Trailer sway - what to do and how to react?

[romandesign]

I was towing my 1989 Macgregor 26D on original trailer with surge brakes for the second time yesterday, with my VW Routan (made by Chrysler, so same as Caravan etc.). It actually tows really well, and transmission temp doesn't get gihger than normal (I monitor with Torque Pro app through blutooth ELM327 dongle) however when I tried changing lanes and had to veer back, trailer started swaying left and right. I was going about 90 km/h. I felt it a bit and seen in the mirror the oscillations. I let go of the gas ans started breaking really really gradually and it stopped, but left me thinking...

- Ho do I react properly when it happens? I reacted instinctively, but I'm not sure its' the right way.
- I used a hitch drop/riser to keep the trailer parallel to ground. It has several positions, and can also lower hitch ball. Should I lower the ball, hoping to get a bit of weight forwards?
I have this one: It has several positions in down and up orientation. So should I lower it and if yes how much?
- The actual reason I had to cancel lane change is because my left turn indicator suddenly stopped working. After I stopped to check later, even when I unplugged my DIY harness from the car, the car left turn indicators weren't working. But after I turned the car of and restarted in a minute, everything started working again. I don't know what the hull was that... I did wiring and harness myself - there are no electornics, just wires spliced from rear lamps and correctly wired to the trailer. But it doesn't seem to be a problem. Bad wiring would cause a short or loss of contact, so when unplugged it should start working, but it only did after a "reset". Trailed also worked after that...
- My mast is moved farther front when I keep the boat on my drieway (it doesn't fit otherwise). I pull it back to normal position when towing. Maybe I should tie it down well and leave it forward of the normal position, just to have more weight on the front?

[kadet]

Key things to control sway;

• Correct tongue weight
  Even distribution of weight in boat port - starboard
  Try and keep heavier items over axle,extra water fuel etc..
  Ensure tow vehicle suspension is rated for tongue weight

If sway occurs come off the gas as you did but resist braking till sway stops also don't tow over 80km/h if/until sway issues are fixed.

[kurz]

Towing higher than 85kmh I have the same problems.

So stay slow and save

[NiceAft]

Something just is not right if you have a sway like that at 85kmh.

You state that the boat is level, but is the rear bumper of the car unusually low? If so, this too can cause problems with trailer sway.

Ray

[kmclemore]

As noted, trailer sway is nearly always caused by too light a tongue weight and/or the wrong angle of the trailer. Since yours is riding level then I have to assume it's too light on the tongue. Shift the boat's movable weight forward into the V-berth (luggage, supplies, etc.) and this will likely eliminate the problem. And, as noted, slowing down by allowing the car to slow naturally is the best bet... using very light braking, as you did, also works, though if you're able to avoid it its best.

[kmclemore]

Rule of thumb is that the tongue weight should be >10% of the gross weight to prevent swaying. Most of our Macs are around 3,500 lbs. so that's a minimum of 350 lbs. at the tongue. Catigale long ago posted a way to weigh the tongue using two bathroom scales and a short, stout beam of wood, essentially spreading the load between the two scales (since not many scales will read 350+ lbs). Add the two indicated weights, subtract the weight of the beam and you have your tongue weight.

[NiceAft]

https://www.airliftcompany.com/workshop ... iler-sway/

More than one way to create conditions described.

Ray

[kurz]

Something just is not right if you have a sway like that at 85kmh

But he wrote about the speed of 90kmh.

I notice in my configuration a real big difference between 85kmh and 90kmh!!!

Of course, if you have a big truck my be different. I am talking about a car!

[NiceAft]

I cruise along at 105kmh nicely. My vehicle is a 2011 GMC Acadia. Before that, an even smaller wheelbase 2002 GMC Envoy. My point is that both too light a weight, and too much weight on the tongue can cause conditions for sway. If all is correct, then there should not bra swaying problem at the speed the original post stated.

Ray

[romandesign]

Thanks for the pointers. My trailer is pretty much level, or very close. I can play with the hitch drop/rise but not sure if it's wiser to keep it parallel, or drop the tongue to give it a bit more weight. See photo below for how it looks as of now. My tongue is definitely too light. Vehicle rear doesn't sag almost at all. I don't have any gear in the boat, and whatever is in the boat (anchor, boom, MRS pole) is all inside as close to the bow as possible. Still, the bow is too light I think. Also, it's very difficult to make the boat stick to the V on the trailer, and there is an inch or two of distance to the boat, and that with winching it 2-3 times during raking the boat out of the water. So the problem is definitely not too much weight on the tongue, it's most likely too little.

[romandesign]

Here's another pic of how it looks hitched

[NiceAft]

You mention that there is about two inches gap in the boat despite winching. Do you do the Mac bump after taking your Mac out of the water?

Rau

[romandesign]

No. What is this and how do you do that?

[kurz]

If you have single axle tongue high does not affect tongure weight.

And: Don't talk about tongue weight... just mesure it correctly!!!!! Then you know more

[romandesign]

Well, I've seen my fried lift the tongue with his bare hands, so it must be light. I can't fully lift it without risking stretching a muscle, but it feels like I almost can.