Bent Lamination -- how thick on the veneers?

[Matt Meiser]

I'm going to be doing a bent lamination for dining table aprons in cherry. I'm using the URAC 185 glue and bending around a yet-to-be-constructed MDF form. The outside diameter will be 44" so inside will be 42.5". How thick should I plan to make the veneers?

Also, each half of the table will be a semi-circle with a a bit of a straight section. My plan is to make aprons one piece. Anything wrong with that idea?

[alex grams]

I typically make mine about 1/16" to 3/32", depending on how many I am using to build up the laminate.

Can you find bending ply anywhere for a filler? I usually use 3/8" ply + 2 x 3/32" on each side of the ply.

Your plan sounds good. I use Pro-Glue Veneer Bond Resin (http://www.amazon.com/Pro-Glue-Resin-Veneer-Bond-Ounces/dp/B003CMKKB2) and never really have to contend with springback, or at least not on any significant level.

[John TenEyck]

You also can buy bending ply in 1/8" thickness, which would give you a much stiffer assembly with all those extra glue layers, just like it will if you use solid stock laminations. Assuming you will use solid stock, for something as large a radius as you are bending you could easily use 1/8" thick sections. Be sure to use a couple of backer pieces on the outside to help distribute the load

[Prashun Patel]

Do you have a drum sander? If yes, then the thinner the better, IMHO. Easier to bend. I also read an article on making a thicker center lamination that's kerfed for easier bending with thinner outer veneers. They argued that there was less risk of springback this way, and it was easier to mill and glue up.

[Frank Drew]

For that design (two part racetrack), bricklaying the apron then double veneering the outer face is an alternative construction method, and there's no worry about springback.

[Matt Meiser]

Well, I went with the 3/8" bending ply and 2 3/32 veneers on each side. I do have a drum sander so cleaning them up with one pass after resawing was a snap. Test fitting them around the form went fine.

I bought a quart of URAC-185. Not enough. I followed the by-volume directions and used virtually all the hardener they sent for a little over a pint of glue and used all that for one side (pieces are 3-1/2" by about 7' 6 or close to 18 sqft of area speading glue on both sides. I put it on way too thick obviously as I had a ton of squeezeout but I'm not sure how I could have applied it thinner unless I had used a notched spreader. Maybe I should have just spread it on one face? And that excess made for some gaps that will be full of hardened glue that didn't show up when I did my initial test.

[Jeff Monson]

Good choice on the bending ply. I've had some wrestling matches with too many laminations and getting everything lined up to get in the press. Seems for me once the glue is spread it's like "lighting a fuse". Hurry up and get away.

[John TenEyck]

IMO, Weldwood Plastic Resin glue works as well as Urac and is generally available locally. Costs less, too. Anyway, in general, you only apply glue to one face, and it's not much. I think a pound of Weldwood covers around 40 sq. ft. I put it on with a mohair or foam roller. It always looks like it won't be enough but if you have uniform clamping pressure, it is.


John

[Frank Drew]

I agree with John that Weldwood's Plastic Resin glue works quite well with laminating, and veneers in general.

[Matt Meiser]

I've used it before and it worked fine on some veneer. However the first stuff I bought locally was old and wouldn't cure. Their date code isn't readable without a super-secret decoder ring. The stuff I had another local store order from the Do It Best warehouse was just barely in date.

I won't use URAC again. A friend gave me enough Unibond 800 to do the other lamination.

The first one came off the form this morning. I cleaned up the glue on one edge on the edge sander, then used my BS to trim one edge, then the other edge. It is just big enough to curl over the top of my BS to finish the cut. Working on cutting the veneers to do the other right now.

[Dale Cruea]

Pictures Matt. We need pictures for us that have never done this before.
This why I am here.... Pictures..... :p

[Matt Meiser]

Here you go.
212083212085
212084

Just finished the second with Unibond. Glueup went much better. Next time though I would definitely either use 2x as many clamps, or make a female form as well. There's some definite impressions where the clamps where and some glue-filled voids--you wont' see them on a table apron, but if this was a more visible piece they would be very noticeable.

[alex grams]

Matt,
When I clamp laminations down like that, I find it helpful to stretch another piece of bending ply over the top (with a sheet of plastic between the top bending ply and the glued up pieces. This helps to alleviate pressure points/clamp marks and helps even out the pressure from the clamps some.

Looks good. That is a big form, I hope you save it and get to reuse it for another project. I hate making forms that are one-offs and do nothing but collect dust. I think i have several forms in the attic for end tables of different diameters (16", 18", 20" diameter skirts)

[Dale Cruea]

Looks good to me Matt.
I have done anything like that but still looks good to me.
Thanks for the pictures.
Keep us posted as you continue.