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Update continued:
Beveling the elevator leading edge.
Cutting the solid balsa tips.
Continued...
Beveling the elevator leading edge.
Cutting the solid balsa tips.
Continued...
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Update continued:
Ready for sanding.
Installing the control horn.
Ready for covering.
Oops! Forgot the holes for the mounting screws. That and the stabilizer saddle is next.
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Art,
Really glad you are using the elevator horn method as drawn on the plans. People tend to shy away from it because it is viewed as difficult or sloppy in service, but if you spend a bit of time getting the slot in the sliding square tube right, you will be rewarded with a nicely functioning setup. The trick is to get the top hole just the size of the horn width, and the bottom hole slightly bigger to allow the horn to angle forward or backwards as the elevator is moved. Start with the top and bottom holes just big enough to let the horn pass through, then elongate the bottom hole to allow movement. You may have to bevel the top hole ever so slightly to allow the horn to "swing", but not much. It's not complicated; just needs a bit pf patience, and you will be rewarded with a slop-free quick-mount elevator with no need to access clevises with attendant access holes in the fuselage.
I assume it's coming, but the front part of the stab middle section gets filled with a block of balsa (grain vertical) to house the front mounting screw.
Looking great!
DSComment
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I'm out of town this weekend so no progress to be made but I though I'd share one little detail that Dave Smith brought to my attention. The tail has squared off tips. It's an easy fix but I hadn't noticed it. Thanks Dave!!!Comment
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Update:
Got back in town in time to work on the Cherokee a little this evening.
I cut and shaped the saddle and pinned it to the stab.
Then I counter bored and drilled thru for the plastic sleeves, 6-32 screws and neoprene washers.
The plastic tubing will act as locating pins and a hard shoulder for the screws to tighten against.
Test fitting and leveling the stab by sanding the bottom of the saddle.
Continued on next post.Comment
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Update continued:
Then I epoxied everything in place and aligned to the wing rod before the epoxy set.
The plastic tubes are epoxied to the saddle. The holes in the stab are hardened with thin CA.
Feels nice and solid.
That's it for now. Next will be the elevator control rod and quick connect mechanism.
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Update:
I have the elevator control mechanism done.
Here is the carrier sleeve and mounts.
This is the top of the inner tube which the control horn fits into. The size of this hole is very critical. It needs to be a perfect slop free fit when the elevator is at neutral.
This is the bottom of the inner tube. Nothing critical here, the hole just needs to be large enough not to interfere with the control horn.
This is the control horn. The tang is tapered to allow full throw of the elevator with no slop throughout the movement.
Continued on next post.Comment
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Update continued:
Here the stab and elevator are mounted and the control horn is through the inner connecting tube. You should have a slop free fit at this point.
Here the elevator is deflected full up. The control horn has to be tapered very carefully to allow this movement without any slop.
Here it is deflected full down. It takes a lot of trial and error fitting to achieve this movement without any slop.
I mashed the end of the inner tube and drilled it to fit a 4-40 clevis. Then I soldered the clevis to a piece of all-thread and screwed it to the Sullivan control rod.
That's it for now. I guess I'll go ahead and do the elevator and rudder servos next.Comment
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I was explaining the procedure for getting this mechanism to work properly to my son who is a machinist and mechanical whiz. The first thing he said was "you should have just used a fork and pin". In other words the control horn would be forked with an exact sized slot and a pin would be fitted in the slider to engage the fork. I didn't try it but I think it would work great and not require all the trial and error fitting.
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Update:
Not much today but I did get all the gussets done. I would recommend doing the gussets before the stringers and doing the stingers after all the interior work is done.
All right the elevator and rudder servos are next.Comment
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Great thread! I put the 'pin and fork' idea on paper and put the info in my kit! Tell your son.... Thanks!Comment
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Update:
The rudder and elevator servos and the control linkages are done.
I mounted the servos per the plans with the elevator upright and the rudder inverted. I made the servo tray removable so they can be accessed by removing two screws and sliding the tray out.
Mounted the control rod sleeve using plywood standoffs and Gorilla glue.
Continued on next post.
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Update continued:
Added balsa filler to mount the rudder control horn.
I made the control horn out of some scrap aluminum.
This is the rudder servo looking from the bottom. I used crossing pull-pull cables in order to get a clear shot through the fuselage sides.
The control horn is mounted through a slot cut in the balsa filler. Does anyone know what the control throws are supposed to be? I want to make sure I have enough bevel on the rudder.
That's all for now. I'll start working on the bottom next.Comment
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You can't have too much rudder. 45 degrees would be the right target, but not the end of the world if you fall slightly short. The Cherokee is pretty forgiving; if you have the ailerons set up right there is very little adverse yaw. The 1/3 Cherokee flies pretty well on just ailerons or just rudder :-)Last edited by Dave Smith; 08-01-2015, 06:16 PM.
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