What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

100 Pounds Heavy

GrayHawk

GrayHawk

Well Known Member
I'm working on a new W&B for an RV-6A I bought already flying. If I believe the original W&B, the plane has gained 100 pounds since it first flew. Some of this weight is easily accounted for in going from a wood Sterba prop with a fiberglass spinner, to a wood Warneke prop, to finally a metal Sensenich (79") with a metal spinner and 4" extension. However, the remainder of the added weight seems to be distributed so as to move the CG 1-2" aft.

There's not much back there new except paint. In fact, I've removed every bit of aft weight that I can easily remove. I am thinking possibly the plane was repainted without removing the old paint. Wound anyone care to venture a guess as to the weight added in an average paint job? Searching the forums did not find a good number.
 
scale calibrated?

Switching from one type of scales to another will make a big difference. Some folks use bathroom scales joined together...others may use an old beam scales. The only way to be sure?... if you know the first weight check and your check was accomplished using calibrated scales. Point #2. Any time I have done aircraft weighing on commerical or corporate aircraft, we upjacked and downjacked 3 times and then take the avg. Point #3. Was the aircraft level the first and second time? Many things may have happened that you might not know of the first time. We are human and we make errors all the time. No big deal, keep up the good work and keep learning your aircraft.
 
Average weight

According to Dan Checkoway's excellent Weight and Balance data base;
http://www.rvproject.com/wab/
the average RV6 weighs 1078lb and the lightest 1017lb and the heaviest 1139lb.

How does this compare with the claimed weight from the first weighing and the weight you determined?
Pete.
 
Could be, a little

GrayHawk said:
added weight seems to be distributed so as to move the CG 1-2" aft. There's not much back there new except paint.
Click to expand...
Interesting theory it was painted twice. The most weight I have heard of was about 30 lbs and yes, paint tends to move CG aft, but I don't know about 1-2". Paint does add but 100 lbs, no.

I think there are two things. A little there, a little here and a lot with errors in the old weight and balance measurements and calcs, or errors with the new W&B calcs. Its never fun to find out you gained weight. :eek:
 
Last edited:
You did have your canopy closed while weighing, didn't you? I know this is elementary, but sometimes simple things are overlooked.
 
Yukon said:
Have you considered that the original W/B was not accurate?
Click to expand...
Yes, I am keeping that in mind as shown by "If I believe the original W&B" in the original post.
 
Mel said:
You did have your canopy closed while weighing, didn't you? I know this is elementary, but sometimes simple things are overlooked.
Click to expand...
Thanks Mel
Yes, I am weighing in flight configuration.... Not sure about the original as I was not there. I am about to weight again this next week. I'll get as close to flight configuration as possible.
 
fodrv7 said:
the average RV6 weighs 1078lb and the lightest 1017lb and the heaviest 1139lb.

How does this compare with the claimed weight from the first weighing and the weight you determined?
Pete.
Click to expand...
Original empty weight: 1063 (Done by original owner)
Current empty weight: 1164

Original CG: 70.70"
Current CG: 72.34"

But I plan to redo weight this week with calibrated scales, and will jack & unjack several times to get an average.
 
gmcjetpilot said:
Interesting theory it was painted twice. The most weight I have heard of was about 30 lbs and yes, paint tends to move CG aft, but I don't know about 1-2". Paint does add but 100 lbs, no.

I think the its two things. A little there, a little here and a lot with errors in the old weight and balance measurements and calcs, or errors with the new W&B calcs. Its never fun to find out you gained weight. :eek:
Click to expand...
I think what I will find out is that the weight increase shown on the nose wheel is due mainly to the change from Sterba wood prop with harmonic dampener to metal Sensenich with metal spinner and extension. Then of the weight increase that's left, some will have disappeared due to weight reduction efforts I've taken since I first weighted. The remaining increase will be on the order of added paint and added equipment, bondo, and misc.

I'll post the new numbers when I get them and appreciate all of the feedback & suggestions.
 
SCALES TO WEIGH PLANE ON

Gray Hawk, contact your state Motor Vehicle Enforcement unit and see what is would cost for them to weight the plane on their certified scales. These are the guys who weigh 18 wheelers. I'm in Tennessee and the cost is really low. This is not to say it will be the same in your state. I would then take the old W&B, the W&b you have done and the 3rd and compare the three. Question was the orginial W&B done without fuel and also was yours done the same? Just my 2 cents!
 
RICHARD HUTSON said:
Question was the orginial W&B done without fuel and also was yours done the same? Just my 2 cents!
Click to expand...
Don't know for sure about the original but it is labeled "Empty" weight and then in later calculations fuel is added in. My first W&B was without fuel but with oil and the one coming up will be without fuel but with oil.
 
dan said:
GrayHawk,

I might have missed it in your posts or profile, but where are you located? If it's anywhere near SoCal, I'd be happy to weigh your airplane on Intercomp digital scales... http://www.weighmyplane.com
Click to expand...
Colorado & Texas. I'll be less secretive and add it to my profile. I plan to use the local EAA chapter scales, unless they end up being bathroom scales (Haven't checked them out yet).
 
Last edited:
Residual fuel also

Some additional weight might be hiding in the wings in some residual fuel, even if you have drained this, there is always *some* left.
Doesn't solve the aft CG but maybe some to the total weight.

Have they placed an ELT behind the baggage area?

Pat Garboden
Ozark, MO
 
gorbak said:
Have they placed an ELT behind the baggage area?

Pat Garboden
Ozark, MO
Click to expand...
I believe the ELT is in the original position, left side of baggage compartment, behind pilots seat. I've actually removed some things aft of the baggage compartment (2 antennas, one diplexer); so it will be interesing to see what effect that has.

The equipment I believe was added after the original W&B:
1. NavAid wing leveler, servo under passengers seat area.
2. Duckworks landing/taxi lights.
3. Wingtip lights with strobe power supply per wing at wing tips.
4. Several small gauges at instrument panel.
5. And then of course, the prop change.
 
Good thread

Sounds like the mystery is unraveling. Prop, extra equip, original W&B not quite right or accurate, Canopy (good one Mel).

Just a note, Van wrote and article last year on this very thing. They go to air shows and a new owner of a second hand RV mentions W&B. Van's knows normal weight and CG for given equip, and they know when its wrong.

From the article Van finds that planes do gain weight over time (like their pilot/owners) and W&B documents are often done poorly and subject to errors from scales, math, new equip not added and subtle things like canopy position and fluids.

Interesting thread and good on you having the curiosity to investigate and determine the likely reasons. Many second hand RV's just get sold and the old W&B's are way out, but the new owner never investigate or question it. This has safety implications as Van's article mentions.

PS fuel is usually empty but that can be usable fuel, with unusable fuel as part of the empty weight.
 
Last edited:
I just saw a commercial that said that a typical mattress will double in weight over it's lifetime due to DUSTMITES!! :eek:

Clearly this doesn't apply to RV's, but it's pretty dang gross.
 
One other thought

When I weighed my plane, I didn't have fuel or oil in it. I also had not completed the fairings, so I just taped the pieces that would make up the fairings in their general location. My hope is that the completed fairing with paint will come out close.
When your plane was first weighed, was it painted, were the fairings completed? The answer to these question could help justify the weight change/shift.

Also there could be a small weight effect of oil and dirt on or inside the fuse.

My fairings are completed now, but won't paint them until the weather warms a bit. After I am finished I will drain the fuel and re-weigh the plane. I will report the results to the forum.

Kent
 
He only weighed it once

GrayHawk said:
I'm working on a new W&B for an RV-6A I bought already flying. If I believe the original W&B, the plane has gained 100 pounds since it first flew. Some of this weight is easily accounted for in going from a wood Sterba prop with a fiberglass spinner, to a wood Warneke prop, to finally a metal Sensenich (79") with a metal spinner and 4" extension. However, the remainder of the added weight seems to be distributed so as to move the CG 1-2" aft.

There's not much back there new except paint. In fact, I've removed every bit of aft weight that I can easily remove. I am thinking possibly the plane was repainted without removing the old paint. Wound anyone care to venture a guess as to the weight added in an average paint job? Searching the forums did not find a good number.
Click to expand...

He probably never bothered to weigh the plane again after paint and fairings.

My plane was 1080 when it was certified for the first flight. After paint and fairings it was 1120.

So there's 40 of your 100. Painted twice? Another 30. Metal prop and spinner? Another 20? Add upholstery and possibly some fuel estimate error (if you didn't drain it) and you've easily accounted for 100 pounds. Oh, by the way, if the plane doesn't have a drain under the luggage compartment, you might need to check for water, too. I had one annual with my old Cherokee where I cleared a stopped-up drain hole under the rear seats and a quart of accumulated condensation drained out.

I bet not one in ten weighs again after paint and fairings. And they'd be shocked to see how far over gross and behind the limit they are when they're loaded up for Osh.
 
kentb said:
When I weighed my plane, I didn't have fuel or oil in it. I also had not completed the fairings, so I just taped the pieces that would make up the fairings in their general location. My hope is that the completed fairing with paint will come out close.
When your plane was first weighed, was it painted, were the fairings completed? The answer to these question could help justify the weight change/shift.

Also there could be a small weight effect of oil and dirt on or inside the fuse.

My fairings are completed now, but won't paint them until the weather warms a bit. After I am finished I will drain the fuel and re-weigh the plane. I will report the results to the forum.

Kent
Click to expand...
I'm not sure about the condition of the plane at first weighing. I'll try to find out from the builder.

I agree on the debri inside the fuselage and have been cleaning "house".
 
jonbakerok said:
He probably never bothered to weigh the plane again after paint and fairings.

My plane was 1080 when it was certified for the first flight. After paint and fairings it was 1120.

So there's 40 of your 100. Painted twice? Another 30. Metal prop and spinner? Another 20? Add upholstery and possibly some fuel estimate error (if you didn't drain it) and you've easily accounted for 100 pounds. Oh, by the way, if the plane doesn't have a drain under the luggage compartment, you might need to check for water, too. I had one annual with my old Cherokee where I cleared a stopped-up drain hole under the rear seats and a quart of accumulated condensation drained out.

I bet not one in ten weighs again after paint and fairings. And they'd be shocked to see how far over gross and behind the limit they are when they're loaded up for Osh.
Click to expand...
No water under the floorboards, just dust & other debri. I also removed a couple of clumps of mud attached by agressive insects. So a couple of ozs there.

Working through the numbers, the worst case situation would be on landing with minimum fuel, heavy pilot, heavy passenger, and some baggage. In that case you are near rear CG limit or outside limit and need to exercise caution on the landing; probably were over gross on take off and should have stayed on the ground.
 
Last edited:
One more thought...

I know I have said that before.

The inside of the wheel pants may have some dirt/muck in them.

Kent
 
I know I'm chiming in late and someone may have already mentioned this. But if you weigh one wheel at a time like I did, having the plane sitting exactly in the same attitude each time you moved the the scale from wheel to wheel made a *tremendous* difference! Fortunately, my next door hangar neighbor had a nice precision level and some previous experience at weighing planes and helped me.
 
I know it's unlikely, but over years I'll bet a lot of dirt, water, bug poop, etc. could accumulate in the rudder bottom.
 
szicree said:
I know it's unlikely, but over years I'll bet a lot of dirt, water, bug poop, etc. could accumulate in the rudder bottom.
Click to expand...
Yuk! That's one I haven't checked. Might be worth checking.
 
Low Pass said:
I know I'm chiming in late and someone may have already mentioned this. But if you weigh one wheel at a time like I did, having the plane sitting exactly in the same attitude each time you moved the the scale from wheel to wheel made a *tremendous* difference! Fortunately, my next door hangar neighbor had a nice precision level and some previous experience at weighing planes and helped me.
Click to expand...
I plan to use regular aircraft scales, 3 separate scales for the 3 wheels, with the plane leveled in flight attitude, then jack & unjack each point taking an average as suggested.
 
You must log in or register to reply here.
Back
Top