I realised that we are not going sailing this summer without a new trailer. Our boat was first launched in 1978 and since then it has had two trailers. The first trailer corroded until it eventually collapsed while driving along the road - fortunately no harm done, it just scraped a bit on the tarmac until we were able to stop. The second trailer has now rusted to the point that I dont think it is safe - trailers tend not to last as long as boats. The second trailer was hot dip galvanised but even so it corroded inside the square hollow sections.
The third trailer will not be galvanised but it will not rust inside because plates will be welded over the ends of the tubes so water will never get inside. Never ever. Outside will be epoxy painted.
The pictures show the parts for the trailer now about ready to stick together, just setting them out with clamps to hold in place to check everything fits. The picture above shows the general idea. There will be a roller behind the cross member, I need to buy the rubber roller before I can make the brackets to hold it. There will also be rubber pads on the cross member where the rubbing strakes under the boat rest on it.
Second picture shows the raised supports for the suspension units which fit above the cross bar, not underneath as on our previous trailers. This means the cross bar is 100mm lower, which I think will make it easier to get the boat on and off. The bent plates on top of the short vertical posts will support wooden pads to fit under the hull and guide the boat onto the trailer, also the tops of the mudguard will attach to these. This photo also shows the joint between the cross bar and the central bar which comes apart with two bolts. Reason for that is 1) there are increasing numbers of waterside car parks that ban the parking of boat trailers, so by taking it apart we can hide the pieces under the car. 2) We sometimes make long journeys without the boat on the trailer, in which case I prefer to have the trailer on the roof rack. This makes reversing easier, its hard to reverse the boatless trailer because you cant see it, also it avoids the problem of an unloaded trailer bouncing on the over stiff suspension. We sometimes carried the previous trailer on the roof rack but having it in two pieces should make it easier.
Third picture shows the front end, temporarily held in place with clamps. There are turned bushes with tapped holes that fit through the hollow section to mount the tow hitch and jockey wheel, this is to keep the hollow section watertight. The boat has a hole right through the bows just above the waterline. In the past we have used this to tie the boat to the trailer with bits of string, which was always a fiddle. The new trailer will have two plates forming a fork to guide the bow into position and the metal bar will then fit through these plates and also through the hole in the bow of the boat to lock the boat to the trailer. I think I will put a plastic pointed piece on the end of this bar to make it easier to thread through and it will need something like 'R' clips to keep it in place. This trailer also has a small winch, we have managed without one in the past but I hope this will make things easier now that we are getting old!
On 15 Mar 2014 at 6:45, John P [via UK HBBR Forum] wrote:
> The third trailer will not be galvanised but it will not rust inside
> because plates will be welded over the ends of the tubes so water will
> never get inside. Never ever. Outside will be epoxy painted.
How will you make the spine watertight where the various bolts pass
> The pictures show the parts for the trailer now about ready to stick
> together, just setting them out with clamps to hold in place to check
> everything fits. The picture above shows the general idea. There will
> be a roller behind the cross member, I need to buy the rubber roller
> before I can make the brackets to hold it.
I have a number of rollers from my trailer that are now surplus to
requirements as I rather over-specified at the design stage. You are
welcome to some if you want them. They are solid rubber, a nominal
60mm OD, 15mm ID & 200mm long (though they can easily be cut
Hoping for calm nights
Hi Alastair, your rubber rollers sound like just what we need. However, I would only need one roller and I am wondering whether postage would cost as much as buying a roller from one of the trailer shops here in Plymouth. Petrol to drive to your place and back would certainly cost more than a rubber roller, but if we happen to be coming your way or you coming our way it would be a thought, so thank you for your kind offer.
Re the holes in the 'spine', if you look at the lower picture and press 'ctrl +' a few times you will see that there are turned bushes fitted through the spine at the tow hook end. These project on one side, to allow a good fillet weld. On the other side I turned a small shoulder at the end of the bush to locate it in the hollow section and also turned a 2mm x 2mm chamfer on the shouldered end of the bush and made a 2mm x 2mm countersink in the 3mm wall thickness of the hollow section. This makes a Vee groove that I hope will be filled by a full pen weld, so that when the weld is ground flush with the wall of the hollow section there will still be adequate weld to make a seal. Should be sound structurally since the shoulder would stop the bush coming out even if the welds failed. Each bush will have an M10 hole for the bolts to hold the tow hitch and the jockey wheel, I drilled the tapping holes on the lath but will leave the threading till after welding so that weld metal does not damage the threads.
At the cross bar end of the spine there are two bushes that pass right through, fixed with fillet welds each side and bored right through for bolts. The idea of the strange looking connection between spine and cross bar is that it will slip together with clearance fits to avoid damage to paint, but when the two bolts are tightened the clearances will close up making it rigid with the diagonal braces and packing pieces supporting the joint if, for example, a wheel hits a curb.
Hope this not too confusing!
Are you coming to the AGM in 2 weeks time? Can you wait that long?
That's all clear enough, I am still not convinced that you won't end
up with tubes with water in them, that can't get out because they are
watertight (like is usually found with sealed buoyancy tanks).
My preference would be to put a plug in the top of the tubes and use
them to store old engine oil.
Or use I or C sections.
My preference is to make boat trailers from aluminium, with stainless fasteners and chromate paste:
Coupled with sealed (actually submersible) LED rear lights the only corrosion I need to worry about is the bearings, wheels and suspension units.
Makes for a very light trailer, too, but, because aluminium is less stiff than mild steel (but about the same strength) the design does need bracing to make it stiff enough.
This post was updated on .
Hi Alastair, Yes we do intend to come to the DCA AGM on 29 March, I expect a few others here would be interested in that given that there will be a talk by none other than Francois Vivier during the morning before the AGM. I think you should be a member of the DCA to attend, but it's not so expensive. And the earliest we are likely to go sailing this year would be 3rd May, so if you could bring us a rubber roller when you come to the AGM we would certainly be grateful for that.
Used engine oil in the trailer frame is a thought, but if your doubts about the welding do turn out to be justified I would not want the mess on our drive! I suppose if I could fit a tyre valve into the tubes somehow I could check that the tubes hold pressure, but not sure it is really worth the trouble. I thought the reason buoyancy tanks leak is because people fit them with inspection hatches?
Jeremy, that does look a really nice trailer you have made. I agree that aluminium would be an excellent material to use, maybe my trailer number 4 will be aluminium! Even though you would need extra stiffening, or larger sections to allow for the lower modulus (greater flexibility) it should still be quite a lot lighter. I was wondering how you joined the parts for that trailer, nuts and bolts, rivets or welding?
Yes, some grades of aluminium alloy are stronger than mild steel, but not all. The hollow sections I have used are Corus Strongbox 235 - min yield strength 235MPa. There is also Hybox 355, min yield strength 355MPa, needs different electrodes I think. The most readily available high strength aluminium alloy is probably 6082 in the T6 condition, proof stress 290MPa so intermediate between the two main grades of hollow steel section. Most other aluminium alloys are less strong than 6082, some much less. I once worked for a firm that used a lot of aluminium for strength critical applications and we tested all the batches of ally as they were delivered and it was not all that unusual to have to send material back because it did not actually meet the strength requirements for the specified grade of heat treatment. Also, if you intend to weld ally you need to take account of the loss of strength in the heat affected zone - that varies quite a lot from one alloy to another. Also probably best to use TIG welding? And, given a good factor of safety, mild steel is very reliable in a fatigue situation. Even so, aluminium is an attractive material for a boat trailer. Titanium would also be nice.
I noticed this firm on the other side of the world is making nice trailers to fit their trimarans, they have a fibreglass shell moulded to fit snug to the boat hull, aluminium frame and wheels and stainless steel brakes. http://www.f-boat.com/pages/News4/FM-Factory2014.html
That trailer is made from 6082-T6, which is both easy to buy and relatively strong, the downside being the relatively low Young's Modulus of aluminium, which does mean either using bigger sections or adding bracing,. when compared to steel.
The trailer fastenings are all a mix of stainless bolts and stainless pop rivets, so no welding (with the consequent problem of needing to re-heat treat and age the 6082 to get it back to T6) and easy construction with just a saw, drill, rivet gun and some spanners. This is the fourth trailer I've made from aluminium like this, the others were used to trailer home built light aircraft. Here are some detail shots of the construction:
To provide local internal stiffening at places where bolts pass through the 2" x 2" x 1/8" square tubes, I slid lengths of 44mm x 44mm x 6mm pultruded glass fibre box section inside the alloy. I also beefed up the axle tube along its whole length in this way.
The trailer is very light, I can easily pick it up with one hand and hang it on its side on the garage wall to keep it out of the way when it's not being used - the heaviest parts are the wheels and suspension units. It takes a boat up to about 18ft, as long as the total weight is within the 450kg limit of the suspension units.
Your craftsmanship is excellent.
Given ally is so easy to work is it possible to retrofit a galvanised trailer with a custom ally roller system?
I can't recall the electro chemical potential problems back in 1976 A level chemistry!
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In reply to this post by John P
Easy enough to make a cradle to fit your hull, if you can turn the boat over.
With hull upside down: drape nylon carpet or whever you want to use for packing in the right place on the hull; lay up 'glass on top; add stiffening where needed ("rope" 'glassed in); add brackets to fit trailer; et Voilá!
I probably should have read through this more carefully
But what about all those lovely regulations so kindly donated by the EU and gift wrapped by the DVLA that say any new trailer has to have a formidable array of parameters and state them on a little plate?
I only ask because I've thought of making my own to help sell 'Rosie Mae' apart from anything else....
Anyone have a small second-hand trailer up for grabs?
I expect the Type Approval regulations of boat trailers will be adhered to with the same enthusiasm as the RCD.
It only applies to new trailers, once they have been dunked in the briny a couple of times they all look old.
To be honest by the time you add up the cost of all the constituent parts it just might be as cheap to have one made, although I haven't priced it.
I seem to have made a slight slip of the keyboard in describing this as a new trailer in the title of this thread - its actually a refit of a rather old trailer. Having said that, if it were a new trailer I think, from a quick and possibly incomplete perusal of the rules, that it would be compliant and it would only cost £75 for an inspection and a bit more to have a proper manufacturer's plate made up. Not sure though if it is OK to have an individual's name on the plate rather than a company.
I think the rules do require a way to mount lights on the trailer when there is no boat on it, but that's something I was meaning to do anyway, just haven't yet worked out the best way.
Graham, I am sure you are right that if you were to add up the cost of all the bits, the steel, the welding consumables, the paint etc. a refit project of this kind could cost at least as much as just buying a new trailer, but that's not the point is it - we all know that we could buy a boat, second hand maybe, for less money than we spend on the materials to make boats ourselves.
Over the years I've broken, forgotten to tie on, dunked in water etc more trailer light boards than you can wave a big stick at. Rather oddly I keep a few of the broken ones around, in the vain hope that I'll have a enough salvaged bits to make up a new one.
For my last trailer (the one pictured above) I decided to splash out on completely sealed LED lights. These can be immersed in water without harm (as long as the wiring connections to the 7 way cable are suitably sealed). I fixed these to the trailer so they are visible when the boat is on it (the boat overhangs the lights though) and so never have to worry again about fixing the trailer light board on, or having the cable dangle down and wear through from dragging on the road.
I sealed up the wiring connections to the 7 way cable using soldered joints and adhesive heat shrink sleeving, which makes for a waterproof connection. All the joints are inside the tube the light plate is riveted too.
Although the LED lights were expensive, I thought it was a price worth paying for the peace of mind and convenience they give. The only snag with them is that they don't draw enough current to work the "trailer connected" warning beeper inside the car when the indicators are working, but there is a fix for that by adding load resistors across the LED indicators so they draw enough current. I've not got around to doing it yet................
Jeremy, is the FRP internal section to protect against bolts crushing the tube or to provide stiffness/strength along the tube?
It's mainly to prevent crushing, but does add a fair bit of stiffness, too. I only really used it as I happened to have a few lengths of 44mm x 44mm x 6mm pultruded FRP box section spare, and, by happy coincidence, this was a nice snug fit inside 2" x 2" x 1/8" alloy box section.
An update on my trailer project. We have now used the trailer to tow our boat to various parts of Ireland as well as some local trips in Devon, so it has already covered quite a few miles. Generally it has worked out fine.
The low ground clearance resulting from having the suspension units above, rather than below, the cross member does make it easier to launch and recover the boat. I had been anxious that this clearance would be too little, but in practice there has been no problem even on some of the rather bumpy roads in Ireland. Measuring the ground clearance I find that it is actually a few mm greater than that of our Ford Fiesta car, I think most cars do have slightly more clearance though.
The boat is secured to the trailer by inserting a 20mm diameter tubular steel pin through the guide arms at the front of the trailer and through a hole that passes right through the hull of the boat near the stem. Back in 1978 the boat was built with this hole in the stem with this in mind, but until recently I have not had a trailer to make use of the feature. I think this method does provide a simple secure attachment between the bow of the boat and the trailer. I have discovered that it is necessary to remove the pin before the hull starts to float when launching and fit the pin after the boat has stopped floating when de-launching. When the hull starts to float it tends to move about and the pin then jams and is almost impossible to move.
I do still need to make a couple of improvements. The boat was built with two shallow 'runners' on the bottom and these runners take the weight of the boat when it is on the trailer, or dried out on the seabed. The runners are shod with stainless steel and at present the steel rests on rubber pads fitted to the trailer cross beam. I find that the stainless steel soon wears away the rubber. When the rubber was new it was 12 mm thick, now it is about half that. Maybe rubber reinforced with some kind of fabric (like a conveyor belt or a tire) would be better but I think I will order some nylon blocks and machine nylon pads to bolt onto the trailer. The other thing is that the roller on the trailer needs to be about an inch higher to so as to lift the boat enough that the runners under the boat can more easily slide onto the trailer cross beam. This is going to need more welding, a bit of a nuisance after the whole trailer has been carefully painted. The problem arose because I designed the trailer so that the supports for the boat accurately fit the cross section of the hull at the position it will sit when on the trailer. What I somehow forgot about is that the hull needs to move through a whole series of positions as it moves on and off the trailer and the supports on the trailer have to clear the hull in all those intermediate positions!
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