Trailer fishtailing

[lightwood38]

Gday, Towed my boat for the first time today at speed and every time i got to about 90kmh the trailer started to fishtail. What would be the cause of this. I have new wheels and tyres, bearings are fine and the axle looks perfect. My old boat never did this right upto 110.


Any ideas what to look for.

cheers

 

[fishrdan]

Re: Trailer fishtailing

Not enough weight on the trailer's tongue, you should have 10-15% of the trailer's weight on the tongue. Move the boat forward on the trailer or the axle back. If you are hauling along a bunch of heavy things in the boat while trailering, move it forward.

 

[redone4x4]

Re: Trailer fishtailing

Not enough weight on the trailer's tongue, you should have 10-15% of the trailer's weight on the tongue. Move the boat forward on the trailer or the axle back. If you are hauling along a bunch of heavy things in the boat while trailering, move it forward.

yep, thats just it. move the axle, or throw some weight in the bow. i take my tube (that weighs alot, maybe 50 lbs.) in the bow when im trailering. no sway at all here. maybe load some stuff under the bow cushions. alot of stuff thats normally in the ski locker like lines n stuff can fit under the bow seats.

 

[lightwood38]

Re: Trailer fishtailing

Thanks guys, how much forward movement are we talking, I have about 6 inches or so and moving the axle would be a massive PITA.

Here's a pic of how for forward I can go.

cheers

 

[Jeep Man]

Re: Trailer fishtailing

Figure the weight of the rig, including the trailer, use a bathroom scale under the tongue and go from there. May be as simple as moving stuff forward.

 

[Bote]

Re: Trailer fishtailing

You maybe able to shift axle backwards. I have mid 90s Brooker tilt trailer
and axle can be moved farwards or backwards . Four bolts hold wheel and axle assembly to the trailer frame.

 

[tashasdaddy]

Re: Trailer fishtailing

move the axle, you are already too far up on the trailer.

 

[Bote]

Re: Trailer fishtailing

Moving axle further back will put more weight on the tongue. Isn't this what's required ?

 

[kenmyfam]

Re: Trailer fishtailing

How about a photo of the whole set up not just the bow.
Sure sounds like you need to move the axle back some. The photo you show sure looks like the boat is too far forward at present. Looks like someone tried moving it forward already. Check your current tongue weight with the bathroom scales at your towing height and post what you find.

 

[rentprop1]

Re: Trailer fishtailing

looks like the tongue of that trailer is way to short, if I used my truck to back that thing up and deviated 45 degrees like to back into my drive way the boat and that winch mast would be rubbing against my truck ???????

 

[4JawChuck]

Re: Trailer fishtailing

I agree, looks like someone cut 12" off the tongue to remove a damaged section.

 

[lightwood38]

Re: Trailer fishtailing

Thanks guys, Trailer has not been cut and the trailer is the original one for the boat. Here are some pics of the whole boat, the rear and a pic of the axle setup. As you can see moving the axle back would involve cutting off the spring mounts and relocating them and relocating the guards. Not something I want do do if I can help it.

How do I tell the weight of the boat? When I spoke to the marine place a couple of weeks ago inquiring about trailer brakes he told me that the boat and trailer would be 650KG max. State regulations in Australia require brakes at 750KG so I know I am under that.

The boat is 16.5' and really there is no weight at the front, but my last boat and trailer were exactly the same only it had a 100hp merc which would have been more heavy.

Thanks for all the replies I'm much appreciated.

cheers

 

[kenmyfam]

Re: Trailer fishtailing

Did you check the tongue weight yet ???

 

[lightwood38]

Re: Trailer fishtailing

I put a set of scales under the jockey wheel and they said 84kg.

 

[lckstckn2smknbrls]

Re: Trailer fishtailing

I'm guessing that the boat and trailer weigh more than you think.

 

[EddiePetty]

Re: Trailer fishtailing

Good Day, Mate !!!

First off...that rig looks to be quite heavier that 650KG (1433 lbs.) !!
Better head over to a truck stop (lory stop) and get an accurate weighing.

IF your weights are correct, your current tongue weight is 13% of your gross which is well within the norm, if not just slightly high. [Provided your bath scale reading of 84KG (185 lbs. is accurate).]

I suspect that your axle is not square to the hitch point. Measure from a fixed reference point at the hitch to a common point on each spindle. A measurement variance of more that a 1/4" will result in the trailer wagging the tow vehicle.

No worries mate...we're gonna fix this thing !!!

FWIW....Ed in 'ol Virginny

 

[4JawChuck]

Re: Trailer fishtailing

The trailer axle is too far forward, looks almost like a trailer meant for a inboard motor equipped boat.

 

[Bote]

Re: Trailer fishtailing

I just had a look at your boat specs in ?Secondhand Boat Secrets? magazine

Swiftcraft Seagull
Length ? 5m (16.6ft)
Hull weight ? 430kg (948lb)
Weight on trailer ? 900kg (1984lb)
Max power ? 125 hp
Best Power - 75hp

Sadly it seems you well over the legal limit of 750kg for the trailer without brakes.
You may need to sell this trailer and buy one that complies.
You may also install electric brakes but it will involve new axle, hubs with brakes, wheels and tyres and new wiring. All could be costly.

 

[Bob_VT]

Re: Trailer fishtailing

I had a similar situation and I was unable to move my axle so I welded an extension onto the tongue. That was about 8 years ago but it was my only solution. http://forums.iboats.com/showthread.php?t=35063&highlight=welded

 

[rbh]

Re: Trailer fishtailing

throw a piece of DOM square steel tubbing into the reach to give yourself an extension.
rob