|
|
|
|
|
|
|
|
|
I don't want to add any additional confusion over the stabilizer issue but I thought I'd add a link that might be able to back up where your aerodynamic CG is on your stabs.
http://wingcgcalc.bruder.com.br/en_US/ Place your dimensions in there as precise as you can, select your desired CG (%MAC) and it will show graphically where your stab CG should be. I did this to back up my most recent F-100 that uses a similar pivot point arrangement. All flying stabs are great as long as they are precisely controlled, for that we need a balanced stab and also enough torque, right?!! So to back those premises up I ended up adding ballast to the stabs to balance them at 18 percent MAC. Flying wings are typically 15 to 20 percent MAC so I thought my "flying wing" of a stabilizer should be about in the middle. My pivot point is slightly ahead of the 18 percent CG - looks like the design of the model places the pivot point right at 12-15 percent MAC of the stab based on my calculations (that can create flutter issues with the pivot point being too far forward). A pivot point being too far back on the other hand, seems to me to be possibly setting up an aerodynamic control "snatch" hard-over control input, not easily returned to neutral due to aerodynamic forces above a certain speed, or servo strip/linkage/structure failure scenario above a certain loading. You have some mighty good servos going in, so the weakest link would be the linkage, servo mounts, and the pivot point hardware and mounts (if the problem even exists). Also think about what happens under heavy G loading - if the mass of the stab is forward of the pivot, the stab will tend to load up and increase into an additional control input that would add G loading further. That would be for positive and negative g loading, both cases. This could add to some subtle negative static/dynamic stability under load. OK, I'm getting too much into my old "aerodynamics" courses in college, I'll stop now. If it get's to the point of having to pull the pin out of the stabs to re-position, the way I see it you will not have to destroy the stabs. Since you added no formers you are in luck. Simply cut into the foam in the pattern of your stab pin and pull it. cut a new pattern in the proper place. Put ply formers on the bottom and top of the new stab pin pattern all the way to the glass surface, extend the formers beyond a little to act as a carry through spar and cap the stab also to help secure it all in as well as hold the pin in a central location. Add some carbon fiber mat, wet layup and vaccum bagged if you can on the center section of the top and bottom of the stab. Use a little bit of filler to glaze the transition. Yes it will be noticeable but it will be very nearly "un-noticeable" and will look planned/normal if you do it cleanly. Just my .02 |
|
|
|
|
|
Well in the interest of "doing it right" I better make sure the pivot point is in the right place, I wanted to see if I could carve out a new stab by hand..I am matching Nuts airfoil as best I can and think I am getting it pretty close.
I hate to not use Nuts hard work on hot wiring the stab but I would rather destroy it this way then in a flutter structual failier. I will plot the rod location and use formers this time. The new stab took me about 45 minuets to carv out so far..not a bad investment to get it right. |
|
|
||
|
|
Quote:
Absouletly beautiful!!! |
|
|
||
|
| Thread Tools | |
Similar Threads
|
||||
| Thread | Thread Starter | Forum | Replies | Last Post |
| Cool Micro F-5/T-38 Parkflyer Build | boingk | Pusher Prop Jet Models | 2 | Oct 17, 2011 09:58 PM |
| Discussion I knew it wouldn't be long!!!!!!! | Flightbox | Video Piloting (FPV/RPV) | 8 | Sep 29, 2011 05:17 PM |
| New Product 1/6 HETZER JAGDPANZER 38(t) Sd.Kfz. 138/2 r/c full metal | BIG TANKS PLANT | RC Tanks | 0 | Sep 28, 2011 02:38 PM |
| Sold Hangar Sale E-Flite P-38 rtf, GP Fokker, WM Miss America EP, Easyglider EZ T-38 | ScaleBrad | Aircraft - Electric - Airplanes (FS/W) | 15 | Jan 02, 2008 01:22 PM |