Trailering - sway. The tail wags the dog

[busterblue]

Just pulled my boat for the winter and pulled it on the trailer for the first time. The trailer and boat are new to me. The boat is a 1989 Sailfish 252g (spec 4300lbs) with win zuke 175's (1200lbs) on a Magic tilt 25' dual axle trailer rated to 7200lbs. I rented a 2008 Sierra 1500 to tow it and could not break past 40mph without the sway starting. If I did not bring it down to 35mph the sway built to dangerous.

My qusetion is this: Is it the truck the trailer or both? I am considering getting a new truck in December (F150?)so I could trailer the boat but if I need a new trailer too then I'll probably trade down from my current SUV rather than up.

 

[Curmudgeon]

Most likely your trailer tongue weight is way out of whack. Conventional recommendation is somewhere in the vicinity of 7-10% of total weight. I'd make that adjustment before deciding on a new truck or trailer. The truck probably isn't the problem, and the "new" trailer will act the same way if not properly loaded ... :wink:

 

[gw204]

He's right. Too little tongue weight is probably the no. 1 cause of trailer sway.

 

[TBone]

Ya, check the tongue weight, I forgot exactly what the % is too, but call local RV dealer and they will walk you through it(how to measure). If you need to adjust it, you will have to see if your tandem dolly is adjustable.

On that note, one guy I new had a Sea Ray weekender will the same problem of sway, but could not get rid of it by adjusting the tongue weight.

He ended up putting one of those anti-sway stabilizer displacement hitches on it, like the ones used for towing RV trailers.

He said after that it towed like a dream.

I have a triple axle under my sail fish, no sway any highway speed.

As far as the truck, if it is more than local towing to the ramp, i.e., high way, I would go up to the 2500 series with the DURAMAX diesel and the Allison tranny, I used that and a 2008 Tahoe.

Both towed it, but the Duramax seemed like it used a lot less effort, and that tranny with the braking system was awsome.

 

[catch22]

It might be both.

I've experienced both. Had a 24' Offshore, with too light of a tongue weight. Exactly as you described, anything over 40 mph and it would sway badly. The faster you went, the more violent it would sway. I couldn't adjust the boat, (transom was right at the end of the rollers) so I moved the axles back about 5 inch's and it was fine... smooth at 65 mph.

I also trailered a set up, that I know was ok with other heavier vehicles, but when I tried pulling it with an under-rated vehicle it would shimmy and sway, (almost the same as the Offshore did). Again, right around 40 mph.

I would try trailering your Sailfish with a heavier, (2500) vehicle first. If it still acts funny, then I'd take a look at the tongue weight.

Also, I think that trailer you have, (if it's rated at 7200 gvw) is a little light for a Sailfish. I think you need something around 8000 - 9000 gvw.

 

[Grog]

If the trailer has a capacity of #7200, you're close to the max. For a seasonal tow it's not that bad but for weekend use, be careful. I pull my Sailfish with a Suburban (1500 but has the 4.10 gears). There's no issues towing but only do it twice a year. If I did it more I'd step up to a 2500/250 HD.

 

[busterblue]

Thanks, and....

The GVW of the trailer is 8090.

The axles are mounted to welded brackets so moving them would be a professional's job.

I moved the rollers and winch bar prior to use and the rollers now come to the transom. However, when I was setting up the trailer to fit my boat I flipped (front to back) the last roller bars (port and stbd) so it would extend farther back - the bar is divided 1/3 -2/3, it has 2 pair of rollers at one end and 6 pr at the other . I could flip it back and move the winch post forward to bring the wieght forward on the trailer. When I was setting it up I was afraid of having too much tongue wgt.

Thoughts?

My towing range - if I get it to tow properly, would be maxed at 30-40 miles; for you locals that's: wareham, sandwich, padanaram, plymouth.

thanks . BB

 

[journeyman]

The height of the hitch ball had a lot to do my sway issues and was the easiest thing to adjust. The trailer manufacturer will have recommendations as to hitch height to make the trailer level and once I fell in the 'Window' by increasing the drop, I can now safely cruise at 60. Truck is a 2500 HD Silverado and sits quite high so I had to look for a ball mount with a pretty good drop. I suppose hitch height and tongue weight are closely related.

Having a trailer sway on you can be reeeeeel scary :shock:

 

[busterblue]

scary indeed

I used a 2" drop because that looked level to me. I suppose increasing the drop would increase the tongue wgt but at the cost of putting more of the load on the front axle.

As these things go the sway started as I reached the junction of 2 highways and a local access ramp; there were vehicles coming at me from all directions :shock: ............they all backed off rather quickly :lol:

 

[Capt Bill]

Also, just to state the obvious; if your trailer tires are under-inflated, it will also fish-tail. Make sure that they are inflated properly for the load; probably to the max inflation pressure on the tire sidewall.

Also, as the others have already mentioned, your tongue weight is probably too low.

 

[rorkin]

Re: scary indeed

I used a 2" drop because that looked level to me. I suppose increasing the drop would increase the tongue wgt but at the cost of putting more of the load on the front axle.

As these things go the sway started as I reached the junction of 2 highways and a local access ramp; there were vehicles coming at me from all directions :shock: ............they all backed off rather quickly :lol:

Just went throiugh this with mine.. Get that tongue weight right..
Fooling around with ball height is not the answer..
You want the trailer level when hooked to truck

 

[journeyman]

Just went throiugh this with mine.. Get that tongue weight right..
Fooling around with ball height is not the answer..
You want the trailer level when hooked to truck

Ball height should be the first thing looked at! By the way, how do you get the trailer level without thinking about the height of your hitch? :roll: You're fighting a losing battle if all you are concerned with is tongue weight and you're dragging the ass end of the boat down the highway. If you are within manufacturers recommendations with a reasonably level trailer, then adjust boat and/or load to achieve desired tongue weight.

For me, all issues were resolved with a -4" adjustment.

 

[Curmudgeon]

Do what you have to do to get the trailer level, then get the trailer weighed before shifting or flipping stuff. A truck stop should be able to get you axle and tongue weights. Once you know what you have you can make an educated guess what to move and what direction to move it, or whether or not to just say 'screw it' and get a new trailer ... :wink:

 

[busterblue]

level

it was level on the hitch with a 2" drop. Has to be one of the other "cures".
Thank you all for your inputs.

 

[rorkin]

Just went throiugh this with mine.. Get that tongue weight right..
Fooling around with ball height is not the answer..
You want the trailer level when hooked to truck

Ball height should be the first thing looked at! By the way, how do you get the trailer level without thinking about the height of your hitch? :roll: You're fighting a losing battle if all you are concerned with is tongue weight and you're dragging the A** end of the boat down the highway. If you are within manufacturers recommendations with a reasonably level trailer, then adjust boat and/or load to achieve desired tongue weight.

For me, all issues were resolved with a -4" adjustment.

The tongue weight is independant of hitch height.. The Tongue weight is a
function only of the weight that is forward of the axles .

EVERY manufacturer will tell you to have the trailer level.. If your hitch is too high then of course a 4 inch drop will help.
One of the major danger points is to have the ball too high with the result of the as** being down.. The proper approach is get the tongue weight right then get ball drop or rise appropriate to get the trailer level when you hook up. If you do the reverse, if you shift tongue weight forward, then the rear of your tow vehicle will drop. You may have ended up there
by a reverse process, but that is not the way to do it.
There are many online articles explaining how to use a bathroom scale to
get the tongue weight.. Also available is a Sherline tongue scale if anyone wants to spend the $125

See below if you don't believe me

http://www.venturetrailers.com/images/sup-weight.gif
also towing guide at this link
http://www.sherline.com/lmbook.htm

 

[journeyman]

The tongue weight is independant of hitch height.

I'm sorry, but the more I read on the subject the more I disagree. The height of the hitch significantly changes tongue weight (I've read as much as 100 pounds per inch of ball height depending on total trailer weight).

I'll conceed that if you adjust the tongue weight with the hitch at the height you'll be towing your trailer then that's Ok. But I've seen people hitch their trailer up and watched the rear end of the vehicle sag 8 or 10 inches from the weight thinking all was good.

My truck springs barely move when dropping my trailer on so last year, when I moved up 5 feet and realized I needed hitch tuning, my first order of business was getting the proper ball mount. It wasn't done in the reverse order.

 

[rorkin]

The tongue weight is independant of hitch height.

I'm sorry, but the more I read on the subject the more I disagree. The height of the hitch significantly changes tongue weight (I've read as much as 100 pounds per inch of ball height depending on total trailer weight).

I'll conceed that if you adjust the tongue weight with the hitch at the height you'll be towing your trailer then that's Ok. But I've seen people hitch their trailer up and watched the rear end of the vehicle sag 8 or 10 inches from the weight thinking all was good.

My truck springs barely move when dropping my trailer on so last year, when I moved up 5 feet and realized I needed hitch tuning, my first order of business was getting the proper ball mount. It wasn't done in the reverse order.

Not what those articles say.... Your truck springs are sufficient for the load
(tongue weight) that is why the truck does not dip.
Call a trailer manufacturer and ask them about the relationship of tongue weight to ball height as well as the proper angle of the trailer
The ball should be adjusted to have a level trailer when attached..With the proper tongue weight established by position of rear axles and the position of the boat on the trailer
Tongue weight is ONLY about how weight on the trailer is distributed between
axle and ball..Tongue weight does not change due to ball height.. The trailering characteristics do. That has to do with the bounce initiated if the trailer is not level. If the truck sags alot then the spring/shock combination is too light for the tongue weight.
Think about the problem like a lever.. That is what it is..
Does the force required to move a lever change as you lift on the lever ??
I don't think so.. The force remains the same throughout the motion.
Tongue weight is the force the lever (weight of boat ) exerts on the ball
with the axle being the fulcrum.
What you have read is probably about the increase in weight on the ball
when the truck is bouncing at speed if the ball height results in an unlevel trailer. This adds an extreme shock loading that you don't want.
I am not suggesting you change anything on your set up.. It works for you. I could be wrong but that i how it looks to me and what I have been told by trailer Mfgrs
I am done .. If what you have works for you I am certainly not suggesting changing it. Happy motoring







I

 

[ahill]

Tounge weight is critical, next is what is the load distribution of items in the boat. If tounge weight is measured with the boat dry, it will change when the boat is loaded. Next check tire pressure. Sway bars defeat the hydraulic braking system.

 

[journeyman]

Think about the problem like a lever.. That is what it is..

A boat is not a simple lever. It has mass! When you change the height of the tongue on the trailer, the weight distributed over its axis changes. Think about a half-filled fuel tank! Mine sits just about over the axles. A hundred gallons could be either weighing down the bow or stern. Fill her up and everything changes! Hundreds of pounds shifting from front to rear depending on the height of the mount. And it will also shift in transit. So getting the right height from the start is rule one!

Everyone's rig is different and all problems are not solved by one simple answer. That's why we love this site and all who participate :wink:

 

[catch22]

Re: Thanks, and....

when I was setting up the trailer to fit my boat I flipped (front to back) the last roller bars (port and stbd) so it would extend farther back

Thoughts?

I think there's a real good chance that's the problem, but to be sure, check out a truck scale.

I think something like this would work;

Take 3 readings, (weights).

A - Tow vehicle and trailer together, (grand total) lets say 10,000.
B - Just the tow vehicle, (remove trailer) say 3000.
C - Back the tailer onto scale, (axles only) say 6000.

A (10,000) minus B + C (9000) = 1000 tongue weight.

I used round numbers to keep it simple, so that's a high result. I think 7 to 10% is a pretty good average for tongue weight, so a gross trailer of say 8000 should be 560 to 800.

Another method would be;

Unhitch trailer on the scale, (axles and jack stand) and take a reading. Hitch up and weigh just the trailer axles, (like above). The difference would be tongue weight.

I don't think weighing just the jack stand will give you an accurate idea of tongue weight, especially if it's 4 or 5 feet away from the coupler. The further away from the coupler, (toward the axles) the higher the weight.