What Is the Best Method to Find the Neutral Point in Glider Models?

[darwinssj5]

hey,
i am working on a hand launched glider model..can anyone guide me how to find the neutral point, i used some simple online calculators but it is not considering some important variables..suggest me a reliable method guys...

 

[Ryoko]

You need to do wind tunnel testing or use numerical methods. You can also use a cookbook approach, which requires you to know the pitching moment of the wing and the amount of downwash on the stabilizer.

But the easiest method is to set the CG at 25% chord and move it aft a little at a time a give your model a toss. As the CG approaches the neutral point, the model will be increasingly reluctant to pitch down as it looses airspeed. When it passes the neutral point, it will try to pitch up as it slows.

For most conventional aircraft designs with straight wings, the neutral point will be in the 33%- 35% range.

 

[truffaldino]

hey,
i am working on a hand launched glider model..can anyone guide me how to find the neutral point, i used some simple online calculators but it is not considering some important variables..suggest me a reliable method guys...

Use XFLR5 program, it is free and has user-friendly interface, the neutral point will be found with few percent precision. You will also get drag polars and even stability analysys if you want.

I have designed and constructed several gliders using Xfoil and XFLR5.

You can also get preliminary rough estimate using tail volume and mean aerodynamic chord as in http://en.wikipedia.org/wiki/Longitudinal_static_stability

For more info on glider design join modelling science section of rc groups

http://www.rcgroups.com/modeling-science-136/

Truffaldino

 

[Aero_UoP]

hey,
i am working on a hand launched glider model..can anyone guide me how to find the neutral point, i used some simple online calculators but it is not considering some important variables..suggest me a reliable method guys...

Did you try to apply the theory that is inside every flight mechanics textbook?
I think that's the most reliable way... then comes the actual flight testing.