Using a caravan chassis as a boat trailer

bikerbill

bikerbill

Well-Known Member
Joined
16 Dec 2012
Messages
1,309
Visit site
Hi all

I have a Hurley 20 with bilge keels but with no trailer. I have the chance of an 18 foot caravan chassis that I am thinking of using as a trailer. Would this type of trailer be suitable? I know that I may have to 'fettle' it a bit. What I am unsure of is, would the trailer hold the weight of my yacht which is around 1100kg? and how can I check this?

Thanks in advance

Billy
 
You'll have to make some fairly major changes to the chassis. They are designed to gain their stiffness from the floor which is a composite of timber/foam/plywood.
I have one I am converting to carry my trials car which only weighs 400Kgs. Once you have removed the caravan floor the side frames (all there is) of the trailer are very flexible about the point the axle fits in. I have put some extra cross members in and am going to re-deck it in Phenolic Ply. This will be bolted all along the top of the side members.
You mustn't weld the existing side frames. Only bolt to it.
My chassis has a maximum trailer weight of 1000Kgs. This is marked on the back of the axle beam. I think there are 1300Kg chassis, but I think that greater weights will probably be 4 wheel ones. I wouldn't think a caravan chassis was really up to towing a boat. Too much weight in one place and the CoG will be quite high leading to a lot of flexing.


As it was when I bought it. The floor was pretty rotten so you couldn't try to use that.

Caravanchassis01.jpg



With the floor removed and three new beams bolted across. (cropped from a bigger picture)

Caravanchassis02.jpg
 
You can do it, if you aren't too bothered about appearance the cheapest option is to leave the ply deck on. However, this makes the trailer buoyant...

I used canal slipways with my 19' Dawncraft Dandy, pertty well flat bottomed and the angle meant the trailer did not float away. (Especially with offspring sent to stand on the far corner-)

A better bet which I used later with my bk Seawych was to buy a cheapie car trailer, no work to do except for docking arms.

Nick
 
Cheers Lakesailor, Yeah, I thought the caravan trailer I looked at was bit flimsy and that I would need to reinforce with box sections or angle iron. Will need to google to source steel box sections and U bolts etc.
 
Cymrogwyllt said:
How many trailer launched boats get their bearings re done each launch?
Click to expand...

Good question.:rolleyes: When I had the RHIB, the trailer had sealed bearing hubs, though I did remove and regrease the bearings every 3 months just to be safe. I don't think this caravan trailer will have sealed hubs, so will need to have a think as to do this.
 
With bilge keels you will need to add another beam in addition to the ones I have just behind the axle. The keels will probably need to sit over the axle, which would be handy as it would remove a lot of the twisting motion that a weight near the back of the trailer would have.
I use secondhand scaffold boards for my tracks for the cars wheels. In fact I may use them again instead of the plywood I mentioned. They are very stiff and bolted to the side rails and the new beams will provide all the stiffness I need. At about £5 each they are good value.

My current trailer

Backwheelpad03.jpg
 
Caravan chassis are made with a lot of good stuff, but and it is a big but they are not stressed for the sort of loads you get carrying a boat, even if the main parts, the A frame and axle(s) are suitable for the weight. All caravans have a weight plate which will tell you the max weight they were designed for if this is not more than the expected weight of your 'new' trailer plus your boat then it is a complete non starter.
 
TRAILER.

Yes it can be done quite easily, but use a four wheel caravan chassis. Make up a frame similar to a cradle from 60mm box section to suit your boat with the side rails the same width as the side of your trailer, then bolt the frame to the chassis. weld two pieces of channel across the two axles for the keels to rest on.
I have done this very successfully for to transport an Achilles 24 fin keel.
 
BERT T said:
Yes it can be done quite easily, but use a four wheel caravan chassis. Make up a frame similar to a cradle from 60mm box section to suit your boat with the side rails the same width as the side of your trailer, then bolt the frame to the chassis. weld two pieces of channel across the two axles for the keels to rest on.
I have done this very successfully for to transport an Achilles 24 fin keel.
Click to expand...

The OP needs to be extremely careful welding to the axles - many of them are stuffed with rubber as the springing medium - usually a goof foot, maybe even 18" from each end.

Also, won't any caravan chassis capable of carrying the weight be WAY too wide for the keels? Obviously, it wold be nice to get the keels as close to the axle mounting brackets as possible to minimise the bending load in the axles themselves I guess.
 
Lakesailor said:
With bilge keels you will need to add another beam in addition to the ones I have just behind the axle. The keels will probably need to sit over the axle, which would be handy as it would remove a lot of the twisting motion that a weight near the back of the trailer would have.
I use secondhand scaffold boards for my tracks for the cars wheels. In fact I may use them again instead of the plywood I mentioned. They are very stiff and bolted to the side rails and the new beams will provide all the stiffness I need. At about £5 each they are good value.

My current trailer

Backwheelpad03.jpg
Click to expand...

Is that Unistrut or its equivalent that you have used?

I have used the double section on our trailer and it really beefs up the main bunk supports for the boat. It comes ready galvanised and is available with all the fittings ,bolts and zebedees so that you just have to drill the chassis and bolt it in place.
 
http://www.solentribster.com/towing_requirements.htm


Check out the above web site and others and read the SI notices referred to.....A few Jobsworths seem to be getting up steam to make home built trailers more fit for purpose.

One consideration is that the weight of your boat and the reinforcement may make the gross weight a lot greater than the caravan and so the actual suspension might need to be looked at. Maybe new springs or Indispension units and possibly even different wheels and tyres.
 
I used an old caravan chassis but it had a 8 inch "H" or "I" beam laid on its side over the entire length. Used the original leaf springs but later fitted Indespension units. Present trailer is a car transporter with two angle irons along the length and rollers bolted to them. This supports the main keel. The Bilge keels are supported on wooden beams running on the car tracks.
 
Avocet said:
The OP needs to be extremely careful welding to the axles - many of them are stuffed with rubber as the springing medium - usually a goof foot, maybe even 18" from each end.

Also, won't any caravan chassis capable of carrying the weight be WAY too wide for the keels? Obviously, it wold be nice to get the keels as close to the axle mounting brackets as possible to minimise the bending load in the axles themselves I guess.
Click to expand...

I'm not planning on welding near the axle, prefering to use U bolts in case of minor adjustments. I have taken stress/bending under load into account and the load capacity of the axle. Since the boat is 1100kg, I am looking for a load capacity of at least 1500kg to be safe. However, a twin wheeled trailer looks like the better option of course. The caravan chassis I looked at was 5 feet between both wheels, so I think the keels should fit ok, but will need to get the diving gear on to measure the distance between the keels to be sure. Gives me a chance to give the hull the once over as well.
 
Bilgediver said:
http://www.solentribster.com/towing_requirements.htm


Check out the above web site and others and read the SI notices referred to.....A few Jobsworths seem to be getting up steam to make home built trailers more fit for purpose.

One consideration is that the weight of your boat and the reinforcement may make the gross weight a lot greater than the caravan and so the actual suspension might need to be looked at. Maybe new springs or Indispension units and possibly even different wheels and tyres.
Click to expand...

Complete barstewards wanting trailers to have brakes that stand half a chance of stopping them and lights that people can see! I mean where's the fun in that?!
 
bikerbill said:
I'm not planning on welding near the axle, prefering to use U bolts in case of minor adjustments. I have taken stress/bending under load into account and the load capacity of the axle. Since the boat is 1100kg, I am looking for a load capacity of at least 1500kg to be safe. However, a twin wheeled trailer looks like the better option of course. The caravan chassis I looked at was 5 feet between both wheels, so I think the keels should fit ok, but will need to get the diving gear on to measure the distance between the keels to be sure. Gives me a chance to give the hull the once over as well.
Click to expand...

Most caravans over 1500kgs are twin axle. Remember your boat will already weight more than the manufacturers weight and you will have to factor in the weight of kit etc, and remember the anchor and chain. For my last trailable boat we added 20% to the rated weight to some margin and then rounded thins up
 
Check that car insurance will cover a 'home made trailer'. Just renewed our car insurance and it will only cover bono fide makes!
 
You must log in or register to reply here.

Other threads that may be of interest

E
Is this any use as a kedge?
Replies
15
Views
595
noelex
noelex

Share this page

Top