Spar building - cutting 45 degree corners in solid mast

Hi,

I'm currently in the middle of building spars for our sailboat, and was wondering if anybody had advice on how the make the 45 degree cuts on a solid timber spar. Our spare is 11.25 " diameter, 56 ' long so the 45 degree cuts are approximately 4 inches.

I cut the tapers with a chainsaw, and then finished with an electric plane but I'm hesitating doing the same for the corners (It's pretty rough). The last spars we built for our old schooner where much smaller, so a 7.25 inch skilsaw almost made the cut, I just finished it with a hand saw. I've looked around for a rental of a beam saw, but that's not available locally.

Thoughts, Comments, Suggestions are welcome !

Mark

 

What are you cutting at 45 degrees? Staves? Scarfs?

 

Are you talking about beveling a square timber to make it 8 sided? By "beam saw" do you mean the Makita 16-5/16" circular saw?

 

Good catch David. On most large masts, "siding" them down to 8's and 16's is usually done by hand, with a plane, power plane or even a draw knife. The "stick" is usually just too big to whittle down by other means, unless you happen to have a one huge band saw with a 3" bland around the shop. The typical course is to mark the stick, dividing the "flats" into 3 equal width lines. You place the stick in a 45 degree jig (so you can push or pull with a reference to level), though I've seen it done on the flat at an angle and whittle 'er down until you're pretty close. Once you're pretty close there's a few different ways to really fine tune the flats. On a big pole, I'd pull out the 4" belt sander and have some fun, though a hand plane is safer if set fine.

Maybe something like this might do, though setting these puppies up to make safe and accurate cuts is often difficult.

He may also be referring to a linear link kit that is attached to a regular circular saw.

 

Hi David,

Yes - I do mean to make it 8 sided and the beam saw I was thinking about is the big Makita. A local store has one in stock and it's just massive....
Here is a link to our spar building :

Building the masts and spars – Building PepeBerrou http://boatmutts.ca/building-the-masts-and-spars/

Mark

 

I'll have all the fun you need if you want to come for a visit.... lol

 

Hi Mark, maybe some tips & tricks here . . .

↓ HMS Gannet (1878), new foremast built in 2011.​

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↑ ‘‘ How to build a mast! The Renewal of HMS Gannet's Foremast ’’ ↑​

↓ Grayhound Lugger Sailing, limited discussion with Chris Rees regarding the spars for Grayhound in 2012​

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↑ ‘‘ Spars for Grayhound (large vessel) ’’ ↑​

Good luck !

 

Fir

I take it that you are making solid spars from a single timber? This is how I have done it a few times.

Once the four flats and the taper is prepared mark off the corners using a gauge as described here
http://www.boat-building.org/learn-skills/index.php/en/wood/using-a-spar-gauge/
I use a gauge with biros or pencils rather than scribing pins.

Remove the bulk of the timber with a skill saw set to 45 deg and then power plane and hand plane back to the lines. If you want a round fair mast then care at this stage saves a lot of time later.

It is important that your original square stock is actually square else the angled flats finish at different widths which add a lot to the finishing time.
I like to set up one face using a tight string line on spacer blocks to check the flatness, check for twist by laying battens across the face at the ends and middle and sight down them and then check the square and dimensions of the other faces off the first.

When I mark out the octagon corner flats I cut clean ends at each end on the mast timber and also mark out the centre, finished round and corner flats on the ends. I number the flats which helps later when converting to 16 sides as it is easy to lose track and end up over planing.

The next flats can be taken down by eye but as they begin to get quite narrow it can be confusing what has been planed and what not! Numbering and pen marking the flats can help.

The mast can be rounded reasonably well with a hand plane but for a fair round, a very coarse sanding belt with torture handles works well and is surprisingly fast. Work up and down the mast and make up some padded V blocks so that the mast can be easily rotated. I have seen this done by power with a spindle driving an inside out belt turned by a drill. The spindle had a bearing handle on the other end but for a single job it's debatable whether it's faster to do it by hand or make the spindle.

This is me planing after cutting off the corners. The corner pieces are the strips lying beside the mast.


This is rounding with a 40grt belt. At the begining I use the belt to indicate the high spots and then take them down with the hand plane.


Photos by Kevin O farrell
Kevin O'Farrell Photographer https://www.facebook.com/KevinOFarrellPhotographer/photos/a.297722902071.148019.293313657071/10152356309722072/?type=3&theater

Nick

 

FYI - I also asked this over at the wooden boat forum, and had a few good suggestions for how to make the ~4.5 inch 45 degree cuts.

Spar building - cutting 45 degree corners in solid mast http://forum.woodenboat.com/showthread.php?225888-Spar-building-cutting-45-degree-corners-in-solid-mast

Cheers,
Mark

 

Hi Nick,
This is the reason for the post - how to actually make this cut. Unless you have a beam saw (~16" dia) it's not going to have the depth.
Cheers,
Mark

 

These cuts were done long before there were beam saws. You can probably get it fairly close with a hand saw, maybe a pull saw (Japanese) if you prefer, then plane it down.

 

You will get a lot off the corner using a skill saw going in from both sides and if you were really averse to planing it and the saw was too small to get it all out you could cut the remaining inch or so by hand , it would cut quickly and the saw cuts would guide the saw. But planing is easy with a power planer, it's accurate and you can see where you are whereas it's very easy to slip up on angle cuts when using a big machine. I would cut off what you can and plane the rest.
Nick