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HomeAircraftHelicopterHelicopter Main Discussion › What is a good pitch curve for an 800 size gasser?
08-20-2018 07:03 AM  35 days agoPost 1
OneHoof

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Cold Spring, Kentucky

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What is a good pitch curve for an 800 size gasser?

I have a new to me 800 size gasser, but don’t feel the pitch curves are set right.

I don’t have a pitch gauge with me here in Washington, but just eyeballing it, mid stick looks like zero pitch, and max stick looks like around 10 or 12 degrees pitch.

Ideally, for sport/scale flying, don’t you want around 6 degrees pitch at mid stick?

The previous owner used to always do hovering autos to land, because apparently landing with power it would land kind of hard.

It is equipped with a GV1 governor, so the rpms come up to 1,300 rpms at 30% of up collective, so it is important that I get the pitch curve set right.

My last test flight it seemed like the rpms were high, with not enough pitch, at the point when it should have been taking off.

Any set up tips would be really appreciated. Thanks.

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08-20-2018 09:03 AM  35 days agoPost 2
Andy from Sandy

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Bedfordshire, UK

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The pitch range of the model is up to you and the limitations of the mechanics.

From what you state the mechanics have been setup for zero pitch at mid stick and I am guessing you have a linear pitch curve in your transmitter.

But this is old school with flybarred head.

What is the head on the model, what electronics, etc.

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08-20-2018 12:38 PM  35 days agoPost 3
MattJen

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UK

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As Andy Says, it depends on how you fly, I fly scale on a 15Kilo model,
my pitch curve is -3 bottom stick, +6 midstick, +12 top end..

that is an average scale curve with the head speed you are running.

All The Best

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08-20-2018 01:46 PM  35 days agoPost 4
Richardmid1

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Leeds, England

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If the governor is working it shouldn't have sounded high, it should have governed the head speed to what you set it at. Did you tacho it?

If it is setup for -12/12 pitch with zero center and you want -6/12 with 6 center then increase the mid point to 75% and the low point to 25%. At least that is the easiest way.

60% of the time, it works every time!

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08-20-2018 01:54 PM  35 days agoPost 5
fastflyer20

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N. Tonawanda, NY

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Proper set-up:
In normal curve, turn gov off. You can do this in the RPM setting by lowering setting, it will turn off. Gov will remain on for other RPM settings. Set up a V curve in TX for idle ups, try 100 - 35 - 100. This will allow the GV1 to stay engaged while in idle up and is used as a backup if gov fails. Use normal curve to warm up engine and advance to mid stick, then flip into idle 1 where gov will take over. An 800 gasser should land super smooth if throttle, gov and pitch are set right. Make sure pitch matches when flipping from normal to idle ups.

One way to check if gov is working and you don't have a tach: set both idle up V curves in TX identical, set 2 idle ups in GV1 to different head speeds. Listen for an RPM change when flipping between idle ups. Make sure the gear ratio is set correct in GV1, they are very accurate when set up correctly.

It is typical to set max pitch on a gasser that allows just a bit of head speed decrease at max pitch. Use normal throttle curve, slowly advance to full throttle. It should not bog, but lightly load the engine.

Tom
CAUTION - my posts are based on my experiences, yours may be different.

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08-20-2018 02:39 PM  35 days agoPost 6
RM3

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Killeen, Texas - USA

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you have potentially two problems... and it happens alot with gassers running GV-1s..

the GV-1 has a hidden menu with two settings that are critical to set if you want a gasser to run properly. the two setting are LLimt hover and LLimit idle up. if these two are not set properly the engine will rev up past the RPM set point, the other indicator is the short drop in RPMs when going from normal to idle up... sounds like it wants to die then it picks up speed.

Now if your setting it up for sport, Im assuming you plan on flying some maneuvers that involve inverting the model, like loops, maybe rolls, perhaps inverted hover... and you most definitely will need negative pitch for Autos.. so the pitch curve on most 700 and 800 class gassers is: -10, 0, +10 degrees on idle up and on normal is -5, 0, +10....

either way you always want to have some negative programmed in there should you find yourself needing to auto the heli down safely... without it your guaranteed a dirt nap.

Headspeed is usually around 1600 tops on an 800... but I have seen 1800 for 3D work well on electrics like the Trekker... the general Idea is to allow the heli to hover a hair under 3/4 stick and that will determine what the headspeed needs to be at that point... (it should hover inverted the same amount under mid stick too when in idle up).

Keep in mind not everyone uses a straight line pitch or perfect V- curve for 3D/sport... this works on my electrics... but on all my gassers the curves are more "S" like due to the engine capability... on scale the curves are definitely flatter to prevent collective jumps.

Lastly dont rely solely on the GV-1... you should be able to turn off the GV-1 and the heli should be setup to fly on TX throttle curves for both normal and idleup... this is a backup should the GV-1 fail for any reason...

showing a preference will only get you into trouble, 90% of everything is crap...

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08-20-2018 05:32 PM  35 days agoPost 7
MattJen

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UK

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I thought he wanted a setup for Scale ?

If so you wont want zero in the middle.. unless your doing Scale Aerobatics like the Reds Bull Heli..

All The Best

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08-20-2018 06:14 PM  35 days agoPost 8
doorman

rrProfessor

Sherwood, Arkansas

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SETUP
Even with the GV-1 I agree with MattJen... this is an old school machine and not designed for full on 3D.. great sport fliers though!!!
I fly my pod and boomers with -12-0-+12 just to keep my thumbs moving, but all my scale machines hover at half stick (5 - 6 deg)

Stan

AMA 2918-Team Spin Blades,,Castle Creations, Unique Aircraft

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08-21-2018 12:46 AM  34 days agoPost 9
OneHoof

rrApprentice

Cold Spring, Kentucky

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All of my equipment is home in Greater Cincinnati.

I will probably have to wait until I get home.

I think there is more likely to be someone who can help me in the Greater Cincinnati Area.

I plan to leave Washington State on Thursday.

Getting this heli set up will be easier once I have my pitch gauge.

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08-21-2018 12:47 AM  34 days agoPost 10
OneHoof

rrApprentice

Cold Spring, Kentucky

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This heli has 810 mm blades, and weighs 18 pounds, so I don’t plan to do any inverted flying.

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08-21-2018 04:41 AM  34 days agoPost 11
RM3

rrElite Veteran

Killeen, Texas - USA

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You still need some negative pitch if you plan on doing any autos... which I highly recommend learning. Especially on a big heavy 800 gasser. Many heli pilots don’t know how to and pay a hefty price when their engine dies mid flight

showing a preference will only get you into trouble, 90% of everything is crap...

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08-21-2018 09:18 AM  34 days agoPost 12
JuanRodriguez

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The Villages, Florida

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RM3
You still need some negative pitch if you plan on doing any autos... which I highly recommend learning. Especially on a big heavy 800 gasser. Many heli pilots don’t know how to and pay a hefty price when their engine dies mid flight
Absolutely agree..... years ago I learned how to auto on a Bergen gasser. At about 12-13 lbs and 710 semi-symmetrical blades, it was a pleasure to auto with about -4 ~ -5 degrees ....

Been there, done that and old enough to know better.....

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08-22-2018 01:02 AM  33 days agoPost 13
OneHoof

rrApprentice

Cold Spring, Kentucky

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This was my second, high, forward flight autorotation with my Vario Benzin Acrobatic, in 2011.

Not perfect, but it survived both. They are more challenging with a non driven tail.

I had a real engine failure in a hover at about 40 feet up. I did a good auto and saved it.

I am great at hovering autos. But the forward flight ones still make me nervous.

Watch at YouTube

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08-22-2018 01:08 AM  33 days agoPost 14
OneHoof

rrApprentice

Cold Spring, Kentucky

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This was my first forward flight autorotation. Circa 2011

Watch at YouTube

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08-22-2018 01:14 AM  33 days agoPost 15
JuanRodriguez

rrProfessor

The Villages, Florida

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The problem I see with that auto is that once you switched into throttle hold, you lowered the nose and sort of dove it in.... that’s why you had excessive speed at the bottom and difficulty stopping the forward motion..... with a nicely controlled auto , you should be able to stop the forward momentum and bring the heli into a hover for a few to several seconds....

Next time you practice, pull the nose slightly up when you initiate the auto and you’ll find that as you fly it down , the blades will actually increase in RPM and the heli will descend at a very comfortable speed with plenty of head speed left for the flair and hover followed by the landing.....

Been there, done that and old enough to know better.....

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08-22-2018 02:49 PM  33 days agoPost 16
Pistol Pete

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Seffner, FL

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OneHoof
Getting this heli set up will be easier once I have my pitch gauge
Check out..."RC-Heli-Pitch" app in the PlayStore for android.

~~Enjoying the hobby one flight at a time~~

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08-22-2018 03:46 PM  33 days agoPost 17
RM3

rrElite Veteran

Killeen, Texas - USA

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seriously... an App?

what ever happened to eyeballing it?

whats next the insta-piro flipping hurricane app?

showing a preference will only get you into trouble, 90% of everything is crap...

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08-22-2018 05:06 PM  33 days agoPost 18
MattJen

rrElite Veteran

UK

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LOL
There is an app for everything now ha ha..

Well done on the Auto, take some guts with a Gasser, you saved the model and got it down, Nice flying. Like the full size, practice practice

Good luck.

All The Best

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08-27-2018 08:18 PM  28 days agoPost 19
OneHoof

rrApprentice

Cold Spring, Kentucky

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Okay. I finally made it home to Northern Kentucky/Greater Cincinnati.

The links that were on there could not safely unscrew enough to give me the -5 +6 +12 pitch curve I wanted.

So, I replaced the ball links with the Vario ones.

Now I have a -5 +6 +12 pitch curve that I am used to.

My only concern is the Vario plastic links seem a little loose to me.

When poping the one on, I guess I pushed too hard, and it slide off the ball, inside, towards the pitch horn.

I am trying to find the right size pitch change links.

Is there a rule of thumb test, to know if your pitch links, are right enough on the ball or not?

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08-27-2018 08:27 PM  28 days agoPost 20
RM3

rrElite Veteran

Killeen, Texas - USA

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OneHoof
Is there a rule of thumb test, to know if your pitch links, are right enough on the ball or not?
if the links can move left or right inline of the axis with the ball they need to be replaced... New links should be just tight enough that they hold themselves on the ball but can be easily spun around the ball with very light finger pressure, but no lateral slop. This is where a good ball link sizing tool comes in. If you can pull them off without link pliers or easily by twisting them off... time to replace.

showing a preference will only get you into trouble, 90% of everything is crap...

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