saini flyer
Well-Known Member
I am fascinated by the small wings of F-104's and understand that a blown wing/flap brings much complexity/maintenance and issues that most have abandoned the concept but then I also look at DO-29 here and see that even a prop can be used to achieve the same but it too has a lot of complexity with slotted fowler flaps and what not and is not ideal for a homebuild with an ICE.
The discussion on Clmax on another thread here: made me look for the Cl added by blown flaps and according to wikipedia, "In general, blown flaps can improve the lift of a wing by two to three times. Whereas a complex triple-slotted flap system on a Boeing 747 delivers a coefficient of lift of about 2.8, external blowing improves this to about 7, and internal blowing to 9."
What happens if you use an electric motor mounted on the rear spar of each of the wings and use a CV joint mounted propeller shaft that moves along with the flap and has a propeller at the end like the DO-29 but avoiding all the complexity as in the sketch below.
Also any clue as to how much of lift can be achieved using the prop blowing the flap/wing Vs the Boeing example?
Any help with the details is appreciated.
The discussion on Clmax on another thread here: made me look for the Cl added by blown flaps and according to wikipedia, "In general, blown flaps can improve the lift of a wing by two to three times. Whereas a complex triple-slotted flap system on a Boeing 747 delivers a coefficient of lift of about 2.8, external blowing improves this to about 7, and internal blowing to 9."
What happens if you use an electric motor mounted on the rear spar of each of the wings and use a CV joint mounted propeller shaft that moves along with the flap and has a propeller at the end like the DO-29 but avoiding all the complexity as in the sketch below.
- The biggest issue with the blown flap is it's need when engine quits but using a brushless motor like Emrax should ease that.
- The electric propulsion can be used only for TO&L and then the prop can fold.
- If the lift increase is indeed 2-3 times the wing span will go down tremendously
- The tractor ICE can be substituted with a continuous HP industrial motor= inexpensive
- Redundancy in case of engine out
- Minimal complexity added
- Less effect of turbulence
- Almost avoids the TO&L engine out/density altitude accident!
- Quite electric propulsion for low noise during TO&L
- Uses well developed proven off the shelf existing technology
- No complicated load path, specially on the flaps and flap mechanism. A simple A arm hidden inside the flap can help secure the prop shaft
Also any clue as to how much of lift can be achieved using the prop blowing the flap/wing Vs the Boeing example?
Any help with the details is appreciated.
