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New 1/4" Birch Plywood Project

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daspi
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New 1/4" Birch Plywood Project

Postby daspi » Tue Jun 24, 2014 2:32 pm

I am planning on building another light wind plywood board. Simplicity and function is they main focus. Board size ether 142x43 (Door) or 150x41 (Like the Slingshot Glide).

My last couple of boards I've built with 1/2" Sandeply from HD.
http://www.homedepot.com/p/Unbranded-12 ... /100017950
This worked out great but thought I'm going to try something different after reading other peoples ply projects.

Now I am thinking of getting 1/4" Birch plywood and glue two layers together with the top layer about 2" shorter and narrower.
http://www.homedepot.com/p/Unbranded-1- ... /100092485
Finish will be a few layers of Spar Urethane. Not planning on any glass layup.

Here is my concern, the 1/4" birch is actually only 0.203" thick. Will two layers of it be strong enough? Will it be too flexible and snap too easily? If I would add a 3rd layer under footstraps I end up heavier than using the 1/2" ply and would defeat the purpose.

Has anybody used 1/4" birch in two layers with only Spar Urethane finish? Was it strong enough?

Thank you for any input.

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Re: New 1/4" Birch Plywood Project

Postby plummet » Tue Jun 24, 2014 8:40 pm

My call. 2 layers is too fat. Use one layer and some triaxle glass top and bottom.

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edt
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Re: New 1/4" Birch Plywood Project

Postby edt » Tue Jun 24, 2014 8:43 pm

3/8th baltic birch is equivalent in strength to about 3/4 inch of the garbage home depot plywood or equal to about 1/2 inch of some decent ab douglas fir ply. remember baltic birch is not only stronger it is denser and heavier than cheap plywood. two layers of 1/4 will be way too heavy, either 1 layer of 1/4 birch with glass or 1 layer of 3/8th (i think that's 9mm) with spar varnish

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daspi
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and lots of other junk kites in the shed
Cabrinha Ace
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Re: New 1/4" Birch Plywood Project

Postby daspi » Fri Jun 27, 2014 7:32 pm

If you look at the 1/4", the actual measurement is 0.203" and glued together = 0.406" or 10.31mm.

I agree that a double layer is too strong if top and bottom are the same size but if the top is cut smaller like I mentioned? I am actually worried that the part around the edges and tips is going to be too weak or flexible. I think the overall stiffness can be controlled by making to top layer smaller accordingly. I'm asking again, has anybody used the 1/4 birch in the configuration I described with just spar urethane finish?

I do not intend to use glass. Simplicity is my goal and use only as much ply as needed to acheefe sufficient strength and keep weight down as much as possible.

The sandeply board at 1/2" routed down around the edges worked super sweet. I was just wondering if the 1/4 birch approach offered similar success for any of you. See my previous project here:
viewtopic.php?t=2364963
I want to rebuild this board and just collecting feedback if I should change to 1/4 birch instead of the 1/2 sandeply that I used previously.

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edt
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Re: New 1/4" Birch Plywood Project

Postby edt » Fri Jun 27, 2014 8:05 pm

Go for it. I don't think you want three layers that's too much and one layer is not enough. Two layers is going to be heavy but will work, can't say exactly how much cutout you want. baltic birch is about twice as strong as cheap plywood, when you get some you'll see.

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daspi
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and lots of other junk kites in the shed
Cabrinha Ace
RRD Poison
North Jaime
RRD X5 132cm
various Plywood boards
Space Pickle
Wipika surfboard (the old silver one)
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Re: New 1/4" Birch Plywood Project

Postby daspi » Fri Jun 27, 2014 8:18 pm

edt, do you consider the Sandeply the cheap kind a wood that is softer?

I am just nervous about the thin layer around the outline being just 1/4".

ONE built some beautiful doors but he used two layers of 1/4 and glass.
viewtopic.php?f=107&t=2365401

Just to understand what I have previously built. Have a look at the pictures, this was my second board that I've build with the same sandeply 1/2" as the Plywood Door in the link in my previous post. The only difference is that I used a belt sander to take off material to make it thinner around the outline. Soaked one side with water for a bit and put some wood under the tips and weight in the center for a couple of days. Ended up with a little bit of rocker. Size 138x43cm. Nice board for light wind.

Now want to do another Door... might just do Sandeply again unless somebody convinces me to go with the 1/4" birch?
DSC02192 (Medium).JPG

DSC02193 (Medium).JPG

DSC02194 (Medium).JPG

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edt
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Re: New 1/4" Birch Plywood Project

Postby edt » Fri Jun 27, 2014 10:00 pm

i cant comment on sandyply but all the wood I have bought from home depot has been worthless. It's possible sandyply might be slightly less worthless the rest of what they sell at home depot. You have to go to an actual lumber yard to get decent wood. I noticed home depot sells something they call "birch" I have no idea what it is. Probably a soft plywood with a thin birch veneer painted on. a 1/4 sheet of baltic birch should be 5 ply, 3/8 should be 7 ply and 3/4 inch baltic birch should be 13 ply and every ply should be exactly equal in size.


I think you should just go with the sandyply again unless you are serious about putting quality wood on your boards it will cost a lot more.

beautiful board btw

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daspi
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Posts: 55
Joined: Fri Jun 11, 2010 1:55 am
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Local Beach: Lynn - Nahant Long Beach, Revere Beach, Dog Beach
Favorite Beaches: the ones I can get to within 10-15 minutes
Gear: Core XR4 12m, 9m, 7m
and lots of other junk kites in the shed
Cabrinha Ace
RRD Poison
North Jaime
RRD X5 132cm
various Plywood boards
Space Pickle
Wipika surfboard (the old silver one)
Brand Affiliation: None

Re: New 1/4" Birch Plywood Project

Postby daspi » Fri Jun 27, 2014 10:47 pm

edt, ok now I understand. You are correct, the HD birch in 1/4" has only a veneer on top and bottom and a one layer filler in between. 5 ply sure will give it more strength but it will be a lot heavier too I assume. So it is ether going to be cheap and dirty with Sandeply or source some quality 5 ply birch. The HD birch is now out of the question, thanks.

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edt
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Re: New 1/4" Birch Plywood Project

Postby edt » Fri Jun 27, 2014 11:05 pm

daspi wrote:edt, ok now I understand. You are correct, the HD birch in 1/4" has only a veneer on top and bottom and a one layer filler in between. 5 ply sure will give it more strength but it will be a lot heavier too I assume. So it is ether going to be cheap and dirty with Sandeply or source some quality 5 ply birch. The HD birch is now out of the question, thanks.


close call there glad we caught it

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Re: New 1/4" Birch Plywood Project

Postby UKRob » Sun Jun 29, 2014 4:17 pm

edt wrote:
daspi wrote:edt, ok now I understand. You are correct, the HD birch in 1/4" has only a veneer on top and bottom and a one layer filler in between. 5 ply sure will give it more strength but it will be a lot heavier too I assume. So it is ether going to be cheap and dirty with Sandeply or source some quality 5 ply birch. The HD birch is now out of the question, thanks.


close call there glad we caught it


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