Subject: Re: [baidarka] Bending ribs on Greenland
From: steveJ (vtboat@VERIZON.NET)
Date: Sun Feb 29 2004 - 20:34:10 EST
Flat?? I was thinking the ribs needed to be SLIGHTLY arched. I was not
intending to make the keel any deeper.
Also, I am building a Southwestern Greenland style, not a baidarka.
I agree...boats built intuitively are alive.
I am looking at a drawing (fig 206) on page 210 of Chapelle and Adney's
Bark and Skin Boats of North America and the ribs amidship seem to be
slightly arched..not flat. I believe a flat bottom section would be
weaker. Fig. 208 on page 211 has a flatter bottom. Perhaps this is the
type of boat you build? The difference between these two boats is
interesting. The fig 208 boat has almost a flat bottom. The figure 206
boat has more deadrise.
James Mitchell wrote:
> If you arch those ribs (assuming i understand what you mean), you will
>never keep that hull upright. The strength of this hull likes in its
>flexibility, which is far more than any traditional hull. You are best
>to follow the traditional building methods as closely as possible.
>Baidarkas are alive. They are not machines. You don't so much build
>them as grow them. Do you have Brinck's book? Wolf has the best
>description. I build my hulls a little differently than his, but close.
>
>I have seen a lot of new builders put all kinds of intellect and love
>into creating a hull, and then been unable to paddle it. You can use
>frames to approximate the shape of the first few ribs, but a soon as
>those ribs are installed, take the frames out. And don't mess with the
>shape of the hull. The ribs need to be flat on the bottom when viewed
>from inside the hull. The depth of the keel will then create just the
>right amount of vee to give good tracking performance. If you add any
>depth, the hull will be unstable. Build a half dozen of these and
>paddle them before making changes.
>
>
>On Mar 1, 2004, at 8:23 AM, steveJ wrote:
>
>
>
>
>>This would also eliminate using those fairing blocks on the keelson.
>>It
>>would also allow the rib to naturally bend in a parabolic curve to only
>>the amount needed to reach the keel and chines. It seems like it would
>>be stronger to have the ribs arched on the bottom rather than flat like
>>some I have seen.
>>
>>
>
>
>>steveJ wrote:
>>
>>
>>
>>>So you are essentially doing it the way I suggested rather than the
>>>way
>>>I have seen it done in Cunninghams book for instance?
>>>
>>>James Mitchell wrote:
>>>
>>>
>>>
>>>
>>>
>>>>I still install the ribs hot. When the ribs are being installed, the
>>>>chines lift up off the section molds in order to fit into the
>>>>mortises.
>>>>Then I lash the chines to the installed ribs, and remove the molds. I
>>>>also pin these ribs to the gunwales by drilling a 1/8" hole through
>>>>the
>>>>gunwale and rib end as it rests in the mortise, and then inserting a
>>>>bamboo skewer into that hole. This locks the initial ribs in place,
>>>>and
>>>>allows me to frame the rest of the ribs to that point. The objective
>>>>is
>>>>to produce a final shape that does not have bumps and valleys.
>>>>
>>>>On Mar 1, 2004, at 7:58 AM, steveJ wrote:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>The section molds would be removed with the method I am describing.
>>>>>How would the flexibility be effected? The finished structure is
>>>>>the
>>>>>same either way.
>>>>>
>>>>>James Mitchell wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>I have used station frames to approximate the shape of the chines,
>>>>>>but
>>>>>>I remove them as soon as I can. I set a couple ribs on either side,
>>>>>>and
>>>>>>then take them out. These hulls have much more flex than a carvel
>>>>>>hull,
>>>>>>and I think the frames would interfere with that.
>>>>>>
>>>>>>On Mar 1, 2004, at 7:27 AM, steveJ wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>I'm about ready to start bending some ribs on a Greenland style
>>>>>>>kayak.
>>>>>>>I've been using various books and information resources for
>>>>>>>techniques
>>>>>>>and procedures.
>>>>>>>One thing that puzzles me is the way that the ribs are bent free
>>>>>>>hand
>>>>>>>to the desired
>>>>>>>shape and then the longitudinals are lashed in and faired.
>>>>>>>Doesn't it make more sense to set the longitudinals in place using
>>>>>>>section molds with notches cut to
>>>>>>>receive the keel and chines and then bend the ribs by steaming and
>>>>>>>springing the rib to the points
>>>>>>>established by the longitudinals? This would follow traditional
>>>>>>>bent
>>>>>>>frame carvel planked boatbuilding
>>>>>>>methods and would eliminate the novice having to try to "eyeball"
>>>>>>>the
>>>>>>>correct shape of the rib. It would
>>>>>>>also eliminate having to calculate the length of the rib prior to
>>>>>>>bending. Just bend the rib roughly so it fits
>>>>>>>between the gunnels and clamp it to the keel and chines. When
>>>>>>>dry,
>>>>>>>mark and cut the ends by adding the depth of the mortises. Remove
>>>>>>>the
>>>>>>>keel and chines which are temporarily lashed in place and install
>>>>>>>the
>>>>>>>ribs in the usual manner. Although the bend would be a bit
>>>>>>>tighter
>>>>>>>than the real distance between gunnels, it seems like it wouldn't
>>>>>>>matter and the ribs would have some spring back and fit in the
>>>>>>>mortises anyway What am I missing?
>>>>>>>-
>>>>>>>Baidarka Mailing List - All postings copyright the author and not
>>>>>>>to
>>>>>>>be
>>>>>>>reproduced outside Baidarka or Baidarka archives without author's
>>>>>>>permission
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>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>James Mitchell
>>>>>>Email: baidarka@earthlink.net
>>>>>>Japan: 090-4974-3874
>>>>>>Japan (from USA): 011-81-90-4974-3874
>>>>>>US Message Phone: 425-424-1325
>>>>>>-
>>>>>>Baidarka Mailing List - All postings copyright the author and not
>>>>>>to
>>>>>>be
>>>>>>reproduced outside Baidarka or Baidarka archives without author's
>>>>>>permission
>>>>>>Submissions: baidarka@paddlewise.net
>>>>>>Subscriptions: baidarka-request@paddlewise.net
>>>>>>Searchable archive: http://rtpnet.org/robroy/baidarka
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>-
>>>>>Baidarka Mailing List - All postings copyright the author and not
>>>>>to be
>>>>>reproduced outside Baidarka or Baidarka archives without author's
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>>>>>Searchable archive: http://rtpnet.org/robroy/baidarka
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>James Mitchell
>>>>Email: baidarka@earthlink.net
>>>>Japan: 090-4974-3874
>>>>Japan (from USA): 011-81-90-4974-3874
>>>>US Message Phone: 425-424-1325
>>>>-
>>>>Baidarka Mailing List - All postings copyright the author and not to
>>>>be
>>>>reproduced outside Baidarka or Baidarka archives without author's
>>>>permission
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>>>>Subscriptions: baidarka-request@paddlewise.net
>>>>Searchable archive: http://rtpnet.org/robroy/baidarka
>>>>
>>>>
>>>>
>>>>
>>>-
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>>>be
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>>>
>>>
>>-
>>Baidarka Mailing List - All postings copyright the author and not to be
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>>
>>
>>
>>
>James Mitchell
>Email: baidarka@earthlink.net
>Japan: 090-4974-3874
>Japan (from USA): 011-81-90-4974-3874
>US Message Phone: 425-424-1325
>-
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