I'm confused by this question....
form follows needs....
why cut the wing at all ?
If your talking full fuse why not  fit it over the wing or under the wing?

If you put the bellcrank behind the spar, the leadouts might bend enough to increase wear and friction past what you'd like - but maybe not. Perhaps though you could put the battery between the main spar and leading-edge spar (if you have one), and place the bellcrank inboard of the battery. Maybe you could counter the weight of the bellcrank by offsetting the battery slightly and re-route/bend the control rod to suit? I share your structural concern, although I've seen some wings survive OK, even when notched out past what seems structurally sound to me. 'just some thoughts.

SK

The ARF Flite Streaks we mount the battery on about a 30* angle. The rear of the battery is above the leading edge (actually resting on it) and front of the battery is below the wing center line . The weight is centered on the vertical CG.

The bellcrank is a little behind the spar.  It's aways behind the CG.

'usually kinda hard to put it anywhere else...

I listened.  He is wrong.

Choose your pack carefully: For a 550 sq airplane plan on a 4Sx2500, There are two main form-factor packs around that size.

* The "brick"  packs are around 35mmm by 35mm x 105mm.  Shorter packs mean that the weight of the back can be located farther aft (or forward if needed).  I have not had to notch an LE any more than 1" using short packs This shape of pack also enables you to look at a vertical pack (see Sparky's MC72) if you can make the fuse a little tall up front.  Plan B: use cheek cowls and run the pack ACROSS the fuse...

* The "Wafer" packs are around 28mm x 44mm x 135mm.  These packs have the advantage of lowest shift in vertical CG.  If you mount the bellcrank in a normal location you might box out the arm and let the notch for the pack go only 1/3 to 1/2 the depth of the airfoil and back to the spar.  Still have to pay attention to the CG but there less pain.  I recently took this approach. on a short nosed 1948 design.

* One approach I have not tried but that I believe would work is to use one of the thin packs but locate it in the WING 1 bay outboard of the bellcrank.  Center of the pack would be roughly 2" off center, if the pack weighs 9 oz then that is 18 n-oz or the same as a 3/4 oz slug of tip weight located 24" off the center - HEY the airplane just got 3/4 oz lighter!  Off course you have to work out details of carry through strucure (easy) and a LE cap battery hatch but shat should be no big deal...  Battery effect on CG will be pretty close to nothing, you will have to fine tune the CG the old fashioned way. 

As Windy stated and I believe Bill said also as long as its mounted behind the CG. Bellcranks mounted on boards don't have centrifugal force imposed on them. Gravity is not the same. I try to plot a design so that everything is in line. It makes for a plane where no weight is added to balance things.

Instead of hanging boards a test bed need to be built where we can shift the weight and bellcrank locations easily. This is the ONLY way I and many others will be convinced of this. Paper equations don't fly. Instead of moving weight around move point of tether (which most believe is the wing tip) (but forget the leverage imposed by the distance from center of belcrank to leadout guide) Let alone the centrifugal force added. But I am sure there are some pie times radius square formals that can be written down. But until you feel it in the handle mean ZIP.

So I say mount you bellcrank anywhere you feel it belongs and exit the wing where ever you think is best. Makes me no mind. I have given up in trying to reason.

Not directed at anyone person.

Just as I did with my battery mount standing straight up in front of the wing (I will let you know the results of this experiment soon) Test flights may take place Friday. In order to do this the tail must be light because it still has to balance. Having built only 4 electric airplanes it didn't take me long to see the obstacles that need to be over come. They are only getting better in feel as I move the battery back. No its not a cg shift. Take weight out not add to balance.

If I were going to do something goofy in belcrank mounting it would be to mount the bell crank on the outboard tip so that the leverage imposed by the lines running the length of the wing may overcome some of the yaw. But inline is most pratical.

I listened to what he said and he stated that if the BC is ahead of the CG you are always pulling the plane towards you and the LOs make no difference. Then he said if you place it anywhere behind the CG its ok.  I was really kind of shocked to hear him say the LOs make no difference.  I have flown one of his planes in Nats trim and it is quite obvious he knew the importance of LO position.

If you are in fact pulling the plane in at you in one aspect, BC ahead if the CG, than how can you NOT be doing the same thing in the other aspect, BC after the CG?  If you are pulling the nose in on forward mount you would be pulling the tail in on a rearward mount. That is not a logical conclusion.  AND I AM NO ENGINEER either but I can tell you what he said is not logical.  

At a glance it would appear with the BC ahead of the CG that the nose would be pulled in.  BUT, you cant discount the fact that there is a rudder on there helping to create the ACTUAL direction of flight.  The LOs position is then used to get the model as close to tangent to the circle.  

I am no engineer, math wizard (hell, I barely got out of high school geomtry, and my grammar sucks too), rocket scientist, statistician, excel guru, or whatever the name of the day happens to be.  But I can tell you after years of learning the art/Voodoo of trimming and really understanding the relationship between the LO position, TW, and CG position, along with a host of other little items that truly effect the model it doesn't take a rocket scientist, or any of the other scientist types, to figure out that the BC position is just about the least of ones worries when it comes to getting a model to fly straight, true, with repeatable results in just about any weather condition.......  That is the goal correct?  At least that it is mine.

This is not a engineering thing. Its logic. Draw it out on paper with the point of tether ahead of the CG. Point of tether is not the wing tip its the bellcrank pivot. Tether meant attached to. It is not attached to the wing tip. There is a mechanical advantage between the leadout guide and the bellcrank pivot. As long as this is behind the CG (according to Wild Bill) all is well. Put it ahead one time and see how it feels. No good! Kind of a double standard he states that is as long as its behind the CG in one sentence and it the next it don't matter. Oh well.

Now on your drawing move it back farther and look at the relationship between the CG and pivot. The longer axis will make it feel more nose heavy and it will also load the nose (or at least it feels that way)

I am done trying to make people understand this and you wont until you make a plane is this configuration (I have). So mount then anywhere you feel is best and put leadouts anywhere you think is best.

This is not a engineering thing. Its logic. Draw it out on paper with the point of tether ahead of the CG. Point of tether is not the wing tip its the bellcrank pivot. Tether meant attached to. It is not attached to the wing tip. There is a mechanical advantage between the leadout guide and the bellcrank pivot. As long as this is behind the CG (according to Wild Bill) all is well. Put it ahead one time and see how it feels. No good! Kind of a double standard he states that is as long as its behind the CG in one sentence and it the next it don't matter. Oh well.

Just so you know, I have never read the famous Wild Bill article you and others keep referring to.  My logic is found on the circle at the bottom of a fuel can and guess what?  It doesnt support what you have been saying.  But if it does for you then more power to you.

Not sure why you have to put the battery aft of the spar.  I have 5 electric ships and all balance well without getting into the spar. On the ARF Flight Streak the battery is angle above the leading edge but still way forward of the spar.

Joe

Very interesting thread.  I have been trying to decide if I should build the original Stiletto, which I believe is about 590 square inches, with electric power.  I haven't measured to see if a battery will fit without cutting into the leading edge of the wing yet.  Has anyone done this on the original Stiletto?  Any concerns I should be thinking about other than the leading edge issue? 

George

I've come to realize the smaller planes need the battery farther back. On a full fuselage with a 550 sq. in. wing I think I need to cut the center section out of the wing all the way back to the spar.

So how do you get that strength back? What size/type of wood do I need in the spar?

Would there be any problems at the lead out guide putting the bellcrank behind the spar?

Thanks,
MM

Where, in percentage of MAC, do you plan to locate the CG?