By definition the lift is divided equally between the flying surfaces. In
practice it is difficult to achieve this type of balance because the
leading surface sees air differently than the aft surface, due to effects
like downwash, tip vortices, and prop wash. The effective angle of attack
of the two surfaces also significantly impacts the distribution of lift.
Generally speaking unless the pitching moments, C.G. and separation of the
surfaces are carefully considered, tandems are difficult to trim and can be
less efficient than traditionally designed models with the same surface
area.
I would say overall, this makes tandems a poor choice for SO models.
The equation for the coefficient of lift for the stab that I use is wing
area in square inches * (coefficient of wing lift * ( C.G. position
relative the rear wing post + .75 * mean wing chord in inches) +
coefficient of drag of the wing * vertical height of the wing in inches -
0.1 * % chamber of the wing / 3* the mean wing chord in inches - (stab area
in square inches * (stab drag coefficient (vertical separation of the wing
and stab - height of the wing in inches) + 0.1 * % of the stab camber / 3 *
the mean stab chord in inches)) / (stab area in square inches * (the stab
moment - 0.75 * mean wing chord in inches - C.G. position relative the rear
wing post))
This equation is intended for practical estimation and neglects to account
for several of the aerodynamic effects mentioned above.
Best wishes,
Nick
On Tue, May 19, 2015 at 1:05 PM, manu32d_at_gmail.com [Indoor_Construction] <
Indoor_Construction_at_yahoogroups.com> wrote:
>
>
> Someone knows what occurs with tandem models , ie , with the same shape and size in the wings and stabilizer. Is there a specific formula for this type of models ?, How the contribution of the rear wing lift is considered and how this affects the duration of the flight ?
> Thankyou
>
>
>
>
>
Received on Tue May 19 2015 - 12:02:26 CEST
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:48 CET