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ballast in rear baggage

W

woodsideraff

Well Known Member
I normally have to use full trim to land my 8A, and even then require considerable back stick pressure.

Today, I added 35 pounds in the rear baggage floor and the difference was remarkable! The plane handled much better.

Now, I did not build the airplane. It seems to me there should be tie down rings or other securing mechanism for the baggade compartment. I do not see any in the drawings. I certainly do not want my ballast rattling around in the compartment during turbulence or maneuvers.

Any suggestions on securing the extra weight?

Regards,

Rafael
RV8-A
 
Weigh the Airplane

It *sounds* like you arent sure there the weight and balance is on the airplane. You might want to do a proper weighing and then run the numbers. Or look closely at the numbers you have on a spreadsheet.

On my RV8 I'm a little on the nose heavy side of things and a case of oil in the rear when solo is really nice for landings. When I run various scenarios on W&B- Solo with low & full fuel, With a heavy/light pax, rear and front baggage and all that its pretty obvious how things are fitting in re the envelope.

Something you might also want to do (normally a phase 1 thing) is load it to various points of the envelope and at gross weight to get a better feel for how it handles/performs.

regards-
Tim
 
I installed bases for tie down rings on the baggage bay floor. The bases screw into nut plates on the angles on top of the floor ribs. Easy to do when building the aircraft. Still easy to do now, if the builder modified the baggage bay floor to make it removable. If the builder used the specified blind rivets to install the baggage bay floor, you could drill out the rivets, install the nut plates to secure the tie down rings, then reinstall the floor.
 
Rafael,
May I ask what the configuration of your RV8a is?
Engine? Prop? Battery location?

Thanks!
 
RV-8 (not sure about 8A - maybe the same) - a good figure is to try and get 80"+ CG loaded. If forward of that it is hard to land (8 again... 8A will be different)... With the 8A of course, all the nosewheel issues start, and again avoiding forward CG seems part of that.

1st flights on RV-8 I use ~30lbs of Ballast in the rear, and for solo aerobatics etc. secure 55lbs of Water Tank in the back.

Re securing it, requires a little planning when building to replace some rivets with nutplates and screws. Then use the screws to hold Adel Clamps down, and use these clamps to secure the baggage too... Just one idea.

Andy & Ellie Hill
RV-8 G-HILZ
 
CG details

Thanks for all the responses.

My 8A has a fixed pitch Sensenich, O360, and the battery is located on the firewall. Empty weight comes to 1,096 lb.

The allowable CG range is 78.7" to 86.8". The CG with full fuel and just myself (170 lb.) comes out to 79.5", which is close to the forward limit.

When I add 32 lb. on the aft baggage floor, the CG moves aft to 80.72", still quite forward but I'm now able to trim out the stick pressure during landing.

I'll try and figure out how to anchor the Adel clamps. Perhaps putting the weight on the aft baggage shelf would be better.

I'm curious about the water tank ballast idea.

Cheers,

Rafael
 
Baggage shelf

woodsideraff said:
Perhaps putting the weight on the aft baggage shelf would be better.

Rafael
Click to expand...

I made one of those Van's "practice kit" tool boxes, and added piano hinge segments to either end that attach to the aft baggage shelf. It weighs about 12 pounds when full of tools, and I can tell the difference when landing. Originally it was intended only as a traveling tool kit, but I usually just leave it in. It would be fairly easy to make a lead ballast plate that attaches in the same place.
 
Van's service letter

http://www.vansaircraft.com/pdf/Nose_gear_service_letter.pdf

The above service letter page 5, has a chart to calculate nose wheel
weight. Van's recomended max nose wheel weight is 375 lbs. I used
this chart to determine how much weight my -8A needed in the rear
baggage not to exceed the recomended nose wheel weight. In my case
it is 22 lbs. My oxy bottle, tool bag, survival kit and an extra headset
make up the 22 lbs. The great thing about the -8 is being able to balance
the airplane with front and aft baggage compartments. My -8A had an
empty weight of 1124 @ 77.15 CG
 
The 20-30 pounds of weight in the aft compartment seems like a bit of a makeshift fix to me. Why doesn't someone install a small compartment way back in the tail, like a 2" diameter tube that spans the fuselage, that you can install a like sized slug of lead into for solo flight. This lead ballast could be secure, but easily removable. In theory, you could save 15 pounds or so, but still get the solo CG where you want it. After all, many light helicopters carry this type of "conditional" ballast.

Some people would kill to save 15 pounds... seems almost a crime to carry that much dead weight around.
 
How about a tail weight?

Mark Navratil had a solution on his 8A. He fabricated a weight that screwed into the tail tiedown ring fitting when travelling solo. It appeared to weigh less than 10 lbs. but the moment way out there on the tail made it very effective. Maybe Mark can chime in.
 
I bought a wrecked 8a to use the parts, it was a 0-360, Hartzell CS, battery on the firewall type, 1064 lbs. It had a plate of 1" thick steel bolted to the tail on the shelf under the VS and in the middle of the HS.

I would think that would be the way to go, way more bang for your buck if you are gonna carry the extra weight around anyways.
 
move the battery

you are missing the obvious , move the battery to where it should have been to begin with. don't add extra weight.
 
Rotorway hilicopters have 2 battery positions. I think it is Forward for solo, aft battery position for carrying a passenger.
I built my battery in the back, but I suppose I could build a Fwd battery tray for nil additional weight when I have a passenger and lots of baggage?
I'm not flying yet, so I don't know. I just went for the aft battery 'because'.
 
RatMan said:
you are missing the obvious , move the battery to where it should have been to begin with. don't add extra weight.
Click to expand...

First thing I thought of too, but it seems that even with the empty CG "correct", it is still a little nose heavy when solo. It goes to reason then that placing the CG to make solo flight "correct", you would be tail heavy flying dual. The only fix for that is to add weight in the front baggage compartment, but because of the reduced moment, you'd need a lot more of it. Can anybody counter this train of thought?
 
Glider Ballast

What about removable ballast like is used in the glider community? We have to use it when flying with a passenger in the front seat that is too light (a child, your girlfriend (the wife does not need the ballast...:D), etc.) It is typically a steel plate attached with wing nuts the cabin floor or a bulkhead.

See attached link (scroll to the bottom under "ballast" for pics)

http://www.yorkglidingcentre.co.uk/Members/cfinotes.shtml

Scream
 
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Removable ballast

Scream said:
What about removable ballast like is used in the glider community? We have to use it when flying with a passenger in the front seat that is too light (a child, your girlfriend (the wife does not need the ballast...:D), etc.) It is typically a steel plate attached with wing nuts the cabin floor or a bulkhead.
Click to expand...

This is basically what I do, using some combination of my toolbox and a bag of lead shot (secured to the baggage floor). I seem to recall reading that Van puts 25# of water in the rear baggage compartment when solo in the -8. It would be easy to make a ballast plate that mounts on the rear baggage shelf.

My solo CG is a actually little farther forward than mentioned by Rafael (forward Odyssey battery and Hartzell prop), close to the forward limit. I see this as a feature rather than a "problem", because I can carry pretty much anyone who fits into the back seat. When solo, the airplane flies nicer with some weight in the rear baggage. However, wheel landings are easy even without the ballast. 3-pointers can also be done without ballast, but are trickier to do smoothly because of insufficient trim.

I strongly agree with the earlier comment that you should get an accurate empty weight and balance before doing anything else.
 
Toobuilder said:
First thing I thought of too, but it seems that even with the empty CG "correct", it is still a little nose heavy when solo. It goes to reason then that placing the CG to make solo flight "correct", you would be tail heavy flying dual. The only fix for that is to add weight in the front baggage compartment, but because of the reduced moment, you'd need a lot more of it. Can anybody counter this train of thought?
Click to expand...

The counter, more or less: You definitely should not need forward baggage weight if the battery is in the back and you have a heavy passenger (unless we are talking a Shamu sized behomoth here). I have an RV-8 with the battery in the back along with an ELT the size of a large brick. Empty weight is 1071. Old style gages. She has a Hartzell C/S on the nose and an O-360.

I am roughly 210. With a passenger of equal weight in the back she trims out very nicely with no added weight to the front baggage, regardless of fuel load, and is faily easy and stable to land. So I think your fear of having to add forward weight would be unfounded, especially if you have an 8A.

The best answer I think, albeit the most work, would be to yank that battery off the firewall.

Without the passenger in the back, my -8 is definitely nose heavy but well within the limits of available trim and CG. I can say that less trim changes are required with the guy in back, but once I get over the fact that I actually have to dial in a good bit of trim for solo on final, the weight on final comes off the stick nicely. But you definitely need a good deal more UP trim to keep her neutral. I can not imagine having a nose gear assembly AND a battery up front.

My suggestion would be to move that battery back during the down season if you have one. Me, I call it quits when I can't feel my toes...

I think you will be very pleased with the result.

I do not know if this is relevant...but I generally three point land the -8, which does not seem to be the consensus on the BBS...but after 500 hours in a Luscombe, full stall landings are kind of ingrained. Sometimes the mains hit a milisecond before the tail...and sometimes the tail hits before the mains..doh!...but I almost never wheel land it. At least not what would consider a wheel landing (level wing, tail up).
 
wera710 said:
The counter, more or less: You definitely should not need forward baggage weight if the battery is in the back and you have a heavy passenger (unless we are talking a Shamu sized behomoth here)...
Click to expand...

I'm interested in this because I'm now flying my buddy's newly aquired -8 which has 20# of shot in back. It will 3 point in this condition, but it takes full nose up trim and about 90% of elevator travel to do it.

Short of weighing the airplane and playing with the numbers (which will happen soon), the board discussion gives me the impression that the airplane can't be fully trimmed for solo and dual flight without ballast. If it is set up for nice handling when solo, the CG runs out the back side when dual. If the airplane can handle both conditions without ballast, I will certainly make that happen when we weigh it next time, but if Van uses balast, then I'm thinking the CG range is too narrow to satisfy both conditions.

So that brings us back to a design for the least amount of "easily removable" weight to satisfy the CG requirement.
 
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Ballast with passenger

Toobuilder said:
I'm interested in this because I'm now flying my buddy's newly aquired -8 which has 20# of shot in back. It will 3 point in this condition, but it takes full nose up trim and about 90% of elevator travel to do it.

Short of weighing the airplane and playing with the numbers (which will happen soon), the board discussion gives me the impression that the airplane can't be fully trimmed for solo and dual flight without ballast. If it is set up for nice handling when solo, the CG runs out the back side when dual. If the airplane can handle both conditions without ballast, I will certainly make that happen when we weigh it next time, but if Van uses balast, then I'm thinking the CG range is too narrow to satisfy both conditions.

So that brings us back to a design for the least amount of "easily removable" weight to satisfy the CG requirement.
Click to expand...

I ran the W&B with full fuel, my 170 lb, 50 lb of ballast in the rear floor, and a 200 lb passenger. I get a weight of 1768 lb with a CG of 85.6", still within the 86.8" allowable envelope and close to gross weight limit. Now, if you want to take baggage, then you must remove the ballast.

I guess there are some advantages to being 5'6" and 170 #:)

I've been looking all over for lead weights and thought of using anything from bar-bells to cement bricks. Right now I'm leaning towards bolting two 2" x 4" x 9" bricks to the back of the lower rear shelf. This should give me 50 lb and, by having it in two 25 lb units, manageable to remove. My floor is riveted, so I need to be creative on the attaching mechanism. I'm thinking that I can reach underneath from the rear and install two nut plates on the center floor ribs. I'm definitely not going to remove the riveted floor.

As usual, it's turning into a project.

Cheers,

Rafael
 
Chino Tom said:
That's what my 10 pound tool bag (includes spare quart of oil) is for.
Click to expand...

Understood, but two issues:

1) If we're discussing the tools only on their merit as ballast, then that 10# on the baggage floor could be moved all the way to the tail with a significant reduction in weight. Because of the shorter arm, the baggage compartment is a poor choice for ballast. Some of us often fly as light as possible (min fuel, no extra "stuff"), and 10 pounds is a lot to carry around "just because".

2) Is that 10# bag of tools going to stay in place during a 20-30G deceleration force in a crash, or is it going to center punch you in the back of the head? I'm thinking the rear seat back certainly isn't going to contain a bag of tools going 100 MPH. It would be a shame to have a quality 5 point harness save your bacon, only to be killed by flying tools.
 
woodsideraff said:
...Right now I'm leaning towards bolting two 2" x 4" x 9" bricks to the back of the lower rear shelf. This should give me 50 lb and, by having it in two 25 lb units, manageable to remove...
Click to expand...

Thanks for running the numbers...

Thinking out loud.... Anybody seen the Cessna "grab handles" on the aft fuselage of some models (Cardinal, for one)? These are simply 1 inch tubes that pop out of slightly larger tubes attached to the structure. For flight, they push in flush against the fuselage sides. How about a similar tube in the aft fuselage of the -8 that spans the fuselage sides. This "containment tube" would be about 2 inches or so in diameter x 8 inches long (or however wide the fuse is back there), and it would contain a removable slug of lead for solo flight. It could be spring loaded for easy removal, but contained by a simple hinged access door flush with the fuselage side. This slug of lead could be installed/removed in seconds, be completely secure, and provide the same "work" as any baggage ballast for significantly less weight.
 
Toobuilder said:
Understood, but two issues:

[... that 10# on the baggage floor could be moved all the way to the tail with a significant reduction in weight. Because of the shorter arm, the baggage compartment is a poor choice for ballast....]
Click to expand...

I would be very happy to put the weight at the rear of the airplane. However, this means placing inside the fuselage --- not easily removable--- or hanging it outside.

I have thought of moulding or machining a piece of lead with an aerodynamic shape blending into the fuselage and strapping it on the tail by the tie-down attachment. It could be painted to match, red in my case. I don't think there would be any structural problems, since this place is strong enough to be used as a tie-down point. The configuration should be able to handle the dynamic load.

The more I think about this, the better it sounds....

Rafael
 
Toobuilder said:
the board discussion gives me the impression that the airplane can't be fully trimmed for solo and dual flight without ballast.
Click to expand...

Michael,

I think "can't" is a bit strong. My experience is that solo with no ballast the airplane trims up fine on final, it just runs a bit short of trim if flared to 3-point attitude. Not a problem at all with a wheel landing.
 
Indeed, "can't" is a little strong... It's certainly safe in this condition and it does wheel on nicely, but it feels a bit heavy in pitch. It's much "funner" with lighter stick pressure. Just looking for the ultimate compromise I guess.
 
Toobuilder said:
Thanks for running the numbers...

Thinking out loud.... Anybody seen the Cessna "grab handles" on the aft fuselage of some models (Cardinal, for one)? These are simply 1 inch tubes that pop out of slightly larger tubes attached to the structure. For flight, they push in flush against the fuselage sides. How about a similar tube in the aft fuselage of the -8 that spans the fuselage sides. This "containment tube" would be about 2 inches or so in diameter x 8 inches long (or however wide the fuse is back there), and it would contain a removable slug of lead for solo flight. It could be spring loaded for easy removal, but contained by a simple hinged access door flush with the fuselage side. This slug of lead could be installed/removed in seconds, be completely secure, and provide the same "work" as any baggage ballast for significantly less weight.
Click to expand...

I think this would be an excellent idea. I have installed many of these stc'd grab handles in Cessna's and I think your onto something. The further back you have weight, the less weight you need due to the arm. If you could figure out a weight distribution system as easy as what you lay out. STC it and sell it under many make and models. Think of how easy you could not only trim a RV8 or any model but any certified aircraft also. You could even adjust the diameter of the tube to incorporate bigger aircraft.

Great Idea. This is why I love this forum. So many people not only think outside the box, they don't even know what the box is. :D
 
<<How about a similar tube in the aft fuselage of the -8 that spans the fuselage sides. This "containment tube" would be about 2 inches or so in diameter x 8 inches long (or however wide the fuse is back there), and it would contain a removable slug of lead for solo flight>>

Michael, that is an outstanding idea. I just put it on the project list for my -8.

Pat, can you relate or draw the structural attachment details for the Cessna socket tube? Are they flanged to the skin, attached to a bulkhead, or both? Give me some thinking info and I'll kick out a preliminary design drawing for discussion.

BTW, I'd suggest using 2" 0.049 or 0.058 for the socket tube and pouring the lead into a 1.875" diameter steel tube. That would make the slug durable and clean to handle.
 
weight distribution

you certanly need less weight the farther back you move it, it has an impact on the weight distribution however. This shouldn't be an issue for "normal flying" but it could increase the tendency towards a more horizontal (flatter) pitch angle in a spin.

Mario (very unlikely that any extra ballast in the back of my 7 is needed)
 
Toobuilder said:
Is that 10# bag of tools going to stay in place during a 20-30G deceleration force in a crash, or is it going to center punch you in the back of the head? I'm thinking the rear seat back certainly isn't going to contain a bag of tools going 100 MPH. It would be a shame to have a quality 5 point harness save your bacon, only to be killed by flying tools.
Click to expand...

The rear seat back, if unrestrained, certainly wouldn't stop a ballast weight or tool bag from flying forward and out. So, whenever I fly solo I strap together my rear seat 5 point harness and pull the shoulder straps tight; holds the seat back in place nicely, nothing's coming outta there.
 
Toobuilder said:
THow about a similar tube in the aft fuselage of the -8 that spans the fuselage sides. This "containment tube" would be about 2 inches or so in diameter x 8 inches long (or however wide the fuse is back there), and it would contain a removable slug of lead for solo flight. It could be spring loaded for easy removal, but contained by a simple hinged access door flush with the fuselage side. This slug of lead could be installed/removed in seconds, be completely secure, and provide the same "work" as any baggage ballast for significantly less weight.
Click to expand...

This sounds like about the easiest way to add temporary ballast that I've heard. My quick calculation is that the slug would be around 10-12 pounds, and would move CG back about 1". You would have to put about 20 pounds on the aft baggage shelf to do the same thing, so the tail tube saves about 8-10 pounds.

Another idea would be to seal a compartment between two bulkheads under the HS, to hold water ballast. It would need some sort of plumbing to add water, and a drain plug or valve. This would be hard to do on a finished airplane, but maybe feasible during construction?
 
Holes in the aft fuselage

I would be very hesitant to cut holes in the aft fuselage skin, not only from an aesthetic point of view, but also from structural strength considerations. It might be OK to do so. I just don?t know.

Rafael
 
You only need the hole on one side, and of course it would be properly analyzed for stress. As for the aesthetic part, it would have a flush door sealing it off and be mostly hidden under the stab. Most would never even notice it.
 
Alan Carroll said:
Another idea would be to seal a compartment between two bulkheads under the HS, to hold water ballast. It would need some sort of plumbing to add water, and a drain plug or valve. This would be hard to do on a finished airplane, but maybe feasible during construction?
Click to expand...

Water makes a good ballast in some cases because it is easy to get rid of quickly, but it is sometimes difficult to find when you need it. Also, with a sealed structural compartment, you better hope it doesn't freeze!
 
jbDC9 said:
The rear seat back, if unrestrained, certainly wouldn't stop a ballast weight or tool bag from flying forward and out. So, whenever I fly solo I strap together my rear seat 5 point harness and pull the shoulder straps tight; holds the seat back in place nicely, nothing's coming outta there.
Click to expand...

The seat back is just glass isn't it? I'm thinking that a bag of tools would punch right on through in some situations. I keep thinking of those slow motion films showing chickens launched at aircraft windshields. I could be wrong...
 
DanH said:
...Michael, that is an outstanding idea. I just put it on the project list for my -8...
Click to expand...

Well thanks... since EVERYBODY is further along in their RV project than me, I'm just happy to help the community.

I'm thinking there also needs to be a good place to stow the ballast on or near the C/G when it is not required in the aft position. It should be equally secure and easily removable as the rear position...
 
Toobuilder said:
The seat back is just glass isn't it? I'm thinking that a bag of tools would punch right on through in some situations. I keep thinking of those slow motion films showing chickens launched at aircraft windshields. I could be wrong...
Click to expand...

The rear seat back is aluminum. The upper 15% is fiberglass. I too
fasten the rear seat harness/belts when flying solo. And my tool bag is
strapped down. My -8a doesn't need ballast to fly solo and be within
the CG limits. It does need ballast to stay within Van's recommended
nose wheel weight limit. Simple is best for me, and my tool bag fits
that parameter. The tools go to the front baggage when I fly with
a passanger.
 
Toobuilder said:
The seat back is just glass isn't it? I'm thinking that a bag of tools would punch right on through in some situations. I keep thinking of those slow motion films showing chickens launched at aircraft windshields. I could be wrong...
Click to expand...

Didn't they make a mistake at first and use frozen chickens? ;)
 
Chino Tom said:
The rear seat back is aluminum. The upper 15% is fiberglass. I too
fasten the rear seat harness/belts when flying solo. And my tool bag is
strapped down. My -8a doesn't need ballast to fly solo and be within
the CG limits. It does need ballast to stay within Van's recommended
nose wheel weight limit. Simple is best for me, and my tool bag fits
that parameter. The tools go to the front baggage when I fly with
a passanger.
Click to expand...

That's the beauty of building an Experimental - lots of options. Your mission profile is different than mine (I rarely carry tools or excess weight of any kind - including fuel). I'd also like to point out that I'm not trying to ?win? a discussion; just putting info out there for the community to digest (feel free to accept, reject, or expand). In the spirit of discussion, I avoid a toolbox/bag behind my back because I don?t like the weight and I have a pretty good idea of the energy that ?loose? objects have in a crash. I?m reminded of a project we worked on recently where we were going to install a Garmin 196 in the cockpit of a current military aircraft (we?re the OEM). This was to be a mount that allowed the unit to be removed easily, such as a RAM mount. Anyway, by the time the stress guys did the calculations for containing the little GPS in a crash situation, the mount was going to be built like the Brooklyn Bridge. Now I don?t know how all RV-8 baggage tie downs are built, but the airplane in my hangar has two small aluminum angles pop riveted to the floor. With two pop rivets for each angle, I doubt the structure could contain a box of tissues with hard application of the brakes, let alone a toolbag in a crash. So that leaves it up to the seatback to contain the whole mess. I?ll give you that I don?t know if the seatback (restrained by the 5 point harness) would contain a bag of tools. I think it would take an actual crash situation to find out for sure? Let?s hope that never happens.
 
Aux fuel

IIRC some C-172's had a small tank in the tail with an aux xfr pump. Use fuel in back for CG, then pump it fwd as wing tanks burn off, maintaining a "constant" CG. MUCH more complex, but might be right for someone?
 
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