Originally Posted by antennahead

I have been flying my v1 S surfer for a long time. I originally flew it with a CG of 70mm and I felt that it was a touch tail heavy and it would tend to porpoise when in a power off glide. Recently I decided to use mt Ssurfer for an fpv trainer, but to do this I want to get the plane to fly nicely in a power off glide. I came back to this thread to see what others are using for a CG location and saw a few posts about using a CG location of 60mm from the leading edge. I rebalanced mine at 60mm and took it out to the field for a few test flights. I left all control surfaces neutral, and slowly added nose weight until the porpoising in a power off glide stopped. When It finaly stopped porpoising I rechecked the actual CG and it would balance perfectly level at 30mm from the leading edge Why would the CG be so much differnt from the vast majority on this thread?? I have to say, even with it this nose heavy, it still would glide forever!

So, do you now fly with that CG or what. My SS porpoises real bad but i have been reluctant to fly much farther ahead than 60mm. Have been moving a little at a time but too few days to fly to get it worked out. Any help from anyone is appreciated.
Dog

When does it porpoise,on throttle or off or some were in between.
I am also curious how other folks will answer you.
IF THEY ANSWER YOU.

I finally got some good stick time with my SS and then popped my GoPro on. Then, I played around with Windows MovieMaker.... Here's the video. I made the super hi-tech gopro mount in 5 min.... Not too bad for my first video......

First GoPro Flight with SS (3 min 54 sec)

Originally Posted by Limited flyer

When does it porpoise,on throttle or off or some were in between.
I am also curious how other folks will answer you.
IF THEY ANSWER YOU.

Mostly while trying to do glide test and when motoring slowly into the slightest headwind. Seems to fly sorta OK apart from the porpoising. Fairly new to flight so i like to go kinda slow to minimize crashes.

Originally Posted by bigdogg1

So, do you now fly with that CG or what. My SS porpoises real bad but i have been reluctant to fly much farther ahead than 60mm. Have been moving a little at a time but too few days to fly to get it worked out. Any help from anyone is appreciated.
Dog

3 months ago I would be telling you that the CG of an aircraft does not change. If the design was 60mm then that is what you use and then add or move weight so it balances at that measurement.

Now I am not so sure since my SS V2 flew for over a year at 60mm and now it is better at 70mm. While I haven't got a good reason I did make a number of modifications to the fuse. This could have made the CG change but it should not have.

I know that doesn't help you but I can only suggest you try balancing at a few different CG measurements and then perform a hand tossed glide to see if your plane performs properly.

Originally Posted by Eagle202

3 months ago I would be telling you that the CG of an aircraft does not change. If the design was 60mm then that is what you use and then add or move weight so it balances at that measurement.

Now I am not so sure since my SS V2 flew for over a year at 60mm and now it is better at 70mm. While I haven't got a good reason I did make a number of modifications to the fuse. This could have made the CG change but it should not have.

I know that doesn't help you but I can only suggest you try balancing at a few different CG measurements and then perform a hand tossed glide to see if your plane performs properly.

Seems to dive pretty bad during no power hand toss glide

Originally Posted by bigdogg1

So, do you now fly with that CG or what. My SS porpoises real bad but i have been reluctant to fly much farther ahead than 60mm. Have been moving a little at a time but too few days to fly to get it worked out. Any help from anyone is appreciated.
Dog

Do this, go somewhere that has grass, weeds, 12" min. because your going to thro your plane into the air and your going to watch what it does and adjust. Straight into the wind, if theres wind, you will learn even more. Dead stick, no power. Go get it, when you've got it right it will glide well past what you might have expected.

When do I get to fly the plane. Just got my Bix2 ready to fly (CG is 7/16" back of spec, etc,) I'm as ready as I'm going to get.

Tomorrow only gliders can fly until 12:00. I'm going to take my Bix2 to the glider guys, i have a friend (highly respected) that might help me get this into the air. I'm not signed off on, my 'ticket is not punched' I can't fly on the tarmac because I haven't satisfied all doubts that I can fly this thing without hurting someone. I wouldn't have it any other way.

DJ

Originally Posted by bigdogg1

Seems to dive pretty bad during no power hand toss glide

It is tail heavy. What is the CG measurement?

Re-balance the weight with the new CG 10mm toward the nose and try again.

It should be somewhere between 55 and 75mm. Good luck

I was incorrect with my first message. See the attached document about CG.

Originally Posted by Eagle202

It is tail heavy. What is the CG measurement?

Re-balance the weight with the new CG 10mm toward the nose and try again.

It should be somewhere between 55 and 75mm. Good luck

I was incorrect with my first message. See the attached document about CG.

I have that chart in my flight book, Thanks to you, I just don't understand the terms.

DJ

Originally Posted by Eagle202

It is tail heavy. What is the CG measurement?

Re-balance the weight with the new CG 10mm toward the nose and try again.

It should be somewhere between 55 and 75mm. Good luck

I was incorrect with my first message. See the attached document about CG.

Have use 60 to 70mm and most points in between Last attempt was at spec 60mm

I keep a 1/2 dozen copies of that "CG−position diagnosis via Dive Test" in my TX/Parts Flight Case to hand to anyone who is having trouble with getting CofG and flying 'powered' & 'gliding' set correctly.
-B!

Originally Posted by Sculptor

I have that chart in my flight book, Thanks to you, I just don't understand the terms.

DJ

Sculptor

I was told that if the plane nose dived then the balance point or false CG was too far toward the tail making it nose heavy.

If the plane suddenly rose then the balance point or false CG was too far toward the nose making it tail heavy.

The proper balance point or true CG would make the plane glide further out and slowly down.

Originally Posted by bigdogg1

Have use 60 to 70mm and most points in between Last attempt was at spec 60mm

What did it do at 60mm?

Make sure the elevator and ailerons are neutral. If they are off even a little the plane will be affected.

Originally Posted by Eagle202

What did it do at 60mm?

Make sure the elevator and ailerons are neutral. If they are off even a little the plane will be affected.

Trimmed and neutral each time new CG used At 60mmm porpoised pretty bad Wouldn't moving CG farther forward make it more tail heavy

Originally Posted by bigdogg1

Trimmed and neutral each time new CG used At 60mmm porpoised pretty bad Wouldn't moving CG farther forward make it more tail heavy

Are you testing under power or doing the glide test by hand?

It could be the motor thrust angle is off and every time you power up you have ot correct.

Or your control surfaces are way too extreme. Maybe reducing the travel distance or using a lower rate may help reducing control or over control.