fukupananvil
Member
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Using the observation of 4 degrees list for 1000 lb at 11' off center, I calculate metacenter (GM) = approx 1.1'. Feet, not meters. I'm hoping I have goofed.
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SV Seeker
- Thread starter blunderfull
- Start date
Using the observation of 4 degrees list for 1000 lb at 11' off center, I calculate metacenter (GM) = approx 1.1'. Feet, not meters. I'm hoping I have goofed.
fukupananvil
Member
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They are lifting 1000 lb at 132" = 11', got 4 degrees.
fukupananvil
Member
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Thanks for pointing that test out - I had quit watching all his videos when that was done, so I missed it.
Panope
Super Anarchist
Brilliant.
When two completely different methods arrive at the same answer, it indicates a high degree of accuracy.
Now, for boats of this size, what exactly does a GM of 1' or 1.1' predict?
Steve
Panope
Super Anarchist
Was the GM of the infamous "Anacortes FLIPPER" ever calculated/published?
mathystuff
Super Anarchist
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And that's before even more steel crap has been welded on well above deck level.
mathystuff
Super Anarchist
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It's super low. For even a small sailboat it should be around a meter.
Means boat will be very tender and prone to capsize.
Yes, about that.
I'd say "very easily knocked down by wind if all sails are hoisted in 12-15 knots in a beam wind" rather than capsized. Hard to know what the angle of vanishing stability is but narrow beam boats are usually OK. It's so far away from what is "normal" it's hard to guess.
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Once knocked down on her beam ends, the school bus windows may be challenged(compromised) thus allowing a rapid ingress of water which in turn may begin dreaded down flooding through any number of unsecured access points in the "pilot house".
Furthermore, this BSO has very little in the way of solid volume up high enough to resist rolling over and staying there.
Furthermore, this BSO has very little in the way of solid volume up high enough to resist rolling over and staying there.
mathystuff
Super Anarchist
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Fair enough. There might be a slight difference in meaning between german and english here. Is capsizing a complete turn on the back only in english? The german equivalent kentern also is used for knockdown, while turning on the back would be durchkentern. Lit. through capsizing.
kent_island_sailor
Super Anarchist
In English, a knockdown is something that happens when a sailboat is healed over at or near 90 degrees. This is something any decent ballasted sailboat can recover from with no issues.
Capsize usually means going all the way over. The end result might be a 180 or 360 back to upright or remaining inverted, which is called turning turtle. This happens to some dinghies frequently.
The BSO Seeker does not seem to be a boat that recover from a knockdown with any degree of certainty.
Panope
Super Anarchist
I remember a credible account of a big steel Colvin (schooner?) that capsized and sank somewhere in Northern Europe. The vessel had been modified including having additional fuel tanks (above WL) which raised the CG.
Does anyone remember that event or have a link?
On a related note, I am in the process of eliminating Panope's (above waterline) fuel tanks and converting the empty keel space to a fuel tank.
Does anyone remember that event or have a link?
On a related note, I am in the process of eliminating Panope's (above waterline) fuel tanks and converting the empty keel space to a fuel tank.
mathystuff
Super Anarchist
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Thanks. There definetively is some shift of meaning in the translation than.
Wiki states capsize is going over max selfrighting angle, while kentern is putting a boat over on (at least) its side. For self righting sailboats those aren't the same.
I doubt it will matter for Seeker.
Israel Hands
Super Anarchist
I think with SVSeeker we should work the word durchfall in there somewhere.
Panope
Super Anarchist
Here is the Colvin sinking report:
STATE MARINE ACCIDENT INVESTIGATION COMMISSION FINAL ... https://pkbwm.gov.pl/wp-content/upl...ty_obce/FINAL_REPORT_WIM_15_15_Down_North.pdf
STATE MARINE ACCIDENT INVESTIGATION COMMISSION FINAL ... https://pkbwm.gov.pl/wp-content/upl...ty_obce/FINAL_REPORT_WIM_15_15_Down_North.pdf
kent_island_sailor
Super Anarchist
My own boat has had plenty of knockdowns over the years, but has never tested the maximum self-righting angle, with is about 125 degrees for me.
Fah Kiew Tu
Curmudgeon, First Rank
Yeah I used keel spaces 11 through 15 as fuel tanks. IIRC I got a total of 180 litres which is ample. So of course I added extra tanks P&S which I don't fill and take up space I could have used for water tanks.
Be aware that this is going to reduce your aft buoyancy so you may have to play with the trimming ballast. On launch I was stern heavy and had to move ballast forward. Fortunately I'd listened to Tom and made the ballast moveable lead bricks.
FKT
So to compare that Colvin report with a worst case analysis showing GM as 0.88m and this analysis showing 1.1' for Seeker - seems bad - are we reading correctly? That report goes on to draw conclusions using other derived stability rather directly using GM - am I reading all correctly? - but GM this bad would be expected to result in much worse derived stability figures? Again, is this a valid conclusion?
fukupananvil
Member
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Thanks. You inquired a while back regarding any available drawings of the thing. As I've been puzzling over his videos I generated a crude sketch to get oriented in what I'm looking at. His 3 "waterproof hatches" below deck are sealed with Smoothon Corp Vytaflex 30, which is sold as a concrete molding material. I stumbled upon that while identifying which door was which and where each was located for video viewing purposes. I was curious which way they swing. My sketch is not a proper drawing by any means with all sorts of liberties taken with not using hidden lines, moving the pilot house off to port, nothing to scale, etc., however I offer it here as it may be of some use. I still haven't figured out if 19' is beam to the nerf bars or the hull plate. Anyhow, what I see are 3 deck openings with sliding covers. There are 2 companionways, both on starboard, one into the cargo hold and the other into the foward bunk. Both companionway covers slide to starboard to close. I believe each has an arched top opening in each bulkhead with no sealing door where each penetrates its bulkhead. The cargo hold has forward and aft sliding covers. Again, no water seal. I don't know what penetrations are in the deck inside the pilot house other than a porthole which can be closed. BTW I forgot to add chains and anchors to the weight calc. When I consider a knockdown or large wave I don't like what I see. Think that's been stated before by many. Looks like towars stbd. would be the worst.
