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Canal boat Hull form coefficients


Rik_Boat

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Hi all, 

I am trying to have an general understanding of typical value of Hull coefficient form of wide beam and narrow canal boat to check with mine. 

I am mainly  interested in block coefficient value (cb) and Prismatic coefficient (cp). 

 

At first approch canal boat must have similar hull shape hence a specif acceptable range of this value that basically are dimensionless numbers that describe hull fineness and overall shape characteristics.

Any comments is very welcome. Thanks

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I very much doubt that any narrow boat or wide beam canal craft builder has ever bothered to calculate any of the hull coefficients applicable to their products.

Indeed I doubt if many inland craft builders would even know what the coefficients are or mean.

 

If you want to calculate typical ones, treat a modern  canal boat as a rectangular mid section 2m wide  with  a vertical sided point about 2 m long at either end.  This value will be 

a little larger than dead accurate, but close enough for Government work.

For rough work 1.00 is close enough for both?.

N

 

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Agreed. Complicated to accurately calculate and considering the speeds they operate I seriously doubt most builders care. I suspect the effort is put into the interior and making the most of the space. Of course is the builder happens to design there boat in something like Rino they could let the software calculate it but again, not sure it really matters in practical terms.

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40 minutes ago, Rik_Boat said:

Hi all, 

I am trying to have an general understanding of typical value of Hull coefficient form of wide beam and narrow canal boat to check with mine. 

I am mainly  interested in block coefficient value (cb) and Prismatic coefficient (cp). 

 

At first approch canal boat must have similar hull shape hence a specif acceptable range of this value that basically are dimensionless numbers that describe hull fineness and overall shape characteristics.

Any comments is very welcome. Thanks

Y ??

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1 hour ago, Rik_Boat said:

Hi all, 

I am trying to have an general understanding of typical value of Hull coefficient form of wide beam and narrow canal boat to check with mine. 

I am mainly  interested in block coefficient value (cb) and Prismatic coefficient (cp). 

 

At first approch canal boat must have similar hull shape hence a specif acceptable range of this value that basically are dimensionless numbers that describe hull fineness and overall shape characteristics.

Any comments is very welcome. Thanks

Others have hinted that this information would not be readily available, and it is difficult to see why you would need it. However, you could calculate it from first principles. A good source of information would be "Ship Stability for Masters & Mates" by D.R. Derrett printed by Stanford Maritime Ltd.

 

Enjoy.

 

Howard

Edited by howardang
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Dunno. This sounds like something that involves algebra. Never the less some boats go better than others despite looking as near as dammit identical and quite a lot of old wooden boats were reckoned to be quick and handled well despite being hogged, spread, covered in bits of old flattened tins to keep the water out and having a bottom full of nailheads and bits of rope hammered into the seams.

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Hi all thanks for the feedback. 

 

Patron despite to all other type of huge vessels, ther is not available data that could allow me to  make a judgement/comparison with my data. 

I know how to evaluate them, but I was wondering if some of you has an idea of typical value for canal boat hull from coefficient. 

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7 minutes ago, Rik_Boat said:

Hi all thanks for the feedback. 

 

Patron despite to all other type of huge vessels, ther is not available data that could allow me to  make a judgement/comparison with my data. 

I know how to evaluate them, but I was wondering if some of you has an idea of typical value for canal boat hull from coefficient. 

I sometimes use a block coefficient of around 0.9 to 0.92 but only as a rough guide. As you will know, A canal boat is nearly always a box-shaped vessel (although there are a few V shapes around) so the prismatic co-efficient for the majority is as near as makes no difference 1.

 

Howard

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Patron,

Many thanks,

 

This values are very reasonable and near to mine. I am (cb 0.9 and cp 0.87). Basically I am creating a hull and I am not able to find information to use for double checking purpose. It comes out that despite other vessels for canal boast this information are not commonly shared as I think they are intellectual properties of the boat builders. But this very strange as the canal boat's hulls are typically standard, a part from peculiar shape characteristics  at bow and stern. s

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6 hours ago, Rik_Boat said:

... this information are not commonly shared as I think they are intellectual properties of the boat builders

I suspect it’s far more likely that the boat builder neither knows nor cares. Why would he?

 

 

Edited by WotEver
Typo
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2 hours ago, Rik_Boat said:

Hi all, 

I am trying to have an general understanding of typical value of Hull coefficient form of wide beam and narrow canal boat to check with mine. 

I am mainly  interested in block coefficient value (cb) and Prismatic coefficient (cp). 

 

At first approch canal boat must have similar hull shape hence a specif acceptable range of this value that basically are dimensionless numbers that describe hull fineness and overall shape characteristics.

Any comments is very welcome. Thanks

 

Don't forget that we are not discussing "boats" here.

These are 'squared off steel tubes of varying length' with very little in the way of aquadynamics and closely related to 'waste skips'.

 

Image result for skip boat

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2 hours ago, BEngo said:

If you want to calculate typical ones, treat a modern  canal boat as a rectangular mid section 2m wide  with  a vertical sided point about 2 m long at either end. 

 

A typical modern narrow boat is built to an overall width (over the guards) of 6ft 10 ins (yes, the industry still largely uses imperial units). If it is built 'Brummagem square', then the hull sides will be vertical. But most mid and lower market boats are build with the hull sides tapering in to a 2m wide baseplate. Nothing to do with hydrodynamic design, and everything to do with making hull fabrication easier and cheaper.

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2 minutes ago, Rik_Boat said:

Thanks Patro, actually this is a really good point.

 

Do you know what is the typical value of the angle between hull side and base plate, (basically the inclination of the hull sides when they are not vertically. 

About 1 in 10 

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12 minutes ago, Rik_Boat said:

What does it means "about 1 in 10" in terms of angles

It's not very far off vertical, or 90 degrees between baseplate and hull sides. Not enough of a difference to make any discernable improvement in boat handling characteristics anyway. The thing to remember is that narrow or wide, the hydrodynamics of canal boats are fairly similar to the commercial narrowboats or barges on which the designs are based. In other words they all handle like crap compared to just about any other type of boat.

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Theory & practice don't often seem to match in this context. Remember the ABC boats with a bow that resembled a dustbin? Theory (and tank tests) showed that the design was more efficient than the conventional bow shape, and would enable a boat to travel faster with less wash, causing less disturbance to the banks and the canal bed. In practice they were slower and created more wash; we once followed one down the Llangollen, he pulled over and waved us past saying that he kept having to let other boats by.

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