Swaying Boat

[marcel haber]

hi there fellow raiders,

Recently upgraded and did a huge make over on the boat trailor.

The trailor originally had 10 inch tyres which we have upgraded to 15 inch wheels.

I have a pongrass surfmaster which is made of fibre glass with a 50 horse power yamaha on the tail.

The boat is a open runabout.

I tow the boat behind a toyota SR5 Hilux 4wd and have noticed that whilst travelling on the motorway the boat and trailor seem to sway from side to side, the quicker you go the harder it sways, even at around 60 klms swaying still occurs.

Are there any solutions to this problem . let me know.

Tight lines

TWIN 1

MARCEL

[Mark L]

hi there fellow raiders,

Recently upgraded and did a huge make over on the boat trailor.

The trailor originally had 10 inch tyres which we have upgraded to 15 inch wheels.

I have a pongrass surfmaster which is made of fibre glass with a 50 horse power yamaha on the tail.

The boat is a open runabout.

I tow the boat behind a toyota SR5 Hilux 4wd and have noticed that whilst travelling on the motorway the boat and trailor seem to sway from side to side, the quicker you go the harder it sways, even at around 60 klms swaying still occurs.

Are there any solutions to this problem . let me know.

Tight lines

TWIN 1

MARCEL

mate you may have to bring your axles fwd more, they are genrally 600-700mm fwd of the last roller on the trailer. Try this and I think you may have pleasent suprises. Good luck and pm me If you want more info

[Flightmanager]

Twin 1 , get this problem sorted ASAP!! The potential for a jacknife situation is very high , and can have disasterous results. Make sure the boat is evenly loaded , and ensure that the tyre pressures are correct in both wheels. Also , as Mark suggested , moving the axles should have the desired effect.

Ross

Edited May 29, 2007 by rzep

[pjbink]

mate you may have to bring your axles fwd more, they are genrally 600-700mm fwd of the last roller on the trailer. Try this and I think you may have pleasent suprises. Good luck and pm me If you want more info

I think that you will actually move the axle back! You want around 8 to 10% of the total rig weight as downforce on the towbar to minimise swaying. So it sounds like you don't have enough downforce. You can also fit torsion bars which are a cheap and effective device to help eliminate this problem as well as improve general handling, braking and level ride height.

[tiger_shark]

Try to move the boat further up the trailer if you can...or as said previously, move the axles back..

[a boat]

Good Morning Marcel, if your boat is swaying or "fishtailing" then you do not have enough weight on the towbar. Move your axle backwards to allow more weight on the towball, about 10% of the weight of the rig is a good weight to have on your coupling. Also make sure that the boat is all the way forward on the trailer and the transom of the boat is supported by the rear rollers. I am seen many boats where the boat overhangs the trailer which therefore means that the weight of the outboard is not being supported.

Cheers,

Huey.

[james1990]

With our old rig double trouble.,

The previous owner towed her with a landcruiser ute which had a lift kit so he moved the axle set as far backwards as possible so he didnt blow the rear tyres out on the trailer.

When we bought her we towed her forabout 2 years with a ford territory and a nissan patrol which were both alot lower in the rear than a cruiser ute, and was constantly going through tyres, every 200kms of travel we would have to change one of the front tyres due to blow outs, tyre damage etc.

About 12months ago we spent 2 weekends on the trailer getting the setup right so we would stop getting blowouts etc.

We never had 2 change a tyre on the trailer in 12 months, and they were in top condition when we sold her.

They were 9 inch wheels inflated to 38PSI each.

I was told by a VERY experienced four wheel driver that the right setup for your trailer is when the hitch has 200lb's of weight on it heres the method

step 1--take a set of bathroom scales and a car stand, place the carstand on the scales and drop the hitch of the trailer on it and see how much it weighs.

step2--if the weight exceeds 200lb's you will have to move the wheel carrige forwards, if it is under 200lb's move the carrige backwards. untill you get the correct weight.

We were lucky with the old boat that the mudgaurds, axles, wheels etc were all connected via a large metal plate so no weldding or griding was needed.

cheers james

[achjimmy]

Good Morning Marcel, if your boat is swaying or "fishtailing" then you do not have enough weight on the towbar. Move your axle backwards to allow more weight on the towball, about 10% of the weight of the rig is a good weight to have on your coupling. Also make sure that the boat is all the way forward on the trailer and the transom of the boat is supported by the rear rollers. I am seen many boats where the boat overhangs the trailer which therefore means that the weight of the outboard is not being supported.

Cheers,

Huey.

Hello Again Huey

how close do the rollers need to be to the transom? The trailer i just got with boat was rebuilt a little while ago and you can see where they have mooved the wheel assembly back (75-100mm) and also the winch post back. The transom is approx the same distance past the last wobble roller. It tows really well except for a bloody anoying rattle in the tow hitch. I have tried adjustment but it seems to be caused by excessive clearance in the release handle shaft that hooks under the ball.

I have tried to attach pic.

[pjbink]

Hello Again Huey

how close do the rollers need to be to the transom? The trailer i just got with boat was rebuilt a little while ago and you can see where they have mooved the wheel assembly back (75-100mm) and also the winch post back. The transom is approx the same distance past the last wobble roller. It tows really well except for a bloody anoying rattle in the tow hitch. I have tried adjustment but it seems to be caused by excessive clearance in the release handle shaft that hooks under the ball.

I have tried to attach pic.

I though most boats were set up for the transom to overhang the trailer by a few inches - presumably to aid launching.

[achjimmy]

I though most boats were set up for the transom to overhang the trailer by a few inches - presumably to aid launching.

thanks Billfisher, i just didnt know.

I would like to make a support up for the outboard but the back crossbar on the trailer is hinged and quite well under. i am going to see what i can come up with.

On another note does anybody know where to get that galavanised planking (like cable tray but stronger) I want to make a gangway to the right of the centre rollers for retieving.

Cheers

jim

[marcel haber]

mate you may have to bring your axles fwd more, they are genrally 600-700mm fwd of the last roller on the trailer. Try this and I think you may have pleasent suprises. Good luck and pm me If you want more info

thanks for the advise mate , will look into.

Love your boat building, keep up the great work, you are truely talented.

marcel.

Good Morning Marcel, if your boat is swaying or "fishtailing" then you do not have enough weight on the towbar. Move your axle backwards to allow more weight on the towball, about 10% of the weight of the rig is a good weight to have on your coupling. Also make sure that the boat is all the way forward on the trailer and the transom of the boat is supported by the rear rollers. I am seen many boats where the boat overhangs the trailer which therefore means that the weight of the outboard is not being supported.

Cheers,

Huey.

Thanks Huey,

this advise is greatly appreciated and I will have to look into this problem and get it fixed, will keep in touch and let you know of the outcome.

Thanks to all the very helpful fish raider members. What a top site .

[Thunder]

As others have said, you will have to move the axle backwards, not forwards.

You may also have to check the bushes in the springs, and how much flex is in your tyres.

I have a 5.5m fibreglass boat and had the same trouble.

My trailer was originally a tilt trailer and they changed it to a multi roller trailer. There was movement in the tilt section so I drilled and bolted it together. Heaps better.

I noticed when I rocked the boat from side to side, there was a lot of deflection in the tyres - ie high sidewalls. I have since gone for lower profile tyres and have them inflated to near maximum. A bit better. I am trying to source some rally car tyres as they have a very stiff sidewall. This will reduce a lot of the movement and I can run them at lower pressures. Commercial tyres have harder sidewalls and are good for carrying weight, but the sidewalls are a lot higher. The lower the boat is to the ground, the easier it is to launch and retrieve, especially when the boat is heavy.

I moved the axle back around 100mm as there was not much weight on the towball. ie it was fairly easy to lift the front of the trailer off the ground - it should be very heavy. The axle and mudguards were bolted to the chassis, so it was fairly easy to do. This improved it significantly.

I then replaced the springs with heavy duty springs and it is a lot better again. Once I get the rally tyres I will be happy with it.

My boat is very heavy and I contemplated fitting dual axles, but when you have to push the boat in and out each day, the twin axles are terrible for turning and manouvering, so I am stuck with single axle.

I can now tow my boat at 100km/h in safety, whereas before, if I travelled over 90km/h I could feel the boat pulling the rear end of my wagon sideways.

I hope the above helps you, as there could be more than one cause to your problem.

Cheers

Greg

[marcel haber]

As others have said, you will have to move the axle backwards, not forwards.

You may also have to check the bushes in the springs, and how much flex is in your tyres.

I have a 5.5m fibreglass boat and had the same trouble.

My trailer was originally a tilt trailer and they changed it to a multi roller trailer. There was movement in the tilt section so I drilled and bolted it together. Heaps better.

I noticed when I rocked the boat from side to side, there was a lot of deflection in the tyres - ie high sidewalls. I have since gone for lower profile tyres and have them inflated to near maximum. A bit better. I am trying to source some rally car tyres as they have a very stiff sidewall. This will reduce a lot of the movement and I can run them at lower pressures. Commercial tyres have harder sidewalls and are good for carrying weight, but the sidewalls are a lot higher. The lower the boat is to the ground, the easier it is to launch and retrieve, especially when the boat is heavy.

I moved the axle back around 100mm as there was not much weight on the towball. ie it was fairly easy to lift the front of the trailer off the ground - it should be very heavy. The axle and mudguards were bolted to the chassis, so it was fairly easy to do. This improved it significantly.

I then replaced the springs with heavy duty springs and it is a lot better again. Once I get the rally tyres I will be happy with it.

My boat is very heavy and I contemplated fitting dual axles, but when you have to push the boat in and out each day, the twin axles are terrible for turning and manouvering, so I am stuck with single axle.

I can now tow my boat at 100km/h in safety, whereas before, if I travelled over 90km/h I could feel the boat pulling the rear end of my wagon sideways.

I hope the above helps you, as there could be more than one cause to your problem.

Cheers

Greg

Thanks Greg for your useful information,

My brother and I HAVE MOVED THE BOAT FURTHER UP THE TRAILOR BY 10 CM JUST BY UNBOLTING AND RE POSITIONING THE FRONT BAR WHICH HOLDS THE WINCH AND BOAT TO THE TRAILOR, THIS HAS GIVEN US AN EXTRA 20KLMS IN SPEED BUT LONG TERM WE WILL NEED TO MOVE THE AXIL BACK AS STATED.

KEEP YOU POSTED.

MARCEL

TWIN 1

[bradludwig]

Mate the difference in weather any trailer sways or not can be as simple as how it`s loaded.

Try putting all your heavy gear as far up the front of the boat as you can.On longer trips dont fuel up until you get closer to destinations.Generally it would be easier to move the boat a couple of inches further up the trailer than moving guards and axle(but thats just my opinion)Is your winch stand U-Bolted or welded?

[marcel haber]

Mate the difference in weather any trailer sways or not can be as simple as how it`s loaded.

Try putting all your heavy gear as far up the front of the boat as you can.On longer trips dont fuel up until you get closer to destinations.Generally it would be easier to move the boat a couple of inches further up the trailer than moving guards and axle(but thats just my opinion)Is your winch stand U-Bolted or welded?

Gooday bigears2u,

Our winch bar is bolted and hence made it alot easy to undo the bolts and slide the whole arm forward by 10cm or so.

Moving the arm forward as stated before has given us an extra 20klms in speed, also by loading the front of the boat with the spare tyre and two portable fuel tanks has shifted the load from the back of the boat and has reduced dramatically the swaying of our boat trailor whilst in motion.

cheers

MARCEL

TWIN1