wood for Boom

[mikeinkwazi]

I want to make a 20 foot laminated boom. Is there any other wood than Douglas Fir (maybe Larch or Ash?) that will do?

 

[peter radclyffe]

spruce,

 

[pyrojames]

Hand picked knot free european redwood from a good quality builders supplier. I made a pair of spinny poles from it this year, about 20 ft each.

 

[oldfrank]

Sitka Spruce is lightest. You'll need patches of glass matting on places where the boom regularly touches - for example shrouds. Collars usually have it in stock.

 

[Woodlouse]

Sitka Spruce is lightest. You'll need patches of glass matting on places where the boom regularly touches - for example shrouds. Collars usually have it in stock.

Instead of glass matting you could use bronze strips or sheet. More expensive, but better looking.

 

[Amulet]

I reckon, if you're laminating it, you can make the thing out of builders lumber bought from your local builders supplier. If you don't need a solid lump you can cut it to work your way round knots and imperfections. I made my boom (smaller) this way.

It's hollow and made of four bits of builders lumber with a few knots drilled out and plugged.

It's going fine after seven years, and I expect it to do another twenty-seven.

 

[Peterduck]

Actually, you don't need to go for a light timber, as you would with a mast or gaff. Oak would be fine. Don't forget that all the force being applied to the mainsail by the boom is downward. I'll bet that the original builders of fishing smacks didn't fret about lightweight booms. Some people use lightweight aluminium extrusions, and then hold the thing down with a boom vang ( a.k.a. kicker strap). Hello?? Am I missing something here? To be sure, an oak boom would be a good thing to stay clear of during a jybe, but then aren't they all?
Peter.

 

[peter radclyffe]

do you use oak for booms in oz

 

[Peterduck]

There aren't all that many oak trees here, but we do have millions of eucalypts of a dazzling variety. Offhand, I think that there are something like 400 species to choose from. So I would choose Spotted Gum. Very durable, straight grained, lovely to work and a pale honey colour.
Peter.

 

[pyrojames]

There aren't all that many oak trees here, but we do have millions of eucalypts of a dazzling variety. Offhand, I think that there are something like 400 species to choose from. So I would choose Spotted Gum. Very durable, straight grained, lovely to work and a pale honey colour.
Peter.

Odd. The spotted gum I worked with in Sydney was hard as nails, heavy, and had a very cranky grain, and was red/yellow mixed grain. Fabulous for timbers frames and deadwood, but I don't think I'd use it for a boom!

My current boom is about 150 kgs, but it still lifts scarily in heavy downwind conditions, so much so, that we managed to hook it on the backstay gybing during Cowes Classics, then broached and blew the bottom out of the main. Sometimes weight just isn't enough.

 

[mikeinkwazi]

What wood?

Thanks guys. Lots to think about?

 

[DownWest]

The idea of oak spars makes me pause. Light as poss with the strength needed. Heavy ,as in oak,to keep the sail down might have nasty implications in a crash gybe, due to the inertia. Colombian pine or Douglas fir sound about right. Sitka spruce if you can find it, not cheap.
I used 'Red Pine' and made the spars with the birdsmouth system ( look at duckworks site) 4 of the eight laths were continuous, the other 4 were scarfed to avoid knots. Cheap and light and strong. It sounds complicated but is actually quite easy. Table saw or router for the laths.
A

 

[Woodlouse]

Just out of interest what does everyone have against knots in wood? As someone that has a tree for a mast, the knots don't cause any problems, so why the great effort in removing them when laminating? Aesthetics?

 

[pyrojames]

They are always weak points of stress concentration. In a large heavy solid mast the stress concentration is probably not enough to worry about. In a lightish laminated spar, it is.

 

[DownWest]

In a grown timber spar the fibres flow naturally round the knots, once one cuts it into strips the fibres lose their continuity.
A