F18 Elevator
 

I have a Skymaster F18 and although all the linkages to the elevator ( or more correctly, the stabilizer ) are new, there is inevitably a minute amount of free play in the clevis to control horns. This movement is then exaggerated, due to the leverage and results in about 1/4 inch of slop. Is this acceptable? I'm worried about flutter on a model this quick.
Thanks,
John

RE: F18 Elevator
 

John, after having built 3 of these now I would not use clevis of any kind. My choice is a bolt on ball link, no slop and cannot pop loose. Dubro makes several you can choose from. I also make my pushrod from 1/8" cold rolled steel. Cut your own threads, very stiff and the link will self thread right on. Use a 4-40 die to cut the threads. Good luck with her.

RE: F18 Elevator
 

What about using a ball link system instead of a clevis? We have a few skymaster f-18 flying at our local field but I dont remember seeing any large amounts of play in them.

Rob Lynch

RE: F18 Elevator
 

Thanks, I'll take your advice, I don't feel comfortable with the present setup.

John

RE: F18 Elevator
 

On mine (JL), I drilled out the horn and inserted a nylon bushing for the clevis. Dead tight and pushrod alligned with the center of the horn.

- Thore

RE: F18 Elevator
 

John,

I had the same concern on my SM Raptor!
I checked with a few individuals that have successfully built and flown this model as well as other SM aircraft owners.
And I was told that a little play (1/16) in the bushing is expected and pretty typical of SM aircraft.
I also changed out the SM links and rods for Dubro 4-40 Heavy Duty Ball Links and Turnbuckles.

RE: F18 Elevator
 

Hi,

The ball-link idea is a good one. I don't use the Dubro stuff because I find the plastic too inconsistent. Sometimes, it's too brittle--sometimes too soft. I use the ball-cups and ball-ends from the RC car side of the hobby shop. There are several aftermarket ball setups that are very beefy and the ball stud is hardened steel. There is no binding at all, and they're not coming off in flight. Good luck!

RE: F18 Elevator
 

I,ve just taken it to the flying field for range tests and engine run ups and a few of my fellow flyers have pointed out that the movement seems to be because of slop in the actual stabilizer pivot. As I didn,t build this model, can anyone advise me does the pivot run through a bush or bearing and is this normal or what can be done about it. It looks a ***** to get at.
John

RE: F18 Elevator
 

A little play is expected (1/16) is ok (1/4) then you have yourself a problem. The pivots run through bushings and can be replaced if they are of a bother. You would have to heat up the bushings to remove them. Then you need to route out some bearing pockets for 8mm bearings and epoxy them in. Before you do all that replace your hardware with the ball links.

RE: F18 Elevator
 

g'day john, we (test pilot with the steely nerves and me) have just completed test flight #8 on s/m f18 and i thought i'd share some results with you. i found the same sort of slop in the brass bushed elevators, to me totally unacceptable on a high performance jet, fixed with jetlegend twin ball bearing blocks and a bit of surgery(see photo), also extended torque arm to 45mm, this gives 40mm trailing edge movement with 140% servo travel, 10% for trim, and new servo mount to realign pushrod, sounds like a lot of work but our results leave me feeling totally vindicated. started with c/g on front spa but have since moved back approx 2 cm( don't quote me on that! approx!) with much better handling at flair, cg checked with rear tanks full, front tank empty(i drain front to rears to header) its heavy, but flys absolutly on rails, the s/m and j/l hornets are good flying models, with a bit of attention to detail they are superb flying models. pst 1300 gives plenty of power and excellent performance. a friend took some video and will post here soon, look for tiger hornet vid or send pm for more details

RE: F18 Elevator
 

Blackcat, I,ve sent you a PM.
John