Hi there
I just go my SR, and bumped into a question:
The Canard links system supported seems rather soft - even if I swap them with musicwire as some of you. The SR will be equipped with a 145 N turbine, so I want good links.

My suggestion is to mount the servoes directly through the sides of the fuse with the servohorns sticking out, and mount normal ruderhorns on the canard. Would'nt that be a lot better than original, even though the line of push/pull will be angled in respect to the hing-line??

That might work... the elevator hinge line is a pretty extreme angle, so yu would have to try it to see if you can make it work without the linkage binding. I wasn't too crazy about the setup either, but I went with an all moving single surface canard..(a borrowed idea...)

Please e-mail me concerning your canard setups. Thanks.

e-mail : [email protected]

Best Regards,
Todd J. Walters

Propellars,

If you have not used the search function; may I suggest you do so. You will find lot's of info on the SR.

You fail to mention where you feel the weakness lies, whether it be in the actual wire or if you feel the wood is too soft, etc...

The stock wire supplied is definitely too flimsy, but not something some 1/8 music wire should not cure. Also suggest you add a reinforcement plate to sandwich the fixed portion of the canard assembly to the mounting plate.

If the wood appears to soft; some carbon fiber strips inlaid span wise should cure it's ails.

Countryboy - I have read ALL info about the SR more than once , and I keep on re-reading it.

I dont like the system using torsion-rods. Even a 1/8" music wire needs to be supported and I expect there will be some free-play in the bearings along the wire.

Anyhow, my (adjusted) sugestion is to make the following:
Servo's behind the canard, direct links in 90° angel to hing line. This would give optimal connections:

you would have to make sure that with full nose down (ie elevator goes up) that it does not hit the push rod. I considered this idea, but settled on an all flying canard.

Good luck with your building...

Nony - yes I'll consider that . Mich Reves says 30mm up/down throw for the canard. I will design it for allowing 40 mm up/down, that might be enough, or how much canard throw do yoy guys have?

I don't have a SR but I have seen plenty. The best arrangement seems to be servos in the fuselage side under the canards, a short stiff linkage to those robart horns with the ball links to allow for the raked back hinge line.
If you go for the all flying route I suggest that you place the pivot at 25% of mean aerodynamic cord.
Regards.

John

thanks John - If I understand you right, then this was exactly my first idea.


Sorry, I dont understand what you'r saying - Could you rephrase that???

Propellars,
If you make an "all flying surface" such as a canard or tailplane it is important to get it aerodynamically balanced. This is achieved by pivot the surface at 25% of mean aerodynamic cord. A cord line is a line draw from the very leading edge to the very trailing edge through the section. The mean aerodynamic cord (MAC) line divides two exactly equal areas of the surface in planform and would be parallel to the fuselage centre line. This is easy with a parallel cord surface ( 50% of span) but since yours is tapered you will have to work it out. You could draw it out on graph paper, guess roughly where the line should go and then count the squares, correct draw an new line and so on until you are satisfied that you have the MAC line.
Next, measure back from the LE 25% of this cord and mark this point.
Then you need to get a set square on the fuselage centre line and join it to the 25% mark, and draw this line in.
This is the pivot line. With this pivot position there will be zero aerodynamic load on your servo.
However, you're not finished yet. You now need to statically balance this surface to prevent flutter. This is merely a matter of balancing the surface on the pivot by adding weight to the light side. If you do this the surface will not flutter.
Regards,

John.

Thanks again John, but I'm so sorry, but I'm afraid I still cant follow you, my technical english is'nt that good.

I get your meaning: aerodynamic balanced and static balanced gives "no" flutter, but can I aerodynamic balance a hinged controlsurface?

IF I was to make an all-mowing surface, I found this nice program to calculate the CG. I supose your advise is to place the pivot in the CG location?

http://www.geocities.com/flyawaysrc/mac.html


My SR is made with lead-balanced controlsurfaces, so I supose I'm on the safe side conserning flutter.

Hi Lars, have also a look at: http://www.jets.at/Pendelleitwerk.xls

Regards,

Spunki

thanks, Spunki. I dont dare to make "full mowing surface" - pendelleitwerk, but your program is nice though.