Knowing Your Boat's Limitations . . .

[otherthan]

pleas dont get upset my my views, they ar only meant to gain knowledg.

I want to test my boats ability to recover from a capsize and also her boyancy. this is not meant to do her damage, I want to know first hand who safe and what she needs to be safer.

I'd rather know now then finding out at sea while underway to asia.

is this really newbe nonsens, or others have done it also.

rgds

[maxingout]

It's important to understand how your boat performs in unpleasant and extreme conditions. Unfortunately, I don't know any way of finding out except for getting out there and sailing in bad weather.

When I started sailing around the world on Exit Only, I had no idea how the boat would perform in bad weather. We had a couple of heavy weather experiences, and we gained confidence in our yacht. I feel comfortable in wind to fifty knots. I've never had Exit Only in sustained winds over fifty knots, but if I was in those conditions, I would either be using my series drogue or parachute until the storm passed by. If I have any lingering doubts in my mind about how Exit Only would perform, it would be about what would happen to our yacht if there was a rogue wave. We might end up with an inverted catamaran and immediately have one of the most expensive life rafts in the world.

[Bash]

the more boats you sail, the less any given boat will surprise you.

there are many formulas that theorists might argue about, but there's no substitute for time afloat.

[otherthan]

Guy Thompson designed the T-24 for his personal use, he made her tender to attenuate motion sickness, thats the information I have.
T-24 is a 6000lb boat of wich 1500ballast

later on he changed this boat to 6100lb and 2700lb ballast and called the boat T-27 eventho its the same hull.

This is why I am a little concerned about her ability to righten up.

rgds

[SaltyMonkey]

Bash and Maxingout are absolutely correct. We can talk about different ratios, specification numbers, and argue the merits of STYX, AVS and stability curves. We can even take your boat and turn it upside down and see how she behaves. But ultimately these don't mean much because they are controlled conditions with singularities as variables...and the sea is very non-linear and non-deterministic in what she decides to serve. You need to get out and learn how to sail her and build up your experience to those more extreme conditions. You'll have to anyway. Going out to sea on a boat you don't know first is extremely irresponsible and all the "controlled studies" are an artificial and delusional substitute for that experience.

[Pelagic]

Originally Posted by jobi

I want to test my boats ability to recover from a capsize and also her boyancy. is this really newbe nonsens, or others have done it also.

rgds

Jobi…. I think that is a valid question but doing destructive testing is an expensive way to find out.

Much better in the long run for you to study and understand these items about boat stability…such as:

1. Dynamic and Static
2. Free surface effect with flooded bilges
3. Reserve Buoyancy
4. TPCI so that you can then understand what is happening to your waterline when you load up

If you want to perform a very useful test:

Remove all carry on items then measure weights and placement when you put them back on while noting her draft fore and aft, so as to calculate and understand TPCI and Trim issues particular to your boat.

You can even carefully flood the bilges to see how much more she will go down, which are normal classification tests

Lastly keep in mind that a glass jar with a secure lid on it will survive many a storm at sea….. Your weakness in the event of numerous knockdowns is simply keeping the water out… so secure openings are your first priority

Impossible to tell whether the rig will survive because there are too many variables in the forces exerted on a rollover or pitch pole…. Just carry spare blocks and tackle to jury rig.

[Adelie]

Originally Posted by jobi

I want to test my boats ability to recover from a capsize and also her boyancy. this is not meant to do her damage, I want to know first hand who safe and what she needs to be safer.rgds

Chapter 4 of the Cruising Club of America’s (CCA) book ‘Desirable and Undesirable Characteristics of Offshore Yachts’ discusses this issue at length. They offer an involved equation to evaluate capsize resistance and another one that is simplified but in my opinion less indicative. Even less indicative are righting moment/stability graphs.

What I would do is get hold of the book and the info needed for the full on equation and see what the result is. If you can't get the roll moment of inertia values for your boat, you can fall back to the easier capsize screening formula.

Keep in mind that moderately increasing your roll moment of inertia will increase your capsize resistance. Simple things like beefing up your spreaders and attachments and increasing your wire sizes will actually have a positive impact on capsize resistance, and not insignificantly. If you are going offshore in the boat, you might consider adding a removable staysailstay, intermediate shrouds and fixed and running backstays. The added weight will improve your capsize resistance and the extra rigging will improve your odds of keeping the mast in one piece whether you roll over or are just caught in a big blow.

The best advice is to be lucky when you go.

[PAR]

My information of the Thomson 24 is directly contrary to yours Jobi. My data base shows two different boats between the 24 and 27. My notes on the T-24 show a well balanced, responsive boat and a successful racer, which doesn't suggest it's overly tender, in fact just the opposite. Yes, they shared considerably in concept and lines, clearly having a "family" resemblance, but the 27 was drawn out more in the ends.

Regardless, your reaction is typical of most novice sailors (no offense intended). You boat's capsize screen is fairly good, in fact better then most for her class.

You could preform a roll moment test or better yet an inclining test. A full up capsize test wouldn't be advisable, nor necessary. With roll moment data you can pretty much tell what's she's going to do.

More importantly, as has been repeatedly mentioned, is your experience. You can't really tell how she'll react to different sea states until you're in them, true, but you can tell if a specific design is better suited for certain conditions. Your boat is self righting and not especially easy to capsize, so you're in a good place.

Frankly, enduring survival conditions are very rare for most cruisers. The wise skipper avoids these weather patterns and generally doesn't get to know the joy of a hard knock down or good roll over in a yacht. It's one thing to auger a puppy in, on a warm summer's day out on the local puddle in a Laser. Actually, it's pretty refreshing sometimes, but this isn't what you ever want to happen to your keel boat. The prudent skipper will spend an extra day or two in port and let the low pass by, before continuing with the passage. Those that don't heed this advise, often don't add to the gene pool.

If you want to know what these things are like then take a beach cat or dinghy out for a sail on a day with small craft advisories. Try your best not to broach or death roll one under. Sail it until your arms hurt and you're completely hungry, thirsty, fatigued and you've been in fear of the mast breaking for at least a half hour. Then you're about ready for a capsize trial. It's best you learn like this rather then when the EPIRB activates from water contact and you're bleeding from the head, in shark infested waters, at night in a building gale, bobbing up and down as you watch the boat go turtle on you, all the while wondering if your crew has also been tossed in the drink, as you scan the suround area for other flashing lights. Trust me, this isn't what you want to experience and you learn to do the things necessary to avoid it.

You can plan for the worst to a great degree, but not every eventuality can be sorted out, nor will it have sufficiently satisfying results. In other words, sometimes, survival means you lose the boat, possibly a percentage of the crew, but you have placed yourself and the remaining crew in a position to be rescued. Yep, a crappy deal, but there are worse situations too.

The only way to elevate yourself from these types of fears, is to get some sea time under your legs. Experience breeds confidence, this builds character and given a few "rough sloshes", personal integrity and respect for the sea. These are the tools that will get you through, not stability curves and ballast ratios.

Sorry about the rant . . .

[rebel heart]

I'd read Amazon.com: Heavy Weather Sailing, 30th Anniversary Edition (9780071353236): Peter Bruce: Books if you haven't already. There is so much to how different conditions affect different vessels in different ways. I've sailed on boats where being on a run in a following sea was no big deal, and other ones where you feel like always five seconds away from death.

[Pelagic]

Originally Posted by PAR

.... when the EPIRB activates from water contact and you're bleeding from the head, in shark infested waters, at night in a building gale, bobbing up and down as you watch the boat go turtle on you, all the while wondering if your crew has also been tossed in the drink, as you scan the suround area for other flashing lights......

Gee Par.... best to lay off that cheese....too many nightmares....

[otherthan]

you have provided me with alot of good information, many thanks.

Par; you have made my day, to read you talking about T-24 made realise just how lucky I am to have such a boat as my very fist sailboat.
when it comes to sailing I am uneducated, I jumped to conclusions after reading about the thompsons and her 5 different sail plan configurations, plus the newer ballasted T-27, I was under the impresion that the T-24 was a cripeled first attempt.

little do I know, the good thing is swallowing my pride and keep asking the questions, imagine if id put all my ideas to use, they give me my own how to distroy your sailboat forum.

many thanks to all you guys
rgds

[PAR]

Been there, done that. I have a big scar on my forehead and neck where the sheet blocks got me. It was at the mouth of Tampa Bay during hurricane Marco, at dusk, in a well known shark area at feeding time. The boat was setup for heavy weather and the crew extremely experienced, but we got sort of broached/pitch poled in a nasty following breaker that tossed us on our beam ends, then lifted the stern over the bow. Boat and crew were saved. 99% of cruisers will never see conditions like this, we went out looking for it.

[Wotname]

Good luck with your learning curve jobi; the fun thing is that it never stops - at least that is how it has been for me - perhaps others learn faster.

[Christian Van H]

Ah, limitations...

YouTube - Mans_Got_To_Know_His_Limitations_MP4__trimmed__com puter.mp4