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Thick or Thin?2/19
A poster in another forum mentioned he had some 5/8" thick panels to edge glue together for use in an exterior door. He will "double" the panels - back to back. The retention molding can be removed and the panels replaced - a good design when you can do it.
So, the 5/8" triggered an old quandary. As I read the 5/8", I winced - "too thin" the left brain said. "Why" said the right brain. "5/8" is so thin, there is so little to hold it together - especially at the edges where the panel raise is" said the left hemisphere. "So 1-1/4" is more likely to stay together than two at 5/8" ? Why? The right said, a little short.
I went off and paid some bills and looked at truck leases, but the small battle raged on. The bulk of my reasoning for thicker panels comes from a root truth: Wood glues together because of surface area. The more surface that is bonded to another surface, the stronger the joint. Nice and logical - just the way the left brain likes it.
But 5/8" butted to 5/8" maximizes the available wood, correct? (without resorting to glue joint cutters, splines, etc.).
As a result, and to quiet the voices in my head, I just make my panels as thick as I can, butted for width. I've had them fail due to glue failure (TBIII and heat), but not for any other reason I can find.
So, is our friend going to be OK with those thin panels? Should he change to 1-1/4" or so to avoid costly panel splits? Do I need to be obsessive about something else? Granted he is an adult, and appears to be of sound mind, so he can do whatever he wants since he will accept the repercussions of his decision.
I was just hoping to save him some trouble if I could. Well, actually, my right brain wished him well. My left brain did also, but over in that odd little competitive corner it was quietly hoping for failure so it could enjoy an 'I told you so' moment. I'm glad we do not have three lobes for brains.
1st time I have heard thesis, antithesis, synthesis done by one person.
So what is the synthesis?
David, thank you for clarifying that I am not the only one who succumbs to this level of insanity.
Pat, I suppose that the synthesis is "Better him than me."
If one believes that a glue joint, properly done, is stronger than the wood itself, then you have what you have. I don't remember the post; are these panels being glued back to back, or installed loose?
Perhaps he can hope for an exterior door location with a covered porch, the saving grace of many an exterior door.
The big difference as I see it comes if the panel side edges bind in the slots. This could be from paint working its way in during the finishing process, or glue during assembly.
In that case the thicker panel will be more likely to pull free while the thinner panel will be more likely to split.
Thinking further (as inspired by David) I want to say that the thinner panel is more likely to cup due to both the thinness and the back being less exposed to moisture. However I'm not convinced of this so will let the two sides of my brain fight it out.
The OP is Harold Pomeroy in the Glue Forum. His panels were to be back to back, but I assume not glued, since the point of the back to back is to let one panel move independently of the other.
I agree with B H Davis on the likelihood of the thin panel cupping, but then it can't because it is restrained on 5 sides (more material with which to obsess). It could bow out, away from the other panel, but only to the extent the retention groove in the perimeter would allow. But bowing out would be what one would expect to see if that panel, and that panel side was picking up moisture.
So - is one better off with two 5/8" panels or one 1-1/4" panel? "Better off" means "Is more likely to not break a glue line or split".
We work to put our solid wood panels into tight grooves. Squeaky tight. The bigger panels require some big beam clamps to pull it all together. We have had no panel splits since the TBIII debacle.
It may be a moot point. We now prefer a 7 ply panel that solves all the problems, but increases costs. We are also now experimenting with a 'framed' panel - man made board core, with a solid perimeter, then cross band and face veneers both sides, then raised. It will also be expensive, should we adopt it.
A secondary problem (obsessive results...) is that this raises the price of our doors to out of our nice little McMansion market. The builders and homeowners don't care about longevity and quality except in passing. It much more about image and grandeur than quality (however one measures it). Most of my projects sprout a for sale sign in 5 years, and sell at 15% higher price than what it was built for. We will have to market (?) our work to a wider geographical area, and slightly different buyer. This I know nothing about. I do know there are many people that would buy our doors, if they only knew we existed.
Stop me when I'm mumbling......
I’m sure that you build a nice door, and sharing your thoughts, processes, successes, and failures with this forum is a benefit to all who read it. Perhaps you might be over thinking this, unless you want to put blind dovetailed keys on the backs of the 5/8” panels to connect them, so that they would stay attached to one another and still allow for movement. Then you would really be over thinking it.
When you previously talked about your 7 layer panel and epoxy, I found this to be a very good solution to an age old problem. And yet it sounds like an expensive and time consuming way to fabricate a door whose quality seems to be more of a concern to you than to your customer.
I haven’t built many exterior doors, primarily because the customer and their contractors generally do not want to do what is required to ensure the longevity of the product, and will then see the millworker as the reason for door failure, if there is one. If you don’t finish, hardware, and install your own doors, or trust those who do, then what I see as an integral part of ensuring your products longevity is out of your hands.
Nature eventually wins the battle of the exterior door, and I suppose the cynic would ask whether you should fight that battle until the check clears, or until the house flips, or until your door is the last thing in the house that the termites eat.
Without getting into a “Zen and the Art of Motorcycle Maintenance” stream of consciousness about quality, one does one’s best to provide the finest product that one can at the price point that people are willing to pay. If you have a solution that works, then your work is done. If a forum member chooses not to follow your advice, then that is their problem and not yours. I would not think that it is incumbent upon you to chase down their methods to determine if they are theoretically plausible. Too much second guessing makes for bad Karma.
As for looking to expand your market, I suppose as is my nature, I have more questions than answers. How many more doors than you already sell do you want to sell? Can you maintain the quality at that production level? Are you going to delude yourself into thinking that, without serious money, machinery and space, economy of scale will allow you to significantly reduce costs? Where will you get the additional craftsmen to make more doors? Are you going to become one of the Six Sigma guys, and hire an MBA who knows nothing about millwork to “fine tune” your operation for you, all so that you can make more doors?
I envision your shop becoming a scene out of Chaplin’s “Modern Times”, which may not be what you want as you try to talk yourself into retiring.
For what it’s worth.
I've only built a few house doors, but have used 5/8" thick panels, back to back, on all of them with one exception. Back to back panels allows me the freedom to use different woods inside and out.
The panels are a single board wide, no glued joints, and never more than 13" wide. I haven't been faced with a customer yet that insisted on full width panels but if I am and can't talk them out of it I'll use a veneered composite panel similar to what you described.
I've never had any problems with the panels, even though one door faces due West with no protection. I'll give a plug for Cetol Door and Window finish here, because that's what's on that door and it looks great 3 years in. I attribute the stability of the panels to being a single piece and no more than 13" wide, being finished on all sides and edges, and maybe shear luck. The panels are captured in moldings so they can be removed for finish maintenance or replacement if ever needed.
Thank you all for your musings.
The reason I am doing this is to match existing doors, probably built in the 1920's. I will be matching the moldings and construction, because that is the architect's intent. The original work was well built and high style, on a public building. I haven't gotten the existing doors into my shop yet, but I'm curios to see if the panels were glued up.
The new doors are many feet away from a porch roof line, north facing, and up a flight of stairs from the ground. The building maintenance is very good, judging from the way the rest of the place is kept up. I will be gluing up vertical grain wood to make the very wide panels. The finish will be good paint.
If I were designing new doors and not matching existing, I would make thicker panels, make them back to back, and add some mid stiles to make the panels narrow enough to be vertical grain Douglas Fir. I would also anchor them in a plough. The panel molding system was protected by lead paint, and that worked better at protecting wood (and poisoning people) than modern paints.