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Mfuller
121 Posts |
 Posted - 24 Jan 2017 : 11:39:30
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Hi Guys,
I'm currently working with a group of people, including the Environment Agency, the IWA and local councils in re-instating a slipway for access to the River Parrett in Langport.
We have had a survey done of it's condition and one of the things raised was that it is a 1:8 gradient slipway, as apposed to the recommended inland waterway guidance of 1:4.
So, my question. If you were going to take your boat to visit an area, would the gradient of the slipway influence your decision? A 1:8 slipway is not as steep as a 1:4 so this means the trailer and vehicle may need to go further in to float the boat. Would this be an issue? Have you ever considered this when using a slipway?
Your thoughts would be appreciated :) |
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cliveshep
Thailand
1324 Posts |
Posted - 24 Jan 2017 : 16:42:35
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1 in 8 might suit a truck, tractor or 4 x 4 but by the time a car got a boat and trailer far enough into the water to float it off the car would be waterlogged and would need to be recovered. Draw it out on a graph, you need at least 750mm of water at the axle position to float a small cruiser off a trailer, that would put the car in maybe 500mm of water or more at 1:8. 1:4 is a good slope putting the trailer in deep water but allowing the car to just get it's feet wet!
How hard is it to over-lay the 1:8 to reduce the gradient? A fairly rough concrete would give good traction - the worst slips I ever used were too smooth reducing valuable traction in recovering a heavy boat. Putting a sheet pile coffer dam around a slip, pumping out and over-laying is not rocket science nor extreme civils construction but basic groundworks. Concrete tamped to leave it rough is easy peasy, mark the lines and simply back a Readymix truck down the slip and pour it out, raking and tamping to line. Shouldn't cost the earth really, biggest expense hiring the sheet-piling, and a machine to install it, a Sykes Univac 6" pump to evacuate the water and a return visit late to recover the sheet piling.
I'd have expected my groundworks gang - 2 men with a 13-tonner - to do the whole operation in under a 5-day week.
Finally living the dream!
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IanM
United Kingdom
2238 Posts |
Posted - 24 Jan 2017 : 17:54:37
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If the slipway is directly off a public highway then be sure to check the highways rules/regs too. A few years ago I was involved as a volunteer building a new slipway for the Stroudwater Canal and we had to make three progressively steeper gradients. The gradient closest to the road was not permitted to be exceed a certain "steepness" but the bit at the water end had to be steep enough to allow normal tow vehicles to launch and recover as Clive describes. And, yes, make the last bit as rough as you can.
Work in progress:
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stratford4528
United Kingdom
414 Posts |
Posted - 25 Jan 2017 : 07:59:49
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| I would have thought a curved slipway would be best. the further you go into the water the steeper it gets. I have trouble with my 32 on a shallow slip. The water is close to the top of my wellies when I am winching the boat back on. With my portable slip I made for my lake it is quite steep the bow is over the front axle before I have to start winching. |
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Mfuller
121 Posts |
Posted - 26 Jan 2017 : 09:59:53
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Thank you all for your input!
I shall pass on to our team. Very much appreciated. |
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Topic |
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Slipways - Your opinions please.
