Rev. Engineering Fins for 3D Modeling

Good Morning, I am currently trying to model fins in a 3d modeling package. I am able to make the fins visually acceptable but the way I am doing it is just by “eyeing” fins that have already been fabricated. While this is not what I have set out to do initially, I am just trying to find a consistent way of defining a fins characteristics and foil, so instead of visually tweaking out a fin on the computer, or tracing out shape, I need to have “hard” numbers to play with. Anybody have a source for a starting point, or any ideas on how to accomplish this would be appreciated. Thank you, Ryan

Ryan, check this link http://www.bits.com.au/immersion/microscribe.htm I’ve used this before to import bottom shapes to a CAD package.It works better with smaller scale surfaces - fins would before easy !!

Thanks John for your post, so are you importing point cloud data from the microscribe? I have been involved with using a larger scale optical 3d scanner but I found that it was very difficult to process the point cloud into a useful surface. I know the auto industry uses this process alot with their prototype models that way they can get really complex organic surfaces easier than trying traditional computer modeling techniques. I have found that using a 2 rail loft technique works best but I am having trouble finding out where on the profile to split it into the two rails I need. And what ends up happening is my isocurve runnin up the middle of the fin kind of veers up and points “into the sky” which causes an “ugly surface” although it looks good shaded, it is not a proper model. Thank you again for you response, Ryan G PS. I hope I didn’t scare anyone with the title of this thread, my point is not to reverse engineer any patented fins, I am just trying to find out a proper technique for designing my own fins by learning from other fins that i can get my hands on to measure.

Ryan, the problem you identify was why i didn’t purchase the hardware.With surfboards you have to create some sort of jig to hold the board PERFECTLY still and sample along multiple axis eg. center line and template outline.The biggest Microscribe scanner had a 60" reach, so you need to work from the mid-point forward and back with absolutely no movement of board or scanner.You then need to place an isometric projection onto the top and bottom surface to produce a grid not unlike the tool-path maps for the KKL machine, for example. The difference being that you need the horizontal axis as well at even increments tail-to-nose wrapping around to model the rail ! Your probably getting the picture about why i didn’t take it further - the labour for scanning one board would probably be worth more than the cost of the whole board !!! I’ve found DAT 98 Designer far more cost effective for CAD work, but for small scale stuff it would be great to have Microscribe 3D.A good question is whether the DXF files that Microscribe exports could be compiled with the DAT 98 files (also DXF) ? eg. bottom shapes, as DAT 98 can’t do concaves - only Vee. But aligning the various components could be a nightmare.