Hello All

Just wondering if anyone have some bellcrank pics for installing the 1/8" rod pivot type like the Tom Morris or Brodaks in the Score. I have looked over mine.. and it doesn't look like there is enough room in there to work along with ball link setup (the spar gets in the way).  unless I relocate the stock plywood mount to a lower location, then add the other piece on top.

Thanks in advance.

Joe,
The vertical CG of the Score is somewhat above the stock location of the bellcrank.  Makes the plane bank to the outside of the circle both upright and inverted.  I guess that's better than banking to the inside of the circle........

Jim

Hmmm..... not too sure what you mean by vertical CG.   Do you mean the outboard wing tip banking up or down vs the inner? 

Hi Joe

I am by no means an expert, but I think your description of adjusting vertical CG is just a little off. It is checked by hanging the model by the leadouts, but you are looking to see if the wing hangs straight down looking from the front or back and you would adjust by adding weight to the canopy or landing gear. A better method if possible would be to reposition the leadout exit up or down on the tip till the model hang straight down.

Adding weight to the nose or tail while hanging from the leadouts is confusing to me. I thought that some have been checking the leadout position in relation to the longitudinal CG by hanging the model from the leadouts and insuring the nose hangs lower then the tail.

I am sure more qualified people can clear this up.

Hi Guys,
Robert, you are correct vertical CG is about wing alignment on the "roll axis", that is, is the outboard wingtip up or down in relationship to the lines. Joe was measuring the CG on the "yaw axis" , in other words is the nose located inboard or outboard when looked at from the "top-view".  This CG location also directly impacts the planes ability to turn on the "pitch-axis", because as you change one CG you also change the other CG.

Over on SSW Al Rabe in his Mustunt IV building series had a photo of the plane hanging by the leadouts , next to a wall that is checked to be plumb and true. The wheels are only an inch or so away from the wall.  You measure the distance from the wall  to the "front -view" centerline of the leading edge of the wing, on both the inboard and outboard sides, of the wing, measured  at an equal span from the "top-view" root chord centerline of the wing. This will work with straight wings or wings with dihedral.

I like this idea much better than messing with plumb bobs , strings ,and etc. The wall gives you an easy, instant and repeatable reference point to check the vertical CG of your airplane.  It was one of those "Why didn't I think of that " moments  , the instant I saw Al's picture.

One idea that I haven't heard anyone mention they have tried yet is to use a laser level projected vertically onto the"front-view" centerline of the leading edge of the wing right next to where a centerline is drawn. Check if the laser line and the ink line are parallel to each other to find out if the vertical CG is correct. This obviously would not work with dihedral wings but might be do-able with straight wings.

I make no claims at expertise but I think what I said was accurate.
 
I am also getting ready to replace the bellcrank with a Tom Morris system in a TF Score and would like to see photos of the best way to accomplish that particular job.

PS -I just saw Joe's last post .
Joe moving the leadouts front to back only changes the "yaw-axis" CG.  Let me give you an example of vertical CG.
You may have seen pictures of biplane stunters and the leadouts are usually mounted on an inboard strut and not coming out of a wing. The reason they are on the strut is that is where the vertical CG is located  that would let wings fly level with the lines. If the leadouts came out of the bottom wing, the plane would fly with the outboard wing tips flying way down in relation to your lines.
Someone gave me a low-wing plane that was imbalanced like this once, and there is not enough flap bending or trim tabs available to fix that mess. Forget stunting, when you get inverted you lose all line tension and it comes in on you big time.

Back, in the 70's Tom Dixon was the first guy I ever read bring up vertical CG issues in his Stephens Akro article.

Most stunt designs account for the vertical CG ,just fine, unless you change something. If a plane is designed for an inverted engine and you change it to a side mounted engine you will change the vertical CG, and so you may have to use heavier wheels or add wheel pants in order to restore the vertical CG. 
Some people do make vertically adjustable leadout guides or they may use temporary guides during final construction to locate vertical CG location and then glue in the permanent adjustable leadout guides at that determined height.

                                                           Pat Robinson

Pat,

Thanks for the information regarding vertical CG.  Obviously, I only knew about a method used for adjusting for yaw axis.  Sometimes, a little knowledge is worse than none at all.

Regards,

Joe M.

Hi Bob,
Thanks for the information.  My control system order hasn't shipped yet , so in the mean time, I am finishing up everything else on the Score.

                                                              Thanks again,
                                                           Pat Robinson

Hi Bob,

I saw your reference to *several* advanced wins...... *Several wins*=EXPERT! LOL!!

Around here, it has been so long since I even sniffed the podium it isn't even funny.  But, we have a bunch of pilots in Advanced who would be flying Expert in a lot of areas. 

If you would have seen me fly in Tennessee you would have kicked me back to intermediate 

What is you say about the blind hog, a couple wins in advanced around here don't mean nuttun other than the guys better than me either didn't attend or had an off day.. I remember calling a friend from one contest saying I'm in first place with 4 flights left and 3 of them can beat me.. Just so happened I was lucky that day but it's rare..

A Tom Morris 3 1/2 inch bellcrank will fit without any major mods. That is what I have in mine and it flys well enough for a couple Advanced wins. I don't have a big vertical CG issue but I have a side mounted Saito 56 which changed the vertical CG.

I used the stock bellcrank mount complete with the stock screw, I cut a bushing from brass tubing that fit the screw and drilled the phenolic bell crank out to fit the bushing. I made the bushing a tad longer than the bellcrank is thick so it's captured between washers. The bellcrank turns on the bushing but the bushing won't turn on the screw threads because it's held in place with washers and the nut.

I used a music wire insert for the carbon tube at the bellcrank, right angle bend and washers soldered to hold it on the bellcrank. A ball link at the flap horn and ball link to the elevator.

Thanks for sharing the info. 

I have a SIG 4" in mine right now, and i had to redrill the mounting hole about 1 3/16" toward the outboard wing for the reversed configuration.  I'm just thinking of changing it to the Tom Morris ones.

I too ended up using a 4" Sig bellcrank but did not reverse it and used the stock hole. I had to Dremel and file some wood out of the spar so it would not hang up on anything. The pivot is 1/8" music wire & is removable.

The photos show 2 different bellcranks. At first I considered a 4" Brodak but ended up using a 4" Sig.

Last week I flew another club member's Score with the stock crank and it handled fine. However, for some reason, I do not trust the stock leadout wire and crimped ends. I replaced mine with Brodak .033 cable (Sig .027 cable would be adequate). The ends are bushed with brass tube, wrapped with Sig copper wire and epoxied. Regards, EWP

Without a bushing the bellcrank will be pivoting on screw threads. Think not much different than using a rat tail file for a pivot.