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RE: Nitro Models Cessna 337 - Build Thread - 6/12/2012 6:35 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Always liked this aircraft.

Got two events coming up MARCEE ( www.marcee.org ) and WATTS (http://www.watts2012.net/Welcome.html ) – maybe?

Fortunately the decals aren’t on so I have a bit more liberty with the scheme @ not too much work.

Big but not too much room in the fuselage – like many new ARFs the construction laser cut light ply.

As implied above, this isn’t for the faint of heart 1st time for an ARF guy – not much detail in the manual at all!

Went with a package I never tried before for the power system; was easy to order from Hobby Partz:
Tacon Big Foot 60 Brushless Out Runner (400KV)
Dynam Detrum 60A ESC
20C Sky Lipo 5000mAh 18.5V 5S1P

Will likely go with 14x10 up front and 14x12 behind.


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       Post #: 176

RE: Nitro Models Cessna 337 - Build Thread - 6/13/2012 3:16 AM   
Sgt_Ric


 

Posts: 19
Score: 100
Joined: 11/10/2006
Last Login: 1/21/2013
From: High Prairie, AB, CANADA
Status: offline 		My single engine mod has an AeolianMotors C4260 KV500 pushing a 3 blade 16x8 pusher prop.
I had to change the the tires to much larger just to add clearance, and given the flex, I would like to replace the main gear completely with some carbon ones from a Sukoui model.

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       Post #: 177

RE: Nitro Models Cessna 337 - Build Thread - 6/15/2012 2:50 AM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Been doing a few things motors/ESCs/ batteries are to arrive tomorrow !

Nice guy posted some motor info for me; so. I'm putting a plan together.

Did the nose wheel servo in the nose; folks were saying it needs some weight up front:

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       Post #: 178

RE: Nitro Models Cessna 337 - Build Thread - 6/19/2012 5:42 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Got the motors, ESCs, and packs!

Motors seem very nice and run well – 2.2 & 2.5amps @ no load w/9.8V; loads tests tomorrow.

Packs seem well balanced; no charge rate info listed, i.e.: 2C or 3C just Ultimate Charge Series?

ESCs – didn’t check out correctly at 1st and there is no BEC data listed on their labels?
1st test w/ A123-3S, one worked w/CC BEC added.
2nd test w/Full LiPo-3S – one yes & one no.
3rd plugged into Turmigy Plush Programming Card and set parameters – now both worked!

Next will be mounting motors and getting ready for CG check.

Mass, Torque, & CG?

I always find the balance point of my wingless Fuselages before making a change in set-up/equipment.

Then set it back to that point after the upgrade (bigger battery, adding skis) – seems to work every time.

IIRC (more than 30years ago) from my Kinematics/Mechanic of Solids class a “force couple” (i.e. torque) can be move anywhere within its plane.

So, I’m wondering if I can use my technique Pre-Flight for positioning the equipment?

In this case I’ve added weight to my Skymaster to get the CG per plan; then found the balance point of the fuselage.

I’m hoping that I can put the equipment in (motors, batteries, cowls, etc.) and balance the fuselage at the point found above.

And, then be “Balanced” when fully assembled.

Comments!

TIA,

Jim

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       Post #: 179

RE: Nitro Models Cessna 337 - Build Thread - 6/19/2012 6:30 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Do know the Torques about the per plan CG needs to be of equal value and in the opposite direction.

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       Post #: 180

RE: Nitro Models Cessna 337 - Build Thread - 6/20/2012 12:53 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Weight of the wing/boom/tail groups is 3#-15oz; torque about the per plan balance point is 450 in-oz:

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       Post #: 181

RE: Nitro Models Cessna 337 - Build Thread - 6/20/2012 6:44 PM   
nioa



Posts: 24
Score: 100
Joined: 2/8/2008
Last Login: 3/19/2013
From: Phoenix, AZ, USA
Status: offline 		Keep up the good work Jim (jrb1),

I'm watching your build with interest. I have two of these planes sitting in the box. My plan is to install two .46 size motors, and to modify the way the wings attach, and battery compartment access. As soon as I finish my B-17, I will be on to building this bird.

Wanted to pass along some encouragement, and appreciation for your input,

Nick


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       Post #: 182

RE: Nitro Models Cessna 337 - Build Thread - 6/20/2012 7:19 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Guess I proved my 1st thought to be incorrect; but, it does works well enough when making smallish changes with a typical aircraft configuration.

Here’s my set-up to check the Fuselage: 21” >> 1# 5.5oz.

With no pack scale read 7.5oz packs need to be ahead of per plan balance point.

The found an alternative way to easily check things as I go along - - fuselage balance @ 3/8” behind the front wing former.

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< Message edited by jrb1 -- 6/21/2012 1:04 PM >

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RE: Nitro Models Cessna 337 - Build Thread - 6/21/2012 3:10 AM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Arming harnesses & ESCs installed – ran both motors too !

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RE: Nitro Models Cessna 337 - Build Thread - 6/22/2012 10:32 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		The method seemed to get me close – though I think she’s nose heavy:

Weighs in a portly 13#-3oz.


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RE: Nitro Models Cessna 337 - Build Thread - 6/26/2012 2:38 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Still working on the beast!

The way this thing goes together the packs are buried and can’t be move fore/aft when all buttoned up.

To complete the datum I plan to locate the CG of the wing/boom/tail/group.

Will also go back the moment fuselage set-up; and get its weight and CG.

The I should be able to adjust the RTF CG in an exercise similar to “weight & balance” check of a full scale.

Will likely use the back of the front spinner as the reference/datum.




quote:

ORIGINAL: steve1mac

With all the additions my plane weight is around 16 pounds!




My 13-3 doesn't seem so bad.


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RE: Nitro Models Cessna 337 - Build Thread - 6/26/2012 9:28 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Progress!

Got CG of wing/boom/group and set up fuselage again and got its weight & CG.

Using the Back of the spinner as the datum the CG calculates per plan!


Math shows that moving the fuselage CG back ½” changes RTF back about 0.7”


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RE: Nitro Models Cessna 337 - Build Thread - 6/27/2012 3:14 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Some prop tips here; bushing/spacer is needed to allow regular APC E to be used with rear spinner.

And, washers made from sanding screen are useful too!


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RE: Nitro Models Cessna 337 - Build Thread - 6/29/2012 12:33 AM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Nice day for a maiden!

Moved out too quick for photog on take off, nice landing though!

[youtube] http://youtu.be/IGxYaonPKos [/youtube]

[youtube] http://youtu.be/BSl8mNH8OSI [/youtube]

Gear is bowed a bit – ugh.

Ran out of both up elevator trim and left aileron (the wing’s not parallel) – very nose heavy!

Too light on the nose wheel; so, I flipped the mains.

Maiden CG calc'd to: 125mm.

w/batteries aft all the way calc's to: 142mm going with it.

Buttoned up and ready to go again

Will leave elevator as is likely to take out all of it's trim w/new CG.

Going to check lateral balance one again and change aileron trim.




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RE: Nitro Models Cessna 337 - Build Thread - 7/2/2012 12:37 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		2nd flight on Saturday; landing wasn't as smooth . Have beefed up the mains by pop riveting on some aluminum from an old set of mains.

Still needed more up trim; but no stick pressure when inverted.

Looks like I might be using a bit more MAH out of the rear pack maybe the 2" of additional pitch is a bit much?


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       Post #: 190

RE: Nitro Models Cessna 337 - Build Thread - 7/5/2012 4:06 PM   
jrb1


 

Posts: 75
Score: 100
Joined: 2/6/2004
Last Login: 2/13/2013
From: Edina, MN,
Status: offline 		Maybe I’m over powered?

Another flight Tuesday – I hate these one flight and need to make a change/repair back home outings.

The take-off was great and it finally seemed be in trim; made a nice pass – cool!

Next pass weird noise – ugh.

Gotta land – needed a go around too.

Upon landing notice the rear prop wasn’t right – its nut and washer were gone; lost sometime during the flight.

Definitely before the go around.


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RE: Nitro Models Cessna 337 - Build Thread - 10/12/2012 1:36 PM   
jaimefernando


 

Posts: 20
Score: 100
Joined: 5/9/2007
Last Login: 12/12/2012
From: Aberdeenshire, UNITED KINGDOM
Status: offline 		Thanks for your detailed post.

I maiden'ed my model last weekend and it didn't go well. As it is the first time I use ASP engines ( I am an OS Engines man...) they didn't run smoothly. The take off was fine but then the engines revs were up and down and after battling with model balance and trimming, one engine quit (the front one!!) so i had to land. I have to say that the model was still flyable with one engine, but I would have preferred that the working engine was the front one and not the one in the rear as it makes the model much more prone to unstable conditions. The landing wasn't that great and the front engine +firewall came apart. I have to say, I am amazed as to how strong the structure was!!. Nothing happened to the wings or fuselage and let me tell you that it was a VERY rough landing. Back in my workshop and my 337 should be ready in a couple of days for the second attempt, windy dependant.

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       Post #: 192

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