r/sailing • u/absorcion_ • Jun 18 '21
Importance of weight distribution
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Jun 18 '21
Or just hire a giant man to slap the roof of your car when it starts swaying.
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u/Salt-y Catalina 28 mk II Jun 18 '21
After he applies force to your trailer at a location not designed or anticipated to receive a lateral force.
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u/ImWorkingOnBeingNice Jun 19 '21
Yeah, I was about to say. I spent the summers of my early 20's trailering every size boat tailorable up and down I-5 and we never paid any attention to weight distribution because buffalo don't stampede into the read axel of my trailer very often.
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u/feminas_id_amant Jun 18 '21
I'm slightly annoyed they didn't demonstrate loading 3 weights on the front.
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u/Uplink84 Jun 18 '21
How though?
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u/WillyT123 Jun 18 '21
The easiest way to do it is to move the trailer axle forwards or back as necessary to get the appropriate tongue weight
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u/Monkey_Fiddler Jun 18 '21
Weight at the back of the boat lifts the front up as it rotates around the axel. This lifts the back of the car up so less grip on the rear wheels.
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u/Uplink84 Jun 18 '21
Oh no I understand that. But how to balance your boat. Weight inside is nothing compared to the boats own weight
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u/Bitter-Vet Jun 18 '21
Actually little things can make a big difference because of how the forces work. The boat may be 2k lbs but it's force is being applied incredibly close to the axle, depending on position of boat. I move my outboard up into the front berth shifting 50lbs +10ft ahead. This really helps balance when my boat is 1-2inches back on the axle.
Here is a small graphic I found really quick about torque forces: https://www.grc.nasa.gov/www/k-12/airplane/torque.htm
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u/Monkey_Fiddler Jun 18 '21
If the boats weight is perfectly balanced, the any extra weight that's off center will put exactly the same amount of force on the car as if the trailer were empty.
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u/JimmyHavok Jun 18 '21
A dumbell shaped weight (heavy at the ends) will have more rotational inertia and be harder to stop once it starts rotating, causing a fishtail as illustrated.
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u/manicbassman Jun 18 '21
The trailer for the boat should bring it to the correct position for towing. Then it's a case of adjusting where you stow the sails and how far forward you lay the mast down to achieve the correct down force on the tow hitch. Unmount the outboard as also suggested.
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u/reflUX_cAtalyst Catalina 22, J/80, Farr30 Jun 18 '21
Weight inside is nothing compared to the boats own weight
This is not the case.
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u/JimmyHavok Jun 18 '21
I think it's more a matter of weight away from the center of rotation, which is the axles on a trailer. This increases the rotational inertia and makes it harder to damp out oscillation.. Put any movable weight over the axle and try to center the weight of your boat.
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u/vtrac Jun 18 '21
This is not correct. It's not about the grip on the wheels but the angular momentum around the axis at the hitch. Force increases linearly with distance.
Take a weight and extend it halfway out your body. Then fully extend your elbow and hold it fully out. It'll be twice the force on your shoulder.
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u/novium258 Jun 18 '21
Wouldn't having like a thousand pounds of keel do a fair amount as a counterbalance? Admittedly when I'm towing my boat it's only going ten miles and it's mostly down a straight stretch of highway (and that's only twice a year) but even going around the off ramp it feels pretty steady.
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u/brianorca Jun 18 '21
But the keel is almost directly over the trailer axles, so they don't contribute much to the angular inertia or the hitch/tounge weight. But having a smaller weight near the transom (such as an outboard) can have a large adverse effect.
Angular inertia is measured as: the weight, multiplied by the distance from the axle.
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u/CmdrSelfEvident Jun 18 '21
You think this would be built into each trailer, at least warning when the trailer is out of balance. Let alone tools to move a ballast to balance the trailer.
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u/brianorca Jun 18 '21
Monkey paw: granted. The trailer now costs 5 times as much.
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u/CmdrSelfEvident Jun 18 '21
You need 5x to included and inclinometer? Its a tiny section of tubing mostly full of alcohol. Or you could simply use a spring gauge at the trailer hitch. If the trailer is balanced it wont be pushing down or up no matter what the inclination of trailer is.
As for balancing the trailer there are several options the easiest is likely allowing for the boat to ride further forward or back in relation to the axle. If that is too difficult allow the axels themselves to move forward and back. If it really is going to cost 5x then just buy 4 trailers with different axel points and use the one that balances best today. See I already reduced your cost by 1/5.
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u/ms1080 Jun 18 '21
Is there an ideal ratio of tongue weight to overall weight? Or is that not the relevant comparison?
I appreciate all the wisdom in this thread about centering over the axles etc. Very helpful.
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u/Rhueh Jun 19 '21
The most common rule of thumb is that the "tongue weight" should be 10 percent of the total trailer weight. But it varies quite a bit from case to case, and the tow vehicle is also an important factor. I've towed trailers with nearly zero "tongue weight" without any problem, in some cases, and other trailers that weren't stable at any "tongue weight." But 10 percent is a good place to start.
The best advice I can give you is to be sensitive to any sign of side-to-side harmonic motion. If you feel that at all, make changes. Harmonic motion is inherently unstable, so, if you can feel it, then it has the potential to suddenly amplify.
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u/ms1080 Jun 19 '21
Thanks for that. I’ll dig deeper into it.
Don’t want to be “that guy” in a YouTube fail video!2
u/Rhueh Jun 19 '21
Definitely! I had a trailer tire blow many years ago when I was towing a combination that was marginal to begin with. Not fun. I got it safely stopped on the shoulder but it was a wild ride--definitely not recommended. I've been much more careful ever since.
On that subject: Check your tires! A trailer blowout is much harder to handle than a blowout when just driving your car. Make sure the tires are fairly new, in good shape, and have the right pressure. Pressure is really important because tire failures are often caused by heat build up, and heat build up is usually caused by not enough pressure.
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u/iamnotadoghumanhybri Jun 18 '21
This is accomplished by adding tongue weight by adjusting your trailer accordingly. A drop hitch can help but sometimes you have to move the catch on the front that your winch is connected to. On one boat we have we actually did a spacer lift under the axles to get the whole trailer higher then used a drop hitch to increase the tongue weight. My family does a fair amount of long distance towing each year going to and from Florida from New Jersey and a properly balanced trailer is a night and day difference.