#11
A carpenter brought me an unfinished project asking for help.  He has made a 5-foot wide arch of 3/4 white oak to fit in a church doorway.  He made the arch out of nine segments 4 inches wide and 12 inches long.   The butt joints have biscuit joinery.  He glued the segments together with yellow glue. Clamps are of no use on an arch, so he pressed the segments together as best he could.  When the glue was dry, each of the joints had a small gap he filled with wood putty.  It looks awful on what should be a quality job, so he asked me for help.


By using a heat lamp, all the joints have been pulled apart and the biscuits removed. The butt joints do fit nicely, so using biscuits again, the arch is ready to be re-glued. 

Here is my question: the endgrain on each piece looks shiny, because they soaked up the first glue.  What kind of glue will be best to use now.  Also, I will pull the joints tightly together using pocket hole screws on the back.  Thanks in advance.  —Peter
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#12
Lightly sand the glue on the ends, and use the same yellow glue since you have the joints fixed.
Steve

Missouri






 
The Revos apparently are designed to clamp railroad ties and pull together horrifically prepared joints
WaterlooMark 02/9/2020








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#13
(01-23-2023, 08:19 PM)Petertaylor Wrote: A carpenter brought me an unfinished project asking for help.  He has made a 5-foot wide arch of 3/4 white oak to fit in a church doorway.  He made the arch out of nine segments 4 inches wide and 12 inches long.   The butt joints have biscuit joinery.  He glued the segments together with yellow glue. Clamps are of no use on an arch, so he pressed the segments together as best he could.  When the glue was dry, each of the joints had a small gap he filled with wood putty.  It looks awful on what should be a quality job, so he asked me for help.


By using a heat lamp, all the joints have been pulled apart and the biscuits removed. The butt joints do fit nicely, so using biscuits again, the arch is ready to be re-glued. 

Here is my question: the endgrain on each piece looks shiny, because they soaked up the first glue.  What kind of glue will be best to use now.  Also, I will pull the joints tightly together using pocket hole screws on the back.  Thanks in advance.  —Peter

Biscuits were a bad idea from the beginning and still are.  They are great for alignment but don't add much strength, and with butt joints you need something more than a biscuit to hold parts like this together, just to move it, as well as over the decades it will be in service.  And now that the butt joint surfaces are contaminated with glue, it's critical, IMO.  

I would get rid of the biscuits and use Dominos, loose tenons, or several dowels.  The parts are short enough that any of those should be possible with proper fixturing.  OK, once you figure that out, you need to figure out how to clamp the parts together.  Pocket screws may, or may not pull the joints together.  I would do a test on some scrap cut to the same shape to find out.  The screws have to at the centerline to pull the joint together without a gap being pulled on the top or bottom.  I would do some tests on identical scrap pieces to see if you can make it work.  

I would put a spacer across the bottom of the arch to hold the bottom of the arch the correct distance apart.  I'd also make a template the exact profile of the inside of the arch so you know the arch is correct when you glue up the parts.  Screw the spacer to the center of the bottom of the template and add some spacers under the arch to put it at the centerline of the arch.  Or make two templates, one for each side of the arch pieces, with spacers in between, to provide fool proof support with no chance of twisting or tipping.  Then I'd use a couple of band clamps or ratchet straps around the arch to pull the glued joints together.  You could still use pocket screws with this approach, but they may not be necessary.  If the arch is going to have a door stop attached to it, you can screw through the centerline of where the door stop will be to pull the parts down onto the arch template.  In this case, I'd definitely make two templates and put spacers between them on each side of where the joints will meet.  Those will provide convenient screw locations.  

Glue.  I'd use epoxy because it has a long working time, will fill any little gaps, and is waterproof and stable over a wide range of temperature, as it will see in service if it's an exterior door (although it's probably not if it's only 4" wide.  I'd still use epoxy for the other benefits.    

Bonus points.  If despite your best efforts, there are unacceptable gaps, you could glue a sheet of veneer to both sides of the arch.  It will cover the joints, and also provide some strength if you use shop sawn veneer.  

The carpenter should never have taken on this project.  It would be a non-issue for a millwork shop.      

Good luck.  

John
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#14
Thank you for the extended suggestions, John. Your thoughtful answers and comments to everyone are always interesting much appreciated.  Loose tenons and epoxy it will be.  —Peter
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#15
John got it right.

As for clamping, loose tenons or dowels will make the job a lot easier. You could possibly get away with just two to at the most four long clamps.

Try all you can to clean up the glue surfaces first. Scraping is what many prof restorers do.

Simon
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#16
Clamping pressure that goes perpendicular across the butt end of the joints is going to be a challenge.

I don't have a band clamp that would be suitable for that size project.

The concept in this Wood Whisperer video might be worth adapting for the job.  I have used this same idea for clamping non-45 degree miters on flag cases (much smaller than your project) but I think it would scale up well.  I've also seen variations used by other woodworkers on TV.
Ray
(formerly "WxMan")
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#17
I may be having a challenge visualizing this.

If I have this right, the arch will be installed in a 5' wide doorway.

The cross-section of the arch is 3/4"x4"

The arc length (probably bottom point to bottom point aka the inner arc) is 9'

Will the arch be painted or will there be an attempt to deal with areas of oak that will not absorb finish (saturated with glue, for example)?

Is there a numerology significance to the nine segments?

If it is to be a natural finish, numerology is not an issue, and there is nothing special about the history of the current 9 pieces; then you might want to consider the suggestion above to (essentially) make a bending frame and then use thin strips the full length of the arch to laminate the arch.

This is like laminating the rockers for a rocking chair.

It means the expense of building the bending frame and the cost of a long piece of oak, but it should give you a beautiful arch that will hold up to years of kids jumping up and slapping the arch as they go through the doorway.
"the most important safety feature on any tool is the one between your ears." - Ken Vick

A wish for you all:  May you keep buying green bananas.
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#18
Since people were helpful of curious, here is what I did.
As a support, I cut a similar 6-foot arch from plywood.  This would allow me to clamp down each of the nine oak segments and to move and glue them as needed.

The butt ends of the nine segments had slots for biscuits, so I cut 3/8 deep slots in each by running them over the table saw. Loose tenons were made to tie the ends together.  The segments are four inches wide, so two pocket holes were drilled into the backside of each end. I used epoxy but didn’t try to glue all at once; every other arc was glued first and the pocket hole screws pulled them up tightly. Then the now-longer arcs were glued to complete the 6-foot arch. Everything turned out well.  The arch, still clamped to the plywood support, it is now ready to go back to the carpenter.

But I had an odd experience with the epoxy.  Bought several packs labeled as 5-minute open time.  The first one had more like 20 minutes before it began to firm up.  Okay, fine.  The second pack, same brand, got hot even as it was being mixed and was semi-firm before it could be applied! Went back to the stre for a different brand.  

I assume this topic is now closed.  —Peter
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#19
(01-25-2023, 06:46 PM)Petertaylor Wrote: But I had an odd experience with the epoxy.  Bought several packs labeled as 5-minute open time.  The first one had more like 20 minutes before it began to firm up.  Okay, fine.  The second pack, same brand, got hot even as it was being mixed and was semi-firm before it could be applied! Went back to the stre for a different brand.  

Thanks for the update. It sounds like things worked out.

I would be curious about the brand of epoxy that gave you such disparate results.
"the most important safety feature on any tool is the one between your ears." - Ken Vick

A wish for you all:  May you keep buying green bananas.
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