[NSRCA-discussion] Thrust Line Trimming

[Bob Pastorello]

I've just installed +1.4* upthrust, measured at the prop hub face, referenced to firewall.  The really INTERESTING thing is that now the spinner is dead center in the cowling (it was off slightly before) and the prop clears the cowling front lip equally all the way around.  I had to think through this awhile before I remembered - the cowling is "pre drilled", with the blind nuts premounted.  It would seem that it LOOKS right with the upthrust.

Will fly it Wednesday and report back, FWIW.
I left the elevator trim alone, so I will know on TAKEOFF if this was a good/not good thing to do... 

Bob Pastorello
www.rcaerobats.net
rcaerobob at cox.net
  ----- Original Message ----- 
  From: rcaerobob at cox.net 
  To: NSRCA Mailing List 
  Sent: Monday, May 22, 2006 2:38 PM
  Subject: Re: [NSRCA-discussion] Thrust Line Trimming


  Thanks, everyone. Consensus seems to be "try the thrust change".... and I'll do that. Good points and things to refresh memory about dynamic effects when changing throttle settings. 

  Happy Monday! 

  Bob
  ---- "george w. kennie" <geobet at gis.net> wrote:
  >IMO it sounds like the center line of the engine shaft is above the center line of the wing acting like down thrust. Additionally, as I recall, don't those Yaks have really long gear legs, ?......this would produce additional drag producing even more down thrust effect, then when you cut the power all of these force factors are effectively removed, which the elev setting has been overpowering at normal R.P.M. Without these factors in effect, the up elev now produces enough force to cause ballooning at the reduced setting. You will probably need to add a couple of degrees of up-thrust in the engine and this should not make it pitch to the belly, if anything I would expect it to exacerbate the canopy pitch requiring additional corrective mix, but like I say, just MO.
  >G.
  >
  >
  >----- Original Message -----
  >From: Bob Pastorello
  >To: NSRCA Mailing List
  >Sent: Monday, May 22, 2006 6:53 AM
  >Subject: [NSRCA-discussion] Thrust Line Trimming
  >
  >
  >Hello - I have a BME 30% Yak, (and had a TOC/Aviation Models Yak), and both pitch to the canopy when power is reduced in vertical climbs (also on level cruise power deceleration, too). Elsewhere, fly well, and doesn't exhibit bizarre incidence problems, and both needed UP elev. trim for level upright flight.
  >
  >ON the RCU threads on these two, owners report needing to carry up elev trim, also, but haven't gotten any insights on the engine thrust question.
  >
  >I have measured, and there is currently NO up or down thrust in the motor referenced to centerline.
  >
  >Could these planes actually need some UP thrust??
  >
  >Bob Pastorello
  >www.rcaerobats.net
  >rcaerobob at cox.net
  >
  >
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  --
  Bob Pastorello, El Reno, OK, USA
  rcaerobob at cox.net
  www.rcaerobats.net




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