Suitable for planking??

[mattyg]

I am in the intial stages of the restoration of a 1930's 6.4 KR. She has been GRP sheathed since 1974 and to present, the major work has been the stripping of this vile stuff. Not too surprisingly the glass has been covering a lot of problems and I am going to need a good few planks. I have seen for sale some 3inch think mahogany that is apparently from an old church floor. It is free of fastener holes. This wood is likely to be 100 + years old. My planking is fairly thin, about 15mm and so I could potentially get 3planks out of the one. My question really is whether given the maturity of this wood, it would be suitable for the purpose. It will presumably be very dry (as in deed is the boats planking, or at least the non-rotten bits). Any help appreciated.

[Tar Devil]

Not my area of expertise.

Wait a minute... I have no areas of expertise.

In that case, can I see a picture of your boat?

(Someone with real experience will be along shortly, mattyg! Meanwhile, you might wanna mention what kind of planking is currently on the boat and give us a better idea of how much needs replacing.)

[SchoonerRat]

Assuming your existing planking is mahogany (you should repair with the same wood as the rest of your planking), be warned that there are a number of woods passed off as mahogany. Of these, only real mahogany is suitable. Judging by the age of the wood, you should be OK, but best to check.

[SchoonerRat]

Wait a minute... I have no areas of expertise.

In that case, can I see a picture of your boat?

Give yourself some credit, Devil, you are certainly expert at asking for pics .

[mattyg]

Hopefully a picture for Tar Devil. Yes she is mahogany on oak.

[Dave R]

Looks like you've got your work cut out for you. That's some mast you've got there but I think there's too much rake.

Where are the experts?

[Tar Devil]

Thanks for the pic!

Ayep... that's a project alright!

[Bob Smalser]

....I am going to need a good few planks.

I have seen for sale some 3inch think mahogany that is apparently from an old church floor. It is free of fastener holes.

This wood is likely to be 100 + years old. My planking is fairly thin, about 15mm and so I could potentially get 3planks out of the one.

My question really is whether given the maturity of this wood, it would be suitable for the purpose. It will presumably be very dry (as in deed is the boats planking, or at least the non-rotten bits).

Tough job. But I think yours is the right approach.

I take it you are in the UK. Are you sure the original planking is mahogany? Looks like it from here as I don't see the growth rings that would be evident in larch or fir. The species used for replacement planks should be close in seasonal stability to the originals. For instance a Longleaf Pine replacement plank in a mahogany hull might crush its neighbors because it expands to a greater degree with increased humidity.



Did it have had a stem repair during its life? Or are what looks to be short planks just glue stains?

Regarding your old mahogany....it depends. Old wood tends to lose some lignin from UV and other factors starting from the outside of the stock inwards. Hence it has a reputation for being brittle. That's no problem for interior trim but may be a problem in structural applications like planks. You might have an experienced builder take a look at them. Otherwise I'd rehydrate them by soaking them for several weeks, then resaw, plane and test them for their ability to bend and absorb impact. Often it's just a few mm of degraded wood that can be planed off. Sometimes the degradation runs deeper.

I'd also double check the species using a hand lens and key or by taking samples to your local forestry school. I haven't wandered through many old English churches lately, but the true mahoganies are pretty soft to be using in a floor compared to your local oak and beech.

[mattyg]

Thanks. The planking is currently mahogany to just below the turn of the bilge and possibly larch down to the keel. I say possibly. It certainly isn't mahogany and it has been suggested that it might be larch. I'm not sure that we have too many forestry schools but I will seek out the equivalent. The reder appearance toward the stem is glue and not short planks. You are right that there has been some repair work to the stem though. Thank you for your advice. I'm affraid I may be back for more before Esliina floats again. Ta

[Bob Smalser]

Thanks. The planking is currently mahogany to just below the turn of the bilge and possibly larch down to the keel.

It certainly isn't mahogany and it has been suggested that it might be larch.

If your bottom planking is softwood, it is most likely larch but could also be Doug Fir or even Longleaf Pine. A good lumber dealer who deals in imports should be able to identify them.

This is an endgrain slice of larch:



And this is Douglas Fir (Oregon Pine)...LLP looks similar but its earlywood is more yellow than red:



And if you have to match different species, this chart shows their relative stability:

Order of Stability in Wood Species

Most stable to least stable.

Northern White Cedar
Honduras Mahogany
Khaya
Redwood, 2d Growth
Western Red Cedar
Eastern Red Cedar
Atlantic White Cedar
Eastern White Pine
Teak
Incense Cedar
Alaska Yellow Cedar
Purpleheart
South American Cedar
Iroko
Sassafras
Okoume
Spanish Cedar
Black Cherry
Black Spruce
Tamarack
Baldcypress
Port Orford Cedar
Dark Red Meranti
Black Locust
Sitka Spruce
Sapele
Douglas Fir
Longleaf Pine
White Ash
Black Ash
Yellow Poplar
Rock Elm
Slash Pine
Apitong
Light Red Meranti
Black Walnut
Tangile
Western Larch
Angelique
Ipe
White Oak
Live Oak
Greenheart

Last, 5/8" is pretty thin for a boat that large. Make sure your replacement planks don't have any grain runout that weakens them.

[mattyg]

Thanks Bob. I had intended to replace the larch? with mahogany. It seemed strange to me that the wood below wasn't hardwood. I assumed that this was perhaps used to keep the cost down originally.

[carioca1232001]

................And if you have to match different species, this chart shows their relative stability:.....

I refurbished the outside longitudinal planking (15 mm thick) below-the-waterline on my 32 ft motor-cruiser some 3 1/2 year ago .......

The stern-to-amidships region was completely renewed with Ipê flooring boards (much cheaper than custom milled stuff) where the original red cedar planking was deemed to deserve so and the rest of the latter planking simply refastened. Nº 10 silicon-bronze, 1 1/2 " screws were used throughout. Original fasteners were Nº 8, 1 1/4 " bronze screws.

I noted that Ipê and red cedar are on the opposite ends of the table you supplied.......do you foresee any problems, where the two species butt-together and/or in regions where they overlap over short stretches ? (I adopted USCG´s preferred practice, that is, staggered butt-joints over the hull bottom surface, with adjacent joints no less than 3 frames apart).

This boat is getting ready to be launched .....soon !

[Bob Smalser]

I refurbished the exterior layer (longitudinal, 15 mm thick) of the below-the-waterline planking on my 32 ft motor-cruiser some 3 1/2 year ago .......

The stern-to-amidships region was completely renewed with Ipê floor boards (much cheaper) where the original red cedar planking was deemed to deserve so and the rest of the latter planking simply refastened. Nº 10 silicon-bronze, 1 1/2 " screws were used throughout.

I noted that Ipê and red cedar are on the opposite ends of the table you supplied.......do you foresee any problems, where the two species butt-together and/or in regions where they overlap over short stretches ? (I opted for USCG´s preferred practice, that is, staggered butt-joints over the hull bottom surface).

I tend to describe the worst case because I live in an area with a significant dry season.

Above the waterline it's all about humidity....if your humidity is fairly constant year-round you may not experience a problem with mismatches at all, or until the next time your boat is pulled and housed for a period of time sufficient to dry below what's normal for a moored boat.

But below-waterline planks are wetter. They swell more after the boat is launched and they will shrink more during an extended haulout. For more than just a repaint, misting your bottom planks might be a good idea.

[carioca1232001]

......But below-waterline planks are wetter. They swell more after the boat is launched and they will shrink more during an extended haulout. For more than just a repaint, misting your bottom planks might be a good idea.

That does sum it up for the below-waterline planking. Thanks.

[Dan McCosh]

If your bottom planking is softwood, it is most likely larch but could also be Doug Fir or even Longleaf Pine. A good lumber dealer who deals in imports should be able to identify them.

This is an endgrain slice of larch:



And this is Douglas Fir (Oregon Pine)...LLP looks similar but its earlywood is more yellow than red:



And if you have to match different species, this chart shows their relative stability:



Last, 5/8" is pretty thin for a boat that large. Make sure your replacement planks don't have any grain runout that weakens them.

Table is a bit confusing. Least stable is on the top of the list?

[Bob Smalser]

Order of Stability in Wood Species

Most stable to least stable.

Order of Stability in Wood Species
Percent Shrinkage Green to Oven Dry as an Indicator of Relative Stability


Species / Radial / Tangential / (R+T)/2
Northern White Cedar 2.2 / 4.9 / 3.5
Honduras Mahogany 3.0 4.1 3.5
Khaya 2.5 4.5 3.5
Redwood, 2d Growth 2.2 4.9 3.5
Western Red Cedar 2.4 5.0 3.7
Eastern Red Cedar 3.1 4.7 3.9
Atlantic White Cedar 2.9 5.4 4.1
Eastern White Pine 2.1 6.1 4.1
Teak 2.5 5.8 4.15
Incense Cedar 3.3 5.2 4.25
Alaska Yellow Cedar 2.8 6.0 4.4
Purpleheart 3.2 6.1 4.65
South American Cedar 4.0 6.0 5.0
Iroko 4.0 6.0 5.0
Sassafras 4.0 6.2 5.1
Okoume 4.1 6.1 5.1
Spanish Cedar 4.2 6.3 5.25
Black Cherry 3.7 7.1 5.4
Black Spruce 4.1 6.8 5.45
Tamarack 3.7 7.4 5.55
Baldcypress 3.8 6.2 5.6
Port Orford Cedar 4.6 6.9 5.75
Dark Red Meranti 3.8 7.9 5.85
Black Locust 4.6 7.2 5.9
Sitka Spruce 4.3 7.5 5.9
Sapele 4.6 7.4 6.0
Douglas Fir 4.8 7.6 6.2
Longleaf Pine 5.1 7.5 6.3
White Ash 4.9 7.8 6.35
Black Ash 5.0 7.8 6.4
Yellow Poplar 4.6 8.2 6.4
Rock Elm 4.8 8.1 6.45
Slash Pine 5.4 7.6 6.5
Apitong 4.6 8.2 6.5
Light Red Meranti 4.6 8.5 6.55
Black Walnut 5.5 7.8 6.65
Tangile 4.3 9.1 6.7
Western Larch 4.5 9.1 6.8
Angelique 4.6 8.2 7.0
Ipe 6.6 8.0 7.3
White Oak 5.3 9.1 8.0

[carioca1232001]

Order of Stability in Wood Species
Percent Shrinkage Green to Oven Dry as an Indicator of Relative Stability


Species / Radial / Tangential / (R+T)/2
Northern White Cedar 2.2 / 4.9 / 3.5
Honduras Mahogany 3.0 4.1 3.5
Khaya 2.5 4.5 3.5
Redwood, 2d Growth 2.2 4.9 3.5
Western Red Cedar 2.4 5.0 3.7
Eastern Red Cedar 3.1 4.7 3.9
Atlantic White Cedar 2.9 5.4 4.1
Eastern White Pine 2.1 6.1 4.1
Teak 2.5 5.8 4.15
Incense Cedar 3.3 5.2 4.25
Alaska Yellow Cedar 2.8 6.0 4.4
Purpleheart 3.2 6.1 4.65
South American Cedar 4.0 6.0 5.0
Iroko 4.0 6.0 5.0
Sassafras 4.0 6.2 5.1
Okoume 4.1 6.1 5.1
Spanish Cedar 4.2 6.3 5.25
Black Cherry 3.7 7.1 5.4
Black Spruce 4.1 6.8 5.45
Tamarack 3.7 7.4 5.55
Baldcypress 3.8 6.2 5.6
Port Orford Cedar 4.6 6.9 5.75
Dark Red Meranti 3.8 7.9 5.85
Black Locust 4.6 7.2 5.9
Sitka Spruce 4.3 7.5 5.9
Sapele 4.6 7.4 6.0
Douglas Fir 4.8 7.6 6.2
Longleaf Pine 5.1 7.5 6.3
White Ash 4.9 7.8 6.35
Black Ash 5.0 7.8 6.4
Yellow Poplar 4.6 8.2 6.4
Rock Elm 4.8 8.1 6.45
Slash Pine 5.4 7.6 6.5
Apitong 4.6 8.2 6.5
Light Red Meranti 4.6 8.5 6.55
Black Walnut 5.5 7.8 6.65
Tangile 4.3 9.1 6.7
Western Larch 4.5 9.1 6.8
Angelique 4.6 8.2 7.0
Ipe 6.6 8.0 7.3
White Oak 5.3 9.1 8.0

Now you have me confused !

'Hearsay' in this part of the world has it that Ipê is the yard-stick against which the stability factor in diverse wood species may be compared.

Yet the 'green to oven dry' figures in the above table may suggest otherwise.

Once the species is transformed from 'green' to 'dry' or 'oven dry' - I recall several posts of yours calling for air drying as opposed to oven drying, to ensure long-term stability - how applicable are the figures in the table for when the sample is wetted again, given that there is little chance of it turning 'green' again ?

[Bob Smalser]

Yet the 'green to oven dry' figures in the above table may suggest otherwise.

Once the species is transformed from 'green' to 'dry' or 'oven dry' - I recall several posts of yours calling for air drying as opposed to oven drying, to ensure long-term stability - how applicable are the figures in the table for when the sample is wetted again, given that there is little chance of it turning 'green' again ?

I developed this chart as an aid for substituting species in planking, as in old boats sometimes the original species....for example old-growth Longleaf Pine....is no longer available.

How much wood shrinks in drying is a direct indicator of how much it will shrink and swell in normal seasonal movement. All this USDA test does is measure than by uniform drying in an oven....it has nothing to do with kilning or airdrying wood for service.

The USDA measured shrinkage from green to 12% as well, which more closely correlates to how we use wood, but that information isn't as commonly available for foreign woods as green to oven-dry is.

All the chart shows is relative seasonal stability between different species for flatsawn, qsawn and riftsawn grain. You can also obtain that with only slightly less accuracy by using the wood's weight, as generally the denser the wood, the less stable it is. Ipe and cedar are nowhere close to each other by any measure.

For example the chart shows riftsawn Ipe shrinks 7.3% in the green to oven-dry test. The same number for mahogany is 3.5%. That means Ipe moves seasonally twice as much as mahogany. And based on that, given a specific piece of wood and a specific change in moisture content, we can also determine the change in dimension expected.

[Andrew Craig-Bennett]

Thank you Bob; that is a most helpful chart and explanation.

[carioca1232001]

.....The USDA measured shrinkage from green to 12% as well, which more closely correlates to how we use wood, but that information isn't as commonly available for foreign woods as green to oven-dry is.

No news is good news ! The more you know, the scarier it gets !

.....You can also obtain that with only slightly less accuracy by using the wood's weight, as generally the denser the wood, the less stable it is. Ipe and cedar are nowhere close to each other by any measure...........For example the chart shows riftsawn Ipe shrinks 7.3% in the green to oven-dry test. The same number for mahogany is 3.5%. That means Ipe moves seasonally twice as much as mahogany. ..........

This particular bit of data is going to bust the bank ! I can´t wait to show it to the 'conventional wisdom' boys at the club, their head guru included, the latter with at least half a dozen 30-40 footers built to date, from the keel up.

[Dan McCosh]

The chart is pretty much the reverse of what I thought were the most stable woods. Interesting.

[Mrleft8]

3" thick flooring?

[Bob Smalser]

No news is good news ! The more you know, the scarier it gets !

This doesn't mean you can't plank a boat using Ipe, although the result would be quite heavy. There are no shortage of boats in Scandinavia planked with oak, which has similar characteristics. It means that in a tightly-caulked carvel hull that Ipe will experience compression set and become a weeper long before the most stable woods will....and in a lapstrake hull more likely to experience cracked planks.

The higher the degree of expansion and contraction, the more carvel plank edges are crushed and lose their resilience, the more the planks shrink when the boat is hauled and dried, and the slower they will take up when the boat is relaunched. It's not an accident that nature's two most stable woods....mahogany and cedar....are traditional planking woods where they were available.

It's not the end of the boat....after all, the USS Constitution has survived a day or two with unstable planking. Simply minimize the potential problems by keeping up with the coatings, limiting haulout durations, and when it's hauled mist the below-waterline planks when you can.

[Bill Mercer]

Wouldn't England be easier on planking than many areas of the US, especially the pacific northwest? You can leave yer boat in all year here, but the summers (well, except for this one) get desert-dry, while it rains almost continually winter through spring. England, I thought, had a moist climate all year. Also, on the east coast most folks haul their boats for the winter because if the ice.

[carioca1232001]

.......It means that in a tightly-caulked carvel hull that Ipe will experience compression set and become a weeper long before the most stable woods will....and in a lapstrake hull more likely to experience cracked planks.

You may recall George Georgiades´'Dalia', 60-footer, Bostonian cod-fisher ?

Well, it is of strip-planked construction, Ipê throughout, excepting for some cedar in the interior finishing and 'freijó' (a teak look-alike) on the decks.

I have never, ever seen a bilge like Dalia´s, not a drop of water anywhere.

It is a new boat, though, and epoxy + strip-planking could make for a virtually impervious hull, at least over the time span that the epoxy will not begin to degrade.

On the other hand, a lot of our traditional schooners ('saveiros') are built of Ipê and the boat-building methods 'locked up in the past', not to say 'questionable quality'. That these may have chronic, weeping bilges - for the plausible reasons you have stated - has never been divulged much, if anything at all.

It's not the end of the boat....after all, the USS Constitution has survived a day or two with unstable planking. Simply minimize the potential problems by keeping up with the coatings, limiting haulout durations, and when it's hauled mist the below-waterline planks when you can.

How does one go about 'misting' the below-waterline planks
? Would an old-fashioned, hand-operated inecticide 'flitter' be adequate ?

[Bob Smalser]

Of course it's not the new boats that have issues, it's the old ones that have spent a lot of time out of the water.

To keep the planks hydrated for periods of repair longer than just repainting, I'd store the boat in an enclosure with (ideally) a dirt floor covered with gravel, and I'd irrigate the planks using soaker hoses sufficiently often to keep the humidity up surrounding them.

[carioca1232001]

........I'd store the boat in an enclosure with (ideally) a dirt floor covered with gravel, and I'd irrigate the planks using soaker hoses sufficiently often to keep the humidity up surrounding them.

The goal is to have this boat out on the charter market, suggesting that a mooring, either leased or purchased, be of primordial importance. I already own a space in the hangar.

BTW, hardly any members of the Rio Yacht Club realise that they are blessed with the 'zero-fee' modus operandi of our Travel Lift service.......costs a fortune any place else in Rio, let alone in the rest of the world !