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Old 05-29-2016, 07:01 AM   #1
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Boat weight

How important is the weight of a boat. I'm thinking seakeeping ability. I notice some 34' trawlers weigh about 20,000 lbs. Other 34' trawlers are about 14,000 lbs. This is a significant difference.
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Old 05-29-2016, 07:09 AM   #2
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While weight factors in, CG (center of gravity), beam width, and hull shape also are big factors. Comparing 2 boats only on weight will be very misleading.

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Old 05-29-2016, 07:19 AM   #3
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Here us a direct comparison of two 34' boats. In the mid 2000s I owned a 2006 Mainship 34T. This boat was a flybridge trawler with a wide beam for its size- 14' and weighed 20,000 lbs. Several years ago I sold that boat, moved to the east coast and bought a Mainship Pilot 34, a downeaster style that weighs 15,000 lbs.


The Pilot actually handles a sea way a little better than the 34T. I suspect the difference is the narrower beam and the lack of weight up high with no flybridge.


So, I support OC Diver's view above: sea keeping ability depends on a lot of things, not just displacement.


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Old 05-29-2016, 07:59 AM   #4
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And way too many posters go by simplistic things such as weight or any other one factor of design...so be careful of forum generalizations.

But so far so good...compare many variables...not just weight.

Some seem to be able to determine stability, speed, liveability. etc..etc....from just pictures.....and while the guess may be correct, it is ONLY a guess.

So when advice is general and from laymen, be careful...better to seek specifics from those with personal experience. Many here will give great advice when they aren't guessing.
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Old 05-29-2016, 08:05 AM   #5
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I agree regarding seakeeping, as in open waters. However my experience is that the extra weight sure helps taking wakes in the ICW as well as helping with close quarter handling and lessening the effect of wind.
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Old 05-29-2016, 08:30 AM   #6
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The virtues of taking wakes and windage may be related to size and shape as much as weight.

Similar boats maybe...but again using one variable to describe anything related to a boat is a pretty gross generalization.

And what is not mentioned so far is how the weight is distributed...a little in the right places can be way more effective than just the gross number.
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Old 05-29-2016, 09:01 AM   #7
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One fact in considering weight of a vessel. It is best not to allow the weight of the vessel to be greater than the weight of the water it displaces. I have found this to be a good rule to safe boating.
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Old 05-29-2016, 10:00 AM   #8
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I don't trust maker's weight specs. Often many additional features are added to a boat that may not be included in the listed weight. Things like larger engines, fly bridges, ground tackle etc may not be included if only one weight is listed in the makers data. Used boats will have more stuff added.


Only if the weight is measured at haul out do I trust the data.
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Old 05-29-2016, 10:19 AM   #9
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Our KK42 is listed as having a displacement of 39,500 lbs. at half load. After calculating the weight that full water and fuel tanks would add plus estimating what we've added for cruising/living things, we're around 45,000 lbs. when full. This has bee verified a couple of times during haul or at least we were close. Knowing that ~2000 lbs./inch of immersion, helps to verify the weight.

Don't trust all travel lifts though. A KK42 near us, hauled out this week. The yard said he weighted 55,000 lbs. Which was pretty much impossible given the where the water line and tankage was.
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Old 05-29-2016, 11:31 AM   #10
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Travel lift weight measuring systems are notoriously inaccurate for a few reasons. I've had the luck of having my boat on a hydraulic trailer and was able to go on a truck scale and get true weight. Compared that to travel lift readings and those were all over the place.
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Old 05-29-2016, 12:22 PM   #11
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Handling of a boat represents the intersections of weight total and its individualized placement positions, power source on board, hull shape/form, type seas encountered... and last but not least... the Captain's own capabilities to understand what the boat, its power sources, and the sea/wind conditions require.

Best way to see how a boat handles is to take it out for a romp in some conditions. Now, that = Fun!!

Unfortunately the romp in sea conditions is not always possible during a sea trial for reasons of purchase. In that case it is up to the Captain to be able to intuitively understand many factors regarding handling conditions that the particular boat contains.

Happy Boat Handling Daze! - Art
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Old 05-29-2016, 12:41 PM   #12
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One should be aware that there can be major differences between gross tons, net tons, and displacement weights. You may see a gross or net tonnage on your documentation and it has little or nothing to do with what the vessel actually displaces. Even the calculations for determining gross tonnage is variable based on many hull and superstructure factors.
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Old 05-29-2016, 12:52 PM   #13
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Quote:
Originally Posted by ulysses View Post
One should be aware that there can be major differences between gross tons, net tons, and displacement weights. You may see a gross or net tonnage on your documentation and it has little or nothing to do with what the vessel actually displaces. Even the calculations for determining gross tonnage is variable based on many hull and superstructure factors.
Yes, this. And displacement does not correlate to boats weight in pounds. Tonnage, gross or net is an internal measurement.
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Old 05-29-2016, 01:40 PM   #14
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What needs to be established for any boat is what is the ideal weight for the intended use. If you can establish that then you can say a boat needs to gain or loose weight. Most trawlers would probably benifit from reduced weight. But the shape of the hull and many other things would ideally be changed if significant weight changes were made.

Many trawlers (maybe even most) could benefit from weight reduction. My Willard is a heavy 30' boat but I'm not convinced an overall weight reduction would be a benefit. Other boats like some 34 - 36' foot boats w two heavy engines are (IMO) too heavy. But if you gutted the boat of excess weight ......? "Everything in moderation" comes to mind. Perhaps everything taken to extremes in either direction will be undesirable. But where the sweet spot is would probably best be established by a NA. But a NA will put lots and lots of weight into a boat that he'd rather not have to do for marketing reasons.

But most boats are probably too heavy.
A more important question (that I think we tackled some time ago) is weight distribution. Having too much weight bias in one end is probably much more undesirable than overall weight.
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