Tapering a mast

[Rum_Pirate]

I understand how to mark out and can do the square to octagon etc eventually to circular cross section

BUT

How do I get the taper on all four sides along its length to start with? :confused:

[Paul Girouard]

See this thread

http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=64979

There are other try the FAQ thingie or a search of B&R .

[Tom Robb]

Are you sure you're supposed to taper all 4 sides? Many, I've seen have the aft side straight from partner to tip or the sail may not fit correctly.
Do you have a plan? It ought to show how much and where the taper it.
Measure and mark on the stick. Connect the dots w/ a long reasonably stiff batten and cut to the line w/ your saw/adze/draw-knife/plane - what-have-you.

[Rum_Pirate]

The plans call for a circular section.

I am considering an almost square (3"x 3") section with 1" radius on the corners.

Anyone foresee any problems?

PS Gunter rig.

[Jay Greer]

As mentioned in another post, the aft side of the mast should be straight and not tapered. Other wise, your sail maker will hate you! On the non tapered spar, snap a center line on the fwd side. Port and stbd. diameters will be taken from the after end at the heights as shown on the plans, mark the diameters accordingly and spring a long batten on them. Draw the tapers on all three sides, using a power plane and or draw knife and jointer plane, smooth down the tapers. A round over bit in a router or a half round cutter in a Stanley 45 combination plane will finish off the corners. Then it is a matter of long board sanding to smooth things up.
Jay

[Ian McColgin]

Glad so many pointed out that the luff must be straight.

Don't just round the corners. It will look wretched on a boat designed with a round mast and will not come out as well as tapering the square section on three sides, then eight-siding with the guage, and then rounding. And less work to get it right. Making a big radius corner on a spar is a huge pain unless you happen to have a really big stout router and the raw courage to run it.

[Jim Ledger]

Are you using hoops . If so keeping the aft edge of the mast straight isn't going to do you any good as they bear on the forward edge. The usual practice is to keep the mast fairly parallel sided in the area where the hoops bear.

[Ian McColgin]

Jim's point is well taken, which is why the rigging plan is ever so useful. It's easy to have an attractive taper above the gaff jaws.

[StevenBauer]

This is just one of the reasons that making a birdsmouth mast is so easy. You taper the individual staves on the tablesaw with a tapering jig, then when you glue it up it's already got the taper built in. Oh, yeah, it's round, too. :) (Almost)

Steven

[Ian McColgin]

As always, design parameters matter. A catboat like Marmalade with her very heavy solid sticks out-sails the same hull with aluminum spars because the heavy spars dampen the roll and help the sails stay better filled with the wind. We just walked around another Chappaquiddick 25 in a soutwesterly moderate to fresh breeze (Force 4-5) and associated off-Bass River slop on the ebb.

This is one of several reasons I dare not design a mast and rig from scratch. After lo these many years in really diverse boats with good reading and conversations with superior sailors, NA's, sailmakers and such, I find that I don't have the systematic training to keep from leaving something out. Unless you're actually smarter than the designer, follow the plan.

[Canoeyawl]

It is important to note that a “tapered” spar is usually built as a form of elongated ellipse.
This is stronger than a straight taper and should be carefully laid out with battens from given diameters along the length of the spar.
If the sail is attached to the spar the side that locates the sail should be a straight line.
Chapelles’ Boatbuilding has a treatise on this layout that is worth a bit of study time.

[Nanoose]

I'm not an expert, but you've had some expert replies to your post. We're in the midst of building a mast for Nanoose and it's been an interesting project so far. (The link to the thread is in a post above). We started with a log, which meant we had to square it first (which was A LOT of work), but from there have followed the "normal" method.

With apologies to those who have suggested otherwise, our mast was round and will be round when complete...

There have been a couple of times where the process made no sense to me at all. I have very limited ability to visualize in 3D and (for example) to understand how cutting tapers when it's foursided would translate to eight and sixteen sided. was nearly impossible for me. But I followed the process that Ian Scott mentioned and it worked well.

I then tried to understand how a spar making gauge works. I actually got out paper, pencil and a calculator to understand how it would keep things consistent along the taper, I've concluded that it's not mathmatics that makes it work but magic. I made the gauge and it worked like a charm.

I've now sixteen sided the mast and have cut in the shoulders for the mast bands (I cut these when it was eight sided). I tried to figure out how to make the gauge work to go from eight to sixteen sided but the theory began to make me nauseous, so I just eyeballed it.

The process should work for a D shaped mast or spar as well and, all in all, it's been a real education. Good luck with the project (and post LOTS of pictures.

Dave

[Rum_Pirate]

Are you using hoops. It probably will be lacing as the design calls for. BUT could consider hoops although it not my favourite option at present.


The mast 16'6" overall is gunter rigged so will have a boom about 3'0" from base and the gaff spar about 14'0" up. So the luff will be about 11 feet. The 'taper' would be all along the 11'0" and would be probablynot that significant - provided I tell the sailmaker about it. :)

Taking into consideration that the 'designed' taper will be 2 3/4" dia down to 1 3/4" dia at top. I plan to go closer to 3" dia down to 2" dia at top.

I wiil think about going the taper cuts then octagon then probably due to small cross section go to planing and sanding off the 'corners'.
Am I likely to hit problems doing that?

[Tom Robb]

A spar gauge isn't so much math as it's practical geometry.:D

[Thorne]

I built a 16' mast from two clear fir 2x4s glued together, and went for the oval shape -- seems to work well so far. I use robands rather than lacing, and having a nice slick varnish on the mast seems essential to ease of raising and lowering the sail.

If you are considering making it larger than the plan, take it out sailing a few times before finishing it. I did the same, and realized that the additional weight aloft was really bad juju -- the boat was much more tender than with previous masts. So out came the hand planer and off went the extra wood and I'm much happier.

[Don Z.]

To go back to your original question... how large is the mast?

The reason I ask is that I was thinking of the "cabriole leg" method, where you cut off two sides in one go, then tape them back on with masking tape. You can then rotate the piece 90 degrees, the taped on cut off still supports the piece, and when you cut the other two sides, you're done...

Works well with a band saw, and worked well when I made my seven foot long, inch and three quarters max diameter flag staff. I just have a little, tiny band saw, but if the diameter was less than about four inches, I'd probably go for it.

And yes, the spar gauge is an example of practical geometry. If my geometry teacher would have used such practical methods, I probably would have done a lot better in school. As it was, none of it really made sense to me until we pulled out the compass and started doing constructions.

[Ron Paro]

I laminated and scarfed douglas fir to make a 2¼" x 2¼" x 16'5" blank. Since the bottom 16" and the top 10' of the mast are tapered on three sides, I used a chalk line to mark the tapers, and then rough cut the tapers with this hand saw that cuts on the pull stroke. Then I planed and sanded to the final shape. The wedge helped to keep the wood from binding on the saw blade.

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