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Discussion Starter · #1 · (Edited)
I sure hope I can get some help here. I am making an Ipe bench. It is 1½ thick - the top and three legs. Bench top is 23” wide and. 83” long. I used my router to create three mortises, and when I dry fit the legs there is a little wiggle. The depth of the mortise is ⅝”.
Question 1: is ⅝ deep enough?
Question 2: I was planning to use System Three #2 general purpose epoxy to attach the legs. I was told wood glue was not the right choice.
Any tips on applying the epoxy in the mortise? Will it hold the legs?
Will the epoxy squish up and fill the small gaps on the sides?

thanks in advance for any suggestions.
pictures should help.

BJ


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Yes. The epoxy will hold it. I would use tape on the edges to make squeeze out easier to clean up and keep it off of the surrounding surface. Also, I would thicken the epoxy some with one of the thickening agents the company sells or just use some fine sanding dust to make the epoxy about the consistency of peanut butter. This will make the epoxy stronger where it has to fill gaps.

One other point. I recommend that you make stretchers between the legs. This will stiffen up the structure and help prevent racking under load. Otherwise, you joints are going to undergo a lot of stress and may fail early.
 

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Generally epoxy isn't a good adhesive for Ipe. The wood has natural oils in it which epoxy would have difficulty getting a bite on. In your situation though epoxy is probably the best choice since it would fill the gap. There are thicker epoxy glue which are more like a paste which might work better when working with a gap. If you could use some kind of mechanical fasteners too that would help.
 

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Discussion Starter · #4 ·
Yes. The epoxy will hold it. I would use tape on the edges to make squeeze out easier to clean up and keep it off of the surrounding surface. Also, I would thicken the epoxy some with one of the thickening agents the company sells or just use some fine sanding dust to make the epoxy about the consistency of peanut butter. This will make the epoxy stronger where it has to fill gaps.

One other point. I recommend that you make stretchers between the legs. This will stiffen up the structure and help prevent racking under load. Otherwise, you joints are going to undergo a lot of stress and may fail early.
Thank you Bill for your advice. I did save some fine particle Ipe sawdust from sanding and I will mix it with the epoxy. Tape - the green or blue tape or does it matter? The legs are 20lbs each! The top is around 100. When the person who requested I make this for her showed me a picture of what she wanted it did not have a stretcher. And, there are three legs, not two. Do you think that matters in terms of strength?
 

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Discussion Starter · #5 ·
Generally epoxy isn't a good adhesive for Ipe. The wood has natural oils in it which epoxy would have difficulty getting a bite on. In your situation though epoxy is probably the best choice since it would fill the gap. There are thicker epoxy glue which are more like a paste which might work better when working with a gap. If you could use some kind of mechanical fasteners too that would help.

Steve, thanks! I did read to treat the mortise and the end of the leg with acetone first to remove some of the oiliness. Will that be enough?
What kind of mechanical fasteners are you suggesting?
 

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With oily woods such as Ipe or teak, wipe down with acetone or lacquer thinner just prior to 'glue-up' and you should be just fine.
 

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A single brace or rib down the center will make the bench much more stable. This would be barely visible if it were 3" to 4" wide and 1.5" or 2" thick. It could be mortised into the legs by 1/4" or so. It would be in two pieces, between the ends and center legs. You are already asking the epoxy to fill the gaps which makes it a "structural" member as well as an adhesive. That may or may not endure over time? The brace will be a structural member making the joint more reliable.
That design would work well in welded metal, but wood is not nearly as strong.
 
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I only use West System epoxy systems. Been using it for over 40 years. Their product line is quite extensive.
They make several different fillers for different applications. Some are for more strength and some are for less strength where filleting and fairing and sanding may be necessary. If you do a lot of repair work, it is worth knowing about this stuff. Especially about fillers.
Their technical data sheets give setup time vs temperature. You can set your watch by it.
BTW, their tech support people are on top of their game.
 

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Discussion Starter · #9 ·
A single brace or rib down the center will make the bench much more stable. This would be barely visible if it were 3" to 4" wide and 1.5" or 2" thick. It could be mortised into the legs by 1/4" or so. It would be in two pieces, between the ends and center legs. You are already asking the epoxy to fill the gaps which makes it a "structural" member as well as an adhesive. That may or may not endure over time? The brace will be a structural member making the joint more reliable.
That design would work well in welded metal, but wood is not nearly as strong.
I’m trying to picture the single brace idea. Being pretty new and this being my first attempt at mortises and routing, I’m a bit confused. So it’s two pieces? What is meant by the ¼” into the legs? Is there a picture of this you could add? Thanks
 

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Discussion Starter · #10 ·
I only use West System epoxy systems. Been using it for over 40 years. Their product line is quite extensive.
They make several different fillers for different applications. Some are for more strength and some are for less strength where filleting and fairing and sanding may be necessary. If you do a lot of repair work, it is worth knowing about this stuff. Especially about fillers.
Their technical data sheets give setup time vs temperature. You can set your watch by it.
BTW, their tech support people are on top of their game.
West better than System Three? I have no allegiance to them, just what they suggested at woodcraft.
 

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I agree with the comments about epoxy and bracing. As @Tony B mentioned, wipe down with acetone right before gluing.

IMO 5/8" is deep enough, but only if you add some bracing. That could be a 2x6 board running between the legs, an apron, a stout steel angle brace. Unless you're fastening the bench to a wall you need to do something or its going to rack with any type of sideways force.

System 3 is just as good as West, other than maybe a shorter open time and its thicker. For joinery I use the West in the pump cans. I recommend using a thickener or wood dough.

There are a couple ways to tighten the fit, one is is glue material to the tenon and resize it, the other is insert veneer in to the mortise. But epoxy is a good gap filling glue, to you may not need anything.

I heard that Weldwood plastic resin glue has been discontinued by the manufacturer? Is this true?
 

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I agree with the comments about epoxy and bracing. As @Tony B mentioned, wipe down with acetone right before gluing.

IMO 5/8" is deep enough, but only if you add some bracing. That could be a 2x6 board running between the legs, an apron, a stout steel angle brace. Unless you're fastening the bench to a wall you need to do something or its going to rack with any type of sideways force.

System 3 is just as good as West, other than maybe a shorter open time and its thicker. For joinery I use the West in the pump cans. I recommend using a thickener or wood dough.

There are a couple ways to tighten the fit, one is is glue material to the tenon and resize it, the other is insert veneer in to the mortise. But epoxy is a good gap filling glue, to you may not need anything.

I heard that Weldwood plastic resin glue has been discontinued by the manufacturer? Is this true?
Thank you Robert. Where can I find pictures that will show what the bracing would look like? I’d sure like to finish this!
I don’t understand. Doe this mean I need to make a mortise in each leg to put the brace wood through? I’m picturing the mortise in the center of each leg, running vertically, and the brace going through the leg slots, a little short of the length of the top. So maybe a piece 77” long, going through all legs at glued on. Does that sound right?
 

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A single brace or rib down the center will make the bench much more stable. This would be barely visible if it were 3" to 4" wide and 1.5" or 2" thick. It could be mortised into the legs by 1/4" or so. It would be in two pieces, between the ends and center legs. You are already asking the epoxy to fill the gaps which makes it a "structural" member as well as an adhesive. That may or may not endure over time? The brace will be a structural member making the joint more reliable.
That design would work well in welded metal, but wood is not nearly as strong.
OK, here's a sketch of the center rib between the outside and middle legs. A mortise into both legs will strengthen the joint considerably.
Rectangle Sleeve Font Slope Triangle
 

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So is it two separate braces or one long one?
It can be either. What you are trying to do is attach the legs together so the force on one is carried over to all of them, 2X more resistance.
If you use one, then the center one will not have the strength/resistance of having two separate ones.
 

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Thank you Robert. Where can I find pictures that will show what the bracing would look like? I’d sure like to finish this!
I don’t understand. Doe this mean I need to make a mortise in each leg to put the brace wood through? I’m picturing the mortise in the center of each leg, running vertically, and the brace going through the leg slots, a little short of the length of the top. So maybe a piece 77” long, going through all legs at glued on. Does that sound right?
WNT illustrates pretty much what I’m talking about. A mortise is ok except I think you would still need fasteners.

My thought was to just butt them and use screws. The ends can be “toe screwed” from the inside so they don’t show.
 

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I think wnt did a lot of drawing at work
Very nice representation (y)
Not actually. I did take architectural drawing in high school. I also took some drawing classes in college, drafting, and figure drawing, and design drawing with sketches.
We were taught a very technical approach to perspective drawing, orthopedic projection. We even projected "shades and shadows" on those drawings!
At work there were "illustrators and designers". The illustrators could make a rendering look so real with reflections in the chrome and the paint. The designers were more focused on the shape and lines on the cars. I did some design work when I started there, but changed my career path to clay modeling or sculpture where I remained for 25 years. I was a far better sculptor than a designer. My design skills were OK. but no match for the best automotive designers in the business.
 
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