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Re: trailering [Re: Mary] #71184
04/11/06 03:29 PM
04/11/06 03:29 PM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline
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Santiago, Chile
Quote
.....He checked out the trailer and said the axle is bowed down and the wheels are canted out and the bearings on the starboard side are probably going to disintegrate soon from the stress. He advised me not to drive far. I said, "Well, I have to go another 700 miles." He said, "No way. Go to a repair place and get a new axle and replace the bearings."

I did not take his advice. Instead, I decided that the boats had slid back on the trailer because of not being tied tight enough. (Not our boats and not our trailer.)

so basically you didn´t mind risking other peoples boats, trailer and perhaps other peoples lives on the highway..

-- Have You Seen This? --
Re: trailering [Re: Mary] #71185
04/11/06 04:03 PM
04/11/06 04:03 PM
Joined: Jun 2004
Posts: 141
Panama City Beach, FL
steveh Offline
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By "stability" I meant how well it tracks behind the towing vehicle and how little it gets thrown around when big vehicles pass it.

So you are saying that this is not necessarily specifically related to the width of the axle, but is also related to the length of the trailer tongue?

I'm not an engineer, so bear with me on this. If you have a narrow axle and your trailer wheels are close together, does that mean you should have a shorter tongue. And if you have a wide axle (wheels far apart), you need a longer tongue? Or is it vice versa?

I know I have followed some trailers with very wide axles, carrying ATV's, and they seem to be all over the place. And I have followed one of our trailers with the narrow axle carrying three boats, and it seems to track very true.

So is this all a function of relative tongue length vis-a-vis axle width? (Assuming proper weight on the hitch.)


Exactly. However, you do need width to add stability if your load is higher to keep it from tipping over.

Re: trailering [Re: Andinista] #71186
04/11/06 04:18 PM
04/11/06 04:18 PM
Joined: Nov 2002
Posts: 5,558
Key Largo, FL & Put-in-Bay, OH...
Mary Offline
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Andinista,
Well, it was all in the family. My sister and her husband had bought them, and I was bringing them up to Ohio to help form our new Wave fleet. They had bought them from another friend of ours down here in Florida who had been sailing Waves with us and who is impeccable about maintaining his boats and his equipment and had been trailering his boats all over Florida with this same trailer with no problems whatsoever.

The only problem was that he does not hogtie things down as much as I do, and the boats had slid back a little bit. No big deal. It was just common sense to redistribute the load, and I'm sorry I even consulted that so-called trucker.

As far as risking the lives of other people on the highway, I don't think so. Based upon his analysis, the worst thing that could have happened was that the bearings might go on one of the trailer wheel hubs, which would have left me possibly stranded alongside the road for a while.

Have you ever heard a high singing noise when you are pulling a trailer? That's the sound of wheel bearings starting to seize up. Rick and I have experienced that twice, and both times we have ended up staying overnight in unplanned places.

Doesn't endanger others, but it's not something I wanted to experience all by myself pulling a trailer through the mountains.

Fortunately, shifting the load forward and tying it down better solved the problem. Although, I still worried about the bearings all the way north.

Re: trailering [Re: Mary] #71187
04/11/06 04:39 PM
04/11/06 04:39 PM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline
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Ok. The sentence "Instead, I decided that the boats had .." sound like the theory came out just as an easier alternative than hearing the guy's advice.

Re: trailering [Re: Andinista] #71188
04/11/06 05:15 PM
04/11/06 05:15 PM
Joined: Nov 2002
Posts: 5,558
Key Largo, FL & Put-in-Bay, OH...
Mary Offline
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Hey, I heard the advice, and I passed it on to my sister, the new owner of the boats and trailer, in case they ever want to take it anywhere off the island, which is unlikely.

Now, the interesting thing about all this is that the wheels on that particular trailer were very far apart, wide axle. It was always carrying two Waves double-stacked. And, as I mentioned, the axle was bent (bowed down a little bit), which caused the wheels to cant outwards a little bit, which caused more pressure on the wheel bearings.

SO, I am just wondering whether there is also some engineering ratio to determine where the wheels should be under the load so that it will not stress the axle. Is more in better than more out?

Re: trailering [Re: steveh] #71189
04/11/06 05:19 PM
04/11/06 05:19 PM
Joined: Jul 2005
Posts: 306
St. Louis, MO
hobienick Offline
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The tracking of the trailer has very little (if anything) to do with the stance of the wheels. It is the longer tounge that will keep it tracking behind the two vehicle. It will still blow around when a semi passes you, or you the semi, but it will not jerk the tow vehicle around as much and will recenter in a much more gentle way than a short tounged trailer will.

It's like the wheel base on a car. If you ride in an old CJ5 Jeep dow the highway, every little bump in the road will rock the jeep. If you ride in a road boat station wagon with the really long wheel base, you don't feel the bumps as much. (For those of you who will jump on me and point out suspension differences, assume they are using the same suspension).

For a more nautical reference imagine sailin a small 8' dinghy in 1' seas. Then imagine sailing a 16' dinghy in the same seas. Much smoother. Rotate the plane of motion 90 deg and you have your trailer. Instead of your contact points being the bow and stern causing pitch they are the hitch and wheels causing yaw.

I hope this cleared things up and didn't make it more complicated.


Nick

Current Boat
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Previous Boats
'84 H16
'82 H18 Magnum
'74 Pearson 30
St. Louis, MO
Re: trailering [Re: Mary] #71190
04/11/06 05:21 PM
04/11/06 05:21 PM
Joined: Jul 2005
Posts: 306
St. Louis, MO
hobienick Offline
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You needed a beefier axel. It sounds as if it was overloaded. Most small boat trailers are good for about 600 - 1000 lbs. The only way to remove the torsion you saw on the wheel bearings is to apply your load to both sides of the wheel.


Nick

Current Boat
Looking for one

Previous Boats
'84 H16
'82 H18 Magnum
'74 Pearson 30
St. Louis, MO
Re: trailering [Re: Andinista] #71191
04/11/06 05:56 PM
04/11/06 05:56 PM
Joined: Jan 2006
Posts: 11
Sacramento, Ca
acdavis Offline
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I'm pulling this out of a vehicle stability class that I took while studding Mechanical Engineering in college. It's been a few years so if I'm mistaken feel free to correct me.

From what I remember, there are three areas of stability:

Stable, under normal speeds when disturbed the trailer will always follow behind the towing vehicle and any oscillations (bumps in the road) will dissipate.

Critically stable, the vehicle will remain stable under a threshold speed and any oscillations will dissipate. Over this speed the oscillations will increase until you loose control of the vehicle (fishtail).

Unstable, at any speed any oscillations will increase and you will loose control at even the smallest speed.

Warning, if you’re not an engineering nerd you may want to skip this next paragraph:

Stability has to do with where your eigen values are located when plotted on a real vs imaginary graph. For fundamental stability the eigen value must be in the quadrent located above the real axis (x axis) and to the left of the imaginary (y axis). Critical stability occurs when any eigen value is located on the y axis and above the x axis, and fundamental unstability occurs when the eigen value is located to the right of the y axis.


When it comes to trailers this is a direct function of where the center of mass is in relation to the axel of your trailer.

If your center of mass is in front of the axel the trailer will remain stable.

If the center of mass is right at the axel, your trailer will be critically stable, over the threshold velocity it will oscillate out of control. This type of loading should be avoided because there is really no easy way to know what the threshold velocity is. Unless you like finding out the hard way.

The trailer will be unstable if the center of mass is behind the axel. This is unsafe at any speed.

I remember a demonstration we had in class where we had a bicycle with a trailer which had a 2 lb weight in it. Just putting this little amount of weight behind the axel was enough to throw someone off the bike at a walking pace.

It's super easy to know what kind of loading you have. If the tongue of the trailer is on the ground before you hitch up and take off you'll be fine, just make sure the load can’t shift. If the tongue is balanced evenly or up in the air, you're screwed.

Of course the easiest way to make a trailer unstable is to simply put your car in reverse.

I’ll put my pocket protector away now.

Adam

Re: Wheel SIZE 8" v. 12" [Re: acdavis] #71192
04/11/06 06:22 PM
04/11/06 06:22 PM
Joined: Mar 2006
Posts: 66
Fort Lauderdale, FL, USA
ReefedOne Offline
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Before you put your Mech. Eng. texts and SAE handbooks away, please re-assure the folks that 8" wheels are just fine (for single cat trailers, anyway), and will not "overheat" the bearings at speeds under 100mph. Wheel bearings must meet minimum DOT/SAE/etc. standards, which generally have LOTS of margin built-in. What makes bearings overheat is EXTREME OVERLOADING (or overtightening during installation) and (*ta-DAH*) INSUFFICIENT LUBRICATION, period. Spring loaded hubs, which maintain positive grease pressure, i.e. no air voids, thereby keeping water out, go far in this regard. So does periodic maintenance.

I've had trailers with both size wheels, and in retrospect, I like the 8" better because the boat was lower to the ground, ergo easier to launch, recover, and hop up on to step the mast.

I too worried about the THEORETICAL overspeed of the bearings with my 8" wheels, so once after driving 120 miles non-stop at 70MPH, I pulled over to the shoulder, hopped right out and felt both hubs in quick succession... air temperature. NO problemo...


Of course all of the above applies only to bearings made in the G8 industrial countries. If you buy bearings made in Red China, well, I hope you enjoy the $2.86 savings while your $20,000 A-cat gets a terminal case of road rash.

Re: trailering [Re: acdavis] #71193
04/11/06 08:05 PM
04/11/06 08:05 PM
Joined: Nov 2005
Posts: 5,582
“an island in the Pacific.â€...
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Quote
From what I remember, there are three areas of stability…
One other factor is how much fuel is in the towing vehicle’s tank. Fuel weighs 5.8 to 6.5 lbs. Ethanol is 6.59 lbs. Diesel is 7.0 to 7.3 lbs. If a vehicle has a 20 gallon tank you mat see stability change as the fuel is used.
Quote
Of course the easiest way to make a trailer unstable is to simply put your car in reverse.
When I was in the Army, I had a signal group with a bunch of M151A1 Jeeps (pre Hummer) equipped with trailers. None of the guys in the section had ever pulled a trailer before. After I finished with them they were doing figure-eight races in reverse around two warehouses. The major I worked for freaked out until I got him into a Jeep. He turned out to be a pretty good competitor.


US Sail Level 2 Instructor
US Sail Level 3 Coach
Re: trailering [Re: hobie1616] #71194
04/12/06 01:04 AM
04/12/06 01:04 AM
Joined: Jul 2001
Posts: 364
Andrew Offline
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Fuel weighs 5.8 to 6.5 lbs. Ethanol is 6.59 lbs. Diesel is 7.0 to 7.3 lbs.


Then fuel weighs 5.8 to 7.3 lbs (per gallon), right?


Andrew Tatton Nacra 20 "Wiggle Stick" #266 Nacra 18 Square #12
Re: trailering [Re: Andrew] #71195
04/12/06 08:53 AM
04/12/06 08:53 AM
Joined: Jul 2005
Posts: 306
St. Louis, MO
hobienick Offline
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Wow, this thead just got really complicated for a simple question. Let's assume for all of my previous posts the trailer was balanced correctly (weight on the tounge of the tow vehicle). With a longer distance between the hitch and the axel the trailer will track behind the tow vehicle better.

Since most of us trail with bows forward cat trailer have this "advatage" built in.

I would say that the chagne in weight of fuel in a tow vehicle is not going to make it unstable. It's not like we are flying in a small airplace with a fuel tank aft of the rear baggage compatement that when the fuel is burned completly changes the handling of the airplane.

As far as tire size goes, 8" tires will work fine. I like the larger tires because I feel better with that extra margin given by reduction in angular velocity of the bearings. I also really like the larger tire diameter for handling bumps in the road.


Nick

Current Boat
Looking for one

Previous Boats
'84 H16
'82 H18 Magnum
'74 Pearson 30
St. Louis, MO
Re: Wheel SIZE 8" v. 12" [Re: ReefedOne] #71196
04/12/06 09:03 AM
04/12/06 09:03 AM
Joined: Sep 2005
Posts: 1,187
38.912, -95.37
_flatlander_ Offline
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Quote
Before you put your Mech. Eng. texts and SAE handbooks away, please re-assure the folks that 8" wheels are just fine (for single cat trailers, anyway), and will not "overheat" the bearings at speeds under 100mph. Wheel bearings must meet minimum DOT/SAE/etc. standards, which generally have LOTS of margin built-in. What makes bearings overheat is EXTREME OVERLOADING (or overtightening during installation) and (*ta-DAH*) INSUFFICIENT LUBRICATION, period. Spring loaded hubs, which maintain positive grease pressure, i.e. no air voids, thereby keeping water out, go far in this regard. So does periodic maintenance.

I've had trailers with both size wheels, and in retrospect, I like the 8" better because the boat was lower to the ground, ergo easier to launch, recover, and hop up on to step the mast.

I too worried about the THEORETICAL overspeed of the bearings with my 8" wheels, so once after driving 120 miles non-stop at 70MPH, I pulled over to the shoulder, hopped right out and felt both hubs in quick succession... air temperature. NO problemo...


Of course all of the above applies only to bearings made in the G8 industrial countries. If you buy bearings made in Red China, well, I hope you enjoy the $2.86 savings while your $20,000 A-cat gets a terminal case of road rash.


Ditto, Amen and all that. There's a lot of real estate between lakes around here, not so breathtaking that one would want to drive slow to take it in (driven at 75 - 80 mph) and never a problem. Specifically the advantage of having the whole "kit" lower far outweighs the supposed advantage of 12" setup. I've pulled and have both sizes and while pulling I can discern no difference.


John H16, H14
Re: Trailering wind resistance [Re: _flatlander_] #71197
04/12/06 09:15 AM
04/12/06 09:15 AM
Joined: Sep 2005
Posts: 1,187
38.912, -95.37
_flatlander_ Offline
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Pardon me, maybe this should be a new thread?

With soaring fuel costs and lots of miles slated for this season, I like the lower idea (8" wheels), from the wind resistance standpoint. I'm about to take the old school, overblown cooler style box OFF my 16 trailer (sail tube only). Nothing in it can't be kept in the vehicle. Thinking of doing something to the front of the box on the 20 trailer (along the lines of Thull) to cut down wind resistance. Or is this useless? Engineers? I dunno, maybe I can tape some smoke bombs to my bumper. Will a significant amount of air go under a tow vehicle at 70 mph?

Last edited by flatlander18; 04/12/06 09:16 AM.

John H16, H14
Re: Trailering wind resistance [Re: _flatlander_] #71198
04/12/06 12:53 PM
04/12/06 12:53 PM
Joined: Jul 2005
Posts: 306
St. Louis, MO
hobienick Offline
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St. Louis, MO
I don't think you will see any increase in fuel economy if you take the tool box off your trailer. Remember how much quieter it gets in your car when you tailgate a tractor trailer. The same thing happens behind your vehicle but on a smaller scale. The increase in drag is mostly (at least for me) due to the boat being wider than my car. So, my car has not moved the air out of the way yet.

I don't think a couple inch difference in height of the trailer will increase your fuel economy either for the same reason. Most of the drag comes from the boat being wider than the tow vehicle. Your best bet would be to dissassemble to the boat so it can fit within the width of your tow vehicle. Then you will have better fuel economy.

My 2 cents


Nick

Current Boat
Looking for one

Previous Boats
'84 H16
'82 H18 Magnum
'74 Pearson 30
St. Louis, MO
Re: trailering [Re: hobienick] #71199
04/12/06 01:02 PM
04/12/06 01:02 PM
Joined: Jun 2004
Posts: 141
Panama City Beach, FL
steveh Offline
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Panama City Beach, FL
Quote
The tracking of the trailer has very little (if anything) to do with the stance of the wheels. It is the longer tounge that will keep it tracking behind the two vehicle. It will still blow around when a semi passes you, or you the semi, but it will not jerk the tow vehicle around as much and will recenter in a much more gentle way than a short tounged trailer will.


All other things being equal, for an equivalent disturbance, the wider trailer will have larger oscillations in the disturbing, restoring and damping forces due to the longer moment arm from the tow point to the tire contact point. In particular, the component of the tire side force that resolves to a force pointing directly aft and acting on the moment arm, sin(yaw)*(axle length), will have a much larger impact on the system on a wider trailer than on a narrower trailer.

Assume a wind vane with a pivot arm of length 1 ft from the pivot point to the center of lift of the vane. Assume a second wind vane with the mid point of an arbitrarily long cross bar attached to the same 1 ft arm with a vane at each end of the cross bar. Any length cross bar will be less stable than the zero crossbar case and with a long enough cross bar, the wind vane will be unstable.

Looking at it qualitatively, an absurdly long crossbar (axle) will, in effect, result in a very short pivot arm (tongue length).

Please don't make me draw a free body diagram.

Re: trailering [Re: steveh] #71200
04/12/06 01:11 PM
04/12/06 01:11 PM
Joined: Nov 2002
Posts: 5,558
Key Largo, FL & Put-in-Bay, OH...
Mary Offline
Carpal Tunnel
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So am I right in my totally subjective impression that, in general, a narrower axle will tow better than a wider axle, if the tongue length is the same for both and they are both carrying the same load and with the same tongue weight and same percentage of weight forward of the axle?

Re: trailering [Re: Mary] #71201
04/12/06 01:20 PM
04/12/06 01:20 PM
Joined: Jun 2004
Posts: 141
Panama City Beach, FL
steveh Offline
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Panama City Beach, FL
Nick says no, I say yes. These guys also say yes, though they don't show equations to prove it.

Quote
Trailer length and length with respect to width is another factor. Longer trailers typically tow better -- or more accurately, a greater separation between the rear most wheels of the tow vehicle and the fore most wheels of the trailer. A long tongue as discussed in the Strength section can help in facilitating separation. The point here is really the distance with respect to the width. Look at the width of the trailer with respect to the tow vehicle and with respect to the axle separation. The wider the trailer, the more it will benefit from length.


If you feel like dropping $12, you could most likely find the definitive answer in this ... Analytical Methods and Test Procedures

Re: Trailering wind resistance [Re: _flatlander_] #71202
04/12/06 01:49 PM
04/12/06 01:49 PM
Joined: Jan 2006
Posts: 11
Sacramento, Ca
acdavis Offline
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Sacramento, Ca
As far as wheel sizes go I feel confident with 8" tires. True a 12" wheel spins 30% less than an 8". Typically 12" tires are wider than 8" tires, which means more rubber is on the road, which means more traction.

In mechanical design we tend to deal with cyclical loads. Funny things happen when a load occurs over and over again. Think about bending a paper clip, you can do it once or twice but if you do it over and over again eventually it breaks. The goal of mechanical engineering is to design paper clips that don’t break. Bearings are designed to have an “infinite” life (on paper any way). On the box it never says “replace after 1 million revolutions.” Industry standards such as SAE are set up to make sure that machine parts don’t have a finite lifespan.

What is more important than wheel size is that your hubs are well maintained. Well maintained bearings with an 8" wheel will last for years and years and miles and miles. Poorly maintained bearings regardless of wheel size can be extremely dangerous. It is all about lubrication and maintenance.

A friend of mine was towing his Boston whaler from Tiburon (just across the Golden Gate from SF) down to Monterey. He didn’t know about bearings or how to pack his bearing buddies. Just south of San Francisco he noticed his trailer was smoking and pulled over right away. A bearing had seized and when he jacked his trailer up the wheel fell right off. The heat had softened his axel and the seized bearing has sheared the wheel right off. I guess the moral of the story is to check your bearing buddies regularly.

Re: Trailering wind resistance [Re: acdavis] #71203
04/12/06 02:10 PM
04/12/06 02:10 PM
Joined: Aug 2005
Posts: 2,921
Michigan
PTP Offline
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Michigan
I have brand new springs/bearings/hubs/tires (12) that were installed about 6 months ago and I have maybe trailered 100 miles since. Do I need to do anything to the bearings before a long trip?

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