Re: transom and deck

DELFTship forum Hull modeling transom and deck Re: transom and deck

John R. Coil

I can tell you one advantage of using a curved surface rather than a cylinder: with a cylinder it’ll have the opposing surface that intersects your model so that when you intersect layers it will put points there too. These can sometimes have an effect on the way a model renders.

Now, about getting that first curved surface.

Yes, start with a vertical plane.

And, another Homer moment here for me, you really don’t have to worry about the math or the scientific calculator so much. Remember those offsets I gave you for a radius of 4.8333? Well, once you’ve got a surface typed in using those values you can scale it (Transform > Scale) in the X and Y direction to get any diameter you may want. Just use your ordinary calculator to divide the radius you want by 4.8333 and then use that number for the scale function.

Also, I found I need to correct something I wrote earlier about the math for ovals being more involved. While this is certainly true what I realize now is that rotating the circle results in oval shapes if you were to cut a horizontal or vertical cross-section through it. You vary the actual shape of the oval by increasing or decreasing the angle of rotation.

Which means that selecting all the CPs on the top of your curved surface and Transform > Move them into place on your sheer line and then to do the same with the bottom of your curved surface, moving it to the place you want on the keel, is how you actually get a true-circular surface cutting through where you want your transom to be.

This last has also proved an easy way to use different radii — you can scale the top line and bottom lines independently of each other. Doing this seems to give you control over two other important aspects of any transom: where it connects to the sheer line and how far forward it sweeps. For example, say you wanted the sheer line to join with the side of the hull 2′ forward but doing so makes the thing sweep around dramatically and it just doesn’t look right. If you made the radius of the lower edge of your surface larger you can try to tone down this effect if it is unwanted. In this last instance I “know” it’ll work but I suppose it depends on the model and your preferences how much can be achieved with it.