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Re: Skin-on-Frame: stringer fastening
By:Bill Hamm
Date: 9/14/2012, 9:47 am
In Response To: Re: Skin-on-Frame: stringer fastening (ancient kayaker)

: I agree a test is the way to go, but I am not sure what would
: constitute an appropriate test. I have made joints with
: different adhesives and tested them to destruction to determine
: how best to make such joints. That seems appropriate for an
: all-wood boat in which failure of a joint or wood leads to
: potential failure of the boat. But I think the force
: interactions in a skin boat are more complex than for a rigid
: boat.

: A skin boat can flex within the limits of the elasticity of the
: skin. The skin is an important structural component that
: provides much of the boat's strength, so the frame assembly
: itself needs to be able to flex to an equivalent degree. If the
: frame or any part of it is too stiff it will take a
: disproportionate share of the load and will soon fail. That is
: part of the argument in favour of using lashed joints. But I
: think such a test of a lashed joint would yield to such a degree
: as to render the test meaningless.

: In the case of the Platt Monford Geodesic Aerolite designs, I have
: always thought the main value of the diagonal roving was to
: stiffen the frame to prevent distortion applying the skin, but
: PM's purpose may have been to obtain a stiff frame to relieve
: the skin of stress and/or to yield a stiffer boat which some
: people prefer. The roving works by converting bending forces
: into compressive forces which the light frame components are
: better able to withstand. On the other hand, the people who long
: placed their trust and lives in skin boats in the far North
: never used anything resembling diagonal roving.

: This doesn't help us to decide how best to assemble a frame for a
: skin boat. I suppose it's good that we can at least ask the
: question; current practice needs to be questioned now and then.
: When theory cannot predict the best course of action all that is
: left is the experience of many boats and trial-and-error.

At minimum there is hundreds of years of testing of lashed frames, it's worked for a very long time. Btw, need to look at the method of lashing, done correctly there really isn't a huge amount of force put on your hands/fingers. They are basically lashed snug then the lashing is lashed again to tighten the original lashing. Painting the lashing with epoxy after it's done will prevent any loosening, makes for an amazingly strong joint.

Bill H.

Messages In This Thread

Skin-on-Frame: stringer fastening
Peter Lord -- 9/11/2012, 3:45 am
Re: Skin-on-Frame: stringer fastening
Bill Hamm -- 9/12/2012, 1:57 am
Re: Skin-on-Frame: stringer fastening
Peter Lord -- 9/13/2012, 10:29 am
Re: Skin-on-Frame: stringer fastening
ancient kayaker -- 9/13/2012, 6:04 pm
Re: Skin-on-Frame: stringer fastening
Marc Upchurch -- 9/13/2012, 6:34 pm
Re: Skin-on-Frame: stringer fastening
ancient kayaker -- 9/13/2012, 11:41 pm
Re: Skin-on-Frame: stringer fastening
Bill Hamm -- 9/14/2012, 9:47 am
Re: Skin-on-Frame: stringer fastening
wysedav -- 9/14/2012, 10:16 am
Re: Skin-on-Frame: stringer fastening
wysedav -- 9/13/2012, 11:53 pm
Re: Skin-on-Frame: stringer fastening
Marc Upchurch -- 9/14/2012, 1:17 am
Re: Skin-on-Frame: stringer fastening
Peter Lord -- 9/14/2012, 5:43 am
Re: Skin-on-Frame: stringer fastening
wysedav -- 9/14/2012, 8:43 am
Re: Skin-on-Frame: stringer fastening
Bill Hamm -- 9/14/2012, 9:51 am
Re: Skin-on-Frame: stringer fastening
Bill Hamm -- 9/14/2012, 9:43 am
Re: Skin-on-Frame: stringer fastening
Bill Hamm -- 9/14/2012, 9:42 am
Re: Skin-on-Frame: stringer fastening
Niven Paine -- 9/14/2012, 4:51 pm
Re: Skin-on-Frame: stringer fastening
Marc Upchurch -- 9/14/2012, 10:31 pm
Re: Skin-on-Frame: stringer fastening
Niven Paine -- 9/15/2012, 4:30 pm
Re: Skin-on-Frame: stringer fastening
Marc Upchurch -- 9/15/2012, 6:16 pm
Re: Skin-on-Frame: stringer fastening
Niven Paine -- 9/15/2012, 7:40 pm