plywood L girders

[Anonymous]

Hey all,
I was just wondering if anyone had ever tried making L girder benchwork out of plywood. I have access to a bunch of 3/4" plywood for free, and also a very nice fully equipped wood working shop of a friends. I was thinking of cutting the plywood into 4" and 2" strips and then milling out a slot in the middle of the 2" piece and gluing them up. The result would be a T shaped girder of 8' in length that i could then cut to length as i build my benchwork. Does this sound feasible, or does anyone see a downside i have not thought of. The plywood is free and so is the shop time. All it would cost is the glue and my time. Thanks in advance for the input from all.

[Anonymous]

You are almost describing an I-Joist except you would also include a bottom flange installed as you describe. The top & bottom flanges are a bit thicker, usually 2X3 or 2X4s and the web (the vertical portion) is usually OSB. You might double the top plywood flange so there is some meat left after you cut the slot, but likely is overkill. The bottom flange, which you are omitting, is to resist twisting which likely won't be a problem unless your benchwork will double as a dance floor.

Glue and secure with a few screws to hold while drying.

Make the web a bit deeper and you may be able to dance on it.

Wayne

[dehusman]

Using cut plywood for dimensional lumber is very common lately. I know several ers who use it. If the plywood is good it works fine. If it is rough and has a lot of voids in it isn't as good.

Dave H.

[nfmisso]

Overall, your plan is good. I would not bother with milling the slot, just glue and screw. The slot will not buy any strength or stiffness.

You do not mention what modeling scale you are using, or how much distance your inverted T will be spanning. 4" on edge is an incredibly strong structure, very similar to a 2 x 4 on edge. If you do not need the strength and stiffness, I would back it down to 3", and use 3" for both pieces, saving set up and cut time on the table saw.

I would also suggest build a jig to hold the two pieces aligned while you glue, drill the pilot holes for the screws and drive the screws. 1 5/8" screws, every sixteen inches or so, should be be fine.

[Anonymous]

Thanks for the info and input everyone. I think i'll do the 3" and 3" thing. I was only milling out the slot to help with keeping everything from bowing or flexing too much. It'll only take a few minutes to do and i figure it will be worth it. I think the way my benchwork is looking so far on paper the longest span i'll have is 4 feet. I still plan to make them 8' so i will have my options open. Thanks again.