When is flotation not flotation?

[K.C. Walker]

If you are lucky enough to live near the desert, open up your access ports and go for a ride. When we went out to the NACR at Huntington Lake, California a few years back the boat lost 10 pounds of water weight driving thru the desert. This was a boat that always weighs in at exactly 575 so we had to add 10 lbs of lead to bring her back up to the minimum weight requirement.

Well, that's very interesting.

KC

[MrPlywood]

Good info all around. This job is on my list. I have the inspection ports, just need to find my noodle supplier (or cut up the billets that I mentioned before) and some time.

Also, I took the liberty of rotating ctenidae's photo to the correct orientation so it's easier to view...

[ctenidae]

I bought some air pillows used to hold up the cover on an aboveground pool. $15 each, heavy duty vinyl, designed to stay inflated all winter under freezing conditions, so I think they ought to be okay in the relatively mild conditions under the seats. Only thing I don't like is depending on single cells, but I'll just add checking them everytime I go out to my preflight cehcklist. Still want to fill the tanks with poured in foam, just haven't gotten around to checking local dockyards to see how much it would cost (figure tipping the boat so the foam pours all the way in would be best).

[GreenLake]

I would be troubled by two worries:

If you misjudge the foam's expansion rate, you could blow apart your seats. Also, if you leave any voids, and they fill with water, you can no longer get at them for inspection and/or remediation.

About air bladders: bladders designed for continuous outdoor use would seem to be fine - as long as they can handle being baked more in the hot sun under the seat (depends on where/how the boat is stored, difference in the seat vs. bladder reflectivity, etc.).

The other aspect to think about is expansion again. A tightly sealed bladder, if inflated too strongly on a cold day could force apart your seat on a hot day, given the right circumstances. At least, there you can allow for the expansion up front, by leaving some slack.

[ctenidae]

Yeah, the permanence of pour-in foam is a concern. I think if done properly (by a boatyard with a crane, for instance), if could be highly effective, providing floatation, stiffening, and seat insulation. But, if anyone ever wanted to change it, it would be nearly impossible. Poured in layers, I wouldn't expect the expansion to be such a problem.

I'm really not sure on the conditions the bladders will be subjected too. The boat lives on the water all season (or will, anyway). The deck will be white, the water stays cool, and we'll use a boom tent, so temperatures shouldn't soar or swing but so much.

My biggest concern on tehe bladders is truly catastrophic failure- if I lose a bladder for whatever reason, that's 1/3 of my floataion gone, and unrecoverable while out. It's kind of unlikely to lead to sinkage, but that is a concern.

[K.C. Walker]

I don't see why there would be a concern about the bladders expanding differently than the seat tank itself, provided the seat tank is well sealed. It seems to me that it's just an added seal. As long as they're tough enough to withstand some amount of abrasion from the inside of the tanks, I don't see why you would worry. Being that Cape Cod Shipbuilding recommends sealing the tanks and leaving them empty, the bladders seem like reasonable added flotation insurance. As long as you had a way to check them easily, I wouldn't think there would need to be much concern. Even if they weren't inflated tightly into the seat thanks they would still probably provide more flotation than foam or something like pool noodles where your tank seals to fail.

Do these pool pillows seem tough enough to you? Are they going to be easy enough to get in and out of the tanks? Will you be able to get to the inflation valve reasonably easily?

I've contemplated the pourable foam idea myself. Of course, the main concern is that it is a, more or less, one-way street. However, it does seem to me that it would add stiffness to the boat. How are Boston Whalers made as far as the foam goes? They seem to hold up quite well. Also, the way that Sunfishs are made is that they use blocks of foam and then pourable foam to adhere them to the deck and the hull. I think this would be a less expensive and just as effective a way to fill the seat thanks. I guess the stuff kicks really fast and that is the tricky part of using it.

Unfortunately, right now, there's still a bit of snow on my boat cover and no doubt more to come.

KC

[ctenidae]

I think the bladders are tough enough. Fortunately, my hull was made with all woven fabric, so the inside of the tanks is pretty smooth- no prickles from chopped mat. The valve on the bags is at an end, so shouldn't be a problem orienting them near the access ports. I am going to inflate one and set up a test rig with weights on it to get an idea of how airtight the valves are, but teh guy at teh pool store said they're good, and generally don't need to be reinflated at all over the winter.

[MrPlywood]

Finally got around to adding the noodles to my boat. Although, after reading Moose's thoughts in this thread:

http://forum.daysailer.org/forum/viewtopic.ph ... highlight=

...I'm not sure it was needed, but I had already bought the noodles and inspection ports so I went ahead with the job. One tank was mildly compromised, as I could see daylight through the seams in some areas, so maybe the flotation will come in handy.

I also fit some into the space under the gunwales along the length of the seats. 6 noodles per side fit into the space nicely (4 full length stacked 2 x 2, 2 more cut in half and stacked the same way).

[Melbourne55]

I spoke with a fiberglass guy in Vero, Florida. He has tons of experience. He recommends soda bottles with some silicone on the cap. They never soak up water. If you sail in cold weather they may shrink but they lack the hole in the middle of a noodle. He has never seen a leak. Free and easy to find on recycling day.

[ctenidae]

I was seriously considering the soda bottle option, but was concerned about how much they'd rattle around in the tanks.

The float bags were an utter failure- couldn't insert them effectively, and they didn't inflate well. And then they developed tiny pinpricks.

[seandwyer]

I too considered the soda bottles, but also wonder what sort of racket they may make, knocking against one another inside the seats. However, if someone did go with this option, how many should you put in there?

Seems like we know how many noodles will fit in the boat, but has anyone ever come up with how much buoyancy one noodle provides and if the number commonly fitting beneath the benches and inside the bow tank is really enough flotation? I don't weigh very much and a noodle really doesn't float me - 2 sort of keeps me floating, but wouldn't if the water were rough, so I started wondering - a boat, the crew, the gear - are 75 noodles worth of flotation really enough?

One more question that I'm pretty sure has been answered already, but persists to poke and prod within my own curiosity: Is there any proven way to make the boat into something that would be close to self righting? Even if you had to stand on the centerboard - but someway of either adding weight or flotation beneath the rails or perhaps by some other means I hadn't considered that would enable a guy to get the boat back upright without assistance. Anything?

[ctenidae]

According to the formulas here: http://www.glen-l.com/weblettr/weblette ... ation.html which seem reasonable, and assuming 1.8 as the specific gravity of solid fiberglass, I'm coming up with a negative bouyancy for the 575 pound daysailer of about 255 pounds (not accounting for teh higher negative bouyancy of the mast, rigging, etc etc).

Assuming a 2lb density for the swim noodles, which seems reasonable (I've seen similar looking polyethelyne rated at 1.7), a 2.25" diameter 60" long noodle with a 1/2" hole in the middle is about 0.04 cubic feet. The net boutancy of a noodle, then is 2.68 pounds (62 lbs per cf for fresh, 64 for salt water, less the foam's weight = 60 lbs per cubic foot net bouyancy). Which means you need at least 95 noodles to make a daysailer unsinkable. That's a lot of noodles.

[seandwyer]

Thanks ctenidae

....and if 95 is the number, it isn't the number I've been hearing. I had planned on buying about 75 noodles which is what I have heard people can fit in the bench and bow tanks. If this isn't really enough buoyancy where are you guys adding more to equal the 20 odd extra noodles necessary? Plus, gear adds weight, and anyone out there is going to tell you that if you go in, stay with the boat and hang on to the side, so that's adding even more weight.

Any other opinions?

[Elk River]

One thing that hasn't been mentioned is the fact that should a DS capsize, the floatation tanks won't immediately flood or fill up, assuming, of course that all plugs are installed. Even if the seat tanks are cracked, water will only seep in, perhaps. By the time the boat is able to be righted and most of the offending water removed, there shouldn't be that much water in the seat tanks themselves. I could be very wrong in this, but it is just my thought. My wife and I are rebuilding #2332 and have 6" inspection ports in the sides of the seat tanks and in the 'forecastle'. We used less than 200 plastic bottles of various sizes to fill all 3 cavities. There is no rattling around as they are jammed in. The only noise is some expansion noise in the heat. Just thought I would pass this along.
To help prevent turtling, we intend to have some floatation sewn into the head of the mainsail as was mentioned in one of the Daysailer articles in the May/June issue of Small Craft Advisor. We don't race, so 'ruining' the main is not an issue with us.
Elk River

[Alan]

I'm thinking about placing an inspection port about where the photos show, but on a 1980 DSII. Anyone know whether I'll find foam in there, or air space, or Jean LaFitte's ghost?