Soda bottle flotation

[TIM WEBB]

Hi All,

I'm getting ready to pull the old foam and put in soda bottle flotation on The Red Witch, and have a few questions:

1. Where are the best locations for the 2 seat and 1 bow inspection/access ports?

2. Do the regular 2 litre bottles work? I've been collecting. I would seal the caps (what silicone works best?), and collapse them slightly to compensate for expansion (it's HOT here!)

3. How many can I reasonably expect to be able to fit into each space?

Below are a couple pics I took of the bilge through the existing starboard sole pivot bolt access port, showing the area below the starboard seat. Is that "filler foam" below the white foam normal? I reached under there, and it all feels like one big loose chunk ...

Any and all further advice would be greatly appreciated!

Thanks,

- Tim

[algonquin]

There are conflicting opinions on this subject. Personally I am an advocate for this type of flotation over foam or noodles.

The 2 liter bottles work great. I used a clear silicone sealant. Some of the 35 plus year stuff. I don’t think the brand is all that important for what you are doing. I used 6 inch access ports. One in the bow and one on the forward side of each seat. I can’t recall the actual number needed but about 30 fit in the bow cavity and about the same in each seat. Also I sealed the access ports.

Like any added flotation, you should inspect it each year to make sure it is performing up to your expectations. Brad

[seandwyer]

Hey Guys,

Maybe some of you have seen the news about the boat that sailed from CA to Australia - made mostly of only 2 litre bottles. I'll put a link in below.

Anyway I watched a video and I think they worried about the expansion and compression of air in the bottles as has been brought up on here. There answer was to fill them with CO2. Later in production they got a CO2 dispenser for the bottles (because they had 1000's to fill) but initially they just used dry ice. They took the bottle, compressed it as much as possible by hand (removing the air) dropped a few morsels of dry ice in and then place the cap on slightly tight. In a few minutes the bottle was full - even pressurized, then they tightened the cap all the way. By leaving the cap only slightly tight, as the CO2 gasses, it pushes any air left in the bottle out. Now, maybe someone with a little chemistry experience can chime in and let us know if this is a better idea than just using the air that happens to be in them. It didn't look like it would be that much work if you got some help, but between putting the dry ice in the bottles and packing them into the boat, I'm sure it's at least a day long project.

Anyone have an idea how many 2 litres it takes for a DS 1?

Heres the boat:
http://www.theplastiki.com/

[kokko]

As a chemist, I will respond.
Loading the soda bottles with CO2 provides no benefit. It is a waste of time and money. What you want is positive flotation - something that is less dense than water. Filling a 1 liter with CO2 or air makes no difference. CO2 has a density of about 2g/liter and air is about 1.3 g/liter. the difference is negligible in comparison with the weight of the bottle itself. If a one liter bottle weighs 10 g, then it will weigh 12 grams filled with CO2 and 11.3 grams filled with air. A difference of 0.7 grams per bottle. If you need 100 bottles, the difference is 70 grams total (2.5 ounces)

it is a good idea to compress the empty bottles slightly to allow for the expansion. if you cap the bottles when the temp is a cool 50F, then the air trapped inside will expand about 10% when the temp is 100F. If well capped, the bottle will contain the pressure without problem.

[kokko]

If you remember the gas laws from high school (Boyle's, Charle's and Gay-Lussac's), you will remember that gases are essentially identical when it comes to changes in volume, temperature and pressure. Co2 and air (which is 80% nitrogen) can be considered ideal gases when it comes to coefficients of thermal expansion (change in volume per change in temperature)

[bm1981]

I've got a cockpit full of 1 and 2 L bottles 4 6" ports, 2 4' ports to replace the old leaky ones and a hole saw on order.

Any tips tricks or gotchays that I should be aware of?

I plan this weekend to drill the holes, pull the foam and squeeze and silicone the bottles. Then I'll let the the boat sit with all the ports open (or uninstalled) for the week with the cover up and let it dry out. - If needed-

The following week I'd like to start the bottom job I'm still trying to figure out the water line. There is an existing one but it looks way to low, so i'm thinking of painting to the existing WL but more likely below the curve of the hull so its truly the bottom side. Then try to blend in the new higher line after it sits on the mooring for a few weeks. The I can paint the new WL while on the trailer.

[algonquin]

Bm1981 - Not sure what you mean by “squeeze” the bottles ? Brad

[bm1981]

I mean to reduce the air in the bottle by 10-20% by squeezing their sides then capping them so that when it gets really hot in the summer and the air in them expands they don't all explode in my seats.

I'm not sure if I'm going to have time to do everything I want to do this weekend but if i get the bottles ready I can throw them in the seat tanks one night after work. I would imaging siliconing the caps on will be time consuming.

[TIM WEBB]

Hey all, thanks for the replies/info (I had forgotten I posted this!).

I've actually been putting off this project for several reasons, but mainly because as far as I can tell, the foam in there is dry. Also not sure how I would get it out, and not sure if the soda bottles would stay put in there. However, I am getting ready to install seat and bulkhead inspection ports in the cuddy anyways, so I guess I'll get a better looksee/feel of the foam once I do that ...

- Tim

[bm1981]

Has anyone with a DSII done this mod?

I've run into a few things that made me want to pack it in for the day..

Firstly, I opened up the bow. There is nothing in there, no foam just a straight shot to the bilge.

Second, holes in the front of the seat tanks... yeah that a hole too close to measure from the cuddy to the seat tanks. Besides the port side has the cooler built in so you can't drill a hole there and get into the seat tank. Option 2, was to put the inspection ports on bottom of the seat fronts, but then I got to thinking that since there isn't foam in there why bother adding bottles? My main goal was to eliminate the excess weight but since there isn't any I'm at a loss.

Would it be prudent to leave it as is, and add bottles to the bow tank and bilge and leave the seats as is?

[GreenLake]

Removing soggy foam is one aspect of this type of project. It doesn't seem to apply to your boat. The other aspect is to prevent any of the flotation spaces from filling entirely with water in case of a small leak. In other words, it's mainly a form of added insurance.

If you had a way to reliably and frequently assess whether your tanks are airtight, then you might feel that this added insurance is not worthwhile. Bottle flotation would help protect your boat in case it got hulled (whether by hitting a rock, or an unfortunate collision).

I've started sailing in mixed fleets, and since then my appreciation of what the likelihood and result of a collision might be has definitely changed...

[bm1981]

GreenLake,

Being that I've already had the boat on its side and it totally filled with water, I don't know how it didn't sink.

After walking away from the boat for a hour I realize that it's in my own best interest to add flotation. But I need to think about it for a day.

I think, what I'm going to do is pull out the 2 - 2X4s at the bottom of the seat well tanks ( in the bilge) drill a 4" hole and fill it w/ bottles. I need to verify that a 2L will fit thru a 4" hole. I'd put the hole on the vertical part of the bottom of the seat.

I know the DSI guys recommend a 6" but I'm not removing foam, besides a 6" hole in the seat will be a tough cut, I won't be able to get a powertool to the deck to cut the bottom 1/3 of the hole.

[GreenLake]

Ways to cut holes: I cut a hole for an inspection port by drilling a closely spaced circle of small holes and used a screwdriver to break the little bits between the holes. (And a file to even out some stuff - however, because of the "lip" on the inspection port covers, the hole does not need to be "neat").

That approach, or something similar might work where other tools fail. (For example, drilling the holes at an angle wouldn't matter).

[bm1981]

Quick update...

The bow tank just under the front half of the cuddy floor took 39 2L bottles reduced in size 15-20%

The starboard seat tank has a 4" hole with 4 2X4s and the bottom 2 attached together with a poured / sprayed on foam.

The port tank can kiss my *^* from the cooler back the entire tank was full of foam with that sprayed in stuff all around. Essentially it was one gigantic block of foam. The top was dry but I was literally wringing out the bottom 1/3. After 2 hours with my hand in a 4 inch hole, both of my arms look tiger striped, but the foam is out.

In both cases I noticed that there was serious condensation on top of both seat bottoms. I'm leaving the ports all open to dry the boat for a few days.

Now i need to figure out how to get all the foam/epoxy and 30 years of crap out of the bilge to keep the transom drain clear. Suggestions?

When this is done, I'll post a writeup and things I've learned / would do different.

For what its worth I took out 4 trash bags of foam, conservative estimate 60+ LBS of wet foam.

[Alan]

"Now i need to figure out how to get all the foam/epoxy and 30 years of crap out of the bilge to keep the transom drain clear. Suggestions?"

I used a 5hp shop vac with a 2-inch hose to slurp about 5 to 6 inches of water out of the bilge, and then set it up as a blower to finish the job. (Yes, you're not supposed to use a shop vac as a bilge pump, but in my neighborhood, you show up absolutely dry or the inspectors don't let you in the water.)

Seems to me this would work on damp solids.