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Old 12-12-2016, 06:35 AM   #41
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Originally Posted by North Baltic sea View Post
....Can someone give me a US concept of coastal cruising, whether it's roads distance from the coast or travel distance to the point a to b, or all boating which does not exceed oceans, or the other?
There was a thread on exactly this subject and there are some very good answers here.
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Coastal vs. Offshore
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Old 12-12-2016, 09:44 AM   #42
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There was a thread on exactly this subject and there are some very good answers here.
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Coastal vs. Offshore
Thank you link Unfortunately, my head is certainly a pea when I could not find an answer

That is, there are no facts which is Costal cruising, there are no facts about the seaworthiness of the vessel, but there is a lot of reviews that are not facts. Probably due to the culture that I love more hard facts than vague stories and images of things seaworthiness of different boat models.
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Old 12-12-2016, 09:51 AM   #43
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Maybe it's just a bad design.

100% agree, I purchased a planing boat but the SD. I believe that NT is also not a submarine very well, because it is designed to work under water. do not understand the answer wrong, a little humor.
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Old 12-12-2016, 11:35 AM   #44
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I have 0 training in naval architecture, but I would think any extra weight added to an upper area of a boat like a dinghy and outboard will change the boats meta center, and have an adverse affect.
I wrote this a few years ago for people like you. It is sail oriented but the basic principles are the same and I should give you a working understanding of stability.

Stability of Boats and Ships

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Old 12-12-2016, 12:25 PM   #45
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Great information as always Roger. Thank you for the link.
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Old 12-12-2016, 03:38 PM   #46
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Nordig Tug 37 stability

There is a lot of generic information available about boat stability. One I found very handy and which describes the basic rules and aspects to be considered is here:
http://www.fao.org/3/a-i0625e.pdf

However I wasn't able to find a specific stability curve for our boat (what a pity for an engineer like me). But which additional value would I gain with such a curve describing only the static stability? In practice the dynamic stability gives the limit!
What we really have to avoid is periodic roll and are braking waves equal to or higher than our beam ...

Most of our trawler yacht hulls have an AVS (heeling angle of vanishing stability) quite below 90 while flooding starts already at a heel angle which is typically in the range of 50 (or even lower). And we know that most of our hulls are reasonably stiff (e.g. roll Eigenperiod in seconds is typically lower than beam in meter), i.e. they have a reasonable metacentric height.
If you really want to you can calculate the metacentric height of your boat based on the results of a heel test (performed at your dock) and correlate this with your roll Eigenperiod measured at the same time.
Doing so you would be able later to check whether metacentric height / roll Eigenperiod have been influenced negatively due to a changed weight distribution, a new heavy antenna in the mast top, ice on deck, added heavy load on the cabin roof or whatever.
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Old 12-12-2016, 03:47 PM   #47
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And we know that most of our hulls are reasonably stiff (e.g. roll Eigenperiod in seconds is typically lower than beam in meter), i.e. they have a reasonable metacentric height.
If you really want to you can calculate the metacentric height of your boat based on the results of a heel test (performed at your dock) .
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Did you read post 44 and thoughts on megacentric height? Other true professionals with requisite NA chops may step forward but the two NAs that peek at this forum are Tad Roberts and Roger Long. Lots to learn from them.
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Old 12-13-2016, 11:23 AM   #48
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Wadden

Did you read post 44 and thoughts on megacentric height? Other true professionals with requisite NA chops may step forward but the two NAs that peek at this forum are Tad Roberts and Roger Long. Lots to learn from them.


sunchaser

Yes, did so and found it valuable. E.g. Roger gives some hints how to establish a fair approximation of the GZ curve based on metacentric height and two heel angles. Certainly that will satisfy the engineer inside me :-)
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Old 12-24-2016, 06:52 AM   #49
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I asked the factory to the stability of NT facts and the answer was negative. apparently a big secret, I can not understand such a policy. Thanks for all the responses and thoughts!
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Old 12-27-2016, 02:42 PM   #50
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I asked the factory to the stability of NT facts and the answer was negative. apparently a big secret, ...
I doubt they have a clue, not because of anything specific I know about the company but just recreational vessel industry practice.

The low freeboard of these boats would likely make them look pretty poor according to the criteria used for USCG inspected passenger vessels. This doesn't necessarily make them unsafe for their intended use but would not encourage a builder to even do the calculations comparing them with commercial passenger vessel standards.
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