Bolt on center line ring/eye?

[OldPeculier]

I currently have a couple of center lines tied to the hand rails. I don't really like this and would prefer to have a ring in the middle of the roof. Any ideas on how to go about this? The ceiling is T&G so although I don't mind cutting a small hole in it, access from below is going to be limited. Similarly, I dont really want anything welded on, as the roof space is full of polystyrene.

 

Would an eye bolt with a big washer behind the nut be strong enough? Or should I be thinking of an eye welded to a plate that is then bolted onto the roof? I think the roof is 3mm

 

Or maybe something else?

[KJT]

Personally I would use a 'T' stud. It's much easier to tie off the centre line than using a half loop or eye bolt. You can get threaded 'T' studs so the hole would need to be tapped I guess, to accept it. Then it just screws on.

I had one put in place of a metal half loop and it is much more convenient. It was done entirely from outside. It was not necessary to gain access from the inside which would have been very difficult on my boat.

 

Ken

[Alan de Enfield]

It depends what you intend to use the ring for.

 

A centre rope should not be used for 'stopping' the boat, or mooring the boat (but unfortunately a lot of people do)

Therefore there should not be any great load on it when it is used correctly, as a 'hand-held' line.

 

A simple ring bolt thru' the roof should do, but don't in the future use the ring as a mooring point, or use it to tie up in a lock as you may rip a 'gurt big' ole in the roof'

[Chewbacka]

If you want a bit of strength and don't want to weld the roof, I would weld a hoop or ring into some 6mm plate then bolt the plate to the roof using a four 10mm bolts.

If your roof steel is a bit thin for tapping, then you can use stainless rivet nuts. I used these for holding my solar panels on the roof.

If you smear them in epoxy and then bang them in and set them they don't leak - mine haven't after 2 years.

 

Something like these -

http://www.ebay.co.uk/itm/STEEL-ALUMINIUM-STAINLESS-RIVNUTS-NUTSERTS-RIVET-NUTS-M3-M4-M5-M6-M8-M10-M12-/361388153801?var=630737719139&hash=item5424699bc9:m:mmbqNhMqoBEOifh0cxwNRCg

[magnetman]

A forum member (Chris JW don't know what happened to him but anyway) once stopped his Nb using a centre line attached to a to a poorly fitted eye in the roof and it ripped off catapulting the metal bit towards him and hitting him in the shoulder.

 

Worth putting in proper reinforcement as this sort of thing can happen and if it was the head not the shoulder it could be very serious

[Alan de Enfield]

A forum member (Chris JW don't know what happened to him but anyway) once stopped his Nb using a centre line attached to a to a poorly fitted eye in the roof and it ripped off catapulting the metal bit towards him and hitting him in the shoulder.

 

Worth putting in proper reinforcement as this sort of thing can happen and if it was the head not the shoulder it could be very serious

 

But - why would anyone do that ?

[magnetman]

The reasons are a) obvious or b ) irrelevant

 

Fact is people do sometimes stop heavy steel canal boats with centre lines.

 

I have done it sometimes when it makes sense but my centre lines are attached to welded handrails and I do it in a controlled manner not too suddenly. I also have undersized ropes as centre lines so the rope will break before damage to the boats hardware

[magnetman]

 

The best centre line moment was when I was approaching Iffley Lock on the Thames in my barge (58ft x 12ft) from upstream and was being blown off the layby by a stiff breeze. I don't use a bowthruster. There was a trip boat about to exit the lock. I motored the stern in to the layby then got off and wrapped one of my centre lines around a bollard. Result was that the boat lined itself up with the layby nicely and prevented any embarrassment for me or the other boat full of passengers

 

My centre lines are braided rope with a decent amount of stretch so they can do unusual tasks when needed.

[dmr]

Accidents happen and sooner or later you will be stopping the boat which moving rather faster than you intended with the centre line. If the boat don't stop then hopefully the rope will snap rather than the eye pulling out or the roof deforming. Whatever you do it needs to be strong.

 

..............Dave

[FadeToScarlet]

 

But - why would anyone do that ?

To hold the boat into the side when descending a wide lock, and the person you're sharing with isn't capable or keen enough to come in 10' behind you and be alongside when reverse is put on.

 

It's strapping rather than winding- put a loop of the rope around the strapping post so the bitter end is underneath, then pull it upwards so the rope rubs on itself and around the bollard. You can then increase the pull on it to increase the friction and bring the boat to a stop.

 

A strapping line from the anser pin would be better, but I've not got any anser pins.

[Claude]

It depends what you intend to use the ring for.

 

A centre rope should not be used for 'stopping' the boat, or mooring the boat (but unfortunately a lot of people do)

Therefore there should not be any great load on it when it is used correctly, as a 'hand-held' line.

 

A simple ring bolt thru' the roof should do, but don't in the future use the ring as a mooring point, or use it to tie up in a lock as you may rip a 'gurt big' ole in the roof'

My boat is 33 tonnes so I stop it on the engine, but i often finally stop it using the centre rope. My roof is 5mm thick so no problem there. I also moor using the centre rope and as long as it's left lose it's never been a problem. The mantra that you shouldn't moor with a centre rope I'd a myth. It depends how you do it.

I currently have a couple of center lines tied to the hand rails. I don't really like this and would prefer to have a ring in the middle of the roof. Any ideas on how to go about this? The ceiling is T&G so although I don't mind cutting a small hole in it, access from below is going to be limited. Similarly, I dont really want anything welded on, as the roof space is full of polystyrene.

 

Would an eye bolt with a big washer behind the nut be strong enough? Or should I be thinking of an eye welded to a plate that is then bolted onto the roof? I think the roof is 3mm

 

Or maybe something else?

My M24 stainless eyebolts are bolted from underneath and welded from the top to prevent them from spinning (and leaking)

Personally I would use a 'T' stud. It's much easier to tie off the centre line than using a half loop or eye bolt. You can get threaded 'T' studs so the hole would need to be tapped I guess, to accept it. Then it just screws on.

 

And spins off?

 

I've never had a problem putting a rope through an eye bolt.

[PaulG]

I used a fitting similar to this one. Drill and tap four holes to match, and you don't need access from below. Bit of sealant on the screw threads to prevent leaks and you're good to go.

Edited June 1, 2016 by PaulG

[OldPeculier]

Ok, some good ideas. Thank you. I would like to have something as strong as possible just for those odd occasions when it all goes wrong and you need to really use that center line. I hadn't thought of using rivet nuts. That might be the way to go. Do I need a special tool, or can you set them with a long bolt and a nut?

[DHutch]

If you do not want to weld, and there are various reasons not to, then the two basic option you have are to through bolt or to have some sort of blind fixing.

- Through bolt is in a way simpler, and slightly easier, but needs access to the roof from the inside.

- Blind fixing can be either drill and tap, or as said, use a insert like a rivet nut (think pop-rivet that will then accept a bolt.

 

You can then secure either a bespoke made part, or a of the shelf fabrication. Obviously the shorter in height and or wider the bolts if using multiple the better, as you are then closer to being in shear then tension/bending. The main issue with rivet nuts is getting them in there, as the tool costs a lot and other options can give mixed results.

 

The final rule is that whatever fixing you have it should always be stronger than the rope, so if its not very heavy duty fixing then use a lighter gauge rope, so it will fail first rather than turning the fixing in to a potentially lethal weapon. Of the shelf fixings such as eye bolts should have load ratings (SWL etc) stated, typically in both vertical and horizontal directions, and the pull-out and shear forces of a bolt can also be calculated. Rope also states its breaking strain in perfect conditions, and if splicing the end and attaching with a shackle you should use 90% of this figure, if using a knot you could go as far as 75% I understand. The breaking strain should always be less than the swl of the fixing.

 

We have access to through bolt and use a single M10 eye bolt, which is borderline for the rope we use, so I also have a short length from eye to the handrail (robust welded affair) to retain the eye should it fail.

Personally I do not agree that the centerline 'should never be used to stop the boat' so our rope/fixing are sized to bring a 22ton narrowboat to rest safely, and as James said, we often use it to hold the boat in either a wide lock or to hold the boat when ascending a lock I know pulls strongly in one direction and then the other as we are 'short' for a narrow lock at only 58ft.

 

I also often use the centre line while mooring, tied at an acute angle as a spring back to the front or rear of the boat, although as said it should never be tied down to the floor at right angles to the boat.

 

While doing this work on the centerline, it is also worth considering the specification and condition of the fixing at the front and rear of the boat, and the rope you are using with these, as with the use of ropes which are of a diameter which is 'nice to hold' some boats are very suspect here. One option if you are using a polyester rope as many do is to switch to polypropylene which is a lower density rope with lower breaking strain per section, you also have the added benefit that it floats if slightly less nice to throw.

 

Anyone thinking that this post is a little sombre and if Chris J W's indecent mentioned above was not enough, its worth reading the MAIB report on the fatal incident on the Thames involving the Star Cutter, even if you just skim through the photos.

https://www.gov.uk/maib-reports/failure-of-mooring-bollard-on-passenger-vessel-star-clipper-at-st-katharine-s-pier-river-thames-england-with-loss-of-1-life

 

 

Daniel

[Chewbacka]

Setting a rivet nut - if you buy a cheap tool it can do aluminium and maybe m6 in steel.

I used steel (from memory not stainless) and a high tensile bolt with a nut and oil on the thread of the bolt. You almost need 3 hands to do this.

 

1 Drill a snug fit hole

2 Tap the rivet nut into the hole which should be a snug fit - ideally it should need a tap from a hammer to sit flat - to encourage it not to rotate.

3 Put a nut onto a high tensile bolt with some oil on the threads of the nut.

4 Add a washer, or better still a long plate with a hole

5 Screw into the rivet nut

6 Now you need a spanner on top of the bolt to stop it rotating and another spanner turn the nut to pull on the rivet nut. If the rivet nut starts to rotate then hold the long plate with your 3rd hand. If the rivet nut is a good tight fit it will not rotate and a washer is enough between the rivet nut and the bolt nut.

 

I did this with M8 rivet nuts.

[OldPeculier]

Setting a rivet nut - if you buy a cheap tool it can do aluminium and maybe m6 in steel.

I used steel (from memory not stainless) and a high tensile bolt with a nut and oil on the thread of the bolt. You almost need 3 hands to do this.

 

1 Drill a snug fit hole

2 Tap the rivet nut into the hole which should be a snug fit - ideally it should need a tap from a hammer to sit flat - to encourage it not to rotate.

3 Put a nut onto a high tensile bolt with some oil on the threads of the nut.

4 Add a washer, or better still a long plate with a hole

5 Screw into the rivet nut

6 Now you need a spanner on top of the bolt to stop it rotating and another spanner turn the nut to pull on the rivet nut. If the rivet nut starts to rotate then hold the long plate with your 3rd hand. If the rivet nut is a good tight fit it will not rotate and a washer is enough between the rivet nut and the bolt nut.

 

I did this with M8 rivet nuts.

 

Thanks, I seem to remember this being done where I worked many years ago but wasn't sure.

[boat fan]

There is another way to do this , but it depends if you are happy with the way it looks.

 

You can bolt the fitting with high tensile bolts that have been fitted with compression tubes.

 

These are a steel pipe / tube that fits snug ( not tight ) over the bolt .The holes are drilled through the roof / insulation and lining ( T&G )

The tube has a correctly sized washer and nut fitted over the tube and T&G lining from below .

 

The tube prevents the nut from crushing the T&G lining and insulation.

Edited June 5, 2016 by boat fan

[alan_fincher]

I used a fitting similar to this one. Drill and tap four holes to match, and you don't need access from below. Bit of sealant on the screw threads to prevent leaks and you're good to go.

 

I'd have reservations iuf the steel you are tapping into really is only 3mm thick, as the OP suggests. THat is not a lot of thread on each bolt!

[PaulG]

 

I'd have reservations iuf the steel you are tapping into really is only 3mm thick, as the OP suggests. THat is not a lot of thread on each bolt!

Take your point, but 4mm is more usual, and this metheod of fixing has worked fine on my 55 footer for the best part of ten years. From memory I used 8mm screws.

 

For a "belt and braces" approach, there is also the option to remove some paint and then use some metal-loaded epoxy to bond the base of the fitting to the roof in addition to the screws.