Tongue weight before & after dump

[Phoenix PAL]

Have you noticed this? I've never seen it discussed in the thousands of discussions about tongue weight.


My 212QBW t/w actually went UP nearly 100lbs after dumping my blk/gry tanks yesterday. Since the drains are in front of the axle, I just assumed the tanks were either in front of or on top the axles. Guess not.



And I can't find a sub-floor layout drawing anywhere. Hopefully it's available on request.


Paul

[JFlightRisk]

Our 19RD is the 2 foot shorter Jay Flight version of the 212QBW, and the gray tank forward of the front axle. The black is partially above it.

[Midnightmoon]

As best as I can tell, the only tank that is fully in front of the axles on my 22BHM is the fresh water tank. The black is fully behind and the grey is above and slightly to the rear of the rear axle.

We discovered this one of the first times we went boondocking for a weekend and towed home with an empty fresh and full black and grey. It was an absolute handful to tow.

[Bob K]

Both of the tanks on my 185RB are behind the (single) axle. With the axle acting as the fulcrum for the lever, my total trailer weight goes up when the tanks are full but the tongue weight goes down.

Since I'm pulling with a Tacoma, I sometimes try to take advantage of this lever by putting heavy items behind the axle in order to reduce tongue weight...ensuring, of course, that I always have at least 10% of the total trailer weight as tongue weight, which I exceed handily.

[damaltor]

Interesting? What year is your 212QBW?

On our 2020 212QBW, the grey tank is centered about 2.5’ in front of the front axle, the black tank is close to being centered over the front axle and the fresh water tank is close to being centered over the back axle.

[MrSaxy]

Is there a schematic or drawing of the location of the tanks on a 2018 21QB?

[TWP723]

Remember, it doesn't take a whole lot of discharged weight to add to your tongue weight. It really depends on how counterweighted it is. Emptying a tank even directly over the axles can add additional tongue weight. All weight that is added or subtracted from smaller trailers greatly affect it's balance of weights front to rear. If you were holding in both tanks, that's roughly 80 gallons total of liquid weight. Probably close to the hundred pounds you found on the tongue.

[damaltor]

Originally Posted by TWP723

Remember, it doesn't take a whole lot of discharged weight to add to your tongue weight. It really depends on how counterweighted it is. Emptying a tank even directly over the axles can add additional tongue weight. All weight that is added or subtracted from smaller trailers greatly affect it's balance of weights front to rear. If you were holding in both tanks, that's roughly 80 gallons total of liquid weight. Probably close to the hundred pounds you found on the tongue.

I get that, but the OP states his tongue weight went up after dumping the tanks. If his grey and black tanks are positioned on top and in front of the front axle, how is that possible?

[TWP723]

Originally Posted by damaltor

I get that, but the OP states his tongue weight went up after dumping the tanks. If his grey and black tanks are positioned on top and in front of the front axle, how is that possible?

Pretty sure there are fresh tanks to the rear and black and gray over the axles, or close to it. Emptying the black and gray together would affect tongue weight. Think of a see-saw with a heavy weight positioned over the center. Remove that weight and the see-saw goes down on the heavy side because it's not perfectly balanced over it's center point. Just like how the tanks aren't directly and perfectly positioned over the axles. The weight of both tanks held the nose up just enough to have a 100 or so pound difference when emptied. Like I said, it doesn't take 100lbs. to be removed from the unit to create a 100lb. difference on the tongue. Draining the tanks relieved the weight across the entire unit and applied more to the tongue.

Mind you, this is my theory. But working with weight distribution on an aeronautical level tends to make me believe this is what's happening.

[Phoenix PAL]

Thanks for everyone's feedback. It appears that every model's tank placement is a bit different. @Damaltor your 2020 is clearly different than my 2016, or I would have lost tongue weight, not gained 100lbs. With 2 axles, you'd think there was enough real estate to center all 3 tanks over the 2 axles.



As it is, I (all of us?) tow with 3 different tongue weights: 1) Here in the southwest, we always start with full freshwater. 2)Then, leaving the campsite I transfer the remaining fresh water to the black tank to help flush. I drive with that weight until we get to the dump, and then 3) drive home empty. Clearly 3 different weight distributions varying as much as 100lbs (assuming I repack the same way)


All this tells me is that I need to keep my Sherline scale handy and check it each time and not assume.


Thanks all

[Phoenix PAL]

I guess, after looking at my calculator, it's not a big deal as +/-100lbs is just a 2% change in tongue weight.

[JFlightRisk]

From what I've gathered, the tank placement is dependent on where toilet and sinks are located on any given floor plan. The black tank(s) are usually directly under the toilet(s), and the gray tanks are as close to the sinks and shower as possible.

Rear baths would have their black and a gray tank more towards the back, and floor plans like our TT have them more forward, leaving room for the fresh water tanks to occupy the space in the frame farther back.

The plumbing for the gray side is easier to route to tanks, since the pipes are smaller, and you really want the toilet plumbing to be as directly straight down as possible, for obvious reasons.

[Phoenix PAL]

@JFlightRisk
You're right. And I'm sure that for every floor plan the Jayco engineers have given thought to tank locations. I've wondered about the black tank being all the way forward or aft under the head.

Our's is midship right over the axles.

Here's what I found today as we prepare to go back out: The full fresh water is the same tongue weight as the full grey and black tanks. So it's when I empty those that the weight goes way up and I need rearrange my stuff... ie for the trip home.

It's taken me awhile to home in these peculiarities [emoji849][emoji16]

[LuckyDuck]

Originally Posted by damaltor

Interesting? What year is your 212QBW?

On our 2020 212QBW, the grey tank is centered about 2.5’ in front of the front axle, the black tank is close to being centered over the front axle and the fresh water tank is close to being centered over the back axle.

Our 2018’s tank placement is exactly the same as far as I can tell. The OP’s rig is a Baja, which, as I recall, has about double the FW capacity (80 gals). I wonder if that entails two connected FW tanks with one in front of the axles? Or a different placement because of the size/configuration? Just thinking out loud but maybe that explains it?

We generally don’t run with water in the FW tank, and I typically dump black and gray before traveling. But a few times we’ve towed with a partially filled black tank and I didn’t notice even a slight difference, FWIW.

[RKHengst]

Originally Posted by Phoenix PAL

I guess, after looking at my calculator, it's not a big deal as +/-100lbs is just a 2% change in tongue weight.

Better check your math on that one. If 100lbs is only about 2% of your tongue weight, your total tongue weight would be 5,000lbs. And that’s not likely…

[Phoenix PAL]

@ luckyduck .. no our fresh water is only 40 gallons. Apart from the inverted axles and larger propane tanks, I'm not aware of any differences from the non baja.

@RKH by 2% I was referring to the difference between 450lbs 8%, and 550lbs 10% of 5500lbs

We are going to be spending 10 straight weeks in it this summer with 27 different stops, so I'm really trying to pin down optimum cargo distribution.