Birdsmouth mast

[Don Bailey]

Over the winter I want to build a birdsmouth mast for my Pooduck skiff. The mast is 12' long and is tapered at both ends. The bottom is 2.25 inches and goes to 3 inches, 14 inches above the bottom, then tapers to 1.5 inches at the top. I am going to make this mast about 4 inches longer than the plans call for to give a little more headroom at the boom. Has anyone built a birdsmouth mast/spar with a double taber? If so, how do it go? Did you have any difficulties? Any and all suggestions would be appreciated. Certainly I can't be the first who would be working with this shape.
Thanks,

[Jack C]

I just got done making a 11.5' mast. I have no idea why you want to go to the trouble of making a birdsmouth mast of such a short length. A solid one isn't going to weigh that much more.

Make it solid and it will take you about 1/4 the time.

Jack

[ 12-20-2002, 03:01 PM: Message edited by: Jack C ]

[Beowolf]

It seems to me if you run a search of masts in here, you'll find a specific article on taperred bird's mouth spars. I built a pedastal for a table with a comprable taper to it, but it was short enought that I was able to design a jig that would cut everything correctly. Essentially, I dimensioned it at either end of the taper and then let everything project linearly from one end to the other. Worked pretty well.

Take Care

Jeff.

[Cedarhill Boatworks]

Jack C. is right. Your taking a long run for a really short slide. The void in the mast in going to be less than a half inch. If you are really that concerned about weight start with a square section, rip it in half and cut a dado out of the center of each section with the dado head at a 45. Glue the sections back togehter and pare it down to round.
Or just but a nice peice of spruce and have at it.

[Dan Nielsen]

Are you building the mast for the pure joy and challenge of it?

[capt jake]

Though I don't have an answer for Don, I think his question revolves around the double taper.

The way I am reading it, there are 2 different tapers he is trying to incoporate. One at the top and one at the bottom.

Though I have considered the birdmouth method, I went for the solid, for the reasons stated above. smile.gif

[NormMessinger]

A double taper is just as easy as a single. Use carlson design's little mast program to determine the width the staves need to be to give the diameter you want at several stations along you mast. Measure to a few thousandths, cut the tapers in the staves, cut the birds mouth, slather on the glue of your choice, assemble and proceed.

It's, well, duck soup.

--Norm

[ 12-20-2002, 05:13 PM: Message edited by: NormMessinger ]

[Don Bailey]

Thanks everyone for your responses. Since I've already got a hollow mast, two halves routed out and glued up I guess I do want to build the birdsmouyh just because. The main reason for building though is to slightly increase lenght and gain boom headroom. Thanks especially to Norm who said a double taper is no problem. I'll let you know how it turns out.

Thanks again,

[Don Maurer]

I built a 12' birdsmouth mast tapered at both ends, but I plugged the bottom section with an octagonal core to just past the mast partner, makng the bottom section solid. I tapered the top portion of each stave, but left the bottom portion straight. Once it was glued up, I planed the flats to the correct taper on the bottom. I would have done it the way Norm suggests, but I was afraid of the stress placed on the unstayed mast at the partner.

[imported_Steven Bauer]

I made a birdsmouth mast for my John Gardner skiff and I tapered both ends. I cut the birdsmouth before I tapered the staves though. I used the tablesaw to cut the birdsmouth - if the taper was done first you'd have to use a router and even then it'd be easier to cut the taper after. I really don't understand these guy's comments above - the hole inside the mast is way more than 1/2". And I don't think it was any more work to do it this way. You rip the strips, cut the birdsmouth, taper the ends in a taper jig, and glue it up. I was sort of dreading the glue-up but it was easy, much easier than I thought it would be. I wanted to be able to step the mast while out in the boat so I think the weight saved is important.
Steven

[Jim Goodine]

I agree with Steven. These birdsmouth masts are very easy to make. I made a 10' spinaker pole with double taper by planing the strips. I had made up a bunch of samples of hollow birdsmouth in different sizes just to get the proportions figured out. Then I clamped the strips together (with a couple of extras in case I had my usual problems), laid them on the bench, and worked them down to a nice curve with the "razor sharp plane". It took very little time. Then I pushed them all through the router mounted in a table and glued them up. The hardest part was getting the glue-up straight. All the pipe clamps were in the way but sighting through the hollow in the middle was best. Let us know how it turns out.

[landlocked sailor]

I have built 3 birdsmouth masts so far: 12', 9' & 20'. I guarentee that nobody who discourages this method has ever tried it. They are light, strong & elegant; things of great beauty. I followed the instructions in the WB article, tapering the square edges of the staves using homemade tapering jigs. The 20' was too long for this so I simply tapered them with a hand plane. I wouldn't build a smallcraft mast any other way! Rick tongue.gif

[NormMessinger]

No arguement about cutting the taper after the birds mouth. I've done it both ways but remember the edges of the "beak" are fragile.

Another way to handle the solid plug on a small mast or spar is to run a drill bit up the hollow after the glue up and put in a dowel. On a small spar a round piece may be adequatly made hexaginal by the epoxy/filler squeeze out inside. Having a plug at the ends and anywhere solid is required handy at glue-up makes it easier to roll the assembly up and get it clamped. Rather than try to sight down the spar to get it straight I made a flat streight table with 2by lumber long enough to support the mast. One side of the mast was to be streight with the taper on the sides and front so that seemed like a the right approach at the time.

The thickness of the staves for spars other than a mast is a guess to me. If those I hefted at the WoodenBoat Show a few years ago that were made by the guy that did the article in The Magazine (I think) are a proper indication the staves can be thinner than one might think, thinner than I made mine. I'll see how thin is to thin, maybe, when I get the spar for Prairie Islander's tops'l hoisted.

--Norm

[ 12-22-2002, 11:39 AM: Message edited by: NormMessinger ]

[ion barnes]

Go to http://home.clara.net/gmatkin/design.htm#new

[NormMessinger]

Go here as well. http://www.carlsondesign.com/ghartcnr.htm

Scroll down to "Shareware for boat designs" and find the free mast programs. One is a little program which will give stave dimensions based on several variables--diameter, stave thickness, etc.

--Norm