Design > Stunt design

I. C. Engine vibrations.

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Chris Wilson:

--- Quote from: Brett Buck on April 10, 2021, 04:16:42 PM ---   Or, as a smaller-scale experiment - festoon it with VGs , trip strips, turbulators, and zizag strips.

     Brett

--- End quote ---
The issue I see there is that site specific application suits only a small range of use and having it applied generally with out regard of trip zones  maybe of greater benefit.
Coupled with ribs that resonate with I.C. engines would drastically increase the effective rlb size and take this discussion well outside of known research.
Ultimately I would like to see an equivalent product like Solarfilm made with a herringbone pattern on it and cover the entire model.
Such a film exists but not on a commercial level and comes from wind turbine research.
Chris.

Air Ministry .:
Could be the ' boundary layer ' effect would produce less drag but more / better ' LIFT ' , as the airflow wouldnt fall off / break away from the aifoil / flaps as easily. Maybe .

You might have to vary the surface to suit the temperature / atmospheric density . VD~ S?P

Ken Culbertson:

--- Quote from: Chris Wilson on April 10, 2021, 04:36:29 PM ---The issue I see there is that site specific application suits only a small range of use and having it applied generally with out regard of trip zones  maybe of greater benefit.
Coupled with ribs that resonate with I.C. engines would drastically increase the effective rlb size and take this discussion well outside of known research.
Ultimately I would like to see an equivalent product line Solarfilm made with a herringbone pattern on it and cover the entire model.
Such a film exists but not on a commercial level and comes from wind turbine research.
Chris.

--- End quote ---
You raise an interesting point.  None of this has anything to do with vibration but I have never had shiny clear coating and rubbing out make any plane fly better.  Score higher, yes but fly better?  It might be interesting to take a nearly finished electric and fly it with a fresh coat of unsanded filler, then sand it smooth and fly it again.

Ken

Dave Hull:
A bit more to add to the thought experiment:


(Ok, can't remember how to link one thread to another. Go look at "Energized Boundary Layer" in the engineering section--while I try to figure this out again.)

Jim Hoffman:
It’s been my experience that hunting (low frequency pitch limit cycle)  is more often seen in E powered stunters than IC.
There are two theories (IMHO) that may explain this……

1)   Higher inertia effects from the rotational mass of the motor, crankshaft, prop and spinner in E-power planes.
2)   Some boundary layer disturbance that may exist more in IC than E-power due to vibration.

I have been able to trim both IC and E-power stunters to a reasonably high level.

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