Newbie needs advice - CAD to mold

[brywisco]

Hi,

I have been asked to help design a new fiberglass sailboat hull roughly based on an existing hull. I am trying to better understand the overall process during this research phase of the project.

The rough plan is to somehow 'scan' an existing hull to create a 3D file that can then be digitally modified as needed. Any suggestions on this scanning?

I assume that once the design is complete, a plug will need to be machined. Are there places that do this?

I am a mechanical engineer by profession and use AutoDesk Inventor 3D solid modeling software. I am not 100% clear on the best software options to allow me to take a scanned file and thne perform design modifications to it. Any suggestions here are most welcome.

Thanks!

[duluthboats]

It can be done but it’s not that easy. My $.02 is to find a good NA who designs fiberglass boats and has worked with mold builders. He can take the measurements needed to design the hull you want. It would then be your hull not one that was just reverse engineered.

You can get points from a small boat using a frame and pointer sticks. Then transfer these points to sheet stock on the lofting floor. For large boats look at something like Faro laser trackers. They will give you a 3D point cloud you can use to make a digital model. Changing a point cloud to a clean model can be tedious. Most 3D software will except point clouds but some like Rhino are better at working with surfaces.
Gary

[brywisco]

Thanks for the reply and please bear with my ignorance. This marine design stuff is a bit foreign to me. I am not sure what lofting is and am maybe stuck in the mindset of digitally creating the model and then having the plug CNC machined. I will be doing more research on various 3D scanning options. Any more suggestion and/or words of advice??

[lewisboats]

I am wondering...if you are going to take the lines off of a hull that was designed by an NA then modify it...who is going to do the modifying? If an NA is going to do the modifying then he already knows how to pull the needed measurements and if you don't have an NA working on it then how the heck do you expect to be able to modify the boat and have any reasonable expectation that it will perform safely and to its design standards. Even on larger boats seemingly small alterations can cause large changes in performance and safety. Hire an NA that is familiar with how you want to build your boat, point him or her at the one you would like to (loosely) base your hull on and let that person do their job. You will get a much better, safer and liability friendly product in the end and the cost will be insignificant compared to the cost of a poorly or dangerously designed boat and all the tooling involved to produce it.

[duluthboats]

bry,
Please don’t misunderstand us. When I got interested in boat design my background was that of a experienced CNC machinist with many hours working with several CAD systems. I set out, much like you, to draw a hull. I wanted to make a 3D model of my favorite canoe. It was not that easy and very frustrating. I did finally get the model I wanted and many more.

Answers to a few questions may help us point you in the right direction. There may be offsets or plans available for your hull, so you would not have to take the offsets yourself. If it is a small boat I can point you at different ways to get the offsets for your model. A large hull is much more difficult and requires more expensive equipment.

Once you have the model it would be wise to work with someone who builds molds for a living. It can be costly and mistakes are expensive.

Any pictures of the boat would be helpful. At minimum the length and beam would help us help you.

Welcome to the forum,
Gary

[brywisco]

lewisboats,

Very good questions to be sure. I was told the hull will stay the same with just a few slight tweaks to remove imperfections in the original. I am not sure what these imperfections are, maybe it is not perfectly symmetrical or faired. Is this the correct nomenclature??

Does anyone have some good web links describing a typical project similar to this?

[brywisco]

duluthboats,

Thanks for the reply. The hull is a pretty basic racing scow that is 20 feet long with a beam of 5.5 feet.

[lewisboats]

Where is the original file or plan that the hull was developed from? Why not just go back to that and tweak it?

[duluthboats]

Wooden Boat #210 on the news stand now, on page 72 they describe a simple method for taking points off a small boat. If you then transfer these points to a sheet and measure from a base line and the center line you will have your points then you will have to enter them into the 3D software and use them to make you hull. A laser tracker would make getting the points into the software much faster and much more expensive. Getting a nice hull from these points is no simple thing, and will require at least a minimum knowledge of hull design and a high level of proficiency with the software. As I said before, it is much easier to draw your own lines using the old hull as a guide.
Gary