Darryl Keil Last Activity 2024-10-10 3:42 PM
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Stan

Posts: 2

Joined: 2005-08-10
Location: Decatur, AL

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Subject : Honeycomb Core Veneer Question
Posted : 2005-08-10 9:38 AM
Post #32326
I am planning to build a conference table and I am considering the honeycomb cardboard as the core. If I go this way, do I still need to veneer the top and bottom of the top MDF skin? You normally do this when using only MDF to balance the stresses, but I am wondering about the need for it on a bottom skin, honeycomb, top skin, veneer sandwich. Also, how thick should the MDF be? 1/4"? 1/2"? The table will be a boat shaped table, about 16' long and roughly 4' wide at the center. I plan to use solid wood to trim out the edge.

Thanks in advance!

Stan


 
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Andrew

 
Subject : RE: Honeycomb Core Veneer Question
Posted : 2005-08-10 5:48 PM
Post #32330 - In reply to #32326
Stan, that's a really good question. I'm about to make some large cabinet doors that I want to keep as light as possible, so I knew solid MDF was out of the question. I was planning on veneering only one side of each skin, but now that you mention it, I don't know whether the glue line would be rigid enough to keep things balanced. Instead of the honeycomb cardboard, I am thinking about using that high density blue foam insulation instead, since it's cheap and easy to find. I made up a test panel and it seems quite strong, so foam might work for you too, unless someone out there has a reason why it shouldn't be used.

Andrew


 
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Darryl Keil

Posts: 1453

Joined: 2003-05-22
Location: Maine

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Subject : RE: Honeycomb Core Veneer Question
Posted : 2005-08-11 8:57 AM
Post #32337 - In reply to #32326
Stan and Andrew,

You are fine veneering only the outside of each skin. If you do it this way and are veneering the skins first I would try to do the honeycomb lay up as soon as you can after veneering the skins as they will begin to warp. The other option is to veneer the completed panel afterwards. I use 1/4" in general. You can use 1/8" but it tends to have a hollow sound when you tap it. I dont see any practical reason to go over 1/4", it just adds weight.

Foam does work to create a light panel but does not give you the same level of torsion box effect as honeycomb cores will.

Sincerely
Darryl Keil


 
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Stan

Posts: 2

Joined: 2005-08-10
Location: Decatur, AL

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Subject : RE: Honeycomb Core Veneer Question
Posted : 2005-08-11 7:44 PM
Post #32343 - In reply to #32337
Darryl,

Thanks for the info. It is amazing that you can get the strength and rigidity from 1/4" mdf and the cardboard substrate. Any thoughts on the thickness of the cardboard or is that purely an asthetic choice?

Thanks,

Stan


 
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Darryl Keil

Posts: 1453

Joined: 2003-05-22
Location: Maine

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Subject : RE: Honeycomb Core Veneer Question
Posted : 2005-08-12 9:20 AM
Post #32344 - In reply to #32343
Stan,

Thicker the honeycomb stronger the panel.

Sincerely
Darryl Keil


 
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Stanmo

 
Subject : RE: Honeycomb Core Veneer Question
Posted : 2005-08-21 10:55 PM
Post #32359 - In reply to #32344
Darryl,

When using the cardboard substrate, how much vacuum do you apply when gluing up the top skin, bottom skin, and the cardoard? Do you have to consider the air trapped in all of the individual honeycombs?

Thanks,

Stan


 
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Darryl Keil

Posts: 1453

Joined: 2003-05-22
Location: Maine

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Subject : RE: Honeycomb Core Veneer Question
Posted : 2005-08-22 10:26 AM
Post #32360 - In reply to #32359
Stan,

You don't really need to be concerned with the air in the honeycomb cells. You do need to turn the vacuum down to around 15HG when laying up a honeycomb panel. Once the panel is pressed up and fully cured you can then veneer it at full pressure.

Sincerely
Darryl Keil


 
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Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : Re: Honeycomb Core
Posted : 2005-08-22 1:48 PM
Post #32362 - In reply to #32360
I've used resin coated paper honeycomb core a couple times and found it very easy to use and was quite happy with the result. When I needed to trim the paper honeycomb I simply used the table saw. Seemed safe, and gave very straight edges. Any better method?

Has anyone experimented at all with different thicknesses and # of layers of paper honeycomb to see the effect on overall strength on 4' x 8' panels? I'm wondering if there would be a noticeable difference in terms of resistance to deflection from say 20 pounds at the center point using three 1/4" MDF sheets and two 1/2" honeycomb cores versus two 1/4" MDF sheets and one 1" honeycomb core versus three 1/4" MDF sheets and two 3/4" honeycomb cores versus four 1/4" MDF sheets and three 1/2" honeycomb cores. Granted these panels would be different thicknesses, but a 3" wide MDF strip can always be glued to the bottom edge to make a panel thicker.

Thanks, and very curious in Cincinnati.


 
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Darryl Keil

Posts: 1453

Joined: 2003-05-22
Location: Maine

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Subject : Re: Honeycomb Core
Posted : 2005-08-23 2:23 PM
Post #32365 - In reply to #32362
Don,

Two general rules around honeycomb panel strength.

1. Thicker the honeycomb stronger the panel

2. A panel at the same thickness will be stronger with two layers of honeycomb over one. Example, two 1/2" honeycomb on top of each other with a ply sheet separating them will be strong than a single 1" honeycomb. Whether you use a 1/16" or 1/4" separator sheet between honeycomb will not effect the strength much.

Now there is a cross over point where a single sheet of honeycomb will be stronger than two sheets on top of each other as the single sheet gets thicker. Where that is I cannot not say without some serious testing. I would assume a single honeycomb sheet at 2" would be stronger than two 1/2" stacked sheets.

I'm not sure I would be inclined to stack three sheets on top of each other. First, the panel does get heavier every time you place a separator sheet between each honeycomb layer. Second the labor increases as well and the thickness of the border gets trickier to get correct for every layer added.

Sorry I cant give you any scientific conclusions on your question.

Sincerely
Darryl Keil


 
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StanMo

 
Subject : Re: Honeycomb Core
Posted : 2005-08-24 10:01 PM
Post #32366 - In reply to #32365
Darryl,

What kind of separator ply is used? And do you glue up all at once, or in phases?

Thanks,

Stan


 
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Darryl Keil

Posts: 1453

Joined: 2003-05-22
Location: Maine

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Subject : Re: Honeycomb Core
Posted : 2005-08-26 4:26 PM
Post #32367 - In reply to #32366
Stan,

What you use for a separator ply is not important. I usually use 1/8" luan plywood.

You need to glue up everything at once except the veneer. I do that in a second pressing.

Sincerely
Darryl Keil
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