all fired up 6 Posted June 12, 2012 Share Posted June 12, 2012 Am in the early stages of building a new rudder. Does anyone know who in Auckland has a CNC machine that can carve NACA profiles out of foam? Beginning Foam size is 2.5M x 350mm x 30mm a.f.u Link to post Share on other sites
B00B00 310 Posted June 12, 2012 Share Posted June 12, 2012 Yes Stu, Russell Davis 'send it' on this forum runs Absolute CNC http://absolutecnc.co.nz/about-cnc/ Phone: +64 (0)9 444 8511 Email: info@absolutecnc.co.nz Hes a good dude and sails a lot on skiffs and Multihulls, and is a regular for our Winter Poker nights (although hes not very good at either.... He should be able to help you. What exactly are you doing Stu, New rudder for the 930? There might be others keen on doing a similar rudder to spread the cost (maybe myself included). Link to post Share on other sites
all fired up 6 Posted June 12, 2012 Author Share Posted June 12, 2012 Sure is. The plan is to replace the stainless monster and current hardwood glassed over rudder with a new foam-carbon creation. It will be a long tedious job to hand profile the foam so I like the idea of machining the profile in. It will be quicker and much more accurate too. Will let you know how things progress. a.f.u Link to post Share on other sites
Guest Posted June 12, 2012 Share Posted June 12, 2012 I maybe in the market for a new rudder. The existing is going to have a grunt up job as it bends a lot. I was just going to skizz out the sides and load it up with carbon but looking around mine rudder isn't that sexy a shape really. Maybe whack a mold off yours A F U? Link to post Share on other sites
Atom Ant 0 Posted June 12, 2012 Share Posted June 12, 2012 There's nothing wrong with your barn door KM, stick with it! Link to post Share on other sites
203 0 Posted June 12, 2012 Share Posted June 12, 2012 There's nothing wrong with your barn door KM, stick with it! .... Link to post Share on other sites
wheels 543 Posted June 12, 2012 Share Posted June 12, 2012 Oh no, KM's Barn doors are much flashier than that. They even have shiny custom made SST hinges. 30mm thick AFU Wow that's thin. Link to post Share on other sites
all fired up 6 Posted June 12, 2012 Author Share Posted June 12, 2012 30mm thick AFU Wow that's thin. That is the starting thickness for a half. As I understand it the shape can be formed in two halves. One side flat, other side profiled. Then glue the two halves together and hand finish with sandpaper and elbow grease. The final thickness of the foam would be (allowing for material loss when shaping) approx 55mm. Here is a pic of the arrangement I will be replacing. a.f.u Link to post Share on other sites
all fired up 6 Posted June 12, 2012 Author Share Posted June 12, 2012 Maybe whack a mold off yours A F U? No problem. We can wait to see how sexy the finished job looks before any mold whacking is done. Sometimes these things start off with a MKI version in the fired up workshop and reach a MKIV or V version before I am happy with the final job. a.f.u Link to post Share on other sites
Guest Posted June 12, 2012 Share Posted June 12, 2012 Hi yeh can do this pretty easy by drawing on cad or simply getting a drawing for naca off the net then print it at the size you want, may have to paste pages together but thats pretty easy, then make a template by cutting the drawing and pasting on thin customwood and cut carefully. Use the customwood template to cut , with a router with a template flush cut bit, a series of plywood , half inch is good, copies and glue together to form a sanding block with the naca profile. Link to post Share on other sites
Guest Posted June 12, 2012 Share Posted June 12, 2012 this is what i did for hotdogger, didn't cnc because I put a proper spar in it with a nose and trailing edge foam fairing. I will plug in the back up box tomorrow and find some pics Link to post Share on other sites
wheels 543 Posted June 12, 2012 Share Posted June 12, 2012 ah righty, 55mm sounds better. I used the NACA 12 I think it was. But I have a slow moving boat. The inside of my rudder is Ally and there are frames shaped to the NACA profile, which was then filled with foam and then shaped to the frame and then glassed over. It made a rudder 6.5ft high, with a 3'ish ft cord and some 200'ishmm thick and I can lift it on my own. It is bouyant in water and adds floatation to the stern and is light as a feather on the stearing. Link to post Share on other sites
John B 106 Posted June 13, 2012 Share Posted June 13, 2012 For curiositys sake and only if'n it isn't some trade secret, what NACA profile will you use? Link to post Share on other sites
ballystick 72 Posted June 13, 2012 Share Posted June 13, 2012 AFU so you are replacing the rudder stock and rudder as well for a lighter non-lifting one piece, I presume? Link to post Share on other sites
all fired up 6 Posted June 13, 2012 Author Share Posted June 13, 2012 For curiositys sake and only if'n it isn't some trade secret, what NACA profile will you use? There is quite a lot written about rudder and keel profiles if you care to dig around on the internet. As far as I could establish the NACA 0015 profile is a good one to use for rudders. So that is the one I will start with. If you wish PM me your main email and I will email you the profile specs. a.f.u Link to post Share on other sites
all fired up 6 Posted June 13, 2012 Author Share Posted June 13, 2012 AFU so you are replacing the rudder stock and rudder as well for a lighter non-lifting one piece, I presume? That is the current plan. As the project develops I amy change my mind and make up a carbon rudder cassette. Doing this will enable me to easily take the rudder out for cleaning and polishing. a.f.u Link to post Share on other sites
Guest Posted June 13, 2012 Share Posted June 13, 2012 For curiositys sake and only if'n it isn't some trade secret, what NACA profile will you use? Naca sections were the most attainable with relevaint data for some years. So everyone used them. the 0012 and 0015 foils are considered safe. But you may do a lot better with a 63-015 or 63-015a. You can get the dat files buy googling airfoil data base. Then you will find there are thousands of foils availble. You can scale them to different cord width %'s but this will change the working range and propertys. There are many sections that in later years have been developed above and beyond the naca sections. You need to make sure you are comparing apples for apples with the data you are looking at. There are several programs availible that you can enter you foil sections at desired widths etc to compare. Link to post Share on other sites
Guest Posted June 13, 2012 Share Posted June 13, 2012 Here's one example from one of many sites. the section is the 63-015a the other sections listed are close comparasions of other foils. for rudders you want a wide working range, or angle of attack before stalling. then you want the best lift for the least helm angle. then you look at the drag ratios. and lastly will it still work as a barn door after it has stalled. http://www.worldofkrauss.com/foils/1315 Link to post Share on other sites
Guest Posted June 13, 2012 Share Posted June 13, 2012 from the black box, hotdoggers rudder in build Link to post Share on other sites
all fired up 6 Posted June 13, 2012 Author Share Posted June 13, 2012 for rudders you want a wide working range, or angle of attack before stalling. then you want the best lift for the least helm angle. then you look at the drag ratios. and lastly will it still work as a barn door after it has stalled. http://www.worldofkrauss.com/foils/1315 Yes that is what I am hoping to achieve. Did you use the 63-015A profile on Hotdoggers' rudder? a.f.u Link to post Share on other sites
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