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Cmackg

Getting close on my Spin-10

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Lost a job in May, so I decided to build a boat. Got my wood last December, spent a while deciding on a set of plans......Anyway, thanks to the Covid, all I got is time on my hands, and credit cards to run up.....

 

im getting close to final epoxy and painting.

 

im thinking of making the mast using the Birdmouth technique - has anyone else done that?  Here’s a proof of concept, it’s too big, I was using easy wood on hand.

Now Virginia has ramped up the Stay at home rules, I think I can take this to my lake, but may stay off the sailboat it was meant to be a tender for.......

 

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I built birdsmouth masts of Douglas Fir for my Lapwing.  They are a little heavier than aluminum, and IMO look stunning. I found Sitka, DF and Alaskan Yellow Cedar all meet the strength standards for the design Graham included in my plans. Sitka is hard to find and expensive, but the best choice for weight and fastener holding. Alaskan Yellow Cedar is next in weight and equal in fastener holding. DF is heaviest and also good for holding fasteners. It is also the cheapest in most areas. I used DF, couldn't get Sitka and ALC was considerably more money. Due to weight I wish I had used ALC, but not going to lose sleep over it now. The Lapwing specs call for staves 3/4" thick by 1/14" tapered to 3/4", which creates a 3" OD mast tapered to 2". Do your plans include the specs for birdsmouth? I found the 2 hardest parts of the process to be tapering the staves and assembly of 8 pieces in on shot. I tapered the staves free hand on my table saw after the birdsmouth detail was done. I then dressed that surface with a hand plane. I made the taper lines with a chalk line after clamping the staves true to 3 saw horses. There has to be a better way, but it worked. For assembly I made 2 half round concave forms for my saw horses to act as a mold to hold the pieces as I assembled them. Make your epoxy mix on the thick side and slobber both the square edge and the birdsmouth.  You do not want any voids.   Getting the last two staves, all slobbered with epoxy  together was amusing to say the least. I used short pieces of line with loops in one end to tighten and hold the thing together.  One line every 8" or so. Hose clamps are better, but I am a cheap skate.  What a mess, both me and the work area.  Plan accordingly. Make your mast a little long and then dress and plug the ends.  Save both end cut offs to impress your friends. I cut doughnuts from each end to save. My desk top comp is in storage until I can go house hunting, delayed by COVID 19 after my 3 month trip to Africa.  So it may be a while before I can show pictures of anything. I think the process was worth it.  Your boat won't sail any better but it will look beautiful and lead to another well deserved bragging point. Make sure to summon up all of your patience before beginning, you will need it.  Best to you in your endeavor.

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The spindrift plans call for a solid mast at 2.75 inches, taper to 1.25. A duck works article says to scale up 10%, so I’m shooting for 3 inches which feels large. The birdmouth wasn’t too hard to cut on the table saw, and I’m thinking the taper would be done with a power planer, in sets of 3 or 4, not sure. I’m thinking I’ll go 3 inches down to 2, which means my 1.25 in slats end up at ~5/8. I’m thinking clamp them down and take out the material over a run of ? 6 feet. Seems hard to imagine, but I’ll see. The article also mentions putting a solid core in for the bottom section, up to around where the boom attaches. Seems fair. 
 

this system saves a lot of sanding after the fact - I think I’ll leave it octagonal. 

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My masts are 17 and 18 feet.  I would think yours could be smaller than 3" in diameter, but that is just estimating and not sound engineering advice. Send Graham and/or Alan a message. They may have already done the calculations.  I didn't sand to round, I used a hand plane.  Go from octagon to sixteenagon, to thirty twoagon and soon you will have round.  Then sand. It really does't take that long. A hallow mast is stronger than solid BTW. Putting a solid block inside where the boom attaches is a good idea and not really very hard to do. I have sprits, so not needed. I have done surgery on large boat masts and inserts at spreaders are common too.

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I put a lug rig on my CS15, and the mast is 16' birdsmouth out of Doug Fir.  DF is relatively inexpensive and its reddish color looks quite nice.

 

I used too much math to calculate and measure the taper.  Now I'd go with a simple bent batten to get a nice fair curve on one piece and then use that piece as a reference to match the others to.  It looks like your mast tube is already installed, so that answers the diameter question.

 

In addition to the boom attachment, a lot of forces get exerted at the deck-level end of the mast tube.  Reinforce with a solid core there too.

 

The glue up gets sloppy as Dave suggested.  It can be a mess, but if you have a stay-at-home partner, an extra pair of hands can be an enormous help.  The semicircle forms are a must.  I used four on my bench, but I didn't get them aligned exactly right, so my mast has a slight bend.   No problem. I just aimed that bend at the stern and called it a subtle rake. <wink>

 

Good luck!

Bob

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Thanks! Guy I read mentioned using waxed twine to hold them tight while gluing. I’m totally doing this next week. 

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Twine might be too thin to pull it tight enough, will cut into your hands. I used cheap sash cord and just dealt with it sticking.  Have fun.

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I really enjoyed building birdsmouth masts. I did a couple of test glue ups first. something done with scrap wood to get my saw lined up and build my confidence. I do not have the plans or info at hand but here are some photos. good luck have fun. I have used my Spindrift 10 masts pretty hard with zero problems. I also have birdsmouth on the upper sections of my EC 22. What ever wood you choose expensive or cheap make sure it is as knot free and straight grained as it can possibly be. I think old bicycle inner tubes cut into strips make the best clamps. All my ideas were borrowed from someone I can't remember most of them, but the building jig is from Graham. Blocks are all fastened down and level first strip is fastened down with a headless nail. The other strips are then gathered around and wrapped with inner tubes.

 

If remembering correctly I stacked all the staves and brought them to a tapered line with the hand plane.

 

 

I am pretty sure that is the base of the Spindrift 10 mast with the quarter dollar for size reference.

 

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The cut off must be from my EC 22 mast.

 

 

 

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This is my table saw setup for cutting the staves.

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Beautiful...very nice work. I'm not building a sailboat, but this makes me want to build a birdsfoot (oops, birdsmouth) mast. 

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Oh yeah, that worked pretty well. The taper could have been longer, but it works okay. There’s a little bend on one side, I’m putting it forward so that tension on sail will straighten it. Used your saw jig advice Joe Anderson. Made some frames to hold it up. The glue wasn’t nearly as hard to do single-handed, I just laid one stick after the other, then strapped with packing tape and clamps. The core goes for a foot above the boom, so feels solid. 

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Mast is done, epoxied and coated with petit sea gold, boom as well. The boat has 3 coats of paint, I want to paint the bottom blue. Finished my sail that I sewed from old scrap sails. So yeah, pretty close to done! Thanks for the compliment, it looks great from a distance, lol. 

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Yes, your work is exquisite, but so is that barn you're working in. Wasn't it part of Clint Eastwood's  "High Plains Drifter" movie set?

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That’s my dad’s barn, a mile from my house. Quakers built it, pegged post and beam, about 150 years old, we guess. Gets cold in the winter, hot in the summer and photographs really well. He has a pretty nice wood shop downstairs, so the commute from cut,, test, and recut is pretty easy......we’re in Virginia, used to be a dairy farm. 

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On 4/5/2020 at 8:27 AM, Joe Anderson said:

I really enjoyed building birdsmouth masts. I did a couple of test glue ups first. something done with scrap wood to get my

 

 

 

Thanks Joe, for all the outstanding visuals!

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I think barns are a soft spot for most of us...take care of that one.  She's a beauty.  It must be a pleasure working in there; whatever the weather.

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