Basic programs instead of pen and paper

[droussel]

Hi,

I received my first lesson from the YDS a couple months ago and am currently also reading "Principle of Yacht Design". I also previously read Element of Yacht design (8th ed. by Francis Kinney), Elements Boat Strenght by Gerr, Preliminary Design of Boats and Ships by Hamlin and other books recommended over here. Please note that I consider that I should read them all over again a couple times!

So now, I have read a lot of stuff, have a small idea of where to start and what to do (while keeping the books near) and have a first sailboat I would like to design. A small 20 foot cabin daysailer able to serve as a weekend "camper" also. Something which exists by the hundreds and nothing exotic. One has to start somewhere!

However, all this is mainly a hobby for now and I can't invest thousands of dollars at once into it. At first I thought about buying the manual drafting tools but I now realize that this will cost me an arm and a leg! A set of curves, spline weights, planimeter, it sure isn't cheap!

So I thought that hey, a computer sure can do all of this for cheaper (I'm a software programmer by trade, so am naturally inclined to use a computer) but Rhino3D and Orca3D, MaxSurf or the others are also costing a lot of dinaros! DELFTShip Free seems to be great tho. However, all of those have a steep learning curve and, for now, I'd rather invest time in learning the proper calculations and design process then learning to use a complicated software.

So, finally, I guess my question would be the following. Is there a simple software I could use to replicate what paper, pen, splines, weights and a planimeter do? Something simple to draft with and calculate the needed areas, lenghts, etc etc? Could a simple 2D CAD software like ViaCAD do what I want? What would you suggest to a beginner like me?


Thanks a lot,

Daniel

[terhohalme]

First do the parametric study of existing ones. Study the succeed ones, why are they so successful? Notice dimensions, ratios and coefficients. Then deside main dimensions, L/D, SA/D, coefficients like Cp and Cb of your new one. Solve displacement (based on L/D) and sail area (from SA/D). Check stability and performance (Dellenbaugh). Draw first lines, notice LWL, BWL and Tc. Calculate displacement, Cp and LCB etc. and compare to your readings... And start it all over again... When you feel totally dazed, you have found your design spiral.

Study Delftship (or Freeship). If they have too steep learning curve to model your hull, just forget it and focus on entertainment. You just need all the mistakes and frustrations to become something... Experience - an organised bunch of mistakes

Wellcome on board! Happy design.

[masalai]

http://freeship-plus.pisem.su/indexEN.html When I was using it on Linux via WINE (Wine is not an emulator) set up as XP... Not easy to get the best out of it but free (GPL) and you will get there eventually...

It is not a professional package, but a good and effective learning experience will automatically do displacement and quite a few other calculations - there are some tricks to get it to do a cat effectively... That you must learn and experiment... derived from Delft/free-ship when they were GPL...

Freeship+ or Delfship get you further. The learning courve is not steep. Or lets say, if that is too steep, you should give up on boatdesign.

Both ARE professional tools in the hands of a professional, they are nothing worth talking, in the hands of a person with a exaggerated opinion of himself.

Too many around here asked for the same and went disappointed.

There is no free ride, use a tool when you know what it is good for, and ask a pro if not.

In your case, I would recommend to spend the 125$ or so, for a pro version of Delftship.
To test the capabilities a download of the (similar) Freeship might be a good idea.

Regards
Richard

[Leo Lazauskas]

I agree with the other three respondents, but I would also recommend that you try using Excel (or write your own short programs) to do some very simple calculations.

For example, first try to calculate hull section areas and waterplane areas by integrating curves given the offsets of a hull.

Then try to calculate the displacement of the hull. How does it compare to the values given by Delftship or Freeship?

Calculating wetted area is a slightly tougher calculation, but you should be able to do it using Excel.

These are tedious exercises, but invaluable because you are bound to make mistakes and thereby learn a lot as Terhoholme noted.

Good luck!
Leo.

[alidesigner]

QCad and Progecad are low cost alternatives to Autocad. Alibre has a limited free verion for simple 3D stuff.

[terhohalme]

Leo, that's the way my students have to start. One more excel sheet of parametric calcs will help a lot.

[Leo Lazauskas]

Originally Posted by terhohalme

Leo, that's the way my students have to start. One more excel sheet of parametric calcs will help a lot.

There are many small traps for beginners in Excel. E.g. confusing natural log and log base 10 in the ITTC skin-friction formula.

Leo.

[terhohalme]

And angles in radians...

[Leo Lazauskas]

And bozos using non-metric "systems"...

[TollyWally]

"And bozos using non-metric "systems"..."

Sadly perhaps that would be me. inch's, 1/8, +-

[Leo Lazauskas]

Originally Posted by TollyWally

"And bozos using non-metric "systems"..."

Sadly perhaps that would be me. inch's, 1/8, +-

Don't feel too bad. There has to be one last person in the Whole Wide World (tm) who uses non-metric.

Cheers,
Leo.

[droussel]

I'll start with DELFTShip and spreadsheets and look into the inexpensive CAD systems to design the accomodations.

Thanks a lot for your answers!

[mcollins07]

Droussel,
I can second many of the things which have already been said.
Spend considerable time analyzing other designs. I think Bolger's boats are wonderfully transparent in their design and their analysis should be part of any cirriculum. along these lines of Analysis, I can recommend a program called DPlot. It will help you analyze curves. I do a lot of caculations in Excel, with VBA modules. FreeShip is excelent, and since it is free, a good place to start. I've used Turbo CAD version 9.1 for basic 2D CAD, and it has served me well. I hope you are not going to exclude pen and paper, a set of ship's curves, etc. Once I get a design close to reasonalbe, I print it out on cardstock and tape it together to see the 3D model. FreeShip will show locations of stress on the developed panels. The paper modle will give you a real feel for any of these stress points. I have about 100 of these paper models in my office now, they make interesting office decore.

~ Michael