Weight Reduction

[Inland RV Center, In]

Originally Posted by JimGolden

.

I will be doing a lot of boon docking so the tanks must stay. They will be larger than OEM actually. As such, the batteries must stay big too.

I will change out the univolt. I like the ideas of the solar cells.

I think my trailer's empty weight is stated at 5600lbs right now. I'd like to keep it to that or less, but with my enhancements. I will be changing out most of the appliances, if not all.

Cheers

Jim.

Reducing the weight is also a good goal.

But, unless you can appreciably reduce the weight, like 500 to 1000 pounds, you will not really gain anything.

Reduction of weight has a minimal effect on fuel mileage. A greater effect on fuel mileage is your driving habits, not the trailer weight.

Then we must consider the pay load effect. Leaving most of the things home that you usually carry will of course reduce the payload, but it will also decrease your fun factor.

Bottom line is that unless someone does extensive mountain climbing with their rig, small weight reductions have a "nil" effect.

Driving and/or towing habits, have a huge effect on mileage.

The costs to maximze weight reduction, could never be recouped by fuel savings.

Andy

[nickcrowhurst]

Originally Posted by Gen Disarray

I think it is the case that the force needed to move down the road is 1/2 the mass X the square of the velocity.

Force= mass X accelleration ,and thus it has dimensions ML(T^-2)

1/2 mass X square of velocity = kinetic energy , and it thus has dimensions
M(L^2)(T^-2)
Thus you can see that this cannot be a force.

This kinetic energy equals the amount of energy that must be dissipated by the braking system to bring the body to rest on a level plane.

The force needed to move down the road is equal to the air resistance of the body , plus the rolling resistance of the tires and transmission.

Force is that which causes a mass to accellerate.

Work done equals Force X (distance the point of application is moved by the force.)

Power is the rate of doing work.

Power required to overcome wind resistance is roughly proportional to the cube of the speed, rather than the square. That is, if you double the speed, there is 8 times the wind resistance. This takes 8 times the fuel consumption per unit of time. However, the body will only be travelling for half the time for a given journey, as it's speed is doubled, so it will only need 4 times the fuel.
One reference for this highly over-simplified analysis is at:
Drag (physics - Wikipedia, the free encyclopedia)

So you can see that Gen Dissary was correct.

Nick.

[AgZep]

And let's not forget that it's not just mass that might be a problem, but where the mass is. If somebody came up with a miraculous new process that resulted in cheap carbon fiber sheeting for floors, and tubes for frames, I wouldn't recommend using them without thinking long and hard about center of gravity. As you take away weight that you're carrying low down, you move your CG higher. Eventually, you'd end up with a light Airstream that towed worse than an SOB. Not good.

[bigeasy63]

Originally Posted by JimGolden

...I will be doing a lot of boon docking so the tanks must stay...

I would recomend poly or pex plumbing if you don't have it already. I don't know what your unit came with but my 63 Overlander had copper. All the piping, fittings, and patches probably weighed a lot. Luckily the P O had already switched it over and I had to just make a few mods to get it like I wanted it. It is fairly easy to work with and fairly cheap. Keep the tanks, but switch to plastic and you'll lose some there too. Just keep them empty, if you can, while travelling.

Most important.....Drink Lite Beer while you work on it!! That may help.

Bigeasy63 and I have been on a diet for two weeks. So far we've lost 14 days!

[PizzaChop]

Jim,

I think I'm in agreement with Roger and Andy on this one. With 70s era units, I think it is what you put in them, not what you remove which affects weight for the most part. There really isn't much room for appreciable weight savings when you get down to it. (Liquids and personal effects add up to much more than the the installed components.)

Have you considered how much weight you'll be adding by building a new beefier frame?

The original frame was designed to be lightweight and work in conjunction with the floor and shell. Assuming the integrity of all three components (and your axles/running gear are in good shape), the original frame should be more than sufficient to do the job and adds to the overall lightweight design of the trailer. Proper loading is obviously very important as well.

I gutted my '73 Sovereign and was very careful with what I put back in, but even completely empty (shell, floor, frame), I'll bet it weighed at least 4000 lbs. Maybe your TV can tell the difference between 4000 and 5000 lbs mine can't.

As for PEX vs copper, how much savings can that really amount to? If you're going to redo your plumbing anyway and you don't want to fool with sweating copper fittings, PEX may be the way to go, but I doubt you'll see much in the way of weight savings.

[soldiermedic]

My 56 caravanner was framed in 1x2 cedar and fronted with 1/8 inch walnut plywood. My coach weighs between 1500 and 1800 pounds and the cedar appears to have great strength holding up against weight.

Steve

[JimGolden]

Guys,

Don't get me wrong. My intent with the new frame was not to build some ten ton Titanic. Rather, the one I designed should add only about 180lbs to the coach's all up weight, yet be about four times stronger than the fishpole that's under it now.

Now let me throw this out there: When I sight down along the lower rub rail, aft of the back axles, I can see a definite downturn in the angle. It's not a lot; maybe a few degrees, but it's there. If I shine a laser down it, I can see the rub rail is lower at the back bumper than it is at the wheel well.

Is this normal?

I have been taking it all along that this means my frame has bent/sagged. Now if I'm wrong, I would just be happy as a clam! I'd really just love to be able to fix what I've got rather than go whole hog and redo everything.

I live in WV. There's not a stretch longer than two miles that is level here. A lot of where we'd like to go is mountainous. That being said, I'm pulling it with a 300+ hp truck that doesn't seem to mind the little Stream back there much at all. But just the same, I like efficiency. Weight is always the enemy.

And yes, sadly, I can see my wife's point. I'd lurked on this forum for only a short while 'til I bought mine. Had I known then what I know now....but the shell is still near perfect, the inside isn't bad, and I really like this model. I'd like to resurrect it.

PO let the pipes freeze and burst so all that would be redone. They are copper now; I was leaning toward PEX.

That being said, my grandpa sold his '67 Overlander to a guy that I was inquiring if he'd want to trade. The guy doesn't travel at all, just parked it by his workshop and hangs out in it. Something like that would be perfect for a 31 footer with sag and separation. But I don't know...I kinda like my '31.

Got my degree in aerospace engineering and am a big time EAA nut. Designing a bird right now in fact. I'm very familiar with monocoque construction. Again, I wasn't thinking a super gargantuan frame, just something a little deeper like they did later on. Well, actually a little deeper than that, but that doesn't cost you much weight.

I'm digressing here. I knew it wouldn't be easy to shed any pounds on this vintage. It's pretty light anyway. But maybe by new appliances I could at least offset the additional "dead weight" I'd be adding. Not to say I could get my wife to leave the kitchen sink behind

[rmpray]

I have thought about moving the bathroom into my tow vehicle...mainly because it is sometimes running with a boat instead of the airstream and...well...ya know between my wife and I sometimes the rest rooms just are not close enough together! No, not gonna strip out the bath...but it is an interesting thought...
I am an old airfreighter thus balance is still on my mind

[Boondocker]

Umm yeah... what Nick said

[Goin camping]

Why not just box the frame you have? save money, time and probably weight.

[nickcrowhurst]

Originally Posted by AgZep

As you take away weight that you're carrying low down, you move your CG higher. Eventually, you'd end up with a light Airstream that towed worse than an SOB. Not good.

What an excellent point! It's just the same with kayaks and yachts. Designers go to extraordinary expense and trouble to save a few ounces at the top of the mast (e.g titanium fittings) or a by specifying a balsa core deck, and then they add tons of lead or spent uranium to the keel. The aim is, of course, to stop the vessel from falling over. This must be a desirable aim for an Airstream. (i.e preventing roll-over accidents during sudden manoeuvres [I'm allowing myself the luxury of spelling that word the English way])
To this end, a huge benefit for an Airstream would be to remove the A/C unit from the roof, and put it close to the ground, using ducting to distribute the conditioned air. If, like me, you've struggled on the roof with lifting the heavy unit to replace the gasket, you will appreciate the point. That large mass is nearly 9 feet above the ground. During fish-tailing or sudden manoeuvres, it's the A/C that will be a dominant influence in rolling the trailer over.
Well said, AgZep.
Nick.

[Inland RV Center, In]

Originally Posted by JimGolden

Guys,

Don't get me wrong. My intent with the new frame was not to build some ten ton Titanic. Rather, the one I designed should add only about 180lbs to the coach's all up weight, yet be about four times stronger than the fishpole that's under it now.

Now let me throw this out there: When I sight down along the lower rub rail, aft of the back axles, I can see a definite downturn in the angle. It's not a lot; maybe a few degrees, but it's there. If I shine a laser down it, I can see the rub rail is lower at the back bumper than it is at the wheel well.

Is this normal?

I have been taking it all along that this means my frame has bent/sagged. Now if I'm wrong, I would just be happy as a clam! I'd really just love to be able to fix what I've got rather than go whole hog and redo everything.

A 31 foot Airstream trailer, has a normal "sag" between 1/2 inch to 1 inch.

That sag is not suggestive of anything other than, that's the way it is.

Andy

[JimGolden]

Andy,

Really? That may have just made my life a whole lot easier!

I'm going to pull some serious measurements this weekend!

thanks!!!

[Minnie's Mate]

Originally Posted by JimGolden

What ideas would you all have to reduce weight in our coaches? I'm looking at a total rebuild. I mean to increase the strength of the frame (actually replace it with a new stronger one), but I want to lower the overall weight of the coach.

What ideas do you all have for making the trailers lighter?

I don't think the custom feature in this unit will lead to weight reduction:
eBay Motors: 34 Foot Airstream Vacation Travel Trailer Camper RV (item 230128388028 end time May-20-07 13:45:56 PDT)

[malconium]

I wonder if a 70's vintage 31'r loses the sag at freeway cruising speads?

I have posted this thought in other places in the forums but it might bear repeating here. I have thought that if I really wanted to reduce the weight of my unit I would consider using fabric walls intead of more solid material. It also occurred to me that some parts of the storage, such as the wardrobe area, could be done using fabric cubby holes instead of solid shelves. I am not yet sure if that is what I will end up doing but I did go so far as to come up with an approach that I think would work. If anyone is interested feel free to ask for details. By the way going with this approach is not necessarily cheaper than more solid materials depending on the fabric of choice. To give the thought serious consideration mostly requires a change in mindset. As a culture we generally tend to think that solid means quality and that thinking is very deaply intrenched in some of our thinking.

Malcolm

[rmpray]

Hmmmm...we could add wings

[AgZep]

We took our trailer back to the factory for some warranty work in early summer 05. It's a long story, but we had a very early 28' CCD, and had encountered a strange shower drain situation that cropped up due to a deisgn flaw. They were really interested in figuring out what went wrong, and how to prevent it in future production. Anyway, the shower fix required quite a bit of the interior cabinetry to be removed and replaced.

I was shocked at the difference in weight between the 04 and 05 cabinets (the white ones with clear doors). The newer ones were much lighter, yet looked identical. It got me to thinking that a lot of weight in the newer units might come from the use of particle board, MDF and so forth. It would be hideously expensive, but replacing all of that with pine or something might save 100s of pounds. And since the cabinets are mounted high, that would be great for CG as well.

Hideously expensive though.

[CanoeStream]

Interesting report on the weight difference AgZep. I believe John "Pahaska" Irwin has come up with the name of lower density panel board that Airstream has used in cabinet manufacture -- supposed to be less dense than plywood. Not like I'm not going to tell you -- it didn't strike a bell and I don't remember what he called it. Glue resins make up a lot of the weight of chip board or MDF. Uggh!

[doorgunner]

Jim, fellow EAAer, I would suggest by Zeke Smith his fine paperback "Advanced Composite Techniques". Pretty informative and gives good practical information.I'm suggesting this so that you might think about a foam sandwich table or counter top surfaces.As previous post indicates MDF is very heavy. As you are a aero engineer I'm sure you will need a hands on guy to build it for you:+}. Actually if you get to sun n fun or oshkosh or a regional fly-in you owe it to yourself to sign up for the composites workshop. Usually a no cost affair that us tech counsellors help out with! DG

[Royce]

I am faced with a like problem. The Minuet was made with every weight reduction possible. Including foam core counter and floor, I had intended to remove much of the interior and replace it with custom cabinets. Now I will replace as needed but only without adding weight. One alternative is to use Alder, a decent hardwood with good strength to weight ratio. Redwood also has a good strength to weight ratio. I will be using Alder for the dinette table and return to foam core for the counter. The orginal dinette table is long gone.