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Forum topic by SpartyOn posted 07-24-2018 02:16 PM 849 views 0 times favorited 17 replies Add to Favorites Watch
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SpartyOn

47 posts in 2708 days


07-24-2018 02:16 PM

Question for you cabinet experts. Will a 40” wide, 20” deep shelf made out of 3/4” Baltic Birch Ply, sag over time? It seems pretty stiff and stable but don’t know if that will change over time. I know if it was a fixed shelf I could brace it such that it won’t sag. However, I’m making a cabinet for a friend that wants this shelf to be adjustable.

Thanks for any guidance!


17 replies so far

View Bill White's profile

Bill White

5234 posts in 4522 days


#1 posted 07-24-2018 02:30 PM

40” is pushing the limit. I try to keep adjustable shelves no longer than 36”.

-- [email protected]

View nkawtg's profile

nkawtg

292 posts in 1813 days


#2 posted 07-24-2018 02:32 PM

I refer you to the “Sagulator”

http://www.woodbin.com/calcs/sagulator/

View Lazyman's profile

Lazyman

4180 posts in 1949 days


#3 posted 07-24-2018 02:33 PM

A shelf 20” deep cries out for some heavy stuff on it so I would want to add support. I assume you are going to cover the edge plies? Perhaps you could use a 1-1.25” wide strip of solid wood along the front edge to add some stiffness. That might also allow you hide another strip on the bottom as well make it even more rigid, depending upon how high it is of course.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View BurlyBob's profile

BurlyBob

6770 posts in 2827 days


#4 posted 07-24-2018 03:27 PM

I agree with Bill and Nathan. I’m thinking it might work with a serious strip across the front like Nathan suggest. Also besides shelf pins on the sides, shelf pins in 2 locations on the back side.

View SpartyOn's profile

SpartyOn

47 posts in 2708 days


#5 posted 07-24-2018 08:55 PM



I refer you to the “Sagulator”

http://www.woodbin.com/calcs/sagulator/

- nkawtg


That’s a very helpful site. Thanks!

View SpartyOn's profile

SpartyOn

47 posts in 2708 days


#6 posted 07-24-2018 08:57 PM



A shelf 20” deep cries out for some heavy stuff on it so I would want to add support. I assume you are going to cover the edge plies? Perhaps you could use a 1-1.25” wide strip of solid wood along the front edge to add some stiffness. That might also allow you hide another strip on the bottom as well make it even more rigid, depending upon how high it is of course.

- Lazyman


I do plan on adding a hardwood edge. Didn’t think about how that will help. Great idea an making a bit wider and hiding an additional strip on the bottom. Thank you!

View SpartyOn's profile

SpartyOn

47 posts in 2708 days


#7 posted 07-24-2018 08:58 PM



I agree with Bill and Nathan. I m thinking it might work with a serious strip across the front like Nathan suggest. Also besides shelf pins on the sides, shelf pins in 2 locations on the back side.

- BurlyBob

Another good thought! Thank you!

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SpartyOn

47 posts in 2708 days


#8 posted 07-24-2018 08:59 PM



40” is pushing the limit. I try to keep adjustable shelves no longer than 36”.

- Bill White

Good input! Thanks, Bill.

View DS's profile

DS

3345 posts in 2982 days


#9 posted 07-24-2018 09:16 PM

View AandCstyle's profile

AandCstyle

3223 posts in 2819 days


#10 posted 07-24-2018 09:18 PM

Sparty, you can also put a lip on the back edge if necessary for the added strength or ONLY put a lip on the back if you want the design to appear more open or lighter. FWIW

-- Art

View Redoak49's profile

Redoak49

4273 posts in 2550 days


#11 posted 07-24-2018 10:19 PM

Yes, a front and back edge strip. I over build everything and would cut at least one dado in the bottom and add a strip in the middle.

I would ask what was going on the shelf and over build it.

View woodbutcherbynight's profile

woodbutcherbynight

5975 posts in 2971 days


#12 posted 07-25-2018 01:21 AM

Definitely want to know what is going on the shelf. Then double that, cause overbuilding is okay!

-- Live to tell the stories, they sound better that way.

View Richard's profile

Richard

11307 posts in 3594 days


#13 posted 07-25-2018 01:45 AM



Sparty, you can also put a lip on the back edge if necessary for the added strength or ONLY put a lip on the back if you want the design to appear more open or lighter. FWIW

- AandCstyle

This is Okay also!

Rick

-- Richard (Ontario, CANADA)

View PPK's profile

PPK

1578 posts in 1371 days


#14 posted 07-25-2018 02:00 PM

That’s a big shelf. I don’t know that I’d completely trust the “sagulator”... it’s pretty cool… but awful scientific for something very unpredictable like WOOD! It’s kind of like trying to predict the springback on a steam bent peice of wood. You can calculate till you go cross eyed, and depending on the specific board you bend, it will NOT comply with all that calculating :-)

Anyway, I’ve built lots of big cabinet shelves, and if you put edging on the F and B, you’ll be fine. Baltic Birch is a very good plywood. If you were using particle board or MDF it’d be an entirely different story though!

-- Pete

View SpartyOn's profile

SpartyOn

47 posts in 2708 days


#15 posted 07-25-2018 05:26 PM

Thanks everyone for the help! I knew I could count on this group!

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