RC Slope Soaring in Hong Kong

Why do people do it? Some say on the top only and some say on both side, what are the difference? Many thanks!

你想問mixing原理定應用呀﹖

可能你真係問 waxing 打臘.

咁打完臘, 隻機咪靚仔 D 囉.

同埋, 可以令表面光滑 D, 減低風阻??

Thanks all,

I mean waxing, as someone told me before - waxing the wing bottom will decrease the lift of the plane, and waxing the top can increase the lift and speed. Don't know if that's true or not.

打蠟要分翼底翼面我真係第一次聽﹐更加無實際經驗。不過純講理論﹐打蠟會令翼面更光滑﹐不論翼面翼底﹐都可以降低空氣既摩擦阻力﹐提昇速度﹐間接增加升力。

但翼面變得更光滑會影響氣流黏附係機翼表面既能力﹐有可能令機翼提早失速。好多空氣動力學既書都有提到 邊緣層(boundary layer) 呢樣野﹐邊緣層係指貼實翼既表面個層氣流﹐一般都希望係做到呢層空氣係紊流( turbulent flow ) ﹐呢度唔係講失速個陣氣流完全脫離翼面個種大範圍紊流﹐而係好薄好薄既一層紊流﹐再打上就係層流 ( laminar flow ). 邊緣層係紊流既壞處就係增加阻力﹐但好處係令空氣更黐翼面﹐延遲失速﹐有D真飛機既翼前緣裝左一排好似牙既 vortex generators ( http://www.newenergy.org.cn/english/guide/index-9.htm) ﹐目的就係要製做一層翼面紊流﹐延遲失速。同樣既裝置都有用係模型上﹐譬如有D自由飛飛機既翼前緣做到起?#29399;牙?﹐又有D人貼條 zig-zag 形既厚膠紙係翼前緣既上面﹐都係咁既作用。所以如果打蠟真係要揀位﹐就應該唔好打翼面。

翼底唔會有氣流分離現像(反飛除外) ﹐所以係越滑越好﹐無也理由係度打蠟會降低升力。

其實飛機上面好多裝置都只係會對性能帶黎好小改善﹐對一程飛十幾個鐘既長途客機黎講﹐呢D小改善可以節省燃料﹐所以有用﹐但用係我地D模型上﹐作用係好難感覺到。所以我覺得未必需要睇到咁仔細。

Thank you Y C for the detailed explaination on aerodynamic.

唔 ~ 呢個可能係 Stanley 隻舊爛 Sting 飛到咁既快原因 . . .