Porpoising is out of control!!

[lone_star_dsl]

With our first trip coming up next weekend, I have been towing the trailer from the storage yard to my house a couple of times a week.  Total round trip is about 5 miles.

When I first picked up the trailer, it porpoised pretty bad but I figured by the time we got supplies in it, the trailer would tow a little better.  Well, we have it loaded up with the exception of food and luggage and the trailer is porpoising as bad as ever.

I did a few experiments over the week.  I was trying to move weight around to get more tongue weight.  The black and grey tanks are empty, the fresh tank (under sofa up front) is full, the storage under the front queen bed is packed to the gills with the easy-up, tools, canned goods and bottled water.

It still seems like I need another couple hundred pounds of tongue weight.

Given the way the trailer tows right now, I am dreading our 2,400 mile round trip to California later this summer.

My weight distribution hitch seems appropriately set-up given the research that I have done.  Without going to the scales, it's hard to tell just how much weight I'm distributing throughout the truck given that I have a one ton rear suspension and my front suspension has been upgraded to handle my snow plow.

Is the porpoising just "the way it is" with travel trailers?  Would airbags on the truck calm the suspension cycling down?  Do I need to invest big bucks in a Hensley?  I own a few gooseneck equipment trailers and it's been YEARS since I have towed a bumper pull.

In theory, I think my trailer axles need to be another 2-3 feet further back.

 

[Lowell]

Is the porpoising just "the way it is" with travel trailers? 

No, this is not "the way it is with Travel trailers".  Something is not set up correctly.  I have never had this experience towing my TT.  Hopefully,someone here can offer some help.

 

[Gary RV_Wizard]

You need to get to the scales. Lack of tongue weight is the most common cause for TT porpoising. Moving the axle back a foot or so will greatly increase tongue weight, but should not be necessary.

Are you sure your WD hitch is set up right? You need a full load on the trailer to tune that in.

 

[tvman44]

How does the TT sit when hooked up?  It should be level or the front just slightly lower than the rear.  You also need enough tongue weight as you already know.  Either will cuse towing problems.

 

[lone_star_dsl]

How does the TT sit when hooked up?  It should be level or the front just slightly lower than the rear.  You also need enough tongue weight as you already know.  Either will cuse towing problems.

With the trailer hooked and loaded, the trailer sits slightly nose down (1/2" over 30') and the truck has a 1/2" rake to the front. 

Perhaps I should drop the hitch down a hole and bring the front of the trailer down a little more.

 

[denmarc]

TT sounds tail heavy to me.  Gary RV Roamer is right...get that puppy to a scale.  More specifics are needed to solve this problem.
This rig needs some TLC to figure out why she doesn't want to pull straight.  How about some specific info on the towing vehicle and the TT?  It might help.

 

[Terier]

What is porpoising?

 

[wgb1]

You've seen how a porpoise (dolphin) swims as comes up out of the water and then down under as it is traveling in a straight line. That is porpoising. I guess another way to look at it is kinda like fishtailing but up and down instead of side to side. Porpoising is the vertical form of fishtailing............I guess you could say. 

 

[lone_star_dsl]

TT sounds tail heavy to me.  Gary RV Roamer is right...get that puppy to a scale.  More specifics are needed to solve this problem.
This rig needs some TLC to figure out why she doesn't want to pull straight.  How about some specific info on the towing vehicle and the TT?  It might help.

Tow vehicle is a 2002 F-350 crew cab, long bed, single rear wheel, diesel.  About 8,400 lbs before I hook onto the trailer.  Trailer is a 1997 Fleetwood Wilderness 29S.  GVWR of 7,400 lbs.

I initially weighed the combo when I first got it and came up with 14,000 lbs.  In all, I had about 700 lbs of tongue weight and 4,900 lbs on the trailer axles.

I'm going to adjust the hitch tomorrow to get the WD bars to point down just a little more.  Right now they are pretty close to parallel with the tongue.  Perhaps that's part of my problem.

 

[path]

Tighten up Weight dist. chains to put more weight on front end.  Or spring bars are not right size for set up (pound rating)
And you are sure hooked up your ball height to trailer is straight as possible, not like some who look like a 45 degree angle going down the road?
Did previous owner you move the axles?  Is this one stretch or road or all roads?

 

[Gary RV_Wizard]

You should have 12-15% of the trailer's actual gross weight on the tongue. I like 15 better than 12.

 

[katgold]

what does porpoising mean ???

 

[Water Dog]

what does porpoising mean ???

See posts above.

 

[lone_star_dsl]

Tighten up Weight dist. chains to put more weight on front end.  Or spring bars are not right size for set up (pound rating)
And you are sure hooked up your ball height to trailer is straight as possible, not like some who look like a 45 degree angle going down the road?
Did previous owner you move the axles?  Is this one stretch or road or all roads?

If I tighten up the chains, the bars are above parallel.  I think I need to add a few more washers to the hitch to correct this.  Right now, the truck and trailer sit almost perfectly level together.

I can guarantee that the axles have never been moved on this trailer.  There would be waaay too much fabrication involved for anyone except a professional builder.

The porpoising occurs more at speeds less than 60 mph and off the interstates.  Any rough section or bump in the road sets off the rocking motion.  I can best describe it as a wave that starts at the front axle of the truck, makes its way to the rear of the trailer and then comes back toward the front.  It does this rocking motion 2-3 times before it finally settles down.

These are the weights I got when I first picked up the trailer.  It had some supplies but was not camping ready.  I figure I have added another 250-300 lbs in front of the axles since then.

Truck Front Axle: 4,720 lbs
Truck Rear Axle: 4,380 lbs
Trailer Axles: 4,900 lbs

Total GCW of 14,000

My typical unloaded truck weight is around 8,400 lbs.

 

[SargeW]

Are you carrying water and if so how much? Depending on the location of the tank, it can greatly add or reduce trailer weight and towing manners.

 

[Water Dog]

According to your numbers, you have less than 10% of your trailer weight as hitch weight. I agree with Gary that the hitch weight should be closer to 15% which would be a little over 1000 pounds. I used to pull a 10K pound dump trailer behind my Ford diesel and if the front was lightened, it would do the same thing.

 

[lone_star_dsl]

I seem to have got it fixed.  I added another washer to the hitch to bring the spring bars down.  I took it for a 20 mile run at 65-70 mph and she rode smooth.

As a side note, I will be ordering a sway bar ASAP.  I had some crosswind which moved the trailer around a little but the passing semis put me in a couple white knuckle situations.

Thanks for the help guys.  I was hoping to get it ironed out without having to add unnecessary weight to the trailer.

 

[wgb1]

As a side note, I will be ordering a sway bar ASAP.  I had some crosswind which moved the trailer around a little but the passing semis put me in a couple white knuckle situations.

Those darn semis can do some crazy things to you. Its funny how they suck you closer to them just right before the cab gets to you and then they push you away as they pass. Got to really pay attention when one is coming up alongside you at a pretty high rate of speed.

 

[denmarc]

Careful wgb 1...

Some of us make a living driving those "darn semis".  Me for one.
In all fairness,  there are semi drivers with no patience and blow right on by.  BUT,  there are those RV'ers that are to too afraid to do 60 mph on a 70 mph Interstate.  Big problem here in Michigan.  Split speed limits have their pros and cons.

The key is to have your rig set up correctly.  Semis push alot of air going down the road.  You feel it whenever being passed by one or when a truck comes at you the other way on a two lane highway.  No one can control the direction and velocity of the wind which effects all of us.  Those of us who pull high profile vehicles need to be aware of this.  For the most part, your advice is correct.  Common courtesty, confidence, correct rig setup, and safe practices by all, add up to a safe and enjoyable journey.

 

[lone_star_dsl]

Careful wgb 1...

Some of us make a living driving those "darn semis".  Me for one.
In all fairness,  there are semi drivers with no patience and blow right on by.  BUT,  there are those RV'ers that are to too afraid to do 60 mph on a 70 mph Interstate.  Big problem here in Michigan.  Split speed limits have their pros and cons.

The key is to have your rig set up correctly.  Semis push alot of air going down the road.  You feel it whenever being passed by one or when a truck comes at you the other way on a two lane highway.  No one can control the direction and velocity of the wind which effects all of us.  Those of us who pull high profile vehicles need to be aware of this.  For the most part, your advice is correct.  Common courtesty, confidence, correct rig setup, and safe practices by all, add up to a safe and enjoyable journey.

I think he was commenting more on the vehicle itself rather than the driver of the semi.