Hi y'all, I was reading an article by Kent Ford in a past issue of Paddler magazine (May/June 1999). The title of the piece is "Make Your Boat Glide". He talks about how rocking fore and aft and side to side cause considerable drag on the hull. Kent claims that, "A barely visible wobble or bob, say one-half inch, is like dragging a coffee cup-sized anchor on each side of the boat." I'm having a hard time believing this. Could someone enlighten me please? Cheers, Wobbly Dave Dave Williams dave_at_paddleasia.com http://paddleasia.com Phuket, Thailand *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Dave wrote; >I was reading an article by Kent Ford in a past issue of Paddler magazine >(May/June 1999). The title of the piece is "Make Your Boat Glide". He >talks about how rocking fore and aft and side to side cause considerable >drag on the hull. Kent claims that, "A barely visible wobble or bob, say >one-half inch, is like dragging a coffee cup-sized anchor on each side of >the boat." I'm having a hard time believing this. Could someone enlighten >me please? > I have trouble believing it too. I can find nothing in my stuff that suggests such a thing and changing the heel such a small amount doesn't change the form characteristics enough to account for it (sometimes the form gets improved by heel). Did Ford say where he got the information? Cheers, John Winters Redwing Designs Web site address, 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.paddlewise.net/ ***************************************************************************
I wrote; >I was reading an article by Kent Ford in a past issue of Paddler magazine >(May/June 1999). The title of the piece is "Make Your Boat Glide". He >talks about how rocking fore and aft and side to side cause considerable >drag on the hull. Kent claims that, "A barely visible wobble or bob, say >one-half inch, is like dragging a coffee cup-sized anchor on each side of >the boat." I'm having a hard time believing this. Could someone enlighten >me please? > John Winters replied: <<I have trouble believing it too. I can find nothing in my stuff that suggests such a thing and changing the heel such a small amount doesn't change the form characteristics enough to account for it (sometimes the form gets improved by heel). Did Ford say where he got the information?>> I looked at the article again and he doesn't say attribute the info to anyone else. John, could you explain how heeling could improve speed? It seems to me like it would be an inefficient action. Wouldn't it, to some small degree, make the boat 'zig-zag' just a little bit? Cheers, Dave Dave Williams dave_at_paddleasia.com http://paddleasia.com Phuket, Thailand *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
(SNIP) > >John, could you explain how heeling could improve speed? It seems to me >like it would be an inefficient action. Wouldn't it, to some small degree, >make the boat 'zig-zag' just a little bit? > I didn't say heeling would improve net speed, what I said was that the form might get improved. For example, a boat with too high a prismatic coefficient for lowest resistance at a given speed might have a lower prismatic when heeled and so, would less resistance. As for net resistance resulting from all factors, that includes many variables. Heeling need not cause zig-zagging. Some people heel their boats to keep them going straight without using corrective strokes (this works particularly well with some solo canoes). Just as I am not convinced that the blanket statement that heel causes more resistance has validity in all cases so am I not sure that heeling will reduce resistance in all cases. I provided the comment example to suggest how the former statement might not apply. Complicated, I know. Like a designer friend once said, "I am not sure I understand everything I know about that." Cheers, John Winters Redwing Designs Web site address, 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.paddlewise.net/ ***************************************************************************
I understand that you couldn't find anything on "changing the heel" but what about "rocking fore and aft and side to side"? Also, what type of boat was Ford discussing? If he was talking about a slalom race boat (very low volume), I would think the already high drag could be multiplied greatly by a side-to-side rocking (not a one time change of heel). Eric -----Original Message----- From: 735769 [mailto:735769_at_ican.net] Sent: Thursday, September 23, 1999 3:34 AM To: Paddlewise news group Subject: Re: [Paddlewise] What a drag Dave wrote; >I was reading an article by Kent Ford in a past issue of Paddler magazine >(May/June 1999). The title of the piece is "Make Your Boat Glide". He >talks about how rocking fore and aft and side to side cause considerable >drag on the hull. Kent claims that, "A barely visible wobble or bob, say >one-half inch, is like dragging a coffee cup-sized anchor on each side of >the boat." I'm having a hard time believing this. Could someone enlighten >me please? > I have trouble believing it too. I can find nothing in my stuff that suggests such a thing and changing the heel such a small amount doesn't change the form characteristics enough to account for it (sometimes the form gets improved by heel). Did Ford say where he got the information? Cheers, John Winters Redwing Designs Web site address, 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.paddlewise.net/ *************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Hi Eric and all, I wrote: >I was reading an article by Kent Ford in a past issue of Paddler magazine >(May/June 1999). The title of the piece is "Make Your Boat Glide". He >talks about how rocking fore and aft and side to side cause considerable >drag on the hull. Kent claims that, "A barely visible wobble or bob, say >one-half inch, is like dragging a coffee cup-sized anchor on each side of >the boat." I'm having a hard time believing this. Could someone enlighten >me please? Eric replied: <<I understand that you couldn't find anything on "changing the heel" but what about "rocking fore and aft and side to side"? Also, what type of boat was Ford discussing? If he was talking about a slalom race boat (very low volume), I would think the already high drag could be multiplied greatly by a side-to-side rocking (not a one time change of heel).>> Kent mentions "rocking fore and aft" but doesn't expand on it for some reason. All he says is, "the hull of a kayak or canoe slows significantly when it bobs front to back, or rocks side to side." He's not talking about any particular boat. There are photos of a couple boats, none of which are slalom boats. It seems to me that a slalom boat might suffer more that other types when it bobs and rocks. Cheers, Dave Dave Williams dave_at_paddleasia.com http://paddleasia.com Phuket, Thailand *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
>I understand that you couldn't find anything on "changing the heel" but what >about "rocking fore and aft and side to side"? Also, what type of boat was >Ford discussing? If he was talking about a slalom race boat (very low >volume), I would think the already high drag could be multiplied greatly by >a side-to-side rocking (not a one time change of heel). > Actually I was considering the side to side motion as well. I could not find anything on that either. An interesting aspect of this involves paddling across waves. We promote narrow boats for seaworthiness because they can easily roll to maintain a more vertical orientation while condemning wide boats that follow the slope of the waves. Thus, the narrow boat gets rolled with the passing waves relative to the water although it rolls less relative to the horizon. The wider boat rolls less relative to the water although it rolls more relative to the horizon. Poses an interesting possibility. Could a wider boat actually have less resistance than a narrow boat? (I can hear Ralph gloating from here :-)) As for the fore and aft pitching ( here I confess I was confused since the quote from the original post said, "A barely visible wobble or bob, say >one-half inch, is like dragging a coffee cup-sized anchor on each side of >the boat." I did not think of fore and aft changes in trim since it is normally called pitching. There we have studies showing that fore and aft pitching does slow the boat from studies done on rowing shells, ships, etc. How ever, for sea kayaks a lot of the what might get perceived as pitching (at least in smooth water) may come from changes in trim due to the acceleration and deceleration of the boat. These changes of trim do not appear to cause increases in resistance. Admiral Taylor says the change in trim is a symptom of speed and not necessarily a cause of increased resistance. We have to contrast this with rowing shells that experience most change in trim due to shifting of weight (sliding seats) and not due to speed variations. I suppose some paddlers might bob back and forth but I have not really noticed it. I will certainly watch for it in the future to see if it occurs. Cheers, John Winters Redwing Designs Web site address, 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.paddlewise.net/ ***************************************************************************
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