Steaming larger timbers

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jaysea

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I'm wanting to steam bend some stringers to replace the rotten ones on my boat. They are 4" thick by 5" deep and were pitch pine. Has anyone any experiance of steaming timbers of this size? All the books I've read seem to be talking about steaming 1" ribs etc. Is the theory still the same? Would green oak be better than trying to replace the pitch pine? Anyone got any tips?
 
Never tried it, but there are those who still do it.

I don't know where you are, of course, but one of the Thames estuary yards working on wooden Thames Barges, or the Excesior Trust in Lowestoft, or one of the Scottish yards building large fishing vessels in wood would have all the "know how", and they would be worth talking to, I should think.

The other way to deal with stringers is to laminate them, of course; the pitch pine stringers in my 1937 boat are in two thicknesses - the fastenings keep them as they should be, there having been no suitable glue back then.
 
The oak steam bend timbers in a Hillyard 12 tonner if I recall where something like 2 1/2 x 1 1/2,would be difficult to put in place ,as wood very hot and wet and you need to force it into place.Stringers are long bits of wood which run fore abd aft,ie bilge Stringer,as said laminating best way to go!
 
Yes - steaming of these timbers was how it was done.

Construction of large wooden boats was only possible by steaming of the large dimension timbers. On a decent sized fishing boat some of the PLANKS would reach the dimensions of the stringer you talk of.

The book FROM TREE TO SEA by TED FROST is an interesting memorial to the methods used in the building of the wooden steam drifters of East Anglia (direct descendants of the sail smacks). It gives a good insight into the tools used and numbers required to manhandle the large timbers.

As Mirelle says, there are still places in the UK where this work goes on, and decent sized steam boxes remain.

The rule of thumb was/is one hour of steaming (at 60 to 80 psi) for every inch of timber thickness.

The trouble is (as MOGY says) that timbers of your size are large, heavy, hot and slippery. Not easy to handle with few hands.

Sounds like the boat you have is also of substantial dimensions. The physical difficulty involved in timber work on a 65 footer is worlds away from that required on even a 35 footer.
 
I steamed a bit of 35mm x35mm Oak the other day just to see what it did , i bent it like a strong man bending steel and was amazed . I then tried 150mm x 18 mm steamed for twice as long and nothing . Steamed timber is like grabing hold of a hot frying pan plus 3 - 10 depending on how long you leave it .
I think your looking at 10 .
 
Boiling the timber is also highly regarded, but the water has to be boiling vigorously with no half-measures. I would also recommend laminating as well as boiling to make it easier. Half the thickness = four times easier. You will also need more people that you could believe. Better to have too many than not enough!
Peter.
 
Years ago I bent the hog (25cm x 4cm) for a 20 ft. cruiser. Laid it over the frames, wrapped it in towels and tied them on and every time I passed it, day or night for next month, I poured boiling water on it. Weights pulled it down and the whole thing was painless - if slow !
Ken
 
I've bent smaller (much smaller!) timbers, planks and ribs in situ by putting them in a polythene tube, sealing the ends with rags, and connecting to an ordinary kettle on a Primus nearby with a bit of rubber tube and a bung. The advantage is you can keep testing to see if it wants to bend, and when it does, there is very little hot handling. Just rip the polythene off once the wood is in place.
On longer planks slide the tube along as you gradually bend and fasten, starting at one end.

But I'm not sure the principle would work so easily on the kind of massive timbers you are talking about.
 
The steam Wallpaper removers are very handy. Designed to continue producing steam, (rather than constantly boiling a kettle!) they've got safeties built in to stop you boiling dry, and can run for a good long time before a fill up. Very cheap from B&Q, Homebase etc.
 
Stringers generally follow quite a gentle curve and therefore make steaming considerably easier than tight ribs. Any green timber will bend much more easily than wood with a low moisture content.

There have been articles produced in the marine mags over the past year where timber can be steamed in a bag, rather than the traditional steam box. The advantage is that the wood can be placed in a more favourable position and it also reduces the running about with hot and heavy timber especially if you are short handed. The bag is made from plastic sheeting/ tarpauline material, wrapped around the timber with room for steam .Allow about 50% extra. The bag can be stapled together. Ensure plenty of steam in one end. Maintain a good supply. Bend the plank/timber whilst still in the bag. Allow to cool. Remove the bag.
 
Boil in the bag.

Make very loose fitting tube of cheap tarpaulin from B&Q .
staple the seam every inch or so... but dont make it totally watertight or you end up with tube full of hot water instead of steam.
Place timber in tube and put it in the boat.
(seam downwards so excess water can escape)
staple one end of tube ... put pipe from wallpaper stripper in other end and staple around it... top up wallpaper stripper as needed
Steam for 45% of the total time (total time approx 1hr per 1in thickness of timber)
ease timber to shape and clamp as needed .. no panic.. its still steaming... (its not cooling in 2 mins like the ole steambox method)
when timber is to shape required turn off steam and leave overnight to cool
remove bag next day and fit timber.

Yes it does work!
 
Yes, I discovered wallpaper strippers after I'd already done all my steaming.
In my experience it was best to rip the polythene off straight away, or the wood tended to turn black. Also it's good to let the heat out, or it continues to weaken the wood if overdone.
Being able to slide it along is invaluable. I've steamed 20 foot long planks, fastening at one end and progressively bending, sliding the bag, and fastening/clamping as I went.
 
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Just looked at your website, wow! She's lovely. Whereabouts are you based? I'm a bit manic at the moment, but might be able to find you a few hours later in the year.

[/ QUOTE ]

Hi. She is based in Gloucestershire, on the north banks of the Severn.

I'll be having a play with old tarpaulins and wall paper steamers this weekend! It will be interesting to see what happens.
 
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