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Colt 
Senior Member 
Joined: 16 Nov 2019 Online Status: Offline Posts: 383 |
 Topic: Have you weighed your 180?Posted: 28 May 2020 at 12:58pm |
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I am also both a (inactive) pilot and an engineer, thus the reason for asking about Weight and Balance. There are similarities enough and stability is the issue in both cases. Divergent oscillations being the result, and I don't want any! Having been named personally in a suit over an environmental disaster, I am motivated to at least put out the effort do do a calc to see that I'm safe, errors notwithstanding.
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John
'16 R-Pod 180 |
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 28 May 2020 at 2:55pm |
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I figured you had to be a pilot to use the terminology. It is indeed the same basic issue. You even have a weight vs cg envelope you have to stay within, just like with an aircraft. I agree with you regarding knowing where you are with this stuff, it would be hard for us to take the position on the witness stand that we didn't understand the engineering so we used the zen approach. A smart lawyer like lostagain would eat us for lunch, 'cept that he would be going after the deep pockets of FR. Berkshire, and Mr. Buffett, not us poor rPodders.
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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lostagain
Senior Member
Joined: 06 Sep 2016 Location: Quaker Hill, CT Online Status: Offline Posts: 2587 |
Posted: 28 May 2020 at 3:04pm |
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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.
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Never leave footprints behind.
Fred & Maria Kearney Sonoma 167RB Our Pod 172 2019 Ford F-150 4x4 2.7 EcoBoost |
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Olddawgsrule
Senior Member
Joined: 20 Sep 2017 Location: New Hampshire Online Status: Offline Posts: 1014 |
Posted: 28 May 2020 at 3:42pm |
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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lostagain
Senior Member
Joined: 06 Sep 2016 Location: Quaker Hill, CT Online Status: Offline Posts: 2587 |
Posted: 28 May 2020 at 5:44pm |
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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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Never leave footprints behind.
Fred & Maria Kearney Sonoma 167RB Our Pod 172 2019 Ford F-150 4x4 2.7 EcoBoost |
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tcj
Senior Member
Joined: 05 Jul 2018 Location: Central WA Online Status: Offline Posts: 141 |
Posted: 29 May 2020 at 10:31am |
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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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2018 R-pod 180 Hood River Edition
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 29 May 2020 at 3:46pm |
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Another pilot for sure! Now ya need to provide the math to convert the calculated cg to percent tongue weight😜.
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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tcj
Senior Member
Joined: 05 Jul 2018 Location: Central WA Online Status: Offline Posts: 141 |
Posted: 29 May 2020 at 6:41pm |
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
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2018 R-pod 180 Hood River Edition
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tcj
Senior Member
Joined: 05 Jul 2018 Location: Central WA Online Status: Offline Posts: 141 |
Posted: 29 May 2020 at 8:56pm |
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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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2018 R-pod 180 Hood River Edition
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 30 May 2020 at 9:15am |
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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.  There are three kinds of pilots. Hee hee  |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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Have you weighed your 180?