Thank you to everyone who has joined the blog recently. Many of you have made comments about your concern for the ballast and the horizontal stability of the tsunamiball. Here is what I am looking at:
The round shape of the tsunamiball makes for a very strong hull shape, but a lousy shape for horizontal stability. I knew this was an issue very early on. In fact, this issue is why the boat is called the tsunamiball, but the shape is decidedly not a ball. I sacrificed the strength of the sphere to buy more fore-aft stability and put more oxygen in the boat, which I plan on being airtight.
So now… horizontal stability.
After all of the plywood layers are added I’ll weigh what I have and start the math to get the weight ratio above and below the waterline right. I expect what I will need is a good sized steel keel, which will get bolted through the outer hull and into the frame of the boat. The idea is to put as much of the ballast requirement into the keel, as far below the waterline as I can.
I’m thinking the keel could be similar to a folkboat, which is a traditional wooden sailing boat that has a very heavy steel keel (1ton+)) to keep her upright in rough conditions and full sail.
Another option would be to try a less traditional approach and do a double keel, which would have the added benefit of keeping the boat upright and stable for the majority of its time on land? The thickness and height of the keel will depend on the weight for ballast that I need to get the right waterline.
I was also wondering if there was a benefit to closing off the double keel, so it was more of a box? Would this give me a lot more stability as the water trapped in the box would be like an anchor, keeping the boat from much horizontal movement at all? If you know the answer, let me know. :)
I expect the single keel is simpler to maintain, better for the centerline architecture of the vessel, and makes navigation a lot more responsive and predictable.
I would love comments.