Originally posted by a088008
Looks like a good project. The CAD drawings are coming along very nicely. Keep it up!
A comment about wing area. Generally the smaller the model the more disproportionate (larger) it's wing area to achieve the same flight performance. Your 1/6 model will have 1/36 the wing area of the real thing. Now wing loading will comes into play. The real thing has a much higher wing loading than your model will have, so that's too your advantage. The larger the model the higher the wing loading it you get away with. So, you might want to consider taking these factor into account before leaving the wing dimensions at 1/6 scale. I would enlarge the cord and span slightly, but only as much as is needed to give an acceptable wing loading. But, if you build the model light you can get away with less enlargement.
The second comment is about airfoils. If the real thing uses a certain airfoil, you can bet that it is not going to give you the same flight characteristics when scaled down to 1/6. There are many reasons why, but to mention a few, the cord and cruise velocities are less and therefore decrease the Reynolds number of the airfoil. This is bad news for a full scale airfoil since it will be much less efficient at model scales. The air flowing over the airfoil will also be less turbulent and more laminar. This will lead to a greater chance of boundary layer separation and less chance of reattachment since turbulent flow reattaches easier than laminar flow. Use the X-Foil software if you want to see this. Compare it to the Eppler airfoil you wanted to use and you will see that the Eppler airfoil was designed to operate at low Reynolds numbers, and not the real thing. Now, the larger the model the less of an effect the Reynolds number has since it will approach the real Reynolds number, so this is to your advantage. But, if you want to use the real airfoil, remember than your drag will be increased and will therefore dictate a larger power plant. Again, building it light helps keep the induced drag (due to the airfoil trying to lift the plane) down to a minimum.
Whew! Good night.
-Q.
Thanks, there will no doubt be alot of parasite drag, because the camber is rahter large, some 2" in in places. Look at the graphic those little numbers along side the front view wing are in 16th. so 30/16 is how you would read that number. That just under 2".
I can see the power plant will have to grow bigger, but I can built it lite that is not a problem. I have some ideas on drilling holes and some other ways to make it liter.
Just wish I knew how to make composits or do molds. But that is another thread.