Pete in Northiam Posted July 25, 2022 Share Posted July 25, 2022 Having seen several F3-RES gliders hit wing flutter on the bungee and watched as tailplane flutter led to the sad demise of an F5-RES under power on Saturday, I thought it was about time I got past my own limited understanding and read more about the causes and cures. I found the link below a useful summary of the physics of causes and fixes. If you want to skip the maths, look at the pictures then jump to page 9 for a summary of the problem and possible fixes. I've posted this to the Facebook group too as I know not everyone is on BARCS. https://www.kimerius.com/app/download/5784128815/Aerodynamic+Flutter.pdf Link to comment Share on other sites More sharing options...
cirrusRC Posted July 25, 2022 Share Posted July 25, 2022 Not sure I understand any of that My take on flutter - speed and lack of stiffness in surfaces and linkages is your enemy. Our quest of low wing loading kinda works against us, as typically means more fragile. Launching - the steeper the climb the less speed and reduced risk of flutter. I see people launching to the horizon on bungee which accelerates the model. Release aiming as close to vertical as possible. The best solution I think is 2 models. 1 lightweight one for light conditions, one heavier/stronger one for windier conditions. But clearly I don't listen to my own musing Link to comment Share on other sites More sharing options...
Martin O Posted July 26, 2022 Share Posted July 26, 2022 17 hours ago, cirrusRC said: Not sure I understand any of that My take on flutter - speed and lack of stiffness in surfaces and linkages is your enemy. Our quest of low wing loading kinda works against us, as typically means more fragile. Launching - the steeper the climb the less speed and reduced risk of flutter. I see people launching to the horizon on bungee which accelerates the model. Release aiming as close to vertical as possible. The best solution I think is 2 models. 1 lightweight one for light conditions, one heavier/stronger one for windier conditions. But clearly I don't listen to my own musing Launch to the horizon - That's me! . But so far no flutter on the Magic 2. I sort of agree on the two model thing but my next project will be an attempt to have a design that will cope with all conditions. We shall see Link to comment Share on other sites More sharing options...
mikef Posted July 26, 2022 Share Posted July 26, 2022 Plastic film covering adds little torsional stiffness. Most Fx-RES designs use tubular carbon spars or wooden D-boxes to counter this stiffness problem within the rules. It may be worth remembering that doped tissue is stiffer in torsion than a plastic heat-shrink film of the same weight. As often happens, a 'simple looking' model formula turns out to reveal problems that 'more modern' models have already solved. 1 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now