Tolerance: what is close enough?

[DavidF]

I'm spending a pleasant Labor Day in the shop making floor timbers for my Folkboat. I have the old floors to use as templates but they came out in pieces (badly rotted). The new floor timber does not fit perfectly flush on all angles. But then the other yet-to-be-removed floors don't fit tight either. The new timber is well-seasoned white oak. The planking is larch, some of which will be replaced. The boat has been dry for years.

The old oak and the new oak and the old larch and the new larch will all swell at different rates. Right now the gaps are as large as 1/4" but most of it is within an 1/8". How close is close enough?

[Jay Greer]

Where fastenings will be attaching frames to floors and planking fays to the molded sides of the floors I like a wood to wood fit. This also holds true for the landing on the keel. Rubbing chalk on the surfaces that the floor will fit to will allow you to see the high spots and shave the floor for a better fit. In cases where floors are only attached to the keel and frames, although I prefer not to, some sloppy builders leave a gap between the floor and planking. I look upon this as a place for dirt to collect. I also fasten my planking to the floors. Avoid drilling new holes in the frames as this will weaken them. Better to drill through the old holes into the new floor.
Jay

[donald branscom]

I like to make exact patterns. I use small sticks(screen door molding) is what the lumber yard calls it and a HOT GLUE gun.

I make my pattern in place and the carefully remove it, and trace it onto the wood i will be cutting it out of. Always a perfect fit.

[Rich VanValkenburg]

I know this is off-topic, but your heading reminded me of my two BIL's, one uses a micrometer, the other uses a yardstick. They were iron workers for many years. It's "rumored" that the Detroit Tigers scoreboard at Comerica park is 30 feet out of place. The cement guys pouring the footings maybe used a bigger yardstick? Both guys worked on that place so it can't be their fault.:rolleyes:

When I replaced Sonja's floors I made sure they were a wood to wood fit, just as Jay said. I know there's some strain on them since the top nuts and washers are being sucked down into the white oak, but only by about 1/16 inch. I think this is where your concern is, right?

Rich

[DavidF]

Thanks. Yes, my concern is that when things get wet, things might expand too much and pry things apart. Right now there is a great deal of space between the old floor timbers and the planks. This might be from shrinkage from drying or maybe the wood is so worn out it is distorted. If I am to make it tight, then I ignore the old floors and do not use them as templates.

[Chan]

I had a framing company 10 years ago, we built highend homes. My motto, on the card, was,"when close enough isn't"
Anybody saying close enough was instantly terminated.
Close enough just need not be when it it can be right on!









'when close enough just isn't
'


'

[Rich VanValkenburg]

I think what I would do is to pull one of those floors out and put it in a bucket of water for at least three weeks. Change the water every few days to keep green stuff from stinking up the place. Measure it before and then after. If there's any life left in the wood, it'll swell to near original. That would be the time to check it against the planks. Is there space between the frames and planks? Most likely not. I've learned that dried lumber isn't the best thing to use down there where it gets wet often.

Somewhere in here I've seen photos of Ed Harrow's floors and he had some space in there. I think he'd be of some help here. And I think Margo replaced some or most of Sarah's.

Rich

[DavidF]

Sorry, but there is such a thing as close enough. I worked with a guy framing houses and he was looking a 1/32nds and taking forever. The boss screamed at him, "You're not building pianos!" There is a place where efficiency counts. I don't know about other people here but I can't afford to live in a house made by people who believe there is such a thing as a perfect fit and that every joint is tighter than you know what.

But more to the point, my question had to do with how much play should be built into a floor timber to account for the swelling of wood? Should I keep to the original measurements or do I redesign the new floor timbers to reflect the new sagging dimensions of the boat?

[George Ray]

In a loosely fitted joint you are depending on the fastening to carry the load and because things are LOOSE the structure will wiggle and move and the fastenings will flex and fatigue. It is seldom an issue that causes a problem in a house or other stationary structures but ON A BOAT? Do you want to spent three days in the 'perfect storm' being pounded and rolled and bashed knowing that the screws holding the garboard plank on are flexing back and forth and back and forth?

In a very well fitted joint the fastening has little work to do and that is a good thing.

[Mrleft8]

Clearly I seem to be in the minority here, but.... In my experience Dry wood fitted to dry wood, tight like a piano will end up sloppy after the wood swells and then relaxes a bit. Ofcourse there's no real way to figure out the exact amount of swellage, so it's seat of the pants close your eyes and jump kind of woodwork.
One day, as I struggled for an invisible joint for hours on end Jim Krenov sat down next to me, looked at the offending joint and said:"That looks pretty good. It's not a damned piano you know!". Sometimes, especially in boat construction, "close" IS close enough.

[George Ray]

You make a good point that it is important to know 'what is good enough', and not to be paralyzed by perfection. As to joints opening up that is certainly the case to an extent but you make it sound like seeing daylight though the gaps and having cracks that fill up with moisture holding dirty glop are the norm on a well built boat. The handful of well built wooden yachts and fishing boats I have had the pleasure to see naked and exposed in their private places seldom had gaps that a thin nail file would slide into and joints were usually bedded in something be it thick bedding compound or just a thick coat of red lead primer. Part of it is how long you hope the item to last. If it will pay for itself and be retired to the knackers yard in under 10 years then 'quick and dirty' makes sense.

[Chan]

As soon as good enough becomes good enough the quality of the work detioriates rapidly. 1/16 " gaps become 1/8 to 1/4" gaps, "spooge will fill anything". Spooge costs more than tight fits!
Everytime time you have to fill 1/4 " gaps with epoxy and filler that's 3 more pumps on the resin and the hardner, then sanding all that squooge.
In house framing every 1/16" gap in wall plates in a 100' house adds up to a wall 3/8" out of plumb. If that's something you can live with or expect I guess I'm not your framer.

[Ron Williamson]

Chan
How do you manage crowned lumber?
I would say 'good enough' just to piss you off.
R

[Mrleft8]

As soon as good enough becomes good enough the quality of the work detioriates rapidly. 1/16 " gaps become 1/8 to 1/4" gaps, "spooge will fill anything". Spooge costs more than tight fits!
Everytime time you have to fill 1/4 " gaps with epoxy and filler that's 3 more pumps on the resin and the hardner, then sanding all that squooge.
In house framing every 1/16" gap in wall plates in a 100' house adds up to a wall 3/8" out of plumb. If that's something you can live with or expect I guess I'm not your framer. If you're framing houses and worrying about 1/16" you're either a boutique carpenter, or an unemployed carpenter. House framing shrinks 1/16" between the time you nail it together in the morning, and lunch.
I'm not, obviously, promoting sloppy work, but rather "realistic work".
If you want to be a 1/64" kinda guy, fine, but in 99 out of 100 cases it's not necessary.

[DavidF]

I can see how you want the tightest fit imaginable in a cabin roof to keep out the water. But there are cases where it isn't important (framing a straw bale house) and some cases where a bit of play is important (a door frame needs a gap or the door won't open.)

I am concerned that the swelling wood would do something like push the garboards away from the keelson. Not a single floor touches now and the boat lasted 50 years. One reason I posed the question is I have been told to not tighten keel bolts until the boat has taken up. This must mean, if it is correct advice, that floor timbers swell a fair bit.

[George Ray]

Floor timber/plank gaps like the ones in this boat from year 42AD and recently uncovered?
http://www2.rgzm.de/Navis/Ships/Ship052/Image/052F0061.jpg
http://www2.rgzm.de/Navis/Ships/Ship052/Fiumicino2Engl.htm

Intentionally making floor timbers a loose fit against planking is a new on to me. Understand concern about swelling but do consider the moisture behavior of wood. I pulled this from goggle and can't speak to the absolute accuracy of the numbers but it seems ballpark at least.
A good rule of thumb: When bone-dry wood gets soaking wet, it swells 8 % in the direction of the annular rings (tangentially to the trunk), 4 % radially to the trunk and not at all lengthwise. And shrinks with the same percentages when drying through the same moisture scale.
http://www.gsahv.pp.fi/wood/wood3.htm

So a floor timber made with consideration to the grain may get a bit thicker fore/aft but won't push on planks to speak of.

[Emma56]

When No light will pass through the joint:eek:

[George Roberts]

If you need our approval for the tolerances, you are out of luck. Most of us are intolerant.

I suspect 1/4" gap will suck up small parts that you drop. But 3/8" is close enough for me - puts your work in tolerance.

[Chan]

Mr left I've been making a decent living framing houses on a contract basis for 30 years, that means I compete with all the hackers in terms of price. The first tool out of my van is not a sawzall as is the case with most of the hackers. Do it right the first time is far more efficient and economical.
It doesn't take any longer to do it right the first time, takes quite abit longer to do it wrong then fix it.

[Chan]

Ron
Crowned lumber? In a floor joist or a rafter for the most part framing 16" on center the sheet goods and some wieght will straighten it out.
If I don't feel that's the case I send it back to the lumber yard.
My current project a 4500 sq ft house has a pile of lumber ready to be sent back to be mixed in for the framer and home owner who don't mind cracked drywall crooked trim and shimmed cabinets.

[Chan]

ps Ron
The really crowned stuff goes in the back of my van for future deck and coach roof beams.