Weighing

[skyhawk]

As a routine, are these cruising couple sized yachts ever weighed?
such as when hauling out, do the travel lifts have a scale to measure the weight and locate the CG for balance?

I was just watching Seaventure's 2nd vid on the bulbous bow project. Very interesting to me by the way.

In vid 1 he mentioned something about the number of pounds added.... can't recall the number.... but it strikes me that that's likely a ballpark at best because of the waste from dripping, grinding, etc...

Anyway, this line of thinking about weight added from that project, and how it might affect balance, holding the bow down in heavy seas, etc.... got me to thinking about measuring weight and balance, and considering balance to more finely tune teh boat. I know that most folks will tend to add a lot more weight to something like a cruising boat or RV than they could ever imagine....

 

[jgwinks]

Some travel lifts do have scales. Maybe on each winch, maybe not. The yard I used to store at had a scale, the one I'm in now does not.

 

[DDW]

Most travel lifts are built with scales of a sort (extrapolated from hydraulic pressure data), some of them are still functioning when they lift your boat, but all of them are notoriously inaccurate. It gives you a general number, off by a few thousand pounds. To really know the weight you need to lift it with crane scales that have been recently certified. In theory, if you have good hydrostatic data from an accurate lines plan, you can calculate weight from flotation data (how far does the boat sink) but practically it is not accurate.

 

[jungpeter]

Hi Skyhawk,

You may be over-thinking this topic. In answer to your question, yes, most travelifts do have scales, and they're accurate to probably a few thousand pounds, and can be used to generate the CG of a hoisted vessel.

BUT... You ask about "fine tuning" the boat by (I assume) adjusting the CG to compensate for such non-issues as trim and/or pitching moment. Bear in mind that the typical 40 +/- foot "trawler" that appears to be the norm in this forum has a "weight to trim an inch" (a typical naval architect's metric) is many thousands of pounds, it's unlikely that adding ballast, or moving stowed items, to affect a large powerboat's trim is viable. Or necessary. And definitely lost in the noise when you delve into such esoteric topics as response to wave motion as a function of CG.

And yes, the weight gain over the years by many owners' propensity to add "stuff" is high. But we don't operate ultra-light sailboats, and (multihulls excepted) aren't really that weight sensitive. And while I haven't looked at SEAVENTURE's bulbous bow video, in my opinion, any attempt to alter a recreational powerboat's performance in any substantive way via a bulbous bow addition is akin to picking the pepper out of the fly sh**.

Regards,

Pete