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Laminating cedar to hold rocker

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El_Norte_Adventures
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Laminating cedar to hold rocker

Postby El_Norte_Adventures » Sat Jun 10, 2017 3:47 pm

Hey guys,

My last build was a foil board using two layers of cedar strips laminated on a make-shift rocker table. The rocker held really well with very little springback.

I suspect the glue between the strips would be enough to hold the rocker in a single layer lamination, but anyone tried and can comment? Also did you use a titebond type product or epoxy?

Cheers,

Greg
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BWD
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Re: Laminating cedar to hold rocker

Postby BWD » Sat Jun 10, 2017 8:47 pm

Built a twin top that way seven years ago, still going strong. Minimal spring back from epoxy gluing 2 layers of approx 7mm strips western red cedar. Actually has a hair too much rocker, really. Top layer doesn't go all the way to tips. As long as you leave it on jig until glue is fully cured, should be great.

And that looks great BTW.

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downunder
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Re: Laminating cedar to hold rocker

Postby downunder » Mon Jun 12, 2017 9:37 am

El_Norte_Adventures wrote:
Sat Jun 10, 2017 3:47 pm
Hey guys,

My last build was a foil board using two layers of cedar strips laminated on a make-shift rocker table. The rocker held really well with very little springback.

I suspect the glue between the strips would be enough to hold the rocker in a single layer lamination, but anyone tried and can comment? Also did you use a titebond type product or epoxy?

Cheers,

Greg
No, and yes. Epoxy.

BWD, this is double layer of yours, OP asks for single.

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jeromeL
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Re: Laminating cedar to hold rocker

Postby jeromeL » Mon Jun 12, 2017 2:53 pm

Looks nice, Hydrofoil build?

BWD
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Re: Laminating cedar to hold rocker

Postby BWD » Mon Jun 12, 2017 6:13 pm

Ahh. :o oops

I read it as "lamination" = 2 things or 2+ layers of something glued together.
So I got confused semantically there.
I am not very confident that the Edge Gluing holding the strips together would hold rocker.
The thicker the strips, of course, the more area to help hold shape, but it be hard to glue the strips together on a sufficiently curved jig. They would still try to straighten out again.
Even using 18oz or so of glass each side, with a one-layer flat blank of cedar ~10-12 mm or so max thickness, you will be fighting spring back and may expect up 50-75% of jig rocker to be lost. This is on the USA, western red cedar and eastern white cedar I get locally. It's kind of stiff. Your mileage may vary with species, location etc. in general though cedar is stiff.

To figure out how to get your rocker, make test strips - make blank extra wide and cut a couple of 50-100mm wide strips off the side. Laminate one with your planned glass schedule in your jig and observe how much it springs back. Adjust jig or lam schedule accordingly and repeat. My experience has been in low rocker sections doubling the desired rocker is a good starting point, but for a directional needing nose "flip" or a wake style hi rocker twin tip you'll have to go higher in area of higher curvature, maybe 3x if your blank will take it.
So you may have to build a jig with a curve that is not looking linearly related to the end rocker of the board. Or you could say it relates to it with a nonconstant slope.

Sorry I was confused there.

El_Norte_Adventures
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Re: Laminating cedar to hold rocker

Postby El_Norte_Adventures » Mon Jun 12, 2017 9:14 pm

Thanks for the info BWD, I will stick with two layers of cedar for my next build to keep the rocker table design easy after reading that that downunder has tried a single layer and it didn't work out. Trying to save a bit of time and stress during the glue up, but I would rather have a bit of a thicker core anyway so that is fine.

Appreciate you sharing your experience downunder and saving me a failed experiment! Why do you opt for epoxy over an expanding glue? I used epoxy on my build above because I had it on hand and it has a longish working time, but I had to go back and fill a bunch of tiny cracks in the lamination from my imperfect planing/jointing/clamping. I was considering something with some expansion this time around to save that hassle and ensure all the out of sight gaps are filled.

Thanks Jerome! It is a hydrofoil board, but no plans to build a hydrofoil any time soon - I'll leave that to those better qualified!

Greg

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downunder
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Re: Laminating cedar to hold rocker

Postby downunder » Tue Jun 13, 2017 4:50 am

Greg,

because the only board ever delaminated on me and quite spectacularly I must say (forensics still pending :), it was glued with the titebond III with double layer wood.

I would suggest to have a look at my "new year build" from here:
http://kiteforum.com/viewtopic.php?f=107&t=2387451

This are the one layer strips bonded with epoxy. The trick is to have them almost loose before the top glassing, so I sort of just glued the tips slightly. It also helps to have a bit of carbon to hold the rocker, and UNI FG as you can see. I did not 'push' any epoxy between the strips, the vacuum did that plus gravity.
So, the 'plain' wood will definitely sprig back heaps, to almost flat.

D.

El_Norte_Adventures
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Local Beach: Vancouver Island
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Gear: LP Foil with low aspect wing, Ocean Rodeo Jester, OR Prodigys and Flite
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Re: Laminating cedar to hold rocker

Postby El_Norte_Adventures » Thu Jun 15, 2017 12:24 am

Makes sense, I'll stick with two layers then as I am not using a vac bag.


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