4* 40 CG and Battery Placement
05-28-2007, 10:35 PM
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4* 40 CG and Battery Placement
Hi,
I have a Four Star 40 ARF with a Saito .62 up front.
I currently have a 1700mAh NiCd (6oz) pushed as far back against the servos as possible which places it with a third of it's weight behind the CG point and i still needed 2oz of lead at the tail to balance the model on the spar as suggested in the manual.
When i maideded the model it wanted to nose dive an needed an awful lot of up trim to fly straight and level, so i'm of the opinion that it's still nose heavy.
I want to get the model better balanced and also be able to remove the lead from the tail, so i was looking at possible battery locations.
I have a few options.
It looks like i could squeeze a physically smaller 1400mAh Intellect NiMH pack (3.2oz) behind the servos between the servo tray and cockpit floor which would move the weight about 4" rearward. I'm not sure if the lighter pack further rearward would be enough to remove all of the lead.
If i need to go even further rearwards there is the base of the cockpit which extends another 6" past the radio tray, but being an ARF it's already covered and a PITA to get to and has no slots cutout for velcro battery straps.
The other option i thought of was to mount the battery inside the bubble canopy. I could spray it black from the inside with RC car paint to hide the pack. I'm just worried that moving the pack above the mid-line of the plane might effect it's flying quality in other ways.
Other ideas i have are to find a lighter muffler for the Saito and maybe some lighter landing gear to reduce some of the weight up front.
Option 5 is to put a lighter 2-stroke up front (like the 4* was originaly designed for) and buy a new home for the Saito .62, like a Somethin' Extra perhaps.
I have a Four Star 40 ARF with a Saito .62 up front.
I currently have a 1700mAh NiCd (6oz) pushed as far back against the servos as possible which places it with a third of it's weight behind the CG point and i still needed 2oz of lead at the tail to balance the model on the spar as suggested in the manual.
When i maideded the model it wanted to nose dive an needed an awful lot of up trim to fly straight and level, so i'm of the opinion that it's still nose heavy.
I want to get the model better balanced and also be able to remove the lead from the tail, so i was looking at possible battery locations.
I have a few options.
It looks like i could squeeze a physically smaller 1400mAh Intellect NiMH pack (3.2oz) behind the servos between the servo tray and cockpit floor which would move the weight about 4" rearward. I'm not sure if the lighter pack further rearward would be enough to remove all of the lead.
If i need to go even further rearwards there is the base of the cockpit which extends another 6" past the radio tray, but being an ARF it's already covered and a PITA to get to and has no slots cutout for velcro battery straps.
The other option i thought of was to mount the battery inside the bubble canopy. I could spray it black from the inside with RC car paint to hide the pack. I'm just worried that moving the pack above the mid-line of the plane might effect it's flying quality in other ways.
Other ideas i have are to find a lighter muffler for the Saito and maybe some lighter landing gear to reduce some of the weight up front.
Option 5 is to put a lighter 2-stroke up front (like the 4* was originaly designed for) and buy a new home for the Saito .62, like a Somethin' Extra perhaps.
05-29-2007, 12:26 PM
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RE: 4* 40 CG and Battery Placement
CustomPC. Keep me updated on your findings. As you know I have a 72 ready to go in mine. I cut the covering on the bottom punch out just behind the wing so I could add some bracing to the frame per some recommendations on this web site. I think Iām going to build a small compartment there so a battery pack and foam should be able to be inserted and removed without much problem.
05-29-2007, 03:01 PM
#3
RE: 4* 40 CG and Battery Placement
I had a Saito 56 in my 4*40 and had no CG problems. All the 4* planes have a wide CG range. Is your engine mounted as close to the fire wall as possible? If you are experiencing difficulty in trimning and landing due to not enouth elevator (ie nose heavy) check you engine thrust and wing incidence. Is yours an arf or the kit? I've had three four stars and never had a problem with CG. Trees and (attempted) knife edge snap rolls 20 feet off the ground are what have done mine in!
Good luck.
Good luck.
