Running torsion box through planer

Mismarked

Mismarked

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Oct 8, 2014
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I am doing a floating shelf using a torsion box thing.  Bottom skin is flat.  Is it a terrible idea to run it through the planer before gluing on the top skin?  It is 1/4 inch ply if it makes any difference.
 

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It will probably explode. [scared] To much open space between the parts.
 
If you have access to a drum sander and sneak up on it in small increments that would work better than a planer.
 
Yeah, I think the planer is a bad idea. You probably won't have much of a torsion box left. Knives are bound to grab those cross piece top edges. I envision lots of splintering.

Seth
 
Figured that was right, but sure seemed tempting.  Don't have access to a drum sander.  Maybe I will try a straight edge and hand plane and see if I can at least knock down the high spots.
 
Give it a go.

The short cross pieces are the only concern. They will likely get knocked over but as long as they end up below the long strips (don't interfere with the bond between long strips and skin) you're okay.

If you want to you can grind the tops of the short strips (right angle grinder) to be sure the cutter head rides above them, or wait and see if you need to do that after.

In the grand scheme of torsion boxes the short strips are only needed to keep the long strips upright. They don't need to be glued to the skin.
 
"In the grand scheme of torsion boxes the short strips are only needed to keep the long strips upright."

That makes me wonder if I used way too many short pieces.  It is very light and very stiff even without the other side skinned, but if I build something larger, like a torsion box miter saw stand or workbench, using thicker materials, I would want to avoid unnecessary weight by having too many short strips.

 
Mismarked said:
"In the grand scheme of torsion boxes the short strips are only needed to keep the long strips upright."

That makes me wonder if I used way too many short pieces.  It is very light and very stiff even without the other side skinned, but if I build something larger, like a torsion box miter saw stand or workbench, using thicker materials, I would want to avoid unnecessary weight by having too many short strips.
Click to expand...

The shorts are only needed to keep the long strips upright, but that is a very important job, especially with relatively wiggly stuff like 1/4" ply. If the long strip gets crooked it's likely to produce high spots that would jeopardize adhesion of the skin.

Check out Sing Panels. They have it down. They use thin vertical grain strips for maximum compression resistance and minimum dead weight with foam blocks to support and regulate the distribution of the strips. I'd like to know how they manufacture the blocks. I guess a hot wire cutter to avoid the foam beads...

Scroll down to the bottom of that page to see a very interesting panel.
 
Funny, I also had pulled up info on the Sing Panels when I did a Google search, and it took me to something called www.lightweightuniversity.com.
 
Mismarked said:
Funny, I also had pulled up info on the Sing Panels when I did a Google search, and it took me to something called www.lightweightuniversity.com.
Click to expand...

I do think Sing has their version of the tech down but the vocabulary is pretty loose. In some posts they call the panels "honeycomb". Not.

To compensate for their somewhat remote location they've done a pretty good job of populating the internet with links to their product.
 
I would do it with 4 things: a very sharp block plane, a light touch, a straight edge and patients.
 
FWIW...if this were my project, I'd run it through the planer. The most important part is to just lean on it by a max .005"-.010" per cut, just a whisper of a cut. Less is more in this application. Especially the first cut because that's where you're leveling the surface. Just take it easy, a hair thickness at a time and you'll be ok. The longitudinal strips are fine it's the perpendicular members that may become a problem. Then again, the perpendicular members are not the major structural elements for this shelf, it's the horizontal members that support the skin.
 
I think it would be okay to use the thickness planer provided you take very light passes. If you are concerned with tear out, you could run a chamfer bit on all the trailing edges.
 
Before I had a big drum sander I would take my stuff to my hardwood supplier that is also a staircase building. He would charge $5 per minute of sanding, that panel would take about 2 minutes. In reality, he never once charged me. Check out whoever builds cabinets in your area and ask what they would charge you - it would probably be free. Slip the guy running the machine $10 and you have a sanding source for life.
 
I agree specially since it's so narrow....even someone with a super-max or something
 
It appears the consensus is that a drum sander would be the right tool and that a hand plane would also work, but there is no clear consensus about what would happen on the planer, and no one reported having tried it. 
    At the same time, there was no suggestion that light passes would be dangerous or would damage the planer like trying to run an end grain cutting board through it.
    In light of the altruistic nature of the FOG forum (and lack of ready access to a drum sander), I feel compelled to try it and report the results.  If it explodes, at least we will have a little more information for future use and I won't be set back that much.
    Will try this tomorrow and report back, hopefully with a video from both sides.
 
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