On Apr 8, 9:19 pm, Brian Nystrom <brian.nyst...@[EMAIL PROTECTED]
> wrote:
> Norm wrote:
> > On Apr 7, 9:57 pm, Brian Nystrom <brian.nyst...@[EMAIL PROTECTED]
> wrote:
> >> sa...@[EMAIL PROTECTED]
wrote:
> >>> On Sun, 6 Apr 2008 21:28:05 -0700 (PDT), Norm <normk...@[EMAIL PROTECTED]
>
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/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.
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.
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