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Topic ClosedHave you weighed your 180?
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tcj View Drop Down
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Posts: 141 		Direct Link To This Post Topic: Have you weighed your 180?
    Posted: 30 May 2020 at 10:01am
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.
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Posts: 5290 		Direct Link To This Post Posted: 30 May 2020 at 9:43am
I don't know about where y'all live but I haven't seen any decent looking beef in the markets around here in a couple of months. Chicken yeah, but lately I've been getting an urge to cluck and peck at the ground so I'll pass....And bacon? I've forgotten what that tastes like. As you seem to have a direct conduit do you think lady justice might cut us some slack and let us sacrifice some canned beans during Covid? 
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lostagain View Drop Down
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Posts: 2587 		Direct Link To This Post Posted: 30 May 2020 at 9:28am
The only thing that can protect you from litigation is sacrificing a chicken on your back yard grill to the goddess of justice every afternoon, served with a fresh salad, veggies and corn on the cob cooked on the grill, along with very cold beer.  You can substitute a nice tri-tip, a whole salmon, or a pork tenderloin, but to work well it must be cooked to perfection.  Bacon helps too, especially wrapped around nice thick fillet mignon steaks or put onto freshly grilled hamburgers.  Tongue

  
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Posts: 5290 		Direct Link To This Post Posted: 30 May 2020 at 9:15am
The math to calculate the tongue weight percent looks correct. It should be 1-(cg to axle)/(hitch to axle). In the example its 12%. I'd suggest one more change in datum, to the axle. In an aircraft the datum is arbitrary but in a trailer the axle is always the fulcrum of the teeter totter, making it the natural choice for the datum. 

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. Big smile

There are three kinds of pilots. Hee hee Thumbs Up
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Posts: 141 		Direct Link To This Post Posted: 29 May 2020 at 8:56pm
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?
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Posts: 141 		Direct Link To This Post Posted: 29 May 2020 at 6:41pm
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'tWink
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Posts: 5290 		Direct Link To This Post Posted: 29 May 2020 at 3:46pm
Another pilot for sure! Now ya need to provide the math to convert the calculated cg to percent tongue weight😜.
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Posts: 141 		Direct Link To This Post Posted: 29 May 2020 at 10:31am
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.
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Posts: 2587 		Direct Link To This Post Posted: 28 May 2020 at 5:44pm
Just for the record, Old, I was not the one who brought up the topic of legal liability about W&B charts for trailers and lawyers.  It was our friend OG.  We just engaged in a silly series of replies to his original comment.  So lighten up a little and you'll be happier.

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.  https://www.youtube.com/watch?v=d-diB65scQU
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Posts: 1014 		Direct Link To This Post Posted: 28 May 2020 at 3:42pm
Originally posted by lostagain

I have no intention of coming out of my very enjoyable retirement.  Now I can rant and rave about other stuff, though I can't "talk" about it here.  

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.  Star 

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.. 
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