FLOTATION

[Alan Peck]

I know the topic of flotation has been discussed numerous times. However, after reading "Gerts" comments in the Designs/Plans section, it reminds me of the importance of flotation.

First off, I am "by no means" an expert in boat construction. Heck, it has taken me three years to reach the point where I am finally ready to put the decking on my 15' runabout. Before, I do that it seems like this would be the ideal time to add some flotation.

My two cents worth:

Just because most small wood boats won't sink, doesn't mean that floatation is not needed. As Gert pointed out the "Shearwater" design didn't sink but it could not be bailed.

Especially in cold water, being stuck hanging on to your boat is potentially tragic.

My observation is that a great many builders (of small boats)do not add the flotation. I am not sure why, but maybe its because we all figure it will not happen to us.

As I mentioned above I know that this subject has been discussed before. But there does not seem to be much concensus of ideas. In fact, some of the ideas seem like they could be downright dangerous.

I have seen floation ideas ranging from ping pong balls, fun noodles, styrofoam, air bags and sealed compartments. Obviously every method has its pros and cons.

My own (again not expert) ideas are that styrofoam is the most readily available but is not acceptable if petroleum is on board. Ideas like ping pong balls are not very effective as they waste too much valuable space to match the effectiveness of solid foam. Sealed compartments can be a problem if they are damaged in the event that causes the boat to capsize.

So after much thought I am considering buying the two-part foams available from some marine supply houses. I think these are usually urethane, but I am not positive about that. I am not sure it is a good idea to pour these foams directly into voids in the boat as I think that might promote rot due to lack of ventilation. Therefore, I am thinking about casting my own foam blocks in a separate container and cutting them to fit various suitable spaces in the boat. The only thing I haven't figured out is how to secure the foam so it doesn't float away when it is most needed!

Sorry if I have rambled on here. But with all the expertise on this Forum, I think more discussion would be valuable. I know I would appreciate it.

Thanks everyone.

[whb]

Alan,

I too have been considering flotation for my as yet unbuilt boat. Sealed compartments would be a bad idea for me as the boat will spend a great deal of time on a trailer in a desert. I am sure that in time a sealed compartment would explode from the heat. I am leaning towards multiple closeable compartments with flotation containers (pop bottles) or removable foam blocking stored where convenient.

Howard

[Venchka]

Working on the premise that everything aboard a small boat must do double or triple duty...

Fenders. You need them anyway, right? One 8"x20" fender equals 35 pounds of flotation, more or less. Secure them under thwarts or in the ends.

Empty drink bottles: Stored in mesh bags and lashed out of the way. When out of the water the mesh bags are easily removed for drying the boat. They must have a second use. Oh, right, for emergency water storage on a desert island?

Ice chest. Required here in the Swamp for cool drinks. Lots of flotation. Tied down securly of course.

Large zip-lock bags. There are really large zip-lock bags on the market now. Spare clothes, anything needing waterproof storage, etc. goes in the zip-lock bags and the zip-lock bags go in sturdy protective bags. Lash the bags below thwart level if possible but lash them well.

I'm sure the list goes on.

[On Vacation]

If its blocks, use the hook and latch system, simular to the velcro, but much tougher. Make sure you have a nice flat area for one side to stick to the foam block. BEWARE: This two part is expensive. Order it online, in bulk. Or find it in at least the gallon kits.

This stuff will also set off quickly on you. Mix small quanities and be ready to stir like crazy and pour. The more you stir, the better the mix and flotation for the amount of liquid. Be carefull of the hot pot. You will only have around thirty seconds of working time for the mixing. It will turn a dark brown upon stirring and then back yellow. By then you had better be ready to get rid of it, espcecially in the hot weather.

It will also stick to your skin forever, so use long paddles and gloves. A drill motor with a paint mixer on the end works great for larger mixes. In an enclosed area, it will give off a type of cynide gas.

[imported_Steven Bauer]

For the Oughtred Elf I'm building (very similar to Gert's boat) Iain recommends the kind of flotation bags that optimist sailors use. For my John Gardner skiff I'll use empty milk jugs under the stern seats and some sort of closed cell foam up in the bow.

Steven

[Venchka]

Originally posted by Oyster:
BEWARE: This two part is expensive...This stuff will also set off quickly on you...Mix small quanities and be ready to stir like crazy and pour. Be carefull of the hot pot...By then you had better be ready to get rid of it, espcecially in the hot weather.

It will also stick to your skin forever, so use long paddles and gloves...In an enclosed area, it will give off a type of cynide gas.

YUCK! Bundles of neon swim noodles are looking better and better.

[Bob Cleek]

Here you guys go reinventing the wheel again! LOL

Don't mess with that damn "mix and pour" foam. It's nasty stuff. I have a little FJ that somebody filled the bow with it. It's damn near impossible to remove. I have to get to the end of the bow to install a ring to use for hauling it on the trailer, but I've all but given up on it. When there's nothing else to do (that's rarely), I go at it with my grinder with a wire wheel on it and cover myself with foam dust, while making little real progress. I saw one guy blow his boat apart trying to fill an "air tight compartment" with it. It just kept expanding and expanding and expanding until, POW!, she split her seams! The problem with rot is so true as well.

If you want positive bouyancey, buy foam block stock at your local foam store, or even use some old dock floats. (The outside gets crappy, but cut it off and the inside will be like new.) Consider stuffing an inner tube in a compartment, or under a thwart and inflating it to "stick" in place. Even consider rigging an old fire extinguisher to an inner tube so you can have "instant floatation" if you need it. Packing peanuts, anything, is better than the cast in place stuff.

HOWEVER, the concern about floatation is really more a fear borne of inexperience than anything else, IMHO. If you are going to capsize a boat on a regular basis, you need more than floatation, you need to learn how to sail it. Not to say that small boats aren't prone to turning turtle, but those that are (where stability has been intentionally sacrificed for the sake of speed) should not be sailed in unprotected waters where a "crash boat" or other helpful rescue isn't readily available. (Or where you can stand up and bail her, the water's so shallow!) Certainly, every mariner should consider resourcefulness and self-reliance as primary character traits, but there's a limit.

If you are sailing a boat that you know is liable to dump you in the drink, you should not be sailing it without wearing a PFD. If the waters are seriously cold, you should not be sailing it without a wetsuit. (Here on SF Bay, on a GOOD day, you've generally got somewhere less than an hour's survival time before hypothermia gets ya.)

Bottom line, every boat should be suitable for the use intended. When they are used beyond their intended limits, no amount of floatation is going to make much difference.

[ 08-21-2003, 09:12 PM: Message edited by: Bob Cleek ]

[On Vacation]

There are advantages to using it, if you wish to fill voids, and for the most part, it is marketed as being waterproof, as waterproof as foam can be. The last time I bought it, in the 2 quart kit, it ran around 30 dollars. One premature kick, can cost you some change. The worse part is when it gets on your skin. Well evening to all and to all a good night.

[abe]

Alan, a very appropriate topic for you to raise again.

I have a couple questions for you or anyone faced with this issue.

I am going through the US Coast Guard basic requirements in the COMDTPUBP16761.3B or "Safety Standards for Backyard Boatbuilders" publication and I am directed to add flotation among other requirements to a 16 foot rowboat.

Before I make any decisions on what to use for flotation material, I thought it would be wise to determine just how much is required.

So far it has been determined that a cubic foot of enclosed air(in a bow chamber) will provide 62.4 lbs of buoyancy, the boat is 110 lbs, the conversion factor for white and WR cedar is about -1.80 and therefore the flotation material required is minus 3.17 cubic feet.

Formula is: ((Weight of Hull times Material Conversion factor) plus (weight of deck)) divided by Buoyancy of Flotation material.

Now if I add 400 lbs of people and gear, I will need .15(400)=60/62.4 or rounded up to 1 lb flotation, then added to the -3.17 lbs above the boat will still not need any flotation? The .15 factor is a given, does anyone know where this comes from?

I was planning to add a bow flotation compartment to the cedar strip boat, but now it would appear that the regs don't support that.

abe

[Stu Fyfe]

When Phil Bolger designed my Redwing, he called for flotation in the bow behind the 1st bulkhead and under the starboard and port bench seats in the cockpit. We have chunks of styrofoam that are held in place with fishnet. They've held up for 21 years now. The nets and the loose chunks seem to allow some circulation and mildew hasn't been a problem. Hopefully I'll never have to find out if they work, although Phil once asked me, matter of factly, "Have you capsized her yet?"!

[NormMessinger]

What Cleek said about pour in place foam!

If you are casting your own foam blocks, cut out a step, and start with foam blocks

[warthog5]

Well here's the fix for the foward compartment.
I installed a piece of 4in PVC so that you could still get to the bow eye. There is some throught to my madness.
As to the 2part foam. Yes I use it and I use the 4lb density, not the 2lb like most boat manufactures. It's more dense. Sure it only goes half as far as the 2lb density.
As to not using it and using some flim-flam other pop bottles or ping pong balls.
How Much is YOUR life worth?

[Alan Peck]

Thanks everyone for the replys so far. I really appreciate the input.

I would prefer pre-made blocks, but the only kind I can find locally seem to be styrofoam which I am trying to avoid since it melts upon contact with petroleum and is also pretty water absorbant.

Does anyone know of a source of pre-made urethane blocks?

[warthog5]

Hey It work's Mike. Yea!
Follow Osyter's direction's on this stuff.
The max you can stirr it is 45sec on a fast count.
You better be pouring it. No time to climb a ladder to get to the spot.
I get mine from http://www.fgci.com

[warthog5]

In the aft section on my skiff I made blocks out of 1 1/2in styrofoam. I glued them together with some epoxy. I then wraped 4oz cloth around it with epoxy and stuck them in the hole. I then poured the small void's with 2 part pourable to lock it all in.
It's labor intensive and I don't think there was any money really saved.

[helvit]

How about "blueboard" + styrofoam adhesive and maybe a batten or two? Cheap at any yard, or Home Depot, many thicknesses, closed cell, good with moisture, very light and floaty, easy to handle.... 1200 lbs of flotation under the sole and around the ceiling of an Ocean Pointer.

----------------------------------
Manufacturer: Dow Chemical
Address: 2030 Dow Center, Midland, MI 48674
Phone: (800) 447-4369
Web Site: www.dow.com

Product Name: Styrofoam (expanded), Styrofoam Square Edge (extruded)
Insulation Classification: Foam Insulation
Thickness As Tested: 1.00"
Claimed "R" Value: N/A (expanded), 5.0 (extruded)
Actual "R" Value (at product thickness): 3.84 (expanded), 4.92 (extruded)
Equivalent "R" Value (per inch): 3.84 (expanded), 4.92 (extruded)



Product Overview
Dow Chemical's "Styrofoam" brand name encompasses a wide range of polystyrene-based insulation products. Included in our testing were two versions, the common white "expanded" product and the "extruded" Styrofoam Square Edge (see photo).

Styrofoam (expanded)- This is the product most people think of when they hear "Styrofoam". It is white in color and comprised of thousands of individual "beads" which are pressed together. The most common use is as a cushioning material in shipping and packaging. Although it is not intended for use as an insulation, it frequently is. Most people have seen cheap coolers and ice chests made from it. As an insulation, expanded Styrofoam has many qualities which count against it. At R 3.84 per inch, the product is simply not a very good insulator. Secondly, it is very hygroscopicity (absorbs and holds moisture). This tendency to get, and stay wet, makes it something to definitely avoid when looking at ice box insulation.

Styrofoam Square Edge (extruded) - This product is often called "blueboard" due to its light blue color. In spite of its relatively modest "R" value (4.92 per inch), Styrofoam SM is our overwhelming recommendation for foam ice box insulation in marine applications. Unlike its expanded cousin (above)and virtually all other foam insulation, Styrofoam "Square Edge" is completely impervious to moisture. This is a huge plus. While many other foams start out as better insulators, they inevitably suffer significant decline as they absorb moisture from the surrounding air. This is not the case with Styrofoam SP. Another benefit of its hydrophobic nature is that no "air gap" is required when installing it. This means that more insulation can be packed into a smaller space. If is available in many thicknesses and two sheet sizes.

Test Conclusion
As the fifth largest chemical company in the world, Dow does not need to oversell their products or exaggerate their qualities. Unfortunately, misapplication of expanded Styrofoam has led many people to think of the brand as offering poor insulation value and high moisture absorption. As previously stated, expanded polystyrene is not a suitable insulation for moist environment. However, the extruded version, Styrofoam Square Edge, is another story entirely and we recommend it highly whenever a standard insulation foam is required.
http://www.glacierbay.com/dowtest.htm

[George Roberts]

abe ---

I think your formula is incorrect.

.15*400 = 60 pounds

60/62 = 1 cuft air as floation material.

I don't know where the .15 comes from. I think the booklet explains it.

The floatation formula may apply to boats under 20' and canoes, kayaks and ... are exempt.

Flotation is always a good idea. There may be conditions beyond your control (hitting flotsom) that may require ...

[Wayne Jeffers]

Andy,

Regarding your question about the 0.15 factor for the people -- I suspect that is a result of experience as to the minimum amount necessary to keep the boat above water sufficiently to give the passengers something to hang on to while they are largely immersed in water, either inside the swamped boat or in the water beside the boat. It's not figuring enough flotation to keep them out of the water, just enough to keep them floating securely. That's fine if hypothermia is not an issue.

At your latitude and even at mine, I think it important to include enough foam so that the passengers can get up out of the cold water in the springtime. I would factor 100% for the passengers, or close to that number, if you'll be using the boat when the water is cold enough to be a risk of hypothermia.

Alan,

If you decide to use blocks of foam or similar and it's not in a closed compartment, you can cover them with fabric (canvas, etc.) or put them in large duffel bags, before strapping them under the thwarts, or wherever. That way they don't look so ugly.

Wayne

[imported_Snatchblock]

Eastern Burlap out of Norfolk is a good souce for pour type foam.

[ion barnes]

The .15 factor I believe is because when you are in the water, you do not weigh your dry weight. Thats why the PFD you wear is relativly small.

The blue foam is the best thing on the market. It has surpassed everything else. If you have open compartments (that breathe) you can use white pearl foam board, also available from Home Depot, but it will crumble if banged about. Just depends on the situation. I have some in a little punt, under the seats and it has not given me any trouble for years.

Instead of the mixed foam, to fill inbetween the cracks, how about the spray foam in an areosol can? You dont get much, but there is no mixing and you wont need much.

Going back to the blue foam, I epoxied some with West epoxy and doorskin ply to make a curved panel 3' long and 4" wide. It has about a 3.5" arc. I can stand on it (not jump on to it) and it supports my weight of 230 lb. No kidding, The foam is 1.5" thick.

Regards to flotation lockers, they should be distributed around the boat so that it has a chance to float horizontally with people on board. Our Canadian regs indicate one person per seat so if the boat is 10' long with bow, mid and stern thwarts, - 3 people. If you have a motor hung on the transom, you have to add for that. And you do not want the flotation buried under the floorboards either, because the the boat could turn turtle (upside down) if swamped, and would be hard to keep afloat rightside up in a swamped condition. Ion

[DickB]

Cleeg says it is our inexperience that brings us to flotation. I'm still inexperienced, as the boat is still on land. Yet, some years back when I too brought this subject up (then wondering about kids aboard and how to bail out a 20-footer) I learned #1 that rot isn't to be avoided if you're gluing to the hull, and #2 there are other options that are workable. I'll be buying a car innertube for the bow and one for the stern--They'll get jammed into spaces and pumped up a bit before going out, and they'll be emptied upon return. Seems to be a very inexpensive and kind-to-boat solution.

[Wayne Jeffers]

Originally posted by ionbarnes:
. . . Instead of the mixed foam, to fill inbetween the cracks, how about the spray foam in an areosol can? You dont get much, but there is no mixing and you wont need much.
. . .

Ion,

The foam in the aerosol cans is an extremely expensive substitute for block foam. The contents of a can won't fill much more than the volume of two cans when expanded. Try it sometime. It also crumbles upon exposure to UV light (sunlight.) A can of foam is better thought of as a substitute for a tube of caulking compound.

Wayne

[On Vacation]

I am always amazed at the amount of knowledge of many folks, but speak with the lack of knowledge on issues.

There is a time and place for everything in boat construction. No two boats are alike. Most boats with foam in the hull areas, are or should be glassed in the compartments. Most of the time, proper glassing of the hull first seals off the hull wood, therefore sealing out the potential of rot in the hull.

In foaming of these hulls, success long term, is generated by partitioning off sections with tabbed in grids of the hull encasement, as seen in these pictures. This will do two fold things, One it gives strength to the bottom, and supports for a lighter deck system. This will also stop any water from getting to all of the sections. But thats another story. This is a boat that had twelve inches of water in it, stored for around twleve months months. The water did get into the deck through end grain area of the console area, but did nothing to create disaster to the hull. Proper work, minimizes work down the road. THIS WAS NOT THE FAULT OF FOAMING IN, AND WOULD HAVE BEEN WORSE IN A TRADITONAL PLANK HULL.

If you will coat the glass or even coat the hull,[notice the brown color change in the bare spots from coating it with a gel coat] coated with multiple coats of resin, then you coat it with either a primer or gelcoat it, down the road the foam will come out in bulk sections, with the release of it from the hull. The partitions allowed for partial work, as seen in the second shot. This can be done in small craft seating compartments. Also you can notice the templete, that was discussed in another thread in MIsc. Boat related, that discussed making patterns to fit a certain shape.

Also, if you will look closely, blue board is used in cut sections and then tabbed in with the foam. It did not go bad in completely closed sections, either. This is a great way to save big bucks, for use in a completely closed section, only. If you iwsh to make blocks, use a one gallon milk or water jugs, or one gallon paint buckets to pour foam into it. Then it wil break out, or you can it from around it. These will need to be waxed a little for a better release. Now off to the creek.




[ 08-22-2003, 08:49 AM: Message edited by: Oyster ]

[NormMessinger]

The pour in place stuff is excellent stuff to glue blocks of foam together, expecially if you are going to be cutting and shaping them later. No hard glue line.

[Alan D. Hyde]

The cheap Type III life jackets go for $3.95 or $4.95. The cheap throwable cushions go for a little bit more. The X-large adult jackets provide even more floatation.

I've usually got a dozen life jackets in fore and aft lockers, and perhaps 8 or 10 of the cushions.

There's some floatation for you.

Alan

[ion barnes]

Wayne,I was not thinking of aerosol foarm for an entire compartment!!! Just to cement the indiviual blue foam blocks and fill small voids.

I can vouch for the styro peanuts in a garbage bag, but you have to avoid the imatation peanuts made from potatoe starch. They melt when exposed to water. Really, all you want or need is something that will hold air or prevent water from flooding the compartment.

[merc412]

A quotation from a one design class, "Older hulls without floatation may fill with water and sink if sailed in a careless manner." I plan to put 2" closed cell all round under the deck between frames and add a bulkhead fwd of the mast and aft of the rudder post to keep the attached 600lb keel from takin it to the bottom. I'll be sailing bays and deep lakes and don't want to loose the boat if I screw up or a freak wind comes up.

[ion barnes]

Oh and about the UV resistance of aerosol foam? I have some sticking out of the gap around my workshop door, and though it has changed colour from cream to orange on the surface, it is still there, not crumbling, Looks like a fungus you find on a tree. Its been exposed to the weather for about 5 years now. Its also fire resistant too.

[JimD]

I recall reading an article in one of the UK magazines, maybe Practical Boat Owner or ClassicBoat, can't remember, but the article was for the most part against the two part pour in place systems, one reason being that the stuff can break down over time and end up acting more like a sponge that soaks up water than closed cells that keep water out. Never used the stuff myself though.

[abe]

The pdf file of the Backyard Builders Reqs is below for your reading pleasure. My flotation formulas are on pages 15 to about 20.

http://www.uscg.mil/d8/mso/louisvill...bp16761_3b.pdf

abe

[Venchka]

If it's all the same to some of ya'll, I'll stick to safe, non-toxic, sometimes free stuff I can remove for ventilation, refinishing, etc.

Thanks to someone above for adding that extra PFD's and cushions, properly secured, provide a lot of flotation.

A point missed by all of us, I think, is a plug for the centerboard/daggerboard case. Flotation alone may not allow you to bail/pump out the water if the top of the case is wide open.

[On Vacation]

FWIW, The type III flotation does not weather that well. Exposure to the elements, will create a damp bundle of water logged flotation.

[ahp]

You might think about watertight compartments with a removable hatch. This could be a piece of plywood with a gasket around the edge and a piece of shock cord to hold it tight in place.

You must promise yourself put the hatch in place before sailing and to remove the hatch when not sailing, every time! I have looked into unventilated compartments in wood boats, and the smell of mold would about knock you over.

[On Vacation]

Unventilated compartments are not foamed and sealed compartments. Hollow and unventilated compartments are a greenhouse, many times. That is where you get the smell and rot. Ever heard of the foamed sandwiched hull named Boston Whaler? Pretty successful operation for foam applications. Well, unless stress cracks or improper caulking of hardware and equipment create water intrusion, you will get a lot of years from them. There are times, ways, and places for everything.