What is the relative strength difference between (2) 1″ birch dowels joining a rail to a stile vs one biscuit? I think there was an article in FW some months ago about different jointing methods. Right off I know that the 2 dowels would be stronger but does take longer to make. The force on the joint is going to be a shear force as opposed to a bending force. Im joining 2 pieces of 3″ wide X 3/4″ poplar in, roughly speaking, a ladder arrangement to anothe piece of 3″ wide by 3/4 thick piece of poplar. The biscuits would save time but are they strong enough to support about 60 #…lest say a small child, climbing on the stiles? My gut feeling is live with the extra time and make it sturdy. However time is money too.
Wicked Decent Woodworks
(oldest woodworking shop in NH)
Rochester NH
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IIRC the article in question found that a biscuit joint was about the strength of a loose tenon joint and half that of a mortise and tenon. On the strength of that I have planned my next project to use biscuit joints and bought a jointer (176 biscuit joints to make).
However the test method was very specific for the type of stress applied so it probably does not apply to your case.
I would guess that the problem will not be when your construction is new but when what you are building has aged a bit and been subjected to forces which may loosen the joint. When (if) that happens a biscuit will slide out under shear when dowels may not.
Hope the thought exercise helps.
For a ladder I think I would rather have lap joints or through mortises. My grandkids (like most kids at one time or another?) will use a ladder for a launching pad and/or "the plank" or whatever is in vogue at the moment. Make it as sturdy as possible and pray that they will not be hurt too badly when they play rough with it or use it as their high dive.
If this is going to be a ladder - ie _intended_ for kids to climb - then I have to agree that the only way to go should be pinned M&Ts. I got the impression that it was _possible_ that kids would climb it.I say pinned joints because that way even if the tenons become loose the dowels will prevent them sliding out.Where children are concerned I have always over-engineered and am pleased to say that none of their multitudinous injuries have ever been attributable to a failure in something I built. (Playpen, cot, beds, swing, slide...)I am now in the blissful stage where the girls have grown and there are no grandchildren on the horizon yet, when the wheel will start turning again.
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