Guys
I have done calculations on several different engine locations. The temporary
engine mount I made allows me to move the engine about five inches fwd and aft.
I'm using the tip of the spinner as my ref datum so each time I move the engine
fwd so moves the datum and I'm not sure if that is correct. My calculations as
I move the engine fwd are moving closer to the fwd RR CG limit, but only in
very small increments. I would have thought moving the engine five (5) fwd
would have had a large change in CG location. Should I be using the firewall as
a datum as it remains constant with respect to the RR CG range? All the
calculations have placed the flying CG within the RR CG range and the "plane"
goes over gross before getting to the safe aft CG limit.Looking for advise from
the smart ones!!!!!!!Pete Klapp
> Date: Thu, 31 Mar 2016 09:40:41 -0400
> From: n357cj at ptd.net
> To: pkengr at hotmail.com
> CC: ml at n56ml.com
> Subject: Re: KR> C.G location, Engine centerline
>
> Hi Pete,
> Just information for you... no advice.. Your Airframe is one of the longest
> if not thee longest constructed from the information that I have been
> collecting. by something like 1'-3". The next closest air frame is a flying
> plane and the dimensions that you sent me are proportional from in front of
> the main spar to the rear of it. 'having said that and a moment to digest it
> I would think that the engine mount would be very similar to length as what
> Mark and I had made. My gut reaction is that Maybe an extra inch might be
> appropriate. As far as the thought process of where to shoot for would be
> half fuel plus some fluff for all the stuff that you end up hauling around
> like flight bag, some tools, O2, headsets and the like. I have found that I
> most often fly with just barely under a half to full tank header and 3/4 to
> nothing in the wing tanks. Taking a trip being the exception when I start at
> full gross and fly until I have just the one hour reserve left. The end
> result that has been very satisfying to me is that I only trim for take off,
> landing and on a trip going from full gross to empty tanks. Even then the
> trimming is pretty minimal.
> As a side note my plane really does not like the rear CG even with out the
> 2" that we all agree is not safe. I really avoid that area completely and try
> to manage fuel movement from wings to header when I am at fully loaded
> condition.
> Joe Horton
>
>
> ----- Original Message -----
> From: "Pete Klapp via KRnet" <krnet at list.krnet.org>
> To: krnet at list.krnet.org
> Cc: "Pete Klapp" <pkengr at hotmail.com>
> Sent: Wednesday, March 30, 2016 11:04:24 PM
> Subject: Re: KR> C.G location, Engine centerline
>
> Mark
> I think I going to move the engine a little further fwd such that it
> calculates out that full fuel and pilot puts the cg right at the fwd end of
> the cg range. What about changing the location of the cg range, or should I
> stay with RR location?
> And you don't see a problem with lowering the centerline to 3 to 3.25" below
> the longerons? I will still have about 9.5" ground clearance.
> Pete
> > To: krnet at list.krnet.org
> > Date: Wed, 30 Mar 2016 21:42:07 -0500
> > Subject: Re: KR> C.G location, Engine centerline
> > From: krnet at list.krnet.org
> > CC: ML at N56ML.com
> >
> > Pete Klapp wrote:
> >
> > > I have done calculations with pilot plus 1/2 fuel and it falls at 2" into
> > > the RR cg range, and pilot & passenger plus 3/4 fuel and cg falls within
> > > 6" preferred cg range, the later coming in right at the aft edge of the
> > > preferred range. I'm thinking that I would like set the engine such that
> > > with me and 1/2 fuel that the cg falls right at the fwd cg limit.<
> >
> > N891JF is right at the forward limit with pilot and full fuel, and I can
> > tell you that I need a lot of UP trim to keep the nose up, but it's a small
> > trim tab and I still have plenty of travel left, so it does work. Forward
> > is certainly better than too far aft, and even though yours has a
> > nosewheel,
> > I wouldn't expect any problems being able to rotate the nose up on takeoff.
> > It's easy enough to move some things aft if needed later, and it's better
> > to
> > start with max stability, rather than min.
> >
> > > Next question: The horizontal engine centerline with the temporary engine
> > > mount is 2.5" below the top of the upper longerons. I'd like to drop the
> > > centerline a little more, 1/2 to 3/4", for better clearance for engine
> > > cowling and cooling plenum. Anyone see a problem with that.<
> >
> > My CG is 2.375" below the longerons on N56ML, and it's not a problem at all
> > in any respect with my plane.
> >
> > Mark Langford
> > ML at N56ML.com
> > website at http://www.N56ML.com
> >
> >
> > _______________________________________________
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