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Calculations
By:Sam McFadden
Date: 4/26/2002, 12:43 pm
In Response To: Re: I would like jump in here (Andreas)

: 1. Stiffness and strength: If you calculate the strength of the Cedar with
: fiberglass, you will see that the cedar has only a small influence on the
: strength. All bending loads are carried in tension and compression by the
: outer skin (fiberglass). Once you get close to the failure the bond to the
: cedar becomes important. If the fiberglass is able to seperate from the
: cedar core in compression, it will buckle and break, thus the laminate
: fails. If the bond is excellent you may see the layer in tension fail
: (depending on lay-up).

Andreas,

Then how do you explain the results of three-point bend testing (http://www.guillemot-kayaks.com/Building/Testing/index.html)? Within each data set, a single commom variable was grain orientation. If the cedar has a small influence on strength, then the grain orientation should have a small influence on strength. But test results show that grain orientation has a significant influence on stiffness and strength.

I'm currently in an experimental mechanics group at Sandia National Laboratories. Within the groups that we support, primarily solid mechanics modeling, a common phrase goes something like "experiment is trumps". Most of our results provide property input to, or verification of, modeling (calculations). If the models don't predict the experimental results, then the models are reworked.

I too have done calculations that don't match well with the data for glass/cedar/glass construction. I believe it is because of the lack of a good data base for mechanical properties that represent the way we use glass and epoxy - the stuff is simply not a stiff as we assume it is. Therefore, there is more load sharing than simple calculations suggest there is.

But lets keep in mind that one of the main themes of this discussion is that Mike would like to explore moving away from the glass/wood/glass sandwich model for kayaks to a wood-based structure model. So discussing the details of glass/cedar/glass construction does not address Mike's interest.

Sam

Experiments

Messages In This Thread

Launching: photos?
Mike Loriz -- 4/23/2002, 9:16 pm
Another pic
Mike Loriz -- 4/24/2002, 10:40 am
Newbie contruction review, hardwood difs
Mike Loriz -- 4/24/2002, 2:18 pm
Re: Newbie contruction review, hardwood difs
Sam McFadden -- 4/25/2002, 12:56 am
Re: Newbie contruction review, hardwood difs
Mike Loriz -- 4/25/2002, 9:17 am
Re: Newbie contruction review, hardwood difs
Sam McFadden -- 4/25/2002, 11:27 am
Re: Newbie contruction review, hardwood difs
Andy -- 4/27/2002, 11:09 pm
Re: Newbie contruction review, hardwood difs
Sam McFadden -- 4/28/2002, 9:52 pm
Re: Newbie contruction review, hardwood difs
Mike Loriz -- 4/25/2002, 1:07 pm
Re: Newbie contruction review, hardwood difs
Sam McFadden -- 4/25/2002, 11:39 pm
Re: Newbie contruction review, hardwood difs
Mike Loriz -- 4/26/2002, 10:15 pm
Other species
Sam McFadden -- 4/27/2002, 12:09 pm
Re: Other species
Mike Loriz -- 4/28/2002, 9:10 pm
Re: Other species
Sam McFadden -- 4/28/2002, 9:45 pm
Re: Other species *Pic*
Nick Schade - Guillemot Kayaks -- 4/29/2002, 9:14 am
Re: Other species
Sam McFadden -- 4/29/2002, 5:27 pm
Go with the old wood/canvas canoe model
Paul G. Jacobson -- 4/27/2002, 12:48 am
Re: Go with the old wood/canvas canoe model
Mike Loriz -- 4/28/2002, 8:49 pm
Re: All Wood
Nick Schade - Guillemot Kayaks -- 4/26/2002, 10:06 am
No angels, pins or dancing needed :)
Paul G. Jacobson -- 4/25/2002, 9:10 pm
Re: No angels, pins or dancing needed :)
Mike Loriz -- 4/26/2002, 10:04 pm
Re: No angels, pins or dancing needed :)
Sam McFadden -- 4/25/2002, 11:24 pm
I would like jump in here
David Hanson -- 4/25/2002, 4:51 pm
What about using 1/8" Red Elm for strong strips?
John Monfoe -- 4/26/2002, 7:22 am
Re: What about using 1/8" Red Elm for strong strip
Mike Loriz -- 4/26/2002, 9:42 pm
Re: What about using 1/8" Red Elm for strong strip
John Monfoe -- 4/27/2002, 6:17 am
Re: What about using 1/8" Red Elm for strong strip
David Hanson -- 4/26/2002, 11:44 am
Use both feet :)
Paul G. Jacobson -- 4/25/2002, 9:58 pm
Re: I would like jump in here
Mike Loriz -- 4/25/2002, 9:40 pm
Now we are getting somewhere
David Hanson -- 4/26/2002, 11:36 am
Re: Now we are getting somewhere
Mike Loriz -- 4/26/2002, 9:33 pm
Re: I would like jump in here
Andreas -- 4/26/2002, 10:44 am
Re: I would like jump in here
Mike Loriz -- 4/26/2002, 9:04 pm
Re: The Wood Matters *Pic*
Nick Schade - Guillemot Kayaks -- 4/26/2002, 12:48 pm
Its a bird its a plane its a .....?
!RUSS -- 4/26/2002, 5:34 pm
Re: Its a bird its a plane its a .....? *Pic*
Nick Schade - Guillemot Kayaks -- 4/28/2002, 11:55 am
Re: The Wood Matters - You are right
Andreas -- 4/26/2002, 2:47 pm
Re: Credit *Pic*
Nick Schade - Guillemot Kayaks -- 4/26/2002, 5:16 pm
Re: Credit
Andreas -- 4/26/2002, 6:16 pm
Re: Delamination
Nick Schade - Guillemot Kayaks -- 4/28/2002, 12:41 pm
Re: Delamination
Mike Loriz -- 4/28/2002, 10:43 pm
Re: Delamination
Sam McFadden -- 4/30/2002, 12:08 am
Re: Delamination
Mike Loriz -- 4/30/2002, 12:37 pm
Calculations
Sam McFadden -- 4/26/2002, 12:43 pm
Re: Calculations
Mike Loriz -- 4/26/2002, 9:19 pm
Re: Newbie - Not!
Chip Sandresky -- 4/24/2002, 3:05 pm
Re: Newbie - Not!
Mike Loriz -- 4/24/2002, 7:06 pm
Re: Newbie - Not!
Steve Frederick -- 4/24/2002, 10:22 pm
Re: Newbie - Not!
Mike Loriz -- 4/25/2002, 8:44 am
Re: Launching: photos?
Mike Loriz -- 4/24/2002, 10:35 am
Re: Launching: photos?
Nick Schade - Guillemot Kayaks -- 4/24/2002, 9:35 am
Re: Launching: photos?
Bobby Curtis -- 4/23/2002, 11:14 pm
Re: Launching: photos?
Mike Loriz -- 4/24/2002, 7:00 pm
Doh!!
Sam McFadden -- 4/23/2002, 11:01 pm
Re: Launching: photos?
daren neufeld -- 4/23/2002, 10:29 pm
Great!
Sam McFadden -- 4/23/2002, 10:55 pm
Re: Great!
Mike Loriz -- 4/24/2002, 6:57 pm
Re: Launching: photos?
John Schroeder -- 4/23/2002, 10:17 pm
Re: Launching: photos?
Ronnie -- 4/23/2002, 9:28 pm