tongue weight, dumb question - Page 3 - Fiberglass RV


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Old 07-25-2007, 06:17 PM   #29
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I wouldn't obsess about 10 pounds, either... but that's before any cargo!

Also, I'll happily run up to a limit, but in this case the rear of the tug will be sagging (more suspension compression than ideal), because of the hitch weight, which will not help handling. This means either some rear suspension help is appropriate (which we are discussing separately), or - one more time - fix the trailer.

I would rather set up the rig properly, than tiptoe on the edge.
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Old 07-25-2007, 08:40 PM   #30
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Here's a more-or-less simple solution if you have a local weigh station. Load up your tow vehicle and trailer, then weigh your tow vehicle alone, then the tow vehicle with the trailer without rolling the trailer on the scale, then get the weight on just the trailer axle. The difference between the tow vehicle with and without the trailer is your tongue weight; the weight on the trailer axle plus the tongue weight is the total trailer weight.

--Peter
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Old 08-18-2007, 10:45 PM   #31
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Here is some data that relates to this thread. having just purchased a BigFoot 21 that has a design issue with tongue weight (considering the factory just added about 275lbs of ballast weight to the front of this frnt bdrm model) I decided to purchase one of the Sherline tongue weight scales as someone here recommended (good $100. investment in my opinion) and see what weight I had on the tongue. With the water tank full (it is in the front on this model) and the holding tanks empty and our initial provisions stowed aboard (we just got the trailer so more will likely be added as time goes on), the tongue weight was 560 lbs (scale is supposed to be + or - 2%). The weight of the trailer has to be over 5000 lbs, it was almost 4700 lbs as shipped by BigFoot with the options etc. installed but with tanks empty, propane empty, and no battery. So at 560 lbs the tongue weight is OK but marginal in my opinion based on what I read etc. Especially considering some dry camping would result in moving the water at 8lbs per gallon from the front storage tank to the rear holding tanks. I removed the spare from the rear bumper and that increased the tongue weight to about 580 lbs, I added the spare and a few tools to the front outside access storage chamber and that left the final tongue weight at almost 640 lbs (better). I plan to leave the tire up front (in the storage area until I figure another place to mount it). At some point I will add a bike rack to the rear bumper and try to keep the weight of rack and bikes below what the tire and mount weighed. I can now see why they added the ballast weights as these trailers are light in the front and to adjust it by moving axles etc. would be a new trailer design and not feasible. As soon as we get the trailer completely loaded I will weigh the entire package to determine what the tongue weight range should be. Maybe not a neccessary exercise but interesting. Ed
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Old 08-19-2007, 09:03 AM   #32
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Oops, correction on my tongue weight data in previous post. The water tank is not full, probably half full which is good news as this is likely a more typical condition when towing. The propane tanks (two large 30 lb variety) are close to full. I will fill the water tank and update the tongue weight data. Ed
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Old 08-19-2007, 08:21 PM   #33
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Oops, correction on my tongue weight data in previous post. The water tank is not full, probably half full which is good news as this is likely a more typical condition when towing. The propane tanks (two large 30 lb variety) are close to full. I will fill the water tank and update the tongue weight data. Ed
Well here goes another attempt to share the data I've collected on my BigFoot 21'FB tongue weight. As indicated in my earlier post I am using the Sherline tongue weight scale. This is a new trailer so it has the ballast weight (275lbs I think) welded into the A-frame and as a cross member near the front of the frame. I used 8 lbs/gal for water weight in the calculation parts of this summary.
With the spare on the rear bumper (cont kit etc. from factory)
Water tank full, propane full, holding tanks empty TW=680 lbs
trailer weight est to be 5190 lbs TW= 13.1%
Water tank emp, propane full, holding tanks empty TW=410 lbs (calc)
trailer weight est to be 4920 lbs TW= 8.3%
With the spare in the front compartment (as I now have it)
Water tank full etc. TW= 760 lbs
trailer weight est to be 5170 lbs TW= 14.7%
Water tank empty etc. TW= 490 lbs (calc)
trailer weight est to be 4900 lbs TW= 10%
If you assume all of the 275 lbs of ballast is tongue weight (most of it
should be) and look at the TW without the ballast added under the above conditions (with the trailer 275lbs lighter of course) the TW would be
in the range of 3% to 10%. It seems you would want to tow this trailer with the water tank full and hopefully with the holding tanks close to empty. I went through this exercise hoping to convince myself I could remove the ballast weights but I think (sadly) that they are needed and I would consider adding them on if you haven't. I met someone in Oregon who traded a 21' FB in on a BF 25' trailer because of being frightened by this swaying situation. I guess I just bought an expensive trailer with an inherent balance design issue -- but I like the trailer and knowing the situation I will manage it. I'm not sure what the implications of the rear bedroom model are but having the water tank in the back I guess makes it the opposite of the front bedroom and you would want to tow with it as empty as possible?? Hope I haven't confused everyone. I do remain a little concerned that if you were on a dry camping trip you might be returning with water tanks and holding tanks in a condition that is not too good for travel (tongue weight)?? Ed
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Old 08-19-2007, 11:28 PM   #34
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Thanks Ed, this is important info. Sorry for your issues though.
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Old 08-20-2007, 10:56 AM   #35
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Quote:
Here's a simple method for weighing your tongue with a bathroom scale.
Pete, best diagram of that method that I have seen.

With this, and other, methods isn't it important that the tongue weight be measured with the trailer at the same level as it is towed? Wouldn't the same trailer, if weighed first nose down, then level and finally nose up, return three different figures?
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Old 08-20-2007, 01:58 PM   #36
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With this, and other, methods isn't it important that the tongue weight be measured with the trailer at the same level as it is towed? Wouldn't the same trailer, if weighed first nose down, then level and finally nose up, return three different figures?
Yes, exactly.
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Old 08-20-2007, 04:03 PM   #37
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Brian's right, the angles do make a difference, and that difference may differ between different trailers depending on construction and loading.

The very best way to do all this stuf is to do it like it goes down the road. However, as long as you have it all set up to weigh, try all three positions to see how they differ. If all your weight inside is low, they won't differ as much as if they were high, because one part of the weight change is the center of gravity (COG) and the higher it is, the more it will move for the same angle.

Likewise, when driving, the trailer and tow vehicle weights will be moving forward or back as the road goes down or up, respectively.

For an extreme example, picture your tow vehicle on a two-platform scale, with the front platform gradually rising. Eventually, you would have 99.44% of the weight on the rear.... Same holds true for coupler vs axle weight when the trailer is off-level. However, I should point out that all this weight transfer is relatively negligible at the shallow angles, presuming COG is also in line (A roof a/c would make some difference, for example).

Keeping the going-out and coming-back weights in mind is also a good thing. My old Jayco had the LP and fresh tanks waaaay front of the axle, with the food storage over the axle. As my trip progressed, the LP left and the fresh water and food moved to the gray and black tanks which were behind the axle. I was aware of the theoretical transfer of weight, but never bothered to measure it because I didn't perceive it on the road (Only had ten gallons of fresh and hardly used much LP, so apparently not enough weight was transferred to make a noticeable difference in handling).
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