Trying to lighten tongue weight

[GregE]

I have a 16 foot aluminum Tracker Grizzly (modified V hull). Boat itself weighs 400 lbs. Outboard motor, around 90 lbs. I have about 10 inches available from the transom keel to the very ends of the bunks. I know it wouldnt make too much tongue weight difference to put the boat on the trailer closer to the back edge of the bunks, but every ounce I can off the tongue would be best. It's quite heavy right now. I pull this boat with a 2003 Taurus with a Class 1 hitch. Works fine, I just prefer less tongue weight if I can get it.

What's the safe zone for having a boat on the bunks? Should the very furthest back be the transom keel aligned with the bunks? Or can it be a little further? Bunks are carpeted 2x4s and overhang the rear trailer crossmember by about 10 inches or so.

Right now the motor is off and I've pushed the boat to that very back point of the bunks. Boat nearly has all of its weight on the forward crossmember of the trailer (trailer only has two crossmembers. Very little weight on the rear crossmember - almost teeters on it (but no motor though). Is this as far back as I should go?

How about the bow hitch? Should the winch strap connect to the bow eye below the rubber stop (in my case it's a roller type) or above it? I think below but I want to make sure. Previous owner had it below but it was so close to the roller the strap hook is digging into the rubber.

 

[Silvertip]

Re: Trying to lighten tongue weight

The boats transom must be supported by the bunks so you don't want the back of the boat past the ends of the bunks. The bunks should extend past the back of the boat only an inch or so. If you need further adjustment, you move the axle forward to lighten the tongue weight, or backward to increase it. The winch strap should always go UNDER the bow eye so in panic stop the boat can't climb over the bow stop and end up onthe trunk of your car. You should also have a safety chain from the bow eye to the trailer frame. Likewise, at the back you should have tie down straps. A boat that light should not pose much of a weight problem on the car. Without the motor on the boat, the tongue might appear heavy. But with the motor on, you should have 7 - 10% of the total load as tongue weight. You have a load of about 1000 pounds (boat, motor, trailer, & stuff) so 70# to 100# is good. You can even distribute stuff in the boat (like the full portable gas tank) to move weight around.

 

[GregE]

Re: Trying to lighten tongue weight

Thanks Silvertip, I appreciate it. I ended up with the transom about an inch in from the bunk edges, and moved the winch supports so the strap could pull tight and is about 1/2 inch below the bow stop so as NOT have the strap hook digging into the stop. Thanks for clarifying the over/under for the winch strap. Under sounded right, but I never knew of the reason. Makes good sense. As for saftey strap from bow hook to trailer, yep, I have that, as well as the tie downs on the transom.

I wont be moving the axle. But one day I plan to do some modifications to the boat and may need to. I was looking at that today, wondering how it's done properly. How do you move an axle and still have it remain completely aligned? Obviously measurements from current position to new position and ensuring both sides are done the same distance EXACTLY. Just curious of how exact "exact" has to be. I know with car front end alignments, they use precision tools, whereas with a small trailer and a do-it-yourself job I'm thinking a tape measure and go for it. Also, how does one move the axle so as to be able to test the result and being able to move more before committing?

 

[tashasdaddy]

Re: Trying to lighten tongue weight

you can move the axle, if it is a bolt on. but welded brackets, it is better to add length to the bunks, change the bunks. you want 10% of the total weight on the tongue.

 

[Silvertip]

Re: Trying to lighten tongue weight

Precise axle alignment on a single axle trailer is not critical as the wheels aren't steering anything like on a car. If you've ever looked at a tractor-trailer rig on the highway you should notice the trailer dog-tracks a little to the right. Some more than others. It allows the driver a little better view down the side of the rig. The same thing will happen with a boat trailer. It will simply track a little to the right or left if you aren't exact on the right-left adjustment. The best way to measure it would be to measure from the center of the coupler to the tip of the spindle on each side. But you need a straight line to do that. One most newer trailers the suspension is on a sub-frame that is held to the main trailer frame with "U-bolts". You simply loosen the bolts and slide the subframe forward or backward as required.

 

[Shamic]

Re: Trying to lighten tongue weight

Precise axle alignment on a single axle trailer is not critical as the wheels aren't steering anything like on a car. If you've ever looked at a tractor-trailer rig on the highway you should notice the trailer dog-tracks a little to the right. Some more than others. It allows the driver a little better view down the side of the rig. The same thing will happen with a boat trailer. It will simply track a little to the right or left if you aren't exact on the right-left adjustment. The best way to measure it would be to measure from the center of the coupler to the tip of the spindle on each side. But you need a straight line to do that. One most newer trailers the suspension is on a sub-frame that is held to the main trailer frame with "U-bolts". You simply loosen the bolts and slide the subframe forward or backward as required.

I wasn't going to reply to this, but it has to be said. Trailers are NEVER designed to "dog-track", that would only occur if there is a problem with alignment. It only burns up tires faster, and creates other issues under braking, etc. It is very easy to determine proper alignment, such as measuring from fixed cross members on the trailer to the axle brackets.

 

[Silvertip]

Re: Trying to lighten tongue weight

You can weld the tongue of a single axle trailer at a 45 degree angle off the trailer and it will still track perfectly parallell to the tow vehicle center line -- just off to the side with no impact on tire wear. If you measured the the parallelism of the rear axle of the tow vehicle, you would find the trailer axle also perfectly parallel to it. Tire wear on any trailer is far more sensitive to tow-in, tow-out, and positive/negative camber issues than axle alignment. Axle alignement on trandem and tri-axle trailers is important for good tire wear, but alignment issues are in relation to each other. Misalignment on those trailers does cause straight ahead loading if all axles are not parallel with each other.

 

[Titanium48]

Re: Trying to lighten tongue weight

You can weld the tongue of a single axle trailer at a 45 degree angle off the trailer and it will still track perfectly parallell to the tow vehicle center line -- just off to the side with no impact on tire wear. If you measured the the parallelism of the rear axle of the tow vehicle, you would find the trailer axle also perfectly parallel to it. Tire wear on any trailer is far more sensitive to tow-in, tow-out, and positive/negative camber issues than axle alignment. Axle alignement on trandem and tri-axle trailers is important for good tire wear, but alignment issues are in relation to each other. Misalignment on those trailers does cause straight ahead loading if all axles are not parallel with each other.

Not quite. If the tongue is offset from the perpendicular plane running through the center of the axle, the force applied on the trailer by the tow vehicle is no longer co-linear with the friction and drag forces experienced by the trailer. This creates a torque that causes the trailer to rotate to try to lessen the offset. It won't rotate very much because the rotation causes the wheels to begin to slip sideways and creates uneven aerodynamic loading, both of which act to counter the rotation-inducing torque. Nonetheless, there will still be some sideways movement of the tires resulting in increased friction and wear.

As for the traditional alignment parameters (camber, toe-in), with a solid axle they are not adjustable and will be zero unless the axle is bent.

 

[Captain Caveman]

Re: Trying to lighten tongue weight

Someone correct me if I'm wrong, but another issue could be the rise on his hitch. Since he's towing with a Taurus the hitch might be low so the trailer is not parallel with the ground, but rather leaning on the back of the car. Maybe some more rise in the hitch could help.

 

[Bondo]

Re: Trying to lighten tongue weight

If you've ever looked at a tractor-trailer rig on the highway you should notice the trailer dog-tracks a little to the right. Some more than others. It allows the driver a little better view down the side of the rig.

Nope,...... Not So.....

Any Doglegging you see following a Big Rig is caused by the Road's Camber, or a Mechanical Problem.......

Big Rig Wagons are Designed, Built,+ Serviced to track Dead-On behind the Kingpin or Pintle.....

In order for your tongue at an Angle thing to work,..... The Axle must also be at an Angle........

 

[GregE]

Re: Trying to lighten tongue weight

Someone correct me if I'm wrong, but another issue could be the rise on his hitch. Since he's towing with a Taurus the hitch might be low so the trailer is not parallel with the ground, but rather leaning on the back of the car. Maybe some more rise in the hitch could help.

You're right about the hitch rise, and I know I really need to get a different draw bar and raise it somewhere between around 4-7 inches. I gotta get it hooked up and check that out. I didn't make any changes last year, but I do need to raise it some. But as for weight, a rise may lessen the weight slightly. I have the boat propped up now, and in just my test lifting by hand, I really can't tell a difference in weight when it's high like that vs when it's low. It's still pretty heavy but probably within the 7-10% ideal range. Closer to 10% I bet. I really should weigh it so I'll know for sure.

 

[bjcsc]

Re: Trying to lighten tongue weight

Hmmm...this would be a good mythbusters episode...

 

[fishrdan]

Re: Trying to lighten tongue weight

Before going to college (and the main reason I went to college) I worked at a diesel trailer manufacturer. They squared the axel(s) to the kingpin, no offset. I worked in final assembly where this axel(s) were adjusted and have seen it done a time or 2.

Have you figured the tongue weight yet? I did this with a bathroom scale on my jon boat trailer, you should be able to see if there is a difference in weight with the different tongue heights, though I think it would be marginal. Your best bet will be to move the axle forward, move the boat back or shift the boat's load back as stated before.

 

[GregE]

Re: Trying to lighten tongue weight

Got it weighed today. 160 lbs on the tongue. Gas tank/battery/gear not in boat. This is at current height, which when I did measurements, the boat is actually level.

Boat itself is 395, trailer (I'm guessing) 500, outboard 90, gas tank/battery/gear 100. Also a 4 x 7 x 3/4 plywood floor, approx 65.

That puts me around 14%. I'd like to drop it a couple percent if I could. Anyone know (or have a link) to how to calculate how much weight I'd move off of the tongue by moving the axle forward X number of inches? Still searching the net for that info.

I also need to call BassPro and see if I can get the exact weight of the trailer. My guess is only a guess. I hope I'm high with that.

 

[jtexas]

Re: Trying to lighten tongue weight

I'm not a physisisist or anything, but the trailer tongue will weigh the same at any height. Unless your load shifts.

how long is the trailer, and how far from the transom to the axle as it is right now?

 

[fishrdan]

Re: Trying to lighten tongue weight

Depending on what your total rig weighs, you can use a bathroom scale to figure out the total weight. Tougue + left wheel + right wheel = total weight. My loaded jon was 700# total, tongue 150#, left tire 260#, right tire 290# (batteries on the right side weighing down that side of boat, but my fat a** evens it out in the water ).

If your over the scale's max weight there's a way to measure heavier weights by using a board on the scale, but I won't go into it unless you need the info.

To figure out what your tongue weight will be by moving the axle forward, place jack stands where you want the axle and measure the tongue weight. (you might have to use a 2x4 under the trailer frame if the springs are interfeering with jack stand placement.

 

[Frugal Floater]

Re: Trying to lighten tongue weight

"I'm not a physisisist or anything, but the trailer tongue will weigh the same at any height. Unless your load shifts."

Actually, the force will be slightly greater. The fulcrum would be the axle and the force would increase if not in static equilibrium. This is because force would not be straight up and down, but at a very slight angle towards the vehicle. I don't think it would make a big difference though.

There are suspension spring kits that help prevent a severe squat in your car, but have no idea if they are worth the money.

 

[External Combustion]

Re: Trying to lighten tongue weight

Whether the load lightens or increases by rasing or lowering the tounge height from level is not necessarily an easy answer. It depends on the center of gravity of the combined load and the axis of rotation about the combined axles. The calculations only involve very simple algebra, but the short answer is that it makes no real difference until the angle goes over fifteen degrees on most loads.

Pretty steep huh?

GregE PM me and I can give you the formula for the tounge weight calculation or I will do it for you and send you the complete problem. What you will need to know is the total weight of the rig (found by using the public scales, trailer unhitched and the tow vehicle off the scales), the current tounge weight and the distance from the center of the hitch ball to the centerline of the trailers axle/axle combination. This is a plug and crank formula that anyone that paid attention in fourth grade math can do. It just takes a couple of paragraphs to make it clear in your mind what is going on and why. Nothing more than addition and multiplication.

By the way the center of gravity is commonly found by taking the tounge weight at a level trailer height, jacking it up a few inches and comparing the tounge weight again. Plug and crank another simple formula. Have a relatively sensitive scale as the difference will not be great.

 

[GregE]

Re: Trying to lighten tongue weight

When attached to my car, I measured from level ground to the bottom of the trailer's tongue, then measured also from the ground to the bottom of the very back of the trailer. Tongue is about 3 inches lower, so I do want to get that higher, though I'm only doing it to create a level trailer, not at all looking for it as any significant tongue weight changer.

I'll have to get some more measurements, etc. And I'm pretty sure I'm very high on my estimate of trailer weight. After launching boat and parking last weekend, I picked it up in the back and moved it to make it more straight where I parked it , so if it was anywhere near 500, that lift would have not been so easy. I'm glad of this, but at the same time, my tongue weight percentage is higher than originally calculated too.

I appreciate everyone's responses here. I've not been around the forum for a few days to read any of it. Lots of good info.

External_Combustion, I'll see if I can get any additional data. Thanks.

 

[tashasdaddy]

Re: Trying to lighten tongue weight

http://forums.iboats.com/showthread.php?t=252519