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  1. #1
    User TENdriver's Avatar
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    Laminated Chair Legs

    So, I've been contemplating building an upholstered chair. It is a continuation of my building furniture with SYP. The frame is SYP but the legs are hardwood.

    I have some figured soft maple stock that will work for the legs, but I'm concerned about some areas of "short grain" in the three back legs. So I'm thinking about laminating the back legs. I haven't done any laminations for several years and don't remember that much about it. I would prefer to minimize experimentation so I'm looking for inputs from anyone who has done this recently.

    One side of the legs will get hand planed for the mortise and tenon frame and stretchers. The top of the legs are cut at an angle for the chair back frame.

    Couple of issues:


    Plan is MDF (packing taped) mold on top of a melamine base. I think I can make the convex shaped mold single sided for the back of the leg and just use a plethora of clamps to hold the laminations versus a second mold pushing on the front. I have to mill the front side anyway.



    Gorilla glue was used in an American Woodworker video. I like the idea of longer open time, easy clean up of squeeze out and that I can hot "H2O soak" the laminations to ease bending, and the moisture will work with the Gorilla.


    How thick can I make the laminations for a 2 1/2" by 2 1/2" leg that is 24" long? I'm planning to rip the laminations on the table saw, so +1/8" per cut is sawdust, less laminations is less waste.



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    Re: Laminated Chair Legs

    I use Dap Weldwood plastic resin glue. It is available at Ace hardware. Be sure to wax the forms very well as this stuff is really strong. The lamination pieces need to be about 1/8 to work well and bo steam is needed. Use a waxes call between the outer piece and the clamps. The weldwood has a very long open time and takes 24 hours to dry. Warning. The squeeze out is sharp and will cut you. The excess is really hard and easiest removed with an angle drinder and flap sander wheel before jointing the first laminated side. The other side can be removed on the table saw using an older blade if you do not sand off the excess glue.

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    Re: Laminated Chair Legs

    Weldwood is a very strong glue. Be sure to note that the piece needs to be kept at a minimum temperature for the entire cure time. Sorry, I don't remember what temperature that is off hand, but it's on the can. The other important thing to remember when working with this glue is not to wipe any glue that gets on your hands on your clothing. As Jeff pointed out, it dries hard. It is water proof so it won't wash our and when your clothing is bent at one of the places where you've wiped your hand the material will crack making a hole. I don't know how many pairs of jeans I ruined with this glue as i'm not a very neat worker.

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    Re: Laminated Chair Legs

    Guys, Thanks for the suggestion of the Weldwood Plastic Resin. It forced me to do what I was trying to avoid, which is deep dive into research to get answers.

    The Weldwood was not on my list, but it seems to be the "go-to" glue for laminations. I'll have to do more research (Ughhh!) on how to machine it since I was planning to stick with my hand tools. I don't have an angle or die grinder and from reading about the UF glues, it's not at all safe to inhale the dust. Any dust is one of the two reasons (and noise) that I'm trying to rely more on hand tools.

    I haven't totally excluded the Polyurethane (Gorilla Glue) on wet bent wood. The primary reason I may exclude it is the issue with gap filling and clamp pressure. The Weldwood seems to eliminate those two issues.

    I'm also now considering the possibility of using a PVA. I'm looking to build for at least a 50-100 year life expectancy. I prefer to build for longer, but 50-100 is a reasonable compromise since I won't be around to hear any complaints anyway. in any case, turns out Sam Maloof allegedly used plain old PVA to laminate the rockers on his famous rocking chairs.

    Lastly, I'm still in the dark on the lamination thickness. I didn't want this to be a major science project, but it looks like I'll have to run some tests to determine how thick I can get away with on my curve. Today I bought the melamine and MDF to build my forms so I'm a little closer to an answer.



    Ironically, I could avoid all this if I just skipped researching about laminations and use the maple I already have, which is starting to look like it may be a reasonable thing to do.
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    Re: Laminated Chair Legs

    For that shape I would not bend, I would do a three piece lamination with the grain of the middle piece strengthening the outer two.

    And good old Tightbond III would work for that.


    second look; I see there are some mortises that would weaken the leg if flat laminated.

    the bend seems to be about 2 inches deep in a 24 inch piece so 1/4 inch should do that. You might try one piece of 3/8 just to check. 6 pieces of 3/8 will give you 2 1/4 OR 8 pieces of 1/4 would make an even 2 inches. You could taper the back three pieces for even greater strength.

    do 2 at a time and use Tightbond.



    One machine can do the work of 50 ordinary men. No machine can do the work of one extraordinary man." -Elbert Hubbard

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    Re: Laminated Chair Legs

    Mike, I was slowly moving in the direction you recommend. The only real concern left was if having the thicker laminations would cause the PVA to creep a little more since it'll be under greater tension. Seems a fair number of people report the laminations start to telegraph with time and humidity. One of the reasons that the UF glue gets used.

    Your suggestion of three layer lamination may still be an option over the bending. It's certainly easier and would strengthen the short grain even if it's just a marginal improvement. I was starting to feel that I was over thinking these legs, but I just checked the original, and the short grain failed exactly where you would think it would. I've had too many short grain failures in different pieces and I want to minimize the risk in these legs.



    BTW, Thanks for chiming in. You're the only person I knew that had done some recent bent laminations. My last shot at this was a couple decades ago and it was something simple and very small scale.

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    Re: Laminated Chair Legs

    There are other options. Maple is relatively inexpensive lumber to work with. I generally purchase at least 6" wide material and position a chair leg in such a manner to get the most long grain in the lower portion that sits n the floor. There is a lot of waste but if you are making a chair to be an heirloom, the cost is not the main factor. FYI, I generally work with Walnut or Cherry and the cost is typically 4 times that of maple. The seat and crest rail are the most visible pieces of a chair but,not from he front. From the side, the legs are the primary pieces in the line of sight. No matter how good you are, the lamination lines show up. Walnut is better than cherry which is much better than maple. The only way to make the rocker for a Maloof chair is to do bent laminations as the arc would require 12-14" boards and there is a weak point in the drain otherwise. My second Maloof rocker was ambrosia maple as the lumber is generally $2.50 per square foot. I have never been satisfied with the rockers. My first rocker made from Walnut made the laminations nearly invisible. I am not sure how Maloof made the infamous tiger maple rockers and I have not had an opportunity to see one in person. I assume it is perfect just like the joinery on the other pieces that I have seen in the Renwick. The plastic resin glue is brown and hence this may be why it shows up so much with maple.

    if you really want to do laminations and use plastic resin glue, you can always sand it off with a belt sander. Just wear a mask. I have a trend airshield so I never breathe the dust. A Festool Rotex sander also removes it quickly and there is little to no dust. The plastic resin glue could wreck havoc on jointer blades or a hand plane. However, you may be able to sharpen a lowes Stanley beater hand plane enough to remove the adhesive and use a good hand plane to clean everything up.

  8. #8
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    Re: Laminated Chair Legs

    Interesting, Maple and cherry are pretty close to the same price up here and walnut is about 60% to 70% more.

    Actually, it's not about the cost and this is an Upholstered piece, so only the bottom 11 1/2" of the legs are exposed. It's a sofa that is against a wall so maybe not as concerned about using a darker stain and calling the back legs good. The front legs and stretchers will all be solid with some nice grain.

    The laminations are to improve strength over the short grain failures (top and bottom of the leg) from using solid wood. Turns out, the original piece has the exact failures I'm concerned about. While this is a period piece, lamination seems the way to go as I'm not planning to source some stump wood with curved grain.

    Based on my recent reading, the UF resin appears to be the more "standard" way to do laminations for a variety of pretty good reasons. Not sure I'm really set up to work with the resins. If I was, I'd probably just move forward with the Weldwood. Unfortunately, I don't have or use angle grinders or belt sanders and my dust protection is a twenty cent mask. I'm doing my best to avoid wood dust, but it does sound like the UF resin dust is an additional issue, so I may not be able to go there. I do have a great selection of hand planes, scrapers, chisels and saws.





    BTW, interesting points about the Maloofs. Looks like the Renwick double rocker's rockers are curly maple with walnut and possibly some additional species laminations. Do you have any shots of your ambrosia rocker?

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    Re: Laminated Chair Legs

    Just to add, I've used Gorilla glue on BL table legs 1/8" Leopard wood with very satisfactory results. Also, you might want to invest in a thin line rip blade to save 1/16". I re-sawed with a band saw and put them thru a drum sander.

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    Re: Laminated Chair Legs

    I have asthma and hence the reason for a higher quality mask. I generally only wear it when using the angle grinder which throws dust everywhere and whe using finishes which aggravate my breathing.
    I am a chemist by training so I read all the scary warnings and laugh. Safety data sheets as required by the government Significantly overestimate the risks associated with exposure and the hazards associated with chemicals. Urea formaldehyde resins are readily metabolized back to urea and formaldehyde. Urea is relatively nontoxic. Formaldehyde is a carcinogen but he risk factor is extremely high. The levels in e SDS are based on chromic exposures, not infrequent exposures. If you look around your home, there are many sources of formaldehyde and the levels in most homes far exceed the OSHA permissible exposure limits. All nylon carpet uses polyamide formaldehyde resins as dye fixatives hat off gas formaldehyde heir entire lifetime. OSB and the modern laminated floorings I.e. Pergo use significant formaldehyde base adhesives and again expose homeowners to significant quantities. The new car smell is highly toxic as all of th plastics and other parts in the car off gas formaldehyde especially on a hot summer day. We have much more to worry about than limits exposures with a one time sanding experience. The major problem with sanding the plastic resin glue are the particles (adhesive and wood fibers) that can be deposited in the airway and even deep lung tissue. The defense mechanisms in the body attack these foreign materials but can lead to chronic inflammation, oxidative stress and on long term exposure possibly leading to lung disease. The simple twenty cent mask provides significant protection from the particles.

    On another note, both urea and formaldehyde are byproducts of metabolic pathways in the body. The body s a well designed machine and can handle most limited exposures. Chronic exposure is the problem.

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