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AJZimm
10-22-2016, 12:59 PM
When I built my new boat, I didnít get the length of the mast just right. It could benefit from a few more inches to allow more downhaul adjustment and a better view under the boom. In short, I need to add a piece to the top of the mast. I figure the best way to do this is with a clothespin scarf, but while Iíve read about them, Iíve never done one before.

It seems to me that there are probably a number of pitfalls waiting for the unwary and/or inexperienced. The chief one Iím concerned about is how to get the scarf angles matched perfectly between the vee and the wedge and how to make sure the cuts are centred in both pieces.

Questions:

What tips and tricks do people have for making a clothespin scarf?
Are there jigs people have made or used to ensure the cuts match?
What kind of saw do you use?
How do you make sure the cuts are centred on the piece?
Should the vee be in the older, longer piece of mast or the new, shorter, added piece, or does it matter?
Anything special to consider for a birdsmouth section mast?

David G
10-22-2016, 01:11 PM
I took some fotos when I did one for a bowsprit.

https://www.flickr.com/photos/arbordg/albums/72157624466966133

1. Precise layout
2. No jigs
3. Bandsaw. But a variety of approaches could be taken. Jigsaw only. Tablesaw + jigsaw. Handsaw
4. Precise layout
5. Matters little, but my instinct would be to 'v' the stouter piece
6. You're going to have to do some fairing to blend the old with the new. Careful it doesn't skinny up things to the point of weakening the walls of the staves

MKane
10-22-2016, 01:21 PM
AJ

No expert here, but my inclination would be to add to the base of the mast.

Is it deck stepped or keel stepped ?

MK

Peerie Maa
10-22-2016, 01:22 PM
I would final fit by putting the two pieces together, without clamping the joint tight, and then running a panel saw or Japanese pull saw along the joint. That will remove any excess wood, without widening any gaps.

AJZimm
10-22-2016, 01:23 PM
David,

Thanks for jumping in so promptly. Great pictures!

Did you clean up the bandsaw cuts in any way after you made them or were you just very careful? I'm not sure I'm that good with a bandsaw.

AJZimm
10-22-2016, 01:29 PM
AJ

No expert here, but my inclination would be to add to the base of the mast.

Is it deck stepped or keel stepped ?

MK

Keel stepped.

The base is very much more complex than the top, with a reinforcing sleeve, plug and taper. Also, simple statics - the base gets much more loading than the tip. The tip addition would just be an extension of the birdsmouth section with a new plug in the end.

Ian McColgin
10-22-2016, 01:30 PM
I'd add to the bottom as that's more wood to play with and, whether deck stepped or keel stepped, less stress sideways. In your case, doing it at the bottom means it's easy to cut your notch without beating up a lot of mast. But adding to the top would probably work as well. I've seen a couple of very nice jobs that did just that. I've not a scientific structural analysis to account for my prejudice.

To the scarf, I've done a few. I did not ever have a big enough band saw and since these were big sticks I could not see horsing 40' of nice spruce through a saw anyway. I use my Japanese pull saw.

I did always make some sort of stick jig so that I could see that I had the blade aligned correctly on both sides. I always cut the female side first, carefully sanded the faying surfaces dead flat, and then fit the male. As I move in on the fit, I put carbon paper in the scarf carbon facing the male part. That helps mark the high parts and making a perfect fit. If you can't find carbon paper, put chalk over all of the female side and let that mark your highs on the male side.

A handy trick is to plane a small flat on the knife edge of the male part. Makes an easier fit to have a little void there. When the glue's dried let that be a pilot hole for a hole big enough for a dowel stopwater. You don't need a stopwater but it's a nice touch.

G'luck

Edited to add, after getting my post up saw #6. You're right. Do the top.

David G
10-22-2016, 01:32 PM
David,

Thanks for jumping in so promptly. Great pictures!

Did you clean up the bandsaw cuts in any way after you made them or were you just very careful? I'm not sure I'm that good with a bandsaw.

No cleanup required. But that stick was getting painted. One is inclined to be a bit more fastidious when it's a clear finish.

AJZimm
10-22-2016, 01:38 PM
Thanks Ian, good tips.

Brian Palmer
10-22-2016, 02:02 PM
I made a pair of oars longer by adding to the handle ends with cloths-pin scarfs. The new female ends were glued up from two pieces so I could finish the scarfs with a plane and a 12-1 sloped jig. I used the same jig for the male ends cut on the old oars. Thickened epoxy allowed for a little bit of play to keep the oars straight if the scarfs were not perfect.

Peerie Maa
10-22-2016, 02:14 PM
No cleanup required. But that stick was getting painted. One is inclined to be a bit more fastidious when it's a clear finish.

I think that as you were cutting a rectangular section the band saw will give good fits if you can follow the line. A round top end to a mast will be harder to hold "upright" on the saw for four parallel cuts. A jig, or steadying battens screwed on may be necessary.

Gerarddm
10-22-2016, 03:41 PM
Alex, I had the exact issue last month. After consulting with Hvalsoe, I added length to the base. I cut the mast first, then matched the angles to two timbers so that when epoxied together, fit the clothespin.

Tip: cut the addendum pieces oversize so you can trim down to your current mast diameter without fear of skewing the added on assembly.

MAGIC's Craig
10-22-2016, 04:27 PM
One additional suggestion: Plan on a method to keep the new pieces from "squirting away" from the rest of the mast. Epoxy makes things slippery and if you are trying to hold to a good fit without excessive glue lines, then make sure that the joint does not extend length-wise on you as it cures. I had to replace the upper 6+' of MAGIC's mainmast once and used a clothespin scarf. I followed a system like Brian Palmer described, though the mast was carefully planed with hand planes and much checking with a square. The upper two planks which made up the female portion of the joint were clamped together and then lashed to a fitting "lower down" the mast for the cure.

AJZimm
10-22-2016, 06:49 PM
A bunch more good tips.

Thanks guys!

DeniseO30
10-22-2016, 08:23 PM
Alex, if you only need a few " would a new mast step work?

Andrew2
10-23-2016, 01:39 AM
I would tempted to cut the male end on the existing mast, then make the extension out of two bits. Fitting one half first, as a simple scarf, then fettling the other to match the angle left. Bit easier than trying to cut the female end out of one piece of wood.
A2

AJZimm
10-23-2016, 12:15 PM
Alex, if you only need a few " would a new mast step work?

Good lateral thinking, but no. The mast step is in a trapezoidal mast box that is glued to the keel and integral to (i.e. glued into and airtight with) the surrounding buoyancy chamber/storage space. Much easier to add to the tip of the mast.

Peerie Maa
10-23-2016, 12:33 PM
Good lateral thinking, but no. The mast step is in a trapezoidal mast box that is glued to the keel and integral to (i.e. glued into and airtight with) the surrounding buoyancy chamber/storage space. Much easier to add to the tip of the mast.

To rephrase Denise's question. Can you drop a block into the tabernacle to lift the mast a couple of inches? How many is "a few more inches"?

AJZimm
10-23-2016, 12:47 PM
To rephrase Denise's question. Can you drop a block into the tabernacle to lift the mast a couple of inches? How many is "a few more inches"?

I need to add probably 6", haven't decided exactly how much yet. This seems to me to be a few inches in the context of a 16' mast.

The bottom of the mast box has taper wedges added to guide the mast into place easily - this is a sail and oar boat with lots of transitions from sail to oar and back again during the day, so this is a critical consideration. Adding a block to lift the heel of the mast 6" or more would not only destroy that arrangement, it would also shorten the distance between the step and the partners unacceptably and put the existing taper at the bottom of the mast right at the partner.

Ian McColgin
10-23-2016, 01:06 PM
I don't see what sort of boat she is, how big the rig, what manner of rig, or if stayed or unstayed.

Sounds like an open boat under 20' but that's just a guess. If right, probably an unstayed mast but if sloop rigged maybe not.

One good reason for knowing more is that depending upon the rig and/or alternative rigs it might well be easy to get the clearance you want without adding to the mast.

I'd also note that picking the tack up by 6" will give only slightly better visibility, especially on a breezier day when you're up on the high side. You'll likely be wanting a window in the sail no matter what.

Hoping for more info &

G'luck

Gib Etheridge
10-23-2016, 01:07 PM
Looks pretty easy to me...

http://2.bp.blogspot.com/-nHwy-cWzjgM/U2KYmYxrLsI/AAAAAAAAODo/U3Hede0MQxc/s1600/scarfholder1.jpg (http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiLpdHywPHPAhVM2WMKHXaCAM4QjRwIBw&url=http%3A%2F%2Fwww.sallyannk.com%2F2014%2F05%2Fd iy-clothes-pin-scarf-holder.html&bvm=bv.136593572,d.cGc&psig=AFQjCNHOnCwGLUN4Eqo00FpFcK4wm21AXQ&ust=1477332014647417)

Seriously though, I don't see any justification for the complexity. Why can't you just use a simple 10:1 scarf?

Jay Greer
10-23-2016, 01:08 PM
I am guessing this is a solid mast? You mentioned "Birds Mouth" so is it solid or hollow? Hollow is more challenging but can be done with patience. How big is this spar?
If it is a Bird's Mouth spar, you, as Ian Mentioned are better off scarfing from the bottom. If it is a large spar then you will be better off building a temporary spar bench in order to have a solid, flat surface that is set up for clamping. And insuring your spar and scarf are aligned correctly. I would approach the project by deciding the length and angle you want. this can be done by making a layout to scale. 1:12 is a normal ratio for such a scarf for single planks but here, if you are dealing with a solid section, I would choose to go 1:14 which will increase the faying surfaces a bit more as the bottom of the mast will take the brunt of vertical loading. I would make only one scarf allowing the new section to become the new heel. Since the shrouds carry the athwart ships load, making the jaws of the cloths pin athwart ships as well will add more support to the for and aft loading of the mast which, insures the best support for the loading of the scarf under sail. I would choose to make the center of the scarf at the partners for the wedges will lend added support as well. Making a clean cut that creates a butt that is square to the central axis of the mast is the first order of the day. Then a two line X marks the spot is made keeping in mind that these lines must be both plumb and level. You now have the width and thin center of the bottom of the cloths pin wedge. Moving back 14" and making a line around the mast at that point gives the top of the wide end of the scarf on the male section of same. Here you will begin to carve the male portion of the joint. No layout is needed here as you are only connecting two points on a flat plane. There are a variety of tools that can be used for making this cut, a draw knife, power plane and jointer plane are the three I would choose. Here you begin the rough cut with the draw knife and progress with the other tools until the tenon is dead flat on each ramp all the way to the point at the end. This means rotating the entire mast in order to align it for ease of working the tenon.
The layout of the female portion of the joint is simple as it should be made of matching the taper on two planks that end up being glued together to form the female section. Here a lot of trial fitting must be done by clamping the two planks together and sliding the extension piece over the male portion of the joint. This means applying chalk to the male tenon and slipping the new section on to it. The mast should be on its side during this fitting.
This will give you instant readings as to where a bit of stock needs removal for the optimum fit. This is best done with a low angle block plane such as a Stanley No. 9 1/2 or a newer version of it. It may take several trial fits but once you are satisfied. Gently block sand all faying surfaces with 100 grit paper and glue the whole works up using West System G/flex epoxy. Driving a temporary brad or two in the thin portion of the joint will keep it from slewing around while the clamps are being set. Once dry, all that needs to be done is a shaping of the new section to match the old plus the paint or varnish. I think varnish would be my own choice for watching the scarf as time passes.
I did one on my own boat a few years ago using a private pier as a work space. Here is the set up I used for doing a hollow box mast for the main of our H28 "Bright Star"
Enjoy
Jay
https://im1.shutterfly.com/media/47b9d625b3127ccec79daf948be900000050O00QYsmrNy5bsQ e3nwg/cC/f%3D0/ls%3D00107990352120090804164544627.JPG/ps%3D50/r%3D0/rx%3D720/ry%3D480/

Gib Etheridge
10-23-2016, 01:13 PM
Nice work Jay.

Jay Greer
10-23-2016, 01:13 PM
https://im1.shutterfly.com/media/47b9d904b3127ccec7e6fbd125b800000040O00QYsmrNy5bsQ e3nwg/cC/f%3D0/ls%3D00107990352120090725223957405.JPG/ps%3D50/r%3D0/rx%3D720/ry%3D480/

Gib Etheridge
10-23-2016, 01:20 PM
I expect you drew a crowd. I'd have stuck around to watch, would have wanted to help.

AJZimm
10-23-2016, 01:28 PM
To answer Ian's question, the boat is Fire-Drake, an 18' sail and oar lug yawl with a balanced lug unstayed hollow birdsmouth foremast (the one in question) that is about 3 1/4" dia at the partners tapering to about 2 3/8" at the tip. Mast is about 16' long, base to tip.
http://forum.woodenboat.com/showthread.php?187417-Building-Fire-Drake/page3
I realize I don't actually have any good pictures yet of the boat with the mast up.

Lots of good advice Jay - lot's of food for thought.

Peerie Maa
10-23-2016, 01:56 PM
6" off of that bury
http://i368.photobucket.com/albums/oo123/AJZimmerman/Fire-Drake/Construction%20Pics/P1090446_zpsjswg2wdk.jpg

is a lot. Many of your objections can be overcome, but that and the taper of your mast at the partners are harder to deal with.

Jay Greer
10-23-2016, 04:00 PM
I expect you drew a crowd. I'd have stuck around to watch, would have wanted to help.
We did indeed draw a crowd and met a lot of nice people. We also built some kites for our grand kids and had a lot of fun doing that too.
Jay
https://im1.shutterfly.com/media/47a6ce02b3127cceed3b56ac97dd00000030O00QYsmrNy5bsQ e3nwg/cC/f%3D0/ls%3D00107990352120161023205613431.JPG/ps%3D50/r%3D0/rx%3D720/ry%3D480/

Ian McColgin
10-23-2016, 04:09 PM
It looks to me like the boat was made to have the tack pretty low. Sure you want to raise it?