[pierre smith]

Mornin' all,
We weighed Brians -4 last night and it came in at 985 lbs...great. However, it is 1" forward of the forward CG limit empty and no fuel. With a 180 lb pilot and ten gallons of fuel, it is well within limits, about an inch behind the forward limit. Is this normal for a -4 with an Ed Sterba prop and the old, big clunky starter? He also has an Oddyssey battery on the firewall.

Thanks in advance,
Pierre

 

[Dean Pichon]

My -4 weighs 1050 lbs, empty. As I recall, the pilot must weigh at least 40 lbs to bring the CG within limits.

 

[Steve Sampson]

Good job on the weight!

Pierre with a glance at p 14-5 & 6 it looks very similar to the VANS numbers though I did not rerun the calc.

You might want to take a look here, http://www.rvproject.com/wab/. There are many -4 to compare with. Notice the average Cof G is at 65.23, and if I understand you correctly, yours is at 67.7. Glancing through the data there is one (British) with a number which looks plain wrong. If you knock that out I think the average and your number would be even closer.

QAt a quick glance you would appear to be pretty typical.

Good job on the weight. 21lbs less than average!

 

[Dayton Murdock]

Hi Pierre

This is the data for my RV4 which sounds very similar to your friend?s aircraft. My understanding is that RV4's are usually tail heavy. My A/C has a Catto prop and a clunky starter and my C/G is aft. Check your calculations if your friends A/C is equipped with a O360 that may account for the C/G forward

WEIGHT & BALANCE DATA

Make: Van?s Aircraft
Model: RV4 Serial # 4354 Registration # N359DM

Datum= 60 inches forward of wing leading edge. (L.E.)
Design C.G. Range = 15% to 29% of wing chord, or 8.7? to 16.8 inches from L.E., or 68.7 to 77.4 inches aft of Datum.
Wing L.E. = 60?aft of datum.
Main wheel, right = 60?aft of datum.
Main wheel, left = 60.3?aft of datum.
Tail Wheel = 237.5?aft of datum.

Aircraft weighed empty in level flight attitude.

Weight (lbs) Arm (ins) Moment (lbs. in)
Right Wheel 441 60 26460
Left Wheel 436 60.3 26290.8
Tail Wheel 56 237.5 13300
Total: 933 66050.8

CG=66050.8 / 933= Empty moment of aircraft 70.8? aft of datum

 

[bjustus]

Mine weights 971 lbs and empty CG is 70.66. This is with an O-320 and Catto prop, standard (heavy) starter, Odyssey battery between da feet.

 

[Low n Slow]

From my Aircraft Flight Manual;

 

[Mark Albery]

The wrong RV-4 on the list is my one - sorry. Actually it is right but the figures were based on a different datum of 50" forward of LE so you need to add 10" to all the datum positions.
Unfortunately, I can't see a way of editting it now it has been posted. Maybe Dan can delete it and I'll start again (G-MARX).

Back to the topic; pretty well everything you do to load an RV-4 will push the CG backwards, so having the empty outside the forward limit is not only pretty normal, it's actually quite desirable. I have more trouble staying inside the aft limit when 2-up with luggage.

 

[n82rb]

mine N82RB is 995lbs needs a 212lb pilot to get into cg

could be the o-360 constant speed and the battery in stock location.

the good side, i really cant make it go aft....