Maximum crosswinds

Topic: Maximum crosswinds (Read 1276 times) previous topic - next topic

Maximum crosswinds

March 11, 2021, 10:34:07 am

So what's too much? I was reading of Dave and Danette driving home yesterday and got got me rethinking about driving in the wind. So there are many many variables but this is what I found on the internet. I have no clue!

At 60 mph the theoretical dynamic pressure will be 0.0639115 psi
Source What psi can be achieved from a 60mph wind | Physics Forums

So at 11' tall and 36' would be 396 sqft which means 57024 square inches times 0.0639115 would be 3644 pounds of side force at 60 mph. Like pushing a box kite. Tire load limits also came to thought in writing this also. So I have always just used the seat of my pants to determine stay or go. I do know I have drove 60 mph with a 50 mph crosswind, but prefer not too. I've also seen rigs on there side that were parked.
So what's a easy way to know it's time to wait or go? One would think there would be a chart with speeds and wind speeds to show the caution zone transition to danger zone. Yes there are many variables that need to figure into the base numbers.
Scott

Re: Maximum crosswinds

Reply #1 – March 11, 2021, 10:52:03 am

Scott, I think the worst cross winds seem to be from the front, 45° to 60° from the front line. We were coming across SD on I90 with strong cross winds to the driver's side when the slide awning started to unwind and billow up. We stopped and tied it up as best we could and pulled into a truck stop aways ahead. There were two other coaches with shredded awnings. We got ours secured better, had lunch and left driving about 50 mph.

I have added tie down points on the roof inside the ends of the slide awning and patio awning. A bungee cord from the tie down across the roller to the awning arm does the trick. I used ZipDee window awning strap hooks that got attached where there is roof framing.

We use Ventusky Ventusky - Wind, Rain and Temperature Maps to get n idea of winds on the way. We have waited for a day or two for all sorts of weather. Just no reason to hurry if you don't have to.

Re: Maximum crosswinds

Reply #2 – March 11, 2021, 10:53:42 am

Show off

Depends hw much of a hurry we are in.. Since I am still working (dont have any set hours so not sure why I am always hurrying).. If i get tired I will pull over and wait but typically I slow down to what is manageable and continue.

Re: Maximum crosswinds

Reply #3 – March 11, 2021, 11:04:12 am

When you are starting to get cramps from clenching your butt muscles, and your fingers are leaving permanent impressions in the steering wheel, it's time to pull over.

Re: Maximum crosswinds

Reply #4 – March 11, 2021, 11:06:21 am

Roger, yes that's what I'm attempting to put some numbers with. Hypothetical example 50 mph is acceptable with 60 mph crosswinds? Combined crosswind speed factor (CCSF) of 110 mph*?
Scott

Re: Maximum crosswinds

Reply #5 – March 11, 2021, 11:10:20 am

Quote from: Chuck & Jeannie – March 11, 2021, 11:04:12 am

When you are starting to get cramps from clenching your butt muscles, and your fingers are leaving permanent impressions in the steering wheel, it's time to pull over.

Ya my coach don't play that way. 50 mph crosswinds at 60 mph with effortless driver input. Slowed down last time going thru Texas on forty to show dw why I would not buy a class C as he was as you clearly described. Actually felt bad that I slowed down as I hit resume on cruise control. He had a horrible day.
Scott

Re: Maximum crosswinds

Reply #6 – March 11, 2021, 11:17:50 am

Favorite saying from my Dad's era as a semi driver: "When the pucker factor goes up the speed had better go down."

Re: Maximum crosswinds

Reply #7 – March 11, 2021, 11:22:50 am

Quote from: nitehawk – March 11, 2021, 11:17:50 am

Favorite saying from my Dad's era as a semi driver: "When the pucker factor goes up the speed had better go down."

100% agree. I think there may be a combined number. No wind 90 mph. 80 mph wind travel speed of 10 mph? Just making random numbers, not saying to drive 90
Scott

Re: Maximum crosswinds

Reply #8 – March 11, 2021, 11:26:32 am

Usually if I have to ask the question I try to talk the wife into staying put another day. Usually the wife overrules and I drive anyways.

Re: Maximum crosswinds

Reply #9 – March 11, 2021, 11:28:08 am

Where the center of gravity is also is a factor. Truck trailers are loaded to the top is why they tip over easier than we do with all the heavy weight down low. Even our storage is at the bottom. Before I retired and took one week vacations we had to travel up 395 to get to our camp area. Passed many trucks turned over on the side of the road and in the median. The gusts were the hardest to deal with as steering correction was required.

Re: Maximum crosswinds

Reply #10 – March 11, 2021, 11:39:15 am

We came across two crosswind crashes within about 5 miles in East Texas. Here is the scenario; the wind is blowing fairly hard from the right but a berm on the right is protecting the highway from the crosswind. Suddenly, the protection is gone and the crosswind hits the coach pushing it to the left. To keep from going into the left lane, the driver turns the steering wheel to the right loading the left side of the coach and over she goes. This is the worst when the winds are gusting and suddenly load the side of the coach. I had several photos but can't find them right now.

On the other hand, a huge Monaco ahead of us on the Yolo (Sacramento) Causeway blew over in high gusty crosswinds. That makes you slow down.

Pierce

Re: Maximum crosswinds

Reply #11 – March 11, 2021, 11:48:41 am

Bingo! and that is the true danger for most of us. I've had it happen coming through LaVeta pass in Colorado coming around a bend when the trees ended and a strong crosswind hit me broadsides and pushed me over the center line. That will get the pucker factor up. This type of crosswind is much more difficult and dangerous than a steady crosswind.

Re: Maximum crosswinds

Reply #12 – March 11, 2021, 12:01:46 pm

Quote from: dsd – March 11, 2021, 10:34:07 am

So what's a easy way to know it's time to wait or go? One would think there would be a chart with speeds and wind speeds to show the caution zone transition to danger zone. Yes there are many variables that need to figure into the base numbers.
Scott

If you were flying an aircraft, yes there are test limits, but in your RV you're the test pilot. Safety is a mind-set. Needing to be at your planned destination doesn't matter at the end of the day. What goes into your go-no-go decision is your judgement regarding conditions, and as I said, "I gotta be there" doesn't matter.

The only way out if the weather goes bad is to find a place to park and stay headed into the wind. We've weathered two southern hurricanes since 2015. Our game plan is to wait until the last day, look at the storm track and drive 100 miles 90 degrees to the projected storm track. We then try and park in the middle of a row of tractor trailers to ride out the winds. Visit the CB shop, eat at the restaurant, browse the goodies in the truckers 12V aisle.

One gust of wind. Engineered, professionally designed and built, thoroughly tested. One gust of wind.

https://youtu.be/vBUTJG3Hf_s

Art

Re: Maximum crosswinds

Reply #13 – March 11, 2021, 12:02:59 pm

So yes we all agree that crosswinds are bad, I knew that. Know that. So what combination is acceptable or is not. And there are many combinations. I've always used seat of the pants as to what is comfortable for me but putting numbers with it may be beneficial for everyone multiplied by any other road factors. Crainman probably understands load and wind factors better than most and also brings up center of Gravity/ roll axis which helps for a stable platform.
Scott

Re: Maximum crosswinds

Reply #14 – March 11, 2021, 12:20:22 pm

May be I should be asking what is your own personal limit, not feel numbers but actual speed and wind speed numbers to call the day off? Numbers that you can tell others? Everyone has a different happy comfortable zone to be within. I'm no longer Eligible to be the test pilot, you and many prior have built a foundation that I wish to see shared. I just wish to conform to prior knowledge. I'll adjust as seen appropriate for current conditions myself typically by slowing down more or putting off for another day.
Scott

Re: Maximum crosswinds

Reply #15 – March 11, 2021, 12:44:02 pm

Quote from: dsd – March 11, 2021, 12:20:22 pm

May be I should be asking what is your own personal limit, not feel numbers but actual speed and wind speed numbers to call the day off? Numbers that you can tell others? Everyone has a different happy comfortable zone to be within. I'm no longer Eligible to be the test pilot, you and many prior have built a foundation that I wish to see shared. I just wish to conform to prior knowledge. I'll adjust as seen appropriate for current conditions myself typically by slowing down more or putting off for another day.
Scott

Don't think it's your personal limit but rather, what kind of judgement do you have? Is it on the conservative or reckless side. I should pull off and park facing the wind or I can handle anything mother nature throws at me. As you travel down the road, it's impossible to judge the topography and how it's going to effect the direction and velocity of the wind. Being on a time line like a trucker is one thing but driving an RV with no deadline to meet is quite another thing. And it happens so fast. Once Humpty Dumpty has fallen off the wall...

Great dashcam compilation: https://www.youtube.com/watch?v=MG22JlcZnMk

Pierce

Re: Maximum crosswinds

Reply #16 – March 11, 2021, 12:44:06 pm

Quote from: dsd – March 11, 2021, 12:20:22 pm

May be I should be asking what is your own personal limit, not feel numbers but actual speed and wind speed numbers to call the day off?

What good does it do to seek "actual speed and wind speed numbers" unless you have real-time instantaneous readout of wind speed in your coach cockpit? The actual local winds can vary widely from online weather site predictions. Wind gusts well in excess of steady winds can occur at any time, anywhere. Microbursts can happen with out warning.

Depending on one single rigid Go-No-Go number might cause you unnecessary delay in one case, OR it might lead you to make a stupid move. Each driver must asses the actual weather conditions at their location, and taking into account all the many factors involved (including consulting with your crew), make the decision to either drive, or stay parked and wait it out..

Re: Maximum crosswinds

Reply #17 – March 11, 2021, 12:44:43 pm

Personally anything much over 30 mph and I am staying put. If I have to slow down to less than highway speed, it isn't worth making the drive.

Of course circumstances may dictate a different decision someday

Re: Maximum crosswinds

Reply #18 – March 11, 2021, 12:46:00 pm

Scott, it there are 40 mph winds from any direction than a pure tail wind we will think seriously about staying put. A tail wind is nice but the bow wake off oncoming traffic is worse. We went from Denver area to Moscow Iowa on I80 with a good tirail wind, got almost 12 mpg. North to home, more head wind, maybe 6.5. We weren't home more that 6 hrs and it started snowing, 11 inches.

Some think they can drive in anything (like most 4x4 drivers) until they are in the ditch.

Re: Maximum crosswinds

Reply #19 – March 11, 2021, 12:48:27 pm

If the weather app is saying 20mph winds, I assume 40mph gusts. I too am usually staying put around 30mph. A lot depends on how well rested I am that day too. If I'm already a little fried from a long week, the added stress isn't worth it and my "Go-no-go" number drops considerably.

Re: Maximum crosswinds

Reply #20 – March 11, 2021, 01:24:23 pm

I was coming east on I-80 west of Laramie the wind was blowing but that's not unusual in that area, on the CB were two truckers from the south east. They parked near the " warning high winds " sign and they were debating on how long they could stay and wait for the winds to die down. I told them they would need all the fuel in the western world if they were waiting for the wind to abate in one of the windiest places In Wyoming. Always stay up wind. Find a spot on the leeward side and hunker down think sail boat, any port in a storm.

Re: Maximum crosswinds

Reply #21 – March 11, 2021, 02:29:21 pm

I have a few stories that will wait for a camp fire.. Like said above the grove under your pants will let you know when to make or break camp.

Quote from: Olde English – March 11, 2021, 01:24:23 pm

I was coming east on I-80 west of Laramie the wind was blowing but that's not unusual in that area, on the CB were two truckers from the south east. They parked near the " warning high winds " sign and they were debating on how long they could stay and wait for the winds to die down. I told them they would need all the fuel in the western world if they were waiting for the wind to abate in one of the windiest places In Wyoming. Always stay up wind. Find a spot on the leeward side and hunker down think sail boat, any port in a storm.

Parking by the sign and waiting made me chuckle. It's like a sign was all they were waiting for.

Re: Maximum crosswinds

Reply #22 – March 11, 2021, 02:37:12 pm

Naturally, everyone always tries to take off into the wind but even with a strong crosswind, it's still not much of a trick. Max ailerons into the windy side when starting the takeoff roll, keep it straight and then lift off turning into the wind to keep a straight track.

Now imagine arriving at a destination (Mojave desert, Inyokern Airport, CA) with marginal fuel, wind howling across the runway and landing. You fought headwinds all the way so arrive having used way more fuel than expected. It's windy everywhere else so no choice and you can see the big dust devils everywhere on the ground plus it's so rough, nothing stays put in the cockpit. Now it dawns on you why they put all the huge wind generators in the hills just outside of Mojave.

Oh, for a Foretravel parked behind a building riding out the storm.

Pierce

Re: Maximum crosswinds

Reply #23 – March 11, 2021, 02:38:51 pm

Yes many unknown variables. So I with most it sound like prefer less but will accommodate gusts to 40. Hi gust warning areas as posted. All should reduce speed with opposing gusts. Lot of well experienced owners hopefully will add to this appropriately.
Thanks Scott

Re: Maximum crosswinds

Reply #24 – March 11, 2021, 03:12:29 pm

https://www.wmta.us/images/wind.jpg

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