If anyone else EVER needs to fabricate a new piece of aluminum to go along with replacing their wood piece ... I'm putting a ton of details in this post here: https://www.tinboats.net/forum/viewtopic.php?f=3&t=37548
If you don't know what 'hammer forming' is, it is a method of forming metal alloys by annealing the piece of metal and then using a form and a large, heavy flat-faced hammer or mallet of wood, nylon or rubber (but NOT metal) to bend and coax the metal to form a new shape. I have attached a PDF showing someone making a round dome out of 1/8" thick aluminum. They made it look easy!
With a properly annealed piece of metal, the metal will stretch or shrink, depending on whether or not you are doing an inside or outside formed corner. You can see my layout lines, as I just drew a central line (square the the transom), then others lines parallel to it and 2" out on each side, then measured just to the 'top' of the radius of the bend.
Annealing:
I used 5052-H32 alloy, the same as Starcraft used, and it anneals at 650-degrees F while it's melting point is > 1100. I bought one of those special TempilStiks brand sticks that melts at the temperature you want. I use to use low-temp ones to troubleshoot OB thermostats, so I was very familiar with their use.
For heat I bought a MAPP gas gun and nozzle, as most cheap propane nozzles shouldn't be used with MAPP gas. This nozzle gave a great flame tip and the alloy heated up quickly - just DO NOT keep flame in one spot. I found it best to start from an end and work a 3-4" area. Once the tempstik melted on that area I moved on. On the corners, one must heat the ENTIRE surface or it won't fully shrink or stretch, but will ripple on you.
This was my 1st time doing this and I found the aluminum to be pretty forgiving. Aluminum will naturally harden in air and it also work hardens, so when forming that 1st corner, once it started to be more difficult than it should have been ... I stopped and annealed it again.
I think the pictures tell the story pretty well! The picture that looks like I 'scribbled' all over it is where I kept the tempilstik marker moving searching for it to form or melt into a liquid at the right temperature to anneal the metal. I didn't form the 'V' at the center of the hull and up to the other side yet, but I was able to test fit the starboard corner into the existing stern-less hull and I'm pretty pleased!
If you don't know what 'hammer forming' is, it is a method of forming metal alloys by annealing the piece of metal and then using a form and a large, heavy flat-faced hammer or mallet of wood, nylon or rubber (but NOT metal) to bend and coax the metal to form a new shape. I have attached a PDF showing someone making a round dome out of 1/8" thick aluminum. They made it look easy!
With a properly annealed piece of metal, the metal will stretch or shrink, depending on whether or not you are doing an inside or outside formed corner. You can see my layout lines, as I just drew a central line (square the the transom), then others lines parallel to it and 2" out on each side, then measured just to the 'top' of the radius of the bend.
Annealing:
I used 5052-H32 alloy, the same as Starcraft used, and it anneals at 650-degrees F while it's melting point is > 1100. I bought one of those special TempilStiks brand sticks that melts at the temperature you want. I use to use low-temp ones to troubleshoot OB thermostats, so I was very familiar with their use.
For heat I bought a MAPP gas gun and nozzle, as most cheap propane nozzles shouldn't be used with MAPP gas. This nozzle gave a great flame tip and the alloy heated up quickly - just DO NOT keep flame in one spot. I found it best to start from an end and work a 3-4" area. Once the tempstik melted on that area I moved on. On the corners, one must heat the ENTIRE surface or it won't fully shrink or stretch, but will ripple on you.
This was my 1st time doing this and I found the aluminum to be pretty forgiving. Aluminum will naturally harden in air and it also work hardens, so when forming that 1st corner, once it started to be more difficult than it should have been ... I stopped and annealed it again.
I think the pictures tell the story pretty well! The picture that looks like I 'scribbled' all over it is where I kept the tempilstik marker moving searching for it to form or melt into a liquid at the right temperature to anneal the metal. I didn't form the 'V' at the center of the hull and up to the other side yet, but I was able to test fit the starboard corner into the existing stern-less hull and I'm pretty pleased!
... now to fit it, then rivet her back together ... and THEN pour the ceramic core transom material.
