Lug sail for a dinghy - mast size and material

Hi,

I am building my first boat, a PD Racer. I want to use a balanced lugsail on it, and am wondering about size and material considerations of the mast.

My plan was to use a 2.5 meter long 2x2 as a mast (45mm x 45mm). Is this strong enough? Maybe if fiberglassed?

I have no idea what wood sizes to use for boom and sprit either. Do you have any ideas and suggestions?

Thanks a lot!

 

I had a PD Racer with s sprit sail and the sprit was close to 45mm. I cannot remember the mast was but it was bigger.
Sunfish sailboat mast 57mm and spars 37mm in aluminum.
Here is a chart from Michael Storer for the Oz-variants in aluminum:
Substituting aluminium spars on the Oz Goose sail boat - Oz Goose Sailboat - Cheap Simple Plywood Boat https://www.opengoose.com/building-a-goose/materials/substituting-aluminium-spars-on-the-oz-goose-sail-boat/


All this put together, I would do the mast between 60-70mm and also knock off the square corners of the spars (rounded octagon). Seeing pictures of square section spars is hard on my eyes. The wooden boat crowd often prefers tapering the spars for looks and weight reduction aloft.

PS:
Balanced Lug Sail Details and Dimensions By Mitch Longtin PDRacer 538 https://www.pdracer.com/boat-building/538-lug-sail/
Types of Sailboat Masts for the PDRacer https://www.pdracer.com/mast/

 

Hm ok. I think I'll take 3 2x2s, leave one whole, split one in half, and take a corner of the third one and glue all that together to form a 3x3, which I then reduce to an octagon (does that sound reasonable?)

I'll try with the 2x2s for the boom and sprit. I don't expect to sail in strong winds anyway.

I think I'll just copy the dimensions of that sail setup. Unfortunately they say very little about the mast beyond it's position.

And thanks a lot!

 

It took me a minute to understand your scheme, it looks good. There is a layout tool that one can make for the corners.

 

The wood's grain will be very difficult to balance in that configuration.

You will probably experience significant mast worpage.

 

I doubt that warpage will be much of a factor on such a small spar.Ample growth ring density and sufficient seasoning will minimise the problem in any case.

 

Hi Mario, my masts are 2 1/4 inch (~55mm) diameter oregon I think, with straight parallel grain and sides, no tapering, and about 11 feet long; I used old wooden dinghy masts. Boom about 9 feet long, and yard about 13 feet long, for a tall pointy sail.
If you have a sail already, make the spars to suit it; a company makes several sizes of standard looking lug sails, just pick the sail area you need, go a bit bigger, and put in a couple of reefing lines, then you will be ready for any conditions.
Search balanced lug sails on here, I have posted several times about them. Also search 'sail making' if you have no sail. Was out today sailing one of them in gusts up to nearly 30 knots, on my second reef. Pulled the mast out twice to go under a low bridge, very handy.

 

After considering all options I ended up buying a 3,6m long 70x70 mm long piece of pressure impregnated timber from gardening supplies. Do you think that's useable?

In imperial that's a thickness of 2 3/4 '' and a length of 11.8 feet.

It feels quite heavy, so I wonder if I should take the trouble of trying to taper it. If so, what should be the thickness at the tip? Should I seal it with epoxy?

Thanks everyone for your input!

 

Sorry
That piece of wood is very undesirable as a mast.

1. Pressure treatment destroys much of the strength of wood. So you will need a much larger diameter of stock than natural wood.
2. The treatment ingredients are extremely toxic. They are ment to kill wood eating organisms.
3. PT lumber splinters easily. Those toxic splinters will result in infection

 

Heh ok. Thanks for the warning!

Well it seems I'll absolutely will have to laminate myself a mast of other stuff. Do you think using strips of plywood glued together can make a reasonable mast?

 

Oh I found a thread on plywood masts and it seems I'll laminate other wood.

This mast business has been surprisingly challenging. I have to say I didn't expect that. They just don't sell the right shape of wood where I live.

 

You are in Sweden, plenty of spruce and aspen growing in the forests. Ask some landowner to buy one.. or two.
Spruce for mast and aspen for spars..

 

I would use spruce for mast and old carbon windsurfer mast for boom and yard- thicker end of the mast for the boom and thinner, bendier one for the yard.

 

I ended up using spruce. Three boards of 22mm thickness and 3.6 m length glued on top of each other with almost a litre PVAc glue. Then I got to learn to use the circular saw. It was a mess, and it took forever, but I'm quite satisfied with the experience and the result. Now I have a realy beautiful (to my eyes, at least) octagonal spruce mast that is 3.5m long and 6.5cm thick. That's 11 1/2 feet long and 2.55 inch thick. Thanks everyone for the help!

The next step is to assemble the boat. Let's see how long that takes.

 

Mario, you inferred that you have almost no experience with the circular saw. I am going to assume that the use of the words circular saw, refers to the portable hand held type. If you are actually a beginner with saws of that kind, please take the time to get some advice from experienced users. Discover what the term "kickback" means, Those things can be dangerous if not used correctly and very carefully.

If you are building the boat, you are likely to use the saw many more times. Give that tool all the respect that it deserves. It can permanently remove a finger in a fraction of a second and it has no conscience at all.