Do I really need flotation foam?
This is a question that comes up more than you would think. The simple answer is that if the boat is under 20' long, YES! All outboard powered boats under 20' long are required by federal law to have upright and level flotation. Sterndrive and inboard powered boats under 20' long are required to have basic flotation. It is also a requirement of the American Boat and Yacht Council, otherwise known as ABYC. ABYC standards are more complete than US Coast Guard regulations. If you are in the EU, I believe the CE rules are almost the same as ABYC. In Australia, I think you are only required to have basic flotation under 20 feet. If you are outside the USA, check with your local regulations as I can't be an expert on them all!
The ABYC publishes a book about the size of the phone book in a medium size city. In it they have standards for nearly every facet and system in a boat. While these are voluntary standards, nearly all quality builders follow them. In fact, when the Coast Guard wants to change the rules they sometimes get the ABYC to update theirs as it is easier than getting things through congress. Why would you follow these rules? If you are a professional builder and find yourself in a lawsuit, you better have followed the standards! If not, just try to settle for as little as possible as you'll likely lose. You should probably keep that in mind if you ever want to sell that boat you are building in your garage . . . or if you take any clumsy friends out with you.
I am a member of ABYC and try to follow all of the standards that pertain to each boat I design. This helps me ensure that the boats I design will be safe for you and your family. I don't consider this optional, it is mandatory to me! The standards are updated regularly and have been proven for many years to help produce a safer, higher quality boat. They work so well they are actually referred to in the boating safety laws of other countries.
In the plan sets for my designs under 20 feet I include a flotation foam drawing. This drawing shows where to place the foam in the boat and how much to include. Again, this is a federal requirement and really isn't up for debate. It is required whether your boat came from a production builder or if it came from a pile of lumber in your backyard. I very strongly suggest that you follow this drawing closely. It isn't just getting enough foam to float the boat, you have to distribute it properly about the boat so the boat will float in an upright position if swamped. The Osprey and Crystal designs don't have a lot of freeboard and their cockpits are not self bailing. I can not stress this enough, the foam in these boats is a critical safety feature!
This is so important that if you make major changes to the design while building, we should revisit the foam arrangement to make sure it still meets the rules. So if you have added a bunch of stuff and overbuilt "just a little", then we probably need to talk! Changing the weight or the distribution of the weights will effect the foam.
What if the boat is over 20 feet? We really don't care about you guys . . . just kidding! On boats over 20 feet flotation is not required. Most production boats have it though as it adds a touch more safety if the boat is sinking. It also makes the boat ride quieter. Did you ever see a boat that has foundered and it is floating upside down or with just its bow sticking out of the water? That is because the under deck spaces were filled with foam, but none was placed up high. Once the deck became awash it was more stable upside down than right side up. That is why smaller boats are required to have upright and level flotation. I don't particularly like foam on larger boats as it tends to trap water in inaccessible locations, although that's not as big an issue on fiberglass boats as it is on wooden boats, at least not for the first few years. If you choose to skip the foam, it is possible your state will refuse to issue you a hull number. The boat can't be registered until it passes inspection and gets a hull number. Just imagine yourself sawing the boat apart in order to add the foam!
So, do you need that foam? If I include a drawing for flotation foam and don't label it optional, then IT IS REQUIRED BY LAW! Sorry to shout, but a few of you haven't been listening!