I do a 3 way weight when I go. Truck / Truck & Trailer / Trailer. Doesn't cost me and they have fun doing it and awaiting my math in the lot afterwards. I do love my small town! 

Here's how you can get it without having to disconnect the trailer back at the scales. Did you already get the whole rig weight when you were there? If not, go get that, then come home, drop the trailer, and go get the weight of the tow vehicle by itself. Then the trailer weight is 

total rig - tow vehicle alone and tongue weight is total rig - trailer axle - tow vehicle alone.

If they'll let you, and they should because it only takes a few seconds, try to also get each axle's weight by adding an axle at a time as you go through the scale. You can then later use subtraction to get each axle weight. That will give you more data and improve the accuracy, but you can do it as I describe above and that should be good enough. 

One more thing, if you have a WDH it needs to be in place but untensioned for the measurements. And leave it on the TV for that measurement.

Water weights 8.3 lbs per gallon so 30 gallons of fresh water weighs 250 lbs. Since the FWT is forward of the trailer axle, some of the additional load will go to the hitch and some to the axle.  Measure the distance in inches from the trailer axle to the hitch and from the trailer axle to the midpoint of the FWT. The additional weight on the hitch will be 250 lbs times the distance from axle to tank divided by the distance from axle to hitch. The rest will go to the axle. If you only fill the tank half full then use 125 lbs rather than 250. Simple!

Water weights 8.3 lbs per gallon so 30 gallons of fresh water weighs 250 lbs. Since the FWT is forward of the trailer axle, some of the additional load will go to the hitch and some to the axle.  Measure the distance in inches from the trailer axle to the hitch and from the trailer axle to the midpoint of the FWT. The additional weight on the hitch will be 250 lbs times the distance from axle to tank divided by the distance from axle to hitch. The rest will go to the axle. If you only fill the tank half full then use 125 lbs rather than 250. Simple!

[/QUOTE] OFFGRID

Would this work in reverse if figuring tongue weight on a 177 where the FWT is BEHIND the axle?  So one would subtract tongue weight using the above formula?

Colt, I bet you can already answer your own question about FR providing a weight & balance sheet. Three little words; "avoidance of liability". You can't give someone a tool (W&B sheet, schematic, or hydraulic jack) and tell them to have at it, at least not without either assuring folks are trained in the proper use of the tool or have waived any claim to damages from improper use. It doesn't help them sell more trailers and it could cost them a bunch of legal fees, so why do it? Sigh...

Just like their use of a generic "owners manual" for most of their trailer lines, it's really a matter on not wanting to incur the cost of writing trailer specific materials.  

I knew I'd get a response on that one.

It doesn't work the way you suggest in practice, or maybe in a way it does. In manufacturing companies I've worked for there are always staff engineers who could easily write the instructions so that was budgeted, but not staff attorneys who could vet them and write the disclaimers. That would have cost additional unbudgeted $$. So documents requiring legal review and input never happened unless they were essential for sales of the products.  And specific materials were always discouraged due to the risk that they would not be maintained properly and result negligence claims.

In aviation, W&B worksheets are essential to keep the pilot and their passengers alive, so they are done as a matter of course. The customers are pilots who have been trained in the use of these materials and tested and licensed by the FAA certifying that they know how to do so. Not so with RV owners, the vast majority of whom wouldn't have the faintest idea what a W&B sheet was for. 

Going back to Colt's original comment, my point is that just because the FR engineers have a W&B spreadsheet that they use when designing their trailers doesn't mean that that can be provided for external use by customers without a substantial outlay of additional engineering and legal resources. And to what end? A W&B sheet is not either expected by trailer customers or customary in the RV industry. Better not to do it at all, as I'm quite certain both their head of engineering and their chief counsel would advise. 

There is no reason not to give a W&B work sheet, except cost.  It has nothing to do with legal liability or lawyers.  

Like most non-engineers, you are underestimating what would be required to do the job of properly releasing a W&B worksheet in a way that doesn't put the company at risk. The FAA's handbook for aeronautical engineers on W&B is 114 pages. The airman's knowledge handbook that all pilots are trained and tested on has a half dozen pages on the topic, and in pilot training you spend a whole 2 hour session on it usually. A typical POH (pilot's operating handbook) for a small aircraft devotes 10-12 pages to the topic. Trailers would likely be more complicated, because the loading scenarios for a trailer are a lot more complicated than for a small airplane. The safe operating envelopes are a lot more complex too, because there is a second vehicle involved. 

So, you can call a trailer manufacturing company not wanting to incur all that cost "cheap" but why would it when no one expects it to do so? If the company just provided anyone who asked their engineering W&B worksheet, without all the training and accompanying documentation, change control procedures whenever the design of each trailer changed, etc, someone would misuse the tool, a death or injury would occur, and the company would be subject to a lawsuit. 

Is a lawsuit justified in that case? I think almost certainly yes, because surely the company has a duty to try to assure that the parties that it gave access to the tool were capable of using it properly. That's relatively easy when its a trained in-house engineer who has a supervisor and there are review and test procedures for every new trailer design. Not so for the general public. Its more like giving a chain saw to a 10 year old, pointing him at a tree and saying have at it. But that's just my observation, now we are in your area of expertise, not mine, so I will be interested in your thoughts on that. 

 

As for W&B, a trailer's balance is not likely to be as complex as an aircraft, but I could be wrong.  The Zen of W&B has worked quite nicely for me and our TT.

The failure to give adequate product use instructions, such as how to balance your trailer, is more fertile ground for product liability suits than would be a simple chart to figure out where the heavy stuff should go..  You are mixing the complexity of aeronautical physics with a simple travel trailer that usually only moves in 2 dimensions and is generally connected to the ground.  Why make things needlessly complex?  The Zen of trailer balance works just dandy, until it doesn't.

Maybe we should emerge from retirement and seek out plaintiffs who have gone off the road from not having their trailer loading right. You can litigate and I'll be your expert witness. I only want $500 per hour

But I think you've hit the proverbial nail on the head. Most of the time, the zen approach to trailer w&b works just fine, and ppl don't die. Lots of pilots use the zen approach too, but the difference is that generally you don't die if you mess up your trailer W&B. It has happened though, no doubt. So it will come back to what is reasonable and customary in the industry, right? If you screw up your zen in the trailer that's on you at this point, there is no case law putting it on the manufacturer (until you get your specialized practice going and call me as a witness anyway). 

If you screw it up in your airplane, that's on you too, unless Cessna screwed it up, and they didn't, and besides, you were trained, and Cessna knows you were trained. If FR published a w&b worksheet and screwed it up, or didn't make sure you knew how to use it, they have now changed what is reasonable and customary in the industry, right? Not to mention creating a reason for ppl to be afraid to buy trailers....Not in their best interest.....

And, I was almost never on the side that was arguing to pin responsibility on someone else.  I was one of those dang insurance lawyers who always said "NO" not a dime in tribute and my client is not responsible for its failures; you are as an unformed consumer.  Caveat emptor.   Like the sporting ladies of the night, I was paid by the hour, just like expert witnesses.  

This is what you call thread drift.   

I posted.. then deleted.. LA, you're a few years ahead of me, yet decades apart on thoughts of life or how to live it... 

Consider this another DRIFT and hopefully the last there of.. 

No, decades apart may not adequately describe how we may differ about "life" and "how to live it."  I think perhaps galaxies may be more apt.  But since we are consigned to co-exist on the same planet, at least for the foreseeable future, I ask, as did Rodney King, can't we just all get along?  Don't worry about a little drift, it happens all the time.  Or, as the song Bobby McFerrin sang:  Don't worry, be happy.   http://www.youtube.com/watch?v=d-diB65scQU - https://www.youtube.com/watch?v=d-diB65scQU

I made this weight and balance for my 180 using hypothetical weights based on the door sticker.  I did measure the arms so they are pretty good for a 180.

Get some actual weights for your 180 and plug them in to the form.  Remember, Weight X Arm = Moment.

Originally posted by offgrid Another pilot for sure! Now ya need to provide the math to convert the calculated cg to percent tongue weight😜.

Okay, check my math to be sure I have it correct.

Distance from wheels to hitch is 13.3 ft.  Loaded CG is 11.7 ft. from hitch.

11.7 divided by 13.3 equals .88.

Loaded weight is 3314.

.88 X 3314 = 2916 pounds on the wheels.

3314 minus 2916 = 398 pounds on the hitch.

I think I should redo the form to make the datum the center of the hitch ball instead of one foot in front.  The result will be the same but the math will be easier.  Then convince my wife (Computer expert) to put it in an Xcel spread sheet.

There are three kinds of pilots.  Those that are good at math and those that aren't

Here's a revised Rpod 180 weight and balance form.  Changes the datum to center of hitch ball.  Makes the math easier and easier to measure other Arms you will add.  ie. storage compartments, kitchen cupboards, closet, etc...  anyone care to check my math and review for correctness of method?  Thoughts?

Next step would be to generate a W&B envelope for the trailer, just like we have for airplanes. On a weight vs cg graph the aft cg limit is a vertical line at 1.33 ft from the axle (10% tongue weight to limit sway risk). The max weight limit is a horizontal line at the trailer max gross weight. The min weight limit is a horizontal line at the trailer empty weight. The forward cg limit is a vertical line at 2 ft (15% tongue weight, the normally accepted max for trailers). This vertical line will extend vertically from the empty weight line until the tongue weight reaches your TV max hitch weight, then slopes upward maintaining that weight until it connects to the max trailer weight line. 

Surprise! The trailer W&B envelope looks just like one for an airplane! Maybe rather than coding this in Excel we could use one of the W&B tools out there that the EAA folks use. 

Then all we'll need is for lostagain to write an ironclad disclaimer for us to protect us from litigation.  Maybe he would even consider doing that pro bono for us poor rPod owners. 

There are three kinds of pilots. Hee hee 

  

Offgrid,

Good point about moving the datum to the axel.  Would it be the Wheeis with the torsion suspension? I made a CG envelope graph for my experimental airplane. It took a lot of head scratching to do that.  I'll have to think about it some for the Rpod.

Lostman,

The chicken and steak would probably be good enough liability protection.  I actually don't think the average camp trailer owner would be inclined to use a weight and balance form.  I'm tinkering with it mostly for my own amusement.  I think it is probably just a complicated way of doing something that is actually pretty simple.

It has given me a good understanding of how weight in various locations in the trailer affects the hitch weight and weight on the axel though.

Only the goddess of electronic aparatus will lower herself to accept lesser sacrifices.  .... Grade A eggs.

OG, out in the civilized part of the country, we have local meat suppliers and even Costco has a great selection, but it's getting a little pricey for my Social Security budget.  But, worst comes to worst, I can sneak off and poach a horse from our local wild herds or from Elon Musk's Tesla estate.

Some of my poor itinerant Irish potato farmer ancestors got into a little trouble for poaching on the absentee English landlord's estate.  Hanging or transportation were the usual punishments, but it was the only way to get a little meat to go with the praties.   http://www.youtube.com/watch?v=1sTZ6sROY38 - https://www.youtube.com/watch?v=1sTZ6sROY38

I owned a 1/3 share in a Piper Cherokee 180.  I learned to fly in it.  Then built a kitfox and flew it for 7 years.  Then there came the day when it was time to quit.  It was three years ago.  I got old and was not as sharp as I should be.  I sold the kitfox to a retired FAA inspector and commercial pilot from Alaska.  I miss it a lot.  But I am lucky to have lots of interests so bought an R-pod.

I wound up with a tongue weight of 14% outbound (FWT full, gray empty) and 11% inbound (gray tank full, FWT empty). I'm happy with that. Trailer weight is around 3650 and doesn't change much. I use a wdh which adds about 90 lbs to the trailer axle, putting it at about 3350 inbound.  I installed axle reinforcement and bumped up to 15 inch LRD tires and 2450 lb rated wheels. 

Finished my Spreadsheet for Wt and Bal.  I'll upload it if I can figure out how.  PM me and I'll e-mail you a copy.  This is messy, but you can see it.  

Weight and Balance – 2016 R-Pod 180
*Basic Weight		3122	Lbs		Tongue Wt	442	Lbs
Item		Weight		Moment Arm		Moment
# Basic Moment	=	442	*	13.4	=	5923	Ft-lbs
*Batt/Rack (47 lb)	=		*	10.3	=	0
*LP Tank (38 Lb)	=		*	10.7	=	0
*Water Htr (50 Lb)	=		*	8.7	=	0
Fresh Water (30g/250lb)	=		*	5.6	=	0
Gray Water (30g/250lb)	=		*	-1.9	=	0
Black Water (30g/250lb)	=	250	*	-5.5	=	-1375
Wardrobe	=		*	-4.5	=	0
Rt Storage Cabs (Ctr)	=		*	1.4	=	0
Fridge	=		*	3.3	=	0
Shower	=		*	-3.3	=	0
Rear Wall	=		*	-7.0	=	0
Center of Bed	=		*	7.6	=	0
?	=		*		=	0
Total Weight	=	3372		Total Moment	=	4548	Ft-lbs
Tongue Weight	=	Total Moment	/	13.4	=	339	Lbs
NB: All weight in pounds, all dimensions in feet.
* Included in Basic Weight & Moment
# Center of wheel 0.6 feet behind “axle”/Suspension mount

Colt,

Your form looks very professional.  I measured the same items with close to the same results

I built a CG Range and weight graph .  I used inches because the fore and aft limits are only 1 foot apart.  All weights from12 inches to 24 inches keep the hitch weight between 9 percent and 15 percent of the hitch weight.  Past 24 inches no weight from empty to maximum load has a hitch weight between the limits.

When I bought my hitch, I wasn't thinking I'd ever really pull max load, and I bought a Curt because I know they fit without fuss.  So, this Curt is rated at 3500 lbs trailer and 525 lbs hitch weight.  There is a higher rated one, now, but not 3 years ago.  That's makes my concerns trailer and tongue weight.  Not too much, not too little.  And not too close to the limits, not knowing Curt's F.S.  I created it in Calc/Excel so it might run on my phone. 

The exercise was good.  I discovered there is not much way to get out of balance with normal loads in normal places.  Even a 100 pound generator in the bathroom is fine, unless the black tank is full and then you put it beside the fridge and Bob's your Uncle!  Fifty pounds of food and 50 pounds of clothes, no worries; put them anywhere.      

tcj, one question. I see the lower left section of your w&b envelope sloping up and to the left. What is causing that limitation?

Also, I wouldn't suggest going as low as 9% on tongue weight on an rPod. There have been sway events on trailers loaded in that range. I did an informal survey and a post on that on this forum a couple of years back. I would recommend at least 10%, personally my minimum is 11%. Sway is scary 

OTOH, I think the 15% max tongue weight limitation is arbitrary. If your TV can easily handle more then what's the issue? 

Offgrid,

The sloping line at the lower left is due to the hitch weight being too low at the lower total weights unless  the CG is moved forward.  At 3100 pounds the hitch weight doesn't get to 9% until the CG is moved forward to 14 inches.  At 3300 pounds hitch weight is good at a CG of 13 inches and at a total load of 3500 and above all is good with a CG of 12 inches.

Doing this exercise underscores Colt's comment about normal loads in normal places and CG is good.  I was surprised but...shouldn't have been...that the CG limit range is only 10 inches.  My Kitfox CG limits were only a 4 inch range but still easy to stay within.  I'll put the 11% hitch weight lower limit on the graph and see what that looks like.

Okay, here's the Loading graph with less than 11% loaded weight on the hitch noted as "caution area for sway"

I must be missing something. 9% hitch weight should always occur when the cg is 9% of the distance between the wheel hubs and the hitch, regardless of the trailer weight, shouldn't it?  14.4/161=.09?

Offgrid,

Your right.  The CG at +12 inches is only 7.5% of the distance from wheel hubs to hitch

I don't.  A full fresh water tank requires at least 50 lbs against the back wall to keep the tongue weight under 525 lbs, my hitch's limit. 

I bought the trailer to help me stay longer on disaster relief trips.  We have had water and power at all of the work bases, so far.  But, I enjoyed it so much the first trip, I'm looking for fun trips and state parks to visit. 

My Toyota Tacoma 4 X 4 with towing package owner's manual lists towing capacity as 6500 pounds.  It says to use a weight distribution hitch if tongue weight is over 350 pounds but, doesn't list a maximum hitch weight.

In reality the hitch weight will also be limited by what you have loaded in the back of the Taco. I like this towing calculator because it tracks loading on each axle and the combined rig and lets you dial in the wdh as well. If you set the tension on the wdh so that the load on the front axle is the same as it was with the trailer weight set to zero (actually you have to set it to 1lb or the calculator blows up) and everything is in the green then you should be good.