Steam bending advise.

I propose steam bending lengths of 45x10 red hardwood to form the edgeing to a serpentine shaped hardwood deck. Do I bend, glue and tack in one operation or bend and tack first then when the wood has dried to shape,remove then glue in a second operation? If the former is there a glue suitable for saturated wood at boiling temperature? Thanks. Roy

I would bend and clamp it into place too cool as any bamage to the fibres while bending is likely to cause it to snap. You will also need a very straight grained piece of wood free from knots etc.

Jason

Roy

You say that you will be using "red hardwood" - do you mean redwood (as in California redwood) or another species?

Scrit

Hi scrit.
Hardwood not redwood (softwood) ie what is sold by timber merchants as 'mahogany' but can be various species of dark red hardwood-keruing,luarne etc. The radius will be only slightly less than can be achieved with the flex of the wood dry,hence the need to steam.

gardeners26 said:

Hardwood not redwood (softwood) ie what is sold by timber merchants as 'mahogany' but can be various species of dark red hardwood-keruing,luarne etc. The radius will be only slightly less than can be achieved with the flex of the wood dry,hence the need to steam.

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Hi, had to ask - there are people out there who seriously consider steam bending softwood...... I'm with Jason, bend it and leave to dry/cool then fix. The only glues which will set well in the presence of water are polyurethanes, but I don't know how well they work at high temperature/humidity. I suspect that they will foam a lot and set very quickly. UF/PF/RF glues will set a lot faster at high temperature but won't give a good bond on wet timber

Scrit

I would like to say that in the world of steam-bending Mahogany is the most unsuitable wood to steam-bend ,also that there is as many softwoods that are suitable for steam-bending as there is hardwoods unsuitable for steam-bending

splinter said:

I would like to say that in the world of steam-bending Mahogany is the most unsuitable wood to steam-bend, also that there is as many softwoods that are suitable for steam-bending as there is hardwoods unsuitable for steam-bending

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I agree that kilned South American mahogany may not be very good. Perhaps I should have been a lot more specific about this. There are numerous items made from certain steam bent softwoods, most notably North American white cedar is used in traditional cedar strip canoes by the native peoples in Canada and the Pacific Northwest states of the USA, however the technique there is generally to steam bend green or partially air dried timber only. The difficulty with softwoods is that you frequently can't specify the species when you buy in the UK and that what you buy from most merchants is kiln dried (to extinction).

When you dry timbers by kilning it suffers a partial cellular collapse within the structure of the timber as commercial kilning removes moisture from the timber at (an unnaturally) high rate. Sometimes the kiln operator gets it wrong and you end up with "honeycombing" just below the surface which means the timber isn't worth a bean. When we ran an Arrowsmith kiln a long time ago we wasted a lot of green timber to find that out. But the result of kiln drying seems to make many softwoods less suitable than hardwood species for steam bending - which is why hardwoods are generally preferred. Even hardwoods can suffer this problem - air dried teak will steam quite well and is used for many dhows on the Indian Ocean - kilned teak is a complete nightmare to bend and suffers frequent failures. I was once involved in trying to replace the teak decking on a boat with over-kilned teak and it was absolutely disasterous until the owner put his hand in his pocket and bought us the right stuff.

The best resource to find if a timber is suitable is suitable for steam bending is a book called "World Woods in Colour" by W.A.Lincoln, or if you can read Dutch "Hout Vademecum" by Kluwer-TNO both of which contain information about suitability of timbers for steaming

Scrit

Scrit.
Well done for being more specific,a very concise and imformative peice of writing

splinter said:

Well done for being more specific, a very concise and imformative peice of writing

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Maybe I should just have said most of the softwoods you can buy from builders merchants are cr*p for steam bending?

Thanks one and all for the advise. The job is now completed and looks great. The steam bending gave a smooth even curve to the deck edging and is far superior to the 'notching' method of bending timber which results in a curve comprising a series of straight lines! One mistake I learnt from was initially using steel pins to hold the bent timber in place whilst drying. Given the saturation of the wood these pins caused unremovable staining to the hardwood rendering the piece scrap. On the second attempt I used brass pins which did not discolor the timber. Roy