Nobody answered you, John. Perhaps in this thread, it's because the stock setup are continuous tubes from fuse exit to the former just behind the servo. I did both elev and rudd stock using those guides, and so far, so good. They center well, have good geometry of travel (considering the excess Ackerman that is built in and SHOULD be corrected).

I'll tell you my technique on OTHER airplanes, though. And this isn't sarcastic.
Carve/cut as needed I try to use a straight edge looking down from the top of the fuse, holding it from control takeoff to servo arm hole. Eyeballing, I put a horizontal hash mark roughly where the hole will be. Then I do the same thing on the fuse SIDE, and mark where it intersects that original mark. Then, I make a slot, about 1/16" wide, far enough in front and behind that mark that there won't be any rubbing. Works for me.

There are a lot more scientific, analytical, and anal-retentive, obsessive compulsive schemes of arrival at the hole location. For me, I like the "guess, mark, cut, make it work" approach. Less time, less stress, more fun.
But not as pretty.

What does everyone think a good starting point for the CG is??

I'm with Bob on the metal hinges. I've had planes before with them and, alignment, waiting on epoxy, Rf noise, waiting on epoxy, rust, waiting on epoxy, sloppy feeling and waiting on epoxy kind'a made me not like them[X(]. I've had great success with the Radio South "blue" CA hinges but, I don't know how they are compared to the available slot in this application.

Great info here, thank you to all!!

A very Merry Christmas to all....

Dave - post 196 of mine suggests Sig EZ hinges. That's what I used, because they are a lot thicker than the Radio South, but in this airplane because of the pre-made slots, you need the thickness.

Starting CG - NOT 7.00". I started there, and it was very nose heavy, needed LOTS and LOTS of down elevator inverted. Others here (tommys, swlarcham) have flown theirs at 7.25" aft of leading edge at the fuse side and report great improvement. That's where I'm setting mine with the ST 2300 for next flights.

Sorry I can't say when that will be - it's 8 degrees, below zero wind chill, and not much change forecast for the weekend.

7.25", gotcha. I've never even seen the Sig hinges, I'll have to get some and check 'em out. Our LHS is, well, a little behind the times. I ordered one of the Tru Turn wide slot spinners designed for the thick chord 3D props and he said, "I know exactly what you want." He ordered a 1.20 slot spinner and told me they didn't make anything bigger. I like the guy and will support him but, I bring in printouts from the net to save the confusion now....

Regarding your search for an alternate source for the long DuBro horn take offs. I've seen these things, or something close, at Home Depot or Lowe's. I'll try to find 'em again next time I go up there...

The DuBro ones I have on one of my "flip flop" planes seem like they could rotate on the 6-32 stud rather easily in a push-pull arrangement. I used a jamb nut on 'em. Has anybody else had any problems like that with them??

tph1,
The stock mount is like the Dave Brown except the bar with the engine mounting
holes is one piece , not split like the stock one. The Dave Brown mount seems to
work OK but I'm no expert in this as this is my first 4-stroke and my first D-B mount.
I have decided to modify the nose on my second one and install a Hyde type A mount.
I already have the mount and after some measuring it will be a fairly easy modification.
The Hyde just looks like a better mount and they ARE the best. Central Hobbies has
them on sale now at $59.95.

I am flying with CG a 7.25" from leading edge of wing measured at fuselage sides and
have no mixes in Radio for knife edge , etc. Works for me.

Check Tru Turns web site. You can order directly from them and they can modify any
spinner as you want it and anything you want is always available.

I used Radio South 1/4 scale CA hinges and they worked perfectly. Be careful removing
the metal ones and you won't pull out much balsa. I have never had a Radio South hinge
fail and I have been using them for quite a few years , just make sure you use the proper
installation procedure.

I used the stock pull-pull tubes and they work great , I see no reason to change them.

tommy s

Elevator takeoff solution - maybe - ya'll look at this and tell me what you think. This was made from a steering arm, removing the 5-32" wheel collar, drilling through the plastic, and threading it on. Drilled a clevis attach hole where ever I needed it.

Anyone think of a reason this wouldn't work as well as the "high dollar" DuBro (unavailable) parts???

thanks Tommy

Hi Bob,

If you have time would you read this article and let me know what you think about the control horn offset as outlined in it.
http://members.cox.net/bdfelice/Ackerman/ackerman.htm

Thanks,
Bill

Bill,
That is a great explanation of why the stock control horn set up on the Excelleron
works very well. My elevators move just about 1/2" up and down and that amount
of movement is more than enough for any maneuver I want to do. When fully
deflected the non pulling cable might lose a little tension but it is very little , not
enough for me to make any changes. The tension change is so slight you cannot see it
and can barely feel it. If the non pulling cable was getting tighter then I would worry.

tommy s

Hi tommy s,
yes, it makes you stop and think. Here is another set of diagrams that approach it some what differently.
http://www.swbmfg.com/rudex.html

Bill

Very nice diagrams - are they yours?

E.

In reply to Tommy S.

That is exactly correct. You want the cable not being pulled to maintain the same tension or slack a little. You don't want that cable getting tighter. It all has to do with where the pivot point is in relation to the hinge line. I have read many peoples' opinion that slack in the non-pulling cable will cause control surface flutter. I don't think it can happen. For flutter to occur, the surface has to either move against the pulling cable or against the airflow over the surface.

The problem with the stock setup of the Excelleron is that it places the pivot point too far aft, and THAT results in the non-pulling cable actually increasing it's tension as the PULLING cable approaches it's max deflection. THIS produces assymetric tension on elevator halves, and believe me, guys IT IS A PROBLEM.

What it creates is assymetric elevator travels near their limits as we set them up, and that produces corkscrewing. Hard pulls like square corners, or pushes, like we have in the Vertical Square Eight DOES CREATE troubles.

What I've been searching for, and solved, with the help of others, I might add, is the "neutral" Ackerman, and that is with the control takeoff exactly over the hinge line.

I'll update with better photos after I re-string the elevator pull-pulls.

On my Excelleron using all the stock hardware, control horns, etc , when the elevators
are at full deflection the non pulling cable loses tension. Just checked it again to make sure.

tommy s

What is the position of your clevis attach point referenced to hinge line? Forward, aft, or on? This is interesting variation!

Fortunately, the LHS had the Dubro steering arms. They have the proper locating of the arm on the diameter. Drilled through easy enough, then threaded on and put new clevis attach holes ON the hinge line.
An example where the theory is correct. Thank you, Mr. Ackerman. I have all four clevis take off points exactly the same distance FROM the hinge line, and they are all OVER the hinge line. So now, the PULL side pulls, constant tension as near as I can tell, as the opposite cable slackens slightly. The travel of both elevators is now symmetrical out to the maximum, and they track together.

Can't wait to fly it now that I have this fixed.

Bob,

All right, I'm starting to aquire the stuff!

My 2300 is in the shop, I got it for 125.00, brand new, can't beat the price.

Excelleron is on the way.

I just need to know the specs on your Mueller header, I know it's a KM wrap-around, do you remember what the drop is?

Thanks a lot,

Ken

Ken - I had him make it 1 9/16", and that's based on measurements I made. I'm *hopeful* that it's right. I also had him put in 2 degrees right thrust offset, too.

Was hoping it would already have come, but not yet.
That's okay, as I did all the pull-pull rebuilding today anyway.

Hi Eric,
No not mine. I'm sorry if I gave the wrong impression.[:-] I did not notice that they gave no credit for the source. These were links that came up in another topic in the Pattern forum.
Here is a link to that thread.
http://www.rcuniverse.com/forum/m_24...tm.htm#2405772

Bill

Double post - deleted.

Aerobob,

Where did you get your eye bolts that you used on the rudder?

Tower, and most LHS will have them. They are a Sullivan part, 4 to a bag. 2-56. Clevis is a Goldberg. I'm a firm believer in nylon/nylon connection points for minimum friction, minimum slop, minimum wear.

I glad you commented on the nylon to nylon connection I wasn't aware that it was better than the dubro with the steel pin connected to a nylon horn. But from now on i'll use nylon to nylon. I realize this may be your opinion but I respect it.

Just based on my experience, the steel pin clevises of various flavors seemed to always wear the plastic control takeoff parts. I first went all nylon about 8 pattern airplanes back, and use them exclusively now, even on my 2M pattern planes. Amazing how long these nylon to nylon parts will last with no wear.

Try it; it doesn't seem to work for everyone, but that's why there's like 10 or more brands of control horns and clevises out there.

Bob,

Maybe I'll wait, before I get a hold of Karl, and see if your's fits.

Ken