On Mon, 14 Apr 2008 12:41:27 +0700, Bruce in Bangkok
<b*paige*125@[EMAIL PROTECTED]
>
wrote:
>On Sun, 13 Apr 2008 21:19:48 -0700 (PDT), Norm <normkelk@[EMAIL PROTECTED]
>
>wrote:
>
>>On Apr 11, 8:46 pm, Brian Nystrom <brian.nyst...@[EMAIL PROTECTED]
> wrote:
>>> Norm wrote:
>>> > 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.
>>>
>>> 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 im****tant. 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.
>>
>>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.
>
>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)
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.
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