C17 in New Zealand.

[OneWayTraffic]

Definitely a blue/green foam. Most of the pour went ok, I did have one small area where it's gotten too much air in it and I can push holes in it. I'll cut that back and seal over it, or more foam.

I don't want any water traps in there at all when the sole goes down. Any gaps in the foam will either be filled with more foam, putty, or a hole drilled to allow drainage. Lowest parts of every compartment have either a limber or an inspection port.

NZ is known for it's wind, right in the middle of the roaring forties. Southern hemisphere doesn't have a lot of land in it, so the wind picks up speed over the ocean. NW gales gusting to over 100km/h in exposed places are fairly common. But not many tornados or hurricanes, so I'm not complaining.

[TomW1]

Nice job on the foam as I recall from my plans that is where Jacques designated it go to make the C17 unsinkable. Love the color.

Tom

[OneWayTraffic]

Nice job on the foam as I recall from my plans that is where Jacques designated it go to make the C17 unsinkable. Love the color.

Tom

I have some left to go under the gunwales and along the sides above the waterline.

[TomW1]

Nice job on the foam as I recall from my plans that is where Jacques designated it go to make the C17 unsinkable. Love the color.

Tom

I have some left to go under the gunwales and along the sides above the waterline.

Good move that will keep her upright also.

Tom

[OneWayTraffic]

Someone on another forum asked me a question about the foam. I replied in some detail and thought it might be worth a cross post here.

I put a lot of thought into this, as I really don't want to be ripping off the sole and digging out sodden foam ten years down the road, nor do I want to end up a statistic.

Standard 2 part polyurethane foam, that I bought from an industrial supplier in ChCh. The blocks are high density foam 100kg/cubic metre and the pour foam was partly the same high density and mostly a standard 33kg foam. All supposed to be closed cell.

I am aware of the potential for it to absorb water. Apparently this is mainly due to not being mixed perfectly with a 1:1 ratio, at the right temp and humidity, or a bit of water gets in through where the denser skin has been cut and then through hydraulic action, slamming of the boat, or freeze thaw cyclesmigrates its way through over years.

Otherwise it is pretty waterproof, especially the polyurethane block foam made in a factory at optimum conditions which is therefore of higher quality.

Thinking about all this the key in my mind is to a) do a good job of laying the foam b) keep water from sitting in there and c) allow a method of checking and removing water from compartments. The foam is there to allow me to sleep better at night without that nagging what if...

The middle compartment is by far the biggest. I glued two layers of high density block foam down the middle of it as a dam. This is quite strong; a small square will support my weight. Then high density 2 part pour on the inside of them to help secure and support.

Then multiple pours of the 2 part standard density foam between that and the stringers. That explains all the little muffin tops. One or two places where the 2 part didn't set off correctly, which I will mostly dig out and replace. Once I've cut it level I'll go about plugging and sealing any little places where water can gather. I'll keep the muffin tops for later if they are good.

Outside compartments have the block foam just glued to the floor with some high density pour foam on the upper side between foam and chine. The high density takes longer to go off; I underestimated how far it would migrate. It does do a good job of plugging holes and water traps.

Each side has two separate compartments, the middle just one big one. In either case the lowest part of every single compartment is left bare and uncovered. Should water ever get inside in any significant amount it will end up there and I will know about it.

When the sole goes on it will be epoxy coated and glassed both sides and glassed in all around the perimeter as per the plans. There will be five inspection ports. Circular screw in type. To avoid leaks through these they will not be in places where water can gather. Two at the back will be partly up the vertical motorwell bulkhead, the other three will all be on the sole, but either inside a hatched compartment or at least under a shelf and on a raised surface. I'll seal them as well as I can, but no water should ever be sitting up against the inspection ports. There will be some small breather holes but not where water should get in, and if it does, I will know.

The cockpit will be designed so that if and when rainwater gets in, it will run to the rear and either out the back or out two plugholes I'm putting in the sides. No nooks and crannies for it to accumulate. Benches will have either a sloped uphill side or gaps under to let water by, either salt, rain or when I hose it out.

The boat will be stored outside but under a cover. I may get one custom made eventually. Thinking about a carport as well to keep UV and the worst of the rain off.

If water ever gets into that foam I will be surprised.

There will be foam under the gunwales as well for a measure of upright buoyancy. Not yet 100% sure what exactly it will look like.

As you can see I didn't just come up with this plan over a couple of beers.

[BarraMan]

I did something similar with my boat - a combination of Microlen high density foam blocks and 2 pack polyurethane poured foam. The way my boat is built, its almost a double-hulled foam sandwich!

I know my boat will not sink - I've done the maths. Theoretically it will float upright if swamped - but I haven't tested that.

Where I go, the boat is our life support system. Its very remote and hours from any help. Lose your boat and you are in a world of hurt, in a very inhospitable environment.

Here's some specs on Micolen.

Microlen® Marine Buoyancy Foam
A New Cross-Linked Buoyancy Foam Developed for Positive Buoyancy in Small Vessels. Microlen® closed cell foam is cross-linked, a chemical irreversible process that makes the foam inert to solvents and gasoline. Microlen® will not cause any electro chemical reaction when coming into contact with wood, steel, aluminium alloy, glass fibre laminates, paints, varnishes or adhesives. Microlen® has high impact resistance and will not powder or crumble, making it suitable for installation without the need to seal in an outer skin. The foam is easily cut with a standard bandsaw. Microlen® will only absorb fractional amounts of water because of its closed cell structure.

[OneWayTraffic]

I did something similar with my boat - a combination of Microlen high density foam blocks and 2 pack polyurethane poured foam. The way my boat is built, its almost a double-hulled foam sandwich!

I know my boat will not sink - I've done the maths. Theoretically it will float upright if swamped - but I haven't tested that.

Where I go, the boat is our life support system. Its very remote and hours from any help. Lose your boat and you are in a world of hurt, in a very inhospitable environment.

Here's some specs on Micolen.

Microlen® Marine Buoyancy Foam
A New Cross-Linked Buoyancy Foam Developed for Positive Buoyancy in Small Vessels. Microlen® closed cell foam is cross-linked, a chemical irreversible process that makes the foam inert to solvents and gasoline. Microlen® will not cause any electro chemical reaction when coming into contact with wood, steel, aluminium alloy, glass fibre laminates, paints, varnishes or adhesives. Microlen® has high impact resistance and will not powder or crumble, making it suitable for installation without the need to seal in an outer skin. The foam is easily cut with a standard bandsaw. Microlen® will only absorb fractional amounts of water because of its closed cell structure.

Looks ideal. I remember looking around for a supplier of that earlier on. Couldn't find one in NZ, so I went another route.

[Dougster]

"Double-hulled foam sandwich" I think that way of my LB22. It's almost a huge surfboard with sides. I would be surprised too if any water has gotten in there.

Dougster

[OneWayTraffic]

Well I went to go buy the remaining plywood I needed. Went with 9mm rather than 12mm on the sole, as I have enough biaxial to glass both sides. Should even be cheaper, factoring in the already bought glass and cost differential between 12mm and 9mm plywood.

Speaking of cost differential the plywood was over 1.5 times the price Jan 2020. If I'd bought all I needed back then I'd would have saved hundreds of $$. COVID mucking up the freight companies.

There was a silver lining though. I ordered 2 sheets of 6mm (cabin top and forward deck) and 5 of 9mm (sole, berths and seating.) They said they'd give me a coversheet to keep the ply dry on my trailer, and they did. A 4mm sheet of Meranti BS1088 marine!

I'm now thinking about leaving the C17 open cabin and making the CC14 with one sheet of 6mm and 4mm ply for the sides.

[OneWayTraffic]

Sole dry fit. I took my time painstakingly measuring from the boat and then cutting slightly oversized with repeated trimming and grinding and was rewarded with an almost perfect fit with an even gap most everywhere.

I managed to save a sheet of plywood over the nesting diagram. This does mean that one of the butt blocks is quite close to a frame. There's just enough overlap though I'll reinforce the join on that side. I'd forgotten about rebating the foam there for the butt block, so pulled out Mr Grinder with 36 grit. 10 seconds later I was ankle deep in foam dust. It does take up a lot less space as dust in the trash compared to the foam.

The front panel halves will be taped both sides and a butt block where the inspection port will be. This will be on top of the sole to keep it proud of the deck, but under the berth to save toes.