More Mast Questions {Bolger Windsprint}

[Memphis Mike]

The reason this boat is not completed is because I feel so intimidated by the process of mast building. It seems to me that what I'll be doing is whittling a big toothpick so to speak only the measurements have to be precise.

I've come across some Douglas Fir availible in 10 to 12 ft. lenghths. The length of the mast is 16 feet and should be 3/1/2 inches square at the partner. The fir is 3 inches by 10 or 12 ft. The plan is to scarf and laminate the fir to give me 3 inches square and 20 ft. to start out with.

Would not having the extra 1/2 inch at the partner really make that much difference?

Also is there any rule that says this mast has to be round and tapered? I thought about rounding off the corners or making it eight sided at the most. I saw a classic in one of my books with a square mast with rounded off corners. It was laminated also.

Does anyone have an illustration of the scarfing method they could post?

I'm anxious to get this boat in the water and this is the last major stumbling block.

Thanks in advance.

[John Bell]

I built my Windsprint mast from solid wood instead of the box section shown on the plans. I simply glued up two 16' 2x4's and whittled away everything that wasn't mast. ;) Mine was eight sided, but it could be rounded if you wanted. You'll find a power plane helpful BTW.

WBF's own Jack Dillon had a nice article on mast making in WB a few years ago. I'd suggest you find that issue and follow his instructions. It was a very clear and concise description of the process.

[Ed Burnett]

Be a little careful reducing the size of the spar.

As an illustration, a solid section 3" square will have only 63% of the strength of one that is 3.5" square.

There is a cubic relationship between the diameter of a spar and its section modulus (the geometric property of a section which determines it's bending strength). In other words, if you double the diameter of a spar, you don't double it's bending strength, you increase it by a factor of 8.

[Ed Burnett]

Sorry, what I just said isn't that encouraging and probably increases the intimidation factor.

Spar making is great fun and really not hard at all. The two 2x4s scheme sounds like a good one and would get you back to the 3.5" square section.

Get the taper right and fair while the spar is 4 sided (i've always wondered if this is where the expression "fair and square" comes from), and its all down hill from there. Eight sided is not far from round for a spar of this size. Just be methodical about knocking the corners off and you will be fine.

[Keith Wilson]

FWIW, Birdsmouth spars are a lot easier than they look, and it's fun to be able to step the mast with one hand. You can make one with only a circular saw, a router and a plane, and it's a good way to use shorter or lower-quality stock. Two 2x4s glued together would be fine, though. I made a mast this way for my first Bolger boat 14 years ago, glued with Weldwood. It needed reglueing last year, but it's still working. Eight-sided would look nice. You can even leave it square if you like; why not?

[N. Scheuer]

Choice of wood species make a difference, too.

If the plans suggest spruce, then Doug fir of a slightly smaller section would be as strong. In fact, DF of equal section might be too heavy.

Have you seen comparative srength tables? Doug Fir is way stronger than other conifers, even approaching the numbers for Oak.

Moby Nick

[Bruce Taylor]

Using Skene's formula for an unsupported spruce mast (cube root of 16PL X Safety Factor / 15,700) I calculate that Windsprint needs a diameter of 2.94" .

You should be fine.

[Bruce Taylor]

Here's a plain-Jane (or should I say plane Jane) scarfing jig.

http://www.imagestation.com/picture/sraid134/pab31a24b92a2715e50ffbf18cd7d0127/f7710a37.jpg

The image is from Greg Rossel's Building Small Boats (if WoodenBoat doesn't consider this "fair use" I'll promptly delete it).

You'll want a 12:1 scarf. So, if your laminations are 1 1/2" thick, you'll want those wedges to be 18" long.

Don't try to laminate the full 3" mast blank and then scarf it. Scarf each of your laminations separately.

Good luck!

[chris nova]

There's a good article on "Bird's Mouth Hollow Spars" in WB 149 by Aime Fraser.

She gave a talk on this topic at the WB show in Newport a few weeks ago that was very informative. The article provides the mathematical formula for figuring the size of the staves required to produce spars of specific lengths.

[Bruce Hooke]

Jump in...it's not nearly as hard as it seems. I'm just finishing up a new canoe pole, which is basically a small mast (it's 11 1/2' long by 1 3/8" diameter at the larger end).

I will say this...while it is more work taking the pole from 8 sides to round, it's not that much more and there are a couple of advantages -- for an 8-sided pole to look good, you need to get nice crisp corners and uniform width sides. Of course, if you are planning to make the mast round it's good to have uniform width sides when you get to the 8 side stage, but if you are off a little it's unlikely to show up once the pole is round. Also, the corners on an 8 sided mast are much more vulnerable to being dented than a round pole is.

[Memphis Mike]

Thanks everyone for the info and a special thanks to Chuck. He's been sending me emails and drawings all day concerning this and I think I have enough to thoroughly cornfuss me anyhow. ;)

I understand the scarfing process though. smile.gif

[Jack Heinlen]

Mike,

Just to add a little. Making a small, round, solid spar is not terribly difficult. Someone with your ability to measure carefully, and follow unfamilar directions will find it a fun project. Read up and grok where you're going before you go. Fairing the taper is probably the most critical point. A good, light fairing batten is a must. With that, a circular saw, a simple spar gauge, a jack plane and some split sanding belts with handles on the ends and it's an eight hour project max, once the laminations are made.

Good luck.

[ 08-13-2004, 11:40 PM: Message edited by: Jack Heinlen ]

[Memphis Mike]

I saw in Tom Hill's book where he used a draw knife to make spars. Would this be easier than a plane?

[Bob Smalser]

Originally posted by Memphis Mike:
I saw in Tom Hill's book where he used a draw knife to make spars. Would this be easier than a plane?I drawknife them for speed then clean them up with a plane....but you can get into a lot of trouble with a drawknife without some practice:

http://media5.hypernet.com/cgi- bin/UBB/ultimatebb.cgi?ubb=get_topic&f=1&t=009003&p= (http://media5.hypernet.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic&f=1&t=009003&p=)

If the knife is digging too deep....stop, reverse it and clean out the cut before it chips out.

And pay close attention to your layout and your lines for a neat job:

http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=009692

[ 08-14-2004, 10:18 AM: Message edited by: Bob Smalser ]

[Jack Heinlen]

A draw knife would be a good addition to the kit for this. It would be faster than a plane, and with good attention won't get you into trouble. Same with a powerplaner, as someone mentioned. I like a plane, or even a flat soled spoke shave at times, for when you get close to the lines, and for when you go from eight sided to round. Up until that point, if your original taper was correct and you keep to your scribed lines, it's a simple matter of staying in bounds. Afterward its a matter of eye, and turning the spar often so you take it to round evenly.

Go for it Mike, you'll enjoy it once ya get over the trepidation. It's one of the most fun projects on a small boat. And even if it isn't perfect, it will work just fine.

[Jack Heinlen]

One other thing that hit me is that perhaps you aren't all that familiar with working edged tools in solid wood. Take a piece of scrap of the same wood you are making the spar out of, clamp it in a vice, sharpen your tools, and play around with it. Turn it around to get different grain orientations. Pay particular attention to grain and how the tool interacts with it. The hardest thing in using a drawknife is that attention to grain. You can be going along just fine, hit a reversal in the grain and tear a chunk out. A little practice would be a good thing.

[Memphis Mike]

Thanks again guys. smile.gif I bought a Dewalt power planer a couple of weeks ago. In playing around with it, one thing I don't understand is how do I keep from cutting too deep while following the lines the spar guage made. In other words, the lines cannot be seen while planing from the top down.

I guess I could use the power planer to remove the bulk of it and then finish with a hand plane?

Also the Douglas Fir seems like a wood that might be susceptible to splintering. I know the fir ply that I built the boat with was.

[ 08-14-2004, 11:24 AM: Message edited by: Memphis Mike ]

[NormMessinger]

As an example, say you want to reduce the thickness of your plank on one side by 1/2" over a distance of 8'. Set your power planer to take off 1/8". You will have to make four passes to cut off 1/2". Divide the eight feet into four parts. Make one cut from the first mark, another from the second, then the third then the fourth. There you have it. With a little clean up, bob's yer uncle. Do all four sides this way first then work it to eight sides then 16. I put the power planer aside after eight.

[Mhija]

I built a solid spar 28'6" overall using this scarfed method after losing an argument with a draw-bridge and the tide..... It really is fun to
see the finished product emerge from that
square hunk of timber. You can do it. Have
fun. Mine wasn't perfectly fair but nobody else
seemed to notice.....

[paladin]

Using Bruce Taylors image above, wedge the piece you are working on in the middle of the jig with a small plank on either side starting at the back of the jig to about mid jig to keep the work stable.....then use the drawings that I sent to complete the scarph.....make sure your plane is razor sharp and square, vacuum the piece, place it in a similar jig with a piece of mylar under the wood and to the sides, coat with CPES, wait overnight, add epoxy and mate two pieces together..clamp back a few inches from the scarph with blocks between the work and the clamps, tighten lightly when using epoxy, cover the scarph area with mylar and use a cinder block for a weight.....

[Memphis Mike]

Ah Chuck, you told me not to do any cutting yet. I'm stll waiting on the rest of the drawings. smile.gif

BTW, I bought eight 1x6x10 pieces of Doug. Fir yesterday. Where can I get the CPES? Jamestown Dis?

[ 08-15-2004, 05:25 PM: Message edited by: Memphis Mike ]

[paladin]

YUP...and my mast is gooped together with Schindlers T-88, now owned, pedalled, marketed whatever by System Three.....been together for a buncha years.......The bowsprit, boomlins, boom and a few other things used the same stuff...MAS had not yet arrived in the U.S. when Tana Mari wuz done...........nuthins' ever broke....

[BillyBudd]

For a boat building novice, such as I was 4 years ago, and still am today, this thread of helpful advice is a joy. A far cry from the days when some would huff and puff and try to scare away those who would dare mention epoxy, plywood, and other modes of construction not pertinent for the 1800s. Great going guys! :cool: :cool: :cool:

[Jack Heinlen]

Thanks again guys. I bought a Dewalt power planer a couple of weeks ago. In playing around with it, one thing I don't understand is how do I keep from cutting too deep while following the lines the spar guage made. In other words, the lines cannot be seen while planing from the top down.

I guess I could use the power planer to remove the bulk of it and then finish with a hand plane?
A power planer isn't much different that a hand plane in this regard, just faster, so you can get in trouble with it quicker. smile.gif Think of it like a hand plane with more mojo. You can't see the work as you run a hand plane over it either, so you develope a sense of the angle of attack, and with skill you stick with it. It's one reason I like the flat-soled spokeshave for finer stuff. You can see with that tool.

But yeah, saw it to four sided taper, scribe with the spar gauge, take out most of the waste with the power planer, finish with a jack plane, block plane, spoke shave, what have ya. Go to sixteen sided/rounded by eye, then use the opened sanding belt to finish. Works for me.

P.S. Be careful with the power planer at the ends of your tapers. There ain't much stock needs wasting there. Those are places where a spoke shave shines.

Good luck.