How much 'slack' in 6" * 22" solid wood panel

[mark mcfarlane]

I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

421095

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,

[Mel Fulks]

Yeah, 1/8th is plenty for such good wood and small space.

[Lee Schierer]

The length isn't going to change dimensions any appreciable amount.

According to the USDA FOrestry products you can expect seasonal moisture changes in the ranges shown on this map.421106

[Jamie Buxton]

Lee, is that map showing EMC indoors, or outdoors?

[Steve Demuth]

I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

421095

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,

On the time scale wood cares about, humidity barely changes in Houston. See here (https://www.weather-us.com/en/texas-usa/houston-climate#humidity_relative). You basically have a 4% RH change over the year. So, as long as your piece stays outside, given QS White Oak is a very stable wood to start with, you're going to see very little movement at all.

And even if you were in a place where here are 15% plus RH swings, with your materials and dimensions you'd be OKith the 1/8" for width. Length isn't going to change measurably at all.

[Lee Schierer]

I believe it is out doors, but here is a link that is definitely for outdoors (https://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf)

[Steve Demuth]

I believe it is out doors, but here is a link that is definitely for outdoors (https://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf)

Yep. I was assuming that when the OP wrote he was building "a small outdoor shelf," that it was permanently outdoors, under a roof. Obviously if it's indoors or moving back and forth, it's a completely different story.

[mark mcfarlane]

Permanently outdoors, at least during my lifetime.

[Bill Dufour]

My theory on fitups like this is I fit the panel exactly to fit. I can normally use the molding cuts on the outside to get the dimensions. Then once it is done and verified I cut one blade width off on two sides. So about 1/8" off in both dimensions.
Bil lD

[Brian Tymchak]

With the internal panel floating in the frame, regardless of humidity change, I would expect essentially no seasonal movement in the whole panel.

[mark mcfarlane]

Thanks everyone for sharing your experience on this question.

Sorry I have been slow to respond. I've been really sick with some severe flu-like symptoms for a couple days. I actually pulled muscles in my back due to the most violent vomiting I have ever witnessed. Hopefully I'll be back in the shop in a couple days after I rehydrate and get some nourishment onboard.

[mark mcfarlane]

I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

421095

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,

I finished milling all the wood and built the frame today. I put in my prototype panels with 1/8" of L-R play.

The sides are made from two panels, so at least for now (before finish is applied) the two panels slide independently so they can potentially leave a gap (or a crooked gap) in the middle as per the attached picture below. Not really what I want. What should I do? Order some 1/4" Space Balls (https://www.rockler.com/space-balls-raised-panel-door-spacers) and cut them in half ?

421813

[mark mcfarlane]

Thanks everyone for the help on this project. I ended up using 1/4" space balls from Woodcraft, and cut them in half so they were 1/8".

Here's the finished project. Turned out to be too nice to put outdoors, as originally planned :).


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