birdsmouth mast help needed

[ScottWidmier]

I have eight 16' staves cut complete with 45 degree birdsmouths.  However, I am having a devil of a time dryfitting the mast without the staves going every which way.  This is exceedingly frustrating after reading all of the articles on birdsmouth mast where they simply rolled the mast up when dryfitting.  I have tried tape on either side and have tried rolling it around different diameter items.  I have tried starting at either end and then in the middle all to no success.  I shudder to think about glueing this up if I can't get it together when dry.

My last hope is to build a form out of bits of plywood with half octagon shape cut in.  This seems like a lot of extra work given how many articles I read where the birdsmouth mast were simply rolled up!  My basic dimensions are staves 1 1/2 inch wide and 5/8 inch thick.  I haven't yet cut the taper in just wanting to see how the mast went together at this point.  I also need to cut plugs to go into the mast and would appreciate any advice people can give me.  The plugs on this particular mast will be at the tapered parts at either end of the mast.  I plan on tapering the foot so that it is easier to lift out of the deck and maststep. 

I already have made and used a solid mast out of laminating two 2x4 together and rounding with a plane.  Works fine but I would like something a little lighter for ease of raising the mast plus I just want to try making a birdsmouth mast.

[Frank Hagan]

I don't know how you would roll one up!  I used stands made of plywood with a half circle cut in them, and then for glue up, I needed one additional pair of hands to keep everything from sliding around!  When you get the staves longer than about 3 feet, it becomes unweildy.

You can see one of the stands with the half circle cut in it at the top of this pic.  I used three of these and a helper!

[ScottWidmier]

Thanks Frank, that makes me feel a lot better  .  I will cut out the forms and see how that works.  How did you do the plugs?  I could build the mast in halves and then make plugs to insert before glueing up the two halves.  I am only concerned that this might lead to problems with the straightness of the mast.

[Norman Colter]

Scott,

  Do a search on the forum. Charlie Jones has posted some great info on birdsmouth masts. To do two halfs, tape opposite joints so they can't bond and glue it up as one. Opening it to two halfs.

Norm

[Dave R1]

Scott, it's a bit like trying to herd a bunch of cats into a gunny sack at first. After you get a grip on 'em, you can do it.  ;D

When I did the birdsmouth gaff for my Weekender I made some extra pieces so I could make up a manageable section. I used that to fit the plug stock. I made the plug stock with my router and a jig which allowed me to work to thickness which would be a bit harder to do with a tablesaw. The jig held the work and let me rotate it in 45

[Frank Hagan]

Thanks Frank, that makes me feel a lot better  .  I will cut out the forms and see how that works.  How did you do the plugs?  I could build the mast in halves and then make plugs to insert before glueing up the two halves.  I am only concerned that this might lead to problems with the straightness of the mast.

Here's a link where Charlie talks about his method: http://www.messing-about.com/forums/index.php?topic=4325.msg36102#msg36102

And another where he talks about the jigs he uses (PVC pipe "ring" for one end rather than my plywood half circles), and PAR chimes in with his tips on gluing up half at a time and how to clamp it:

http://www.messing-about.com/forums/index.php?topic=3184.0

[dale]

Scott,

Just curious - what kind of wood are you using?

[ScottWidmier]

It was Charlies method I was talking about though I didn't see the thread PAR responded in so thanks.  I assume masking tape is sufficient enough to keep the halves from sticking to eachother?  Charlie scares me a bit by the PVC method because it kinda sounds like vodoo given how true I found Daves statement of it is like herding cats.  However, swmbo is fine with my boatbuilding as long as she isn't involved so an extra set of hands is hard to get so I will have to try the PVC method.  I assume the PVC has to be very similar diameter to that of the mast?

Dale, I am using simple spruce for this mast since I am doing it just for the experience of making a birdsmouth mast.  I bought the straightest knot-free 2X8 and cut it into the staves.  Besides, I have had great luck with white spruce on other masts.  It is light weight, easy to shape, and I can pick through and find the best pieces.  My other mast for this boat is laminated out of two spruce 2X and works great.  Be interesting to see how much weight savings I get from the birdsmouth mast.  I predict it won't really be all that much.

[PAR]

Bicycle inner tubes, Velcro, ratchet straps, shrink wrap, copper wire, hose clamps, half moons of plywood, or a single ring just slightly larger then the thickest section of the mast and many other things can be used, to hold the mast staves while you perform dry runs and then eventually the epoxy run. I've found the trick, not controlling the whole mess, the just the end you have in your hand at the time. A quick wrap around one end with a rubber tube, strap or even a length of wire (I like 12 gauge for this) will contain the end, but leave the staves loose so you can align them, butter them up, etc.

A flat work surface and some half moon stands (reasonably closely spaced) can ease the assembly process. The strips of rubber do a fine job, just slash some old bicycle inner tubes and you've some handy low pressure clamps. I used to use duck tape, but now prefer to use shrink wrap. Once you have the one end sort of locked into a circle, you can pry apart the staves and do what you will to them. I use wedges to hold them apart while I apply goo, removing wedges and clamping as I move along it's length. Practice with the dry staves, you'll find a method that works.

[ScottWidmier]

I tried from either end or the middle.  I can't get all eight staves in position to even start wrapping it with anything even if I try to ignore the rest of the mast to concentrate on a part of it.  I think the half-moon stands sounds really good right now.  Thanks for all of the information.

[ScottWidmier]

Ok, anyone who thinks making a birdsmouth spar is fun must be around the bend!  ???  First, I trimmed all of the staves to get the final dimension I wanted using the calculator I found on the web.  I was wanting to dry-fit first before trimming but I figured the extra wide staves were part of my problem.  I then cut in the taper on both ends using my table saw.  Nothing but nothing produces as much sawdust as making a birdsmouth mast out of 2X8 stock and I now have enough coarse sawdust for every cub scout in our pack to make several firestarters  .  I then made six half-octogonal forms instead of the half round.  I figured the half-octogonal forms would give some advantage but also could be easily converted to half-round if I was wrong.  I put the forms along a 2X6 to insure they were well alinged.  All of the above went well though a bit tedious given the number of staves and forms.

Then, it came time to try and dry fit the mast.  I found it still was very difficult to get the staves in position especially the last three that were on top and not supported by the form.  Even then I had to use tape to clamp them together so I could see the shape of the mast.  Now I am very daunted by the next step of glueing the mast up.  There are a lot of surfaces to butter up and putting the staves in place when all slippery seems like it could be difficult.  I assume I use unthickened epoxy?  Is it normal to have some gaps to fill?  I also plan on masking off two surfaces so I can split the mast to put in plugs.  On the plus side, it means less surfaces to have to initially butter up.

[P Doug (WA)]

Sounds like a real challenge!  Good luck and be sure to let us know how it all turns out.  Where is Charlie during all this?  He's the man!

[JTam]

I too had trouble with my birdmouth spars.  Don't remember where I read it, but I made a tube out of newspaper to the interdiameter of the spar, and used it as a core to "roll" the staves around.  Once I got the first clamp on getting the rest of the staves in line and clamped was relatively easy.

I made my plug by ripping a square stock (same width as the inner diameter of the spar) with my tablesaw blade set to 45 degrees - made a great 8-sided plug.

[Howard]

Not Charlie (and that's and understatement), but I've built a birdsmouth mast. Here is a bit of what I've learned.

There are two steps to shape the staves for a tapered mast. You have to somehow cut the birds mouth. I used a router bit. Then you have to taper each stave to get it to the shape you want. I believe parabolic is the shape you are after. If using the bit again, I'd shape each of the staves to the taper I wanted, THEN do the birdsmouth, but that is only because I'm using the router bit. I think I could setup some feather boards to pull a tapered stave through the router table easier than I could plane or rip the taper into a stave that has the birdsmouth already cut.

Mine was 12 sided.....the angles are 30 and 60 degrees (vs your 45's). I never had much problem fitting it together...dry or wet, but it was only 2 1/4" OD mast. I could almost assemble it in one hand. To do a larger one, I'd figure out what my Inside Diameter was supposed to be and cut a piece of round stock from PVC or some other cheap material that diameter or slightly smaller and wrap it around that, using a large rubber band or as PAR has suggested, a band made from a strip of inner tube. You have the core....slide the first, single stave under the band. Add another, and another and another and it will eventually come together on that end. Once you get one end started, the rest fall into place......almost literally, they fall into place. Work your way up the mast adding rubber bands and it will easily come together.

To butter them up, I assembled the whole stack, birdsmouth side up......mixed up some unthickened expoxy and went down the stack with a roller. Once those were all wetted out, I did it again with thickened epoxy, then quickly assembled one end and the rest almost fell into place. Slow cure.....you want time to play with it.

Lastly, when you glue it up, you are locking the shape into place. You want it dead straight to start out with. I made a glue up jig.....V shaped blocks nailed to a 2" x 8", with the V's aligned with a piece of string in 2 dimensions.

For clamps, I used the same rebar tie wire I used to do the stitch and glue. About every foot......twisting it is a powerful clamp.

Other than a few bobbles (rough spots left from the router, I think it came out OK. The 12 sides is nearly round to start with, so it took very little shaping to get it mostly round.

[ScottWidmier]

12 sided, Howard, you have to be nuts!    However, your mast certainly looks great and may be a bit more sturdy than fewer staves.  I thank you for the idea of using the roller to spread the epoxy on the staves.  That sounds like a great way to speed up the process. 

I need to figure out which option to go with for clamping the mast and then I will spread the epoxy.  Wish me luck!

[Frank Hagan]

I thickened my epoxy a bit with wood flour to about a pancake batter consistency.  But I did cheat and had a second pair of hands, my solution after finding the same thing you have found.  Its a bit like herding cats. 

There is a point where things snap together and you have it made.  I over-clamped my first mast using stainless band clams, and bent it.  The second try went much better, with much less tension on the band clamps.  The duct tape, inner tubes, etc. make a lot more sense than band clamps.

[Howard]

Scott:

Nuts? A little.....aren't we all?

On the twelve sides, all things being equal, the more staves, the stronger the mast. You notice very little is taken off the outside to get it round. And the inside is already round to within 1/8th or so. On the bottom, I used a solid core of 1 1/2" yellow pine clothes rod that fitted so close I didn't have to touch it. It runs up the mast about 4 feet. The bottom of the mast tapers a little so it's easier to insert through the mast collar, but the core is solid, so I doubt it affects the strength any. I fitted a solid core of oak dowel in the top, about a foot or so. That was to have a solid core for the mast sheave. It all went in during the glue up.

The only other thing I'd tell anyone about building a birds mouth mast is that to get the inside and outside diameters right takes a lot of math. The stave thickness determines mast stiffness, etc. I think I was somewhere between 20% and 25% of diameter, and I didn't taper the thickness at the top. It seems pretty stiff, yet also pretty light, considering how long it is.

[Charlie Jones]

Very interesting thread here.

I've been away from computers for about two weeks now, and will just be online for tonight, then back into non- internet land for another week. Laura and I are working out of town on a house restoration where we JUST got air conditioning in last week and have zero possibility of going online.  Man has it been HOT !!!

I seriously haven't had that much difficulty getting the birdsmouth spars put together. Once that one end is corralled, you can just kinda "shake" the whole thing and it "pops" into alignment. At least it has for me.

But then I've not tried one using more than 8 staves. I have now built a double paddle using the technique- 1 1/4 diameter, 8 feet long and it weighed in at 31 ozs ;D It WAS for me but Laura tried it and now I need to make another one.

[ScottWidmier]

I write this note from my moaning chair..errr..couch  :'( .  Today I braced myself to epoxy the parts of the birdsmouth mast together hoping things would go well.  I took apart the mast and set up the staves birdsmouth pointing up.  I even went to the trouble of clamping them together so that epoxy wouldn't drip down between.  I pumped out some RAKA resin and mixed in some wood flour.  Then I went to my bottles of hardener only to find out I was down to the dregs on both the slow and medium hardener.  Of course, I had plenty of fast hardener  > !  So, I looked on the side of my epoxy cup and marked a line for where the resin was.  I then tipped the dregs of both the slow and medium into the cup just getting the amount I needed...lucky right  ;D .  Well, not so lucky as the batch I mixed only went halfway up the mast which ment I had to quickly mix up a thickened batch with the fast hardener.  At least the pumps worked!  So, I slathered the remainder of the staves and started assembling the mast which task was made much easier by the octogon forms I had made.  Then I realized something....I had forgotten that I wasn't going to glue two of the faces so I could take the mast apart and put in plugs...STUPID!  Choices, do I go ahead and glue it all up hoping that plugs aren't really needed or do I do the right thing...

I quickly grabbed my box o rags and frantically wiped epoxy off with a tick tick tick sound resounding in my skull.  I then put tape down the length of the joints I didn't want to glue in the hope that this would prevent the epoxy that had already soaked into the wood from bonding  :-\ .  I then assembled the rest of the mast but not without some struggle to get the last stave in place worrying all the while that I was rubbing off too much of the epoxy.  I got the mast together and quickly compressed the tapered ends and held them in place with some tape.  I then wrapped the mast inexpertly with twin...hmmm doesn't seem tight enough so lets try plastic coated wire....hmm, still some gaps so lets try some of that 500' of 1/4" shock cord.  That worked best of all and I only had to use 200' before I felt comfortable  .  Actually, I found a little bit of cord went a long way which really points to the wisdom of PAR's method with the innertubes.

So, now I have a mast glued together with epoxy that I am kinda concerned about going off correctly, with spots that might not have enough epoxy on, with glueless joints that might not prove too glueless, and hands stinging from the acetone used to clean off the epoxy that leaked through rips in my latex gloves.  Next step, after the epoxy cures, is to pry apart the two halves and make the plugs.  I plan on painting the inside of the mast with unthickened and then slightly thickened epoxy with the hope that it will run in and fill any gaps or unglued surfaces.  then I will glue the two halves together and hopefully have a usefull mast after all of this.  Still, folks might not want to sail too close to my boat when the wind picks up  ;D .

[P Doug (WA)]

Hope it all turns out OK, and I an sure it will.  Think I will stick to aluminum for my mast until I get more experience at this boat building stuff.