I am putting a molding along the curved top of a garden gate I am building out of redwood. I plan to have a half inch thick molding that follows the arch of the door top. It would be about 2″ wide, so proud by about a quarter inch on each side of the 1.5″ door thickness. If it is possible I’d like to router a dado in the bottom of the molding so it fits over the door by a bit, but it may not be possible with either of the two methods I am considering.
Which would be stronger: building up a laminated molding out of four 1/8 inch strips glued over a form or a single piece that is steam bent? I have read that steam bending can leave wood brittle. I’d like to have this piece give a little bit of structural strength to the top of the door and protect the end grain from water. The door will be made of seven vertical pieces of 2×6, edge glued with dowels and LOTS of biscuits. I made a similar door 20 years ago and it has survived fairly well, except for attacks by termites.
I have never tried steam bending but have read about it for years in Fine Woodworking. Thanks for any advice you can give me.
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What is the radius and run of the arch? A gentle curve could be cut or bent from solid stock and just attached with plugged screws. For a more severe curve bent lamination using the door as the form and waterproof adhesive would be my choice. You could build up the "underhang" edges the same way and profile them into a drip edge to protect the end grain.
Undercutting the end grain on the bottom of the door a touch will serve as a drip edge and shed water instead of getting wraparound wicking.
Either way will work. If you steam bend, you would want to select straight grain stock, joint and saw parallel to the grain or it will break when you bend it. You can use a piece of PVC pipe/caps for the box and one of those wallpaper removal tools to generate the steam. For just one piece, steam bending is a bit of trouble by the time you cobble everything together. Unless you just want to play. You would also want to leave it in the form until it dries.
Laminating would be easier. Just use a good waterproof glue or epoxy.
Other than a few biscuits for alignment I don't see any need for dowels or lots of biscuits in the gate.
Ha Ha - tried the PVC - doesn't work with the thinner stuff. Just sags. I ended up with plastic coated walnut!
Much better to make a quick box out of cheap plywood. Now I have one, I bend more - it was a real barrier to using the technique. Have to watch that the steamer does not run out of water though - they generate plenty of steam but run out a bit quickly.
I agree that laminating is the way to go for most of these forms, and you do need to use proper glue - Polyurethane is ideal and with it's good slip and long open time is perfect for a bent lamination. Epoxy would be an alternative but Gorilla Glue is cheap. High strength is not required.
The radius of the arched top is about 38" The width of the door is 37.5" So the curve is pretty gentle. On the old door, 20 years ago, I just glued a single 1/8" band across the top to seal the end grain. I'd like something more substantial. So I steam bent wood brittle and not strong? I don't mind trying something new.
Properly steam bent wood is strong, but like as not you will find that lamination will be stronger.
How many cars are you planning on parking on top of your lightweight garden gate though?
You have as has already been pointed out, three options:
1. Steam bent timber
2. Bent lamination
3. Solid timber
These are in reverse order of effort required to get a good result.
Solid timber requires at least one glue-up, bandsawing to size and a router template. This is not easy to do, certainly it is at least a moderate skill level to get right and doing it well is quite advanced, but it is quick and requires the least effort. Although far and away the weakest option, this does allow a lot of control over grain appearance. You will still end up with exposed end-grain so it may not be your best option for outdoors. See Tom Mclaughlin's adirondack chair though which uses this technique for the legs. I have made a pair of these and they are plenty strong enough.
Bent lamination requires a bending form the exact size of your finished curve, a complementary bending form pair and clamps. You need to be able to finish strips reasonably consistently - either a very good bandsaw blade or (preferably) plane or sand after cutting (I use a drum sander because that is the easiest option) This will be the fastest way to produce a finished product and is almost certainly the strongest option.
Steam bending requires the large bending form and at least a strap clamp to support the outside edge. There is some skill required to pick straight-grained clear wood (riven stock is preferred as this follows the grain) You can get good results with kiln dried wood and don't let anyone tell you otherwise. It's maybe a bit harder is all. I can't get air dried wood so have only ever used kiln dried.
You need to make your curve a little tighter than your finished project requires to allow for spring-back.
Softwoods are not usually recommended for steaming and I have never tried.
TBH I think you should try something new. Why not? A gate with a nice heavy top will look substantial and will work well aesthetically.
Steam bending would be fun, but it's frustrating. I don't think it's wise to start with a material that others say is not good for the job...
For me then, it's the bent lamination. Not easy, but easily achievable with effort and a lot of fun. Even if it does not go right, it's not much material and you have a high probability of a usable result.
Go for it!
I have done both on my boat rebuild. I steamed a lot of ribs and had to laminate several because the wood kept breaking trying to the the bend.
Of the two the laminated 'seemed' stronger. It was definitely more rigid. Of the two choices I would go with laminated. I find it easier and faster than steaming.
If you're routing a profile, laminations can show through. Sometimes its objectionable, sometimes not. Depends on color of wood and glue you use. Epoxy is clear, plastic resin brown.
In addition, you have to be a little choosy about the grain, not so much with laminations. OTOH laminations requires a good resaw set up and preferably a drum sander.
But, its a garden gate, personally I would do it the easiest way.
Hey, thanks everybody for the advice. One last thing, the "strength" I'm looking for is for the crown to resist lateral movement. The last door had a vertical crack along the grain, not at a glue joint but in the middle of a 2x6 panel. I thought a strong crown molding might help resist that kind of crack. Of course, the crown molding would also resist the tendency of the door to expand and contract widthwise as humidity changes, which is not a good thing.
Floating panels will help keep the boards from cracking. But if you have a long grain top cap fastened to end grain below, it will Crack for certain.
Thanks John. The door withstood 21 seasons, which is good for an outside door in my opinion. It isn't designed as frame and panel system. Even now, it still latches closed. But it's a little worn looking and termite eaten. The vertical panels expand and contract just fine with the weather. I think you're right about the top cap. It needs to expand and contract at its own rate and using it to reinforce the movement of the door itself is bound to fail.
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