Advice on a Bent Lamination Deck Chair

[Sean Rippen]

Hello Creekers,

I believe this is my first post on this forum, although I am an avid lurker and have used this site for a few years now as my go-to research hub for my various woodworking projects.

I started woodworking roughly five years ago, during which time I inherited an incredible amount of tools from my grandfather who was an avid woodworker during his lifetime. I spent 2014 making a dresser for my son (no, it should not have taken a year to build...), and then got sidetracked in 2015 by some smaller projects - a new set of stairs in my basement, a pallet wood "Maryland Flag" for a friend, and a routed sign that my in-laws requested. I must be getting bored at home because I have found new inspiration for a project to tackle - this curvy lounge chair shown below.

stilvoller-liegestuhl-moderne-lounge-sessel-designs-aus-holz.jpg

I assume this chair was made via bent lamination, and that is the method that I intend on utilizing unless someone on here strongly advises me otherwise. I have a few questions for those that are willing to give me guidance on this project:

1. I plan on making my forms with 3/4in by 4ft by 8 ft sheet goods. Keeping the cost down is of course a goal, so I am wondering what would be the cheapest but reusable medium to use. At Lowes/Home Depot, it looks like I can get OSB for $16/sheet, but is OSB strong enough? Plywood seems to be the medium of choice, but plywood sheets are also quite a bit more expensive. Am I a fool for shopping at a Home Depot type store in the first place? Do the pros go to lumber yards and laugh at HD lumber shoppers?

2. To achieve the chair's balance, I would assume the designer used math to determine where the curve's low point should be relative to the chair's top and bottom. I am not sure how to calculate this. Instead, I am figuring that I could embed weights on the underside of the top or bottom if need be. Is this a silly idea? Maybe I should just learn how to design things...

3. It's hard to tell, but to me, the boards do not look overly thick in this chair. I'm guessing they're an inch or so thick. I want this chair to be durable, and to not have to worry about turning it into a pile of splinters if someone sits on it too hard. Is there a way beyond trial and error to determine how thick to make this lamination? Also, I've read that more ply's is stronger, so I am planning on resawing my laminates to 1/8in or less unless advised otherwise.

4. Lastly, does anyone have any recommendation for what type of wood would look nice, not break the bank, and most importantly, be sturdy?

Thank you in advance! The wealth of expertise and knowledge on this site is amazing.

[Doug Garson]

Can't answer all your questions but one suggestion for making it strong and lightweight would be to fibreglass it on both sides similar to how a stitch and glue or cedar strip kayak is made. When the glass cloth is wetted out it becomes almost invisible. The sandwich of fibreglass on both sides of the wood is incredibly strong, in fact the strength of the wood is insignificant in the overall structure. You could use several laminations of straight grained cedar followed by the glass. Looks like a cool project. Note most epoxy resins require UV protection, most use spar varnish.

[Sean Rippen]

I love this idea. I've never worked with fiberglass, but that's what YouTube is for. I take it the sun would turn the resin yellow without UV protection? Thanks for your input.

[Andrew Hughes]

Looks like a simple chair I doubt I could make one cheaper or better then that one in the pic.
I do like your taste.
That chair is a Ferrari of deck chairs.

Aj

[Brodie Brickey]

The power of the bent lamination is that you can force multiple pieces of thinner stock into a shape they normally won't hold and then glue them in place. You would have to do a lamination to get the rigidity/strength needed. The lumber would have to be very straight, rift or quarter sawn.

In the inexpensive woods category, I would look at Ash. It is hard and springy, some people use it as the inner core of back slats that need spring. I don't know how it holds up as an exterior wood, but a hard wood as the inner core and then an exterior wood to give you your desired color might work for you. Depending on your area also look at Yellow Pine and possibly Beech.

Your sheet goods will be used to build the large forms you will need for this thing. I hope you have lots of clamps.

I would see if you can find some plans on sketchup. Chairs like this and the Vita chair require a lot of planning, unless you want to rinse and repeat until you get it right. That could get kind of expensive. You might also make a plywood version to start without bent lamination to see where balance points need to be made. Then do the actual chair.

[Mel Fulks]

I think more thought went into making it difficult to copy than went into making it comfortable. One butt joint is showing and the camera angle conceals ,IMO, butt joints on the other pieces. Consistant curves are much more easily laminated than S things. Keep us informed and good luck to you.

[Sean Rippen]

Thanks for the replies. I have thought about making a scaled miniature to figure out the center of gravity, but on the other hand, if I can get the balance point close enough, simple weights at the head or feet can finish the job. I've looked for plans but so far have been unsuccessful there.

I have a lot of clamps - rafters in my basement lined with them - but I may find out I need more once the forms are done.

This will be my first foray into bent lamination, so if the project turns into an utter failure, I still assume I'll learn something along the way.

[Joe O'Connor]

Just a thought but I think if you left you pieces long say 6 or 8 inches you could slide a top and bottom lamination back and forth using clamps to temporarily hold their positions, find the balance point and cut to length. I like the idea of cedar with fiberglass. Very ambitious.

[Sean Rippen]

This is a great idea! Definitely makes more sense than embedded weights. I was on the internet last night reading how to calculate "center of gravity", but all of the physics websites either use a very simple linear example that doesn't apply to curves, or they use formulas that are well beyond my comprehension. Thanks Joe. This comment just solved my balance problem.

[Sean Rippen]

For those interested, I found a "from the side" picture of the chair on a website that I think is in German. This is actually quite helpful to me, as I was able to rotate the image until the top and bottom of the chair are inline with each other, stretch it across a 4 by 8 canvas while maintaining the original aspect ratio, and now I have my measurements. Much to my pleasure, I now see that I can actually cut two forms per 4 by 8 piece of sheet goods, cutting my cost of forms in half from my original figures.

Thanks again to all of those who have chimed in.

Deck Chair Measurements.jpg

[Pat Barry]

I think the weight of this would be pretty high with 1 inch nominal thickness but I suspect that if you went 1/2" thick with laminated material it would be plenty strong. The adhesive used might be important though since this chair would likely see some flexing in use with different people loadings

[Sean Rippen]

Awesome thanks. As I've mentioned, I've never done a bent lamination so I have no concept of how strong various thicknesses of lamination would be. I can do 1/2 inch laminates, and then if I go the fiberglass route, I assume I'll be okay.

[Doug Garson]

I think 1/2" would be more than enough. If you check out Pygmy Boats website (kits for stitch and glue kayaks and more), they use 4mm (5/32") Okoume plywood for their kits and a kayak takes more abuse than a deck lounger. Typical cedar strip boats are 1/4" thick strips. As I said before, in the sandwich construction with glass on the outside and wood in the middle the main strength is in the glass. You could try a mahogany plywood door skin as a prototype, I think you will be surprised at how strong it will be.