Phantom Phoam

It's official, there is only one more step before the boat will be technically legal by the USCG regulations. That sounds huge, and it feels great but there is still a TON of work to do before the first shake down cruise.

To get to this point Dad and Captain Dave came out again last Monday to finish off the stringers and prep the glass on the deck pieces.

This is a shot of the starboard stringer glassed in and ready to go

After we got the stringers in and the first layer of glass on the middle deck piece we ran out of resin. Looks like I'll need to head down and get another 5 gallon barrel. Not too great for the old pocket book but we're on a roll and being finished next month will feel sooooooooo good.

When the stringers and glass were finished the next step was the floatation foam. The Coast Guard requires all boats under 21' to have enough floatation material to create neutral buoyancy when swamped. The forums have multiple ideas and solutions for this from the two-part polyurethane foam to multi-colored pool noodles. The main characteristics that all the solution share is high buoyancy, light weight, and closed cell. I decided a while ago that since the old foam had so much rigidity in the stern I wanted to stick with the firm polyurethane expanding foam. But this stuff is expensive. Most local retailers sell it for $75-$100 per cubic foot. So how many cubic feet do I need you ask yourself? Well through the magic of math we can figure that out. The formula I found is for salt water. But fret not! There's a coefficient to compensate for the difference in fresh water:


Hull weight: 750lbs
Specific weight of fiberglass in salt water: 1.5
Positive buoyancy: 500
Negative buoyancy: 250
Engine weight: 250lbs
Specific weight of cast iron in salt water: 7
Positive buoyancy: 35.71
Negative buoyancy: 214.29

Total negative buoyancy: 464.29
Fresh Water coefficient: 1.025
Fresh water buoyancy: 475.89

Flotation factor of foam 60lb/cu foot

Total cubic feet of foam needed: 7.93

So at $100/cubic foot that's $800 worth of foam! Fortunately I found an online retailer that sells it for a much more reasonable price.

This is my 16lb kit of two part foam from US Composites out of Florida.
This stuff is ridiculously tricky. You mix equal parts of A and B for 20 seconds then there is only 45 second to pour it before it begins to expand. Then there is the issue of ambient temperature. For optimal expansion 80 degrees is required. Since this has been the worst spring in the history of humanity, our neighborhood hasn't gone above 70 on the best day. And yesterday was not the best day, it was only 65 in the sun. To overcome the heat issue I used my wife Rachele's hair dryer to blow hot air down the length of the boat, it actually worked quite well.

It took ten small batches to get it all in but here it is all foamed up:

You can see the blow dryer in the right side of this picture

Next we need to get the boat off the trailer to patch and paint the underside. I want to get this done before we lay in the deck, it'll be much lighter this way.

So big thanks to Dad and Captain Dave. Another couple weeks and she'll be ready to sail!