My Little Pine Base Racks - Should I Be Concerned?

[onocoffee]

I've been working on a simple pine base for a long, narrow table I'm making. The top is a 1.5" white oak slab that is 18" to 20" wide and eight feet long.

I've built this base out of pine that is 28" high with 15" upper crossmembers and 18" feet. The stretcher is six feet long. And there's a little racking.

I'm cutting domino mortises in the cross member and stretcher to hold metal mounting thing-a-ma-jiggies that screw into the top. My first time making something like this. Do I need to worry about the racking? Will screwing the top to the base eliminate that? Should I add another stretcher? If so, where is ideal?

I'm including a photo of the assembled base and a video of the racking.

Thanks!

[attachimg=1]

 

[Cheese]

Is there a reason you chose to combine a pine base assembly with a white oak table top?

 

[onocoffee]

[member=44099]Cheese[/member] I like the pine look but also because I presumed it would be cheaper and easier to work with, and to get some chops in before I approach the taller bar height base for the other half of the slab.

 

[derekcohen]

I expect that table to rack and twist like Chubby Checker.

There is nothing to prevent the bases resisting back-and-forth movement.

Regards from Perth

Derek

 

[Packard]

Can you confirm either A or B below:

A.  The side to side racking is the result of looseness in the joinery.

B.  The side to side racking is the result of flexing of the pine pieces. 

It is not clear to me which is causing the flexing by watching the video. 

 

[onocoffee]

[member=74278]Packard[/member]

I just checked it. Looks to me that it's more flexing of the pine than loose joinery.

 

[Packard]

It it is the material that is flexing and not the joint (as Ono observed), then you need to do something to do something to add some more structure. 

Adding the top will not answer that problem.

I am not convinced that the stretcher will solve the problem.  It depends on where the flex is occurring.  Is it flexing at the joints at the top of the uprights? Or is is flexing because the uprights are flexing?

The absolute easiest way to resolve this issue is to attach it to the wall as some point.  That would make the wall integral to the structure. 

If that is not feasible then:

If the flex is at the joint, then adding two additional stretchers at the top should help.

If the legs themselves are flexing, then adding a stretcher about halfway from the floor to the top should help.

Or (my preference) use more robust timbers for the understructure. 

I think most people will have a sense of when the base structure looks over-built, under-built, or Goldilocks (“Just Right”) and you might ultimately be happier with the project if you used more heavy duty lumber for the understructure.

If you do that, perhaps you should move from a soft wood to a hard wood. 

In any case, the fastest and easiest would be to attach the top to the wall at some point. 

 

[Vtshopdog]

I expect that table to rack and twist like Chubby Checker.

There is nothing to prevent the bases resisting back-and-forth movement.

Regards from Perth

Derek

Plus one!

 

[peter halle]

I would expect to see a bottom stretcher in a design like that in order to counter the tendency to rack or wobble.

Peter

 

[Vtshopdog]

Maybe you could add some gussets at the joints if you want the svelte look of the design and don’t want to add stretcher(s)?

 

[Crazyraceguy]

That is always going to rack, without more support. The top won't do anything for it, but it will stiffen the stretchers on the long side (since the main center support is not centered)
With just 1 1/2" inches of width, the legs aren't doing much. Then that off-center rib is not touching them.
If that rib was centered and 2" taller, the whole thing would be considerably stiffer. As it is, pretty much the only thing that will help is a second beam, side to side, lower than the joint at the top of the leg.

 

[onocoffee]

Thank you all for the thoughts. I very much appreciate it.

[member=7493]Sparktrician[/member]  rang me up today with some ideas on a rectangular piece to butt up to the stretcher and then a triangular piece to run down the leg. Found out on my first go that the triangle was too small. My father stopped by and I let him decide the shape of a longer triangle piece that ran down the leg about 17". Much, much improved with no racking. Cleaned it up and gave it a coat of General High Performance Satin.

With jury duty tomorrow and maybe a trip to Kentucky to check out the Lie Nielsen event this weekend, I probably won't get to installing the base until next week. I'll follow up then!

View attachment 1View attachment 2

 

[Cheese]

[member=7493]Sparktrician[/member]  rang me up today with some ideas on a rectangular piece to butt up to the stretcher and then a triangular piece to run down the leg. Found out on my first go that the triangle was too small. My father stopped by and I let him decide the shape of a longer triangle piece that ran down the leg about 17". Much, much improved with no racking. Cleaned it up and gave it a coat of General High Performance Satin.

OMG...and I'm very definitely serious about this, where would we be on this forum without Sparky's input? He's been a great contributor over the many years and certainly has my heartfelt thanks. I've learned a lot from him...thank you.  [smile]

 

[Packard]

If those blocks stiffened the structure then it was the joinery that was flexing and not the lumber itself.

 

[Crazyraceguy]

That will absolutely do it, but it makes a huge visual statement at the same time.  [eek]
Some small-ish steel angle brackets could do the same thing and be nearly invisible.

 

[onocoffee]

The white oak top has been mounted to the Little Pine Base. No racking but there is a slight wobble because the bottom tenon on the right leg is a little loose. Going to shim it up tomorrow which should tighten it up. Going to use it for coffee tastings in my day job. Cut the 8 foot top from a 17 foot piece that I was going to use as one long bar top but it just didn't work in the space and accommodate what we want to do in the space.

Gotta finish sanding the now raw ends and then reseal with Waterlox.

Thanks for the help!

View attachment 1

 

[luvmytoolz]

[member=82312]onocoffee[/member] Nice work! Are you a competitive barista or roaster/producer?

 

[smorgasbord]

Sorry I'm late to the thread, but some thoughts for future builds:

1) The size of the big stretcher matters, specifically the top to bottom "width" or "height." The triangles you added make it wider/taller so that gives it more leverage to prevent racking.

2) The location of the big stretcher matters. The top location is worst - you've got the entire leg length acting as leverage on it. The middle is best, which shortens the effective lever arm of the legs on either side.

3) The joint of the big stretcher matters. Looks like you used a half-lap. That reduces the effect of #1 (above) to be half since only half of the stretcher's width/height is available to prevent racking. Better is to use a housed half lap or a bridle joint or things like tenoning the end and having the full perimeter cross-section of the stretcher available for shoulders.

4) The location of the big stretcher's joint matters. In your case, it's not located directly on the legs, but on the short horizontal stretchers. With good joinery of those stretchers to the legs, and good attachment of the top to those stretchers it may not matter as much, but it's not ideal practice.

Here's an example of a better joint for the stretcher than the half-lap:
[attachimg=1]

 

[onocoffee]

[member=82312]onocoffee[/member] Nice work! Are you a competitive barista or roaster/producer?

I guess I've been both (but not a producer).

In years past, I competed in the barista championships and won the US AeroPress Championship. Later, I judged barista championships and became one of the people who certified sanctioned championships across the world. But my day job has been running my own little coffee company that has done retail as well as roasting, wholesale and consulting. As part of my work roasting, I've worked with different producers in different regions to source nice quality coffee.

 

[onocoffee]

[member=77266]smorgasbord[/member] Thanks for the tips. I still have the other half of this slab to build a 38" bar with. If you recall the other plans I shared with the group, I'm thinking that's going to be next. Wanted to do this one first in an attempt to build skills.