OK.
Finally my Roo track straight now. For the time being anyhow.

I changed the mains wire from 4mm to 5mm with struts and robart tires to eurokit ones. I also filled the eurokit tires inside cavity with foam to make them sturdier in compression, as we saw marks in the sides of the robarts, that flex sideways a lot more.

I also changed the 4mm wire nose to eurokit nose strut.

On the first flight it tracked OK in the start, but I managed to land 1m wide of our tarmac, to guite heavy gravel (first jet flight of the season...). The nose strut lower part broke as this was cast aluminium and about 7mm in dia. At this state I still has the 4mm wires and struts in the mains. The mains also bent back heavily.

Then I made a new lower part to the nose from my earlier Yellow A-4 main strut and changed from 4mm to 5mm wire for mains crank/strut fix. After this the plane has been trouble free in 4 flights with 90 deg sidewind.

But... My friend has quite a similar setup and he still has problems with tracking. He has even sturdier mains now, but with robart tires and had problems with tracking. His nose setup also has a bit less lag. So I will advice him to make two changes, that should help.

- More lag to the nose steering. With lag I mean the distance between the steering rotation axis to wheel rotation axis.
- Stiffer, low profile tires to the main, so that the rubber will not flex under the weight.

We also use harder tire in the nose and softer pair in the mains to prevent oversteering. (Note! Hitech Formula one tire selection here!!)

BR,
Jussi