Skerry Mast


Hey all,

Will the mistakes never end?  The mast scarf joint went together ever to slight off center as much as I tried to get it right.  Will this cause any issues?  My guess is not since the mast flexes somewhat anyways under sail.

The second question, does anyone have any good pictures of "rounding the mast and boom"

The book describes some metrics but I'm a bit stuck figuring out what looks best.  For strength I was just thinking about taking my spoke shave to it to add an extra side making it from a square to a hexagon which gives it a rounder look.  Should I go more than that?

Thanks so much for any opinions


8 replies:

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RE: Skerry Mast

No, they never do, you'll just get better at hiding them :-)

If it's really only a slight misaligmnent, you're fine. Run a string from top to bottom and see what the maximun distance between the string and the mast is. If it's less than 2 inches I wouldn't worry about it.

When you step the mast in the boat, put it so that it arches backward. (Keep that in mind when you add the mast hardware.) That keeps the left/right flexing (the kind you'll be encountering the most) in a symmetrical axis. Since the boat will never be sailing directly into the wind, a bow in that direction makes no difference to the strength of the mast. With the arch toward the back, it'll flex a bit less running downwind, but probably not enough to notice.

The other thing that backwards arch will affect will be how the sail sets. Again, a small misalignment should be unnoticeable. All the other flexing and adjusting will hide it. Even if it was really bad, putting a wedge into the mast partner to compensate for the backwards arch , tightening the snotter (if it's the sprit rig) and pulling the boom down should take care of that.

Finally, there's the visual aspect. A slight misalignment should be invisible. Arching backwards will make any visible alignment look as if you meant to do that (remember what I said about getting better at hiding mistakes?).

As far as rounding, here's what I did for the cores on my schooner's carbon fiber masts.

I used a belt sander with a #60 belt since the cores were plywood. If they hadn't been plywood, a spokeshave and/or plane would have been a better choice, but plywood is rough on blades.

Have fun,



RE: Skerry Mast

   Good tips as always, thanks for the pics appears it's completely round.  The skerry mast appears to be three poeces of solid wood glued so I think I can use my spokeshave, otherwise I guess I'll finally have to purchase a router. 

RE: Skerry Mast

Its your build so make it as round as you want, or not.  For solid wood, use a plane or spoke shave (I prefer the plane) to knock the corners off to make it eight sided, then again to make it 16 sided.  Then cut a belt sander belt (80 grit) wrapped around the mast to hand sand perfectly round.  If you scribble on the mast with pencil before you start sanding, you will know it is round when the pencil marks disappear.  Here are a coupld of pictures from the birdsmouth main for my GIS.  Same principle but I started with 8 sides.  I made the mizzen mast as described above from square stock.

RE: Skerry Mast

I built my skerry way back in 2005 or so, and it's possible instructions have changed, but don't remember a recommendation to round it.  I left mine square (although I rounded corners)

RE: Skerry Mast

My Skerry plans from 2006 show the sprit rig with a square cross section for the mast and sprit.

As far as round or square goes, my personal preference has been round mast with a square base for gaff rigs. That keeps the mast properly oriented but lets a loosely lashed sail move around the mast. It also lets gaff and boom jaws rotate around the mast and move up and down without binding. This let me avoid the expense of a sail track and gooseneck. A round mast is also a bit more flexible than a square one when the diameter and width are equal. That helps de-power the sail in large gusts.

Balanced lug rigs want a very stiff mast and a flexible yard and boom, so for them a square mast is appropriate.

The sprit rigs I've built have been simple unstayed boomless ones. A tight snotter tends to keep the sprit pretty tightly fixed in relationship to the mast, so a round cross section is very useful to allow the mast to rotate within the step and partner. This requires that the mast, partner and step can handle the mortar-and-pestle-like grinding action.


RE: Skerry Mast

   Ah guess I should mention it's a sprit.  The instructions warm about rounding and making the mast too weak so that's why my original question was what shape should I make it.  There's a warning about size not to go under so I might just add sides until I get near that point.  I marked the the top of the mast step helper so that and under will stay square.

RE: Skerry Mast

For my NE Dory the manual said round off the mast corners off with a 1/2” radius. More rounding would make it lighter, but given my tools and skilz, would also make it look worse tbh.

RE: Skerry Mast

^^ instructions for lug mast, don't know if Bermuda rig is different.

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