See full version: Richardson Docks
Our Large Pontoon Floats (22′ x 24″ x 16ft will support 130 pounds per lineal foot. Considering an 8ft x 16ft dock has two 16ft floats it will support 2 x 16ft x 135lbs = 4,320lbs. The actual dock will weight by itself 11.5 pounds per square foot. Using the same example 8ft x 16ft x 11.5lbs = 1472 pounds. So the net weight an 8ft x16ft dock will support is 4,320 – 1,472 = 2,848 lbs. [links]
Our pontoon floats run either the entire length or width of your dock or raft. Without any gaps, flotation is consistent giving more stability, strength and buoyancy. A single sixteen foot (12″x 2′ x 16′) float has 32 cubic feet of foam medium. Our larger float (22″ x 2′ x 16′) has 58.7 cubic feet of foam medium. more
It is always important to be comparing “apples to apples” when doing a dock flotation calculation.
Regular dock floats they will support 65 pounds per lineal foot. Considering an 8ft x 16ft dock has three 16ft floats it will support 3 x 16ft x 65lbs = 3,120lbs. The actual dock will weight by itself 10.5 pounds per square foot. Using the same example 8ft x 16ft x 10.5lbs = 1344 pounds. So the net weight an 8ft x16ft dock will support is 3,120 – 1344 = 1776 lbs.
An air filled device and a foam filled device have just about the same flotation characteristics sitting dry. Add moisture in the form of condensation or a leak, and everything changes. Water displaces air and if enough gets in it will not support itself. In other words it sinks!
Using foam within the flotation device displaces the water up until the point of saturation. In other words it becomes water-logged.
So – then it becomes an absorption issue of the foam. [links]
Have you ever wondered what the pounds in bouyancy really mean? Boatsafe.com put together a quick and easy explanation which can be helpful.
"In your course you say that different PFDs have different pounds of buoyancy. What does that mean?"
How can this PFD with 22 pounds of buoyancy hold up a two hundred pound person in the water? more
EMERGENCY FLOATATION
I am a bit of a nutball when it comes to emergency floatation. The coast guard requires all power boats to have enough floatation to "keep the hull floating and give the passengers something to hold onto while waiting for rescue", but interestingly they do not require floatation for sailboats. It is popular among blue water cruisers to have full floatation, so that if the boat is holed and fills up with water, it can still be sailed. I agree with the blue water guys, because there are plenty of logs, shipping containers, oil drums etc that are out floating free that could easily crack open my hull. In 2005, one report stated that 450 shipping containers were lost that year alone - and they can stay afloat for years, just below the surface. With a little time, most holes can be jury rig repaired on the water - which will allow you to bail and continue your trip.
Just to make sure it is closed cell, and will resist water, I did some experimenting. I made a couple of little globs, some were complete globs, and others were gobs that I cut in half. I then took them and submerged them in a small plastic container filled with water. Pushing the lid on made water squirt out the lip, so I knew the foam pieces were submerged under water. Came back the next day, opened the lid and guess what? The pour foam had sucked up a bunch of water. Each little piece was just like a sponge, I was so angry . Well, time to move onto plan B, so I did the same experiment with a couple of other types of foam. I had some sheet construction foam and that held up to the water, was still fine after a month. Popcorn packing chips were another good one.
The next step is to figure a way to encapsulate them packing chips, because if I holed the boat, I didn't want my floatation material to float away. So I got some cheap nylon fabric and started sewing pillows of chips. more
Two-part expanding polyurethane marine flotation foam for permanent flotation, thermal insulating, and soundproofing. Its easy-flowing formula conforms quickly to fill the cavity it’s poured into. Available in 2 lb. or 6 lb. density, in 2-Quart and 2-Gallon kits. more
TotalBoat Marine Flotation Foam is great for filling voids, especially under decks. It’s thermal and sound-proofing abilities make it ideal for a number of other insulation and flotation applications. 94% closed-cell foam structure lets it maintains buoyant pressure even after prolonged exposure to water.
This 2 part pour-in-place expanding polyurethane boat foam reaches full expansion in about five minutes, and can be poured in multiple layers with excellent bonding between layers. The cured foam hardens into shape with minimal shrinkage, is not affected by gas or oil, and resists mold and mildew. Once fully cured, foam can be laminated over with polyester, epoxy, or vinyl ester resins. here