Best sheetgoods to veneer to for table tops.

[drodda]

I am looking for suggestions for a strong sheet material that will be easy to glue veneer to that will hold its own weight without deflection. MDF is a material I have used, however if you hold it by the ends flat the sheets bow under their own weight. Is there a good sheet material that does not bow under it's own weight that is also dead flat to accept burl veneers?

-D

[tmerrill]

Dave,
First product that came to mind is Baltic Birch. It comes in 5 foot square sheets and is commonly available in thicknesses up to 3/4". You used to be able to get it in thicker sheets, but I haven't seen it listed for a while. You can alway laminate two thinner sheets together to get a thicker sheet.

Now, having said all that, I'm not sure you will find a sheet material that will hold its own weight without deflection. A lot depends on the size and distances you are looking at.

Possibly some of the ultralight mdf's might work, but I've never used them.

Another thought, if thickness isn't an issue, is use thinner sheet goods and create a torsion box.

Tim

[beacon14]

Look into paper honeycomb cores used with a thin skin of MDF or 1/8" plywood. Do a web search on "honeycomb paper panel"

[wberminio]

How thick do you need your material?

If you are laying up your own veneers,(not paperbacked veneer)MDF backer would be best choice.
If you can't find "honeycomb paper panels",
I would construct a torsion box panel-
basically 1/4"MDF skins with plywood or solid wood
strips glued lengthwise.
This will create a strong lightweight panel, while minimizing thickness.

I've used this method to create floating shelves and table tops

Erminio

[fmihm]

Dave Rodda --

I don't think that ANY material can be supported as a simply supported beam -- such as holding a sheet by its ends -- and not have ANY deflection. This just isn't physically possible.

However, many materials may be stiff enough to satisfy your requirements. It's just a question of your panel's dimensions and how much deflection is acceptable to you.

David Buchsbaum suggested honeycomb panels. Honeycomb panels can combine very light weight with great stiffness.

To calculate the deflections of honeycomb panels you could search for:
calculation of deflection honeycomb panels

Alternately you could contact some honeycomb panel suppliers and ask them for deflection information. For the suppliers, you could search for:
honeycomb aluminum OR paper panel

Note that honeycomb panels come with faces of paper, aluminum, various laminates, fiberglass, etc. Commercial panels designed for flooring or walls might be worth considering.

Hope this helps.

[wayne_walker]

Dave,

Here is a link to a honeycomb paper product.

I have purchased it thru Laird Plastic.

http://www.plyveneer.com/

Good Luck,

Wayne

[wayne_walker]

Dave,

I neglected to mention you have to use a waterbase contact glue.

I would check with the manufacture for their recomendations.

Wayne

Wayne

[drodda]

Tim,

I have used Baltic birch in the past, however it seems even baltic birch is starting to have issues with flatness. It is also quite heavy. I am looking for a 3/4" material that has a flat and smooth surface on the outside but is still strong enough to not bow on a 75" diameter round dining table without any braces or support under the table besides and apron around the very outside of the dining table.

Has anyone ever used HDO for this purpose? How strong is this type of material? MDF tends to bow down in the center on a table like this.

Thanks for the hlep,

-D

[cabnet636]

all substrates need to be balanced with a backer laminate to match movement, to many times novaply's and mdf is overlooked, but the bottom line is they share epansion and contraction rates with veneers and laminates, juist about any substrate that is not sealed or baked will move indifferent to the top layer

jim mcgrew

[tmerrill]

Dave,

For a table top that size, I would think you also have consider how it would be used. In other words, finding a material that will stay level across that distance is one thing, but finding a 3/4" material that will also withstand someone resting their elbows on the table is something else. Other than stone or glass, I'm not sure you will find what you are looking for.

Tim

[beacon14]

Here (http://www.vacupress.com/accessories.htm#honeycomb) is a user-friendly source of honeycomb panels. They are very knowledgeable about veneering and will answer any questions, also they have a great forum on veneering.

The panels do need to be faced on both sides with a skin of your choice. By themselves they will bend like crazy (they can be used to make curved torsion boxes) but once you glue a skin to both faces they are "stiff as a board". You can butt smaller pieces together end-to-end to make the size you need (the skins should be one piece).

If you've never used these honeycombs or seen them in use, the reaction is similar to seeing vacuum pulled through MDF for the first time. Your brain tells you "this is crazy" but the fact is, it works.

[bill_moore]

My lumber rep gave me some samples of a product called Foamkore by Interior Products it is a blue foam core with various materials laminated to it both sides very stiff and very lite weight. I have seen entire cabinets made from it at the FWS show in Vegas. I don't have any links though.
Bill

[bill_moore]

Update Found the website for the foamkore. www.kerfkore.com (http://www.kerfkore.com) 800-637-3539 Their 1/2" with 1/8" poplar ply laminated to both sides weighs 10 oz. per sq. foot.
Bill

[cabnet636]

phenolic backer laminated to the opposite side of the burl will do the trick, we have used foam core and corragated for lightweight situatons only (plane's and yacht's) i have a 6 year old 20'x5' mohogany boardroom table left from 5 we built for a corporation still sitting in the shop and it is still as flat as the day we built it!! (mdf center 1.5")

we took it back on trade as a fellow carved his name in it as he was being fired!!

any body need a slightly damaged 20' table?

jim

[angus_hines]

Jim,

Can we strap it to the top of a Volvo ?

[cabnet636]

in the early day's it is how we did it!! once droped a unit of ply out of the back of the truck headed up hill one sheet at a time!! i was just gettin impressed with the getup of that truck and then i looked behind me!

jim

[drodda]

The elbows really pose no probelm on these table tops as the table is supported at the elbow area. The very large centerpieces or vase of flowers in the exact center left there for a long period of time seems to be the worst as the center is floating and not supported by anything.

What do you use to attach a solid wood edge to the foamcore?

Thanks for all the responce to my question. Has anyone ever use lumber core plywood for a veneer job?

-D

[waynelocke]

I purchased some EuroPly from North American Plywood in California, http://www.northamply.com/. The link did not work just now. This is a, I think, 17 ply 3/4" plywood similar to Baltic Birch but of better quality. Also it is available in 8' X 4' sheets (the grain goes in the 4" direction) so that it can be veneered the full 8' without crossbanding. I think that it is also available in 1" thickness.

This is expensive, about $75/ sheet plus shipping, if I recall correctly, but it is a terrific veneer core.

[woodworx]

http://www.cfpwood.com/products/prodeuro.aspx


europly. Formaldehyde free, Russian Birch. Glued up with Phenolic glue. We use this for the new Cajon drum currently in the virtual showroom.

[bleeth]

Dave: 75" is too far for no support with a 3/4" material unless you venture into some extremely expensive stuff. Paper honeycomb won't do it. Since you have an apron why don't you put a couple of frames across it the same size as the apron?
Guys-don't forget that with the overall size Dave will be laying up thinner pieces to get to his thickness before he veneers. So if he were to try a divinicell type material then he would be using 1/2" core and a layer of 1/8 on either side cross laminated.

[drodda]

Dave,
The dining topper fits over the top of a Poker table. Like a cover lid. The table rests on the padded rail just inside the apron of the dining top. The actual free span is about 62" across the center as the poker table is recessed down in this area from the top of the rail. There is no room for anything attached to the bottom of the dining top across the center.

I am checking into the Europly, and a product called performance core. Performance core is an OSB type core material with veneer on both sides. It uses an exterior grade glue which is supposed to make it much stiffer than regular OSB. Anyone ever use it before?

The other issue is I have to join two sheets together to get a 75" square to start with. So the material has to be able to get a strong glue joint when attached.

-D

[garyb]

We use core-stock here but it is a solid wood with an applied veneer.
you might look into it

[bleeth]

Dave:If once the table top is on the padding and you have for example 3/4" then you can put a block in the center to fill most of that space. You can also use that block as a butt block to help your joining. You can also do your joining on the bot with Bill Young's step scarf. Lots of glue area and designed for a flat surface.

[drodda]

I have never been able to get Bill's scarf joint to lay perfectly flat once glued up. The last time I used that method it took hours of sanding to level the joint. It seems that sheet material varies from delivery to delivery. I do not have a vacuume setup.

As far as any Block on the center. The poker table has a 1/4" foam under the center felt so any block would leave a permenent indent in the center of the playing surface if the dining top is left on the table for any length of time. Unless this block was the full size of the playing surface. This would add so much weight to the dining top that I am not sure anyone would want to remove it once placed to play poker. I used to use 1/4" baltic as a stiffener to the bottom of the plywood to support the joint. I have went away from that in the last few I have done.

It would be near impossible to calculate the ammount of rail foam compression the table top would cause to figure out the height of this blocking. SImply because the blocking itself would add or subtract from the weight of the top and therefore change the compression.

I appreciate all the help on this. There has been alot of good information talked about in this thread. Hopefully someone else will find good use for some of this brainstorming. There are so many new types of engineered sheet goods out there that sometimes we don't have time ourselves to tryout each and every one. Lumber salesmen are good at pushing a new product, however is his motivation that it's a great product or that it has high profit margins for his company?

Thank you all,

Dave

[bleeth]

You have mail.

[myxpykalix]

Dave,
I didn't go back and reread all posts but why couldn't you take a piece of lightweight foam in the shape of the top and glue it to plywood and with some of that bendable plywood make your edge as shown in the cross-section drawing. Your foam would be thick enough to rise above the padded shoulders. It would give full support evenly over the table surface and not let the elbow pressure tilt the top or flatten your padding. That to me would be a lightweight solution, if i understand what you want to do..

8164

[dray]

I would use the MDF.

But you would need to also laminate something to the underside to equal out the surface tension.

Any product you use will most likely need to be laminated on top as well as bottom.

By only laminating/sealing one side (the top) this leaves the bottom more open for humidity expansion causing the edges to bow upward.

[Gary Campbell]

Dave....
Sorry to get in here late, but I have a good, but not inexpensive product. We have made large panels from NYDA-CORE (http://www.nida-core.com) the product we have used consists of a honeycomb core with a thin skin of fiberglass on each exterior face.
This product is light weight and could easily span the 75" distance with around an 1/8" of deflection in the center of your table using 1/2". 3/4" would have no noticable deflection. product can be joined easily with 4" mat tape and vinylester resin. Glues well with FG resins, epoxies and urethanes. You may need to put a skim coat of filler under the veneer for perfect flatness.
Gary

[davidp]

I agree with Danny

MDF is probably the most stable and cost effective product and if it is veneered on both sides you will get almost zero distortion.

If you only veneer one side of any product, be it foam, uPVC, steel, aluminium, whatever, you will get bowing at some stage.

David

[drodda]

MDF is heavy and sags without support under the center.

Both are undesirable traits of MDF for this project.

I do veneer and seal both side.

Mdf will still sag even when sealed.

I am experimenting right now with Combi-Core. I will let you know how it goes. This is a veneer core with 1/8" MDF faces on each side.

-D

[dray]

Ultralight MDf shouldnt sag, providing you laminate both sides. By doing this you are shearing it.

Standard MDF is a poor and heavy product at best.

[wberminio]

Ultralight MDF will still sag over time,if not supported.I used it exclusively over regular MDF.We're very fortunate here,I can get Trupan from 1/2" to up to 2 1/2 thick.I have use a Combi-Core type product it just might work.

Erminio

[fsrdoug]

For long unsupported spans I always use 2 sheets of 1/2 inch ultralight MDF or 3/8 baltic birch with a grid of 3/4x1 hard wood laminated between. This is very light and will not sag. I built an 8 foot long shelf that is loaded with books and sheet music 3 years ago and the customer says it is still straight. I only used supports on the ends.

Doug

[wberminio]

Doug

You're talking about a torsion box.
It really does work!
You can also use 3/8 or 1/4 material.

Erminio