swinging mooring

[rich185]

Hi guys, on my shetland 535 i have a bow roller held on with 4 M6 bolts, and one 6 inch cleat just behind the bow roller which has 2 M6 bolts holding that on.

Is the size of the cleat big enough for mooring onto or should i need a bigger one? and should i go with M8 or M10 bolts? Im going to make up some stainless plates to go on the underside.

 

Also is this the best way to tie the boat onto the mooring, or are there safer better ways too on my boat?

 

Thanks

Rich

[Adam F]

I'd think that would be fine. The plate on the underside will be more important than the bolt size, it's about spreading the load.

 

Put it another way: how do you manage when anchored in a big tide? A swinging mooring shouldn't be any worse.

[Mike Fox]

Will your connection to the mooring be rope or chain?

What is the diameter of the rope or chain?

Will this fit your cleat easily?

How will you stop the rope or chain from coming off by itself?

Can you guarantee the rope or chain will not jump off your bow roller?

Will you have a safety rope to a second cleat?

How will you prevent chafe?

Do you plan to use a padlock to prevent theft?

 

Regarding the diameter of bolts, if you go oversize, with a chunky backing pad, then your boat should stay attached in 90 mph storms. Over the last 25 years, I've seen several boats washed up along the shore, and a brief check of their bows have shown a variety of reasons.

 

In my experience, the mooring arrangement needs to stand up to any weather, but fishing you'll rarely anchor in more than a Force 4/5.

 

You might also consider if you need an alternative pontoon berth, if you return to your mooring and it's too windy to get attached. I found that anything above a Force 6 makes picking up the mooring and attaching very difficult.

 

Mike

[Rob]

Crikey Mike, now you have scared him!!!!!!

 

Seriously good advice / good for thought though!

 

All sorts of info on sheer strength of 316 online. Found this but it doesn't advise if 316 or 304 etc: http://www.bssa.org.uk/topics.php?article=127

[Mike Fox]

Rob,

The sheer strength assumes steady load. The snatch loading in a typical storm with 3' waves in Poole Harbour with wind against tide conditions will greatly exceed steady loads.

 

Mike

[Rob]

Im sure Mike, but it gives an idea of the strength of the bolt sizes in a controlled situation, I would expect snatch loading capacity is a minefield to try and measure etc ect.

 

 

Chances are the poorly

Maintained mooring buoy will break away from its anchor. Didn't that happen to a club boat last year?

[Mike Fox]

This is a topic I had a good look at years ago when I spent a year on a swinging mooring.

 

There are a number of failures possible in the mooring arrangement:

- Fitting failure - the cleat is undersized, bolts too small, or backing pad ineffectual and the cleat ripped out completely. This is quite a common failure and is avoidable with chunky components.

- Chafe if using rope, usually on a sharp fairlead or roller cutting the rope in extreme weather. Plastic tubing protecting all sharp edges usually prevents this, but judging by several boats I've found on the beach near Shore Road, this is not always done.

- Bow roller failure usually caused by the lack of a retaining drop-nosed pin resulting in the chain jumping off the roller, resulting in the chain's saw-like action destroying the bow and eventually ripping it off. I've never seen this destroying a bow, but have seen the significant damage this can cause in a short time.

- Structural failure of the bow area caused by a lack of GRP reinforcing on a boat not designed to be kept on a mooring. Catastrophic failure, and shouldn't happen on a well-built boat, but I have seen one boat with a missing deck part in the bow area, with no evidence of "saw" marks.

- Failure in the mooring itself, which should NOT happen if it's renewed annually, with chain through to the buoy, metal rod through, and a chain loop accessible via pickup buoy.

 

The arrangement I used was chain loop to a samson post kept slack, with a heavy nylon (stretchy) snubbing rope protected by plastic tubing about 4-5' long to the chain and a different cleat to reduce snatch loads. Both to an over-sized bow-roller with drop nosed pin to prevent jumping.

 

Belt and braces, but it survived 50 knot+ winds with no damage. 

 

Mike

[Steve S]

Good advice above.

 

I've kept a boats on a swinging mooring for at least 6 years (3 different boats). I got the mooring provider to make a suitable strop for me, the cost wasn't too high, they used some pretty heavy duty rope.

 

Assuming a well made boat and the bow roller is fitted by the manufacture, it should be a suitable size and strength for the weight of the boat.

 

The loop that goes over the cleat on the strop must be secure in some way to stop it coming off. A big shackle is ok or another rope tying it on, I've used both methods, I've use the rope tying it on now. you would think it would never come off but combinations of tide and wind do odd things....

 

The big issue is chafe, a thick plastic cover is a must IMO, the chafing affect in a storm can be extreme, A Harbour master told me chafe is the biggest reason for boats coming off the mooring in storms, taking as little as 20 mins. Chafing against the anchor is a common problem even when under calm condition it appears to be nowhere close the wrong combination of tide and wind can cause the strop to run against it. If your anchor is kept stowed then that is one less problem to worry about.

 

In the bad storms this winter I used 8mm chain as a backup, it wasn't needed happily.

 

Check the strop for damage regularly.

 

Steve

[rich185]

Well thanks for all the reassuring replys guys, feel much better now.

Iv got a couple of stainless plates made up at work for the bow roller and cleat.

Drilled out the bow roller for some new m8 bolts that I fitted today and brought meself a much more beify cleat which takes 4 m8 bolts and put a plate under that too.

 

would it be ok to use chain from the mooring, up to the bow roller then where then is 2 holes on the vertical plates on the bow roller put a padlock through there and also through one of the last links in the chain, then going to rope which I can wrap around the cleat, obviously using plenty of grease on the lock?

By doing that iv got it effectively tied on in two different places and padlocked from little s#*ts

 

cheers

rich.