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Boat Forum / Building / April 2008Assistance with steam bending kayak ribs
Greetings. I am currently building a skin-on-frame kayak using the standard (classic) text by Chris Cunningham. I have just reached the stage of putting in the steam bent ribs. I realise that this stage is tricky, especially given that he recommends that you get 50% more timber for breakages. I have a specific question which he does not deal with in his book. Cunningham recommends that you start with timber 5/16 inches thick, and that you thin the ends (maybe up to a third of the length of each rib, depending on its length) by 1/16 inch. His instructions tell you to take all of the 1/16 inch off one side of the rib. (In addition to this, the ends of each rib need to be narrowed in order to fit them into the mortices in the gunnells). This means that when you bend the rib after steaming you have a choice of bending it towards the thinned side or away from the thinned side. It seems to me that it would be more likely to split if you bent it away from the thinned side. That is, it would be better to have the thinned side on the inside of the curve. I have not yet broken enough ribs to know the answer to this. Does anyone have an opinion? Or is this likely to be such a minor matter that it will make little difference in the long run? Yours Norm >Greetings. > [quoted text clipped - 27 lines] > >Norm Bend so that the thinned part is on the inside of the bend. The thinned side has more exposed endgrain due to the thinning, so you want that side under compression, rather than trying to pull it apart. The longest unbroken grain is the suide that can best dal with being stretched without splintering. >> Greetings. >> [quoted text clipped - 32 lines] > compression, rather than trying to pull it apart. The longest unbroken grain is > the side that can best deal with being stretched without splintering. While the above is correct if you're going to use Cunningham's method, my personal opinion is that his system just creates more work than necessary. Using 1/4" ribs without any tapering works just fine. If you've already cut your mortises to 5/16", you're stuck, but it's something to consider on your next boat. One thing that is very useful is his pre-bending jig. While the ribs won't hold the shape of the jig, it does make the ends much more pliable and easier to insert into the frame. For other ideas, see my Webshots albums at: http://community.webshots.com/user/brian_nystrom-reg > sa...@dog.com wrote: > [quoted text clipped - 48 lines] > > http://community.webshots.com/user/brian_nystrom-reg Thank you for this comment, and also for the reference to your Webshot albums. Regarding the 1/4 inch ribs, I have been trying to follow Cunningham EXACTLY because I have a history of minor disasters and half finished boats. However, I have not cut my mortices to 5/16, so I do have the choice to try thinner ribs. (There have been things that I thought of changing but I have so far resisted). I have used his jig. One of the problems I had with the first one I made was that it broke apart while I was bending the first rib. I then built another one which was much stronger and which works. However, just last weekend I was wondering if I could make an adjustable jig which would be suitable for keeping the different sized ribs in till they cooled. I notice that your rib jig looks like just such a piece of equipment. I will have a careful look at your photos over the next few days. I am one of those people who do not like to do things quickly and I feel that I work at my worst when I have to make quick decisions. So the description by Cunningham of the rib process had me worried from the start. Many thanks for your comments. >> sa...@dog.com wrote: >>>> Greetings. [quoted text clipped - 46 lines] > choice to try thinner ribs. (There have been things that I thought of > changing but I have so far resisted). One of the best things you can do when building SOF boats is to read several books (Morris, Starr, Cunningham, Petersen, Golden) to give you a better idea of what's possible. You can then match the methods with your tools and skills. There's no need to follow one method from start to finish, as building a kayak is a series of discreet steps that can easily be mixed and matched. > I have used his jig. One of the problems I had with the first one I > made was that it broke apart while I was bending the first rib. I [quoted text clipped - 4 lines] > such a piece of equipment. I will have a careful look at your photos > over the next few days. If you're interested in the jig, I wrote an article on building it for "The Masik" magazine. You can download it at: http://www.qajaqusa.org/newsletter/Masik_Summer2004_06041.pdf > I am one of those people who do not like to do things quickly and I > feel that I work at my worst when I have to make quick decisions. So > the description by Cunningham of the rib process had me worried from > the start. > > Many thanks for your comments. Any time. > >> sa...@dog.com wrote: > >>>> Greetings. [quoted text clipped - 76 lines] > > Any time. Thanks for the general advice. I have read Morris and a book on kayaks by Chappell and another person. I am always trying to be more flexible in my approach, but I do worry about adopting two incompatible approaches. For example, Morris describes doing the deck beams before doing the ribs, whereas Cunningham does the ribs first. As a consequence of this, Cunningham takes measurements for his masik by sitting in the already ribbed kayak, whereas Morris uses another method. I have downloaded your article on the adjustable jig, and lost sleep reading it the night before last. It looks great, and I will have a serious think about it this weekend. Thank you also for referring me to the journal The Masik. Despite a lot of web browsing over the years on issues relating to kayaks and canoes I have never come across it. Many thanks. I'll try to get back to you over the next few weeks about how the steam bending is going, and whether or not I end up using your jig. >>>> sa...@dog.com wrote: >>>>>> Greetings. [quoted text clipped - 76 lines] > by sitting in the already ribbed kayak, whereas Morris uses another > method. Although I build largely using Morris' method, I fit the masik and the foredeck stringers after the rest of the boat is completed. I can't see any advantage to doing it earlier in the process where the potential for error is substantial. > I have downloaded your article on the adjustable jig, and lost sleep > reading it the night before last. It looks great, and I will have a [quoted text clipped - 6 lines] > about how the steam bending is going, and whether or not I end up > using your jig. Make sure you build a good steam box and have an adequate steam source. The latter is especially important. I built my first boat using a teapot on a hotplate, but it was far from ideal. Using a wallpaper steamer as a steam source is a much better way to go. > >>>> sa...@dog.com wrote: > >>>>>> Greetings. [quoted text clipped - 97 lines] > on a hotplate, but it was far from ideal. Using a wallpaper steamer as a > steam source is a much better way to go. Yes, I do have a good steam source. A few months ago I was at a market where a chap sells cheap tools and he had a 15 litre urn for sale. I have made a new lid for it with marine ply and an old vacuum cleaner tube acts to take the steam to the steaming chamber. I have made a steam box out of old floor boards. It is just the right length for my kayak ribs, and has a rack inside to keep them completely suspended in steam. That part of the process seems to be working well. I have started working on the new jig. >> >>>> sa...@dog.com wrote: >> >>>>>> Greetings. [quoted text clipped - 106 lines] >suspended in steam. That part of the process seems to be working >well. I have started working on the new jig. You probably know this but it is not "steam" that makes the wood flexible, it is heat. The old Maine boat builders quite frequently boiled the oak timbers for boats to make them flexible enough to bend into the forms. For some reason they used soapy water for this - never did understand why. Bruce-in-Bangkok (correct email address for reply) >>> >>>> sa...@dog.com wrote: >>> >>>>>> Greetings. [quoted text clipped - 115 lines] >Bruce-in-Bangkok >(correct email address for reply) I think the soap was supposed to soften the outer fibers a little more to help reduce splintering. It probably also helped with the sap that came to the surface from the heat. >>>> >>>> sa...@dog.com wrote: >>>> >>>>>> Greetings. [quoted text clipped - 119 lines] >reduce splintering. It probably also helped with the sap that came to the >surface from the heat. Certainly the boats were built of green oak as aged oak doesn;t bend very well. Bruce-in-Bangkok (correct email address for reply) >>>>>>>>> sa...@dog.com wrote: >>>>>>>>>>> Greetings. [quoted text clipped - 112 lines] > Certainly the boats were built of green oak as aged oak doesn;t bend > very well. It depends on what you call "aged". My experience is that air-dried oak bends pretty much as well as green oak. It requires a little more steamer time (20-30%), since the lower moisture content doesn't carry heat into the wood as fast. >>>>>>>>>> sa...@dog.com wrote: >>>>>>>>>>>> Greetings. [quoted text clipped - 117 lines] >steamer time (20-30%), since the lower moisture content doesn't carry >heat into the wood as fast. I suppose that "aged" was a poor adjective to use as I was referring to properly dried lumber, sacked and dried for a year or more. I'm only reporting what I saw and was told, that fresh cut white oak was much easier to bend then seasoned lumber, and for that reason most Maine working boats were built of "green" lumber. This was told to me by the last of the boat building Carter family who had built boats on Bremen Island for generations. Bruce-in-Bangkok (correct email address for reply) >>>>>>>>>>> sa...@dog.com wrote: >>>>>>>>>>>>> Greetings. [quoted text clipped - 128 lines] >Bruce-in-Bangkok >(correct email address for reply) At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently being restored, they have stockpiles of Live Oak stored for years before it gets used. It's hard stuff to get in big enough sizes for these projects, as no one likes to cut them down. Katrina windfall supplied a lot of what will be used to replace ribs in the Morgan. By the time it gets used, I imagine it's pretty dried out. They have a sawmill on site as well as a huge steam bending rig. The Mystic Seaport website used to have a lot more information about the exhibits on it. <http://www.mysticseaport.org/index.cfm?fuseaction=home.viewpage&page_id=05F74191 -D78C-D0C6-64E2AB6C7E72F3B6> >>>>>>>>>>>> sa...@dog.com wrote: >>>>>>>>>>>>>> Greetings. [quoted text clipped - 142 lines] > ><http://www.mysticseaport.org/index.cfm?fuseaction=home.viewpage&page_id=05F74191 -D78C-D0C6-64E2AB6C7E72F3B6> That is all well and good but I got my information from a Mr. Chester Carter who's family had built boats on and around Muscongus Bay since sometime in the 1600's. To be frank I will always have more trust in what he told me then what all the lads at Mystic Seaport say. I saw the half models his great grandfather had made dated in the 1700's (always wished I'd asked him for one) and the hand made tools he had inherited from his ancestors. No, I had a chance to learn a bit from an individual who's family had built boats in Maine for some 350 years, a considerably better education then I believe I could have gotten at Mystic. Captain Chester had built some 60-odd working boats with his own hands and had fished lobsters from a sloop and I'll stick with what he taught me. Bruce-in-Bangkok (correct email address for reply) >>At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently >>being restored, they have stockpiles of Live Oak stored for years before it gets [quoted text clipped - 26 lines] >and had fished lobsters from a sloop and I'll stick with what he >taught me. The "lads" at Mystic? Seems you have exactly NO idea what you are talking about. They have a LOT more knowledge and experience to draw upon than some little family operation in Maine building work boats. Has Mr. Chester built anything like the Amistad? Has he restored and maintained anything approaching the size and scope of the Morgan? The Mystic Seaport has. They have also accurately researched and restored a few hundred historical boats and ships. Your Mr. Chester could probaly learn quite a bit from them if he apprenticed himself for 30 or 40 years. >>>At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently >>>being restored, they have stockpiles of Live Oak stored for years before it gets [quoted text clipped - 36 lines] >probaly learn quite a bit from them if he apprenticed himself for 30 >or 40 years. You must think that I'm from Arkansas or some such place. I was born in New England and grew up there. Built (with a great deal of help from my father) my first boat when I was 10 years old. I am quite aware what Mystic is and what they do. I am also aware that a vast amount of their "research" as all research of old time stuff is, consisted of talking to people like the Morse family and the Carter family and other Maine boat builders and writing down what the old folks thought that they remembered about what Uncle Henry used to do. Well, I did the same "research" as they did, except I got the information from the guy that actually did it. Not from Uncle Henry's grand daughter. The trouble is that I'm old enough that I've seen some of the old timers and heard some of their stories. I've seen boat carpenters (as they called themselves) that could square a 12 inch timber with an adze and broad axe, not a power plane. People that had actually fastened the planking to a schooner hull with treenails, not just "researched" it. As far as "accurately researched" even Chapelle included lines in his books taken from hulks or boats badly out of shape. It make's one wonder how accurately some of these restorations would have been working from lines that were stated by the fellow that took them off to be in some part guess work. I'm not trying to denigrate anything that the Mystic people do I'm simply saying that what I learned I learned from the people that actually did it for a living. Bruce-in-Bangkok (correct email address for reply) >>>> At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently >>>> being restored, they have stockpiles of Live Oak stored for years before it gets [quoted text clipped - 67 lines] > Bruce-in-Bangkok > (correct email address for reply) My dad can beat up your dad! Come on guys, there's no real "sides" here. >>>>At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently >>>>being restored, they have stockpiles of Live Oak stored for years before it gets [quoted text clipped - 65 lines] >simply saying that what I learned I learned from the people that >actually did it for a living. You clearly have no clue as to what The Dupont Preservation yard does at Mystic Seaport. It ain't really just book larnin'. These are among the very best and most knowlegeable "old school" shipwrights anywhere in the world. Your buddies couldn't begin to do what these folks do (for a living). >>>>>At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently >>>>>being restored, they have stockpiles of Live Oak stored for years before it gets [quoted text clipped - 71 lines] >in the world. Your buddies couldn't begin to do what these folks do >(for a living). If a guy who's family had built boats for 350 years "couldn't begin to do..." how did those guys learn how to do it? Did they climb a mountain and get some stones with the instructions carved on them? And, how is it that you are so knowledgable about how qualified a craftsman my old friend was? Do you have second sight? It is obvious that you are a "born again" boat builder and nothing done outside the fence at Mystic is of any value so lets just drop the whole thing. You troop down and take the sacraments every week and I'll stay home and steam bend wood. It is obvious that trying to carry out a conversation with you is about as productive as trying to talk to Osama. Bruce-in-Bangkok (correct email address for reply) >>>>>>At Mystic Seaport, where the Amistad was built and the C. W. Morgan is currently >>>>>>being restored, they have stockpiles of Live Oak stored for years before it gets [quoted text clipped - 74 lines] >If a guy who's family had built boats for 350 years "couldn't begin to >do..." how did those guys learn how to do it? They have access to a wider range of knowlege that someone who labors alone or with just a few others in a small shop will never have. This is why you can learn more at Harvard than you can from one guy on a porch swing who has never traveled more than 10 miles from his home. >Did they climb a >mountain and get some stones with the instructions carved on them? See above >And, how is it that you are so knowledgable about how qualified a >craftsman my old friend was? Do you have second sight? See above >It is obvious that you are a "born again" boat builder and nothing >done outside the fence at Mystic is of any value so lets just drop the >whole thing. You troop down and take the sacraments every week and >I'll stay home and steam bend wood. See. That's exactly the problem your boy Chester has. He could have learned so much more if he hadn't stayed isolated at home. >It is obvious that trying to carry out a conversation with you is >about as productive as trying to talk to Osama. What was that about second sight? When did you last speak to Osama? >Bruce-in-Bangkok >(correct email address for reply) |
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