Warbird Electrics Discuss e-powered warbirds in here!

GWS Zero CoG?

Old 10-26-2008, 03:11 AM
  #1  
Twmaster
Registered User
Thread Starter
 
Twmaster's Avatar
 
Join Date: Aug 2005
Location: Dallas, TX, USA
Posts: 6,632
Default GWS Zero CoG?

I've got this beat to hell and back GWS Zero sitting here. Looks like maybe 30 minutes worth of work to put motor/radio in place.

I remember there being some controversy regarding the stock CG being totally wrong. So, if you've flown one and remember where your CG position worked out to be please reply.
Twmaster is offline  
Old 10-26-2008, 04:43 AM
  #2  
Bill G
Super Contrubutor
 
Bill G's Avatar
 
Join Date: Oct 2005
Location: West Central PA
Posts: 4,422
Default

Originally Posted by Twmaster View Post
I've got this beat to hell and back GWS Zero sitting here. Looks like maybe 30 minutes worth of work to put motor/radio in place.

I remember there being some controversy regarding the stock CG being totally wrong. So, if you've flown one and remember where your CG position worked out to be please reply.
Being that the Zero wing is virtually symmetrical about the center chord line, I'd just start at around 22-24% of the center chord to be safe.

My LHS built one before the ARFs caught on, to try to sell as an ARF package. Never sold, so they stripped the gear out of it and it's still hanging there. I figure if I can get them down low enough I'll take it for something to play around with.
Bill G is offline  
Old 10-26-2008, 05:08 AM
  #3  
Twmaster
Registered User
Thread Starter
 
Twmaster's Avatar
 
Join Date: Aug 2005
Location: Dallas, TX, USA
Posts: 6,632
Default

Thanks for the input Bill. The problem is that the Zero was the first GWS warbird (or I should say 'scale') plane they made. Somehow they really screwed up the wing incidence. The plane in stock form has a habit of zooming up sharply with application of motor power.

So many fixes were tried. Most just adjusted the CG. This issue is pretty much specific to this model.
Twmaster is offline  
Old 10-26-2008, 07:48 PM
  #4  
Bill G
Super Contrubutor
 
Bill G's Avatar
 
Join Date: Oct 2005
Location: West Central PA
Posts: 4,422
Default

Originally Posted by Twmaster View Post
Thanks for the input Bill. The problem is that the Zero was the first GWS warbird (or I should say 'scale') plane they made. Somehow they really screwed up the wing incidence. The plane in stock form has a habit of zooming up sharply with application of motor power.

So many fixes were tried. Most just adjusted the CG. This issue is pretty much specific to this model.
That's what I've heard too. I wonder why folks didn't change elevator incidence instead of wing incidence? Certainly seems more appealing than reshaping the fuse bottom. Can't say I've heard about downthrust being added either, which is a common "fix" we all know of.

I have a Guillow's Zero which flys well, but really banks into the turns with little input. Not a sleeping flyer. I think the Zero really does whip around.
Bill G is offline  
Old 10-26-2008, 11:20 PM
  #5  
Twmaster
Registered User
Thread Starter
 
Twmaster's Avatar
 
Join Date: Aug 2005
Location: Dallas, TX, USA
Posts: 6,632
Default

Flew the Zeke today. It seems the previous owner shaved the wing saddle down and removed the positive incidence. Set her with the CG spot on 50MM and she flew like on rails. Nice fast axial rolls, good easy to control inverted flight....

Until doom decended. While prepping her to fly I discovered I had forgotten to install a screw in the alieron servo horn. Put screw in, put wing on, set trims, flew. Went no control and crashed.

Post mortem revealed we somehow pulled the signal lead from the ESC out of the RX.

One nasty side discovery was made. The cheapo first gen TowerPro 15A ESCs do not have a shut off if signal is lost.

Thankfully the damage was minimal. Just need to replace the cowl and glue some foam back into place. install new prop. Maybe 20 minutes of work and I have a new cowl sitting here.
Twmaster is offline  
Old 10-27-2008, 02:23 PM
  #6  
cyclops2
Super Contributor
 
Join Date: Dec 2005
Location: New Jersey
Posts: 1,957
Default How I make sure the plane will fly correctly with power.

As part of a new plane final assembly I ALWAYS do the following.

Glue NO wings, horizontal or vertical surfaces in place!!!
Assemble those parts with just enough rubber bands & tape to give the plane a eyeball check from different angles. Make sure ALL surfaces look well aligned. Then measure from the same spot on the tip of the body end to the widest point of each wingtip. Adjust the angle if needed. Now measure wingtip to each tail tip. Adjust the tail if necessary.

At this time I remove ANY incidences that are NOT parrallel to the prop shaft.
The center line of the wing & tail airfoils ARE parallel to the engine shaft.I find that this ensures excellent low speed control.

I am now ready to glue everything into place with VERY THIN layer of RTV Silicone Rubber. It does absorb noise & vibration beautifully. This is a final glue up. Plenty of time to reset everything again if needed.

Now I do COG weight shifting from a COG chart on the websites. Close enough for now. Off to a DEEP grassed field. ALL surfaces... transmitter moved to a neutral setting. Turn OFF THE RECEIVER first, then the transmitter. You do NOT & are not to change ANY settings for the final adjustments.

Important. NO....NO wind at all for the next step & no prop on it.


TALL, NONE damaging grass or weed area. KNEEL DOWN. toss the plane fast enough to have gliding speed. 1 st tosses are ONLY 1 foot above the grass tops. straight glide ??

No ?? Move battery & or add weights till a flat glide appears.

NOTE...A turn left or right repeatedly means raising the wing on 1 side and putting in shims to eliminate the turning.

If you do the above steps. It is amazing how good a NORMAL amount of engine power will not cause a need for engine shims.

Last edited by cyclops2; 10-29-2008 at 07:54 PM.
cyclops2 is offline  
Old 02-07-2009, 11:43 PM
  #7  
Larry G
E-Pilot
 
Join Date: Jul 2007
Location: Peoria, Arizona
Posts: 444
Default

Nobody really answered the question - where do you set your COG on the Zero?

I just built one and it balances pretty close to the aft limit given in the GWS manual (48 to 55mm). It seems to fly, but I thought I read somewhere where the manual spec is wrong.

Does anyone have a number?
Larry G is offline  
Old 02-08-2009, 12:50 PM
  #8  
madpatter
New Member
 
Join Date: Dec 2007
Posts: 11
Default CG on Zero

Mine is at about 50mm. Lipo is crammed all the way into the nose to get her balanced. She flies GREAT. Really fun plane. Unfortunately my stick mount broke recently when I took the gear off for some hand launching. I am trying to decide if I am going to try and make a firewall mount or shell out $40 for a new Slope Glider kit.

My setup for the Zero:
Rear wing saddle shaved down about an 1/8th of an inch. (I hear the elevator thing works too)

Grayson Hobbies (welgard) 2212-13 otrunner.
Castle Tbird 18
TP 1320 3s
8 x 6 or 9 x 6 apc E prop.

1 bottle of 5min epoxy from BEFORE I learned about the incidence problem.

Really fast, really fun.
madpatter is offline  
Old 02-08-2009, 01:42 PM
  #9  
electrodude71
Member
 
Join Date: Jul 2006
Location: Deridder, Louisiana
Posts: 546
Thumbs up

I to did the 1/8 of an inch wing incidence fix and am flying about 50mm. but had to add a couple of small lead weights in the cowl to ballance.
good luck.
electrodude71 is offline  
Old 02-08-2009, 01:57 PM
  #10  
Sky Sharkster
Super Contributor
 
Sky Sharkster's Avatar
 
Join Date: Aug 2005
Location: Denver, Colorado
Posts: 5,455
Default GWS Zero C.G., Wing Incidence?

Hi Mike, I did the wing-saddle shaping, 1/8" at the rear to lower the incidence. A Himax 4200Kv inrunner, 5.6:1 gearing with 3s 2100 LiPos.
Had to move the battery nearly to the firewall to get 52mm C.G. but it flew fine there, sort of a mini-pattern model. Don't launch at full power, it'll roll left faster than you can blink!
A fun model when set up right, looks great chasing a Corsair! (or, the other way around!)
Ron
Attached Thumbnails Click image for larger version

Name:	IM000242MA11869700-0031.jpg
Views:	163
Size:	217.8 KB
ID:	92943  
Sky Sharkster is offline  
Old 02-08-2009, 02:00 PM
  #11  
gfdengine204
Super Contributor
 
gfdengine204's Avatar
 
Join Date: May 2007
Location: Sandwich, IL
Posts: 9,565
Default

I thought I've read that GWS fixed this problem? I just got a new slope kit Zero and this makes me wonder if I need to fix it?

Larry, I've also read 50mm is a common starting place for the CoG.
gfdengine204 is offline  
Old 02-08-2009, 02:21 PM
  #12  
Sky Sharkster
Super Contributor
 
Sky Sharkster's Avatar
 
Join Date: Aug 2005
Location: Denver, Colorado
Posts: 5,455
Default New/Old Zero?

Hi Kev, I've heard that also, but I don't believe GWS has any notification (with the kit) of which version it is.
Mine was an old version, I checked the wing setting with an incidence meter and it was + 4.5 degrees to the stabilizer incidence, way too much.
The 1/8" reduction still left the total decalage at + 1.5 degrees, enough to cause a slight "Zoom" at full power but not the full-looping tendency that resulted in the original horror stories and quite a few crashed airplanes.
Ron
Sky Sharkster is offline  
Old 02-08-2009, 02:30 PM
  #13  
gfdengine204
Super Contributor
 
gfdengine204's Avatar
 
Join Date: May 2007
Location: Sandwich, IL
Posts: 9,565
Default

Originally Posted by Sky Sharkster View Post
Hi Kev, I've heard that also, but I don't believe GWS has any notification (with the kit) of which version it is.
Mine was an old version, I checked the wing setting with an incidence meter and it was + 4.5 degrees to the stabilizer incidence, way too much.
The 1/8" reduction still left the total decalage at + 1.5 degrees, enough to cause a slight "Zoom" at full power but not the full-looping tendency that resulted in the original horror stories and quite a few crashed airplanes.
Ron
Ron,

Decalage still confuses me. Does this mean the Zero's leading edge was "higher" than the trailing edge (when the plane is upright), and the shim "pushes" the leading edge down, leveling the wing some?

Should the main wing and the horiz. stab be parallel to each other? And how can you measure to determine the angles? (Sorry for the off topic, fellas)
gfdengine204 is offline  
Old 02-08-2009, 03:08 PM
  #14  
Sky Sharkster
Super Contributor
 
Sky Sharkster's Avatar
 
Join Date: Aug 2005
Location: Denver, Colorado
Posts: 5,455
Default Decalage, Incidence, AOA and C.G.

Hi Kev,
These terms are tossed around like they're interchangeable, but they're not.
Incidence; Angle (in degrees) of a flying surface (typically a wing) to the zero datum line of the aircraft. A fixed or permanent angle. The datum is a (mostly imaginary) line that usually goes from front -to-rear along the fuselage side view. Generally speaking, the stabilizer is the only surface that's parallel to the datum or reference line. Typically the wing L.E. will be slightly "Up" or leading edge higher than the trailing edge. "Lifting", so to speak.
This reference line is usually drawn through the fuselage side view and top view. Also called "Centerline", normally when thrust offsets are used.
Decalage; The difference of angles between the horizontal lifting surfaces, most commonly, the wing and stabilizer. Since the stab is (again, usually) parallel to the datum, the wing incidence in this case is the same as the decalage.
If the stab also has incidence, the decalage will always be the sum fixed difference between the wing and stab.
AOA, Angle of Attack; The angle in degrees at which the wing faces the airflow in normal flight. If we have 3 degrees of incidence in the wing, none in the stab and the aircraft is flying in a level attitude (datum or fuselage level to the ground) the wing is flying at 3 degrees angle of attack.
A "Zero-Zero" setup is no incidence in the wing, no incidence in the stab and (usually) no thrust offset. Which results in no decalage, right?
Typically used in pattern or fully aerobatic models having a fully symmetrical airfoil and non-lifting stab. It will "Go where you point it" with no tendency to return to upright, straight or level flight.
Airfoils always have a centerline, called the Mean Camber Line. This is a point exactly halfway between the Upper Camber Line + Lower Camber Line at every point of the airfoil.
The Chord Line is a reference that splits the airfoil with a line from the point of the leading edge to the point of the trailing edge. This is usually used to measure incidence and AOA.
Here's a link to some of the terms and usage;
http://en.wikipedia.org/wiki/Airfoil
Hope this helps!
Ron
Sky Sharkster is offline  
Old 02-08-2009, 04:45 PM
  #15  
Larry G
E-Pilot
 
Join Date: Jul 2007
Location: Peoria, Arizona
Posts: 444
Default

Originally Posted by gfdengine204 View Post
I thought I've read that GWS fixed this problem? I just got a new slope kit Zero and this makes me wonder if I need to fix it?

Larry, I've also read 50mm is a common starting place for the CoG.
I bought this kit in 2008, unpainted, no power system. came out AUW at 18.5oz with a Rhino 1250 3 cell. The motor is about equal to a Park 400 I'm told. Wattmeter says around 200 watts with a APC 8x6 prop.
I did put a little down/right angle on the motor.

The build was pretty much stock except for CF wing spar, plywood firewall instead of the stick mount, and canopy attachment.

I can fly the Zero ok, it does want to zoom climb under high throttle, but not like it loops. I do need to put in a little down stick when accelerating, and need to be careful as it gets up high fast.

I'm not sure how to evaluate the flight performance as it is only my 4th plane. I've got a Super Cub, PZ Spitfire, Formosa I. The Formosa has the exact same power system and prop, but is 5 ounces heavier. The Formosa can be wacked wide open and will stay level. I only get about 7-8 minutes out of the Formosa on the 1250 Rhino and hit VC, The Zero needs such little throttle to stay at a level cruise I've put in 15 minute flights with battery to spare. When I was dogfighting some PZ Corsairs, the Zero could pull away, especially in a climb.

I'd have to do some grinding on my firewall to get the battery further forward, but I might have to go ahead just to find out if it would fly better with the GG forward more. Or maybe the wing saddle mod. I don't think GWS would have changed the kit, it would be real expensive to replace or modify the molds. Looking at my Zero from the side with the tail plane level, the wing does seem to be angled up more than the Formosa.
Larry G is offline  
Old 02-08-2009, 09:16 PM
  #16  
Twmaster
Registered User
Thread Starter
 
Twmaster's Avatar
 
Join Date: Aug 2005
Location: Dallas, TX, USA
Posts: 6,632
Default

@ Ron: Excellent explanation of those terms I learned something today. Thank you.

@ Larry: You are correct. Nobody really answered my question. I did get lucky and notice marks on each wing. These were the CG point noted by the builder. 50MM as stated before.

@ Kev: No way to tell if you have a corrected kit or not just by looking at the box.

The reason the Zeke has these issues is that is was the first of the warbirds from GWS. They did not intend or expect people to hop them up with big power. So flying these with a heavy brushed power system making maybe 60W of power they needed the incidence to keep it flying. Of course the rapid advent of cheap brushless power changed all that. My brushless Zeke measures 82W static on a 400XT, 3S 1050 lipo and 8x6SF prop.
Twmaster is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
watt_the?!
Aerodynamics
18
08-19-2008 06:39 PM
Fishjunky
Beginners
6
02-28-2008 04:09 PM
scottcr
Foamies
13
10-18-2007 05:01 PM
gfdengine204
General Electric Discussions
5
09-21-2007 02:38 AM
RandolphNav
Warbird Electrics
2
07-09-2007 01:32 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Quick Reply: GWS Zero CoG?


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.09673 seconds with 14 queries