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Building Tips and technical articles. => 1/2 A building. => Topic started by: Dennis Saydak on January 15, 2011, 06:13:07 PM
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I have a Brodak 1/2 Pathfinder almost ready to cover. I don't have a clue as to what it should weigh or what weight a Big Mig .061 can handle. So far the weights of all the components total 294g / 10.37 oz. Wheels, spinner, pushrod and finish aren't included but everything else is including the engine prop & tank. How's the weight so far? I still have the option of lightening up the structure by hogging out the fuselage & stab if necessary.
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The Big Mig should be good up to about 12 ounces, then you have to start going to shorter lines. At 12 oz. with a 5.5x2 APC prop or Cox 5x3, I would think you could fly 45 ft x .008 lines with ease.
If weight gets up to 14 -15 ounces, you are no longer going to be competitive, but will be safe and have fun on 40' lines.
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Thanks Larry. I'll make the lightening mods as shown on the plan as a matter of necessity. The wood in the kit was very decent quality and I normally build fairly light but a little extra effort will pay off in performance.
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The Big Mig should be good up to about 12 ounces, then you have to start going to shorter lines. At 12 oz. with a 5.5x2 APC prop or Cox 5x3, I would think you could fly 45 ft x .008 lines with ease.
If weight gets up to 14 -15 ounces, you are no longer going to be competitive, but will be safe and have fun on 40' lines.
That's just what I was gonna say, 12 oz. is about the limit for ideal performance. A .061 will fly more weight than that but will tend to be underpowered. I think my heaviest was an earlier LittleAxe at about 15 oz. it had a lot of wing, thick airfoil, flaps and flew pretty well but could have used more oomph for sure. Same plane at 12 oz. makes all the difference.
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I've lightened up the stab & fuselage but I have yet to do the same to the flaps. The weight saving so far is 6/10 oz ( 5% of the target weight). Perhaps that's not all that great but when you consider the target weight of 12 oz is it rather in?-significant? The saving may be potentially cancelled by added tail weight (if needed). I don't know if these build nose or tail heavy. I'll also do more sanding on the fuselage and I will also trim some material off the nylon hinges for additional weight saving.
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Sewn hinges (do a search, they are well documented) add approximatley NO weight. They also add NO friction! What's not to like? My controls will droop to full deflection when I turn my models over one way or the other (if I have done everything else right) This is crucial for small models. We don't need no stinkin' line tension (if the control system is perfect!!!) S?P VD~ CLP**