Slipway Works

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Malabar

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Our local slipway has become unusable because of build up of shingle. It is also too short. We are looking at restoring it so boats (mainly dinghies and RIBs) can be launched from trailers at all states of the tide. Re-inventing the wheel is something to be avoided if at all possible. Have any other slipway construction projects been carried out around the coasts within the last 5 years that might point to a useful source of experience?
 
North Devon Yacht Club did some work on a new slipway a few years ago. But it is just a bit too short to allow full low tide use.

You can see nearly all the slip here
http://www.ndyc.org/

Someone from the club will have the full gen.

Here's an aerial of the club.
 
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Slipway

We built a new one up here (in Loch Gilp)for dinghy sailing, I did some cad drawings for it which we needed for the various approvals (in our case Planning, Sepa and Crown Estate) It was built along side an old pier which gave some shelter but we have already have had to do repairs for some erosion. Crown Estate gave us a small grant, (£2k,) but most of the construction material was provide by local building contractors with voluntary labour. Our original budget was £20k. but we managed to do it for less than £4k.
Our total drop was 4.5m. (tidal range here about 4m.) the slipway was 30m. long plus a 2m. toe finishing on flat rock. The toe was about 1-4 which is about as steep as you can place wet concrete. The remaining gradient was 1-6 below high water mark easing to 1-8 then 1-10 at the top. Usable width originally about 4.5m. was reduced to 3m. to save material and this seem to work as long as trolleys are cleared quickly. For recovering yachts dont go steeper than about 1-8 unless you have a powered static winch. We cast in a strong eye at the top to allow a 1-2 purchase on a wire if we needed it.
First we placed a considerable quantity of (free) heavy rock armour using a tracked digger overlaid and blinded with quarry waste, compacted by the digger tracks. Because we could not afford structural shuttering, the rock on the side away from the pier settled out at about 1-2 but we used big rocks to form a steep edge at the top along the outside. (To reduce risk of damage to boats not approaching straight up). We used mesh reinforcement ( A334?) just sitting over bricks for clearance, (plus a bit of bar here and there) bent down a bit at the outside edge. Big gang with barrows and shovels when the concrete came. Had shuttered top with 6"x 2" sw. Placed ready mix. (we were charged only for cement used) about 200mm thick, rough tamped with a long board to leave ribbed effect for traction. Underwater concrete was used only at the tip which was raked off to the rock bed at about 1-2 for the last metre. Protected temporarily from waves by sandbags filled with shingle from the beach. After the surface concrete set we brought down a mixer and filled in between the rock on the exposed side, more was added here after the first winter.
If you are blending into existing concrete you need to cut away to get at least 100mm. of butt joint or it will just come away. Benign conditions at spring tide on a weekend in March? we were quite lucky.
The steeper gradient near the toe works fine if you are only recovering empty trolleys there at lws.
Though the junior dinghy club sponsored it, because of the support from all the locals we called it 'the community slipway' and it is used by everyone including jetskis as well as tenders from visiting yachts.
If any of this is relevant and you require more info. pm. me
 
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Quandary seems to have attacked it in a workmanlike manner.
My advice (and I say this as someone who works somewhere that has many large projects carried out by volunteers, many without the skill-levels needed) is to get the project designed by someone who does know what they are doing and managed by someone with the same level of experience.
Volunteers are there to provide grunt. Not to make decisions.
 
Very many thanks Quandary for a most helpful response. All most encouraging. Thanks also Sarabande & Lakesailor. Anybody else out there who has negotiated the slippery slope?
 
Slipway

I had a slipway built at Christchurch. It is on a river but tidal. After excavations gabions were dropped in and filled then, at the lowest available tide, concrete poured. All went well, if you need the name of the company I can find it.
 
Malabar said:
Our local slipway has become unusable because of build up of shingle. It is also too short. We are looking at restoring it so boats (mainly dinghies and RIBs) can be launched from trailers at all states of the tide. Re-inventing the wheel is something to be avoided if at all possible. Have any other slipway construction projects been carried out around the coasts within the last 5 years that might point to a useful source of experience?
Click to expand...

Malabar - How did you get on? My local club is at a point of crisis due to similar issues and would be good to hear your experience. Whilst the exisisting slipway we have is great at high tide it is on a stretch of river where the popular lunch time would be low tide. Most would look to catch the up stream flood thereby avoiding harbour dues that would become due if heading the other way and an arguably more senic trip and returning on or around the ebb.

Part of our problems - the exsisting slipway is only accessed by foot (no cars) and has no winch. Whilst the gradient is ok the foot leads to a 'rocky outcrop' and suffers from mud / silt buildup. It terminates driectly into branching off of a drainage ditch from the main river (so a direct building out of the slipway and more regular mainenance is probably not the whole answer as this would obstruct the drainage at low water?).

Any and all thoughts welcome!
 
Malabar said:
Very many thanks Quandary for a most helpful response. All most encouraging. Thanks also Sarabande & Lakesailor. Anybody else out there who has negotiated the slippery slope?
Click to expand...

Our local shipwright based at Odessa Marine, Bob Forsyth and his team, built a new wooden slipway in Cowes last year. Come round to Odessa in Little London, Newport and talk to Bob.
 
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