Thread: Birdsmouth for GIS Main Mast

I tried getting the Goat in the magazine, but they felt I had too much commercial interest in the boat. They want third party writers. I couldn't write anything about Drake, an editor or a random guy walking down the street could. Tom did a great job on the article.

I'm off to teach Boat School guys about Birdsmouthing! Thanks for your feedback, Bruce. With the asymmetric birdsmouths I think it is best to taper the stave first then route the groove. You could plane a wide board down the the stave thickness, but there is more wood and time wastage there. You could resaw a board, like a 4/4 or 5/4 or 6/4 board, plane it to the stave thickness and rip off your staves, sure. But it seems easier to get a thick board, rip the staves off such that the rips are set for stave thickness plus some, then plane down the staves to exact specified thickness.

Hope that makes sense, it's early.

Wouldn't one of the editors of Woodenboat be able to sail, for example, Dana's GIS?

I truly enjoyed reading the article on Drake in the 2010 Small Boats issue. Job well done I think and the purpose, history and limitations of the boat were explained very well..

Joost

Joost, It sounds like the editor at WB is going to try to contact you and Dana...that is great. I was kinda persistent that he look at the Goat, and it seems like that is working.

yes, Tom did a great job on the Drake article. When I rowed with him across the cove at WB, about halfway across to the island, he said "wow, we're already halfway there, she can really move".

I think a similarly sized Goat would make a great addition...meaning I could use an extra foot or two on the Goat.

Can someone confirm the diameter of the hollow birdsmouth mast.

THANKS!

I'm out of town so can't check my mast to give you an exact number. I think mine's just a bit over 3" probably not more than 3 1/8"

Just shot off Clint a set of the drawings. Anyone who has purchased a goat plan can get a set of the birdsmouth mast drawings for free.

Just email or PM me with your email address.

MIK

How about a birdsmouth for the PDR for those of us who like to complicate and tinker?

It can be fun to do, but it doesn't really make sense as the two will end up being pretty much the same weight. Also complicates the step and partner - maybe it could be left octagonal in the bottom part.

If you are serious I wlll owrk out the maximum mast diameter and the birdsmouth stave dimensions, but after that you have to work out the rest yourself.

MIK

Reviving an old thread here, but I might actually get around to building a GIS this summer after being distracted by a couple of other builds the last few years. I have a question for Mik and/or those who have built the bm mast for the GIS.

Probably a stupid question, but in looking at Mik's bm mast design for the GIS (12/11/2008 revision), it appears half the taper is applied to each side of the staves, rather than all of it to one side only (which would seem to be easier to measure up and plane). Is this correct/necessary?

Never having built a bm spar before, I'm trying to imagine the effect a one sided taper would have - would it produce a spiral effect looking down the spar (which might look kind of cool, actually)? Would it have any effect on mast strength/function?

Thanks!

Neil

You can taper both sides or one side on a birdsmouth stick. Neither will produce a twist, though most find it easier to taper just one side of the staves. The only way you can introduce twist is during assembly and you'd have to work at it, as the staves tend to self align straight.

I tapered just one side of the staves and it worked like a charm. Scroll about half way down on this page of my blog to see how I did it.

Thanks very much guys, will just taper one side then...

Neil

Howdy, The others are right. It is best to just take it off one side and that means there is a datum for the material removal. The mast does take up a subtle spiral done this way ... or at least when I do it!!! But you would have to be looking really closely for a chance of spotting it. And it won't make any difference anyhow

Michael

Simon, I note from your blog that you used Home Depot 1x2s for your staves. Did you allow any pieces with knots? How hard did you find it to find reasonably clear lumber in those dimensions?