No its the anchor on the nose
Pirkka said:
As mentioned earlier, 400 lbs and few MPHs is lost so what is
the difference in case of RV(7) when it is light or not?
So if we really want to fly light plane, we should fly solo only because we
can't get plane 400 lbs lighter by removing unnecessary stuff... So while
building how much you can make difference to the weight really? Engine and
avionics make the most difference I think and it's up to the builder what to
put there but how about the rest? How much the painting does... average
weight of RV7s and deviation would be nice to know.
400 lbs? Top Speed?
I NEVER said light weight was a big factor in top speed. Check it out, its
written down. Doha!
I wrote: "I agree 100% but light keeps the
"fast feel" and not flying
like a stuffed pig."
I was agreeing weight does not affect top speed. That is a given.
So that means weight is not important? Of course not.
Weight does affect: stall, takeoff dist, landing dist and climb rate. Agree? No
argument. Heavy weight does means less payload. Heavy weight means less
gas. Acro in your RV may mean MIN fuel with two up or a solo only acro
plane. Weight is way more critical.
However you you missed the subtle point of
"fast feel". How the stick
feels in the hand, control pressures and response. Weight plays a big part. If
you are nose heavy and run out of trim on approach its a bummer. Or you
have a RV-7 with a light engine and can't fill the baggage compartment,
because you are tail heavy. If you have not flown a light RV it is hard for you
understand what I mean.
I agree its up to builder to make their RV the way they want. I have a
Hartzell, because of cost, performance, maintenance and reliability. So I will
accept the weight for a metal prop. However engine and prop do have the
biggest affect on weight.
Avionics is a minor player, not insignificant but I think heavy paint jobs and
internal priming can add the most. In some ways going from Vacuum to EFIS
and Electronic engine monitors, avionics has become lighter; however I am
aware of the two axis auto pilots and very full panels can add weight. Also
with the fancy panel people add two alternators and/or two batteries. I can't
believe some folks desire and large pocketbooks to stuff a panel full. Engine
choice or prop choice can add 30 or 40 lbs each. It takes a lot of avionics to
match 30-80 lbs.
W&B is the big factor on how the plane feels and what kind of
utility you have. Forget top speed for a moment.
Let's take a look shall we?
Just a scanning of aircraft empty weights that I compiled, lets just look at RV-6(A)'s:
Eng (legend)
[320 = 150/160HP (FI or Carb)]
[360 = 180HP (FI or Carb)]
[IO-360 = 200HP (FI)]
RV Wt. Eng Prop
-6 980 320 Aymar
-6 992 360 Wood
-6 1001 320 Sensenich
-6 1010 320 Hartzell
-6 1011 360 wood
-6 1017 360 Sensenich
-6 1020 320 Sensenich
-6 1023 320 Sensenich
-6 1029 320 Wood
-6 1029 360 Hartzell
-6 1032 360 Hartzell
-6 1034 320 Sensenich
-6 1036 360 Catto
-6 1041 360 Sensenich
-6 1046 320 Sensenich
-6 1050 320 Sensenich
-6 1062 320 Sensenich
-6 1063 360 Sensenich
-6 1067 360 Sterba
-6 1070 320 Wood
-6 1070 360 Hartzell
-6 1072 320 Aymar
-6 1090 360 Hartzell
-6 1110 360 Hartzell
-6 1130 320 Hartzell
-6 1139 360 Hartzell
-6 1147 360 Sensenich
-6 1244 IO-360 Hartzell
-6A 990 320 Sensenich
-6A 1020 320 Catto
-6A 1029 320 Wood
-6A 1040 360 Hartzell
-6A 1051 320 Sensenich
-6A 1060 IO-320 Wood
-6A 1064 360 Hartzell
-6A 1066 320 Sensenich
-6A 1079 320 Sensenich
-6A 1084 360 Hartzell
-6A 1094 360 Hartzell
-6A 1108 360 Hartzell
-6A 1120 320 Hartzell
-6A 1126 360 ?
-6A 1139 360 Hartzell
-6A 1165 360 Hartzell
-6A 1168 360 Hartzell
-6A 1170 360 Wood
-6A 1171 360 Hartzell
-6A 1179 360 Hartzell
-6A 1189 360 Hartzell
-6A 1195 IO-360 Hartzell
Analysis of all data above:
1078 Simple Avg
1065 Median
62 Std Dev
1244 Max
980 Min
Engine Break down:
Eng Avg MAX MIN
320 1037 1130 980
360 1092 1189 992
IO360 1220 1244 1195
You tell me the engine does not make a differnce? I say no Sir! (kidding)
Trust me, of all RV models (-4 thru -9) with O320/Wood prop's, the light
weight ones come in at less than 1000 lb. (typ 980 lbs, with the lightest I
have found was a RV-4 at 874 lbs)
The heaviest was the RV-6 quoted above at 1244 lbs. Using the 874 lb RV-4,
that is a 370 lb differnce! 
So there! (
)
In just the RV-6(A) data sample above
264 lbs difference from the max to min!
Guess what engine/prop was in the light one? 320/Aymar fixed
The engine/prop in the heavy one was? IO-360(200HP)/Hartzell
(Again I have no way of knowing how the planes where equipped other wise.)
Granted I did not include panel, paint, upholstery or what ever, but I have a
data base of over 120 planes and there is a clear trend. Big engine, big prop,
higher weight. Little engine, little prop, lower weight. That is why I said a RV-4
with a 160hp/wood prop was a delight to fly. It does matter. You have to fly
one to know what I am talking about.
There is no surprise because there is a 10 lb, 15 lb to 30 lb weight jump in
each engine HP, i..e, 150 hp, 160hp, 180hp and 200hp. It does not take
rocket science to understand also the oil cooler get bigger, fuel Injection has
more parts and so on.
Also not in the rocket science category, is metal props weigh more then
wood ones. Fixed ones weigh less than constant speed. When you add it up,
the above is typical and representative.
When you look at 20-30 lb engine weight and maybe 20-30 lb or more for
prop it is clearly the main factor. It would take a lot of avionics to make 20-
30 lbs. Again the RV-4 that weighs 874 lbs vs. a RV-6 at a hefty 1244 lbs
makes a difference in how it flys.
That is a lot of weight! I don't agree with avionics alone, upholstery alone or
paint alone being the cause of high empty weights. It is all of them. It is a
little of everything, but mostly engine and prop. I rest my case. So
there,
.
It only takes an extra 100 lbs on the nose to make a plane fly quite differnt. I
don't know how many RV's you have flown but I have owned a few and flown
many others. Light weight makes the plane fly much nicer. I am not alone in
that opinion and not sure what you are debating. If you ever fly a light 900 lb
RV-4 and than go fly an RV-8 with 1200 lb empty wt, you will know what I
mean.
This is no put down of the heavy weight RV-8, the extra 40 hp and
c/s prop makes a difference! However I am totally talking about feel, not
rate of climb or top speed. Hey I like my woman big, about a Deuce an-a
Quarter.
(well knock a C-note off that.)
Cheers George
PS:
Paint I hear estimates from 20 lbs to 30 lbs. I think it is more like 30 lbs.
That is just the exterior. Van's Aircraft saves weight on their factory planes
and does NOT prime before paint. People go hog wild on priming every interior
part with sealing primer verses a wash or translucent primer, will add 10 or
more lbs. Since most of it is on the aft fuselage it makes an aft CG problem
worse. I could see a worse case of 30-40lbs or more for all primer/paint.
If anything comes out of this discussion about weight, everything you add,
including primer adds weight. KEEP IT LIGHT, NOT
FOR SPEED but many other reasons.
