Trailer, extra large keel roller bracket/u-bolt ?

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m1nder

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The old trailer belonging to my N17 has a central steel beam, 100mm wide by 50mm high, hollow. I need to fit new keel roller brackets but cannot source bracket/u-bolt combinations any wider than 80mm (bolt hole fitting)

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I could drill through the beam top and bottom and run individual bolts to hold a keel roller bracket but then I loose the ability to move and adjust it along the beam to suit the keel curve.

Can anyone help me with suggestions as to what I can do here?
I have searched the web black and blue.
 
Rollers mounting

Firstly you need to look at that tubing very closely. Square tubing is horrible for boat trailers because it can rust from the inside out. My boat trailer had square tubing draw bar which broke with 2 years of construction.
I now pour old oil down the tubes regularly to try to discourage rust.
Mine has spine of 2 pieces of angle iron set apart from one another with rollers simply between the angles on axles. Yes it is is straight and the keel is curved so many rollers don't support weight when boat is in place. However this has not been a problem.
The advantage is that the keel is then as low as possible to the road for more stability and the possibility of floating the boat off in shallower water. So you might consider redesigning the backbone of the trailer.
The other real advantage is that by removing rollers you can make a gap to enable the keel to be lowered. If it is a sail boat.

If you want to stick with it as is I would suggest easiest is to make triangular steel plates to bolt or weld to the sides of the spine high enough to take the roller axle with the roller clear of the spine. You may be able to predict the height of the rollers that you need to match the keel curve.

I would think that any roller brackets will end up with the keel and so the whole boat higher than is really necessary. good luck olewill
 
The secret to preventing internal rusting on square tube (or round tube for that matter) is to weld caps over them to make 'em air-tight, and thus water-tight. If you have any doubts over the integrity of your welding, then drill one small hole and super-glue a car tyre valve over it - pump up the tube to (say) 5-10 psi, and watch the gauge for half an hour - it shouldn't move - if it does, a few drops of washing-up liquid in water will soon show up any pin-hole leaks (bike puncture style ...). But don't forget to put a weld bead over that hole afterwards ... (!)

To make oversize 'U-bolt' equivalents, simple make up 2 plates wider than your trailer spine (say 150mm) from 5-6mm plate and drill 2 x 10mm holes in 'em, leaving (say) 1 or 2 mm for clearance, One plate top, one plate bottom, 2 (or 4) 10mm through bolts connecting 'em - and this will then slide along your spine a treat (after you've dressed it, of course). A couple of spot welds on each bolt head will make adjustment a breeze.

Or, you could simply make-up some 100mm 'square' U-bolts from 2x 10 x 100mm bolts and some gash 10mm rod. You'd still need the top plates, though. And the advantage of having large thick plates on the top surface is that you can then weld stuff directly onto 'em.
 
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I hate to criticize trailers, mainly because my own is pretty poor, and I know you have to work with what you have. But whoever designed and built that wants shooting.

They have put the rectangular box sections flat, which is the weakest orientation. they really should have been upright. And the way it's welded together, the spine is not one continuous length, but 3 sections. The middle one being "sealed" so any imperfections will let water in, where it will stay and rust from the inside.

I'm not a supporter of the sealed theory. When renovating my own trailer, all the open ended sections of tube seem structurally fine (and it's easy to flush them through with fresh water after each dunking in the sea) But on my own trailer, the winch post had been formed as a sealed section with plates top and bottom. That clearly wasn't as watertight as intended and it had rusted through at the bottom where clearly it had filled with water that then could not get out.

Having said all that, the tubing hasn't bent yet so is standing up to the job so a good scrub up and re paint and it will be fine.

And the post above has given the suggestion I was going to about making some plates that clamp round the spine, onto which you weld your keel roller brackets.

Re the sealed section, I would be inclined to drill a small hole in the bottom to let water out, and squirt a good amount of oil, or better still (if it's still available) waxoyl which was designed for treating box sections on cars to prevent rusting from the inside. IIRC it comes as an aerosol that you can squirt through a small hole. Perhaps also drill a hole in the top so you can flush through with fresh water.

And don't forget some mudguards so Mr plod doesn't get interested in the trailer.
 
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A lot depends on the weight and keel configuration of the boat, and whereabouts the weight of the boat is supported. I have a dinghy trailer of similar design (open sections though) and although most of the weight it taken on the keel, there are supports close to each wheel that the chines rest on. Every time a wheel hits a bump, it sends the shock straight into the chine.

I'm not a big fan of using closed sections for trailer chassis - even when sealed at both ends. Tubular sportscar chassis tubes are usually welded up like that and they still rot from the inside.
 
As it's a motor cruiser the whole of the weight will be supported on the backbone and the pads near the wheels will just be to keep it upright.
(see original thread)

I'd certainly check the weight of the trailer as the boat seems to be about 340 Kgs without motor and whilst the law allows up to 750 Kgs without brakes it may be that you vehicle manufacturer has set a lower limit.

I agree with the suggestion to use two plates top and bottom of the chassis with bolts between them. Just weld the roller bracket to the top plate.
 
Folks, many thanks for all the great replies. At this stage I am debating whether to go with a new / sh trailer purchase.

How do I determine the weight of my boat though? It's an old Norman 17 currently under restoration. What type of trailer would you recommend? Cost is a SERIOUS constraint.

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m1nder said:
Folks, many thanks for all the great replies. At this stage I am debating whether to go with a new / sh trailer purchase.
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Provided you can weld ok, I'd use the trailer you have. The square tube is the correct way around: what is important is to minimise lateral deflection in use, which is what that configuration does. Together with those gussets (good to see someone knew what they were doing), I'd say that trailer is well up to the required job - I bet it's seen some service already ...

If the tube was rotated through 90 degrees, then you'd need to either use a V-drawbar configuration, or fit additional diagonal struts, to prevent lateral deflection of the drawbar.

What people forget is that the weight of the boat is principally taken over the axles. All the drawbar needs to accomodate (in the vertical plane) is the nose weight, plus the downward weight when braking hard - which is somewhat less with a 4-wheel trailer, than with a two-wheel.

In the unlikely event of vertical deflection (bending) of the drawbar or spine, it is standard practice to strengthen such beams by welding a vertical strip along their undersides, covering approximately the middle two-thirds.
I have an Indespension 'how to build a trailer' book somewhere with all those kind of details, if you need more info.

I'm currently in the process of building a trailer-trolley combination for a small commercial workboat, and am using 2 lengths of scaffold pole for the drawbar - that's pretty-much equal to 4" x 2", although they're spaced 4" apart, so it's slightly stiffer than your configuration, but has similar properties vertically.
 
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The simple answer to the U bolt question if you cant get anything that fits, is to obtain ordinary bolts of suitable size, and make up steel plates wide enough/ strong enough to hold them each side of the chassis member. Make up plates for top and bottom then weld or otherwise fasten the rollers to the top plate. I have used angle iron for the plates to stop them bending - but mainly because thats what I had lying around!
 
Looks pretty knackered to me, i would take it somewhere to get it sorted or buy a new one. Cops are really hot on trailers recently.
 
m1nder said:
Folks, many thanks for all the great replies. At this stage I am debating whether to go with a new / sh trailer purchase.

How do I determine the weight of my boat though? It's an old Norman 17 currently under restoration. What type of trailer would you recommend? Cost is a SERIOUS constraint.

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If you read the post above yours (No #6) I have told you the weight.
All you have to do is Google it.
 
Lakesailor said:
If you read the post above yours (No #6) I have told you the weight.
All you have to do is Google it.
Click to expand...

I had assumed that you took a guess at the weight, going by your wording "seems to be about..." Then I asked the question "how do I determine the weight?" and after a few searches...the answer to that question would appear to be "by consulting the manufacturers specifications".
 
Reading your blog, it seems you had damage to the fibreglass hull at one point caused by the trailer pressing on one point.

That needs looking at. Perhaps the whole weight is being taken by just 2 of the keel rollers? Perhaps you need more of them? But then again I think that's what this thread is all about.

For my own trailer, I have fitted new and bigger rollers, and spaced them differently so that (if I got my measurements right) I will now be able to lower my lifting keel while on the trailer.

I assume you removed the boat from the trailer just by jacking it up then pulling the trailer out. I suggest when you have fitted the rolllers you do the reverse so you can let it down gently, and adjust the position of the rollers before the whole weight of the boat is on the trailer.

Looking at the picture above, it looks like the boat has two little stub keels either side of the main spine. I would want to get some rollers under those to take some of the weight as well.
 
m1nder said:
I had assumed that you took a guess at the weight, going by your wording "seems to be about..." Then I asked the question "how do I determine the weight?" and after a few searches...the answer to that question would appear to be "by consulting the manufacturers specifications".
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Sorry. I sounded a bit curt there.
The reason for saying "about" 340 Kgs was that they said it was 335.66Kgs, with the best will in the world, hand-laying up a boat can't be so accurate. (I think they just converted the imperial weight)
 
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