Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 12-30-2020, 03:36 PM   #41
Rivet Master
 
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 3,725
Mefly2,

Frontal area, by definition is a the a projection to a 2D plane the full frontal exposure so no reduction through a "shape factor" is appropriate. The frontal area of modern wide body Airstreams is about 74.75 sq. ft.

The 2020 Ford towing guide lists the towing frontal area limits for Expeditions at 60 sq. ft. and F150's also at 60 sq. ft. except for gooseneck and 5th wheel applications.

Ford is concerned about aerodynamic impacts on towing performance and stability when towing trailers near the vehicle's stated limits.

Perhaps someone can explain why we should safely ignore Ford guidance. To say the combination tows fine because it has not yet swayed in wind is not responsive to how it would perform with wind induced sway. Does it damp the sway out or go out of control? Ford has some thoughts on this matter otherwise they would set the numbers differently.

It bears repeating, the guidance offered by Ford applies when one is towing at the upper limits so you can safely make tradeoffs. If you are well under tongue and trailer weight limits, larger frontal areas be safe and stable. What this means for F150's with 9200 lb limits is while they may be great for towing a 23' Airstream, towing a 25' is on the margin and towing a 30' is very much over. In some people's mind, they may tow a 28 or 30 great and they may well until an unusual wind comes along.

I show the same specs as you do. 9,200 max trailer weight, 920 max tongue. But Airstream trailers are not inherently stable at 10% tongue weight over about 50 mph. At 12% they will be stable to about 55 mph, still not particularly good. They do much better at 15% tongue. After including the weight of the hitch, I'd be surprised to learn a 25' Airstream loaded for camping is south of 920 lb. and if it is, it is at risk for sway depending on set up and hitch performance. Mine weighs in at 1050.

I'm not implying the Expedition is marginal for 25-27' Airstreams, I don't have to because the Ford Towing Guide tells you this directly. You are correct that many people make them work, I see it a lot. Many that I talk too will admit their combinations are a bit dicey in crosswinds. But an experienced driver can limit trailer yaw motion and prevent a situation resulting in loss of control. These people might conclude the combination is stable, never realizing that if they were to let trailer yaw exceed a couple degrees the vehicle could not overcome trailer inertia and may go out of control.
BayouBiker is offline   Reply With Quote
Old 12-30-2020, 04:19 PM   #42
Rivet Master
 
mefly2's Avatar
 
2015 25' FB Eddie Bauer
2013 25' FB Eddie Bauer
2012 20' Flying Cloud
Small Town , *** Big Sky Country ***Western Montana
Join Date: Feb 2010
Posts: 2,860
Quote:
Originally Posted by BayouBiker View Post
These people might conclude the [Edpedition] combination is stable, never realizing that if they were to let trailer yaw exceed a couple degrees the vehicle could not overcome trailer inertia and may go out of control.
I would be one of those who do realize
... and additionally I would note that I have not driven a TV that would reliably address pulling the trailer back in line when the trailer inertia and yaw amount exceeded several degrees ... not with an HD 3/4 or 1T ... but perhaps with a launch catapult ! Your observation is a keen eye for the obvious for most non-professional TVs out on the road today. It would be nice if you simply could add afterburner and pull the combination back into desired course trajectory, but when the yaw gets outside of the safe envelope, many external forces come in to play ... lots of numbers again ...
At no time did I refer to any AS length other than 25-27'; the 30 length is new to your comments. Of course, shorter model TTs can be objectified as well and we all know that out of control is out of control.

the bottom line is how does it tow.

Slow down and drive under control; I would not insult all those F150 and Expedition drivers who have not yet been told that they are out of your safety envelope; nor has Ford - it is by your assessment and evaluation that the F150 / Expedition does not conform. Somehow, all those F150 and Expy owners have made their budget and vehicles work. I know that we / I have chosen our TVs with care.
__________________
2015 25' Eddie Bauer Int'l FBQ / 2023 Ford Lightning ER
2022 Ford F350 6.2 V-8; equalizer hitch + Shocker air hitch
Honda Eu3200; AIR# 44105; formerly WBCCI 2015.1
Terminal Aluminitis; 2-people w/ 3+ dogs
mefly2 is offline   Reply With Quote
Old 12-30-2020, 06:09 PM   #43
Rivet Master
 
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 3,725
Stable combinations will understeer, slip a bit laterally and bring the trailer back into alignment. More importantly, they will continue to respond to driver and computer input and allow for corrections to realign. Catapults and afterburners are not required.

Owners who read Ford's towing guides with care will note that Ford quite clearly defines the conformance limits of their vehicles and they are not shy about it. Some F150's are set up to tow 25-27' Airstreams, others not so much.
BayouBiker is offline   Reply With Quote
Old 12-30-2020, 07:07 PM   #44
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 4,631
Quote:
Originally Posted by BayouBiker View Post
Stable combinations will understeer, slip a bit laterally and bring the trailer back into alignment. More importantly, they will continue to respond to driver and computer input and allow for corrections to realign. Catapults and afterburners are not required.

Owners who read Ford's towing guides with care will note that Ford quite clearly defines the conformance limits of their vehicles and they are not shy about it. Some F150's are set up to tow 25-27' Airstreams, others not so much.
I think it is a good idea to read the towing guide with care.

Ford very clearly states that frontal area considerations (note that these are not defined as conformance limits) may impact performance. It is obvious that it takes more power to pull a bigger sail through the wind. The answer is to slow down.

It is illogical to equate these frontal area considerations to towing stability. Stability in cross winds would depend more on trailer side area and trailer length, if we wanted to get into that. But Ford, for all their “clear definitions”, doesn’t specify trailer side profiles or trailer length, either as guidance or as limits. We already know that by themselves, trailer weights are a poor indicator for predicting trailer stability so not sure why we would want to add another poor proxy to this discussion

Note that Ford has different frontal area considerations for different versions of the same tow vehicle, with the same dimensions and weight. One difference is a larger transmission cooler. Looking forward to hearing how things like transmision coolers impact towing stability, for those that promote that trailer frontal area guidance is based on trailer stability concerns
jcl is offline   Reply With Quote
Old 12-30-2020, 07:14 PM   #45
Rivet Master
 
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 3,725
Performance is certainly one consideration for aerodynamics but it is not the only one. if the frontal area is simply drag and pulling performance explain how the guidance increases to 75 sq. ft. for gooseneck and 5th wheels.

The vehicle is moving at 60-70 mph forward. crosswinds approach the vehicle and trailer from the front corner not the side.

For vehicles where the only difference is engine or transmission configuration, everything else is the same, one can safely conclude the driver, for the lower numbers only, are performance limits. The larger number may include other considerations. In the same vain when the exact same model has different frontal area limits for trailers with different stability characteristics do we conclude the transmission overheats when the trailer is on an overhung hitch but cools just fine when using a gooseneck?
BayouBiker is offline   Reply With Quote
Old 12-30-2020, 07:22 PM   #46
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 4,631
Quote:
Originally Posted by mefly2 View Post

We have moved from an F150 ... to a 3/4 diesel (Ram & GM)... (4 x 4)
and are now back to BOTH the new Silverado 1500 and a Ford Expedition... (4x4) and are happily not looking back!
Good to hear! But based on comments on this site, this is impossible. All I ever read is that if one drives a heavier duty truck one never goes back!

(Note: I returned a heavy duty Ford pickup (it was a diesel F250) to the dealer many years ago. Bought an SUV instead)
jcl is offline   Reply With Quote
Old 12-30-2020, 07:27 PM   #47
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 4,631
Quote:
Originally Posted by BayouBiker View Post
Performance is certainly one consideration for aerodynamics but it is not the only one. if the frontal area is simply drag and pulling performance explain how the guidance increases to 75 sq. ft. for gooseneck and 5th wheels.
I donít need to, because you havenít explained how adding a transmission cooler improves stability. This is simply a deflection.

If I was guessing, though, I would say that a gooseneck or fifth wheel is more closely coupled to the tow vehicle and thus is considered to present more of a single frontal area. But that is just speculation. Speculation based on considerations of how close a semi has to be coupled to the tractor to gain aero benefit, but speculation none the less.
jcl is offline   Reply With Quote
Old 12-30-2020, 07:31 PM   #48
Rivet Master
 
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 3,725
Actually if you read my response I acknowledge a frontal limits can be driven by performance considerations and stability considerations. I think you know that also.

Edit: You may want to take a course in compressible fluid dynamics before speculating too much more about airflow and slip streams. Gooseneck and 5th wheels are much more resistant to sway and oversteer and is the primary difference. Aerodynamic drag for the combinations are quite similar.
BayouBiker is offline   Reply With Quote
Old 12-30-2020, 07:32 PM   #49
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 4,631
Quote:
Originally Posted by BayouBiker View Post
In the same vein, when the exact same model has different frontal area limits for trailers with different stability characteristics do we conclude the transmission overheats when the trailer is on an overhung hitch but cools just fine when using a gooseneck?
Lots of (class 8) studies available on how to reduce drag, and thus powertrain load factors, by moving the trailer closer to the truck. Fifth wheels are closer to the truck than with an overhung hitch.
jcl is offline   Reply With Quote
Old 12-30-2020, 07:37 PM   #50
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 4,631
Quote:
Originally Posted by BayouBiker View Post
Actually if you read my response I acknowledge a frontal limits can be driven by performance considerations and stability considerations. I think you know that also.
I agree that they are driven by (longitudinal) performance considerations.

I haven’t seen any evidence that they are driven by towing stability considerations, and it is that claim that I am pushing back on.
jcl is offline   Reply With Quote
Old 12-30-2020, 07:45 PM   #51
Rivet Master
 
2017 23' Flying Cloud
Bartlett , Tennessee
Join Date: Apr 2017
Posts: 1,074
Quote:
Originally Posted by DCPAS View Post
Bobbo's logic above seems more in the ballpark, but he also used an 80% which entails more than just frontal area and so I think it is probably optimistic.
If you note, my use of 80% was an addendum to my calculations. It was purely to circumvent anyone coming back and saying "You didn't address this." My personal figures do not include the 80% factor. I stand by my figure of 61.5 sq ft., roughly.

Quote:
Originally Posted by Bobbo View Post
(Addendum: I have read that the curved frontal area of an Airstream gives about 80% of the wind resistance of a SOB trailer of the same size. I don't know if that is true, but if it is, that reduces the apparent frontal area to 49.2 sq ft.)
__________________
Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab 3.5l EcoBoost V6
2017 Flying Cloud 23FB "BobLin Along"
Bobbo is offline   Reply With Quote
Old 12-30-2020, 08:05 PM   #52
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 4,631
Quote:
Originally Posted by BayouBiker View Post
Edit: You may want to take a course in compressible fluid dynamics before speculating too much more about airflow and slip streams. Gooseneck and 5th wheels are much more resistant to sway and oversteer and is the primary difference. Aerodynamic drag for the combinations are quite similar.
I canít keep up with the edits!

Took it. Many years ago, admittedly.

You claim that frontal limits are based at least in part on towing stability. We agree that fifth wheel configurations are inherently more stable. But the two points are independent. You havenít established the linkage.

I took courses in logic as well ;-)
jcl is offline   Reply With Quote
Old 12-30-2020, 08:16 PM   #53
Rivet Master
 
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 3,725
Here are my numbers for modern 2015 and newer wide body Airstreams with ducted A/Cs

in Sq. Ft.

Body. 65.58
Roof A/C 1.46
Undercarriage and pans. 3.82
Awnings and Vents 1.95
Tires 1.94

Total 74.75

Leaving us with the reality that A Ford Expedition and 25' Airstream combination loaded for camping with a 90 lb hitch is over Ford's towing Guidance for frontal area and tongue weight.
BayouBiker is offline   Reply With Quote
Old 12-30-2020, 10:06 PM   #54
3 Rivet Member
 
JayOhBee's Avatar
 
2012 30' Flying Cloud
Milpitas , California
Join Date: Feb 2020
Posts: 104
Quote:
Originally Posted by BayouBiker View Post
Catapults and afterburners are not required.

But it does sound like fun though!
__________________
John
-----------------------------------------
2012 Flying Cloud 30RB
2015 Ram 2500 Cummins 6.7L
JayOhBee is offline   Reply With Quote
Old 12-31-2020, 08:53 AM   #55
Rivet Master
 
hampstead38's Avatar
 
1967 26' Overlander
Owings Mills , MD
Join Date: Jun 2008
Posts: 1,125
Blog Entries: 22
For some years, my "daily driver" was a 1952 Chevy pickup. One of my retirement projects is restoring our 1967 Dodge D200 Camper Special (aka "Special Ed") as a tow vehicle for our 1967 Overlander (aka "Helen Wheels.")

Our modern Nissan Titan is superior to the old Dodge. The curb weight of the Titan is about 5400 pounds; the D200 weighs in at less than 4000. There's no comparison between the old drum brakes and modern discs. I could go on, but my points are simple. A 3/4-ton (or 1-ton) isn't magic. A modern 1/2 ton like a Titan, Tundra, or F-150 is superior to a vintage 3/4-ton... and yet somehow people managed to traverse the country in the 50s, 60s and 70s towing campers without all of them ending up as a smoking wreck. Capetown to Cairo happened with old rigs pulling Airstreams.

https://expeditionportal.com/capetow...kes-on-africa/

"Driving" isn't the same as "towing." A 3/4- or 1-ton is a great solution for Airstream owners who want to tow in much the same way as they drive. Going with a 1/2-ton (or choosing to drive a vintage vehicle) safely means making some adjustments. I make those adjustments automatically because I've been hauling and towing (often with aging relics) since my youth.

To quote my grandfather, the most important part of any truck is the nut behind the wheel. My Overlander and vintage Dodge are safer sitting parked because there are 50 mph cross winds on the Hi-Line than the physics professor who wants to tow his trailer along the same route because he has a 3/4-ton truck. Technology isn't an adequate substitute for judgment, and judgment is shaped by experience. But that's not something you'll read in a Ford owner's manual.
hampstead38 is offline   Reply With Quote
Old 12-31-2020, 10:06 AM   #56
Rivet Master
 
pjshier's Avatar

 
2017 27' International
Wasilla , Alaska
Join Date: Feb 2018
Posts: 542
vintage?

...you mean like the late 50s single axle gas powered Studebaker yard tractor they made the 17 year old kid drive to fetch empty trailers from the SeaLand yard? It wouldn't pull the hat off your head except in first gear, and was dwarfed in size by the "modern" sea-going containers. I even had to take it to a work site over 100 miles away, once, because the low man on the pole can't say no. Slow, exhausting trip.

Yes - the equipment should influence the approach, and may limit performance. It was a contributing factor in my decision to over do it on the TV and hitch. But i still love to see a restored vintage set out on the road, well executed.
__________________
2017 Int'l Serenity 27FB
2020 F250 powered by converted solar
pjshier is offline   Reply With Quote
Old 01-01-2021, 11:02 AM   #57
Rivet Master
 
hampstead38's Avatar
 
1967 26' Overlander
Owings Mills , MD
Join Date: Jun 2008
Posts: 1,125
Blog Entries: 22
In first gear aka "granny gear" I could walk beside the '52 and steer. If memory serves, it had a 411 rear. Top speed was about 55 on level ground.

I don't have any quibble with someone erring on the side of caution when it comes to equipment. If someone wants to tow his or her Bambi with a Ford F-550, OK. My point is just that good equipment is not a substitute for good judgment. And to point out our Airstreaming forebears did some remarkable caravans using what we think of as "vintage" tow vehicles.
hampstead38 is offline   Reply With Quote
Old 01-01-2021, 11:07 AM   #58
Rivet Master
 
2018 25' International
Slidell , Louisiana
Join Date: Sep 2017
Posts: 3,725
A big part of good judgment is choosing good equipment (unless there is a good reason to do otherwise).
BayouBiker is offline   Reply With Quote
Old 01-01-2021, 12:24 PM   #59
1 Rivet Member
 
socalchevy's Avatar
 
Currently Looking...
Currently Looking...
Tustin , California
Join Date: Feb 2017
Posts: 11
Your in luck. The best time of the year to purchase a new truck or auto is January as this is the slowest time of the year for the dealerships. Cast a wide net and look a 1000 miles or so from your home location. There are locals where the giant truck dealerships are, and you will get to 10k off msrp with little resistance. And the lots have filled back up from the Covid shut downs.
socalchevy is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Airstream Connected... two specific questions HappyHapgood Computers, Internet & Satellite 30 09-26-2021 08:12 AM
3 Specific setup questions F350 Air Safe with Blue Ox polar911 Towing, Tow Vehicles & Hitches 4 11-22-2020 11:24 AM
Some very specific 2018 F150 TV questions denton Tow Vehicles 38 07-27-2017 06:11 PM
Very specific tow hitch question Happy Days 2005 and newer - Bambi all models 45 07-09-2016 11:05 PM
1968 Overlander Model Specific Questions Bunkroom 1965 - 1969 Overlander 26 08-26-2014 08:04 AM


Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.



All times are GMT -6. The time now is 08:46 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.