What would be a good distance for hinges center to center on flaps and elevators. On a 60''span 650 square wing area. Flaps lenght is 24 to 26 inches and elevators are 12 to 14 long?    THANKS.

Might want to add a 5th to the flaps just inside the outboard hinge to double up at the tip. This is where they typically fail.

Bob- Is the outbd. hinge failure attributed to flap twist under an airload? -the tip hinge being furthest from the horn and under the most stress. I would think the control horn takes up alot of the airload forces (inbd.)

I tend to use 5 on the flaps. The spacing gets progressively closer as it gets toward the tip.

Bob- Is the outbd. hinge failure attributed to flap twist under an airload? -the tip hinge being furthest from the horn and under the most stress. I would think the control horn takes up alot of the airload forces (inbd.)

Don't know, never analized why, just know everytime I've seen a broken flap hinge it was at the tip.

I would think that on a tapered flap the loads on the hinges decrease as you go out toward the tip because of the reduced area.  Provided you put the last hinge close to the tip, say with only 1" of overhang, I dont think it is necessary to double up.  The horn bearing , provided you securely mount it to the TE, is a hinge itself.  I use to, but dont anymore, try and get the first hinge close as possible to the horn.  Then I realized that makes the alignment all the more critical.  For a given amount of mis-alignment, the closer 2 hinge points are the more binding will result as surface rotates.  So now what I do is put the 1st hinge 2~3" from horn, put the last hinge 1" from the tip, and evenly space the rest of the hinges.  On my last ship just recently layed out, my flaps are 22" long, I used 4 hinges and it came out exactly at 6" spacing between hinges.  I felt that was right at the upper limit of acceptable hinge spacing, and if flap would have been an inch longer I would have used 5 hinges.  So if your flaps are 24" I would go with 5 hinges. On the elevator I used 3 hinges and the spacing came out at 4.5".

Wing of plane I am currently working on in the bedroom.  Have to vacumn each day when I get ready for bed. 

The loads would decrease proportional to area, yes but the stiffness would also decrease which would account for flap twist. Since the flaps are joined at the root by a metal rod, this portion of the flap would be pretty stout. If hinges are failing at the outboard point it would be only due to wing flex (bend) or flap twist (torsion), correct?
Al Rabe has some good ideas by using a carbon tube for a LE spar.
This is my theory and is certainly open for debate. No argument intended.

I dont think there is enough wing flex to cause a hinge failure.  Flap twist is not a good thing for overall performance and surely complicates trimming, but that does not increase load on hinge, in fact it probably decreases the hinge load relative to a stiffer flap with no twist.  I think most of the failures of the tip hinge is because it was installed too far inboard from the tip.  With excessive overhang of the flap tip it is more likely to flutter..