Seagreen
New member
One for the shipwrights. I'm needing to put a new grown oak frame or two in, so should I source green oak or seasoned, and if so, how seasoned? The original wood is quite old, pitch pine keels and planks.
New oak frames, green or seasoned?
- Thread starter Seagreen
- Start date
srp
Well-known member
I would use a local sawmill - I seem to remember one near Honiton that I used to use when I lived near Exeter. They may have air-dried, otherwise use green. Don't waste your money on kiln-dried. It's going to be sitting in the bilges getting damp or wet much of the time.
FAITIRA
New member
When I worked at Mashfords, Cremyll, Plymouth I was surprised how much Green oak they used, don,t remember what the reason was. Was when they were doing a lot of work on the "Onedin" ship.
Roach1948
New member
Don't quote me on this but I think it depends on the use. My understanding is that green is OK for steaming and that Autumn felled seasoned oak is more appropriate for sawn. For larger bits you need as little sap in the wood as possible as this can promote rot. Hence Autumn felling when the sap is at its lowest.
burgundyben
Well-known member
This is a subject I am interrested in, I think you may be right, green for steaming, seasoned for sawn, will be interesting to see the thread grow (sorry).
srp
Well-known member
There's often confusion between sap in the wood (which is just water, and is removed by drying), and sapwood, which is the lighter coloured outer layer of the trunk just below the bark. Sapwood is no good - make sure that you buy a piece of timber which is all heartwood.
The reason for autumn felling is so that when the log is planked and stickered up to air dry, the drying rate through the first few critical months (December, Jan, Feb) is slow, leading to fewer splits and shakes.
Green timber is best for steaming because you're going to saturate it with water anyway and dry timber would just be a waste. When you've steamed a piece of timber its no longer dry.
Like I said, if you're going to stick a piece of timber in a damp bilge its a waste of time drying it first. If, on the other hand, you've got some sort of epoxy/composite construction which is perfectly dry inside, then go for dried timber - it'll most likely be air dried as kiln drying of thick pieces of dense timber is difficult.
The reason for autumn felling is so that when the log is planked and stickered up to air dry, the drying rate through the first few critical months (December, Jan, Feb) is slow, leading to fewer splits and shakes.
Green timber is best for steaming because you're going to saturate it with water anyway and dry timber would just be a waste. When you've steamed a piece of timber its no longer dry.
Like I said, if you're going to stick a piece of timber in a damp bilge its a waste of time drying it first. If, on the other hand, you've got some sort of epoxy/composite construction which is perfectly dry inside, then go for dried timber - it'll most likely be air dried as kiln drying of thick pieces of dense timber is difficult.
Roach1948
New member
I meant Sapwood as opposed to water (sap). I also understand that Oak is particularly prone to resinous sapwood, and thus rot, specially in fresh water.
On a recent repair, my boatbuilder suggested I use Mahogony to double the frames in the reverse tuck under the engine using an epoxy lamination. I was going to use oak, but he quite rightly pointed out the cracked oak that was already there!
On a recent repair, my boatbuilder suggested I use Mahogony to double the frames in the reverse tuck under the engine using an epoxy lamination. I was going to use oak, but he quite rightly pointed out the cracked oak that was already there!
Seagreen
New member
I'm chasing the local sawmills on monday morning. I've come down on the side of grown frames as I can't be a**ed to laminate them up, and there's no other laminate frames, only grown and sawn oak.
Does the autumn drying rate (ie, slowly) deliver wood with less splits, and thus more structural strength, or doesn't it matter? These crooks will be immersed in bilge water and concrete for the next 100 years (hopefully) so are there any species which are better than others? Don't know trees very well, sadly.
Does the autumn drying rate (ie, slowly) deliver wood with less splits, and thus more structural strength, or doesn't it matter? These crooks will be immersed in bilge water and concrete for the next 100 years (hopefully) so are there any species which are better than others? Don't know trees very well, sadly.
Roach1948
New member
Your stretching my knowledge now, but what I do know is that LAST Autumn's fell will still be drying..... normally. It usually takes a year to dry out - but this current weather trends, I would say go for it!
jhughes
New member
[ QUOTE ]
Your stretching my knowledge now, but what I do know is that LAST Autumn's fell will still be drying..... normally. It usually takes a year to dry out - but this current weather trends, I would say go for it!
[/ QUOTE ]
As a rough guide its a year per inch of thickness to air dry timber. 4" = 4 years.
In a sawmill I used to work in an architect placed an order for an air dried Oak beam that had to be a uniform 12-15% moisture content,
he was slightly p****ed off when the boss suggested he paid for it now before giving a delivery date of 10 years time as the oldest 12" beam in the yard was only 2 years old!
Your stretching my knowledge now, but what I do know is that LAST Autumn's fell will still be drying..... normally. It usually takes a year to dry out - but this current weather trends, I would say go for it!
[/ QUOTE ]
As a rough guide its a year per inch of thickness to air dry timber. 4" = 4 years.
In a sawmill I used to work in an architect placed an order for an air dried Oak beam that had to be a uniform 12-15% moisture content,
he was slightly p****ed off when the boss suggested he paid for it now before giving a delivery date of 10 years time as the oldest 12" beam in the yard was only 2 years old!
srp
Well-known member
[ QUOTE ]
... so are there any species which are better than others? Don't know trees very well, sadly.
[/ QUOTE ]
For what you want I think oak will be best. A second choice might be elm, but due to Dutch elm disease there's little of that about. Mahogany may go black and start to rot within a short time if it's constantly wet and encased in concrete (especially if there is a risk of the water being rainwater, eg during a winter layup). There are a few other tropical hardwoods that will be ok, eg teak, keruing, but oak is infinitely easier to source and more likely to be what the original builders would use.
Don't use iron, steel or galvanised fastenings. Silicon bronze woodscrews or bolts, or copper nails and roves are best. Extra large fastenings can be made up from copper rod rivetted over large copper washers.
(Of course, I don't know anything about your boat! I'm assuming it is a conventional construction, something like larch on oak, with non-ferrous fastenings. Perhaps you can tell us a bit more about it?)
... so are there any species which are better than others? Don't know trees very well, sadly.
[/ QUOTE ]
For what you want I think oak will be best. A second choice might be elm, but due to Dutch elm disease there's little of that about. Mahogany may go black and start to rot within a short time if it's constantly wet and encased in concrete (especially if there is a risk of the water being rainwater, eg during a winter layup). There are a few other tropical hardwoods that will be ok, eg teak, keruing, but oak is infinitely easier to source and more likely to be what the original builders would use.
Don't use iron, steel or galvanised fastenings. Silicon bronze woodscrews or bolts, or copper nails and roves are best. Extra large fastenings can be made up from copper rod rivetted over large copper washers.
(Of course, I don't know anything about your boat! I'm assuming it is a conventional construction, something like larch on oak, with non-ferrous fastenings. Perhaps you can tell us a bit more about it?)
Roach1948
New member
I was going to laminate, but there is a twist in the hull which makes it just as much work to make the mould as it is to make an oak (doubling) frame itself.
Interested to hear the results of your Oak search on Monday. You might save me a search.
Interested to hear the results of your Oak search on Monday. You might save me a search.
Seagreen
New member
The boat was either built as a yacht, or converted in build from a Falmouth Oyster dredger type fishing vessel. She is alleged to be almost 150 years old, the previous owners being convinced she was built in 1860, and certainly looks the part.
She has 1" thick pitch pine planking on sawn oak frames, pitch pine keel with some doubled and replaced frames. All iron fastenings were removed in a previous major rebulid some 15 years ago with copper, and she's more or less fine, except for some softening in a couple of frames which I've dug out of the concrete scrap mix and replacing. These soft frames didn't actually attach to the keel, but stopped short, but I can't leave soft frames lying about...
Does this help? Posted a picture in the thread on jib topsails.
She has 1" thick pitch pine planking on sawn oak frames, pitch pine keel with some doubled and replaced frames. All iron fastenings were removed in a previous major rebulid some 15 years ago with copper, and she's more or less fine, except for some softening in a couple of frames which I've dug out of the concrete scrap mix and replacing. These soft frames didn't actually attach to the keel, but stopped short, but I can't leave soft frames lying about...
Does this help? Posted a picture in the thread on jib topsails.
srp
Well-known member
Yes, I've seen your picture - a lovely looking craft. Larch on oak and 150 years old - I'd definitely use green oak. I bet thats what the original builders would have used, along with an adze to shape it. I'd be tempted to saturate it with a few thin coats of red lead paint just before you fix it in place. When I painted the bilges of my (now sold) gaffer I sanded back to the original red lead primer and the wood underneath was absolutely perfect.
