Boat's Center of Gravity

T

Tug

New member
Another trailer question: from doing a search of many posts i concluded that on a 22 foot C-Dory Angler the centre of gravity is just aft of the cabin door as seen in this picture. The axile of a single axile trailer should be position just below the boats center of gravity.

Axileundercenterofgravity.jpg

The question is: on a tandem trailer should the boat's center of gravity be located between the two axiles on a tandem trailer or just centered over the forward axile.
If this is the case my trailer axiles need to be moved forward on my boat. Tug

2012C-DoryDrifter.jpg
 
Measure the tongue weight and the trailer weight. Set the boat so that 7-10% of the weight is on the tongue. Wherever the boat winds up relative to the axles is where it winds up.
 
From what I have learned, the tongue weight is what is important. The tongue weight should be ~ 10% of the weight of the boat and trailer. Also, with a dual axle you want the tongue height to make the weight bear even on both axles. A tongue hitched too high will put pressure on the rear axle , and a tongue hitched too low will put too much pressure on the forward axle. Tongue weight is always a variable when loading for travel. So a good investment is a tongue scale.

You should be able to adjust and permanently set your axel(s) properly before towing the boat and trailer load , and then adjust cargo loads before each trip.
 
rogerbum":na6ajbe2 said:
Measure the tongue weight and the trailer weight. Set the boat so that 7-10% of the weight is on the tongue. Wherever the boat winds up relative to the axles is where it winds up.
Click to expand...

I agree with Roger except that you do not want the boat sitting so that the transom is aft of the bunks. You do want the bunks to support the transom so they need to be flush or just aft of the aft transom wall, (outside of the transom/hull) to provide support there. So set the boat there, then weigh the tongue weight and then adjust the axles to where you need them to get that ~10%. Also, on the tandem trailer, you do want it to travel level, so the trailer tongue and the tail end of the frame, by the license plate should be equal height above the ground. That will make for more even bearing and tire wear.

BTW, how did you come up with where the Center of Gravity was?

Harvey
SleepyC :moon
 
Harvey...i just spent some time looking over the posts but i can't find where and who posted that the center of gravity was just aft of the cabin door. If i find it again i will post it. Tug
 
I'd agree with what is posted so far, but I also think that the weight on the forward and rear axles should also be somewhat equal, not disregarded.

I'd center the weight forward enough of the center point between the front and rear axles to produce the desired tongue weight.

If the load on the front and rear axles was then greater than 10%, I'd then move the axles to correct the imbalance.

Ideally, the weight on the two axles should be equal while achieving the desired tongue weight, which can also vary somewhat with the capacity and characteristics of the tow vehicle.

My 2 cents.

Joe. :teeth :thup
 
Great information.....I think i will order one of those trailer tongue scales and than go from there, the tandem axiles on my trailer look ( to me ) to be to far back on the trailer.The bathroom scale last year is used last year ended up breaking so i may not of collected the right tongue weight. Tug
 
Tug":2em9vnbs said:
Great information.....I think i will order one of those trailer tongue scales and than go from there, the tandem axiles on my trailer look ( to me ) to be to far back on the trailer.The bathroom scale last year is used last year ended up breaking so i may not of collected the right tongue weight. Tug
Click to expand...

Or take it to a truck scales, a gravel yard or maybe the local dump/recycle yard that would let you drive on and off a couple of times. Even at $5 a trip you will save a few $$$ :wink:

Harvey
SleepyC :moon
 
Oregon has truck scales on all of its' highways at varying intervals. Usually the smaller ones are not being used and we just pull onto them if we need to. The digital readout is always on. Pretty handy. Surprised other states don't also have them. Seems like I have seen them up in washington too.
 
You don't need an expensive scale, and you can use your bathroom scale without breaking it. I don't have the information in front of me, but google it and you should be able to learn how to build a contraption that works just fine. Basically just use some 2x4's to make a fulcrum. You can easily set it up so that the actual weight on the scale is 1/4 or 1/3 of your tongue weight, which is proably less than about what many of us weigh.
;-( Then you just take that scale weight times the multiplier (3 or 4). Colby
P.s., just found a website with a diagram:
http://www.rverscorner.com/tongueweight.html
 
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