'89 Bigfoot 19-B weight and bad math? - Fiberglass RV


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Old 04-25-2014, 01:36 AM   #1
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Name: Dave
Trailer: Bigfoot
Washington
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'89 Bigfoot 19-B weight and bad math?

Am I over-calculating this or forgetting to carrying a 1, somewhere?

I took my empty T.T. and SUV to the city dump to use their scale in order to get a reasonably accurate weight. Vehicle has a tow limit of 3500 lbs. so I want to be sure to keep within this range when I load it up, if for no other reason than to keep the wife happy and kids safe. Personally, I'd bog it down till the tires bleed.
First, I used our bathroom scale to determine the tongue weight which came out at about 380 lbs. Seemed a bit high, but went with it. Then I drove the vehicle, only, up on the city scale (with trailer still attached), got that weight (5300 lbs), then pulled forward with both (8160 lbs). I then subtracted my personal weight (210lbs) and that of my daughter (35lbs) and the tongue weight (380lbs) to get the vehicle net weight. This came out pretty close to the vehicle's stated curb weight which is roughly 4700 lbs. I then subtracted this from the total weight of 8160, ending up with a T.T. weight of almost 3500lbs! I know the stated weights were generic back in '89 but this is quite a bit of difference. My T.T. does have an AC unit, fridge, shower, oven, etc. and I think there were a few gallons of water and propane in the tanks. I was hoping the dry weight was somewhere below 3k, which would give me about 500 lbs or so for supplies and sleeping bags since we only use it for local, weekend jaunts. Someone please tell me I am engaging in bad logic. It seems like I might be mis-calculating my personal weight(s)
Thanks!
Perhaps I should just take it to a pay-to-weigh scale and detach.
~Dave
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Old 04-25-2014, 01:58 AM   #2
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Now that I am thinking on this again, I am certain I goofed with personal weight(s) but how do I handle the tongue weight? Will it be added to the trailer weight or should it be withheld from all calculations? except, of course when considering GVWR .
IE, if I and my daughter had gotten out of the vehicle, the first weight for vehicle only would have been 5050 lbs, and the second weight for both would have been 7910 lbs. Less 4670 lbs for the curb weight puts the trailer at 3240. Now, is the tongue weight subtracted again from the T.T. weight or left off everything? My brain hurts, so i am going to bed.
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Old 04-25-2014, 10:37 AM   #3
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One never anticipates the Spanish Inquisition or the complications of trailer weighing in the busy world of commerce. Wait until you've tried to shinny up the pole at CatScale to get close enuf to the speaker to get the attention of the operator in a bldg 100 yds distant. Develop a simple protocol B4 you get weighed. The very simplest is camper axle only on the scale while hitched and then camper off the hitch, axle and tongue jack on the scale. Subtract the former from the latter to eliminate tongue weight.

Devoting more time to guesstimating and fudging a failed weighing attempt isn't likely to make a 19' example of a notoriously heavy trailer a comfortable match to a tow vehicle of 3500lb tow capacity. The thread "Trailer weights in the real world" provides insight on the curb weights of commonly available fiberglass campers. Check out the Bigfoot weights.

jack
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Old 04-25-2014, 11:57 AM   #4
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"Towing capacity" as stated by tow vehicle mfr. means total weight of trailer including tongue and every last thing in/on it.

FYI:

At 3500 pounds your Bigfoot 19er would actually be coming in a little light for the brand, at least when comparing to those BFs weighed in Frederick's "Real world trailer weights" thread. Link to thread.

Even the 17.5 footer there comes in well over 4,000 pounds.
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Old 04-25-2014, 05:04 PM   #5
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There two 17.5 BFs in Fred's tabulation. The first is listed as 2990lbs, the second at 4400. Not much of a sample of course and we don't know numbers for add on gear like gensets and bikes and such but I'd count on the higher number being the one prevailing in the real world and the 19' being heavier.

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Old 04-26-2014, 11:16 AM   #6
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Chances are.....

if one is down to "splitting hairs" in the weight department (aka trying to weigh the load down to the last POUND)...you're gonna be overweight....

In the boat towing community there is a generally accepted rule of thumb for relatively carefree towing....read the towing capacity listed for your vehicle (on the door or the owner's manual)....take 25% off of that and that is what you can tow comfortably down the road weight wise...(listed weight of trailer + boat + your estimate of what you're going to be packing in the boat)

If you live in a place like Colorado make that discount a little bigger....if you're going to tow in Florida you can make it smaller

Use the formula and you won't be back at the car dealer a month after buying the trailer "of your dreams"....

In the pic below the truck's listed towing capacity is 4700lbs (with OEM tow package).....what's behind it weighs 4000lbs.....the rig towed just fine but the truck worked pretty hard on the hills.....if the tow had weighed any more it would have been unworkable....in the real world
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Old 04-26-2014, 12:35 PM   #7
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Also see 80% of listed tow cap used frequently as a reasonable upper limit on trailer weight. The way this is usually stated is that you use the short form rule of thumb if you aren't capable of or don't wish to make an accurate predictive calculation of the weight added to TV in towing service by humans, pets, gear, coolers. This means 3500lbs has a recommended yield on tow weight of 2800.

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Old 04-26-2014, 12:46 PM   #8
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In my real world I like 6500lbs tow cap. and 3450lb curb weight trailer. 80% of tow cap is 5200 and 3450 is 66% of that. I like to arrive in the same tug I started with.

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Old 04-26-2014, 01:05 PM   #9
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Good day Dave.... what tow vehicle are you using? Thnxs
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Old 04-26-2014, 02:12 PM   #10
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Quote:
Originally Posted by hogzilla View Post
First, I used our bathroom scale to determine the tongue weight which came out at about 380 lbs. Seemed a bit high, but went with it. Then I drove the vehicle, only, up on the city scale (with trailer still attached), got that weight (5300 lbs), then pulled forward with both (8160 lbs). I then subtracted my personal weight (210lbs) and that of my daughter (35lbs) and the tongue weight (380lbs) to get the vehicle net weight. This came out pretty close to the vehicle's stated curb weight which is roughly 4700 lbs. I then subtracted this from the total weight of 8160, ending up with a T.T. weight of almost 3500lbs!
Reverse math:
TV + people + trailer = 8160 lbs.
Less TV + people = 4700 + 210 + 35 = 4945 lbs
Equals total trailer weight of 3215 lbs

TV + People + calculated tongue = 4945 + 380 = 5325
weighed vehicle (trailer off scale) = 5300 (pretty darn close) given scales are not accurate to the pound.

Calculated axle weight = 3215 - 380 = 2835

Scaleman may correct me, but what you need to do is go back to the scales and get the weight of your truck with the familiy in it. Then go back with the trailer attached, get the truck axles only weight, combined weight, and trailer axle only weight. Then you can do the math to figure out the rest.
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