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Old 10-13-2017, 09:11 AM   #1
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Total weight and distribution

As a newbie, I have been pouring over the previous threads on AS restorations. I have also seen numerous Internet posts on designs implemented for total gut jobs. What surprises me is that I have not seen anyone discussing the weight implications for these designs.

I think too many people are focusing on how it looks and not how their designs are affecting the stability of the AS. I see people using 2x4s for interior walls. That seems crazy to me! You use up too much space and add too much weight. Steel 2x4s don't add as much weight, but still take up too much space.
After just having gutted my '76 31' Sovereign, I can see how AS saved on weight using plastic and flimsy steel parts. Using 3/4" plywood constructions to replace the original construction...well you can see how weight will add up quickly.

I understand some of these people never intend to tow their AS and park it somewhere to use as an extra bedroom.

Does anyone know of a good reference or list of guidelines for weight considerations for the design of a remodel? Not just the total weight, but how it is distributed within? How it might affect the tongue weight or side-to-side stability?
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Old 10-13-2017, 09:43 AM   #2
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The best guideline I can give is to purchase (or rent) a set of trailer scales, one to go under each tire, and one under the tongue jack. Place adhesive labels on each scale listing what the maximum weight for that point is. Put the scales in place before you start, and leave them there. Then as you proceed, check the scales every day, and if any scale shows more than it should, plan on undoing what you did that day and starting over the next day with things in a different position.

Or better, your target value for each tire and the tongue jack should be no more than 90% of the maximum. That leaves you a 10% buffer all around to account for "live" (moveable) loads such as groceries, clothing, etc.

When using "weigh as you go" methods, place heavy things where they will go and check the weight before fastening them in place.

Also, don't forget to check weights with stabilizer jacks up, not down, and with all tanks full.

"Weigh as you go" is a bit more free-form than drawing detailed diagrams and crunching numbers, so it's not the way an engineer would normally do things. But it does allow for a bit more spontaneity and creativity than planning everything in advance.
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Old 10-18-2017, 08:33 PM   #3
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I guess what you are saying is there is no “practical” solution to the problem? Trailer scales would cost over $2K for a one-time use. Renting them would probably cost more, since it could not be done in a weekend.
I find it hard to believe no one has ever done a methodical study of this before (as many restorations that have been done).
You cannot use a modular-move-it-around method. There are wiring and plumbing considerations.
I guess I will just have to economize in all constructions and balance the load intuitively.
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Old 10-18-2017, 08:46 PM   #4
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What is your goal here?

Are you thinking you will re-engineer a "new" interior that will be road worthy on an "old" chassis, with old technology suspension, wheels, brakes, etc? There is certainly some obvious concern to be safe on the road, especially if your planning on towing regularly and use for camping, etc. I totally get the labor of love thing, and modification to a floor plan that you feel to be more useable, but taking it on the road, does require some engineering considerations with the older models when talking additional weight on the original suspension system. Others on the forum can help with input, if you specify your goals more clearly. Great project if you have the time and money. Good luck!
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Old 10-18-2017, 09:11 PM   #5
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Total weight and distribution

Weight distribution is simple, keep the back light and heavy stuff close to the trailer axles.

Airstream claims the dry curb weight of my 72 to be 4,900 lbs. my modified trailer weighs about 7,500 pounds, loaded for use and wet. I guesstimate I added about 1,500 lbs of real weight.

Once I got smart about it I started using 3/4” plywood cut into 1 1/2” strips for structural members and cabinet frames. I used 1/4” birch plywood extensively.

I have a virtually Identical 75 that is still rock stock. It and my modified pull about the same on the ball, “ok” to about 60 mph. My 72 pulls like it is on rails with my Hensley.

I’d post pictures, but my account is restricted.
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Old 10-18-2017, 09:22 PM   #6
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If you use 3/4” ply for bulkheads, etc, your trailer will be a brick.

Frame your bulkheads like a hollow door using 1/4” ply as a face, and 3/4” x 1 1/2” strips between as the edges. They are light and strong.
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Old 10-18-2017, 09:26 PM   #7
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Total weight and distribution

Quote:
Originally Posted by glrtex View Post
I guess what you are saying is there is no “practical” solution to the problem? Trailer scales would cost over $2K for a one-time use. Renting them would probably cost more, since it could not be done in a weekend.

I find it hard to believe no one has ever done a methodical study of this before (as many restorations that have been done).

You cannot use a modular-move-it-around method. There are wiring and plumbing considerations.

I guess I will just have to economize in all constructions and balance the load intuitively.


Apply common sense. Trial and error will come into play, but the trailer, and its redo’s will be yours.

I redid my bathroom once and half of my kitchen twice. The other half of the kitchen will be the next project for redo.

This project will incorporate some other upgrades on my battery and inverter locations.
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Old 10-18-2017, 09:36 PM   #8
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My last upgrade. The refrigerator and the pantry were previously reversed. https://photos.app.goo.gl/wKpYOLTqyVONUyY73

The bulkhead in the foreground is made with the sandwich method I mentioned above.
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Old 10-18-2017, 10:20 PM   #9
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Was... https://photos.app.goo.gl/1F90MSrZAmPHPny43
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Old 10-19-2017, 06:59 PM   #10
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I see this sort of dinette arrangement on many remodel designs. This seems like a lot more weight on the tongue than a gaucho sofa/bed?
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Old 10-19-2017, 07:07 PM   #11
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It could be heavy, and then is built in a weight conscious manner it might not be too heavy.
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Old 10-19-2017, 07:46 PM   #12
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So - weight calculation is just that. Develop a layout and the general configuration of the elements and components you will install. Establish the weight of the materials on a square ft basis. Establish the quantity of the material you will use. Then establish the location of each element. The distance from the tongue ball and axles allows you to calculate the weight that bears on those components. It will align with the ratio of how far each item is from the support component. Of course all the weight behind the axles will bear on the axles. A computer spread sheet is quite helpful in performing the calculations.

As you start building you can weigh the elements and compare that to your initial calculation. You may need to adjust the design if weights shift much from your plan.

Weight saving - look at how the trailer was originally constructed and use that as a reference. As suggested, build bulkheads like a hollow core door. Hidden elements can have holes in them to remove weight. The Airstream history books talk about the aircraft materials that were used to save weight on the early coaches. You could probably fabricate angles and channels from sheet aluminum with a sheet metal brake from one of the Harbor Freight tool supply distributors. High school and adult ed shops may be a source as well. There is also the option to make your own with bar stock and hinges.

Note - screws are slow speed mills and work lose over time. So clamps and glue may well be your friend. Through bolts are an alternate to screws and are a good way to make a strong connection if you use locking or jam nuts. The folks who have done these projects can help, so read their posts.

Plan until you have a solution that works on all levels. The process will develop into the design spiral. As you define one item, it will change another. As you adjust that item to work, another will be affected. You keep working the layout and furniture configuration until it all works on paper.

If you can't visualize a 2d drawing, you may have to build models or even full size samples. Cardboard can be your friend. It's easy to draw small and hard to live with too small. Don't fool yourself. Key elements might well be built in particle board. It's cheap and the sample can be strong enough to try out to verify it's the right configuration.

Good luck with your project. Pat
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Old 10-20-2017, 02:07 PM   #13
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As above. On my overlander project I used excel for x axis and just tried to balance street and curb. On my current project I’m going an extra step as I moved the axles 24” aft; I bought a tongue scale and I’ll use trailer scale weight, tongue weight and excel to balance x and y axis. I’ve studied up more this time so will aim for the golden 12% tongue weight with a low cog too

I’ll definitely build structural mock ups of furniture rather than just cardboard too

There was also an analogy of a barbell being twisted that I read in this forum which stuck with me reminding me that just because it balances out to a decent tongue weight doesn’t mean it’ll work well
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