I’ve made a few videos on designing lures in Fusion 360, but I realized that the techniques I was using were fairly advanced and I completely skipped over a lot of the simple techniques for designing lures that will produce some great baits. Today we’re going to fix that by creating a simple curly tail grub using only three functions- sketch, extrudes and fillets.
First up, I want to share a tool that I think is critical for my design, the digital caliper. I have trouble visualizing dimensions in my sketch and comparing those to the actual size of an object. It’s also great for taking measurements of existing lures, say you have a lure that has the same size body as the one you have in your mind. You can just take a measurement using the digital caliper and put that into your design, it’s really handy. The link to the one I use is here but you can find these just about anywhere such as Lowe’s Home Depot, Harbor Freight, Northern Tool. All those types of places will have a simple digital caliper, you just want to make sure it has millimeters and inches.
So a few things to think about. First, before you actually dive in and start designing, you need to think about the overall length of the body and the length of the tail. If you’re making an injection mold you need to know where you’re going to split it and typically, for ease, you only have one split. So let’s jump into Fusion 360 and get stared.
First, I’m going to sketch the front of the lure. In this case, I’m going to use a simple 10 millimeter circle. The important thing here is that I’m placing the center of the circle on the center point of the Fusion 360 plane. This will make lining everything up and keeping everything symmetrical much easier. Then, I want to draw a center line that is the same length that I want the body of my lure to be. Now, I could have done this first and I probably should have, but the order at this point doesn’t really matter. The center line is just going to sit here to give me an idea about how far to actually extrude when I’m ready to. This is about simplicity, not accuracy. I work in millimeters because I’m going to 3D print this and 3D printers work in the metric system. Luckily Fusion 360 is smart enough to do the math for me. I can pull out this line and I can simply type 3 I N (for inches) and Fusion 360 does the math for me and converts those three inches directly into millimeters which is really nice.
Now the fun begins! The extrude command takes a sketch or a face and just pulls it out and makes it solid. It’s a very simple yet very powerful function inside Fusion 360. I could take this circle and pull it all the way down to the end and have a basic tube, but that’s pretty boring. What I want is my grub body to have a little hump in the middle so to do this we use the taper angle feature in the extrude command and make it a positive number. It’s going to grow out as I extrude and I usually just eyeball this step until something looks right. Again, we’re going for simple here not exact. So I get it stretched out to something I like then hit enter. I want to stretch out the hump section a little bit so I click on the back face of the taper and just extrude it out. Again, I’m just pulling and eyeballing it, we’re not engineering anything to specs at this point. Now, what I want to do on the tail is to take this hump section and taper it down relatively small, at least compared to the front of the lure. To do that I’m going to use the same extrude command, click on the back face, but instead of a positive number I’m going to put in a negative number. The negative number will shrink it down as it tapers and again I’m eyeballing this process.
So now that we have the basic shape of the body of our grub, what I want to do is smooth out these very sharp angles. So I’m going to use the fillet command and sand down those edges and make them a bit rounder. I click on the front face and hit the fillet icon and, again, just eyeball the process. You can type in a number if you know the number you want to use. Sometimes it’s easier to type and change the numbers but I’m just going to move it and see what I like. I’m going to hop over to the backside and do the same. What I’m going to do on the backside is I want it to be as close to a circle on the end as I can so I’m just going to pull it out until it gives me an error message. That error message means I’ve gone too far and from there I’ll back it up just a little bit.
So now that we have our body shape, let’s work on the tail. The tail is pretty simple, what I’m going to do is draw a sketch on the middle plane. Since I centered my circle in the beginning, I know that the middle plane is in the center of my lure body. So I draw a line across and I’m not too worried about getting it in the center and you’ll see why. I’m just giving it a basic width at the base then I use the fit point spline tool, which is how you draw curves in Fusion 360. The more points you have, the more control you have so you can usually be pretty “click happy” as you go around and make your points. Don’t try to add too many, but definitely have more points than less. If you want to add another point, you can simply right click and the click on insert fit point spline.
So I’m just going to sketch out a rough diagram on one side and try to match it up to the other side. I’m pretty terrible when it comes to drawing curly tails and I’m sure there’s a better technique out there to do it. Again, I’m just trying to show you an easy way to get a basic lure design. You can sit here and fiddle with these fit points all you want. Once you draw these out, hit the escape key t get out of the fit point spline tool. You can drag and click any of these points and you can also click a pint and then it has these green handles. The green handles let you move around and shape the angles of your fit point spline.
So again, we’re going to go back to the extrude command and exit out of the sketch. Hit extrude then select your drawing. The difference we’re going to make here is we’re going to make this a symmetric extrude and what that does is it takes the plan and instead of extruding the sketch one direction it extrudes it in both directions the same exact amount. So the number you type in here is going to be doubled to make the overall width, depth and height of your tail (how thick it is). So in this case, I want about a four inch thick tail, again it’s totally up to you on what you want, but I want four inches. So I type two in the box and we have a four inch tail. It’s not perfect, in fact it’s terrible.
So what I’m going to do is actually change the sketch that I had use in the original tail, this is a very powerful feature in Fusion 360. I simply right click on the sketch down in the timeline- hit edit- sketch- and that bring me back to my lure. I grab the points I made and I’m going to bring them to the inside of my body. So now it comes out of the body around and I actually find it easier to start wide, do the tail, and then come back and change the sketch. I’m not sure why, it just works for me better.
So now, we got our tail and we go back to the fillet command. Make sure you fillet the top and the bottom to make sure you can select them both at the same time. Now we’re done! We have a very simple curly tail grub. Next what you would want to do is probably make a mold so I have a couple of mold making videos and I’ll be doing a new one that has a simpler technique if you want to check it out. If you want to see how to add details like ribs and eyes to this lure, click here.
Take care everybody- tight lines