Hi Rick,
Thank you for going to all this trouble. I think this is just plain FUN designing, learning, etc. As I have bought wood and started building the leeward hull, I'd have to say, its pretty much fixed below the water line. The details are in a previous email and in the Files folder.
After I build the basic box, I do plan on seeing what kind of deformation I can readily do along the center-lines of the panels to induce a little curvature for structural and possibly drag benefits. I'll do some follow up with Michlet to see if there are any noticeable differences.
I'm sure your assessments on everything are correct... I don't doubt it for a minute. But, I'm not here to just thoughtlessly use someone ideas. I need to understand and be able to apply the concepts also. I want to be able to adjust aspects for the design based on my specific requirements and see where the assumptions lead me. I understand and like the train-of-thought you gave for the windward hull design. I just need to be able to immerse in it and be able to follow the path to the same solution. I'll be working on the windward hull next since I'm getting quite intimate with Godzilla. As build time and expense top the list, your last design is the leading and only candidate. After that, I'll need to start ramping up on JavaFoil so I can see how you did the Q stuff for 007. (Black magic on NACA07031), I'm still ramping up on my finite element analysis
tools and will be double checking for hull and beam strengths. Probably do some modal analysis just for fun. I am considering several beam configurations and will be pursuing those also.
Basically, my idea is to build as I go and fix design elements as late as possible in the process as I learn more and listen to you, Todd, Rob, et al talk about other stuff.
But then again, I'm also planning ahead. For instance, I begun the thought process on cheap instrumentation. For all our analysis tools we have ONE very major hole. We cannot quantify dynamic lift. My leeward hull is 8.5% less efficient. As expected, my Flotsam stuff shows it has static down trim under load. No big surprise. Obviously, your past Flotilla work using wave theory indicates for these long, slender hulls have significant up trim. It doesn't take much of a leap of faith to believe there will be some (maybe significant) lift. Whereas the optimized rounded hull won't lift, this flat hull may lift enough to reverse the 8.5% deficit and actually reduce drag at speed. It is my hope! Maybe, I can instrument and get an empirical method... then we'll all have some real numbers to feed into the design process.
Looking forward to it! (Design, Analysis, Fabrication, Brain Storming, BSing about boats... and... Sailing a Proa)
Dennis
PS - Thank you Todd. You definitely started this frenzy with the inspiration of your prototypes.
From: Rick Willoughby <rickwill@bigpond.
To: harryproa@yahoogrou
Sent: Mon, August 9, 2010 9:11:47 AM
Subject: Re: [harryproa] Re: Asymmetric Bi-directional Rudders
Rob
The ts section is not particularly good. Tom arrived at it by chasing the pressure profile rather than a derived camber to get the ideal camber. I tried what he did and got similar ordinary results. The 07 series has a mathematically derived camber line so is about as good as you can get for a near constant pressure profile.
I did a comparison of the ts P30120 section against the NACA07310 and a NACA0012:
The 07 series has a wider working range than the ts P series and much lower drag. They should be designed to operate with a Cl of around 0.3 so will have heaps of reserve. Their operating angle would be only a few degrees.
I am putting together a VPP for Dennis's test proa. If he eventually settles on some hull shapes I will get on with it. I want to look at the merit of different ideas I have and the best way is to analyse over a range of conditions rather than speculate. I have found that what seem good ideas are not so good once analysed.
Rick
On 09/08/2010, at 10:30 PM, Rob Denney wrote:
On Mon, Aug 9, 2010 at 1:37 AM, bjarthur123 <bjarthur123@ yahoo.com> wrote:
i wonder whether there has been any more development since. in particular i wonder whether any boats have been built with such rudders and what control system they are using. that search is next on my long "to do" list...
I built Speer foils for one of the test bed harrys. Set up to rake them aft to get the balance correct. Tiller steered. I found that when they were turned one way, flow stayed attached and they were great. The other way, the flow seperated much earlier and they were hopeless. Could have been lousy shaping, but I have never had problems with NACA foils built the same way.They were not high on my to try list as the NACA 0012 skeg rudders are working well. Thanks to Rick, Todd, BMWO, those bloody mothies and sundry other contributors to this site, the "to try" list is getting way out of hand. Look forward to seeing some new results.Moved the Sol hulls and beam out of the shed and onto the grass today for assembly when the mast os built. Bit of a task single handed, but nothing got dropped. Start sanding and painting El on Thursday.rob
Rick Willoughby
03 9796 2415
0419 104 821
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