Jump to content

Canal boat Hull form coefficients


Rik_Boat

Featured Posts

There word "block" could be replaced with "brick" and "coefficient" replaced with "comparison" for most canal boats. 

 

0.9 seems a reasonable figure. 

 

It would be theoretically quite interesting to calculate the Cb of an old properly made narrow boat like a Josher with the double curved swims but the length of the swims would not make that much difference to the overall figure given the length of the straight bits assuming it was a full length narrow boat. 

 

 

For a very short boat the swims would make quite a big difference to the Cb.

Edited by magnetman
  • Love 1
Link to comment
Share on other sites

I would still ask .....   Y  ?

 

There are several factors affecting the way a narrowboat 'swims' including for example the shape of the bow and the plan view of the taper of the lower hull forward of the propeller.  The block coefficient is the least of your worries.  If the bow and stern are well shaped to reduce wave-making then the block coefficient will be whatever it turns out to be, but you wouldn't base your design on an 'ideal' block coefficient value.

 

Having said all that, on a typical canal in the UK the wave-making is more the result of displacing water in a narrow channel than the fine tuning of the hull shape.  The boat never approaches the 'hull speed' which is way more than the speed limits on UK inland waterways.

 

On the other hand, if you want to design a narrowboat with an efficient (and potentially faster) hull form for use on  wide deep rivers then you would do better to copy an 'inspection launch' hull form, which is primarily designed to swim smoothly and at higher speeds than a traditional narrowboat that was designed only to carry freight.  An inspection launch was intended to carry senior management in comfort and has much finer bow and stern shapes and will have a much lower block coefficient. 

Edited by Murflynn
Link to comment
Share on other sites

5 hours ago, Rik_Boat said:

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

You are having a laugh?

I doubt there are any narrowboat hulls  that have been designed by a Naval Architect. 

 

Why would you be concerned about drag when the typical narrowboat does not exceed 5 knots

 

3 hours ago, Rik_Boat said:

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

Trigonometry ?

 

  • Greenie 1
Link to comment
Share on other sites

54 minutes ago, Dr Bob said:

Depends on the depth. Maybe the toe-in control needs to connected to a depth gauge?

of course you could fit hydrofoils, then you could use them to vary the angle of toe-in dangle as well as reducing the water disturbance ........   just remember to check the headroom at low bridges.

Link to comment
Share on other sites

4 hours ago, Murflynn said:

of course you could fit hydrofoils, then you could use them to vary the angle of toe-in dangle as well as reducing the water disturbance ........   just remember to check the headroom at low bridges.

Maybe I could have tanks to flood like a submarine so when headroom gets limited, I could trim down by an inch or two.

Link to comment
Share on other sites

19 hours ago, MartynG said:

You are having a laugh?

I doubt there are any narrowboat hulls  that have been designed by a Naval Architect. 

 

Why would you be concerned about drag when the typical narrowboat does not exceed 5 knots

 

Trigonometry ?

 

I do not think is it funny at all. For a canal boat you need to comply with standard requirement and produce mandatory document that are still made by Naval Architect. Then there is no doubt about the minor complexity of the hull in comparison to other type of vessel. 

I am not concerned about the drag. 

Then thanks for the second answer very useful, but if you pay attention to the previous comment you can notice that we  already answer to that question 

Link to comment
Share on other sites

3 minutes ago, Rik_Boat said:

I do not think is it funny at all. For a canal boat you need to comply with standard requirement and produce mandatory document that are still made by Naval Architect.  

 

Do you ?

Edited by ditchcrawler
Link to comment
Share on other sites

8 minutes ago, Rik_Boat said:

I do not think is it funny at all. For a canal boat you need to comply with standard requirement and produce mandatory document that are still made by Naval Architect. Then there is no doubt about the minor complexity of the hull in comparison to other type of vessel. 

I am not concerned about the drag. 

Then thanks for the second answer very useful, but if you pay attention to the previous comment you can notice that we  already answer to that question 

your location of 'Amburg' appears to be in Virginia, USA.  Do you have any knowledge of the UK canals and the boats that use them?

Link to comment
Share on other sites

It might be worth noting that the OP is a naval architect from Germany and the subtelties of some aspects of British humour and so called wit may have escaped him. He was asking a particular question which had been answered in earlier posts: why not cut him some slack?

 

Howard

Edited by howardang
Link to comment
Share on other sites

1 hour ago, Rik_Boat said:

For a canal boat you need to comply with standard requirement and produce mandatory document that are still made by Naval Architect.

I think you may be basing your comment on such as 'Rhine Barges' rather that the UK canal narrowboats which are navigating on a canal less than 1 metre deep and probably only 7 or 8 metres wide

Narrowboats are only under 7 feet beam and are not built to any specifications, it is a 'cottage industry' with manufacturers producing (maybe) 3, 4 or 5 boats per annum

Link to comment
Share on other sites

I think they build the boat based on experience or judgement  and test it rather than design it by calculation. Try British Marine Federation for rules and recommendations.

Perhaps a more engineered approach for a wide beam or Dutch barge.

Mass produced boats may well involve a hull designer...( Naval Architect).

 

Link to comment
Share on other sites

1 hour ago, Rik_Boat said:

I do not think is it funny at all. For a canal boat you need to comply with standard requirement and produce mandatory document that are still made by Naval Architect. Then there is no doubt about the minor complexity of the hull in comparison to other type of vessel. 

I am not concerned about the drag. 

Then thanks for the second answer very useful, but if you pay attention to the previous comment you can notice that we  already answer to that question 

If you are having a boat built then all that is the responsibility of the builder. If you are designing a boat for yourself and getting it built by someone else then take their advice. My advice is to buy a boat off the shelf from someone like Colecraft. If you are designing a boat and building it yourself and you intend to make and sell copies of the same boat then you must, indeed comply with the RCD. this may or may not be relevant in the future (brexit) but if you are making a one off boat for yourself then you do not have to bother with the RCD at all. There is provision in the RCD for amateur builders and they do not need to bother with the RCD. There are conditions but you need to check them yourself as it is a few years since I built a boat.

Link to comment
Share on other sites

48 minutes ago, Bee said:

If you are having a boat built then all that is the responsibility of the builder. If you are designing a boat for yourself and getting it built by someone else then take their advice. My advice is to buy a boat off the shelf from someone like Colecraft. If you are designing a boat and building it yourself and you intend to make and sell copies of the same boat then you must, indeed comply with the RCD. this may or may not be relevant in the future (brexit) but if you are making a one off boat for yourself then you do not have to bother with the RCD at all. There is provision in the RCD for amateur builders and they do not need to bother with the RCD. There are conditions but you need to check them yourself as it is a few years since I built a boat.

Read my earlier comments. The OP is a Naval Artichect who appears to be designing a vessel, in Germany, and therefore your advice, though relevant to UK recreational bats on the inland waterways, are not relevant to what he is involved in. 

 

Hward

Link to comment
Share on other sites

4 minutes ago, howardang said:

Read my earlier comments. The OP is a Naval Artichect who appears to be designing a vessel, in Germany, and therefore your advice, though relevant to UK recreational bats on the inland waterways, are not relevant to what he is involved in. 

 

Hward

I thought he was designing a Narrowboat

Link to comment
Share on other sites

4 hours ago, Murflynn said:

strange that OP asks a specific question which appears rather irrelevant regarding UK canals and narrowboats, but fails to answer the question - WHY ?  

 

if we knew the circumstances he might get slightly more constructive answers,

I think  he has already said that he has had answers and is satisfied with them.

 

Howard

Link to comment
Share on other sites

9 hours ago, howardang said:

I think  he has already said that he has had answers and is satisfied with them.

 

Howard

well he must either be easily satisfied or just plain disgruntled, cos there has been no definitive answer to his query. 

 

Bearing in mind that narrowboat hulls can be divided into 3 parts, 2 of which have more or less fixed lengths for any conventional boat, and block coefficients considerably less than 1, and for the other part Bc is close to 1 but of varying length, it is hard to see how he has drawn any meaningful conclusions from the discussion.

Link to comment
Share on other sites

I suspect he isn't designing a narrowboat but perhaps something for canals in mainland Europe.

If he really is a Naval Architect I am surprised he would  be asking advice on an internet forum.  

Link to comment
Share on other sites

18 minutes ago, Murflynn said:

well he must either be easily satisfied or just plain disgruntled, cos there has been no definitive answer to his query. 

 

Bearing in mind that narrowboat hulls can be divided into 3 parts, 2 of which have more or less fixed lengths for any conventional boat, and block coefficients considerably less than 1, and for the other part Bc is close to 1 but of varying length, it is hard to see how he has drawn any meaningful conclusions from the discussion.

....and then theres the co÷×€efficient of EuropeanLadies narrowboat in the Birmingham area which must be due for a sale again soon.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.