HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jun 30, 2012, 08:18 PM
Registered User
desolas's Avatar
Joined Nov 2010
9 Posts
Help!
Trimming issue; Seagull Edge 540 rolls right on hard loops.

I have a Seagull Edge 540 46 that I recently put a Saito 82 in for more performance and power, the OS 46 just sucked.

Over the course of the last few flights I have been getting the trim and CG where I want them, adjusting thrust angle, and generally getting it where I like and good for aerobatic flight and 3D - as well as a plane like this can 3D anyhow.

Only issue I have come across is when I do any type of loop using full elevator the plane will cork screw to the right. I have put a incidence meter on the elevators and made sure they are symmetrical at full travel, I have tried turning down the elevator travel - which helps some but to smooth the plane out I end up doing these massive loops and the plane has a hard time taking off from lack of elevator.

It will cork screw when it as the top or bottom apex of a loop, similar to a tip stall. But if I stay on power it will consistently loop to the right down the entire field at a good speed.

My left/right balance is almost spot on; about 8-10g heavy in the right side. Perhaps this is the issue? I am going to get my L/R balance spot on and try again.

I am pretty sure it did this with the 46 as well, but I removed that engine before I had fully even trimmed the plane in.

Another thought is just the size of the engine is too much for the airframe and this is a symptom of that. I can fly around the issue, I would like to learn more though and figure out why it is happening - even if it will always happen.

I experimented with aileron to elevator mixing, and it helps during the hard moves but it hurts it during normal flight - it makes a loop ugly and roll to the left instead. I have also tried left thrust angle in the engine to see what effect that had and it did not change it at all.

Thoughts?
desolas is offline Find More Posts by desolas
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 30, 2012, 08:48 PM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
746 Posts
You are putting the wing past critical incidence. (Your wing is stalling and there is no lift) This may be more noticable because you just shifted CG.

There is a lot of power back there.... (in the elevator)

Fly it on low rates with less throw. Use high rate for high alpha maneuvers.

You will notice if you use left rudder it will probably stop the roll... but the wing is still stalled.

It is snapping due to the torque of your engine, continuing forward due to inertia, and dropping fast because of gravity.

The answer is to cut the throw on the elevator.

Brian
EscapeFlyer is offline Find More Posts by EscapeFlyer
Reply With Quote
Old Jun 30, 2012, 09:07 PM
Registered User
Jacksonville Fla.
Joined Mar 2007
2,219 Posts
what is your power setting at the top of the loop? if you pull more to one side with power on and not so much with power off it could be your thrust angle....
jetmech05 is offline Find More Posts by jetmech05
Reply With Quote
Old Jun 30, 2012, 10:14 PM
Registered User
Joined May 2012
432 Posts
Pretty much everything Brian mentioned. A loop is supposed to take up all of the sky anyway. It's a smooth, large movement, not some choppy little snap. Well with an Edge anyway. I use a throw meter to set up all of my planes and my extras elevator throws are at about 10 degrees, that's about it for an IMAC or pattern plane. 3-D is another story and I set up about 28 to 30 degrees of throw.
If you have a radio that will do it you can slave the rudder to the elevator so it compensates for the roll out. That is one of the reasons for mixing.
Gray Beard is offline Find More Posts by Gray Beard
Reply With Quote
Old Jul 01, 2012, 12:33 AM
Registered User
desolas's Avatar
Joined Nov 2010
9 Posts
I think it does behave like the tail is stalling the more I think of it. I will experiment with various throws and reassess it and try to post a video if it continues.

I might be just flying the tail too aggressively, but the loops are often not that aggressive to make it happen however, but I might be feeding in too much stick after the apex.
desolas is offline Find More Posts by desolas
Reply With Quote
Old Jul 01, 2012, 01:21 AM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
746 Posts
desolas-

I like the avatar btw!

Brian
EscapeFlyer is offline Find More Posts by EscapeFlyer
Reply With Quote
Old Jul 01, 2012, 02:04 AM
lost in the addiction of flyin
furballll's Avatar
Canada, BC, Kelowna
Joined Dec 2009
798 Posts
single or dual elevator servo? solid connection at elevator or is it using a metal joiner? could be flexing causing one side to travel more than the other? a bit more info is needed, but likely you are getting into the dreaded tip stall.
furballll is offline Find More Posts by furballll
Reply With Quote
Old Jul 01, 2012, 02:19 AM
Registered User
desolas's Avatar
Joined Nov 2010
9 Posts
Quote:
Originally Posted by furballll View Post
single or dual elevator servo? solid connection at elevator or is it using a metal joiner? could be flexing causing one side to travel more than the other? a bit more info is needed, but likely you are getting into the dreaded tip stall.
Its dual elevator, metal pushrod from servo, matched servos. I have spent a good amount of time making sure that they are moving at the same rate, and distance.

Playing with it tonight I see perhaps one servo isn't holding as well as the other, it takes some force but the servo stalls. I swapped sides and am going to see what happens in the morning.
desolas is offline Find More Posts by desolas
Reply With Quote
Old Jul 01, 2012, 02:40 AM
lost in the addiction of flyin
furballll's Avatar
Canada, BC, Kelowna
Joined Dec 2009
798 Posts
well then if the theory is correct it should go the other way if the sevo stalls. i recently test flew a seagull 232 that had dual elevator servoes, one traveled more than the other but only at full throw. the plane made the best full up snaprolls ever, no other input needed. the owner of the plane was fortunate i was on the controlls for that flight as it needed alot of help before i got it sorted out.
furballll is offline Find More Posts by furballll
Reply With Quote
Old Jul 02, 2012, 01:15 AM
Registered User
desolas's Avatar
Joined Nov 2010
9 Posts
Curses, it did not cure it at all. I even tried adjusting the elevators separately to try to counter the effect and it really doesn't seem to help until they are considerably deviated from one another; then I have to counter with aileron trim to make it fly semi straight.

Playing with various CG changes and dual rates I think this plane just stalls the tail and rolls towards the torque when it does. It's a mediocre airframe and I think I will just fly it for a few more gallons and get something a little better.

Comparing it to a few other 46 size planes flying I am just expecting way more out of the tail than it is capable of. I am chalking this up to the pilot.
desolas is offline Find More Posts by desolas
Reply With Quote
Old Jul 02, 2012, 01:42 AM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
746 Posts
Keep backing off on the elevator throw. You probably will not need hardly any movement- 1/4" up and down may be too much even.

What do the instructions give for throw?

Brian
EscapeFlyer is offline Find More Posts by EscapeFlyer
Reply With Quote
Old Jul 02, 2012, 11:42 AM
Registered User
flybybob's Avatar
United States, IL, Woodstock
Joined Jun 2012
31 Posts
I had a similar issue with an avistar. Flew great but full back on the elevator... SNAP.. it would "tip stall".... Violently. I added a few ounces to the tail and I had no problem with tight loops. Could this be the issue? Or is my inexperience adding it up incorrectly?

My thought is that with weight in the tail and enough power it might "mush" but pull through.
flybybob is offline Find More Posts by flybybob
Reply With Quote
Old Jul 02, 2012, 12:07 PM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
746 Posts
It is surprising how little elevator throw some aircraft need.

In the 2, very crude, pictures I drew; I demonstrate the difference between laminar flow and a stalled wing while flying at flying speeds.

Every wing, regardless of symmetry, will do this at some point.

When you have a powerful enough elevator to force the angle of attack of the wing (as it penetrates the air) to a point it disturbs the air flow on the top of the wing, you destroy the pressure difference and you destroy lift.

Not all wings are laminar flow wings, but the principal here should explain the problem in general.

To maintain lift, you need enough laminar flow to create a pressure difference and create lift.

At what point the wing stalls depends on the airfoil chosen for the aircraft.

When you push the angle of attack past the point of effective airflow over the wing,the wing stops flying. At this point you have 3 forces working on the airplane: Inertia (an object in motion tends to stay in motion unless acted on by an outside force), Gravity, and Engine Torque. The torque of the engine will spin the aircraft since the stabilizing wing has lost its resistance being stalled.

The answer is to reduce elevator throw and you will not push the wing past this critical incidence.

In WW2, more fighter pilots died from this phenomenon in training exercises than died in actual. combat.

Brian
EscapeFlyer is offline Find More Posts by EscapeFlyer
Reply With Quote
Old Jul 02, 2012, 12:23 PM
team sleprock
whiskykid's Avatar
United States, WA, Port Angeles
Joined Dec 2009
3,486 Posts
Snap Roll; Flick roll; Flick



Snap Roll; Flick roll; Flick

A family of rapid autorotational or "horizontal spins," not unlike spins. Rotation is induced by a rapid pitch input followed by rapid yaw input, thus stalling one wing further than the other. This imbalance in lift causes the high speed roll.

if your plane starts ta turn when you "slam" the elevator in one direction, the I would start by making shure you don't have a warped wing!

if all is strait and true, then you should put some expo on the ailerons, as you might be putting in a little aileron without knowing it! thus inducing a slow snap!
whiskykid is online now Find More Posts by whiskykid
RCG Plus Member
Latest blog entry: great day!
Reply With Quote
Old Jul 02, 2012, 09:57 PM
Registered User
desolas's Avatar
Joined Nov 2010
9 Posts
Quote:
Originally Posted by Ilikebipes View Post
In the 2, very crude, pictures I drew; I demonstrate the difference between laminar flow and a stalled wing while flying at flying speeds.

Every wing, regardless of symmetry, will do this at some point.

When you have a powerful enough elevator to force the angle of attack of the wing (as it penetrates the air) to a point it disturbs the air flow on the top of the wing, you destroy the pressure difference and you destroy lift.

Not all wings are laminar flow wings, but the principal here should explain the problem in general.

To maintain lift, you need enough laminar flow to create a pressure difference and create lift.

At what point the wing stalls depends on the airfoil chosen for the aircraft.

When you push the angle of attack past the point of effective airflow over the wing,the wing stops flying. At this point you have 3 forces working on the airplane: Inertia (an object in motion tends to stay in motion unless acted on by an outside force), Gravity, and Engine Torque. The torque of the engine will spin the aircraft since the stabilizing wing has lost its resistance being stalled.

The answer is to reduce elevator throw and you will not push the wing past this critical incidence.

In WW2, more fighter pilots died from this phenomenon in training exercises than died in actual. combat.

Brian
Good post and explanation. I think I was looking passed the simplest answer and assuming something was wrong with the plane when really there wasn't ... I think I am just stalling the tail.

It's been an excellent plane otherwise.

Name: ImageUploadedByTapatalk1341280615.812396.jpg
Views: 84
Size: 47.5 KB
Description:
desolas is offline Find More Posts by desolas
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question .46 Seagull Edge 540 - what prop? Abrams 3D / Fun Fly Fuel Planes 9 Jul 01, 2012 12:14 PM
Discussion Seagul YAK 54 or Edge 540 as third plane thaman 3D / Fun Fly Fuel Planes 3 Jul 01, 2012 06:48 AM
For Sale Seagull Edge 540 .60 LPU alexkmmll Aircraft - Fuel - Airplanes (FS/W) 0 Jun 15, 2012 12:04 AM
Sold Seagull Edge 540 60 size ANIB $125.00 LPU bdboy007 Aircraft - Fuel - Airplanes (FS/W) 0 Jun 12, 2012 01:03 PM
Discussion EDGE 540 180 Seagull canister tunel Stefansuba Fuel Plane Talk 0 Mar 05, 2012 08:53 PM