We had 6.5" of rain Tuesday afternoon/evening here in Chattanooga. A good bit of flooding.
This got me to thinking - If I'm cruising and get caught in rain, how much rain would it take to sink my boat?
I'm anchored in a quiet cove and a gully washer rolls through while I'm sleeping (or trying to sleep) in my popup tent (which of course will shed no rain out of the boat). What would sink my boat?
Water weighs 8 lbs per gallon. There's 231 cu.in. of water in a gallon. Disciple Ship is 15'6" long with a beam of 60". The designer says she has a displacement of 610 lbs. with a hull weight of about 200 lbs. Let's say I weigh 185 and am carrying 100 lbs of gear for an extended cruise. How much water can I take on? How many inches of rain would it take to sink my boat?
I don't know how to calculate surface area of a curved surface like the footprint of a boat, but I'm estimating that the area of my boat is around 9000 sq in. For every inch of rain I would be adding about 39 gallons of water and almost 300 lbs of weight to my boat!
Maybe I shouldn't be out in a rainstorm!!!!
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Dale, Your statement:
Quote from: Captain Kidd on Aug 14, 2025, 08:53 AMI don't know how to calculate surface area of a curved surface like the footprint of a boat
Applies to me, also! :-[
However, living in south Florida most of my life and being Florida Keys adjacent, I've seen and experienced things that would give me less cause for concern, than what you are expressing.
Down there in the Keys, it was common lore during Hurricanes to take a small skiff and get as far in the Mangroves as you could manage, tie it down with every line you could find, fill it with water but also,
load it up with rocks or other ballast, because even completely flooded, most boats would still float. And this was with fiberglass and aluminum skiffs, not wooden boats which do a fair job of floating, all by themselves!! :P
Being held forcibly to the bottom with weights and tied in place, kept the hull from being affected as much, by the storm surge.
During a particularly severe Hurricane one year, I took a page from the Keys folks and stripped the inside of my 18' sailboat, removed the mast and all the rigging, removed the wheels, placed 4X4 blocks between the leaf springs and the frame (to keep them from breaking) :o and flooded the entire hull with water. I also faced the hull into the expected wind directions (remembering that Hurricanes don't blow, they suck; winds rush towards the low pressure of the whirly-girl) and staked down the tongue of the trailer and hoped for the best.
After the Hurricane's violence had passed, I found my trailer had ripped the 3-foot rebar metal stakes loose and rotated the trailer and hull around into the low pressure area, as the Hurricane passed by.
A Venture 21 sailboat on the same street as my block, not similarly prepared as my boat had been, rolled multiple times and ended up about 3 or 4 doors down and was eventually totaled. A Bass boat also in my neighborhood was never seen again, as was a Jon boat ripped from its' trailer. Trailer remained, no idea as to where the Jon boat ended up.
In true Tom Sawyer style, I allowed all the neighbors to remove water from inside my hull, for the purpose of flushing their toilets with 5-gallon PVC buckets, since there was no water pressure from the city, just then. They all thought *I* was doing THEM a favor!! 8)
Got my hull bailed out for FREE! ;D
Finally, one year in a Columbus Day Cruising Regatta a decades old manufacturing defect, caused two screws to punch holes in my hull. It was pretty rough weather and rainy, that year, so our companionway hatch was kept closed.
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After we finished the race, we were shocked at the amount of water below. We limped in to Bill Baggs State Park to begin bailing. After two hours or so, we realized we were losing the race with water displacement.
Reluctantly, I decided to abandon the race (CDCR is a 2-day race) and try and make it back to the ramp at Crandon Marina 7 miles away, in a constant rain. At one point, the water in the cockpit and the water in the cabin, were at the same level as I tried mightily, not to think about my electrical system! :o
But we were still sailing.After retrieval, note how close to the top of the fender the tire is and how flat the tire looks; we had to take it to a gas station to get more air in the tires, to make it home.
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The next day, STILL draining:
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Yes, boats sometimes, DO sink.
But they have to work at it.
Hope this provides some insight,
Charles Brennan
Cap'n:
A couple of comments:
1. Does your designer report a designed immersion rate of inch/lb? That is: how much further will the hull immerse into the water from its designed lines due to additional weight carried.
2. I presume, you may want to confirm, that the reported design displacement of ~600lb refers to its design lines. So then you can carry ~200lb of boat structure, ~200lb of crew, and ~200 lb of gear and still be at design immersion. I doubt that it means that at 600lb the boat will be immersed to its gunwales.
Regards, Roland
Captain, have you tried a capsize recovery? I unintentionally capsized my 15' 9" and 6' 1" wide wayfarer on a high wind day. Surprised by this is an understatement. I quickly righted the boat but It was full to the seats of water. It was a lot of water as the hull is basically empty as the seats are just boards. It does have mostly water tight bow and stern compartments for storage and floatation. I had a bucket and after a short while realize how long it would take me to bail it out. So, I just opened the single scupper in the bottom center of the hull next to the centerboard trunk of the boat and sailed the water out. I think they are called a vernier scupper and as long as the boat is moving they will drain. I also have them at the back of the cockpit in my scamp. Duckworks carried them, but alas they are no more. The moral of the story is the boat held a lots of water. I can't tell from the overhead photo of your boat but it looks like you also have bow a stern flotation compartments. Is that right?
Quote from: Charles Brennan on Aug 14, 2025, 10:25 AMYes, boats sometimes, DO sink.
But they have to work at it.
Hope this provides some insight,
Charles Brennan
Yes, I'm probably worrying for nothing (except in the event of a capsize). A heavy rain probably just means a lot of bailing.
Quote from: Roland of Macatawa on Aug 14, 2025, 12:12 PMCap'n:
A couple of comments:
1. Does your designer report a designed immersion rate of inch/lb? That is: how much further will the hull immerse into the water from its designed lines due to additional weight carried.
2. I presume, you may want to confirm, that the reported design displacement of ~600lb refers to its design lines. So then you can carry ~200lb of boat structure, ~200lb of crew, and ~200 lb of gear and still be at design immersion. I doubt that it means that at 600lb the boat will be immersed to its gunwales.
Regards, Roland
Yes, that displacement figure has me confused. I usually figured that was pretty much equal to the weight of the boat. I'll check with the designer and see what he says.
Quote from: Doug SC on Aug 14, 2025, 01:44 PMCaptain, have you tried a capsize recovery? I unintentionally capsized my 15' 9" and 6' 1" wide wayfarer on a high wind day. Surprised by this is an understatement. I quickly righted the boat but It was full to the seats of water. It was a lot of water as the hull is basically empty as the seats are just boards. It does have mostly water tight bow and stern compartments for storage and floatation. I had a bucket and after a short while realize how long it would take me to bail it out. So, I just opened the single scupper in the bottom center of the hull next to the centerboard trunk of the boat and sailed the water out. I think they are called a vernier scupper and as long as the boat is moving they will drain. I also have them at the back of the cockpit in my scamp. Duckworks carried them, but alas they are no more. The moral of the story is the boat held a lots of water. I can't tell from the overhead photo of your boat but it looks like you also have bow a stern flotation compartments. Is that right?
I have not done that yet though I know I need to, especially if I'm going to do any extended cruising which is my plan (I turn 70 in January and am thinking of an extended cruise on the CIY). My boat does have three flotation chambers - one in the bow and two aft. The home made deck plates leak some. My hope is that I'd get the boat upright before too much water intruded. I purchased 3 deck plates from duckworks before they closed but I haven't installed them yet. I kinda hate to mess up the homemade ones. The self-draining scuppers are an intriguing possibility. I've heard of them but never used one. I'll have to investigate that. I've only capsized once and that was in my 11' dinghy. I got her back up but did not have anything to bail with (never made that mistake again). The deckplate over the forward chamber leaked and the bow went down so I had to be rescued.
If you can, let us know what Clint says about it.
I enjoyed meeting him last summer.
Quote from: Spot on Aug 14, 2025, 08:09 PMIf you can, let us know what Clint says about it.
I enjoyed meeting him last summer.
Will do. Sent him a message today. He was great to work with while I was building my boat. Really nice guy.
Well you can test it ;) like I did with my Bateau FS14 skiff. Launched it then tied it off to the ramp dock, drove the truck to the park area then fooled around for a bit before I came back, noticed it was a little low in the water. Wait, did put in the plug? :o No I didn't. It still had lots of room, water to rub rail, the trim was good, and the boat had found its new equilibrium, was not straining at the lines. I could get in it without it sinking. So in a rain storm, I would just pull out the plug so the water inside did not get past that equilibrium point. When I built it I did put foam under the decked area and some extra boxed areas of foam back where the motor sits.
The test was non intentional, a little embarrassing, although not many at the ramp, and a little hard to winch it onto the trailer so I could pull and drain, but at least I learned something. And if a rainstorm came when I can still get on plane, just take the plug out to drain as I go, but no, that wouldn't work on a sail boat or traveling at displacement speed.
I say this as someone who decades ago practiced naval architecture and threw all those thumbrules away for the nuclear industry.....
Length times beam gives you the starting surface area (square inches). Boat form silhouette is probably 60-80% of that area, depending on how fine the bow & stern are. Take that area, times the expected draft and/or craft height (depending what you want to calculate) to get a volume (cubic inches). Again, depending on fineness of the lines, about 50-60% of that is actual displacement. Lot of assumptions in that method, but it'll be a baseline to compare against and good enough for Mythbuster math.
Having extremely flooded two sailboats and sunk two others, I can say my reaction each time was an extremely long period thinking "How is this still floating?!?" then a rapid "She gone..." of about a minute.
Quote from: Travis Chapman on Aug 15, 2025, 09:55 PMLot of assumptions in that method, but it'll be a baseline to compare against and good enough for Mythbuster math.
Having extremely flooded two sailboats and sunk two others, I can say my reaction each time was an extremely long period thinking "How is this still floating?!?" then a rapid "She gone..." of about a minute.
Good estimates and thanks for sharing your experiences.
Keep in mind that semi sunk and capsized are very different conditions.
All the discussion so far are about semi sunk. As the moveable ballast increases (water) the stability decreases. It is important to stay as near the center of you vessel as possible while bailing it out. Moving to the gunwale to bail may cause the vessel to lean far enough that way for water to come over the edge, or even worse continue to heel to 90 degrees and beyond.
Getting it righted, and yourself back aboard is a major feat.
As you bail, do not stress about water that does not go overboard when you toss it, celebrate that which does fall outside. Of course, toss down wind! As the vessel rises, move toward the stern to bring the water to you as that is wider and more stable.
When I was about 70, sailing a Laser with my young grand daughter, we capsized (my first ever) and righting the unsinkable craft was difficult, getting back in even more so for me, Without her weight on the other side, my weight coming aboard would have re capsized it.
Krusen
Quote from: Krusen on Aug 16, 2025, 12:12 PMKeep in mind that semi sunk and capsized are very different conditions.
All the discussion so far are about semi sunk. As the moveable ballast increases (water) the stability decreases. It is important to stay as near the center of you vessel as possible while bailing it out. Moving to the gunwale to bail may cause the vessel to lean far enough that way for water to come over the edge, or even worse continue to heel to 90 degrees and beyond.
Getting it righted, and yourself back aboard is a major feat.
As you bail, do not stress about water that does not go overboard when you toss it, celebrate that which does fall outside. Of course, toss down wind! As the vessel rises, move toward the stern to bring the water to you as that is wider and more stable.
When I was about 70, sailing a Laser with my young grand daughter, we capsized (my first ever) and righting the unsinkable craft was difficult, getting back in even more so for me, Without her weight on the other side, my weight coming aboard would have re capsized it.
Krusen
As I mentioned earlier, I have only capsized once and that was in my 11' dinghy. I was able to right the boat and reenter by simply rolling over with the boat. I would have been ok had I had something to bail with. I really do need to do capsize test though I really want to - dah! Maybe while it's in the 90's this week. Yippeeeee!
Quote from: Captain Kidd on Aug 14, 2025, 11:16 PMQuote from: Spot on Aug 14, 2025, 08:09 PMIf you can, let us know what Clint says about it.
I enjoyed meeting him last summer.
Will do. Sent him a message today. He was great to work with while I was building my boat. Really nice guy.
I finally heard back from Clint. He's in the process of moving his shop and got behind on answering. He said the 610 lbs of displacement was the amount of weight (total:boat + crew + gear) that would bring the boat to her designed water line which would still leave a "decent bit of freeboard to work with".
Now let's see... boat 200, me near 200, gear for a week @100. That leaves an inch or so of rain would just about do it. Better have a good bailer aboard! LOL