Extra Weight / Ballast on Canoe Trailer

I’m questioning the need (imagined or necessary) for extra weight on a canoe trailer that will be hauling one or two light canoes.

What I have is a 2-place galvanized steel trailer, 42" wide frame (57" wide to outside of 4.80-12 wheels) x 16’ long, weighing 180 lbs empty. The 2-leaf slipper-type springs are rated at 450lbs each. The fiberglass/kevlar canoes weigh approximately 35 lbs each and will be carried side by side. I did already try removing a leaf from each spring, but felt that, when bouncing my foot on the back of the trailer, it left things too mushy. I re-installed the leafs.

I will be doing some (although rare) interstate travel. Mostly I will be traveling twisty country roads–and always with the first two miles over VERY bumpy roads (thank you, West Virginia Department of Highways.)

I am concerned about road bounce over bumpy roads and stability on Interstates with big trucks breezing by.

Do I need to be carrying some extra weight? If so, how much? Should I carry it across the frame or lengthwise down the middle? Forward or behind the axle? Present possible options include a 55-inch section of rail train track weighing 140 lbs or an old truck tire and rim weighing 55 lbs.



If your frame is a square tubular …
… and the rear end of the tubes are open or have pop off caps … you can push concrete inside the tubes , mix slightly stiff . Cap end when done . If you block off a drain hole , just drill new ones ahead of concrete .

Premix bags are 50 and 80 lbs. sizes . The 80 lb. bag mixes to 2/3 cu./ft. , if I remember correctly , but it’s stated on bags in any case .

Whatever you add on the frame , just be sure it will stay there and hasn’t any chance of coming off !!

Take a test run or two
adding weight will affect your mileage. If your trailer can be used to haul other things, do you really want to have it permanently loaded with concrete. You could always put some cement blocks in your trailer if you have to add weight provided you have some sort of a bed in it.

Maybe find some lighter springs
It sounds like you have “too much trailer” for the job. Perhaps you can find some lighter springs at a place like Northern Tool. You might even want to try it with just one leaf in each spring. You say it felt mushy that way, but that might be just the ticket.

If you add weight, I wouldn’t place concrete inside a tubular frame (assuming that’s even an option). For one thing, with a 3x3-inch square frame, you’d need to fill more than 16 lineal feet of frame to gain a mere 140 pounds or so (probably even less when using a flowable mix that would be able to fill such a space). This would be a lot of work, and it would prevent you from doing any drilling, welding, or cutting on the frame at a later time for repairs or modifications, and unless you live in a very dry environment it would also create a serious rust problem in the long run. Is this a box trailer with plenty of room inside? Maybe get some large cloth bags and fill them with sand or whatever soil is readily available. Any good water-softener shop will have 100-pound bags of filter sand in stock, and you might be able to get empty bags from them, or even just buy full bags and be done with it. Sand bags won’t bounce around as badly as solid objects will. I’d put the weight slightly forward of the axle. I don’t understand how it works, but apparantly you need to increase the load on the trailer tongue when you increase the total load to maintain good tracking.

Adding weight will reduce gas mileage, but if 200 pounds turns out to be enough weight to help, that’s like carrying an extra guy in the car - not too big of a deal.

When I had removed one leaf from each spring (which left just one remaining) it did not seem to respond very well to a little weight from my foot on the rear of the frame. Without much pressing down, the spring seemed to bottom out. It seemed to me that, if I left it like that, one very hard bump might cause something to break.

I’m not much inclined to fill any part of the frame with concrete—that sounds like an invitation to corrosion… and quite irreversible.

The thought of a four foot section of railroad rail getting loose and flying down the interstate, has made me think very conservatively about attempting to bolt on anything of such a dense nature. I’m thinking that I would want the minimum amount of extra weight that would do the trick. The old tire / rim seems like an easy thing to try at first. If that does the trick, I would probably want to get someone to cut the rail in half and mount that—in order to maintain a tidy appearance.

Or… I could mount the two pieces of rail on either side of the frame and then go looking for a very short locomotive to have some fun with.


Whatever weight I choose, it will easily fit in a centered position just forward of the axle.

tire PSI
I have a trailer I built that is even lighter than yours. It hauls a single sea kayak.

Air your tires down as much as you can without them being too soft. All you need is enough air to prevent the tire from breaking its seal on the rim. I have run alot of interstate miles with this trailer and it does just fine. If anyone says running low air PSI will cause the tire to overheat. That only applies to tires hauling weight close to their limit. The more weight the more air you need, less weight less air.

Just try it and see what you think.

Road bounce
Put shocks on the trailer to dampen the bounce. You might want to go back to one spring. Two #35 canoes won’t weigh as much as the force you can push with your leg. Don’t get to low with the air pressure.

Simply adding mass will decrease the bouncing frequency, but won’t help damp out oscillations once they start. Adding damping(shock absorbers)would be a better approach. The spring rate and damping rate should both match the load for the best results – just ask any serious motorcyclist.

The problem is that finding the right shocks and mounting hardware isn’t easy.

I don’t know why small trailers don’t come with shocks, or at least offer them as an option. Nobody likes having their stuff bounce around.

why? - too expensive
There is a good reason why specific kayak trailers are quite expensive - both suspension and shocks cost money.

Lighter springs help a whole bunch

– Last Updated: Sep-30-08 7:57 PM EST –

It's true that either loading up the springs or using lighter springs doesn't "stop" road bounce, but it does accomplish the most important thing, and that's to reduce the "impact" of those bounces. I took one leaf out of each spring pack for my little motorboat trailer (reduced the number of leaves from three to two), and the improvement in the ride was absolutely incredible, both in terms of "shock" and "size" of the bounces. Oh yeah, reducing the tire pressure so the tire flexes about the same amount under the actual load as it would under full load at the "recommended" pressure helps immensely too.

Not that much

Another option…
maybe I’m as clueless as I suspect, but wouldn’t increasing the padding, where boat meets trailer, accomplish what you want?

Yup, still the trailer will bounce, but the boat will have a thicker, more forgiving surface to meet with each shock.

That’s the way I went, but I also hedge my bet be putting the expensive boats on the roof, and the plastic on the trailer.


You are on the right track
The goal is to have the springs compress when you hit a bump instead of having the trailer bounce, and either of your options will work - adding weigtht to pre-load springs that are too stiff or taking out a leaf. Personally, If one leaf is not enough and two is too stiff, see if you can find a thinner leaf spring.

Rubber torsion suspension
is effective. Also available from Northern Tool. But…an expensive upgrade to retrofit. It would require welding as well. The next trailer I build will have it. I also reduce the tire pressure to reduce bounce when my home made utility trailer is lightly loaded. It helps.

the “solution”

– Last Updated: Oct-05-08 4:44 PM EST –

Here's what I wound up doing:

Since it seemed to me that two leafs per spring were too stiff... and one leaf per spring was too soft... I figured that what I needed was something like a leaf and a quarter.

So... I took the 2nd leaf and cut off some from each end---basically just making it into a 6" leaf (with the hole in the center.) That left me just enough room to re-install the rebound clip (the clip which holds the two leafs together at the front.)

This arrangement is just ever so slightly beefier than the single leaf by itself. With just one leaf, I was concerned about axle u-bolts putting such a sharp strain in one concentrated place. The very short 2nd leaf seems to spread the strain to a 6" length of the main leaf.

With a 70 pound load on the crossbars, the trailer seems just about right to me. I have 60 pounds of air in the tires--which is exactly what the manufacturer of these ST type tires recommends.

Cutting springs is a lot of fun... the best I could do was a 4-1/2" wheel grinder with a narrow kerf abrasive wheel. A power band saw would have been lots better.

Dave Curtis is completing two glass/kevlar canoes for me. I now feel like I have a trailer that is not going to destroy them on the way home.