I just maiden my Fliton Votec 351 with OS56 alpha 4stroke today. I notice the plane has the shimmies while flying. My old 25size 2stroke trainer plane never had the shakes, so Im kinda disappointed with this new one. Fliton specifies .56 to .63 4stroke engines for the votec. And Im using the recommended engine. However Im using 13x6 prop rather than their recommended 12x6 prop by Fliton. Could that be the problem? But the OS56 manual specifies 13x6 or 12x6-8 prop is okay for this engine. I also notice while on the ground at idle speed, the plane vibrates ALOT, but throttle up the vibration goes away. Could it be 4strokes all vibrate too much? My friend (veteran pilot) says its the wind, but im not too sure of that. Comments appreciated. Here's the video of my maiden flight, but you cant see the shimmies on this video (mainly bcos the camera shake is far worse):

http://www.youtube.com/watch?v=H-8vuFOwqek

Looks like you have some slack or something in your control lines. If you have a pull-pull cable rudder system, make sure you have the cables tightly adjusted when at neutral.

Did ya balance your prop?

You mean it's making a funky loud noise?
If it's that, it's from fluttering from the control surface. Too much air speed
or your control surfaces set up arn't up to par. Gaps in the hinge line, Hinges mis-aligned, flexing control rods.
Rounded control suface TE will also cuase more fluttering.

If it's a new engine, it needs time to break in.
Yes, more torque less rmp usually means more vibrations at lower rpm.
Maybe some of the screws came loose. Either at the mount to firewall or
the screws the holds the engine to the mount.
Try to twist your engine off of the mount to check it. Look for any slight signs of the enigne lifting from the mount.

I generally drill through the plastic enigne mount and use nuts on the bottom.
I also use allen head screws heads becuase using a screw driver I can't get good torque.
By using an allen wrench I can use pliers to grip the allen wrench and apply more torque.

There's also soft mount available.
Kind of like the engine mount on your automobile. If it dosen't have one, It'll make a heck of a racket and the engine
will idle very, very bad.

from the video it could be the wind..what was the wind like that day? could it be your thumbs..or some kind of glitch...how was the range check?

Ahh.... yes I did noticed my pull-pull rudder lines were a bit slack after the flight. I will tighten them up again. Thanks!

I didnt. But its a brand new Kato made in japan glass nylon prop. Never hit the ground or dented before. Do props need frequent balancing?

Wow. Thats very good information. Thanks!

Well the wind was kinda strong, but luckily it was headwind blowing parallel to the runway, so we decided to take off. If you watch the video, you can hear the wind noise. And on one of the landings, wind shear made the plane nearly crash, but my friend managed to correct it just in time! Radio was working perfect.

Looks to me like the cause is the wind and thermals. When there are thermals one of the wings tends to go up suddenly in smaller or higher increments, that is why you have to correct the flying path almost all the time.
As the wing they affect heavily to light planes like the Fliton.

Yup, what I saw in the video looks like any of my small lightly loaded models, when they hit a gust of wind...

No biggie.

Remember that even if the air is still on the ground, you can hit gusts at altitude, and/or thermals.

The flight video doesn't show the actual shuddering but does show low pilot skill for a windy condition. Sorry if I offended you. Anyhow if vibration is major problem that is probably due to prop not balanced. don't need to be done often just once unless it gets damaged. the other items mentioned are also important. If you have digital servos in it that could cause some of the unsteady flying due to their fast response. Try adding about 60% of expo to all surfaces. Wind and flying skill was most apparent thing I saw but if it's vibration that's another thing. Yes 4 strokes do vibrate more especially at low speed and perhaps rich mixture. Prop balancing very important.

Thanks for all your replies. Im pretty sure it's due to the loose pull pull rudder cables now. I had to tighten it back quite a fair bit to get rid of the rudder slop. It must have been due to all the snap rolls my friend did. Thanks again guys.

If your hing lines have any gap, use some electric plane hinge tape and seal the gap up. Just make sure you still have movement. Air thought a gap will cause the surfaces to flutter. I didn't see any evidence of that in the video, but it is a good thing to eliminate before it can cause problems.

What I saw on the landing approach was a plane that was about ready to stall. It didn't have enough air speed to answer the controls well. It is best to keep up some air speed until you are just off the runwan then cut power.

On a windy day you have to keep in mind that your mind gages speed in relation to the ground, not air speed. The plane needs air speed to keep flying. IF you are flying up wind, your air speed should be above above stall speed if the ground speed looks OK. On the other hand on a down wind leg, your air speed may be near the stall point with the same ground speed. Also remember that the inetera of the plane is related to ground speed. If you are on a down wind leg, and your air speed is near the stall point, turning up wind will give you more air speed for a bit. The reverse is also true, If you are flying cross wind or up wind at near stall speed and turn down wind, you wind speed dropps off to the point you will stall. I lost my 4 * 60 like this a couple months back. You need to keep your air speed up above stall speed until you are inches off the ground on a landing. The first indication on most planes of a near stall is that the controlls go mussy and you get the all over the place approach as shown in your video. The plane is slow to respond to the controls until you have over controled then it jumps to that control which is to much. You correct and in turn over correct and the plane has a very unstable approach. Just a little more speed will smooth this out.

Don

Thanks for the tips. Much appreciated.