Double layer ply vs single...

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Conrad
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Double layer ply vs single...

Post by Conrad » Mon Oct 08, 2018 11:05 am

Double layer ply vs single...

So the bottom of the flyer asks for 2 layers of 1/4 instead of 1 of 1/2. I know the question has been asked of some, but to get a fresh opinion, which is better? On the one hand, there are no single points of weakness in the hull as 1/4 is offset from the second, but on the other hand, there is no way to make sure there are no air gaps between the 2 layers of 1/4. Thoughts?
Keep your lines tight!

Conrad

Consider what God has done: Who can straighten what he has made crooked? Ecc 7:13 :)

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Bill Edmundson
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Re: Double layer ply vs single...

Post by Bill Edmundson » Mon Oct 08, 2018 11:28 am

The 1/2" will be very difficult to bend.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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Conrad
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Re: Double layer ply vs single...

Post by Conrad » Mon Oct 08, 2018 11:56 am

Bill Edmundson wrote:The 1/2" will be very difficult to bend.

Bill

Like the last flyers, would be half to the bend and then 1/4.
Keep your lines tight!

Conrad

Consider what God has done: Who can straighten what he has made crooked? Ecc 7:13 :)

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Bill Edmundson
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Re: Double layer ply vs single...

Post by Bill Edmundson » Mon Oct 08, 2018 1:31 pm

1/2" is 8 times harder to bend than 1/4".

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

PeterG
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Re: Double layer ply vs single...

Post by PeterG » Mon Oct 08, 2018 7:10 pm

To minimize the chance for voids between the layers of 1/4" plywood, you could try vacuum bagging the second layer on. Have a look at Bob Perkins' Biscayne 22 project: https://bperkins.wordpress.com/2017/11/ ... ayne-22-2/

You would pre-fit the second layer dry, then epoxy it in place, apply the vacuum bag materials and apply the vacuum. 14.7 pounds per square inches is a lot of force and makes sure you're getting a full bond, with excess squeezed out the edges.
Murphy's Law: Anything that can go wrong, will go wrong.
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Bob Perkins
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Re: Double layer ply vs single...

Post by Bob Perkins » Tue Oct 09, 2018 7:11 am

Nice to see my site is still getting used.

and agreed - If you want to be certain to have no voids - vacuum is the best way to do it..
Vacuum is the perfect clamp - 2000+ pounds of clamping pressure per square foot in the exact shape of your boat..
AND - if there is a void potential - the vacuum pulls out the air and glue is all that is left to fill it.

When I was laminating my boat - there was nearly nothing on the topic (for home use).. I'm certain its pretty well documented out there now..
Good luck!
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Bob Perkins

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Hercdrvr
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Re: Double layer ply vs single...

Post by Hercdrvr » Thu Oct 11, 2018 6:12 pm

How much are you going to weaken 1/2” plywood trying to bend it into shape? I don’t know much about the flats flyer shape but 1/2” ply isn’t going to yield much. 1/4 on top of 1/4 held with Poxygrip and some screws and it won’t be coming apart in our lifetime.
Matt B

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Bob Perkins
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Re: Double layer ply vs single...

Post by Bob Perkins » Thu Oct 11, 2018 8:03 pm

I looked at the picture of the boat..
The bottom is relatively flat - however - there is twist..
Twisting 1/2" plywood is going to be a pain... its going to put up a fight.. pulling on frames, etc as you get it into position..
just a thought.
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Bob Perkins

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https://bperkins.wordpress.com/

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