X-Mozilla-Keys:                                                                                 
Ken, I am not familar with the RV-3 cg range and gross weight, so can't
comment on that aspect.  However, I am flying an RV-6A (nose gear) with
the
13B and all radiators and coolers under the stock cowl.  My propeller
flange
is the same place as for the aircraft engine (approx 36 1/4" from
Firewall).

My engine is approx 8" from the firewall.  I use the Ross PSRU.  With
this
set up my aircraft's empty C.G is 0.1 inch foward of the limit listed in
Van's Specs (Van's staff says no problem with this).  The only
noticeable
effect is that when I have burned off most of my fuel and am trimmed for
landing (full flaps) I run out of nose up trim authority.  If I have at
least quarter fuel remaining I have sufficient nose up trim authority. 
The
elevator controls still have plenty of authority to lift the nose for
the
flair so there is no problem.  My empty weight is 1170 lbs or about 100
lbs
heavier than many RVs due to two batteries, mufflers, IFR panel, etc..

I don't fully understand the CG situation gettng worse in the RV 3 as
you
burn off the fuel load.  In my RV-6A, as I burn fuel in the wing tanks
(which are mostly behind the CG) the C.G moves toward the forward limit
not
the rear limit. But, if indeed the RV-3 C.G moves aft with fuel burn
then
that could be a potentially dangerous condition.  FWIW

Ed Anderson
RV-6A N494BW 65 hrs flight time with 13B

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