Lumber dimensions in wooden boat plans (a noob question)

So I'm looking at some of the free plans out of Popular Mechanix magazines and wonder, when these old plans with BOMs state x number of 2x4s, do they mean 2"x4" or do they mean standard 1.5"x3.5" lumber. Can someone clarify? What about NEW plans? Does 2x4 mean 2"x4"?

 

Good question! I can only tell you that 2x4s have been 1 1/2" x3 1/2" at least for the last 35 years that I have been a carpenter. I have done a lot of restoration work and the general time frame going back in time that I start seeing 2x4s that actually measure 2" x 4" is in the 1930's. They used to use the wording "actual" and "nominal" dimensions to diferentiate, perhaps you will find that or an abrieviation of same in your old plans.

 

I have seen it both ways in modern plans. At times the materials list will specify sizes predressed but the plans always show them the real size. If it is in a drawing ( and I know the Pop Mech ones are not to scale) it would of course be scalable.

 

They mean Home Depot 2 x 4s, the 1 1/2" x 3 1/2" size. I base this on the notion that Pop. Mechanics is geared for neophyte home builders and as such would expect home builders to interpret 2 x 4 as if he were reading a lumber list for a backyard shed.
The magazine may have included a note that "dimensional lumber" was being used as is. if not, they should have.
Often as not, drawing plans for a boat listing regular dimensional lumber for frames and so forth, the designer is working backwards to the way he usually woud work. He is starting with a frame size of a given dimension. It may be that the lumber used is really not exactly right for the job. Maybe it's a lot thicker than needed. The best frame dimension might be 1 1/4" x 2 3/4". Perhaps you own a table saw and wouldn't mind dressing the lumber. This is what is problematic with do-it-your-selfer plans. While the boat appears to "practically build itself" because it is designed around easy-to-find lumber store items, it may well be that the potential builder would rather use real gudgeons and pintles, for example, rather than zinc-plated eye bolts that aren't even welded closed, or spars that aren't made from closet poles.
You can certainly save money buying only lumber store items, but not so much as to reflect the much lower value of the finished product.
Your labor will be similar, and in most cases, it's the labor you value and not the savings of a few dollars, especially if the final result has potential for looking anywhere close to professionally made.
So many, many plans are available for fifty bucks, hundreds to choose from.
They are more complete too. You needn't guess what they mean by 2 x 4s either. If they say 2" x 4", it means that, and not 1 1/2" x 3 1/2".
A few guys have come into the forum with magazine plans under their arms.
My suggestion is you find some real complete plans and then, with the incredible backup you'll get here, build a boat that requires a table saw to build. Something with funny dimensions like 5/8" x 4 1/4".

Alan

 

Back when some of those plans were published I think the real size of a 2x4 was 1-5/8" x 3-5/8. That size came into being somewhere around 1923, but even then it varied on type of wood and locality. As far as I can tell, somewhere around 1963 is when a 2x4 became 1-1/2" x 3-1/2". (There is more info on the folowing site than you need to know)

http://www.fpl.fs.fed.us/documnts/misc/miscpub_6409.pdf

Reading some of these old plans shows your dilema. Older ones especially seem to mean actual dimensions, newer ones are sometimes hard to tell. If there are details with actual sizes listed, you should take that as an indication. If the BOM says 2x?, and the details shows 1-1/2"x?, that's one thing, if the detail shows 1-3/4" or 2"x?, that indicates they mean a real 2x?.

http://www.svensons.com/boat/

 

Many of these old plans and much of the free ones are not complete and have issues.

Most designers will mention "dimentional" lumber, meaning (as has been stated) the nominal dimentions of typical framming lumber. If in real doubt, see if you can scale it off the plans. If the drawn frame (for example) apears to be less then 2" or 4" on it's sided or molded edge, then you're working with dimentional lumber. On the other hand if the sided or molded dimention scales out very close to the dimentions indicated, it's milled stock and needs to be cut from bigger stuff.

 

2x 4 means just that. It is 2" x 4" but we DAR (dressed all round) the wood and it had ended up to the dressed size now.