Timeline for How to locate the coordinates of the Center of Gravity of an airfoil?
Current License: CC BY-SA 3.0
18 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 24, 2017 at 10:31 | vote | accept | george | ||
| Aug 23, 2017 at 12:40 | vote | accept | george | ||
| Aug 23, 2017 at 12:41 | |||||
| Aug 23, 2017 at 2:32 | answer | added | Marius | timeline score: 1 | |
| Aug 21, 2017 at 20:51 | comment | added | george | @Marius Legend! | |
| Aug 21, 2017 at 20:45 | comment | added | Marius | @George Gotcha. Alright--I think I have some resources for you. And some papers...someone else in my graduate lab was working on the next step of this idea for a large-scale rotor. Hopefully have it written up today or tomorrow. | |
| Aug 21, 2017 at 20:40 | comment | added | george | @Marius Basically, i will not give much emphasis on the material of the blade since i am trying to develop a propeller for small RC UAVs. Also, the purpose is to find out weather it is feasible to develop this kind of "self adjusting" pitch propeller tailored only due to aerodynamic loads. That's why my idea was to pivot the blade in an offset from the a.c. Counter weights are going to be used to achieve the dynamic stability, but i have no idea what calculations needed yet. | |
| Aug 21, 2017 at 20:31 | comment | added | Marius | @George Ooo...designs using composites are another can of worms that's a little beyond my expertise. I have some reference texts that I can note, though. By internal structure I was also referring to how you were going to balance and tailor the blade structure to achieve dynamic stability. I have a reference text that may come in handy for that too, but estimating the strength of composite structures...that's tricky. I'll see what I can find. By the way -- it would be useful to update your question with some of this detail, and then rephrase your question as looking for a method. | |
| Aug 21, 2017 at 20:18 | comment | added | george | @Marius Also, i am going to use a High Strength Carbon Fiber /Epoxy Composite for the blade. Is that what you mean by interior structure?(I have already got the properties of the material) | |
| Aug 21, 2017 at 20:16 | comment | added | george | @Marius yes, actually i need to predict the static and dynamic balance/stability of the propeller by equating the pitching moments due to aerodynamic loads with pitching moments caused by the inertial effects. Have you any idea on witch theoretical background shall i consider? I am assuming angular momentum would be useful but i am not sure. | |
| Aug 21, 2017 at 20:04 | comment | added | Marius | @george -- Exactly. "m" can be a density to make your life a little easier too. You can use a program like XFLR5 to add points to the E326 profile too for a little more accuracy/control if you decide to have a non-homogenous interior. What does your interior structure look like? I'm assuming you're adding weights, etc. (as I note, I'll codify this into an answer soon along with some geometry formulas for calculating moments of inertia, etc.)? | |
| Aug 21, 2017 at 19:57 | comment | added | george | @Marius i am working on an Eppler airfoil E326 with reflexed profile; data can be found here: airfoiltools.com/airfoil/details?airfoil=e326-il. So by integration you mean this formula : $$ R_{cm}=(∑_i(m_i*r_i) /∑_im_i ) $$ where R and r_i are the position vectors x,y,z right? | |
| Aug 21, 2017 at 19:16 | comment | added | Marius | Oh ok. I just had to do something similar for computing aeroelastic effects on a wing. The only way I saw how to do it was to make a little calculator that would compute the cross-sectional properties for me. Essentially, it's the same of @kevin's comment -- just integrate to find the cross-sectional properties given some desired skin thickness. I don't know if there is a "best" way to do what you want rather than just creating "a tool that does what you want" based on the design of your cross sections. What do your cross sections look like, and what airfoil(s) are you using? | |
| Aug 21, 2017 at 19:05 | comment | added | george | @Marius Yes, actually i am designing a propeller blade with the pitch axis placed in an offset distance from the aerodynamic centre or CG. So i am trying to calculate the pitching moments due to mass/Inertial effects, and i need parallel axis (Steiner's) to make the calculations which are made with the CG location as a reference. | |
| Aug 21, 2017 at 15:42 | comment | added | Marius | Perhaps a question for you would be this -- are you trying to determine the CG location analytically and experimentally? It sounds like you're trying to design the prop on paper and do some design studies...so my second question is this: what are you trying to do? | |
| Aug 21, 2017 at 7:07 | history | edited | DeltaLima♦ | CC BY-SA 3.0 |
edited title
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| Aug 18, 2017 at 8:37 | comment | added | xxavier | You can get reasonably accurate results by cutting a piece of plywood with the form of the profile, suspending it at three different points, and then mark the prolongation of the suspension cord on the profile. The intersection point of the lines (or the center of the small triangle, if one is thus generated) marks the c.g. | |
| Aug 17, 2017 at 20:20 | comment | added | kevin | The same way you locate the center of gravity of any object. If it is very simple you do summation. If it is a curve defined by a formula you do integration. If it is anything else you use numerical methods. | |
| Aug 17, 2017 at 19:54 | history | asked | george | CC BY-SA 3.0 |