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Re: The Wood Matters - You are right
By:Andreas
Date: 4/26/2002, 2:47 pm
In Response To: Re: The Wood Matters *Pic* (Nick Schade - Guillemot Kayaks)

Hi Nick,

I have not run the actual numbers, but I believe your results without a question. The properties of the core become more important the thinner the glass layer(s). The wood next to the fiberglass (as far as possible from the center in a symmetric lay-up) contributes to the strength and overall stiffness. The thicker the glass the less the wood matters (and its orientation). Actually for impact it would be best to have the grain vertically in the sandwich. The slope in your test curves will be affected by the stiffness, thickness and location of the fiberglass as well as by the stiffness and thickness of the wood. As we know the modulus of wood varies from along the grain to perpendicular to the grain. For western red cedar the ratio of the modulus in grain direction to the modulus tangential to the growth rings is 0.055 (nearly the same for Walnut). This is why you are seeing in the significant difference in slopes, i.e. when testing the cross grain the deflection is mainly controlled by the glass, while when testing the along the grain you have a combination of wood and fiberglass controlling the stiffness.

The failure for these lay-ups is difficult to predict. Most of the variation will come from the quality of the bond to the wood and the distance of the fiberglass to the wood. Vacuum bagged samples will give you typically more consistant results. In addition any distortion in the glass will affect the results significantly.

Nevertheless the impact consideration is still difficult to predict.

Great work Nick.

Note that testing shows a significant grain dependance on both strength and
: stiffness of strip built layups. In the graphs below of force vs
: deflection of a sample of 1/4" thick cedar with 6 oz glass, two
: layers on one side, one on the other, samples C1 - C4 are bent with the
: grain and C5 - C8 are across the grain.

: While this grain dependance does not necessarily prove that the wood
: contributes strength to the layup, it does demonstrate that it the very
: least "influences" the strength.

: I think it is a mistake to treat the wood as just-another-core with a
: response just like a homogeneous foam. Wood has a toughness and strength
: you just don't find in man-made composites.

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