Gardner
I would suggest you take a look at JavaFoil. It has the ability for multi-elements and a wide variety of shapes. For sails I use thin cambered plates. You have to realise though this can take a positive pressure on the lifting side whereas a sail cannot.
I think JavaFoil gives most insight into the flow around foils and sails. It does not take long to get useful insights. The AR correction for 3D situations gives you an idea of how this alters the L/D.
You can download the Applet and run from normal desktop system.
It is possible to get carried away trying to eek out the very best efficiency of a particular component that may not make much difference in the final result.
Rick
On 25/05/2011, at 11:28 AM, Gardner Pomper wrote:
Rick,
That is far beyond the level of effort I am capable of putting into it. I was hoping there was a simple subset that I could just alter sail and rudders with that would give me the VPP to plot into a polar diagram. I am looking for a +/- 10% solution to see what difference a taller mast makes vs 2 short ones, etc. I am guessing from the completeness of your answer that I can't just plug a speed vs resistance dataset in for the hull and accept that as a constant while I play with the lifting foils. I will keep this email as reference and I will dip my toes in if I ever get the time.- GardnerOn Tue, May 24, 2011 at 7:56 PM, Rick Willoughby <rickwill@bigpond.net.au> wrote:
Gardner
Most of the software I use is all available free although I use the professional version of Delftship for some of the features that provides.Delftship - Is a very good tool for fast hull rendering - as long as you realise it is a surface modeller, it takes about 2 weeks of regular use to master. One nice feature is that it can produce .mlt files for input to Michlet. I also use Deltship for producing 3D milling files and 2D cut files.Michlet - has been developed by Leo Lazauskas and it marries Michel's slender hull wave theory to selectable viscous drag formulas. A powerful feature is the hull optimising routine within it called GODZILLA. This is available free but Leo has recently set up a donation scheme. You need to read the manual and it will take about 1 week to get it functioning. It will take a couple of years to appreciate the results and get to grips with all aspects it offers. I use the 7 function version but there are versions with many more adjustable parameters. It is possible to generate hull shapes that do not produce waves at a particular speed but they are not the lowest drag.JavaFoil - It is user friendly foil analysis software. It has very useful standard foil generation functions. It is only 2D but has 3D correction factors. It does not iterate on flow separation so will not be reliable when this occurs like at a rounded trailing edge. Xfoil does iterate but it is not as user friendly as JavaFoil.JavaProp - Is useful for fast prop analysis. I have my own prop tool in Excel/Visual Basic that covers a wider range of operation and foil type than JavaProp can handle. My software considers cavitation and includes an optimising function.Flotilla - is another of Leo's products. It enables hull trim to be determined and gives the near hull wave profiles. There is a free version that has limited functionality that I use. Leo is selling the full version for AUD15k. There is no manual for what I have but there is the data files for my V14 on the web that can be modified to suit any particular hull.Savitski modellers - there is at least one web site with Savitski models for planing. There are also spreadsheets around. There are some good NACA papers with formulas for flat panels. Leo has his lsp program but it does not correlate well with the empirical stuff.VPP - I do my own in Excel. These use combination of regressions based on data from some of the above for the force determination and geometry for force resolution. I have quite a few of my hours invested in the proa VPP and my pedal boat VPP.Shaft analysis - the curved prop shaft I use on the pedal boats is hard to get right. I have fatigue analysis for various materials and do dynamic analysis in Excel/ VB for the biomechanical efficiency and the way it will "feel". The shaft for my new boat is CF spun to my spec and cost me AUD300 for a 220g shaft - it is important to overall efficiency. I do not have reliable fatigue data for the CF so this will give me a basis to work from.There are lots of other little programs around that give insight into things like viscous flow and panel methods if you want to go deeper into what tools like JavaFoil and Michlet are based on.Leo's stuff may look clunky with outdated interfaces but he aims for processing efficiency. Once you set up file paths and learn to use the in.mlt files it is very fast. Delftship will import the offset files that GODZILLA produces. There were some anomalies between Delftship and Michlet but I think these have been sorted. The power becomes obvious when you watch a basic hull shape morph into the lowest drag form.If you Google around with the names above then you should find the software to download. Just be careful not to spend so much time trying to get it right inside a computer before you get something in the water.RickOn 25/05/2011, at 5:24 AM, Gardner Pomper wrote:Rick,
Can you tell me what I would need to get in order to calculate a polar
diagram for my harryproa designs? I imagine it is a bunch of software.
Is it something that a lay person can run, or will I need to learn
hydrodynamics (I am a software geek). I am hoping that we are talking
FOSS software (Free and Open Source).
I can run linux, windows or os/x, so just let me know what platform you use.
- Gardner
Rick Willoughby03 9796 24150419 104 821
Rick Willoughby
03 9796 2415
0419 104 821
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