Only thing left is to add a 1/8 x 1/8 piece of basswood to the center section of the water channel, and fill what was left with balsa. I don't have any pictures of that process.
I like my decks to be inset, so I cut off about 3/8" from the edges, and glued the cut off section to the subdeck. I always make sure to use only the highest quality clamps.
You can see here that the center section is now filled with balsa, and the stern solid area is sanded to shape.
With the basic hull completed, I moved on to the motor mount. I will be using 2 motors, direct drive. Mount is made from an aluminum sheet. All the features were created on a mill, then the ears were bent on a brake.
Another view, sorry for the poor focus. I created these holes with a pretty neat process called thermal drilling. Oversimplified the process uses a carbide shaft that is run at high speed, creating lots of heat and deforming the metal into the volcano shape as the metal heats up and deforms around the tool. It is very useful when you want to tap a thin piece of metal, because it approximately doubles the number of threads you can get in the thin material since you are threading the original material as well as the volcano.
Completed mount with motors attached. I will be swapping the brushed motors out for brushless during final assembly. I wasn't brushless friendly yet when I originally set this up.
This sounds awesome and I love the results. Is this something one could do at home within 'reasonable' cost?
Thermal drilling should be able to be accomplished on a decent drill press on it's highest speed. On a hole this small somewhere north of 2000 RPM should do the trick. That's probably at the upper end of what a lot of drill presses will do. The "tool" I used was just the back end of a carbide drill with a bit of a shape ground on the end of it. If you look up thermal drills or thermal drilling (watch some videos of the process in steel - really cool) and find a picture of one of the tools you get an idea of the shape. For our purposes it's not terribly important. Carbide is hard to grind and really requires a grinding wheel capable of it. A high speed steel drill would *probably* work to drill aluminum, but I haven't tried it. Carbide is definitely a must if drilling steel. I did use a drop or two of lubricant to keep the aluminum from galling and depositing material onto the drill, but just a tiny amount, and only apply once to the tool, you don't want to use enough that it interferes with the heat generation. Then just use between light and medium pressure to feed the bit through. The trick is to allow it to heat up and soften the metal before you start applying more pressure. A little practice is all it takes. To make a long story even longer..... it is totally achievable for a very reasonable cost, virtually free if you are drilling aluminum and can get away with high speed steel.
Aluminium is all I'd be trying to work. Thanks! I'm totally going to try this out at some point. (after I go look at the belt chart on the drill press of course...)
Depending on hole size, you can get away with less RPM. I think my holes were for a 6-32 thread forming tap (not a thread cutting tap), so it was pretty small... needs more RPM to get the heat... experiment and you can probably get away with less in aluminum. I used a drop or two of tapping fluid as an anti galling lube. Aluminum likes to heat up and build up on the tool. Some type of oil would probably work as well, I haven't tried it though.
Looks like I can get up to 3000rpm on my press. Could a person cheat a bit and use a torch to preheat the workpiece and bit?
Adding heat other than what the tool generates *may* have a negative effect, softening the material adjacent to the intended area. Just an educated guess. At 3000 RPM the tool will generate more than enough heat to achieve the objective. Without a professionally made tool, ideal speeds, and proper feedrate and feed control, the results probably won't be perfect, but will likely suffice for our purposes.
I made these little sleeves out of stainless steel to adapt the existing motor shafts to the same diameter as the prop shafts.
