SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 15, 2013, 12:11 AM
Plays with Toys
tim_mellor's Avatar
Port Fairy, Australia
Joined Jun 2005
1,972 Posts
Quote:
Originally Posted by mopetista View Post
sounds like the Spit you flew is nose heavy (not agile, and barrel rolls) - a Spit set up right will fly great even on 3s, if proof is needed youtube.com/watch?v=pYwGCFa0kjg
not easy to get the weight distributed correctly in the Spit though...
Maidened Spitty this morning 4S 850 Nanotechs fit the front bay perfectly, speedy in the second and Rx in front of the Elevator servo. CG is within a couple of mm even at this stage in power off and power on tests.

Added a 2.5mm solid Carbon rod cut in under the wing from Roundel to Roundel center. Also some glued vertical pins through the rudder and elevator so they stay put Flying wt 340g

Cool Toy. Bunch of non standard props to play with next.
tim_mellor is offline Find More Posts by tim_mellor
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 15, 2013, 02:57 AM
Plays with Toys
tim_mellor's Avatar
Port Fairy, Australia
Joined Jun 2005
1,972 Posts
Shuld also mention having a play with reverse differential to correct the barrel roll thing.
tim_mellor is offline Find More Posts by tim_mellor
Reply With Quote
Old Feb 15, 2013, 05:38 AM
Mike
miketre's Avatar
Joined Dec 2010
749 Posts
Does it mean that you set the aileron for less upward deflection and more downward deflection?
Or is it the other way around?
miketre is offline Find More Posts by miketre
Reply With Quote
Old Feb 15, 2013, 05:51 AM
Plays with Toys
tim_mellor's Avatar
Port Fairy, Australia
Joined Jun 2005
1,972 Posts
Correct. Example my old faithful Stryker runs about 4mm more down Elevon than up to stop the Barrel being as bad on it. One of my F3B gliders used to roll better with a mm more down than up deflection too.

Also going to reset all the servo arms to 90 degrees (close to) as I am running a fair bit of sub trim currently on the 3 servos which I don't like.

I will have a play then drop some settings back in the thread over the next few days.
tim_mellor is offline Find More Posts by tim_mellor
Reply With Quote
Old Feb 15, 2013, 09:23 AM
Registered User
gooniac33's Avatar
Sunnyvale
Joined Feb 2009
5,058 Posts
Quote:
Originally Posted by tim_mellor View Post
Shuld also mention having a play with reverse differential to correct the barrel roll thing.
I had no issue with mine doing this. It's really axial as it is! But I always set up my ailerons to be used as flaperons. That does help a little to start...
gooniac33 is offline Find More Posts by gooniac33
Reply With Quote
Old Feb 15, 2013, 09:38 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,031 Posts
barrel rolls - CG too far in front

If you set up differential (in a "normal" plane that means more up deflection than down on the ailerons) and the plane still does not want to do axial rolls, then your CG needs to be moved back (because you need a bit of uptrim to make up for the excess weight in front, and that ruins your rolls - and costs you some speed). Just try with doing a roll with slightly pulled elevator, and you see what happens.
On a delta things are different, then you might sometimes need a little negative differential for axial rolls, i.e., more down deflection of elevons than up (Multiplex recommended some negavive differential for the Funjet, e.g.) However, even the Funjet will roll nicely with symmetrical throws on the elevons. Usually no differential is needed when CG is correct.
The TX I know (Spektrum DX-7 and others) don't allow for negative differential, so you have to dial it in "mechanically", setting the servo horns not 90 degrees but suitably tilted at neutral so that you automatically get more travel in the desired direction).
The Funfighter Spitfire will be pretty noseheavy if you put a 4 cell lipo in the front compartment. I am having a light 3s 850 in the front and even used a different ESC (with different wire lenghts than the stock ESC) to get more weight in the rear. Now it is fine, doesn't climb at full throttle, rolls axially etc. I am slightly aft of recommended, don't remember exactly where. If you want best performance don't go furhter forward than the recommended CG. Of course it will be less twitchy and easier to fly (but faster in the landings) with a forward CG, but that costs you performance.
As Ray already wrote, you need pretty small throws on the Spitfire when setup correcly, and a fair amount of Expo. But then it is a treat...
mopetista is online now Find More Posts by mopetista
Reply With Quote
Old Feb 15, 2013, 12:29 PM
Registered User
gooniac33's Avatar
Sunnyvale
Joined Feb 2009
5,058 Posts
Quote:
Originally Posted by mopetista View Post
If you set up differential (in a "normal" plane that means more up deflection than down on the ailerons) and the plane still does not want to do axial rolls, then your CG needs to be moved back (because you need a bit of uptrim to make up for the excess weight in front, and that ruins your rolls - and costs you some speed). Just try with doing a roll with slightly pulled elevator, and you see what happens.
On a delta things are different, then you might sometimes need a little negative differential for axial rolls, i.e., more down deflection of elevons than up (Multiplex recommended some negavive differential for the Funjet, e.g.) However, even the Funjet will roll nicely with symmetrical throws on the elevons. Usually no differential is needed when CG is correct.
The TX I know (Spektrum DX-7 and others) don't allow for negative differential, so you have to dial it in "mechanically", setting the servo horns not 90 degrees but suitably tilted at neutral so that you automatically get more travel in the desired direction).
The Funfighter Spitfire will be pretty noseheavy if you put a 4 cell lipo in the front compartment. I am having a light 3s 850 in the front and even used a different ESC (with different wire lenghts than the stock ESC) to get more weight in the rear. Now it is fine, doesn't climb at full throttle, rolls axially etc. I am slightly aft of recommended, don't remember exactly where. If you want best performance don't go furhter forward than the recommended CG. Of course it will be less twitchy and easier to fly (but faster in the landings) with a forward CG, but that costs you performance.
As Ray already wrote, you need pretty small throws on the Spitfire when setup correcly, and a fair amount of Expo. But then it is a treat...
I will post my throws. They are really low and the CG is pretty rearward. But the plane flies wonderfully....will post later when I get home...
gooniac33 is offline Find More Posts by gooniac33
Reply With Quote
Old Feb 15, 2013, 05:17 PM
Plays with Toys
tim_mellor's Avatar
Port Fairy, Australia
Joined Jun 2005
1,972 Posts
Quote:
Originally Posted by mopetista View Post
If you set up differential (in a "normal" plane that means more up deflection than down on the ailerons) and the plane still does not want to do axial rolls, then your CG needs to be moved back (because you need a bit of uptrim to make up for the excess weight in front, and that ruins your rolls - and costs you some speed). Just try with doing a roll with slightly pulled elevator, and you see what happens.
On a delta things are different, then you might sometimes need a little negative differential for axial rolls, i.e., more down deflection of elevons than up (Multiplex recommended some negavive differential for the Funjet, e.g.) However, even the Funjet will roll nicely with symmetrical throws on the elevons. Usually no differential is needed when CG is correct.
The TX I know (Spektrum DX-7 and others) don't allow for negative differential, so you have to dial it in "mechanically", setting the servo horns not 90 degrees but suitably tilted at neutral so that you automatically get more travel in the desired direction).
The Funfighter Spitfire will be pretty noseheavy if you put a 4 cell lipo in the front compartment. I am having a light 3s 850 in the front and even used a different ESC (with different wire lenghts than the stock ESC) to get more weight in the rear. Now it is fine, doesn't climb at full throttle, rolls axially etc. I am slightly aft of recommended, don't remember exactly where. If you want best performance don't go furhter forward than the recommended CG. Of course it will be less twitchy and easier to fly (but faster in the landings) with a forward CG, but that costs you performance.
As Ray already wrote, you need pretty small throws on the Spitfire when setup correcly, and a fair amount of Expo. But then it is a treat...
In a power off dive test upright and inverted my plane stays in a downward direction and has minimal deviation from the set path so the CG is fairly correct for this plane as built I suspect.

It is 'wrong' to suggest that a forward CG is totally to blame for the plane climbing at full throttle for a start. It has far more to do with motor thrust lines and angle of attack and the resulting lift from the wing and other surfaces. If the CG is so far forward and you have to carry up elevator and it is this downward force from the tail (increases the effect as you go faster) that causes the climb in my case I have minimal to no trim up or down. So climb under power or not just about CG it is about resolution of forces be they lift or thrust angles.

Moving the CG more rearward which I plan to do a little yet is about getting the plane to turn hard with the same elevator throws to make it more bouncy . For others 1-2mm maximum at a time ONLY!.

Roll is also about resolution of forces. The reason the Rare Bear for example rolls cleaner is the mid mounted wing and having the center of mass more inline with both it and the motor thrust line so even up and down aileron for it will be correct. When you move to a low wing with the center of mass above it you need to overcome this slight coupling effect by changing the only thing available to us after the plane is built which is Ailerons.

Some of the Barrel Roll in my case I am blaming in part on the servo arms needing that sub trim to center them (often causes non even throws left/right) . First rule in R/C setup should always be no trim arms 90/0 then electronically tweak, this generally results in a better flying aerobatic toy. As I didn't want to dig into the wing to undo the screws on the preglued servos I thought I would see how it went.

Negative differential is easy to create BTW using one of two methods. Using the Travel adjust or limits or swapping left and right Ailerons over on the Rx.

Agreed a bucket of Expo is a good thing. Flying time 10am Saturday here
tim_mellor is offline Find More Posts by tim_mellor
Reply With Quote
Old Feb 15, 2013, 05:25 PM
Registered User
Joined Mar 2011
101 Posts
Were is this p-38
Duke58th is offline Find More Posts by Duke58th
Reply With Quote
Old Feb 15, 2013, 07:16 PM
Plays with Toys
tim_mellor's Avatar
Port Fairy, Australia
Joined Jun 2005
1,972 Posts
Tweaked and flown. Rolling much better at about 5.5mm down and 5mm up at the Fuselage end of the Aileron, I could cope with some more either way but this is cruisy and crisp . Did this by travel limit BTW 82% Down and 75% up on both servos so it is only a slight difference. Rechecked Elevator trim and no measurable trim off the centerline.

Brought the CG back a tiny touch and I am thinking it could do with a touch less downthrust than stock.

If it stays together it will likely become one of my favorite toys
tim_mellor is offline Find More Posts by tim_mellor
Reply With Quote
Old Feb 16, 2013, 02:50 PM
Registered User
mrgriz's Avatar
Joined Oct 2006
303 Posts
Quote:
Originally Posted by Duke58th View Post
Were is this p-38
I won't be getting one , they look too delicate , I wish they would make a twin mustang , no undercarriage just 2 of the current funfighter mustang fueslages, keep it simple and fun

something like this or a twin rare-bear , not a scale plane but who cares just throw it in the car and enjoy
mrgriz is offline Find More Posts by mrgriz
Reply With Quote
Old Feb 16, 2013, 03:59 PM
I'm overcoming gravity!
Murman's Avatar
USA, NC, Huntersville
Joined Jul 2008
4,018 Posts
Quote:
Originally Posted by mrgriz View Post
...I wish they would make a twin mustang , no undercarriage just 2 of the current funfighter mustang fueslages, keep it simple and fun
Why not just buy 2 Mustangs and make your own.
Murman is offline Find More Posts by Murman
RCG Plus Member
Old Feb 16, 2013, 05:47 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,807 Posts
Quote:
Originally Posted by Murman View Post
Why not just buy 2 Mustangs and make your own.
You need to make the fuselage longer too.
aeromaniac is online now Find More Posts by aeromaniac
Reply With Quote
Old Feb 16, 2013, 06:30 PM
I'm overcoming gravity!
Murman's Avatar
USA, NC, Huntersville
Joined Jul 2008
4,018 Posts
Quote:
Originally Posted by mrgriz View Post
...I wish they would make a twin mustang...just 2 of the current funfighter mustang fueslages, keep it simple and fun
Quote:
Originally Posted by aeromaniac View Post
You need to make the fuselage longer too.
Why? That's not what he was asking for.
Murman is offline Find More Posts by Murman
RCG Plus Member
Old Feb 16, 2013, 09:13 PM
Registered User
mrgriz's Avatar
Joined Oct 2006
303 Posts
Quote:
Originally Posted by Murman View Post
Why not just buy 2 Mustangs and make your own.
yes I have been tempted to do something along those lines with 2 rare-Bears
mrgriz is offline Find More Posts by mrgriz
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion .60 size war birds, wich flys the best? mikes68charger Fuel Warbirds 27 Mar 07, 2011 11:08 AM
Yippee! GWS War Birds 400 Series GWS4CEO GWS (Grand Wing Servo) 160 Feb 23, 2006 04:37 AM
Alert gws war birds vs alpha war birds? tweissen Parkflyers 18 Aug 07, 2004 10:49 PM