On Mon, 14 Apr 2008 07:00:22 -0400, salty@[EMAIL PROTECTED]
wrote:
>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.
>
Certainly the boats were built of green oak as aged oak doesn;t bend
very well.
Bruce-in-Bangkok
(correct email address for reply)
|
