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Rank: Newbie
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Joined: 5/15/2011
Posts: 3
Points: 9
Location: Illinois
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finishing my Primo 40 and it is tail heavy. Put a Saito 72 on the front and put tail servos in the front slot position and it is still tail heavy. anybody else have this problem and is there a fix?
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Rank: Administration
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Joined: 4/9/2008
Posts: 178
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Location: Bartlett
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The Primo has a pretty wide rage of acceptable CG.. Where does yours balance currently?
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Rank: Newbie
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Joined: 1/27/2012
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Location: malta
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my friend has an irvine 53 and cg is on the last mark with sone 3 oz lead in front he complains about an un stable prop hang can it be?
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Rank: Administration
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Joined: 4/9/2008
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Location: Bartlett
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That's crazy Idalmas.... I have a Webra .50 on mine (much lighter engine) and no lead anywhere. It balances perfect at a little further back than 6". Your friend must like his planes nose heavy.
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Rank: Newbie
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Joined: 5/15/2011
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Location: Illinois
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I was trying to balance at 5 inches, I will check and see where it actually does balance.
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Rank: Newbie
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Joined: 2/6/2012
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Location: Downers Grove, IL, USA
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My Primo with Hitec 475 HB's in the forward servo position and an OS 55AX is also tail-heavy. Moved rx battery forward in the wing but had the engine at the rear part of the cut-out. Model was trimmed and rolled inverted at mid throttle on first flight yesterday. It climbed inverted like crazy. Today I moved the engine forward as far as possible, also moved the tank. Cg is now at about 5 1/4 to 51/2". I'll see how it flies but my preference for the cg is neutral flight upright and inverted without trimming.
Did not have any of these problems with my MOJO which had the exact same hardware.
Herb
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Rank: Administration
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Location: Bartlett
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I think you'll like the Primo better with the 5 1/4" CG. This is exactly why I stress to check your CG after building but before covering. It's easy to move components and make changes then. When folks use heavier servo's and batteries, it pays to mock up the plane and make sure you're gonna hit your mark.
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Rank: Newbie
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Joined: 2/6/2012
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Location: Downers Grove, IL, USA
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Thanks Paul! Made another change to get the cg closer to the 5" mark (it flies fine at 5 1/4" but still climbs inverted). I installed the rx battery below the tank and things look good now. So far I'm impressed with the way it handles, especially slow flight. Not enough flight time to know what the differences are vs. the Mojo. Looking forward to warmer weather here in the Chicago area. Herb File Attachment(s):
 IMG_3659.JPG (581kb) downloaded 17 time(s).
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Rank: Newbie
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Joined: 5/14/2012
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Location: Stella, Ontario, Canada
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I am about to order a Primo 40. I have assumed that I would buy an OS 55AX (I have one on my Aeroworks ProX260 and it is a terrific engine, right from first flip onward). However, I also have a Saito 72 available. Noticing the note in here, and it now being several months later on in the game, I am curious as to how that worked out, and if Paul (or others) would have any advice.
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Rank: Administration
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Joined: 4/9/2008
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Location: Bartlett
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Both the OS 55AX and the Saito 72 are great choices for the Primo 40. Personally, I like 2 strokes on my 40 size birds. My all time favorite is the Webra .50, but they are out of business.
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