Message-Id: <199610082107.OAA25327@ns1.intelenet.net>
From: Wolfgang Brinck <wolfgang.brinck@hksystems.com>
Subject: Re: Fwd: Re: Construction Underway
To: baidarka@lists.intelenet.net
Date: Tue, 8 Oct 96 16:03:08 CDT
In-Reply-To: <199610081752.KAA14373@dfw-ix9.ix.netcom.com>; from "Robin McDaniel" at Oct 8, 96 10:52 am
>
> You wrote:
>
> I have used a type of willow which grows in marshy areas of
> Wisconsin. It is not a tree but a bush form of willow. It works fine as
> long as the branches I pick are big enough. The tendency is to use
> lighter
> twigs since these bend more easily, but resist the temptation and stay
> with the stouter branches. A light frame is a pleasure to paddle but
> will compress and deform if not strong enough when you put on your
> skin.
>
>
>
> This brings to mind the movie Ran, based on Shakespear's King Lear.
> (Maybe this line was in King Lear a well, but I haven't read or seen
> it). Anyway the Old king is trying to convince his sons to work
> together after he splits up his kingdom among them. He says that small
> sticks are easily broken when taken individually, but are strong when
> taken together. The sons don't listen very well.
> Anyhow, I wonder if the advantages of the small willow twigs could
> be used by bundling several together. They could then be easily bent,
> and should hold their shape after they are tied together. Has anyone
> tried this?
>
>
> -- Andy Wones
>
You could space the ribs more closely and then use smaller diameter ribs.
However, let's say you split each rib in half to make it easier to bend
and then put the two halves in the same hole. You would have the same
strength since you had the same amount of wood, however, you would have
less total stiffness since stiffness goes up with the square of the
thickness, or is it the cube? I will look this up. Let's assume that
it's a square relationship, then the two half ribs would only have
.7 the stiffness of a single rib of the same total thickness. So to get
same overall stiffness of the hull with more smaller ribs would mean
using a lot more wood, meaning you would end up with a heavier boat.
The issue here is not resistance to breaking so much as resistance to
compression. If the ribs are not stiff enough, they will compress
when you put on the skin and your hull will deform. But if you did
use enough smaller twigs to achieve a hull of equivalent stiffness,
you would have a stronger hull but also one that was heavier.
I have used the many small slats (1/8") layered up approach on coamings.
When they are layered up, they are strong enough, but more springy
than a coaming made from a single half inch thick piece of wood.
By the way, boat building is riddled with these nonlinear kinds of
relationships. This is why scaling a boat is not a straightforward
matter. See George Dyson's treatise on hydrodynamics of baidarkas
if you are interested in pursuing these kinds of matters in depth.
^ - ^ | Wolf
o o | wolfgang.brinck@hksystems.com
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