Design > Stunt design
Stunt Plane Parameter Calculator
Howard Rush:
Here's a spreadsheet to calculate some stuff that's easy to calculate, but kinda rule-of-thumby. It introduces the Buck coefficient, invented today by me, based on Brett's advice that absolute tail length is more useful than tail length relative to wing chord. I just embellished that by dividing by circle radius, making it look more scholarly.
Dave Rigotti:
Thanks Howard!
Chuck_Smith:
Thanks Howard,
Pretty darned cool. What would be even cooler would be to have all of us enter our data and have the results plotted graphically. Or even better, take the winning ships from the last 50 years and see how they compare and changed over time or overlayed on the data
I suspect that with the advent of electric power and the fixed CG we'll the tail volume increasing somewhat noticeably, right Igor ;D? Or at least we'd see a divergence in tail volume of electric vs IC power choice.
But I should add that from a maneuverability standpoint and not static stability, the tail volume can be somewhat (OK, very!) misleading. We really care about the moment generated vs. inertia tensor of the airplane. That's where maximizing comes into play. An infinitely long tail would have an infinite pitching moment upon an infinitesimal elevator deflection, right? But then again it would be infinitely massive so it would never move! Conversely for the infinitely short case. All other things equal, a light model turns faster than a heavy one. Keep the aerodynamic forces constant but at the same time increase the inertia tensor - things slow down.
Or how you distribute the mass. Two planes may be identical in planform and mass, but one has the battery on the CG and the other in the nose. Which one turns faster?
Peace,
Chuck
Howard Rush:
Yep. Graphics would be cool, and a lot of stuff is left out that could have been included without requiring any more effort by the user. For example, I should have estimated wing and tail lift curve slopes.
Igor Burger:
--- Quote from: Chuck_Smith on December 27, 2020, 08:04:13 AM ---I suspect that with the advent of electric power and the fixed CG we'll the tail volume increasing somewhat noticeably, right Igor ;D? Or at least we'd see a divergence in tail volume of electric vs IC power choice.
--- End quote ---
1/ I do not know if "the longer the better" probably not and 2/ I do not know if electric is different than IC - probably also not
However I think there is some optimum (here I do not mean to compare model with 2m long tail flying 1,5m radiuses, I mean real numbers) ... and that optimum I mean between position of CG means static stability and "maneuverability". Means there can be some optimum of tail length and horizontal tail area, elevator area etc (not needs to be only tail volume in meaning volume X arm length) which will allow to move CG so that the static stability will be highest. It will need to seat at such simulator/calculator and try some configurations ... whe know what to hunt for, we have calculator, whe know how to do it ... but .... but for me answer is still ... no time no time n~
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