and pretty much took on board all of the mods listed. I had to rehinge the rudder to make it removable, and now that its in the air, I'll make a balsa one to remove some tail weight. CG is about on the back of the wing tube, if anything I will move it slightly foward. Been great weather for trimming this week, so I won't really be happy with the CG until I fly it in a howling gale.
I'm running the wing and stab a zero, as best I can measure. My meter is a Robart one, so unable to measure 0.25, but from my trim flights so far, I have no Elevator trim and the downlines are perfect. If anything it could do with a touch of upthrust. I have both wing and stab adjusters, so can tweak these. I'm slowly adjusting the wings to get the aileron trim sorted out, but there is only a fraction of trim required to keep it level.
Needs more right thrust. For now I've got a small amount of right rudder mixed with throttle to sort this.
Its not much lighter than my PL Smudge which was right on 5Kg, but for some reason it feels a lot lighter in the air. Bigger wings ? More fuse volume ... dunno, but certainly happy with it so far.
FB

Beautiful airplane there Frazer.

I hope you knock 'em dead in France this year. [sm=wink.gif]

Looking good down there :-)

As regards the CG - I tried 7 different positions yesterday and finished up with the following. (I moved the battery all around the plane to do this)

Mine likes the CG to be right on the center of the wing tube. It snaps better, stalls into the spin very cleanly (No floating around). The rolls are just as easy andi t feels better to hold a bit of down in inverted flight.

Please note that when I say on the center of the wing tube, I mean with the wing off.

It is so much easier to use a reference point on the fuselage with the wing off. For example, if you change the rudder you can get back to where you were without assembling the whole plane. The wings don't change. They do move the CG back a bit, but it is the same amount every time.

Regards,

Eric.

What a handsome bloke there.... Sheepboy!

We had an IMPACT flying day at our local field today. George Asteris had his new model with a YS 1.60 DZ. What a great combination. This motor took the IMPACT up and out of sight. It got a bit windy which sapped a lot of vertical power in the humpty with the positive snap going up. Not for the YS 1.60! This was a treat to watch. I am looking forward to seeing how the various combinations of power plant and IMPACT will fair at the Nationals this year.

It was also a treat to watch someone else''s IMPACT fly. This plane does present well and goes through the FAI schedule very comfortably.

Regards,

Eric.

Hi Eric!

It was good to hear about a setup that I'll be using -- do you happen to know what prop George was using with his Impact/1.60 DZ?

Thanks!
Tom

Regarding CG, I recently maidened my Impact with the CG about 1/8 to 1/4 behind the wing tube (wings on) and it felt very nose heavy to me. I'm really surprised that everyone seems to think that the best CG ranges from the back of the wing tube to 1/4" back. Perhaps this has to do with my incidence settings, which need adjustment as of yet, but at this CG the plane definitely had a nose heavy feeling when inverted and doing rolls.

I'll play with the incidence and give additional feedback as I get time.

Keith B

He was using a 17 x 12 APC but it was not enough prop according to my ear and his comments :-) I'll let you know what he settles on. It was fast BTW

Eric.

Eric,

I saw that you reduced the size of the counterbalance on your Impact. Did you ever consider to cut it off completely?

Regards,
Knut

I did think about it. BTW - I did not reduce it by much. The reason I left it on is for a visual check. You can very quickly check to see if your rudder trim is correct before you take-off when the counter-balance is used.

Also the rudder on an IMPACT is very strong. You can easily do KE loops etc. But it is "soft" around center so I did not want to reduce its effectivenes in the slow rolls etc. I finished up using 9% and 15% expo on the rudder.

Regards,

Eric.

Another good prop to use is the 18x10 pn. Great prop!!!!!!!!!

Robert your running a 1.60DZ right? What RPM is that prop turning, is it loud?

The 15.5x12 4 bld is pretty nice.

Update on the "Soft around center rudder".

I was comparing rudder notes with George Asteris during a flying session today and he was even thinking about making a fatter and deeper rudder. On an impulse I spoke "Futaba" and said to George, "Why not try positive expo?" [In my native JR it would have been negative expo]

George took his mighty 14 MZ and smote that rudder with a whacking great chunk of 5% +ve expo.

One flight later the rudder was no longer an issue. It was now behaving with authority and delivering corrections around center that felt right.

It may not work for you but it is easy to set some on a switch and just try it for fun.

My expos are now at zero..

Regards,

Eric.

I decided this the way to go. After cutting the leading edge off of the rudder back to the balsa "false leading edge", I found I still didn't have a large enough gap between the fin and the rudder. I can cut off part of the fin or I can cut back the rudder some more which will essentially remove the balsa leading edge which will then require replacing. Did anyone else go this route and how did you end up doing it?
Regards, Jim O

On my second Impact I have gone the bevel on both sides approach using the rudder that came with it (rather than building balsa or foam one at this stage). I took the leading edge off the rudder back to the balsa former, and took about 5mm of the back of the fin/fuz to allow for the double bevel. I haven't flown it yet, but it all fits together neatly enough.

I thought about taking more out the front of the rudder (and lowering its size and mass behind the hinge line, while also making it easier to get secure gluing of the rudder control horn above the stab rather than below), but was unsure about the impact of an even bigger counterbalance (I don't 100% rule this out if the flutter debate) and thought this would likely be more work than building a new one. So I took the easy route!
David

Jim on my rudder I trimmed the fin back to have the rudder fit.

Thanks guys. I had pretty much decided to trim the fin too and it sounds like we all came to the same conclusion. I beleive that will put the hinge line in essentially the same spot but with better hinge support.

Jim O

I need some Impact trimming feedback.

I've been playing with the CG and incidence on my Impact. The plane feels nose heavy to me when inverted; yet I already have the CG as far back as I think it should go. In fact, at one point I had it probably 3/4" behind the wing tube (wings on when measurement was taken). At this location it didn't stall turn worth a darn, in fact, it was very hard to stall turn. Yet even at this CG if I pulled a 45 deg. upline and rolled inverted it would immediately start dropping the nose unless I got right on the down elevator. It seems to start dropping much more rapidly than my Aries.

On the incidence for the main wings I started at what I measured to be +0.25 relative to the stab. At this location it pulled to the canopy quite badly in vertical dives, so I've reduced it probably 1.5 to 2 turns down (gator adjusters). The vertical dive is better, but still not straight down without mixing about 2%-3% down elevator on low idle.

As to the down elevator at idle, the problem with this is if I'm cursing along in level upright flight and pull back on the throttle the plane will want to descend more quickly than I'm used to. Normally one of my trim tests is full throttle upright level flight then go to idle. Ideally the plane should stay on the same track until it begins to loose momentum and gradually start falling. With the throttle/elevator mix it will start dropping right away.

Thanks for any advice that you many have.

KeithB

Hi Keith,

What incidence are you running on the stabs? Sounds like you might have + on it to me.

I run 0 degrees incidence on my Impact stabs with +0.25 on the wings and 0 downthrust & 3.5 degrees right thrust. Engine is YS 140lm with 15x12 APC prop & 30% Wildcat 3DLV fuel. C/G is on the wing retaining bolt and can confirm that the model feels very locked and tracks great.

A golden rule that I was taught right from the start is "change 1 thing at a time", trimming issues can bog you down if your not careful and I know how frustrating it must be, hang in there buddy!

Hope my set-up details help.

Andy.

PS. Done lot's of snaps now with the Impact after repairing my fuselage and installing the ladder crotch and I am pleased to confirm it's STILL in one piece!

Andy P., Keith
I met Billy Meadows at our local field today to compare my Older Impact to his brand new just received Impact, we wanted to see what the different was. He was told that the chin cowl area was larger and wingspan was decreased for better snaps, wingspans are the same and fuse is identical except for landing gear cut out are a little lower, and fuse was about an inch shorter. The thing that stood out was the main wing tube was moved back about 30mm, this was just looking with my eye but it was a very noticable amount. This explains why my CG is further back then some I have seen reported here. My cg is at least .5 inch behind trailing edge of the main wing tube and possibly more, feels great, still requires slight amount of push for inverted but not much. When I had it balanced on the trailing edge it felt very nose heavy. My stab is at 0 and main wing +.25, dives straight as an areo, about 5% mix for pitch to the belly with full ruder and about 1% for a very slight roll in knife edge.