Willaroo

The photograph below shows the wing of a Euro Firebird turbine trainer jet which I am attempting to build. <o></o>

The instructions (which are quite vague) say the wing can be split I assume for part flap part aileron at the discretion of the builder. <o></o>

I have decided to take the opportunity to split the control surface to produce part flap and part aileron. I don’t know if this is the right decision or not but it seems from what I have read that flaps will creat more lift thus enable me to land at a slower speed. Also that the inboard portion of the aileron doesn’t really do a great deal so surely it would be better utilised as flap? Comments welcome….<o></o>

My question is, how do I determine where to split the control surface? What proportion should be flap and what should be aileron?<o></o>

I would happily supply further information, photographs if this is needed?

Please help.<o></o>

Lnewqban

Your logic is correct.

I recommend this excellent book:

http://search.barnesandnoble.com/boo...295402&afsrc=1

You may be able to find it at a public library, and it contains a chapter dedicated to your problem.

Best regards!

Willaroo

Hi. Thanks for your input, I really appreciate it. I will try and locate a copy of that book. So I guess it is not quite as straight forward as dividing the control surface into two equal parts? I have cut the control surface from the wing, I probably should’ve mentioned that. Photo attached. So, I presume that you would split to form flaps and ailerons? Boeing do, surely they can’t be wrong?! A question I do have is what would I be missing (apart from the obvious) from a control point of viewif I was to not add flaps and have only ailerons? Also, if I shorten the aileron by using a portion of it as a flap, would the aileron still be up for the job it was meant? I am a complete novice if you hadn’t already guessed.

MinnFlyer

My Feedback: (4)

You can't put flaps on a delta wing, they will act as elevators. Drop them, and it will be like applying full down elevator

AERORICH73

Hi there: I have found Andy Lennon's book, Basics of R/C Model AIRCRAFT DESIGN, very helpful in doing model building, and redesigning. Hopefully you can find an edition to look over before purchasing one. Good luck on your build, and let us know how the construction is going.

Rich S.

Lnewqban

You are welcome, Willaroo!

I have just consulted the chapter 23 of Andy Lennon’s book, and I have learned that flaps are not necessary or practical for delta wings, which have a high critical AOA; therefore, this type of wing are able to fly at high AOA before stalling.

For any wing, the deployment of flaps produce a strong pitching moment that only a stabilizer-elevator can compensate for.
Obviously, a delta wing doesn’t have a tail or any other control surface for this function.
Spoil-flaps, small split-flaps and split-drag rudders have been used in just a few designs as means to slowdown this type of models at landing, rather than to produce added lift.

Hence, as MinnFlyer has advised above, flaps are not recommended for this model.
However, since they can be used in models that have a tail, I include the following reference:

The chapter 14 of the referenced book contains tips for design of flaps for model airplanes of regular layout.
Among them, there is a rule of thumb for the flaps-ailerons proportion that you need:

For plain and split flaps, the flap chord should be 20% of the wing chord, while the ailerons should be 25%.
The range of deflection for these types of flaps should be 0 to 60 degrees.
For slotted flaps, the flap chord should be 25% of the wing chord, while the ailerons should be 25%.
The range of deflection for this type of flaps should be 0 to 40 degrees.
Spanwise, the flaps should be 60-65% of the wing semi-span, while the ailerons should be 40-35%.

Regards!!