Wood joint question (DIY Stand)

[M.E.Milz]

I am drawing up the plans for my stand for a new tank (78"x32"x36"). The basic design will comprise a frame made from 4"x4" lumber, covered with a skin of 3/4" ply.

At each of the 8 corners (4 top & bottom), I will be joining 3 separate 4"x4" pieces of lumber together (i.e., 1 vertical post and 2 horizontal beams, all at 90 degree angles to each other). Any suggestions on how to construct the strongest, most rigid joint? I do not have access to a router, and I do not want to merely bolt the things together. But I am willing to try an make some basic tongue and groove, or slotted-type, connections (anything that I can do with a drill, saw and wood chissel).

Thanks in advance, Mike

 

[Anonymous]

hi.
One of the strong joints that will work in your purpose is the following (I don't know the name...)

1, cut a 2X4 rectangular "hole" thru the vertical member.
2, cut the insert of one of the hort. member into a 2X4 cross section, 4 inch long. It will fit into the "hole" mention above.
3, put the above two pieces together, and cut a 2X2 square "hole" thru both pieces, perpendicular to the first "hole"
4, cut the insert of the second hort. member into a 2X2 cross section, 4 inch long. Insert it into the second "hole" mentioned above.

Now you have 3 interlocking pieces that you must remove in fixed order to take it apart, and very strong.

If anybody know what I am refering to above, please let me know the carpentry term for this particular joint. Thank you.

 

[Carpentersreef]

seven ephors,
The joint that you described is known as a mortise and tenon joint. It's an excellent joint, as long as it is tight.

Mike, as long as you secure the plywood and 4 x 4's securely, the joints will not be all that crucial. The 4 x 4's will give you the appropriate verticle support, and the plywood will be great for the lateral support (i.e., to prevent "racking" of the stand). The ideal situation would be to have the horizontal pieces resting on top of the vertical supports, and join the two horizontal peices together by cutting a 90 degree corner out of each equally, so that each horizontal member has the same bearing surface on the verticle post. Do not mitre it (45 degree cut), like a picture frame.
Be sure to screw or bolt the joint together. No nails.

My concern is with the support of a 4 x 4 spanning the length of the aquarium, acting as a header. Are you planning on placing additional verticle supports along the length, front and back? The 4 x 4 alone will not do it. The deflection will be too great.

Mitch

[ November 10, 2001: Message edited by: Carpentersreef ]</p>

 

[billzie]

Howdy Mike, sorry I missed you when you picked up the SD. I made my stand for a 125 6' tank in much the same manner as you're thinking. It's been several years ago now, and now that I'm thinking about it, can't quite remember how I made the corner joints (I won't be able to check until after Thanksgiving when I go back to Ohio). BUT, I used 4x4 in the corners, married 2x4 for the stringers, double 1/2" plywood for the top (in case I get an acrylic tank some day), 3/4" oak ply for the sheathing. Instead of using 4x4 in the middle I used 2x4 (I think). I made the stand so that the sheathing only reduced rake, not intending to be a structural device, you could plan your stand for the sheathing either way to omit additional center bracing (I checked my plan with an engineer I used to work with before I built it). If you can wait I'll check it out in Ohio when I go. Later, Bill

 

[Anonymous]

wow. the only thing i could add from my experience is to be sure you pre drill the screw holes on the 45 degree angles on your horizontals. i agree that the top horizontals should rest on the vertical. and even though you'll have plenty of meat on a 4x4, once those corners start splitting, it's a real pain in the a$$. HTH
chris

 

[FishGeeek]

Im board......Hope this helps

Brian

 

[cgbexec]

M.E.Milz,

I just recently built a stand for my 72" 125. I was going to use 2x4's and 2x6's and 3/4" plywood around the frame. Before I began construction, I consulted a professional carpenter and he advised me not to use any internal framing at all. We built the stand by building a 4 sided box out of 3/4" plywood and crib-jigging (This is a special devise that clamps on the plywood and allows a hole to be drilled at a perfect 45degree angle at a specific depth. Then a special screw is used to bring the joint tight. With this joint, all screws are on the inside of the joint, and the outside is clean. This only works with plywood at least 3/4" thick.) and glueing each corner. I used 4 2x6's on the top and 4 2x6's on the bottom going across to keep the front and back from bowing out and to maintain square. He explained to me that 3/4" plywood on end would easily support the weight of a fish tank of those dimentions. He builds stair cases for large homes, so he understands structural loading. We even cut two large doors out of the front leaving six inches on the top and six inches between the doors. I wanted to use a 2x6 over the doors and he explained again it was not needed. this tank has been running since march and no problems at all. I just wanted to let you know this can be done and allow for more space in the stand without all that framing.

 

[M.E.Milz]

Thanks for the replies and suggestions.

Mitch, I do plan to have vertical columns (4"x4") at the mid-point along the front and the back. Thus, I will end up with 6 vertical posts to carry the bulk of the load.

As for the horizontal members, I want to make sure they are beefy enough to carry the load to the vertical posts. I also want to make sure they will not deflect, otherwise they will force the tank itself (i.e., the glass side panels) to carry the load. The horizontal members will also provide reinforcing to the joint between the vertical and horizontal plywood panels (I do not have the skill/tools to build the "crib-jigging" joint that was suggested by cybexec).

Right now, I am undecided between using 4"x4" or 2"x6" lumber for the horizontal members. The 2"x6" should be just as stiff/strong, and will be easier to connect to the vertical posts. But it will force my doors to be smaller (I need enough room to get my sump into the stand). In any event, I will still need to connect 2 horizontal members to the vertical post at each corner.

seven ephors' suggested design sounds like the strongest, but will definitely be tricky to make.

Brian's mock-ups look good, but I need to figure out how to connect the 2nd horizontal member to each of the arrangements. But I have a few ideas how each of them could be altered.

Thanks again, Mike

 

[Larry Grenier]

For a non-engineer like me...

I found it very handy to go to a few pet stores and look very closely at how the stands are built.

Like cgbexec points-out, you'll find that there is suprisingly little frame in a wooden stand and the box itself is the support.

Just my $.02

 

[FishGeeek]

Sorry, I missed that you are putting together 3 4x4's. I would just cut the top four 4x4' at a 45 and bolt them together like a picture frame. then set that in top of the 4x4 leg's. You might want to check out and see what home depot has as far as fasteners go. Im sure in the deck hardware area they will have something for just this purpose.
Still board here is a pict.

HTH
Brian

 

[Osama]

Mike:
I would consider screwing the longer 2X4 runners to the top of the posts.
The heaviest load will be on the center posts. I would put a second post ( or a bracket/partial post)on the inside of the main external posts. Those internal posts will support the tranverse runners.

Another option would be to use 2X6 posts and 2X4 runners.
Let us know how it works out
Good luck with your new setup
Osama

 

[Osama]

Mike;
Take a look at the drawing from this site:
http://www.reefs.org/cgi-bin/ultimatebb.cgi?ubb=reply&f=4&t=000555

Creative Reefs DIY stand

 

[FishGeeek]

I think you posted the wrong link Osama.....

 

[Osama]

Sorry Mike ... Thanks FishGeeek
The site I came across is from another reading here @ reefs.org... Here is the site. I hope I can do it correctly this time
http://www.enter.net/~reef101/diystand.html

 

[M.E.Milz]

Update: I have decided to go with a tubular steel stand. It will be stronger and lighter than an all wood frame. It will also give me more room under the stand. The steel frame will still be covered with 3/4" plywood so that I can add doors, etc.

 

[KanUCme]

I used 2x4, 4X4, and just squared them up and Lag bolted them. But it doesn't matter cuz u changed course. O well... good luck.