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I am considering laminating some Pear veneer to make miniature plywood to replace regular kit plywood parts. Does anyone have experience doing this? My concern is what adhesive to use.  Titebond 2 is my usual glue, but I'm worried about the moisture content. Would 3M super 77 spray adhesive last and not delaminate? I think CA would not be good if trying to get a natural finish. Any thoughts?

 

Kurt

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14 hours ago, Kurtrjohnson said:

I am considering laminating some Pear veneer to make miniature plywood to replace regular kit plywood parts. Does anyone have experience doing this? My concern is what adhesive to use.  Titebond 2 is my usual glue, but I'm worried about the moisture content. Would 3M super 77 spray adhesive last and not delaminate? I think CA would not be good if trying to get a natural finish. Any thoughts?

 

Kurt

 

Hi Kurt,

before you try making your own Plywood from veneer sheets, would it perhaps be an alternative for you to utilise so called multilayer aero-plywood ?

I used for examlpe 10-layer ply in aero quality in total thickness of only 5,5 mm, and got very strong filigrane thin parts (frames for my Pegasus build) out of it....

 

Nils

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Nils,  The parts that I want to make are provided in the kit in fine laser cut Aero-Plywood. I am striving for a natural wood finish in Pear as much as possible. I believe a single piece of wood would be too delicate and snap for some parts. Therefore I plan to laminate the veneer with multi directional grains. I'm hoping look okay when the finish is applied.

 

Kurt

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Kurt,

 

I've never laminated layers of veneer to make plywood, but I have often used a great technique to laminate veneer to a substrate.  You coat both pieces with Titebond and let it dry completely.  Then using a household iron set high, but not high enough to scorch the wood, and iron together.  I've used this trick on fine furniture I built as long as 30 years ago and have never had a separation.

 

Best,

John

 

 

image.jpeg

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Kurt,

 

I have used diluted PVA glue to veneer furniture.  The veneer was still holding 20+ years later.  It should work for this as well.

 

Simply brush the diluted solution onto one surface, lay up the veneer, and then iron with a medium-hot iron.  Depending on veneer thickness, you should be able to lay up several sheets in one pass.  A sheet of paper between wood and iron would be a precaution against scorch marks.

 

It's very quick, so you could run a test in about 5 minutes.

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I've used Titebond without issues. Remember to to make a balanced 'sandwich' with grain alternating directions at the gluing face. The glue does re-activate with heat, but I'd be concerned about how deep into the layers heat would penetrate. Heat is great for simple veneering, though. (See John's posting, above.)

 

I apply Titebond generously and clamp the assembly well with waxed paper or cling-wrap to contain squeeze-out.

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Why do you have to remake the part?  Why not just add your pear veneer to the current part to get the finish you want.  If it will be too thick or over large after the application, sand down your high grade plywood or run it through a thickness sander before you apply the veneer.  A lot of kits cover the plywood with a strips of other woods.   

 

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Back in the good old days, plywood was made with "resorcinol glues."  These were synthetic plastic resin glues.  The glues came in two parts, a resin and a powder that were mixed together.  My father and I used a lot of the stuff in 1960 in the construction  of a sailboat.  It was easy to use, worked every time ind did not involve water.  

 

According to the internet resorcinol glues are still available.  DAP apparently makes one but it is sold as a powder to be mixed with water.  Titebond III is apparently another and is sold premixed (with water?). The two part resorcinol glues like I used appear to be available but I didn't see any small quantities. In the boatbuilding world resorcinol glues have supposedly been superseded by epoxies.  I have personally had excellent experience using WEST SYSTEM epoxies and these would work well for your purpose.  In recent years these have been produced in small disposable units so you might research this option.

 

Roger

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I did a little more internet research on glues.  Apparently the family of glues known as Urea Formaldehydes are preferred for laminated structures such as plywood.  These were used way back in WWII to build the famous RAF Mosquito bombers. These were built with balsa cores and birch veneer laminated inside and outside to produce a very stiff structure.  The same principal as a foam or balsa cored fiberglass boat.  These glues which are readily available and cheap will stand up to the high clamping forces required.

 

Roger

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I made 3 layer ply using thin cherry and Titebond II.

It worked well.  With PVA, the strength of the bond 

increases as clamping force increases.  Use two

totally covering dead flat surfaces with as much

pressure as you can get up to fiber crush and leave it

 to dry for 48 hrs.   Contact cement is not long term

stable.  I would not trust 3M 77 long term either.

The marine adhesives advantage is in its ability to

hold while experiencing long term immersion. 

Unless you are building a pond craft that will

store afloat, I don't see the need for these adhesives,

Higgins Boats and PT Boats full size sure.

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A couple of things 

Firstly depending on how thin your veneer will be you might experience soak through staining the wood from the inside with the glue as it soaks through the fibers. possible cloud distortion and it might make it hard to finish.

secondly to get a even and solid air free bond you might consider making a small vacuum table You seal the layers with there glue on them in a vacuum bag suck out the air and let the atmospheric pressure do the work 

Contact cement falls apart in damp air and in the USA the EPA has ordered most of the good stuff taken out of it so its KID friendly Titebond II or III would get my 10 cent vote

Happy gluing

Andy

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Why is CA a problem for natural finishes? That's the one case where it's never a problem since it's crystal clear. Most cottage pen makers use solid CA for the finish since it's also nearly indestructible. I started using it 25 years ago as my preferred tool handle finish and it still is today, you can make it mirror shiny if you want and it's still more grippy on skin than wood is, and it will stay nice and perfect even bouncing around on a workbench for years.  

 

Don't go with a new glue for a single part. How big is this part? Unless much bigger than I am thinking, take two pieces of pear and put them 90 degrees to each other, use titebond or slow CA, put between two pieces of plywood, clamp with c-clamps. I've made up to seven layer plywood this way for carving scale airplane props. If you use CA you do it one layer at a time.

 

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Plywood with parallel grain layers ? Sounds like a contradiction in terms ... Plywood per se was invented not to be bent (or warp). Laminated structures are something different, of course. Diagonally plankend boats, where the layers are glued together with marine glue have existed for more than a hundred years now.

 

I don't think the glue as such is very important in a static model application. It is important to get a good penetration, so that the glue locks the layers together. Soaking through veneers can be a problem, as it will occur unevenly, so that the following surface treatment will also penetrate unevenly. I am not a great fan of CA due to its messy application, but penetrating the wood with it would make indeed a strong composite material and is being used to strengthen small parts. 

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8 hours ago, wefalck said:

Plywood with parallel grain layers ? Sounds like a contradiction in terms ...

It's specifically designed to bend freely on one axis, not only is the grain all one direction but it's been split a bunch (or at least the stuff I used 30 years ago was) such that only the inner layer is solid. 

 

You know all those news shows and office greeting areas that have curvy fronts covered with veneer? This stuff is the substrate, veneered via vacuum bags.

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