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#1
posted to rec.boats.building
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Assistance 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 |
#3
posted to rec.boats.building
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Assistance with steam bending kayak ribs
On Apr 7, 9:57 pm, Brian Nystrom wrote:
wrote: On Sun, 6 Apr 2008 21:28:05 -0700 (PDT), Norm wrote: 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 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 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 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. |
#4
posted to rec.boats.building
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Assistance with steam bending kayak ribs
Norm wrote:
On Apr 7, 9:57 pm, Brian Nystrom wrote: wrote: On Sun, 6 Apr 2008 21:28:05 -0700 (PDT), Norm wrote: 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 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 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 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). 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 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. 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/M...2004_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. |
#5
posted to rec.boats.building
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Assistance with steam bending kayak ribs
On Apr 8, 9:19 pm, Brian Nystrom wrote:
Norm wrote: On Apr 7, 9:57 pm, Brian Nystrom wrote: wrote: On Sun, 6 Apr 2008 21:28:05 -0700 (PDT), Norm wrote: 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 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 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 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). 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 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. 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/M...2004_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. 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. |
#6
posted to rec.boats.building
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Assistance with steam bending kayak ribs
Norm wrote:
On Apr 8, 9:19 pm, Brian Nystrom wrote: Norm wrote: On Apr 7, 9:57 pm, Brian Nystrom wrote: wrote: On Sun, 6 Apr 2008 21:28:05 -0700 (PDT), Norm wrote: 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 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 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 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). 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 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. 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/M...2004_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. 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. 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 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. 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. |
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