Water tank in roof rack?

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Top of pagePrevious messageNext messageBottom of pageLink to this message   By Erik (Eriks) on Sunday, December 02, 2001 - 09:16 pm: Edit

Has anyone out there ever permanently mounted a water tank,lets say 10-20 gallons into an adventure roof rack. I saw some tanks that would be flush with the top of the side rails and is about an inch smaller in width so it would drop in nice. with a faucet permanently plumbed and a hose that could just screw on I thought it would be great for those trips that are 3-4 days long for cooking and what not as opposed to having a bunch of tanks bouncing around. The only con I could see was the high center of gravity. Any thoughts?

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Brett Symons (Tizeye) on Monday, December 03, 2001 - 12:34 am: Edit

Not a good idea for 2 reasons
1.Having 50 to 100 kilos over your head would raise you centre of gravity to much, not too bad for the black top, but too much for off roading.
2. Imagine a 3/4 full tank of water up there, 150kg sloshing around and you have to sweve or make a sharp turn in a hurry? I would recon it would seriously affect your handling, possably even flip you
If you want water tanks the best place to mount them would be down low

Top of pagePrevious messageNext messageBottom of pageLink to this message   By jay caragay (Jcaragay) on Monday, December 03, 2001 - 08:45 am: Edit

Are you sure about this?

I'm asking because I recall seeing Discos loaded with a several jerry cans. Keeping in mind that each can is abot six gallons, three of them is 18gallons.

Is that so much more different than having one 10-20gallon tank?

Just a question

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Leslie N. Bright (Leslie) on Monday, December 03, 2001 - 08:58 am: Edit

When you use jerry cans, each one is a "discrete package"...

For example, if you have a jerry can of fuel, you should pour all of the fuel from the can into the tank. I don't recommend leaving a jerry can partially full. (heats up, gas vapor, not fun)

So, cans are either empty, or they're full. Yes, a full can is acting like a discrete weight, but you're not going to have a velocity vector from sloshing. But, even if you didn, you're limiting it to 6 gal.

Same with water. Not as critical about having partially-full cans, but only for the sloshing issue.

Now, instead of a bunch of 6-gal cells, you have one big water tank. It's half-full, and the load is distributed evenly across the tank. Let's say you're making a 90-degree turn from a level spot of road onto a steep downhill. As you start to nose over to one side, the water will all run to that side, and you may very well find yourself with that extra weight on that side tipping you over further and faster than you were expecting...

If the water had been in 6-gal cans, then it can't shift weight from one side of the vehicle to the other. In a single large tank, your weight will be shifting all over as you traverse irregular terrain. And, because it is on top of your truck instead of down low, you'll REALLY feel it... there's a multiplier effect from the distance above the CG.

I like the idea of a permanent sink. But if you want to do something like that, check out the Dormobiles. They had sinks, but they kept the tanks low instead of overhead.

Mi tres centavos....


-L

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Leslie N. Bright (Leslie) on Monday, December 03, 2001 - 09:03 am: Edit

Jay,

It's not the weight of the jerry-can plus contents that is the problem.

For a large tank, it would be the shift in weight THAT far above the CG...


-L

Top of pagePrevious messageNext messageBottom of pageLink to this message   By John Kruger (Johnnyk) on Thursday, December 06, 2001 - 10:39 am: Edit

What about tires on the rack? The significant weight of two tires should raise the CG.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Leslie N. Bright (Leslie) on Thursday, December 06, 2001 - 11:57 am: Edit

Yes, it does. But, it is stationary (if ya lash 'em down... Don't just throw 'em up there!!!)

Although your CG is raised, it's not moving around.

With the large tank on top, not only have you raised your CG, you're constantly moving it as you go up and down, tilt left to right, etc. It's like having me (or Ron ) run up and jump on your down-hill side all of the time.


-L

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Kyle on Thursday, December 06, 2001 - 11:59 am: Edit

Water in a tank also has inertia , something to think about when putting some on the roof... :)

Kyle

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Leslie N. Bright (Leslie) on Thursday, December 06, 2001 - 12:01 pm: Edit

Bingo! Even extra to think about...

-L

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Thursday, December 06, 2001 - 12:35 pm: Edit

Erik, Jay - here's what you get for the jerrycans on the roof rack:

http://www.t-r-j.com/Los-Coyotes/10Dec00/img52.jpg

open liquid surface decreases the static stability to a much greater degree than the solid object of the same mass and shape. look for any link on a ship roll stability, you'll see it.

dynamical sloshing is even worse. most large tanks have anti-sloshing baffles in them to dampen this effect somewhat.

peter

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Thursday, December 06, 2001 - 12:39 pm: Edit

an example:

http://heiwaco.tripod.com/epunkt316.htm

a quote relevant to this thread:
The Germans 1995-1999 did not make any stability calculations with water on the car deck in the superstructure. The Germans never considered that
any water on the car deck would flow to the lowest point on the car deck and would trim and heel the ship.


interesting that there's many links concerning this marine accident.

peter

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Thursday, December 06, 2001 - 12:41 pm: Edit

and here's the math:

http://www.fas.org/man/dod-101/navy/docs/swos/dca/stg4-03.html

peter

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Ho Chung (Ho) on Thursday, December 06, 2001 - 02:16 pm: Edit

peter, thanks for the link, very schooling. :)

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Thursday, December 06, 2001 - 02:25 pm: Edit

i was too lazy to reach out for the book :)

peter

Top of pagePrevious messageNext messageBottom of pageLink to this message   By joshua on Thursday, December 06, 2001 - 05:41 pm: Edit

I drove a Tanker Fire truck for the Fire dept for a few years. We did a ton of brush work, up logging roads and in the back country of the adirondac mountains. Headed to the fire was the only time the tank was full.

May I suggest baffels in your tank if you are going to custom build one? This will draasticly improve your sloshing factor, and make it more sturdy up there.

I have driven a tanker without baffels and it is scary, talk about a quick lane change if the water sloshes to fast...

:)
joshua

Top of pagePrevious messageNext messageBottom of pageLink to this message   By D Cantrell (Discodad) on Thursday, December 06, 2001 - 07:43 pm: Edit

Reminds me of how my Motor Home drives when the Holding tanks are full "Danger Will Robbinson Danger"

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Thursday, December 06, 2001 - 08:46 pm: Edit

hehehe

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Erik (Eriks) on Thursday, December 06, 2001 - 08:59 pm: Edit

The tank that I saw did have baffles that started about a half inch from the top and went down to about a half inch from the bottom. I think there were 4 of them going from front to back. The guy at the shop said it was the best baffles he had ever seen in a tank. He said in most tanks the baffles if at all have about 1 1/2 inches of gap on top and bottom. Would this make a difference? Sorry I didn't mention it before.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By E Snyder on Thursday, December 06, 2001 - 10:55 pm: Edit

Erik-
Do you have a link for the tanks? I've been looking into this as well. Thinking about making a "tank" out of 8 or 10 inch black pvc pipe, capped, with a tap in one end for a hose. Haven't done the math, (can't actually remember those volume of a cylinder days in 9th grade geometry) but a 6 ft. tube of that size would hold a decent amount of water. I've seen similar set-ups on vehicles on the OuterBanks. If you have a link for low profile tanks, let me know.
Thanks, Enoch.
PS- And relating to the previous conversations, the side to side slosh would be almost non-existent. Front to back would have little or no effect on the truck, perhaps in braking a bit.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Mike B. on Friday, December 07, 2001 - 12:16 am: Edit

Hmmm. This is a most interesting post. I too have wished for fresh water out on the trail. I purchased a used aluminum water can with a ceramic lining from a Army Surplus store. I then bought two brass needle valves and plumbed them into the top; one for the water spout and one for the vent. I lashed the tank up on the roof rack. When I needed running water, I just opened both valves and presto... running water.

However, the valves that I found are really too small to let sufficient water flow to make it really usefull; there are brass needle valves with opening about the size of a pencil. The tank is too small to allow me to fit regular water spigots, so I'm at a loss to find the proper valves for the project. Have you guys given any thought as to which valves you might use?

Thanks,
Mike B.

P.S. Please keep me posted about the progress of your projects.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By D Cantrell (Discodad) on Friday, December 07, 2001 - 12:46 am: Edit

Erik,
Idea, Make a tank to go in the rear cargo where the jump seats mount. Then shelf between the 2 tanks stack all your gear ontop of the rack and below and that will leave the roof rack for the light weight stuff and expedition boxes. Get some HD springs in back

D

Top of pagePrevious messageNext messageBottom of pageLink to this message   By E Snyder on Friday, December 07, 2001 - 07:51 am: Edit

Having the water overhead helps give you more pressure, for showers, etc. Of course, you could mount a small pump in the tank in the cargo area...

Top of pagePrevious messageNext messageBottom of pageLink to this message   By D Cantrell (Discodad) on Friday, December 07, 2001 - 07:56 pm: Edit

If the tanks are sealed SS or Alum. Pressurize them. Wala Shower. Get realy creative.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Erik (Eriks) on Friday, December 07, 2001 - 08:05 pm: Edit

E Snyder: sorry dont have a link, I just saw them at an outdoor show locally and cannot remember the brand.
Discodad: I like your idea of in the jumpseast location. Would cost more because of need of pump for good pressure and a custom tank but would eliminate the center of gravity prob. I think that would justify the cost. The plus of being on top though is if your tank is black, you dont have a cold shower.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Friday, December 07, 2001 - 08:05 pm: Edit

There's some generous area under body, between the door sill and frame rail. to me it looks like it could hold a 10-gallon tank easily (i even see how a bottom plate can be used as underbody protection). Pump? every boater's store has at least two or three varieties - check West Marine for starters.

peter

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Kyle on Friday, December 07, 2001 - 08:06 pm: Edit

As mentioned above you can simply plumb your compressor into the tank and get pressure that way.....


kyle

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Kyle on Friday, December 07, 2001 - 08:08 pm: Edit

The side affect would be an air tank when the thing doesnt have any water in it.. :)

Kyle

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Friday, December 07, 2001 - 08:34 pm: Edit

who needs air tank, Kyle, everyone's lugging CO2 tanks around :)

but yes, the more i think of it, the more it makes sense. we've got space for two tanks, one on each side...

peter

Top of pagePrevious messageNext messageBottom of pageLink to this message   By D Cantrell (Discodad) on Friday, December 07, 2001 - 09:29 pm: Edit

Get a hand pump from a RV tralier supplier. Save the C02 for the tires

Top of pagePrevious messageNext messageBottom of pageLink to this message   By jay caragay (Jcaragay) on Monday, December 10, 2001 - 03:06 pm: Edit

Here in Baltimore, a local RV supplier carries water pumps (either AC or DC) for similar purposes. they are small and can easily be hid under the frame and cost about $85.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By D Cantrell (Discodad) on Monday, December 10, 2001 - 03:22 pm: Edit

I have a on demand one in my Winniebago but size wise not much room in the back a hand pump might be a simpler solution or a plast of CO2?

Top of pagePrevious messageNext messageBottom of pageLink to this message   By p m on Monday, December 10, 2001 - 03:31 pm: Edit

you may blow the tank with a blast of CO2 :)

peter


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