Darn it!! I just slipped with the power rasp, and now there is a huge gouge just where I don't want it. What to do? Bondo comes to the rescue. It's cheap, easy to mix and apply, sticks fine to wood, and sets to a workable state quickly. The only downside is that it smells bad. By the time I finished the model of my boat 2, it was almost all Bondo. You can also use various epoxy mixes at greater expense and less convenience. Mistakes are not the end of the world; they can always be repaired. We are not constructing Chippendale furniture here, and you will not be graded on appearance.
Finally, after (mumblemumble) hours of work, you have half a quarter-scale model of a canoe. It's beautiful (Bondo not withstanding). Now you must proceed to destroy it. Well, you could opt to use some other approach to getting your stations, but this one seems easiest to me. Ah, wait! Before you ruin your beautiful model, you may want to get load waterline information. Since this is going to require immersing your model in water, I would recommend spraying the model with a couple of coats of polyurethane varnish, just to protect it from water absorption, which could cause the wood to swell, distorting your hard-earned lines. It won't be in the water for long, so a thick coat of varnish (which could alter your shape) isn't necessary.
I have never actually done this, but here is my guess as to how to go about it. As Cat has pointed out, the volume of a quarter-scale model is one sixty-fourth of the full-size version, so the test weight should be one sixty-fourth of the design weight as well. Suppose my target load is 260 pounds for boat, paddler, and gear. My model should weigh one sixty-fourth of that, or four pounds, one ounce. If we weigh the model and are lucky, it will be lighter that four pounds, so by adding a bit of weight we can bring it to the correct amount easily. Suppose that our model weighs six pounds. Maybe we should have made it from cedar instead of that old slab of oak we had lying around. Oh well, too late now. We are going to have to reduce the weight by about two pounds. We can do this by partially hollowing out the model, but we want to avoid removing wood where the stations will be, for reasons that will become apparent later. I would do this with a drill press and a Forstner bit, which is guided by its rim, enabling it to cut partial holes without wandering around. I would want to stay at least half an inch away from the locations of the stations (in other words, each station location should have an inch of wood), and half an inch from the centerline plane. One would have to be very careful not to drill through the hull, although an error or two could be corrected with Bondo. On second thought, in view of the difficulty of holding the model firmly while all this drilling is going on, perhaps a die grinder would be better. I leave this procedure as an exercise for the student.
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Finally, after (mumblemumble) hours of work, you have half a quarter-scale model of a canoe. It's beautiful (Bondo not withstanding). Now you must proceed to destroy it. Well, you could opt to use some other approach to getting your stations, but this one seems easiest to me. Ah, wait! Before you ruin your beautiful model, you may want to get load waterline information. Since this is going to require immersing your model in water, I would recommend spraying the model with a couple of coats of polyurethane varnish, just to protect it from water absorption, which could cause the wood to swell, distorting your hard-earned lines. It won't be in the water for long, so a thick coat of varnish (which could alter your shape) isn't necessary.
I have never actually done this, but here is my guess as to how to go about it. As Cat has pointed out, the volume of a quarter-scale model is one sixty-fourth of the full-size version, so the test weight should be one sixty-fourth of the design weight as well. Suppose my target load is 260 pounds for boat, paddler, and gear. My model should weigh one sixty-fourth of that, or four pounds, one ounce. If we weigh the model and are lucky, it will be lighter that four pounds, so by adding a bit of weight we can bring it to the correct amount easily. Suppose that our model weighs six pounds. Maybe we should have made it from cedar instead of that old slab of oak we had lying around. Oh well, too late now. We are going to have to reduce the weight by about two pounds. We can do this by partially hollowing out the model, but we want to avoid removing wood where the stations will be, for reasons that will become apparent later. I would do this with a drill press and a Forstner bit, which is guided by its rim, enabling it to cut partial holes without wandering around. I would want to stay at least half an inch away from the locations of the stations (in other words, each station location should have an inch of wood), and half an inch from the centerline plane. One would have to be very careful not to drill through the hull, although an error or two could be corrected with Bondo. On second thought, in view of the difficulty of holding the model firmly while all this drilling is going on, perhaps a die grinder would be better. I leave this procedure as an exercise for the student.