Well so far I have crashed my Seagull Extra 300S twice. And I'm thinking its because it's tail heavy.

Today I went for the re-maiden flight after the repairs from the previous flight. I balanced it upside down with the CG point at 4" from the wing leading edge at the fuselage. I also had it balanced laterally. Engine is a Saito FA-100 with a 14oz tank....and yes I balanced it with the tank empty. When it took off, it immediately climbed. I had to to give it a LOT of down trim to get it to fly level. Then when I went to try and turn it, it snapped and started spiraling towards the ground. I saved it and tried getting it back to the field to land, but when I tried turning again it snapped and dove for the trees. I killed the throttle and hoped for the best. When I found the plane, the bushes has saved it and the only damage was the tip of the left wing.

I can't understand how it could be so tail heavy with it balanced at 4".

Anyone else that has a Seagull Extra.......where is yours balanced at?

Hey Connery,

I have one (I LOVE it), there are black stripes in the wing, I use them as reference for balancing.

Just turn the plane upside down and ask someone to put their finger under the black stripe at the end of the wing, you do the same (on the other wing of course ) and lift it.

It should give you an idea of the CG location.

The manual calls for 4cms (about 1 1/2 in) at the wingtips.

Joseph

How much throw are you using for the elevator?If you you are having to trim an excessive amount of down for level flight,you may have to put in some down thrust at the motor.

Downthrust wouldn't account for the plane snapping in a normal turn.

If I balance it where the black stripes are on mine, it will move the CG back even farther and make it even more tail heavy.

I'm going to try moving it forward 1" and see how that does. What really shocks me is that even with it being a little tailheavy with the tank empty, it should be nose heavy with 14 oz of fuel in it.

Geez,

did you try 4 CMS at the wingtips?

I'll have to check that out after I repair the wingtip. None of the planes that I have built measured the CG at a point measured at the wing tip.

Well, that's what the manual says on page 19 [&:]

It is weird tho, mine balanced exactly at 4cm at the wing tips with a TT91 FS and 8oz tank.

I used a 12oz tank, but CG shifting was pretty bad as the fuel level got low. CG is kindda critical in this plane since it's not very light [&o]

Well there's the problem. When read that part in my manual, I stopped reading after the "4cm from the leading edge". I "assumed" since all the models I've built have always had their CG listed as measured from the leading edge at the fuselage, that is what was the case here. When I realized that 4cm at the fuselage was WAY too far forward, I did a search on here and found that several people had balanced there's at 4" from the leading edge at the fuselage, so that is what I used. I just went and measured on the good wing tip and 4cm at the wing tip equates to about 3" at the fuselage. So my CG is about 1" too far back. That would DEFINATLEY explain the flight characteristics I experienced

I will have to add some weight to balance it out even with the Saito FA-100 on the front. The reason why is that I had to move the firewall back about 3/4" to allow for the bigger engine to put the spinner backplate at the proper distance from the cowl. So even with the bigger heavier engine, the weight isn't as far forward as a smaller 2S or 4S would be.

Oh yes it would [:-]

I'm happy you found the problem

Joseph