mast question

[adla]

i have decided to try the birdsmouth mast and have decided to use the router bit from Lee Valley for the bird mouth cut...but i am unclear how to cut the long staves such that they are tapered. Any thoughts on this? Does the mast NEED to be tapered.

also posting some finishing pics...i epoxied my bits and chock blocks and the taff rail blocks...and am testing the satin spar urethane...it really makes the mahogany look DEEP, RICh even...

Adla

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[Barry Pyeatt]

Traditionally the masts were not tapered until they got above the point that the gaff jaws were not a factor. It makes things a lot simpler if they are the same dimension from the tabernacle to that point. It also makes it a lot easier to fabricate the birdsmouth as a constant and then just taper the solid above that point with solid wood. It also makes it a lot easier to install solid plugs inside the mast where you have thru bolts for attaching things.

Consider that the mast hoops are one dimension and the mast fits well at the base but as they get further up they get looser. It also has an effect on how the gaff main is shapped if they are fluttering around because they are loose. The gaff jaws are also sized for the lower mast and again as the gaff gets raised to working height, it is loose and more difficult to adjust.

But these are picky differences on a small boat. Making it one dimension from base to gaff height makes it easy to do, it works well and you can size the gaff and hoops to fit well instead of compromising on both.

Tapering the solid mast relieves some of the weight considerations. With a birdsmouth you are going to have a little lighter mast and it really isn't going to make much difference in weight at the top if it is tapered.

I would make it straight, consistent in diameter from the base to the top and then taper a plug for the absolute top lenght. That can also serve as the plug for the topmost portion of the birdsmouth and allow for the thru bolting of things. Install a plug at each point during fabrication that you will have any fasteners, such as tabernacle/hinge points, etc.

Should work out well for you and be a fun project.

Just use your router table and a couple feather boards to keep it inline as you run the lengths thru.

[Dave R1]

Barry is right about the taper traditionally not beginning below the point at which the jaws set when the sail is raise. I like his suggestion to make the mast in two pieces with the top piece being tapered and the bottom piece being straight. A long tenon could be fitted to joint the two pieces. It should be plugged where hardware would pass through the mast anyway.

If you want to taper the staves for the top, you could do it a couple of ways. One is to make a taper jig for the tablesaw. Another is to make a sled for a planer which would hold one end of the stock up slightly. Check your Fine Woodworking CD. There must be half a dozen tapering jigs for the tablesaw and at least one for the planer on there.

Your taffrail sure looks good. Keep it up.

[Stump]

Berry...or anyone else!

Does that mean that it would be best not to taper the mast as the plans suggest? Or is the tapering so slight that it really won't make that much difference to the gaff jaws. I'm guessing that realistically tapering won't make that much difference to the weight since the mast isn't very tall anyway but might be enough to effect the gaff jaws. I've been hearing about the leather yoke area having problems and I'm thinking that part of the problem might be the taper, too much slop at the top. Ideas? Suggestions?

[Stump]

I am of course talking about a solid mast...sorry adla, you just keep asking these great questions that get me thinking on a different but related topic and I can't help but jump in.

[Frank Hagan]

Barry's right, traditionally a gaffer doesn't have a tapered mast. But he's also right that it doesn't really matter much on our boats.

I tapered mine, and found a fairly easy way to do it. I like the look of the tapered mast.

Adla, if you decide to taper the mast, here's how I did it the second (successful) time. I cut the bird's mouth in the staves untapered and took one stave and marked off the amount of taper on the side with the flat end, and then planed down to that line.

Then, the tapered stave was used as a "taper jig" for the remaining staves. To do this, I put the narrow end toward the saw first, with the bird's mouth cut along the fence, and placed the bird's mouth cut of the untapered stave against the straight, tapered edge of the first stave. I adjusted the fence so the blade nearly touched the untapered stave. When the saw is started, and both staves pushed through, the increasing width of the first stave pushes the second stave farther to the left, tapering it.

My trials and tribulations on doing this are at http://frankhagan.com/weekender/mastm.htm.

[adla]

i was pokin' around your site earlier frank and that is where i read about a tappered birdsmouth mast practice and theory...and the lee valley router??? Thanks for the link...i had thought earlier about doing such a thing...cutting them all straight and tappering just one and then using it as a guide....i will read your trials and tribulations.

I had a 4x4 for the mast but butchered it. Thank you thank you...no applause necessary. :oops:

If i can practice this birdsmouth thing and get the hang of it...I have enough mahogany (i think) for the mast...won't that be purdy. I most likely won't bother tappering but may find it useful to know how in the future.

Stump...don't worry about jumpin' in on my threads...i am as thick skinned as a boiled owl. Some goOd information has come from thread hiGhJackinG...or as i like to think of it "stream of consciousness" conversation. Jump Jump Jump away on the trampoline of LiFe.

Thank you as always Barry for the detailed wherefores and whys.

Dave- goOOd idea...check my fine woodworking...plus i have unlimited coupons for articles for Like 190 more days.

The verdict on the spar urethane is that the satin is JUST RIGHT but smeLLs sumthin' aweful. :pale: :cry:

Adla

[Phil Gowans]

Adla, No you don't need to tapper your mast. I think I'm about the only person who did not taper theirs. I decided that I did not want the gaff jaws to twist and have more slop as the sail was raised. The mast hoops would have the same problem. I accepted the disadvantage of more weight up high. My reason was mostly to be more traditional and have a gaffer with a non-tapered mast as it always us to be. However, I don't think on our boats it really makes much difference either way.

[Florin {VACATIONER}]

Adla,

We've made our bird's mouth mast a couple of months ago. I made a trial one (2' long) last year out of some scrap lumber I've had just to confirm that I have it in me to build it. It was actually relatively easy to make. Ours is straight (not tapered). Instead of buying 4x4 we bought a couple of 2x4, 16' long. Why?. Easier to find with straight, close grain and without any wobbles in them. They were a lot cheaper as well, and easier to handle.

A few things to consider (the lessons we've learned)

Make sure the tablesaw is perfectly tuned up! Mine wasn't.... and I did screw up the first stave a little, but luckily I cut it a bit bigger because I really wanted to use the new delta planer I bought hehehe. Then I spent about an hour making the necessary adjustments.

Make sure you have in-feed and out-feed supports on the tablesaw 'cause the staves are quite bendy and they will ruin the cut.

Probably the most challenging part in making this mast was assembling it.

It's virtually impossible to put together without at least one helper.

We also made some V blocks to support the mast while assembling and during cure. These v blocks were glued on a 4x4 piece of 1/2" ply each, which we alligned and glued with a hot melt glue gun on a level surface on a line made with the chalk line, just to keep things straight, afterall you want a straight mast, don't ya. We had one about every 2'. Some of the builders have used radiator hose clamps to keep the staves together, but I found them to be pretty expensive for a once in a lifetime experience, so we substituted with inexpensive plastic cable ties. They worked well. Also, these you can't really overtighten 'cause you don't really have the leverage.

We put a footlong plug at the bottom end, and a 2 foot long plug at the top end. The one at the top end sticks out about a foot I believe and we rounded that on the lathe before we put the whole thing together.

Hope this helps and good luck making one either way you go.

Cheers,

Florin

[MikeStevenson]

Adla: Lee Valley router bits are great. I like 'em and have a few. I think they're made by Amana. I can't see why you couldn't taper the staves ahead of time. I'd probably do a few test pieces to get a diameter at the top and at the bottom, then just make the staves as needed; taper from the bottom fat end to the narrow top using the dimensions you worked out from the test bits.

Stump: The tapered mast works fine.

Mike

[Frank Hagan]

I have the math, along with a "close enough" decimal inch to fraction table that is helpful, at http://www.frankhagan.com/weekender/bm.htm. Some people will be able to just use this diagram:

I "copied" the dimensions of the square mast, which is 3 1/2" square for 30" then tapered from that point to 2 1/4" at top. The mast is 15' 1" tall.

To make a round bird's mouth mast with a diameter as above, I made the staves start out at 1 3/8" for the first 30", and then taper from that point to 7/8" at the top. The actual finished size using these "close enough" fractional equivalents are 3 7/16" tapering to 2 3/16" at the top. I did extend the top of the mast a few inches, and would advise making it 6 - 8" longer if you can.

I made the boom the same way, but it is fine solid. If you want a round boom about the same size (2.03" in diameter), use 12' long staves 13/16" wide.

[MikeStevenson]

Cool...That should speed things up a whole bunch! Just pick starting and ending diameters and work from there.

'Fit'were me, I'd do a test at each diameter to make sure things worked out before ripping tapered staves.

Has anyone ever weighed one of these to see if it really saves that much weight? ...just seems like a lot of work...

Mike

[Florin {VACATIONER}]

Yes, I did use Frank's mast math formulae and it worked out great, (thanks Frank). I couldn't see why it wouldn't work out for the tapered mast as well as long as the rules are followed. (I think Craig made his hollow and tapered and it looks great)... . I could weigh in my straight hollow mast, but we would need someone's solid mast weight for comparison's sake. I'm quite curious about it too.

I'm reluctant to entirely believe that there are significant weight savings as well, but it sure is a more economical method to build the mast. The two 2x4 I bought were $80, in comparison to $260 I would have had to spend on the 4x4 if I could find one worth spending the money on. Not to mention the theory of the hollow mast not warping in time due to the grainof each stave working against eachother. Me thinks going with the hollow mast would be a better choice, but then again, it is just my opinion and we all know opinions are like a$$holes, everybody has one and they all stink :-)

It is quite obvious the solid mast has been used for centuries and it definitely works well, so either which way one decides to build it should work out just fine.

Florin

[Craig]

Franks formula works fine. My mast is straight up until the white part. That is a plug that goes into the end and is a 1/2 inch or so smaller in diameter. It fits about 10" into the lower mast and extends up 18" A taper is OK for a top mast or the ends of yards but for a mast as large as these I think I would keep it straight for simplicity. As I recall the scantlings for these masts call for 3/4" or so for a 3 or 3.5" mast. I just bought two clear fir 2x4s and most of them are now on the shop floor after making the topmast. 2x was $1.60 US a foot. 1x which is 3/4" thick was $1.00 US per foot. Use the 1x lumber if you need 3/4" or less stave thickness. It is easier to rip too.

[adla]

well, the plan is to make a test *smaller* version and then a test full size mast...because I have enough mahogany to make the mast with and i am in no mood to mess that up. i impatiently await the arrival of the lee valley router bit......I liked the idea of building small braces that set every 2 feet so the mast stays straight while it cures. I am thinking west epoxy and a little 404 filler for the glue up as usual. Of course I will have to do the glue up in the MIDDLE of the night since it is 0ver 109 everyday :evil: THANKS MUCH for the information, links, measurements...etc. I will post my progress.

Adla

[Stump]

$260.00 for a 4X4 :shock: :shock: :shock:

I have a bridge I could sell ya.... :?

[adla]

WHAT???? WHeRe dO U buy YER luMbEr?

the 4x4 i trashed was 19 $$ and change...(DF) I have LOTs of mahOgAny though...that was a bit (a lot) more expensive....but they gave me a deal since they didn't want to keep the 14 footers in stock...

thank you thank you

a.

[Barry Pyeatt]

Think if you are looking for clear, Vert. grain Doug. Fir in long lengths for a

Vacationer and live in the middle/eastern portion of Canada that they would certainly quote you figure that could easily run to over $260 (Can.) for material for mast and boom.

I got two 14' clear, Vert. grain Doug. Fir for just under $100 (US) by shopping and looking for material that they couldn't sell for finish work. (Scared, dinged, dirty and small splits on one edge along with some chunks missing.) Since they were being ripped to size it didn't matter.

I also found some for a friend building another boat that came from a reclaimed lumber yard. $25 for three of them over 14' long. One was tight knot cedar and really nice but dirty and aged. The other two were clear vert. grain Doug Fir. but again dirty, dinged, a few nail holes along the edges and again some small chunks missing, but once cut down they are magnificent material.

He also built a boat with a birdsmouth mast, 16' mast out of doug fir. It weighed just 11# less than the solid doug fir mast he was replacing. He plugged the mast in several areas as well as the lower 4' and a solid 3' tapered plug at the top. Advantage as far as he was concerned, round rather than tapered semi-octaginal. Stronger than the old one that broke after only 15 years. And very pretty to look at. He made that out of tight knot 1X stock ripped to size. He also scarfed a few shorter lengths together to get rid of the worst of the knots. Been about 4 or 5 years on the water now and it is a good mast for his boat.

If you are fabricating it from Mahogany or Spruce, it should end up about 5-7 pounds lighter than the solid version of the same material by the time you get finished plugging it and adding a top mast plug to it along with the plug thru the bottom 3-4 feet of it.

Not much difference in this size of a boat, but a great exercise in woodworking. Tabernacle may end up being interesting, but there are some designs for single point hinges that would work if the interior is a solid plug. Personally, I think I would use a solid base square below the hinge point, then a square transitioning to an octaginal plug for a short distance above the hinge, say 12" with another 12 inches more of interior plug, and then birdsmouth to the top as a constant dimension, then taper the last 18"-24" with a solid plug again.

My reasoning is the solid connection and base below and at the hinge point makes for a hinge as designed, which works well and is easy to do. Use Stainless steel hinges from Bosun's Supply. Let them into the solid base so that they are flush with the wood. Reverse the front one so the actual hinge is let into the wood so it is flush on the outside. Clean and neat. The solid base allows you to attach cleats, turning blocks, etc to the mast without any woories about the integrity of the birdsmouth mast. I would fabricate the base from the 1X Mahogany with a solid core and epoxy the entire piece together. That way the entire mast will have the same material.

The solid tapered topmast will allow you to make all the connections and attachments again without worrying about the integrity of the birdsmouth mast. I would install a small water proof connection at the lower end of the birdsmouth and run wire up to the top mast where I would exit the birds mouth and allow for a mast head light. You can run a short jumper from a plug in the cabin wall to the mast when you need to use it. Again keep the fittins flush with the surface of the mast so that there is nothing to hang up on the mast hoops or lacing if you decide to go that way.

I would make the birdsmouth constant dimension all the way up or only taper it slightly, then let the top mast bring it down to the smaller dimension above the gaff.

Wrap the area where the gaff will ride on the mast with a piece of well oiled leather for the gaff to ride on instad or trying to line the gaff jaws. You can lace the leather to the mast and simply keep it maintained so that it doesn't dry out and crack completely. Easy to replace when needed.

Fitting a multi curved section of leather to the inside of the gaff jaws isn't all that hard to do, but securing it other than by lacing it on the outside is a bit of a challenge. If you glue it inplace, it gets hard and brittle with most adhesieves, but you can still oil the surface to keep it pliable. If you form it soaking wet and lace it, it will dry out to the shape of the inside of the gaff jaws and then it is easily maintained with neatsfoot oil. Fun project. I will most likely opt to cover the mast where the gaff rides rather than line the gaff jaws. Reason, my mast is tapered, the gaff will be loose at the raised height and I feel that wrapping the mast is a more viable and still a very traditional method of dealing with it. Lots of Friendships have that portion of the mast wrapped, most of them with canvas or leather.

Mahogany should make a beautiful mast, very rich looking and attractive.

Just be prepared to do a fair amount of refinishing on it with Helmsman Spar Varnish in your climate. Keep it well covered when you are not using it to help cut down on the UV exposure.

Plug the mast where you may need to make attachments.

[MikeStevenson]

It sounds like the consensus is that the weight savings is probably a bit, but not that big a deal. The main thing is the coolness factor, and the fun of making the part. I suspect the laminated b-mouth mast would tend to stay straighter as Florin points out(although I've never noticed any deviation in the cut 4X4's), and the cost of a laminated one is sure a nice bonus. I think a couple of other things would crop up: you could need to put a drain point in the bottom of the hollow mast, and it would allow for wires to pass up the center easily. The tabernacle could be beefed up by making a foot or so of the mast bottom solid (and maybe the top where the rigging/halyards/etc. attach.) Maybe cut a plug to fit inside the staves and it would glue up at the same time as the mast? It may not be needed.

The tapering aspect makes me wonder: would not a double-tapered spar be possible this way? (Fat in the middle, skinny at the tips.) This would seem like a cool way to build a really light mast or a gaff for a latteen, especially if one epoxied carbon tow along the faces.

Mike

[Frank Hagan]

The birdsmouth structure is strong, but its like an egg ... if you pinch it with a throughbolt, you will crush it. So you do have to have either a solid plug where ever you intend to attach something or use bands to spread the stress around the circumfrence.

There are people doing very light, very strong paddles for kayaks with some pretty complex shapes with the technique. I can't find the link right now, but there's a guy who posted at the Guillemont Kayaks site who was making oars and paddles using very small sections. He flared them, had them round for the handles and oval shaped going down toward the blades, etc.

The really cool thing about the technique is that its strength doesn't come from one long piece of wood. You could easily use shorter pieces, staggering the ends so the staves all overlap glue seams, and end up with an assembly just as strong.