Tuesday, March 16, 2010
Transom and how to's...
Today I took off work around 3:00 and went till 7...
I started out with a template of the stringers that will become the cockpit sides.
The easiest way I've found to start a project that hangs in space... Is to build a 2 dimensional outline that can be hung in space, defining a few planes.
In this case, I have some very straight 2x4's that are marked out in 6 inch increments from the aft end of the cockpit back. In addition to this, I have lines drawn square to the faces... so I can measure down with a tape measure or folding rule (folding rule gets a better fit) and jot down the measures on a notepad. The easy way is feet, inches, 8ths. When you go to warp a batten around something 16ths don't matter very much.
Good batten material: buy a #1 kiln dried treated 2x4 that is perfectly straight, no knots around 10 feet long... Rip with the grain... Feel around for hard spots and thin it down if there are any. Its not so important for lofting lines that it be perfectly the same width, as it is that it'll bend to your marks evenly. If you are jointing with a table saw... rip off one side, put your ripped side to the fence... rip again... then take your pass. I like around a 1/2 inch thick for big boat stuff... Rip a bunch of them, as they age some turn to hockey sticks/firewood.
From here, I marked out a piece of flat birch plywood... doesn't do you any good to make a template out of scraps that aren't straight and flat. I used a sheet rock t-square and made lines every 6 inches, then laid a piece of brown contractors paper across the plywood, and remade my lines. If it fits right the first time, I have my template for the other side... but where the paper comes to shine, is doing what I did here. See the tall section at the far end? I measured down from the underside of my 2x4's... You can either do the math to add a few inches to every measure, or just slide the paper to where it looks right... and or, find a piece of scrap that it lays over but didn't have a factory side to loft off of...
Next, take a screw and lay it on your marks... smack it with a hammer. Your mark is transferred from the paper to the plywood quite nicely. Now warp a batten around and play connect the dots with a pencil. Let it fly where ever it runs natural... this is just a template.
Take it to the boat, screw it to your bridge... now take a compass with a pencil, lay it on the hull and scribe the line. 3/4 or 1 inch is a good setting... measure it and jot it down on the piece. Go back and cut it out with a jig saw (or a circular saw like I did here... it's faster.)
If you are doing a bulkhead that has a sole that is flat... I build a carpenters square that stands on its own... a 1 ft square piece of 3/4 as the base, and two 2 foot tall by 1 foot wide pieces screwed together. Now if your floor is square you have something to align to, something to screw a piece of luan to for a joggle/tick stick...
Anyway, next up I cut the transom flat. I said yesterday I was going to loft a 1/2 inch curve into it... I decided today that flat will work just fine. A Triton's transom curves out 5 inches from square, per the plans... 3 1/2 inches at the top by my measuring. Mine was 2 1/2 inches taller than flat, so you have options. Either warp a batten around it, or take a piece of doorskin and roughly scribe the transoms curve on it. Then transfer that to a piece of 3/4 plywood that is wide enough not to lose its flatness... then come back and lay a pencil on top and scribe your line. If you like it... come back with a sharpie.
Once I scribed my line, I measured it out... 32 inches from the bottom of the heart to each corner, and 21 to the middle.
I cut the transom with a thin metal cut-off wheel (1/8th inch) on a 4.5 inch grinder. I always cut this kind of thing at an angle, where the back of the cut is much higher than the line, in case of goofs. If you try to hold it perfectly level, and things go awry you have to make it grow back.
I also advise cutting a 1/4 inch higher than the mark. It doesn't take long with 40 grit on an 8 inch grinder to turn a whole boat into dust. I came back with a straight edge and played with it till it looked right.
After that the weather started going south, so I fired up the grinder and attempted to burn off all the gelcoat on the port side. Didn't make it all the way... but total time invested hit 16 hours for the port side. She has an 1/8th inch of white, on top of the black tooling gel... It's about like firing up a grinder on a parking lot.