trailer question

Looking at the ‘engineering types’ post; and having gone to school for engineering and also spent more than my share of time pulling a trailer, a question came to mind…with the axle located clear to the rear of the trailer, it seems like it would ride quite rough, and track very poorly when making turns. Just about every trailer you see going down the road (bumper-hitch trailers only), the axle is located somewhere near the middle of the trailer or slightly behind the midpoint. This helps to balance out tounge weight–not important in this case, as most hitches have 500 lb tounge weight limits; helps balance the ride of the trailer; makes it easier to back up if needed–the farther back the trailer axle is from the tow vehicle, the farther the tow vehicle needs to move to turn the trailer. Granted, this is nice when you’re learning how to back up with it hooked on, but if you get into a tight situation, it’s miserable. Having the trailer axle too close to the tow vehicle presents a similar problem–the trailer reacts so quickly to tow vehicle movement that it’s just hard to back them up. Another thing to consider is, having the trailer axle that far back is going to make the trailer track far to the inside of a corner, which on a right-hand turn in tight city streets puts that trailer (and $$$$$$ of boats) bouncing over the curb. Sure, you’ve got springs under there, but it’s still a healthy bump. Does anyone know the reason/logic behind having the wheels so far back?

I would think moving the axle forward 3-4 feet might help alleviate the tounge flex problem cited in the other post, also, but I don’t know if the trailer would then flex over the axle under load? (main beam deflect opposite direction, pushing support towers apart rather than together?)

Axle placement

– Last Updated: Mar-29-04 2:16 AM EST –

Having the axle so far back is standard for boat trailers. It might have to do with the fact that they are so light it really doesn't make any difference, or maybe you need to have a fair amount of weight on the hitch to get it to track well. The rule of thumb is something like 10-15 percent of the weight on the hitch, but when the whole outfit only weighs 500 pounds, I doubt that it matters very much. Most trailers carry a lot more weight and don't need the extra length to do it, so having the axle just a little behind center can still put a lot of weight on the hitch.

Oh, and it will actually NOT ride rougher with the axle way back there. The farther *forward* the axle is, the *more* the whole trailer will rise and fall relative to the amount that the trailer wheels go up and down, and the same applies to the magnitude of the bumps. The farther back the axle, the smoother the ride. Imagine a trailer that is 20 feet long. Put the axle at the very back, and while the back of the trailer goes up and down the same amount as the wheels, the center of the trailer only goes up and down half as much as the wheels. Put the axle at the center and the center of the trailer goes up and down the same amount as the wheels, but now the back goes up and down twice as much. Anbd the farther forward you put the axle, the worse this trend becomes.

As far as maneuverability goes, you are correct that making the "wheelbase" of the trailer longer means that it will take more room to manuever, but I don't really think that matters very often, and it really only applies to the space required for wheel tracking, not the whole trailer, as described farther below. First of all, the canoe trailer in question is about the same length, and has about the same axle placement as the fishing-boat trailer I've been using for a long time. With that trailer I can do my sharpest possible U-turn and the trailer follows the car just fine. I have yet to have a problem due to the trailer wheels tracking just a little inside of where the vehicle wheels go. Same goes for backing up. If you set up the turn correctly ahead of time, you can back it around a pretty sharp corner. Any length trailer can be cocked sharper than the vehicle can turn when backing up, so it's all a matter of planning. Again, I've never had to manuever a boat trailer in such a tight place that I had to worry about how far back the axle was located. Finally, on a long trailer, moving the axle forward would create a new and difficult problem in tight spaces. The back end would swing the opposite direction that you turn. To illustrate this, imagine a school bus that has a lot of body length hanging out behind the rear axle. Park it next to a tree-lined curb, and then imagine what would happen if you had to pull sharply away from the curb to get around another vehicle parked in front of you. You'd be stuck, because the back end of the bus has to swing a few feet *past* the curb as the front end swings out into the road, and the back end would hit those trees. Same thing happens with a long trailer with an axle near center. I think if you were maneuvering in a tight spot, if there were enough room on a sharp turn to allow that rear-end swing with the axle farther forward, there would also be enough room to back the trailer and vehicle around with the axle farther back. Either way, extra room is required. It's just a matter of what part of the trailer needs the room while turning.

wow, guideboatguy…
… you sure are smart! I’m really impressed with that whole explanation.


Now I understand…
…why 99.9 percent of us carry our yaks and canoes on the roof of our vhicle.

Being a sparky, I never could undrstnd that mechanical stuff.



As posted above
the axle placement is for ride and manuverability. The shorter wheelbase would make the trailer sway much more going down the road.

How to Rid Trailer Vibration
We started with a standard utility trailer. We welded a LONG tongue onto it, then welded one by two steel vertically off the frame with one by two steel across these (looks like telephone or electric poles).

Only problem we had was that the tongue was so long that the trailer would vibrate. We ended up attaching angle iron about half way up the tongue and attaching the other ends to the front corners of the body of the trailer. This worked.

Axle placement
You see the axle so far back on various boat haulers for weight distribution. Generally speaking, transom weight for a given boat can be disproportionate to the overall weight of the boat. With kayak and canoe haulers like the guy was working on, the empty trailer will look odd while a loaded one with some boat hanging off the back will look more “normal” or make more sense as you can observe the weight distribution then.

Powerboat trailers?
I read your post and wondered WHAT TRAILER were you talking about?

Ours has the axle smack in the middle, but it is a snowmobile trailer, not a boat trailer.