Grain orientation for birdsmouth mast

[D Gobby]

I'm getting ready to build a birdsmouth mast. I've already started another thread which answered most of my questions. I have one more. Which way should the grain run. Should it be Vert grain running with or across the stave thickness.

Thanks
Darrel

[Big Red]

I saw some pictures of a guy building one, and he cut the wood for the staves and then turned every other one end for end. I think that was only in case the wood had a weakness at a certain point, you know, to alternate the strengths.

Does that help? Be warned, not an expert and only my $.02 ;)

[Bob Smalser]

On sticks that small....I don't think it really matters much.

But I make them with the grain vertical to the birdsmouth so that 90-degree vee-cut doesn't produce short grain at the top of the vee.

http://pic3.picturetrail.com/VOL12/1104763/2595357/30354078.jpg

[Don Maurer]

I made mine with the vertical grain on the face, but only because I had less waste that way. I agree it shouldn't really matter. Although in theory, it should be a little stiffer with the vertical grain on the faces.

[NormMessinger]

I'm inclined to agree that on a small mast the grain orientation does not matter but have no data to support either way. However, how does a tree oriente the grain for maximum strength? Ya think God knew what he was doing? Is it relevant?

[Keith Wilson]

OTOH, the rings in a tree are a result of the way it grows. Could a tree grow so as to produce radial grain lines? Not likely. Evolution works with what it has to start with, and doesn't always produce the optimum solution. Ever wondered why there aren't any animals with wheels?

[guillemot]

http://www.imagestation.com/picture/sraid102/p14378475df42d343ce5df3c5cd361489/f9b4495e.jpg ;)

[ 02-05-2004, 10:58 PM: Message edited by: guillemot ]

[Pernicious Atavist]

Ever wondered why there aren't any animals with wheels?

Oh, geez, it's obvious: Who would fix the flats?

[alteran]

The sloths at Wallabee Mart.

[George Roberts]

guillemot ---

Is Little still the Chair of Bio Mechanical Engineering at MSU.

[NormMessinger]

Re transverse growth rings: How about palm trees? Yer tellin's us God couldn't have made trees differently if he had wanted to? Oh, yea of little faith.

Re Wheels: No good on rough surfaces. But after he created man God got lazy. Figured man would do his work. Mostly.

tongue.gif

[Ed Burnett]

It is quite important that the staves are as near to quarter sawn as possible.

Natural checks in timber tend to form radially, ie. through the thickness of a flat grained board. If this happens in your mast staves, you could end up with a check right through the thickness of the spar wall which has the potential to seriously weaken the spar.

Also, changes in timber dimension with moisture content are greater in the tangential direction. A quarter sawn board is more stable which is no bad thing for birdsmouth spars.

[Keith Wilson]

If you rip staves from a flat-sawn board, then they'll come out just right. I made a mast from a 20' 2x10, right from the lumberyard, cheap and good enough once I threw away the parts with knots.

[guillemot]

george,

Robert Soutas-Little is professor emeritus in the department of engineering. I just looked at their web site. I'm in the Entomology Dept (College of Agriculture and Natural Resources), so I have no contact w/ that group at all. Were you here as a student?

Re Masts. I am planning on building a solid spar for my Swampscott Dory. The mast is 12', the sprit is about the same, and the boom is about 8 feet. I think the boom is 2" diameter at its widest, and the mast is 3". Is there any sense in buidling a hollow spar? Sounds like a lot of work for such a small stick!!

[George Roberts]

guillemot ---

I was a student in the engineering dept in the early 70's. Dr. Little was a really good engineer. I transfered there to convince a wonderful lady to marry me. It worked. Lots of fond memories.

Looks like your mast would weigh 20# solid. Maybe 13# hollow. But, it is a nice skill to learn.