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Funtana 125 pull pull set up

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Old 05-04-2010, 02:54 AM
  #1
tich
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Default Funtana 125 pull pull set up

Mike
I am building a Funtana 125 with a Saito 125 glow engine and am struggling to balance the model without adding a lot of weight weight to the nose. i have already relocated the rudder servo to the cockpit area but ideally I need to move the elevators to the same area and adopt a second pull pull pull set up. The alternative is to add a lot of weight to the nose and hence blunt the performance of the model. Obviously the Saito FG with metal mount is about 10ounces heavier than the glow 125 and that's the amount of weight I am playing with. I could stick a five cell sub C pack in the nose but I want to keep the model light so that goes against the grain especially as I wanted to use a 2 cell A123 pack. I was wondering what your opinion is- add weight or move the servos?
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Old 05-18-2010, 09:28 PM
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Default RE: Funtana 125 pull pull set up

I built the Funtana 125 with a Saito 125 and faced the same tail heavy issues you have. In fact I too had to add an extra 9 or 10 oz to the nose in the form of a secondary rec. pack and lead. I used two 5 cell 2700mAh NiMH receiver battery packs (7oz each with seperate switches) mounted to opposite sides of the firewall box and still needed 2 oz of lead mounted on the motor mount to balance at the VERY back of the CG range. The UAW was 9lb 13oz. Not so good. I flew it for the first time with this config just this past weekend. It flew as I expected, a little tail heavy for me and heavy overall. Im in the process of going to a pull - pull rudder and going with one 3200mAh LiFe rec. pack (7.4 oz) and NO lead. This mod. moves the CG just a little forward of where it was and takes off about 10 oz. IMO one important variable here is servo selection. The factory tested setup is just as you stated, with a saito FG and metal mount but whats more is that they used DS9411 servo's on the flight surfaces. 9411's weigh only 1.36 oz. Im not sure what your using but I used hitec 7985mg's. These are 2.2 oz each. That makes a diff of 2.4oz in servo (3) weight alone on the tail. I didnt want to spend 110 bucks on a servo that made only 95 oz-in of tq. so i went with the 7985. If its still tail heavy I will bite the bullit and buy a couple 9411's for the elevators. I hate adding weight as well, so in your case moving those elev servo's may be the answer. BTW, weight issues aside the plane flies great, it has a lot of potential.
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Old 05-19-2010, 02:42 AM
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Default RE: Funtana 125 pull pull set up

I used a single servo for the elevator and with both the rudder and elevator mounted in the cockpit area I can balance the model with a Life battery in the compartment. My model comes in at 8lbs 12 oz. Given that I used a light engine, removed one servo I am surprised it has ended up this heavy
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Old 05-19-2010, 02:45 AM
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Default RE: Funtana 125 pull pull set up

Here is a picture of my set up. If I did it again I would move both servos even further forward
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Old 05-19-2010, 02:51 AM
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Default RE: Funtana 125 pull pull set up

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Old 05-19-2010, 02:56 AM
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Default RE: Funtana 125 pull pull set up

I used the supplied battery tray for the wood and i guess I could have drilled a few lightening holes to shave a few grams but by this stage I was running out of time and patience!
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