What's new
Van's Air Force

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

weight and balance - RV-7A

lostpilot28

lostpilot28

Well Known Member
Did my weight and balance today and was happy with the empty weight of the airplane (1043 lbs). Without wheel pants/fairings or paint, I'm a bit far aft for an empty CG. It calculated out to 80.91.

I'm so close to flying, I really do not intend to move anything forward (ELT, strobe P/S, etc), and was wondering what others think about this CG. I would feel better if it were an inch forward.

I've got a Catto 3-blade prop and a light instrument panel. I'm guessing that all the aeropoxy filler I used on the HS tips and rudder added a little bit to the weight! :rolleyes:

I know I've got the option of adding a weighted prop spacer, but not sure what else I could do to bring the CG forward. After paint and the rest of my interior (baggage side panels, etc) it'll most likely move back a little bit. My W&B only goes out of the envelope under heavily loaded baggage conditions with low fuel. Should I worry about this? Any advice is much appreciated, as always!
 
Here they are...

Scales were aircraft scales (can't remember the brand), but certified & calibrated within the past year.

I should've posted these in the original message:

Weight Arm
Right Main 393 94.375
Left Main 395 94.5
Nose 255 39.125


This brings up another quick question, actually. I find it odd that my Arms are slightly different than what Van's example is. Being a prepunched kit I would think they'd all be virtually the same.

Then again, being off by less than a 1/2-inch probably isn't changing anything much...
 
lostpilot28 said:
Did my weight and balance today and was happy with the empty weight of the airplane (1043 lbs). Without wheel pants/fairings or paint, I'm a bit far aft for an empty CG. It calculated out to 80.91.

I'm so close to flying, I really do not intend to move anything forward (ELT, strobe P/S, etc), and was wondering what others think about this CG. I would feel better if it were an inch forward.

I've got a Catto 3-blade prop and a light instrument panel. I'm guessing that all the aeropoxy filler I used on the HS tips and rudder added a little bit to the weight! :rolleyes:

I know I've got the option of adding a weighted prop spacer, but not sure what else I could do to bring the CG forward. After paint and the rest of my interior (baggage side panels, etc) it'll most likely move back a little bit. My W&B only goes out of the envelope under heavily loaded baggage conditions with low fuel. Should I worry about this? Any advice is much appreciated, as always!
Click to expand...
We have the same plane, and prop. I anticipated this problem and put 5/8" spools between my engine mount and firewall. I will be weighing mine next week. Hopefully the spacers put my W&B in the sweet spot.
 
Hi Sonny,

....amazing! Your weight is just 2 lbs lighter than ours was and the wheel weights are so close. I also have the Catto and Jenny and I have flown it with 80 lbs in back to Florida on a 2hour trip. It became a little rear biased on CG but not a problem. The flare on landing didn't take much effort on the elevator...it was definitely lighter but again, no big deal as long as you realize this.

Regards,
 
Hi Pierre,
Do you have a 7A also, or were you referring to your 6A? In my current situation, there is no way to ever load my airplane any more forward than the middle of the CG envelope. I'd like it to be in the middle of the envelope when it's moderately loaded. I suppose my desire for this is that I get the full range of utility out of my plane.

Does your CG sit more to the aft than front?
 
I forgot...

what engine you have. Is it a 360? If so did you use a 360 Finish Kit?

I am also thinking of using a lighter weight prop (than a CS Hartzell). If your answers to the above are affirmative then I will order a 320 Finish kit even though using a 360 engine. The 320 spaces the engine forward and by my estimation will move the CG about 2/3" forward.

I gues you should have used some boat anchor avionics instead of your beautiful MGL panel (tongue firmly in cheek)

Larry
 
Last edited:
CG

Sonny, You issue is your prop. It's too light. The 7A is nose light and was designed for a CS or Sensenich prop with a 360 on the nose.

My first prop was a Sterba. It was light, just you you state. I added a Landol 12lb CG ring on the Ring Gear. It helped. I then swapped the Sterba for a Sensenich prop.
The issue was solved. If you want to keep the prop then add the Landol Ring, it just bolts on. You may also install the larger battery on the firewall.
Lastly move your ELT to behind the Pilot's seat and re-weight the airplane.
The Landol ring is found in the back of Sport Aviation magazine.

Tad Sargent
7A 500 hours
 
Solved this problem with the weighted prop spacer on my -7A. Did the trick and was the most bang for the buck with regards to CG. I got mine from Sabre (Saber?) Manufacturing. Believe they are in Texas. Thought about adding a 2nd Odyssey battery but the weight gain/cg movement payoff wasn't that big.
 
lostpilot28 said:
Did my weight and balance today and was happy with the empty weight of the airplane (1043 lbs). Without wheel pants/fairings or paint, I'm a bit far aft for an empty CG. It calculated out to 80.91.

I'm so close to flying, I really do not intend to move anything forward (ELT, strobe P/S, etc), and was wondering what others think about this CG. I would feel better if it were an inch forward.

I've got a Catto 3-blade prop and a light instrument panel. I'm guessing that all the aeropoxy filler I used on the HS tips and rudder added a little bit to the weight! :rolleyes:

I know I've got the option of adding a weighted prop spacer, but not sure what else I could do to bring the CG forward. After paint and the rest of my interior (baggage side panels, etc) it'll most likely move back a little bit. My W&B only goes out of the envelope under heavily loaded baggage conditions with low fuel. Should I worry about this? Any advice is much appreciated, as always!
Click to expand...

I have a similiar setup except with the forward induction and weighed in at 1034 and 81.0. I've since replaced my Superior ryton sump with the aluminum. This added 4 lbs. I'm completed painting this week and will do another W&B next week. I'll report my changes.

To compensate, on cross country trips near gross, I restrict baggage to 75#. I definately feel the aft cg on landing with lower fuel.

If you'd like to play with my CG scenario, you can check it out on Dan Checkoway's W&B site.
Here's the link to my 7A wo fairings & paint.
http://www.rvproject.com/wab/wab.jsp?id=163
 
Scott Will said:
Solved this problem with the weighted prop spacer on my -7A. Did the trick and was the most bang for the buck with regards to CG. I got mine from Sabre (Saber?) Manufacturing. Believe they are in Texas. Thought about adding a 2nd Odyssey battery but the weight gain/cg movement payoff wasn't that big.
Click to expand...

Hi Scott, I was looking at Sabre's website, but couldn't find a weighted spacer. How much was it? I also downloaded someone's very slick Excel spreadsheet W&B calculator (with graph) of VAF. If I added 20 lbs to the nosewheel it didn't change my CG much...it went from 80.91 down to 80.13. That helps, but it's not much. Then again, I don't know if shifting the weight like that would lighten the weight on the main gear.

What was your CG before and after the weight?
 
DanLandry said:
I have a similiar setup except with the forward induction and weighed in at 1034 and 81.0. I've since replaced my Superior ryton sump with the aluminum. This added 4 lbs. I'm completed painting this week and will do another W&B next week. I'll report my changes.

To compensate, on cross country trips near gross, I restrict baggage to 75#. I definately feel the aft cg on landing with lower fuel.

If you'd like to play with my CG scenario, you can check it out on Dan Checkoway's W&B site.
Here's the link to my 7A wo fairings & paint.
http://www.rvproject.com/wab/wab.jsp?id=163
Click to expand...

Hi Dan,
Very close setup, indeed! I was worried about painting and adding the Classic Aero side panels & carpet in the baggage area. There's a lot of surface area aft of CG, and paint can be relatively heavy. I'm thinking I may have to spring for the weighted prop spacer. I saw your W&B on Dan's site a few days ago. Have you ever flown it outside the aft CG envelope?
 
Tip up or Sllider?

If it is a slider, did you weight it with the canopy closed? I bet more than a few sliders have been on the scales without closing the canopy. FWIW.
Regards,
Bernie
Strongsville, Ohio
RV7A , N914E,
1,117 lbs, O360, carb, Sensenich prop,with full paint, Flightline interior AND smoke system.
530 hrs, 1,147 landings, 1,243 rolls, 107 gallons of smoke oil, since 9/11/05
L.G.I.T.W.
 
Last edited:
ArmyDad said:
If it is a slider, did you weight it with the canopy closed? I bet more than a few sliders have been on the scales without closing the canopy. FWIW.
Regards,
Bernie
Strongsville, Ohio
RV7A , N914E,
1,117 lbs, O360, carb, Sensenich prop,with full paint, Flightline interior AND smoke system.
530 hrs, 1,147 landings, 1,243 rolls, 107 gallons of smoke oil, since 9/11/05
L.G.I.T.W.
Click to expand...

Hi Bernie, Yes, the slider was closed! ;)
 
Similar equipped RV-7 data point

Here is a data point for you. My unpainted 7 without wheel, leg, intersection fairings came in at 1034 lbs and 80.01?. With paint (yellow takes a lot of coats so it is a heavy paint job) and fairings I came in at 1055lbs and 80.48?.

I was surprised by two things. One, I thought the paint would add more weight. Two, I was surprised by the amount of CG shift since the fairings are forward of the CG.

The real downside of my rear CG IMHO is I can only do acro with guys weighing less than 180lbs. The heavy loaded, low gas scenario has been a non-issue for me. Good luck.

TMX O-360, Catto three blade with Sabre crush plate.
 
Heavy Engine and Prop

Can anybody comment on a 7A tipup with heavy engine (counterweighted 200 HP IO-360), and also a heavy Hartzell CS prop? Is it NECESSARY to have the heavy prop if you already have the heavy engine for balance reasons, i.e. to keep the CG within range under all loading conditions? If using the 200RV prop instead of the heavy Hartzell (18 Lbs ? lighter), would I have any problems with CG in any particular loading condition?

It's difficult to have a clue about my CG starting point and whether I ought to be considering moving things around this early in the game. I'm still trying to decide on the WW group buy, and W&B is a big factor...
 
I just weighted mine -7A with CS Hartzell and IO-360, painted with all the goodies came to 1168 lb and the CG being at 80.29. The thing that I can not understand my left main is about 17lb heavier the right and just wondering/concern about the first flight and how it will behave. Any thoughts?

Thanks in advance
Mehrdad
 
I have a IO-360-M1b with a 74" two blade prop. Based on the data sheet, it looks like mine is not bad, more forward then comparable planes.

Thanks
Mehrdad
 
FWIW

My -7A came in light(w/o paint) at about 1050 and just under 79". I got a used O-360 with a Sterba prop and harmonic dampener. I think it's a Landoll but not sure(there are no markings on it) and to help keep the weight forward I opted for the included stock starter rather than the lightweight Sky-Tec(added another 6-8 lbs in the FWF area). Don't know if that would help.
 
You must log in or register to reply here.
Back
Top