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New 1/4" Birch Plywood Project

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SweetDoug
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Re: New 1/4" Birch Plywood Project

Postby SweetDoug » Tue Jul 08, 2014 2:15 am

'
'
'
I think you'll be too heavy with the dual 1/4". I used 1/8th ply, double layer and it worked well for me.

225 lbs. Lots of flex.

Here's the thread on the build.

viewtopic.php?f=107&t=2381313&start=10

SweetDoug

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daspi
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Re: New 1/4" Birch Plywood Project

Postby daspi » Tue Aug 12, 2014 12:10 pm

Well thanks SD on the tip to use 1/8".

Wow 1/8" double layer is enough? Does it even hold shape this thin? Or did you use glass on top? Also what quality wood did you get?

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bay surfer
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Re: New 1/4" Birch Plywood Project

Postby bay surfer » Tue Aug 12, 2014 2:46 pm

No, 2 layers of 1/8 in birch ply are not strong enough, ya have to glass the top and bottom and middle....you lose any wt advantage. 3 sandwiched 1/8ply layers are just strong enough with poly on the outside, perfect for mowing the lawn riding, but high jumppin flying, THEY WILL TEND TO BREAK. BUT, I do find if you use good 1 1/4in AC 3 ply sheet and 1 1/8 birch 3 ply sheet. Makes for a relative Boom proof LIGHT flexible board, go figure.

zfennell
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Re: New 1/4" Birch Plywood Project

Postby zfennell » Tue Aug 12, 2014 6:28 pm

lots of useful observations to take advantage of.

if still not sure, a bit of experimenting during your next visit to HD will add some hard numbers to all of the speculation. (or you could look them up from someone like 'plywood association' of wherever)
compare all your potential candidate materials.

one by one:
prop up any of your favorite choices between two carts.
toss a 50lb bag of cement in the middle
measure deflection, length width and thickness.

Deflection = wL^3/(48 E*I)
google 'beam deflection formula' for 3-point bending

the resulting numbers will be a good way to compare and give you enough to predict deflection for any of your design iterations.

It may also convince you that the cheepest and lightest crap you can find will be tough to beat with 1 or 2 layes of 4oz glass.
imo,
-bill

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daspi
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Joined: Fri Jun 11, 2010 1:55 am
Kiting since: 2010
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 » Wed May 06, 2015 6:05 pm

Finally got around to try the 1/4 Baltic Birch ply. For simplicity I just got a 2.5ft x 5ft panel and cut to size to make two layers. Almost done. Last few coats of spar urethane...
2015-05-02 16.35.59.jpg

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daspi
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Posts: 57
Joined: Fri Jun 11, 2010 1:55 am
Kiting since: 2010
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 May 08, 2015 1:58 pm

It retained the rocker better than I expected. Gluing up two layers seems to be the way to go for creating a controlled rocker. Now I think I've got myself a bit much rocker for a light wind board. I've tested it last night and it rides super sweet. More comfy then the old one of the same shape with less rocker. Now I have to find out if I get the same low end out of it. For now I am very pleased with the result.
2015-05-07 16.33.20.jpg

2015-05-07 16.34.27.jpg

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daspi
Medium Poster
Posts: 57
Joined: Fri Jun 11, 2010 1:55 am
Kiting since: 2010
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 » Mon May 11, 2015 12:43 pm

After two sessions on it I have to say I am very pleased with the riding performance. The additional rocker makes this board way more smooth than the same outline with flatter rocker. No surprise here I guess.

The Baltic Birch ply gives this board a much better, snappier pop for jumps. I still think I lost a bit on the ultra low end but really not much. Huge improvement in riding down little waves, feels nice and loose. I was slashing them like on my smaller boards. And all that with a 16m kite, light wind and some ply under my feet. I am thrilled!

B/BB from now on for me. Thank you for the encouragement to use better quality plywood.

The original build on a few posts back was with Sande Ply, now re-built with Baltic Birch Plywood. I have to see how the thinner rails and the glued up layers of 1/4" sheets will hold up.


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