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Archive for June, 2017
Posted by eagle60 | Jun 12, 2017 @ 02:55 AM | 7,411 Views
I do not use more thickness than originals, as my goal is to acieve higher speed. Basically in the center I use a 17 cm (nearly 7") cord goe445 wich is simmetric and laminar with thickness increased to 7.4%, thus giving about 10 mm thick airfoil. On the tip I use a 11 cm (nearly 4 1/2") cord mh42 airfoil with thickness increased to 8.9 % to get an airfoil with the same thickness (in mm) as in the center with 1.7 negative incidence to get zero lift effect. In this way wings are neutral with constant thickness but absolutely no tip stall causing a sudden flip, if you slow the plane progressively increasing elevator up with no motor thrust it will start to sink flat.
All airfoils can be made with the program "profili" , which is free and can be downloaded here :

http://www.hoppenbrouwer-home.nl/ika...re/profi12.htm

The material used is not the normal polystirene (white) foam, but the more compressed one (see photos); you will barely notice the weight increase, but the strength will be much higher.
Now the strengthening tecknique depends on the weight of the model and the speed you want to achieve and if wings will be swept or not.
for speed up to 200 km/h (125 mph) and flying weight up to 600 gr (22 onces):
- On the swept wing I use a .8 mm piano wire rolled up the soldering iron (see photo) to cut a 3mm deep x 1mm wide slot top and bottom of the wings at the max thickness point for about the 2/3 or 3/4 of the wing span in which I glue with foam...Continue Reading