3D Laser Scanning of a FreeFall Lifeboat

[cnzlp]

Hello everybody,

I work in a lifeboat manufacturer located in turkey. We produce totally/partially open lifeboats, rescue boats and freefall lifeboats.

We are planing to start a new project which is basically extending the lenght of our GRP Free Fall lifeboat in order to increase its capacity. The lifeboat we are using as reference is our old model sized 6,89 x 2,89 x 3,14 (m) with a capacity of 27 persons.

Present digital data for this boat is very limited. We only have a 2D autocad file of the general arrangement plan and unfortunately the linesplan is not available. Thats why we cannot make an accurate 3D model to work on.

Therefore I suggested to 3D scan the lifeboat and get an accurate 3D model. This, in my opinion will save time and money and also avoid potential mistakes to be made during the design of the extended model.

Here comes the reason i decided to post in this forum;

Is there anybody that can give me details about 3D scanning. Someone who has previously worked on such a project? Approximate price of 3D scanning for such a boat, things we have to be careful during and before scanning, problems we might encounter, etc.

I have requested quotations from 3 companies that provides solutions for 3D scanning and modeling. But they seemed quite expensive and I want to have the precious opinions of experienced naval architects following this forum.

Thank you very much in advance, I am awaiting your opinions and comments.

Can Ozalp

[Eric Sponberg]

Usually in 3D scans you get what is called a "point cloud" which is a record of points in space on the surface of the hull, and in your case, also the canopy. After the point cloud data is taken, one has to create the surfaces through those points. You have to decide first on what surfaces to create--such as flanges, bosses, recesses and protrusions and the like--and then draw those surfaces such that they pass through as many of the points in the point cloud as possible. The measurer will best serve you if he/she creates a point cloud that mimics hull lines, especially at regular stations (and fractions of stations), waterlines, buttocks, and the like. Also, things like keels and skegs have to be measured at discrete and regular points so that they become defined in the final model.

The creation of surfaces from the point cloud is as much art as science, and someone who has knowledge of how boats are designed and built will go a long way towards getting you the information that you need. I have dealt with measurers who know boats, and other who don't have a clue about boats, and the ones that know boats and boat building are far superior to those measurers who don't see a boat as anything other than a 3D object. Boat shapes require after-the-fact calculations, and the more the point cloud follows the geometry necessary for those calculations, the better off the model is.

As for price, in my experience, a good measurer is going to start at about US$5,000 just to leave the office and get set up. Post processing, if they create the surfaces, is going likely be another US$5,000 to US$10,000, depending on how much detail is required in the final model. If your shipyard is adept at 3D modelling, then you may need only the point cloud yourselves, and can do the surface modelling, calculations, and final drawings yourselves.

I hope that gives you a good data point.

Eric

[DGreenwood]

Eric
Next time you need a measurer, give me a shot. I'll beat the hell out of those prices and I will be more accurate and provide a more useful model.
I use Close Range Photogrammetry and the process takes place mostly in the office. The photos are quick and easy and only require good light. No need to clear away the boat yard for 50 meters around the subject.My equipment cost less than a tenth of a laser measurer and I can take it in carry on baggage. A 7 meter boat shouldn't cost that much!

[Eric Sponberg]

Originally Posted by DGreenwood

Eric
Next time you need a measurer, give me a shot. I'll beat the hell out of those prices and I will be more accurate and provide a more useful model.
I use Close Range Photogrammetry and the process takes place mostly in the office. The photos are quick and easy and only require good light. No need to clear away the boat yard for 50 meters around the subject.My equipment cost less than a tenth of a laser measurer and I can take it in carry on baggage. A 7 meter boat shouldn't cost that much!

Thanks, Dennis, I'll remember that.

[Joe Petrich]

Your comments are spot on Eric.

[yipster]

Can Ozalp, dont know why and what you need 3D files for but realise scanning remains a aproximation
may be close but still..
its also posible to draw fairly realistic 3D drawings from 2D drawings and/or photos at less cost
all depends what its for

[cnzlp]

Thanks for your comments eric.
@ yipster, we need the 3d files so that we can get a linesplan and calculate hydrostatics. Also we ll model the new lifeboat by extending it using 3d modeling softwares and make stress analysis, freefall simulation (that i still dont know how and etc. You say its an approximation, do you know another way to do reverse engineering with a smaller tollerance? I think you can get the closest results with this method.

Thanks for sharing your ideas but i have to say that unfortunately I got some quotes from local companies that provide the solution but due to financial reasons we decided to continue with conventional methods for modeling.

[DCockey]

Laser scanning can have accuracy of several millimeters or better for boat size objects.

How accurately the measured data that translated into a virtual model depends on the methodology used to build the model from the scan data, the experience and skill of the operator, how much time the operator puts into building the model, and the software used. This is true for any source of data.

NURBS based modeling software such as Rhino3D and Alias allow any desired degree of fidelity although there are tradeoffs. My limited experience with FreeShip showed that the division methodology used is basically not capable of putting the surface directly through the input points, though it will be "close" and may be "close enough".

[yipster]

thx for the eye openers, few mm eh? from what i've seen few millimeters diffrence is actually normal welding cnc alu plates
and well said: experience, skill, time and software are essential, i would never be that close to the mm from 2d cad and photos
think the real cost is not the 3d model one way or another, but how you want to use it, that'll be some expensive simulations
have a certification in bottom draw on stress analises in acad ansis but after that never used it, no use!
only try'd fluid dynamics demo's, fascinating stuff yet not enouch skil nor experience..
for advertising however i can do a 3d liveboat drawing doing an animated -blunt?- nose dive

[gadu]

Hi All,
I'm new to the forum, but have a lot of experience in laser scanning. We have already preformed few scans of different size boats, from 50 to 7m long yachts. If you have any questions regarding laser scanning or would like to know if it ir the right technology for you, please get in touch.
Dan