Flotation Foam

[avd155]

I'm wondering if anyone has information on flotation foam.

I have a number of small and 2 semi-large areas I want to fill with foam in order to add some reserve buoyancy, but I haven't really seen any first hand accounts of boat repairers like us actually installing/using foam. Does anyone have any experience with installing foam in a boat? Or perhaps a link to someone who has done it already?

Another question I have is what foam to use exactly. I know that pourable foam is a usually a good bet for oddly shaped areas (which describes all of my locations for foam), but I like the idea of being able to mold and shape a block of foam and put it in place. That way, I could possibly remove it as one piece rather than scraping out tiny bits of foam clung to the hull.

[The Froon]

You will want to use closed cell foam - whichever product you decide to go with. A lot of manufactures in the early fiberglass days used open cell foams, and over time they became filled with water...

I have a friend that is stuffing the hollows of a Rhodes 19 with cut up portions of 'noodles' - you know, those pool toys that offer hours of fun. They are relatively inexpensive, but kind of time consuming having to cut into small pieces. The two part foams can cause some distortion if surrounding structures if not allowed to 'escape' as it expands. ...my 2 cents...

Brian

[earlylight]

How much reserve buoyancy are you trying to add? A cubic foot of closed cell foam will yield approximately 50 to 60 lbs of buoyancy so adding large amounts of buoyancy will require giving up considerable stowage space. As Brian noted, you need to allow for expansion when using pour in place foam. I have seen some hulls and closed compartments literally torn apart by expanding foam. Good luck !

[radicalcy]

The Victory 21 that I am currently warehousing, for a future project, used large styrofoam blocks trimmed to fit the hull profile. The entire aft area beneath the cockpit was packed tightly with these blocks. Approximate size of each block is 48" x 20" x 20"

[Hirilondë]

I have seen some hulls and closed compartments literally torn apart by expanding foam.

It certainly can do that well!

Are you trying to get a Bristol 27 to the point where it would float if completely swamped?

[Skipper Dan]

Have you thought about air bags? An old inner-tube will fill a space rather well. Also if you want to use the pink or blue insulation you can glue it up into big blocks and form it. or use a garbage bag and fill it in the cavity with the expandable foam. You fill in layers so you do not over fill. With air though you do not have to fill it until you need it.

Dan

[Quetzalsailor]

I also am curious as to how much reserve bouyancy you're thinking of. I rather doubt that anything shy of accomodating the entire boat's and content's displacement is worth doing. Anything less and she'll go down. The required volume is more (because the foam weighs something) than the volume of air below the waterline within the boat and it would be most convenient for continued operation of the boat if that volume of foam were installed completely from somewhere above the waterline and down.

While this is a pretty uncommon design feature in a keelboat intended for ordinary accomodation and service, this is exactly what is done in some racing classes. For example, Flying Dutchman built since about 1980 are almost universally double bottomed, but not foam filled (because the foam weighs something). The distinct advantage is that any water which arrives in the boat, either by spray or capsizing, is instantly drained out through the transom and centerboard slot. However, the class also requires that the boat continue to float with a certain amount of positive bouyancy even if holed. Thus, even wood boats like mine are required to carry flotation in the form of air bags or foam blocks (there is not enough volume of wood to overcome the weight of the rig with enough additional bouyancy). Fiberglass boats are typically foam or honeycomb core so that the weight of glass can be reduced and the sandwich is sufficiently enough lighter than water so that the positive bouyancy is provided.

Positive bouyancy can be provided by the previously-mentioned foams (but you do have to keep open cell products dry, and if it's concealed, you won't know if it's wet nor be able to dry it), air bags (think of the various sunken boat lifting bags you've seen advertisements for), or the vinyl air bags that used to be seen in dinghies, or bagged chunks of foam. I made up four stacks of quarter circles of 2" beadboard whose dimensions were such that they filled 4 cheap nylon camping utility bags, tucked and tied into the under-side-deck space in the old FD.

Here's a pic of an FD, as found and recently bought to be restored, with inflated airbags still in place. Clearly, airbags intended to float a keelboat would have to be more robust (and more pressurized) in order to stay inflated at deeper depths.

[avd155]

Are you trying to get a Bristol 27 to the point where it would float if completely swamped?

Great question, let me explain...


For the moment, I'm attaching photos that aren't incredibly illustrative, but I'll get some better images tonight. For now, I'll explain (in text) what my plan for making my Bristol 27 as safe as possible. Regarding flotation, I have separated my Bristol 27 into 3 logical "sections": stern to cockpit bulkhead, main cabin area, and forward area.

Stern to Cockpit Bulkhead (3 Watertight Areas) - This area is made up of the lazarette, 2 sea lockers and the area below the cockpit. The lazarette will be fully water-tight, as well as the two sea lockers on either side. They will each have drains built into their lowest points which will have a valve on them that I can use to drain the water tight areas when needed (the drain will run to a dedicated gray water or bilge pump, I haven't decided that quite yet, but soon). The area under the cockpit will be accessed with a hatch cut out of the cockpit sole and will not be watertight due to engine stuff (air vents, exhaust, etc. etc.).

The two sea lockers in this area are very deep. If I filled their lowest point with flotation foam (up to about level with the cockpit sole) which would give me (very roughly) 1.5 - 2 cu.ft. of foam in each locker.

Images: (Not at this time, soon though.)

Main Cabin Area (2 Permanent Watertight Areas, 1 Flexible Area) - This area is from the cockpit bulkhead forward to the first mast-step bulkheads. The head and hanging lockers areas will have a bulkhead that runs from the main salon bulkhead, to the mast-step bulkhead. For ease of use, let's call this coin this the "splitter" bulkhead. The two "splitter" bulkhead will be as high as possible, but most likely will end up being around 8 inches above the original waterline of the boat. I also plan to add a "flexible" way to split the area between the salon bulkheads using a slide-in board, creating an additional watertight area in the salon.

I will also be adding flotation foam below the head platform and obviously all around the icebox.

As for the main salon, due to storage and ventilation concerns, as well as the height of the settee sides in relation to the waterline, I won't be able to create many water tight areas in the main salon area where the settees, galley and nav-station will be, so there isn't much flotation here to speak of.

Images:

Looking forward at the main bulkheads separating the main cabin and forward area. Notice the un-epoxied area which serves as the opening to access the v-berth platform (high above the waterline).

Cockpit bulkhead looking viewed from mast-step bulkheads

Forward Area (3 Watertight Areas) - This area is from the mast step bulkheads forward to the bow. It contains 2 watertight compartments below the v-berth platform and the chain locker. The tops of the two below-v-berth lockers should be around 8 inches above the waterline. The volume of these two lockers also decreases as the bottom of the boat rises to form the bow of the boat.

I have calculated the largest of the two below v-berth lockers will hold at least 120 gallons of water before the water would spill over the top into other areas of the boat. This "large" locker will be further subdivided in half, that will serve to build out two sections, each of which will contain a water tank of a yet unknown volume (somewhere around 40 gallons each by my current calculations). I consider these tanks to be permanent flotation volumes since they are completely sealed and can be drained and used for flotation in a pinch.

The chain locker will be sealed from the rest of the boat and an opening to access the chain inside will be well above the waterline.

Also note, these lockers will also be drained by a valve-controlled PVC pipe that runs all the way to the bilge (Just like the Stern to Cockpit Bulkhead area, I need to decide whether to use a gray water tank or a dedicated bilge pump.).

Images: (Not at this time, soon though.)


Hopefully that all makes sense. The main goal is to make this boat as safe as possible and to avoid allowing the entire boat to get swamped unless it was really, really bad conditions. The flotation foam is just trying to offset any weight that I can. I had considered air bags, but the problem is you need a way to quickly inflate them, which, as I understand it, requires some sort of air system to really be used in an emergency.

I had been considering sharing my ideas with the forum for awhile, but it's hard to put it into words. I'd love to hear any and all opinions about my plans.

[Hirilondë]

Well, unless you can calculate that your plans make the boat buoyant even when fully swamped you may be totally wasting your time and effort for what may in fact be false security. You mention in you last post about water tight lockers. Do they really have hatches with gaskets and tightening dogs? You mention using drop boards to make an area watertight. I don't think that works. Whether your boat settles slowly to the bottom or drops like a rock after swamping doesn't matter much from a safety perspective. Slowing down the time from the incident to when the boat actually sinks has some merit, but is it worth all the effort, money and sacrifices it will cost?

Even if you can do this I would find it not worth the effort. I definitely could not live with the loss of storage space. If I were to sail in open ocean for extended periods of time I would invest in a really good self inflating life raft and all the gear to go with it. And if I were to sail in coastal areas, which is what I do, I would maintain good safety equipments as required by the Coast Guard and bring along a dinghy. This is in fact what I do.

I really am a safe person, but I don't see your goal as realistic. This of course is my opinion, and you have to act on your opinion.

[Skipper Dan]

I think looking first at what kind of hole would sink me (When and where). research and find out how many times this happens. How can I keep the boat afloat long enough to fix it. Maybe some nice Kevlar on the outside may be helpful. I thought most holes came from reefs? It should not take that long to motor to shore before sinking.

Dan

[avd155]

I guess I didn't really say one way or the other, but I am aware that making a Bristol 27 neutrally buoyant and still be a suitable cruiser is probably impossible.

My main goals for these design decisions are meant to isolate areas of the boat when holed or damaged in a collision. Since all the bulkhead "tops" are at least 8 inches above the waterline, the water would in these areas would be contained to one portion of the boat until I could get the damage under control. The "8 inches above waterline" is important, because this allows the boat to list a fair amount before any water would escape one area and migrate to another.

So I guess it comes to the fact that if I'm not trying to make the boat neutrally buoyant, then why add flotation foam at all? I'll have to think about that one...

[Hirilondë]

My main goals for these design decisions are meant to isolate areas of the boat when holed or damaged in a collision.

This is certainly an interesting concern. I wonder how many below or near the waterline holes can actually be controlled? I wonder if there is any data on what percentage of these type of damage occur, and what percentage have been successfully brought under control such that sailing or motoring to safety has been achieved. If you read the Aubrey/Maturin series you would get the impression that it is quite possible to get the damage under control. In the Hornblower series they fail to do so. If you find anything along this line for data avd155, or anyone else for that matter, I would be most interested in hearing about it

There are many things one can do to improve the chances of survival at sea (I imply the coast as well), but like any area of safety it is all risk management and you are addressing the odds of something happening and not the eventuality.

[Quetzalsailor]

Good references!

Recall that Patrick O'Brien lifted all the ship handling and the action right out of the RN archives. Forrester did not, so far as I remember.

An important detail not to be missed is that the RN had an ample, well-trained, and technically skilled workforce aboard. Tools and spares, too.

I think that very few recreational craft are lost to collision, and far fewer to collisions that one could hope to be prepared for. Not all that many are lost to groundings and again, far fewer to groundings that one could hope to be prepared for.

[Tony]

I recall a story from a cruising couple on a full-keeled 36-40ish foot boat that sailed over something in the gulf and got a crack in their hull that ran for a foot or two. If I recall correctly, they discovered it when their backup bilge-pump came on and water was over the floorboards. It was a tense night, but they were able to patch it with 5200 and scrap lumber they carried for such a contingency and make it into port in the middle of a mild storm with some fairly big waves. I believe they did have some hefty bilge pumps. I don't remember for sure who it was. It might have been the former editor of Sail magazine, they cruised for 10 years or so and eventually settled back in Canada to take care of family.

[Ceasar Choppy]

I remember that article too. I think they were on their way to Venezuela or somewhere in the southern Caribbean.