Any civil engineers out there?

[Humblebee]

I am in Uganda at the moment helping a new search and rescue charity on the great lakes. We have a boat shed made from old containers and have been given an 8m RIB by an oil company. At the moment I am trying to build a slipway from the boat shed to the water. We need to cross about 20metres of sand and shingle. The boat sits on a road trailer. Cement and angle iron are fairly cheap here. I think two tracks to take the trailer wheels would work, but I have no idea how to go about building it. Can anyone help please? Any advice or suggestions would be appreciated.
Chris Anstock
"Humblebee"

 

[Stellina]

Which oil company donated the rib?

 

[DJE]

Cheap and nasty method, just dig some cement in to the sand and shingle grade it smooth and compact it with a roller. Do you need to extend the slipway below water level? That's going to be the difficult bit; does the water level vary much so that you can do the bottom bits at "low water"? Can you get hold of an excavator (or a lot of manpower) to form an earth dam around the slipway site and then pump out the water so that you can work in the dry? If it's got to be done in the wet you could weld up some kind of steel grillage and drop it in to place on the lake bed.

 

[holly1]

Good advice from DJE i think but for a pukker job dig the trackways out , then mix one portion of cement with six portions of sand and stones and enough water to make it wet but not runny.

Do it in sections no more than two meters long and about six inches deep

If it is really hot do the work in the late afternoon or the concrete will crack

If there are not many stones in the sand it will not be very strong

Good luck

 

[Stellina]

Can't you cut up a container and weld it back together into a slipway? Trailer wheels might fit into the corrugations....

 

[111KAB]

Main thing to establish is the situation below ground. Little point in putting a 'sound' system above ground if the substructure cannot support it. Without knowing the weight above ground difficult to calculate but I would dig some holes to see if there is any water ingress. If there is you will need to dig some bases and work out some kind of waterproof shuttering so that water doesn't 'run into' your foundations. A decent sized pad of concrete say at two metre centres should support your rails. Try not to go for overkill but given the effort you are making it is wortwhile doing something which will last. I'm abroad myself at the moment but back in the UK next week. PM me if you have any dimensions etc and I am more than willing to put pen to paper if that helps.

 

[William_H]

I presume you have tried to back the trailer and RIB into the water using a 4X4. This can be easier if you have an extension bar on the draw bar of the trailer so gets the towing vehicle out of the water.
An other alternative is a fixed winch to haul the trailer out using a jockey wheel at the front. You can put a large mooring in deep with a pulley so that winch can pull the trailer into the water.

If the sand is just too soft for the trailer you will have to build a ramp.
Or you might try larger tires, dual wheels or similar to limit the sinking into the sand.

Our yacht club were given sections of the prefabricated concrete roof from a toilet block which are terrific ramps but a large crane was needed to drop them in place.

There are all sorts of ideas to enable the RIB to be launched.

good luck olewill