welding a galvanised dinghy trailer.... repair advice + suspension question

[FairweatherDave]

I have a combi trailer (ie road trailer plus boat trolley) for my Wayfarer and whilst using the boat I had a good look at the road trailer. I noticed what I think are the first signs of a weld beginning to go, ie the start of a hairline crack. I want to get it checked out but since I know nothing about welding I was wondering if ordinary welding places are good enough or does a galvanised trailer need special techniques? (I expect the repair would not be galvanised as that requires dipping I believe?).

Secondly the trailer is 12 years old. Should the suspension units be replaced purely due to age.... I stood on the trailer and bounced up and down but could see no movement (though I am only half the weight of the boat). Obviously duff suspension could cause the welds to fail. (The suspension units look like "arms" like you would see on many small trailers, not coils). I know there is a test where you look at the angle of the arm but it all looks normal to me.

Any advice appreciated. Thanks

 

[jerrytug]

Welding steel with a zinc coating, ie galvanised, gives off extremely poisonous fumes, and most welders won't touch it.
Make a mild steel repair section (which can of course be welded on the bench) and bolt it on your trailer.

Indespension, or other trailer spring makers, probably have websites with the info on how to check yours.

 

[MM5AHO]

Welding galvanized steel is quite possible, and frequently done.
If not removed, a cloud of zinc oxide is emitted as the zinc vapourises. (zinc oxide is white, and in sunnier countries is the principal ingredient in sun blocker. Its the bulking agent used in many cosmetics, is a UV stabiliser in tyre making and has many other uses) This can cause an ill feeling. Older welders call this "Galvy Flu", and they used to drink milk before and afterward to stave off the effects.

The simpler solution is to grind off the zinc with an angle grinder before repairing the weld.
The welding will destroy the galvanizing in the heat affected zone, and this area will then be subject to corrosion. But the most common thing to do there is to immediately paint the weld area, best using zinc rich paint.

 

[sarabande]

if the suspension units contain rubber/polymer inserts, they will be pretty well past their use-by date, and hardened.

One of the worst things you can do is to keep the dinghy on the trailer for a long time without taking the load off the units. If loaded and static, the insert hardens in the compressed mode. Hard suspension can cause cracks in the dinghy hull. Been there

 

[FairweatherDave]

Thanks all. Really useful stuff. I have jacked the boat up to save the tyres and suspension, but not always. Think I will be doing the suspension job once the trailer is fixed. We are doing a big trail this summer....

 

[Lakesailor]

I bought a filter mask for welding galv metal. The fumes really are horrible.

My best advice for the suspension units is to look on a site like Trailer Tek ( http://www.trailertek.com/acatalog/Unbraked_Suspension_Units.html ) and get the lowest rated ones you can that will be legal for your outfit. I replace the standard ones on a jetski trailer when I started carrying my clinker dinghy on it. Harsh jarring is not good for old wooden boats and not a lot better for modern plastic ones.
My boat and trailer weighed 230 Kgs so I got some units rated at 250 kgs (the pair) Of course the wheels and tyres are not a load on the suspension, but the difference was remarkable with not bashing and crashing. the boat seemed to float along behind me. (Yes you can use bathroom scales to weigh it. One wheel at a time. Don't forget the jockey wheel )
Make sure you get the right stub axle size 1" and 25mm are not the same.

 

[FairweatherDave]

I have found a welder who is obviously experienced with galvanised metal so that is that bit fixed. Good point about getting the right spec on the suspension units. It is a can of worms as to whether my boat is overloaded with camping gear or not but at least towing on the French roads is normally pretty smooth. Pretty interesting idea using bathroom scales

 

[JumbleDuck]

I bought a filter mask for welding galv metal. The fumes really are horrible.

There was a case of serious injury, and perhaps a fatality, when an unwary volunteer on a heritage railway tried to weld up a framework using old galvanised point rodding.

 

[John the kiwi]

Welding galvanized steel is quite possible, and frequently done.
If not removed, a cloud of zinc oxide is emitted as the zinc vapourises. (zinc oxide is white, and in sunnier countries is the principal ingredient in sun blocker. Its the bulking agent used in many cosmetics, is a UV stabiliser in tyre making and has many other uses) This can cause an ill feeling. Older welders call this "Galvy Flu", and they used to drink milk before and afterward to stave off the effects.

The simpler solution is to grind off the zinc with an angle grinder before repairing the weld.
The welding will destroy the galvanizing in the heat affected zone, and this area will then be subject to corrosion. But the most common thing to do there is to immediately paint the weld area, best using zinc rich paint.

As an apprentice we had it written in our union rules that we could have as much free milk from the company cafe as we wanted when welding galv steel.
Riboflavin is the antidote to zinc fume fever which feels like a heart attack at 1 am the following morning. (ask me how i know!)Riboflavin is found in milk and beer, but they wouldnt supply free beer though we did of course ask.
Used to upset the cafe ladies as it upset their milk planning. Funnily enough in those days no one even thought about a respirator.


Welding of course burns off the zinc. While it is still hot from welding it is possible to rub a zinc stick on the weld zone and spread it with a wire brush. Restores some protection anyway.

 

[JumbleDuck]

As an apprentice we had it written in our union rules that we could have as much free milk from the company cafe as we wanted when welding galv steel.

Metal fume fever

Many welders report flu like symptoms after welding. The effects are often worse at the start of the working week. Metal fume fever is usually linked to welding or hot work on galvanised metals. High exposures to mild steel weld fume can also cause this illness. Metal fume fever does not usually have any lasting ill effects. Don’t believe the stories about drinking milk before welding. It does not prevent you getting metal fume fever.​

http://www.hse.gov.uk/welding/illness.htm

 

[Avocet]

Those rubber suspension units are pretty hard at the best of times. The smallest ones they do are way too stiff for our little Heron dinghy. It doesn't help that they get disproportionately stiffer as the wheel rises up too. Depending on what you weigh, don't be surprised if you see very little movement when you bounce on the trailer. I weigh 100kg and they barely move. A Wayfarer is a fair bit heavier than a Heron though.

One thing that I think is important, is to make sure as much of the boat's weight as possible is on the keel rollers - maybe even add a few extra. The side rollers (or pads), should be free to pivot to follow the shape of the hull, and ideally, should feed the loads into the hull over a wide area (directly below something stiff like the edge of a buoyancy tank if possible) AND only really just touch the underside of the hull to stop it flopping one way or the other. The keel should take almost all the weight.

Lastly, I think it can do a boat more damage to NOT tighten it hard down on the trailer. The worst shock loads are when the boat is lashed freely enough to be able to lift a tiny way off the trailer on bumps. (That might not apply to a wooden boat though).

 

[Lakesailor]

Another thing to be aware of is the tyre pressure. Whatever it says on the sidewall, 25 psi is too hard for a dinghy on a trailer. Try 15 psi or less. The tyres are not taking any steering, driving or braking stresses.
I ran my trials car's driven wheels at between 2 and 5 psi (tubeless). That weighed 420 Kgs plus two crew.

Just don't have the pressure so low that they look underinflated.


As for weighing. To be absolutely correct you should have the other two weighing points chocked to the same height as the scales and just move the scales and chocks around to weigh each point. That way the trailer doesn't change attitude as you weigh each corner.
If it's too heavy for the scales, use a pair with a beam between. It works remarkably well. Check on a weighbridge at your leisure.

[

 

[William_H]

To test the suspesion units just observe the motion of the arms as you jack up the trailer body. (with boat on) As you take the weight off the suspension you should see a large amount of movement. Something like half the total available movement of the arms. If there is no movement ie the tires lift off the ground immediately then the suspension is either too hard or seized up. I wouild think with a dinghy if you get someone to put their weight on the side of the trailer/boat you should see some movement of the supension ie 100kg added to one side.
As an asside the mass of the boat should rest on the keel. The side supports are simply to keep the boat upright and stop rocking. The side supports should be udjustable in height and adjusted to take just the slightest pressure on the hull. good luck olewill

 

[FairweatherDave]

More good advice, thanks. On the tyre pressures I am on it having trailed a fair bit using the advice on the Wayfarer forum and handbook. This can be summarised as I prioritise avoiding a blow out at all costs (over the well being of the boat). Therefore I monitor the temp of the tyres, warm is good but hot is not. I am towing on good fast roads 700 miles with a heavy load and safety is my only consideration. I can do the suspension tests once I get the boat back on the trailer. My only other worry is who our neighbours will be on the campsite (but they should be worried too