Dowelmax

[rlkeeney]

Aquarium stands are a bit different than building furniture. The difference is in the failure. If a joint fails in a dresser or a chest you get a crack you have to repair or maybe a drawer that binds. If a joint fails in an aquarium stand you get 75 gallons of water, 150 pounds of gravel, broken glass and dead fish in your living room floor.

After looking at many aquarium stand builds in various forums one thing became very clear. The weight has to sit directly on the top of the legs. Letting the weight sit on a joint is flirting with disaster. Even sloppy builds work as long as you do this.

So no dowel joints for my aquarium stand.

[pennview]

I'm curious. If you rule out dowel joints for the aquarium stand, what joints would you use to build one?

[dusty]

I'm curious. If you rule out dowel joints for the aquarium stand, what joints would you use to build one?

If I was building something where I wanted "maximum joint strength", I would use dovetail joints. To maximize the strength of a good fitting dovetail, I would glue it]A sloppy fitting joint of any type is unreliable.

If dovetails are out of the question, I would use mortise and tenon joints and then I would pin them with dowels.


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[Ed in Tampa]

Aquarium stands are a bit different than building furniture. The difference is in the failure. If a joint fails in a dresser or a chest you get a crack you have to repair or maybe a drawer that binds. If a joint fails in an aquarium stand you get 75 gallons of water, 150 pounds of gravel, broken glass and dead fish in your living room floor.

After looking at many aquarium stand builds in various forums one thing became very clear. The weight has to sit directly on the top of the legs. Letting the weight sit on a joint is flirting with disaster. Even sloppy builds work as long as you do this.

So no dowel joints for my aquarium stand.

I disagree the shear strength of dowels is high. If they break it is usually by a lateral force that breaks the wood they are in or by twisting again usually the wood they are in is what gives up. I tend to overengineer things and a buddy of mine once joked I built an end table that could be used as a motor stand.
After many years of use it was time for the tables to move on. I just happened to have a motor so I set it upon the table expecting it to come crashing down. Nothing happened. I even put all my weight on the top. Still nothing.
Long story short the table was dowelled together and short of breaking out the wood that held the dowels I could not cause one dowel failure.

I my engineering methology is if the wood I'm using can handle the load and if I use the right number of dowels of the correct size the joint will be has strong as the wood itself. Correct number and size of the dowels is determined by using at least two and possibly four dowels per joint using the largest size that will still allow at 1/4 inch of solid wood all the way around

[rlkeeney]

I'm curious. If you rule out dowel joints for the aquarium stand, what joints would you use to build one?

Half lap or mortise and tenon arranged so the weight is supported on the legs and not on a fastener. Doubled 2x4 would also work well.

This isn't my design but it should give you an idea what I'm talking about.

[Ed in Tampa]

Half lap or mortise and tenon arranged so the weight is supported on the legs and not on a fastener. Doubled 2x4 would also work well.

This isn't my design but it should give you an idea what I'm talking about.

I agree that design is stronger than dowel joints but comes at a cost and that cost is looks and lumber. Will it ever fail probably not, but I contend something could be built using dowels to hold it together using a lot less lumber and perhaps looking a little more eloguent that would have the same probably of failure.

[pennview]

Personally, I think dowels are plenty strong, about the equal of a mortise and tenon, so I wouldn't worry about the joints coming apart. Besides, the dowels merely hold the structure together. The legs are what provides the actual support for all of the weight. More legs, equals more weight-carrying capacity. Putting joints on top of the legs only weakens the assembly. As Dusty suggested, dovetails and mortise and tenons with pins provide a fail-safe mechanism should the glue fail. Another good choice would be a bridal joint. The only thing I wouldn't use would be pocket screws. If I was really worried about it collapsing, I'd have one made out of steel and welded together.

[JPG]

Regardless of the material used, the necessary ingredient in supporting large loads is support!

Now if the intention is to support only from the bottom then the example above demonstrates that - solid material from load to floor(NO fasteners).

Same thing necessary with any structure - nails etc. do NOT carry the load, but merely hold in place.

Now with 'furniture' significant leeway is ok since the loads are light.

An aquarium is not a light load.

The parts providing containment(minimal side forces) can be anything that is capable of handling those forces.

IMHO blind dowels are more than adequate, but I like Dutsy's doweled M&T better. A blind doweled mortise might work.(resists outward force on both halves)

For supporting the vertical load, no fasteners. I would half lap horizontal support to the vertical support and M&T the sides to the ends as well.

Cover/enclose with 'furniture' material and joinery.

[tomsalwasser]

Berry, please check for a PM that I just sent you. Thanks!

Tom