A couple of people have asked about how flow gets determined in the tank so I may as well post it for everyone. The most common method uses yarn or plastic streamers. In some cases these get taped right to the hull and in others they get suspended away from the hull on small wires. Another clever method uses finely ground aluminum particles suspended in the water. This works best in observing the flow form overhead. Another method uses dye that is injected in front of the boat's path. This works OK but the dye soon dissipates. In wind tunnels smoke provides visual evidence of flow. Taylor coated the models with sesquichloride of iron mixed with glue. Then he injected pyrogalic acid through a small hole resulting in a smear of ink that revealed the flow. He would then drill a new hole where the ink smear lost definition until he eventually worked his way to the stern. For flow away from the he used meshes of fine string or wire coated with sesquichloride of iron and injected pyrogalic acid at known points. Taylor says," The relative flow indicated in the immediate vicinity of the model is found as regards to type quite a distance from the skin, so as regards motion near the hull we need consider only the disturbance close to the bottom, or the lines of flow as they may be called." These days I think this gets done mathematically since one doesn't mess up the tank or models. One of the things that impress me has to do with the similarity in flow lines for widely divergent hull shapes. The flow lines (crudely done with yarn I admit) I got on my sprint boats looked remarkably like those I got for my canoes and they looked remarkably like the ones Taylor got on his ship models. Matt asked why I thought the flow would dive under the hull and I must answer "I don't know" but the evidence points to something other than water being pushed only to the side. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Announcing a new domain name for my old site - http://www.onwatersports.com Please update any links you might have, and send along any commentaries. Andree Hurley Hurley Design Communications - ICQ# 27469637 Web Sites for Specialty Businesses - http://www.viewit.com/HDC/ Kayaking - http://www.onwatersports.com *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
-----Original Message----- From: Andree Hurley <ahurley_at_viewit.com> To: PaddleWise_at_lists.intelenet.net <PaddleWise_at_lists.intelenet.net> Date: Tuesday, May 25, 1999 10:40 AM Subject: [Paddlewise] New domain name - onwatersports.com >Announcing a new domain name for my old site - >http://www.onwatersports.com > >Please update any links you might have, and send along any commentaries. > >Andree Hurley >Hurley Design Communications - ICQ# 27469637 >Web Sites for Specialty Businesses - http://www.viewit.com/HDC/ >Kayaking - http://www.onwatersports.com Hi Andree Your site gave me a server error of some kind when I tried to submit the following: Glad to see your site is up and running again. Please note the information on how not to buy a stolen kayak you attribute to John Kurtz was originally written by me and distributed to many kayak shops from here to San Diego when we were trying to catch Ron Freeman. As OOC was one of the shops I faxed it to John was probably just passing it on when you snagged it. You will find the latest version at www.marinerkayaks.com. Also, You may want to make a link from the stolen kayak section to www.marinerkayaks.com as I have a database of about 140 stolen kayaks there in an organized form that the buyer or potential buyer can access fast to see if his or her kayak is on the list. There is also a questionnaire that directs a victim to supply information that is more usable than the often incomplete information they tend to leave in bulletin posts. You might be able to use it (especially the parts of it I publish) as a guide to the information they need to provide to increase the odds of getting their kayak back. Finally the last kayak on your list (stolen from Lake Sammamish) was returned to its owner when I recognized its similarity to one the police had confiscated from a truckload of stolen goods and were calling kayak dealers about to try and find the owner. Although the colors they called it were quite different there was enough similarities to make me suspicious it might be the same one. It was. Oh, I think our new website has a lot of information in the manuals section that could be of value to sea kayakers whatever boats they paddle. You might want to consider a link. Matt Broze > >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.gasp-seakayak.net/paddlewise/ >*************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Thank you Matt for bringing this to my attention! As it turned out, the program running the stolen boat board had somehow become corrupted. It's great when visitors actually turn in errors, especially to a large site that is mostly maintained by one person. (The site has many background programs including a bulletin board, seven guestbooks, one chat page (meet at a specified time such as 7:00 pm pst). The guestbooks include kayaks wanted/for-sale, lost/stolen, jobs wanted/offered (new), and general for announcements.) It has been in existance since 1995 and has a life of it's own! Andree Hurley Hurley Design Communications - ICQ# 27469637 Web Sites for Specialty Businesses - http://www.viewit.com/HDC/ Kayaking - http://www.onwatersports.com On-Line Editor Canoe and Kayak Magazine - http://www.canoekayak.com/ Original message: > Hi Andree > Your site gave me a server error of some kind when I tried to submit the *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Matt and John are discussing whether water is displaced sideways (Matt's idea) or vertically (John's idea). To them I ask, why one or the other, and not a combination of both? My intuition tells me that water is displaced normal to the local surface of the hull, and probably in a uniformly thick layer. At least for a smoothly varying hull. If each parcel of water is not displaced in the normal direction, then water pressure anomallies are created as the parcel collides with an adjacent parcel in one direction, and leaves a void in the other direction. I would further imagine that this effect is what creates extra drag and initiates turbulence. A cylindrical hull would minimize this effect, and so to those who know, I ask could this be why the fastest hulls are more cyclindrical in cross-section? Of course sea kayaks aren't just interested in pure speed and therefore are willing to sacrifice a little speed for better handling. Another interesting question is what happens to the displacement direction of water at a hard chine? Cheers, kevin ___________________ / Kevin Whilden \ |Dept. of Geosciences ___ |University of Washington \ |kwhilden_at_u.washington.edu| ________________________/ On Tue, 25 May 1999, John Winters wrote: > These days I think this gets done mathematically since one doesn't mess up > the tank or models. Can this really be done mathematically? I thought that calculations of flow for any object that moves on the interface to two different fluids was extraordinarily difficult. If it can be done... how? > > One of the things that impress me has to do with the similarity in flow > lines for widely divergent hull shapes. The flow lines (crudely done with > yarn I admit) I got on my sprint boats looked remarkably like those I got > for my canoes and they looked remarkably like the ones Taylor got on his > ship models. > > Matt asked why I thought the flow would dive under the hull and I must > answer "I don't know" but the evidence points to something other than water > being pushed only to the side. > > Cheers, > John Winters > Redwing Designs > Specialists in Human Powered Watercraft > http://home.ican.net/~735769/ > > > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Kevin wrote; >Matt and John are discussing whether water is displaced sideways (Matt's >idea) or vertically (John's idea). I think I may not have made myself clear. I said that the flow dives under the hull and follows the buttuck lines. As the water dives under the hull it displaces water to the side. This is established by flow tests in tanks (not my idea although I wish I had thought of it first). The result (Admiral Taylor appears to be the first to show a proof) has had repeated support in other tanks and tests. >To them I ask, why one or the other, >and not a combination of both? My intuition tells me that water is >displaced normal to the local surface of the hull, and probably in a >uniformly thick layer. This sounds so logical that one likes to accept it and I once thought the same thing (as did a lot of sailsboat designers). How disappointing to discover that water didn't see things our way. :-( >Another interesting question is what happens to the displacement direction >of water at a hard chine? The chine tends to redirect the flow much as fins or keels etc do. Nick provides a good example of the effect of flow under the boat. I will ask Professor Inverbon about the Brit boats. David wrote; >I have observed bulbous bows on commercial vessels. I recall reading that >they are used to increase fuel efficiency. I have wondered what effect one >might have when used on a kayak. (Other than being an efficient kelp catcher >that is.) Bulbs have positive effects on resistance through wave cancellation. They only work when the bow is fully immersed and kayaks rarely spend much time in conditions where the bow can stay immersed. Also, their draft works against them in this respect. Followers of Baidarkas will have read Dyson's comments on this as an explanation for the bifid bows on some baidarkas. Regrettably, videos show the bow emerging from the water. I say regrettably because one would like them to work. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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