Why do so many people tie up their boats like this?

[jonk]

Theory is fine, but that is all it is. If I moored our boat with lines at 45 degrees or more, it will move backwards and forwards everytime a boat passes.

 

Or boat is 33" deep at the back and 18" deep at the fromt, and has 15ft swims. I have found, through trial and eror, that a forward line at a little less than 45 degrees and a rear line at just over 90 degrees, both moored tightly, fendered with two small tyres suspended from the cabin side steps, prevents any backwards and forwards movement and without any rolling.

 

I am not suggesting that anyone else should copy me, but that configuratuion works for us, and I am bemused by people suggesting that they know better.

 

OK - a modified outwards works for you! I did say practice does not always follow theory

I think your 'tightly' has a lot to do with it as well?

 

John

 

There is more to mooring a boat than just stopping it moving forward and backward. If ropes are tight enough to prevent movement ( at whatever angle ) what happens about water level dropping ? More important on a river I know but even canals can drop overnight.

 

True - I experienced that in Skipton a few years back!

 

John

 

the geometry describes the relationship between fore/aft travel vs change in rope length when the angle is not 180deg. It doesn't explicitly include or exclude stretch as being the source of the change in length.

 

OK then a long rope will stretch more than a short one so a 90 mooring rope will stretch less than a 45 AND since the 90 has no longitudinal resistance it cannot restrict movement except by pulling the boat into the bank and hence the boat has nowhere to move except for the little stretch that the short rope gives. The 45 does have longitudinal resistance but will not pull the boat into the bank so strongly so there is more leeway for the boat to move with the increased stretch. There is probably a lot wrong with this argument but then theory and practice are poor bedfellows! Interesting discussion though.

 

John

[nicknorman]

The fact that the ropes are at right angles will not cause the boat to roll. It is the vertical position of the attachment point that is critical here. If you use a centre line attached to the roof that will cause the boat to roll.

 

Nick

Well I sort of agree a bit, but the force developed in a rope that is near right angles is very much greater than one at say 45 degrees for a given amount of boat fore/aft suction. So if there is any roll couple due to the relative heights of the bank attachment vs the boat attachment, it will be exacerbated big time. The worst cases seem to be a boat with a high T stud in the bow, rope going 90 deg laterally but at maybe 45deg slope down to low piling. The suction generates a lot of rope tension which makes a big couple between the bank and the T stud. If the rope were much longer and at a better angle, the rope tension arising from the boat suction would be much less, so there would be an insignificant roll couple (and less strain on the rope so it would last longer). The further away from 90 deg laterally, the less the diminishing rope pull makes a couple on the roll axis of the boat.

Edited August 6, 2011 by nicknorman

[BlueStringPudding]

I wonder how many people contributing to this thread pep along, always in a hurry and get irritated by rows of moored boats, so don't bother slowing down...?

[boatyboy]

Well I sort of agree a bit, but the force developed in a rope that is near right angles is very much greater than one at say 45 degrees for a given amount of boat fore/aft suction. So if there is any roll couple due to the relative heights of the bank attachment vs the boat attachment, it will be exacerbated big time. The worst cases seem to be a boat with a high T stud in the bow, rope going 90 deg laterally but at maybe 45deg slope down to low piling. The suction generates a lot of rope tension which makes a big couple between the bank and the T stud. If the rope were much longer and at a better angle, the rope tension arising from the boat suction would be much less, so there would be an insignificant roll couple (and less strain on the rope so it would last longer). The further away from 90 deg laterally, the less the diminishing rope pull makes a couple on the roll axis of the boat.

[blackrose]

To be honest, I get a bit fed up with these "the way I do it is best" threads, and tying up is one where you cannot make hard and fast rules, because it also depends on the underwater shape of your hull, and how well you fender your boat to absorb movement.

 

If you have one of these modern shallow draught, slab sided boats with virtually no swim, then you need all the help you can get to stop it rocking about when a boat passes, but if you have a boat with a deep draught and long swims, and you use decent sized fenders, the requirements are no where near as critical.

 

Frankly there is no correct way for all boats, and the experienced boater will soon work out what works for their boat. The best system for our boat does not comply with any of the examples given above.

 

I agree. I only read up to your post on this thread, but on this and other issues many posters seem to assume we're all moored on canals. If I moored up in the ways some people have told us is the best way, my boat would probably be stuck halfway over Bell Weir by now.

[bizzard]

I wonder how many people contributing to this thread pep along, always in a hurry and get irritated by rows of moored boats, so don't bother slowing down...?

I agree,it all sounds very suspicious. 'Remorse' bizzard

[steelaway]

Have you considered the geometry? Assuming the ropes are at 90 deg and tight, how much does it have to stretch to allow say 1" fore aft movement. Maybe 1mm? Rope twice as long, but at sensible angle, same force = 2mm stretch which equates to perhaps 3 mm fore aft movement. Maybe they don't teach geometry at school these days?

 

 

I have considered geometry - and sarcasm!! And I'll say it once again - I dont have a problem!

I have even stopped bothering about boats going past to fast - life's to short

 

Alex

[Lord Elsan]

Since we're covering all the angles on this subject, here's something more to consider...

 

If you have the ropes pointing inwards, then they restrain the forward-backward motion of the boat in a way that tends to counter-lever the other end of the boat away from the bankside and increases its bumping-around.

 

Conversely, having the ropes pointing outwards ensures that the boat's forward-backward motion is checked in a way that also pulls the boat in towards the bankside and thus holds it more steadily.

Edited August 7, 2011 by Lord Elsan

[nicknorman]

Since we're covering all the angles on this subject, here's something more to consider...

 

If you have the ropes pointing inwards, then they restrain the forward-backward motion of the boat in a way that tends to counter-lever the other end of the boat away from the bankside and increases its bumping-around.

 

Conversely, having the ropes pointing outwards ensures that the boat's forward-backward motion is checked in a way that also pulls the boat in towards the bankside and thus holds it more steadily.

I preferred my J-Lo metaphor! (post #17)

Edited August 7, 2011 by nicknorman

[Lord Elsan]

I preferred my J-Lo metaphor! (post #17)

Doh! Me too.

(Hands over the "My way's better" cap)

Edited August 7, 2011 by Lord Elsan

[sebrof]

To be honest, I get a bit fed up with these "the way I do it is best" threads, and tying up is one where you cannot make hard and fast rules, because it also depends on the underwater shape of your hull, and how well you fender your boat to absorb movement.

 

If you have one of these modern shallow draught, slab sided boats with virtually no swim, then you need all the help you can get to stop it rocking about when a boat passes, but if you have a boat with a deep draught and long swims, and you use decent sized fenders, the requirements are no where near as critical.

 

Frankly there is no correct way for all boats, and the experienced boater will soon work out what works for their boat. The best system for our boat does not comply with any of the examples given above.

 

 

Actually, the hull shape makes very little difference.

 

The ideal way is to use four lines, two at right angles from bow and stern, and two springs. This provides the most control over the boat, but few people can be bothered to do it.

 

Lines at 45 degrees, going outwards, provide far more control than 45 degree lines going inwards. Look at a digram and you will see why. The outward lines will prevent pivoting far more effectively than lines going inwards.

[jonk]

Actually, the hull shape makes very little difference.

 

The ideal way is to use four lines, two at right angles from bow and stern, and two springs. This provides the most control over the boat, but few people can be bothered to do it.

 

Lines at 45 degrees, going outwards, provide far more control than 45 degree lines going inwards. Look at a digram and you will see why. The outward lines will prevent pivoting far more effectively than lines going inwards.

 

I agree in principle.

The two at right angles stop the boat from moving far from the bank (or in fact anywhere!) and the 45 degree lines help with taking pressure of the pins while also aiding fore and aft movement restriction.

Just having the right angled ropes would put a lot of pressure on the pins. However most of the theoretic solutions don't take into account that the ropes are generally not horizontal from boat to bank - which adds to the fun. Right angle ropes could cause more rolling in these cases for obvious reasons. There is also a problem with rise and fall of water levels - the right angle ropes would give little leeway for vertical movement if they are horizontal from boat to shore.

My conclusion is that 45 degree ropes both forwards and backwards (springs) would be the best compromise, in general, since this would allow for more 'up and down' movement as well as doing a good job of preventing fore and aft movement and pivoting.

All good in theory but as has been said - everyone has their own ideas and what works for YOU is the best solution for YOU

 

John