Monday, October 31, 2011
External link: Article about Flying wings
If you are into flying wings like me, this PowerPoint slideset might interest you. It compares the basics of conventional airliner and flying wing airliner.
Much bigger planes in other words, than my interest area. However, some of the pros and cons findings for each configuration also apply for the small version. Not all though as the starting point does not have engine nacelles and engines sticking out of the wing.
http://www.engbrasil.eng.br/index_arquivos/ap23.pdf
I haven't done yet comparison for the wetted area of a flying wing compared to a sailplane like structure.
Logic tells that the flying wing in this size category might have more wetted area. But I am not sure. I need to design both and then measure the wetted area of both and compare.
I am not a big fan of wing twist and the amount of wing twist on PUL-10 causes me shivers (wing tip twisted 10 degrees). That can't be good for cruise, simply can not. Ten degrees is insane amount of twist - on cruise the tips are on negative angle of attack and cause a lots of negative lift. The wing tips act as rather poor tails this way - it is very short coupled and if you have tail deflected that much on that close, the wing center section will need to lift also the negative lift of the tips which will make the plane to perform poorer. I am quite sure that a flying wing should be made stable without that much twist.
I have a related idea for a flying wing:
- one problem with flying wing is that flaps can not be used
- what if you had small trim tails that look like the ones in SpaceShipOne. When flaps would be down, the trim tail, would cause opposing pitching moment to negate the pitching moment of the flap
- The elevator control otherwise would be like on a flying wing, with elevons.
- I haven't tried this out yet but it can be tested with RC model.
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8 comments:
Regarding the ease of construction point. I have built R/C flying wings and a Low Aspect Ratio model. Construction was amazingly simple.
I wonder if the ease of construction angle would make the BWB a good option for home builders. If the design significantly reduce the time to build and skill required it would be nice to see homebuilt designs for the technology.
You may allready have this book, but if not,well worth reading. "Tailess aircraft in theory and practise" by Karl Nickel and Michael Wohlfahrt. Also amount of twist varies with chosen airfoil, sweep, aspect ratio and winglets. Correct use can reduce twist. Have an idea to build a full size flying wing, but about to build RC model first.
At $699 new and $350 used. Not likely to get it.
Hi Robb, here is a link to Amazon. These books from £35.00 from UK. Just make sure its in English. I paid £60.00 for mine and the book is worth every penny.
http://www.amazon.co.uk/gp/offer-listing/376432502X/ref=sr_1_1_olp?s=books&ie=UTF8&qid=1321006510&sr=1-1&condition=used
Hope this helps
Bruce
Regarding Karolina's original post about pitching due to flap defection, this would be true on a flying Plank, but with wing sweep, this all becomes possible. Depending on length of flap, sweep,and aspect ratio, you could have a moment neutral flap, in conjunction with elevons. If additional lift occurs in front of the centre of lift of wing, then wing will pitch up, if behind, then it will pitch down. This centre of lift position will change as flap is deflected. Obviously you would prefer a gentle pitch down so that elevons deflect upwards hence increasing wash out and avoiding tip stalling
Hi Karoliina and at all
My compliments for blog, it is very interesting in particular for the analyses about electrical power system and fly wing
But I have decided to write you to ask informations about the aricraft that is presented in the top of webpage, in the image that has a blue background and the line in white!!
Do you know the name of this model???
Can you indicate where I can find other informations??
or the company that design its?
kind regard
You can use flaps with flying wings. At least Horten IX (Ho 229) used flaps. During the test flights in 1945 they just used the outer flaps but never the inner flaps (you might check my blog for an article about the Horten IX). Here is a link:
http://1.bp.blogspot.com/-Dq3KtIiEB5E/Tq54WP8RpQI/AAAAAAAAAkw/bnCIQfwAVV4/s1600/Horten_IX.png
My opinion is that a flying wing is a bit dangerous and that a conventional design is much more forgiving to pilot errors and similar matters. If you have to use 10 degrees of twist to be comfortable with a flying wing then you should also add the tail (and fuselage) to it since those are the most effective naturally stabilizing factors in a flying device. And who needs so much wing? You need the full lift usually only during take off and landing and most of the time the large wing would only produce drag if that plane is to be used mostly for cruising. A fighter, bomber or high altitude aircraft might need such a large wing but also high lift devices are available.
One should do calculations to be sure what is actually most optimal for any given task.
Here is a link to a historic approach to a high altitude airplane by Wiley Post:
http://books.google.fi/books?id=xd8DAAAAMBAJ&lpg=PA492&dq=Popular%20Mechanics%20Wiley&hl=fi&pg=PA492#v=onepage&q&f=true
Best Regards
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