Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Jeremy, Jan 31, 2007.
I meant the soviet system on the video.
I believe that is Deskpilot's design. He is one of the members here on the forum.
One of the variations of (HBA forum member) Deskpilot. You'll find many of the variations in this thread:
You'll find this specific variation in this post:
Dear Gtex09, just lost my last attempt to post this into digital limbo. I have been a silent observer of your projects for several months. I have also been working on various models of the FMX-5 aircraft. I am encountering a sudden pitch-up problem immediately after take off. I have done a lot of playing with landing gear/ CG location to no avail. Can you offer any suggestions? I recently sold my Mooney 231 and hope to build a 1:1 version on my models in the near future. Recently purchase a 185hp rebuild Madza 13B with the Tracy Crooks planetary PSRU. I will try to attach photos, but that is when everything disappeared the last time. If I am not successful, will you e mail email@example.com and I will email the photos.Dave BarkerSpokane Valley, WA
I had that problem with one of my models and corrected the problem by giving it a tad more ground angle of attack. Don't try to haul it off the runway with a lot of up elevator. It'd probably levitate off the runway when you trim the model for level flight at half throttle if the ground angle of attack is sufficient.
8dave --your 'sudden pitch up' on take off may (only may) be due to the same problem that existed with the Zimmerman low AR aircraft models -those having a trailing edge elevator ie part of the wing hinged to form a flap, rather than the external tailplanes on the later full scale ones . The slipstream forms a sort of 'venturi' between the ground and the elevator undersurface which pitched them up . It could also be that your Cg is going overcentre as the angle of attack increases (this also happens with Rutan Ezes and requires easing off the backpressure to avoid overrotation ) --although you seem to have explored that avenue already --perhaps the drag centre also moves up (maybe as vortex flow develops ) or propeller normal forces are involved. Just a few possibilities.
Like Aircar stated, this is nose-up phenomenon is most likely due to the suction created by a venturi between ground and the trailing edge, which is in close proximity, when you use lots of elevator at take-off rotation. The possible remedies are:
1. Extending under carriage height, increasing trailing edge-to-ground distance.
2. Implement variable CG .. in other words, weight-shift pitch control, as is done on flexwing trikes.
3. Setting wing at higher AoA on landing gear, as delta suggested.
So longtime without giving some news...Sorry for that.
The project is still alive, please find some pictures attached.
I plan to make some engine static trials before end of the year.
I'll keep you posted.
Looking great Gtex!
Any other angle views please?
Please find attached some other views from cockpit, from engine, rearside without elevons, and also the central part without wings.
It is not yet finished, at prototype stage, with rough surfaces !
Coolies, thanks! :ban:
And one with cockpit open....
You can open the cockpit to enter by moving the top backwards.
I was wondering about that, probably not for older gentlemen and the way the market is going you would want to hope that it attracts a new breed of younger flyers I guess - and it might just do that.
I'm surprised you didn't run a tunnel the length of the cockpit for strength to offset the hatch opening (longitudinally where the control stick is).
Well, actually no need, the shape of central section, YZ cutwise, is strong enough to sustain wing efforts, as calculated (X is from front to rear, Y is from tip to tip, Z is front bottom to top axis)
That is awesome!. Something different, brave and smartly designed, really promising. I like how you've rigged the motorbike forks, that's a very interesting solution, really. Front shock absorber is from a bicycle, isn't it?.
I'm going to have to see more of the construction.
Yes... Main gear shock absorber from Ducati Monstro, but will have to modify spring strengthness to sustain load, and front shock absorber from small motorcycle. Hydraulic brakes on main, too. Cheap, mass produced, so easy to find. For the brakes, I also adapted the hand command cylinders to the rudder and direction pedals....
Yup, well done, Japanese dirtbikes are also a good place to start.
Is the lifting body project still alive? I've not seen any updates for sometime.
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