For anyone who doesn't already know this, to calculate the volume of a space in gallons (for water/holding tanks), when measuring in inches, do this:
(LxWxH)/231 = volume in gallons
So based on that, without making a ton of frame modifications, I can accomodate approximately 54 gallons for fresh water over the axles, with space for approx a 30 gal gray tank, water pump and pipes/dump valve.
Consider adding the fresh water tank to the space just ahead of the front axle. The weight of the water adds some to the tongue weight, and makes the trailer tow very nicely. This was evident in the TradeWind I used to tow, and is why I chose the same location for the fresh tank for the Overlander. Another plus is that you won'thave to remove the axles to service your fresh water tank.
Uwe, I have a mid-bath. In order to accomodate the drain for the kitchen, shower, bathroom sink and black tank/toilet, I think I'm going to have to put my fresh water tank over the right hand side of both axles, approx 90"L, 26"W and 5" deep. It will push out behind the rear-most axles by a couple feet and will stick forward of the front-most axle by a couple of feet as well. I didn't think too much about servicing the tank. I figured once installed the only parts that might need servicing would be connectors/fittings on the entry/exit end of the tank.
Maybe I need to rethink putting all that weight on one side. Should the fresh water tank be centered?
I was thinking about putting a bank of batteries (three) up in front where the old 18gal fresh tank was in order to increase the tongue weight and the battery supply. A full 18 gal tank weighs about 144 pounds, plus the weight of the tank ... about 170 pounds. I figure three RV batteries weigh about the same.
You want to arrive at about 15% tongue weight, or more. That's 15% of the trailers weight, as it is ready for travel. That's about 750lbs for a 4000lb trailer.
If it gets lower than 10%, ride and tow quality will decrease. Much more than 15% will make a very tongue heavy ride.
I am not an engineer, nor do I know how to figure out the tongue weight addition of a full fresh tank that's 8feet behind the ball. I tried to copy the weight distribution of my former trailer, which is a 1971 TradeWind. It towed very well, and this Overlander now is very close in size and layout.
I would recommend that the tank is centered in the trailer, as seen from left to right.
You are looking good. Find a local metal fab shop to bend the cross members. Get all you need as the cost is for the first one for the set up. Looks like you are missing one in the back. Every two feet. I think they used #10 Gauge steel for mine. You can cut the outrigger curve with a sawsall if you have a way to hold it. Metal shop get do it really fast.
Are you going to paint the frame of just do rust convertion zinc thing?.
__________________ Let those who can play, let those who cann't watch....
You are looking good. Find a local metal fab shop to bend the cross members. Get all you need as the cost is for the first one for the set up. Looks like you are missing one in the back. Every two feet. I think they used #10 Gauge steel for mine. You can cut the outrigger curve with a sawsall if you have a way to hold it. Metal shop get do it really fast.
Are you going to paint the frame of just do rust convertion zinc thing?.
Yeah, the missing cross member in the back came out along with the floor
Thanks for the tips and encouragement too!
I was thinking about using this product to treat the rust on the frame, after wirebrushing and welding. It's priming and painting in one step, it's the right color, and it's gotten great reviews from a lot of people: http://www.eastwoodco.com/shopping/p...ProductID=1139
You want to arrive at about 15% tongue weight, or more. That's 15% of the trailers weight, as it is ready for travel. That's about 750lbs for a 4000lb trailer.
If it gets lower than 10%, ride and tow quality will decrease. Much more than 15% will make a very tongue heavy ride.
I am not an engineer, nor do I know how to figure out the tongue weight addition of a full fresh tank that's 8feet behind the ball. I tried to copy the weight distribution of my former trailer, which is a 1971 TradeWind. It towed very well, and this Overlander now is very close in size and layout.
I would recommend that the tank is centered in the trailer, as seen from left to right.
I've definitely been keeping a target tongue weight of approx 15% in mind. The thing is, I want to be at approx 15% loaded as well as unloaded. Keeping that in mind, I was hoping to put as much of the "dynamic" weight (water tanks) between the axles, at what would be approx the center point of the lateral balance. But you bring up a good point that's been concerning me with my current design and that is having the fresh tank off to one side, increasing the curb-side weight when loaded.
Time to look for some new Airstream schematics and see how they're doing it... I think I'm destined for some fairly major frame modifications any way I slice it at this point.
You will find that all double axle Airstreams made over the last 30 or so years have the fresh water tank between the axles from frame rail to frame rail. They get around 50 +/- gallons of capacity this way. The Black and Grey tanks are usually just ahead of (like our '85 25') or just rearward of the axles if there is a mid-bath, but rear bath models may have these tanks near the rear bumper.
I will attest to making the tank servicable, because we had a leak in our fresh water tank last year and ended up having the tank replaced. They just had to remove the lower pan the holds the tank in place, and then drop the tank down between the axles.
__________________ Joe WBCCI/VAC #5533
'94 28' Excella / '05 Hummer H2
(and casually seeking a vintage AS)
Joe... how deep are these over-axle tanks? If I fit it literally between the fram rails (side to side and top to bottom) then it can only be about 54" wide and 5.5" deep. I guess that works. The the tank will only need to be 39" long (front to back).
Hmmm... but then it will get in the way of the drains down to the gray tank unless I run them through the back of the lower bathroom cabinets which, I guess wouldn't be all that bad. Then the gray and black tank drains can meet up in one dump valve assembly behind the rear-most street-side tire.
Grrrr... because of the location of the shower, I don't think I can put my fresh water tank between the two axles. I think I'm going to have to put it starting just over the front axle, forward.
Joe... how deep are these over-axle tanks? If I fit it literally between the fram rails (side to side and top to bottom) then it can only be about 54" wide and 5.5" deep. I guess that works. The the tank will only need to be 39" long (front to back).
Hmmm... but then it will get in the way of the drains down to the gray tank unless I run them through the back of the lower bathroom cabinets which, I guess wouldn't be all that bad. Then the gray and black tank drains can meet up in one dump valve assembly behind the rear-most street-side tire.
My bottom of my fresh tank is well below the belly pan level (I'd guess it is 4-5 inches lower). That makes the tank perhaps 10-12 inches deep as it goes up to the bottom of the floor.
One other thing to note is that these newer trailers have torsion axles, while yours would not (unless you intend to change that). I'm not sure how this would impact tank fitment, if any.
__________________ Joe WBCCI/VAC #5533
'94 28' Excella / '05 Hummer H2
(and casually seeking a vintage AS)
Grrrr... because of the location of the shower, I don't think I can put my fresh water tank between the two axles. I think I'm going to have to put it starting just over the front axle, forward.
If you put your fresh tank just forward of the front axle, you might be able to put the grey tank between the axles (making your locations opposite of ours), but plumbing the dump valve might be a little tricky, but not undoable, to get it just rearward of the rear axle. You black tank will pretty much have to go below the toilet, wherever that is located.
__________________ Joe WBCCI/VAC #5533
'94 28' Excella / '05 Hummer H2
(and casually seeking a vintage AS)
My bottom of my fresh tank is well below the belly pan level (I'd guess it is 4-5 inches lower). That makes the tank perhaps 10-12 inches deep as it goes up to the bottom of the floor.
One other thing to note is that these newer trailers have torsion axles, while yours would not (unless you intend to change that). I'm not sure how this would impact tank fitment, if any.
Okay, now I'm really curious... what "protects" the bottom of the fresh water tank if it sticks down that far? Actually, it's probably tougher than that foil/belly skin, but does the belly skin cover the tank? That's about how far down the floor furnace used to jut, so I suppose it would be okay.
My frame rails are about 4.25" tall. That would mean a tank spanning the width of the rails, 8" deep wuold only have to be about 28" long to accomodate approx 54 gallons.
This is good news because my shower pan is on the floor, just inside of the wheel well, curbside. Moving rearward, almost immediately is the toilet. If I can stick the gray water tank just under the shower, then the sinks could drain down through the "double wall" where the shower pipes are and drop directly into the gray water tank. Cool. That would even leave me enough room to put the black tank under the floor. Previously I was thinking about building a "pedastel" for the toilet to sit on. Running pipes for the dump valve assembly should be pretty easy then.
I've been playing with the idea of switching to torsion axles, but only if my current leaf spring set up can't handle the added weight of the water tanks. I'm not sure what the rated capacity is on them just now. If anyone knows... please share!
Okay, now I'm really curious... what "protects" the bottom of the fresh water tank if it sticks down that far? Actually, it's probably tougher than that foil/belly skin, but does the belly skin cover the tank?
The water tank is protected by a rectangular metal box that bolts to the frame using (I'd estimate) 30-40 good size bolts. I think the Box is galvanized steel of a thickness much greater than the bellypan. It as to be, because it is actually this box that holds the plastic water tank in place, so it must support the weight of the tank plus about 50 gallons of water. There is just a layer of styrofaom between the box and tank for insulation purposes, with a few channels in the tank/foam for furnace air to circulate to keep the tank from freezing in cold temps. I think the styrofoam is perhaps 1" thick.
__________________ Joe WBCCI/VAC #5533
'94 28' Excella / '05 Hummer H2
(and casually seeking a vintage AS)
Great info, thanks!! I wish I had more later-model airstreams handy to inspect these types of things.
I think as long as I've got the whole thing torn apart, I may build in winter-proofing for my water system. Which actually raises an interesting idea... I could heat the floor using an under-tile type system. The same heating elements cuold be used for the piping, though I think I would want to have a low-draw system option for heating the piping and water tanks only...
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