Converting trailer to Roller-coaster

slig

slig

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I have a standard (fairly new) trailer with 2 boards and keel rollers for my 20ft long Shetland 570 cruiser.

I am having problems retrieving the boat, back swings around when first keel roller connect, slipping off the rollers and generally not being very co-operative.

I had the brain wave of converting the trailer to a roller coaster trailer by removing the keel rollers and replacing the boards with a bank of rollers and putting another bank up further. Anybody done this before? Can anybody see any potential problems with this setup?

Anybody know where I can get rollers at a reasonable price?
I have searched the internet and while I have a few results they are mostly in the US or on fleabay.
 
Perhaps most valuable for guiding the boat on are guide posts set up at the back corners of the trailer just wide enough for the max beam and reaching above the gunwhale. From the corner of the posts you could set up angled rollers to help force the boat into the middle. But neither of these work until the boat max beam reaches the back of the trailer.
The p[osts are also useful to enable you to see the trailer when backing in.

Where I recover my t/s there is a jetty next to the ramp (and trailer) I have someone on the jetty with a rope in one hand and a long boat hook in the other. This person can easily push the stern away or pull towards the correct position while I give orders and crank the winch. A person either side with long ropes to the shore might work nearly as well.
The side bunks can be replaced with rollers to some advantage in ease of winching on but essentially they should be set up with enough gap so the keel rollers take the weight while the side bunks simply balance the boat.

Basically I think you might check your technique or take more advice before modifying the trailer. Yes it is the least fun part of trailer boating.
good luck olewill
 
Hi Slig.

If you will always have two people available for recovery onto the trailer then technique will serve in most conditions.

If you want to recover single handed then :

If you have a backbone trailer, you need to fit a pair of wheelbarrow wheels at the back to capture the bow. Height has to be considered for when the boat is fully on. Doesn't work for "bathtub" shaped boats without a sharp forefoot. Only solution for this type of trailer but not as good as next option.

If you have a perimeter frame trailer then you need a swinging cradle to replace the rear crossmember. The cradle will carry the wobble wheel pairs you are thinking about. There are structural considerations and the cradle will have to be custom made unless the manufacturer of your trailer has a stock item to fit both the trailer and the bows of your boat. Roller height can usually be adjusted but the angle of the V in the cradle and the length (accross the trailer) of the cradle cannot.

Properly set up this can solve all your problems but you may be better off buying new.
 
Buying new really isnt an option, I live in Ireland where anything marine related is about 50% more expensive than in the UK e.g The trailer I have cost £1000 in the UK while a comparable one here was between €2500 - €4000.

The trailer is framed but has no v crossmembers just straight.

Where would I mount the wheelbarrow wheels? The bow will get up about 2 keel rollers before the back swings out.

If I reverse too deep then you cant see the trailer from the boat, too shallow and its difficult to keep it coming up straight.
I have tried connecting the winch and hauling up the boat but again its inclined to slide sideways off the keel rollers and scrape the keel off the roller brackets. I believe my problem is that the boat is very front heavy.
 
I'm thinking that thats the best option so far, couple of lenghts of galvanised gun barrel, 2 brackets and something to cushion them. I might even mount the lights on them to get rid of the lighting board.
 
Hi Slig.

The trouble with docking bars is that they only really help once the boat is well onto the trailer and they will only keep the boat lined up well if you have four of them. They work best if the boat is floated on and you should try to avoid this method of recovery.

If the trailer has brakes it should never be immersed. If not, your ungavanised wheels, suspension parts and wheel bearings will last longer if you stop whith the tyres only in the water and winch the boat on.

Assuming that the boat has some degree of "V" to the hull the first thing to try is this.
Get longer axles for the keel rollers (only steel bar cut to length and drilled for split pins). They should be long enough to accomodate a pair of rubber (not plastic) dolly rollers fitted each side, outside of the keel roller supports. The dolly rollers should be a couple of inches greater in diameter than the existing keel rollers. You may be able to find a trailer manufacturer who will sell you all the bits you need for this.

The Wheelbarrow wheel system requires a support such that the axle for these wheels is lower than the axle of the keel rollers. Typically it would be drilled through the backbone but you can't do that if there is no backbone.

Below is a picture of a Dutch hybrid trailer. It has both a perimeter frame and a pair of backbone elements. The wheelbarrow wheel axle has been drilled through the longitudinal backbone elements where they stick out of the back.

You can see that if these longitudinals did not exist you would have to weld a frame onto the rear cross member of the perimeter frame on which to mount them.

By the way, if you were to replace the rear cross member with a swinging cradle the cross member of the swinging cradle has to have "V" shape as the bows of the boat are more pointed than the bottom and when the cradle swings through 90 degrees as it gathers up the bows, the sides of the bow of the boat have to contact the wobble rollers before the stem of the boat hits the cross member.

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