Tuesday, 8 March 2016

When Is A FLOOR not a FLOOR?

A floor is what you call the surface you walk on in your home, right? Beneath a wooden floor the beams, joists, or whatever you call them in your neck-of-the-woods, are those long pieces of wood upon which floor boards are fixed, right?

Not so in boat-building, here the 'joists' are called the floors. The planks on top of them upon which we will walk are called the soles.

As Seagull's floors have to fit onto the curved bottom of the inside of the boat, they have to be tailor-made to suit the exact curvature of the one location to which they will be fixed. 

If I waited until the boat was fully planked before I made the floors  then I would have a difficult time trying to work out the curves. Therefore I make and fit the floors now whilst I can still use the moulds (molds) as templates.

Just as all the floor joists need to be level to stop us having a bumpy floor in the home, so all the floors on my boat must be level so that the soles aren't bumpy when they are laid down. This isn't easy as the inside of the boat curves in all directions. There is only one straight line I can use and that is the hog: the inner keel that runs the length of the boat, as you can see below (remember the boat is built upside down). 

On the Seagull the hog is horizontal for most of its length so we can call it the Zero datum and take measurements from it.

I offer up a piece of 75mm x 35mm hardwood (Iroko) from which I have cut a notch for the hog to fit into. Below I mark the hog's position on the hardwood.

Having cut out the notch to accommodate the hog I offer it up again, and level it with a spirit-level before clamping it to the mould. 

I now pencil the curve of the mould onto the piece of hardwood. Remove the clamps and cut along the curved line on the floor with a saw.

Next the hardwood is returned to the jig. Once the hardwood is fitted it becomes a floor. 

   As all the floors are made from 75mm wide hardwood, and as they are all notched to the horizontal hog, I know each will be exactly 75mm from the zero datum and my soles will lie flat.

Finally, I will remove the floors and store them for fitting after the planking has been completed.

I also need to bevel the edges of the Moulds (molds) so that the planking will fit flush along them.

To get the bevels right, I use a plank (notice how small the cross section of the plank is) as a batten. 

 I place the batten about half way up the centre mould. With a block plane I bevel the moulds at the spot the batten touches. See small beveled notch on picture below.

Then  I drop the batten six inches and repeat the process for all the moulds. Finally I have beveled notches on all the moulds. I now plane the moulds to join the notches, resulting in fully beveled  moulds upon which the planks will lie flat.

Doing this latter operation is going to take some time.

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