Replacing Traditional Wood Masts with Alloy

[Pelagic]

My 33 year old traditional schooner rigged Spruce Masts are coming off in early January for inspection and new electronics.

While all the stainless Rigging and Sails have been replaced and are still like new....The only thing I am considering is switching to Alloy Poles, before we get back into full time cruising.

I am not expecting any structural issues... just sloppy issues from showing its age and changes over the years

My thought is.... that with changing all of my mast electronics and possible weight savings aloft, now might be the time to replace while I am finishing the last of my refit.

You can see it is a simple box structure which could lend itself to internal PIPE in each of the 4 corners with flat plate on 4 sides.

Alternately, I could cost an Extrusion to be shipped to the Philippines, but I am guessing this would be expensive!!

Another plus of making them in Subic is we can reuse the Stainless Tangs and Hardware the works so well.

I am thinking that building side by side with the old old mast and hardware as a mock-up, should minimize any positioning mistakes, so that I can reuse all my standing rigging and furling system.

Thanks from any thoughts or advise from some of our Alloy structural gurus on this.

[Schooner Chandlery]

If they're Sitka Spruce and well made they're likely lighter weight than you'd be able to achieve with AL alloy masts. They will last forever if you treat them right (says me, the gal who has 84 year old wood masts (1 Sitka Spruce, 1 Douglas Fir) on her 1931 schooner. The wood is infinitely repairable, too.

That's my 2c worth.
Brenda

[Pelagic]

Hi Brenda,
Wow....looking at your fine craft, I am quite sure your advice is worth much more than the proverbial 2¢.

Stargazer was built in Holland, so not sure what type of Spruce they used.

My biggest concern is finding the right kind of wood for repairs here in the Philippines.

The quality stuff is hardwoods and the softer more flexible stuff usually have termite or powder post beetle infestation.

I will be at a good yard owned by a friend http://www.hys-yachts.com/ which is why I am researching this option

[Delancey]

My first choice would be to repair as Brenda has suggested, the only hard part being sourcing the wood since we have cut down all of the good stuff long ago. Scarfing in place is doable, I think 12:1 minimum or greater.

Alternately you could research what sizes of alloy rectangular tubing are available in your location. Here in the states extruded rectangular tubing is readily available in sizes up to about 4" x 8" x .25" in alloy types (6061 T6 and 6063 H32) commonly used for masts.

The advantage to this option being that rectangular tubing is an almost commodity-like product widely used in a variety of structural fabrications and will undoubtably be cheaper than a specialty mast extrusion from a spar maker. An example of it's use would be aluminum gangways found in marinas with floating docks.

When you find a source they will be able to tell you the weight by length which will allow to compare to what you have.

Back before there were structural engineers people built ships based on scantlings. You can do this too by researching comparable boats and their specified mast extrusions (X x Y x Wall Thickness) to figure out if the sizes of extrusions you have available would be appropriate, keeping in mind that nothing too strong ever broke.

Alternately you could get this information by contacting a sparmaker and asking them to recommend an extrusion for you. Might want to do this anyway to see what it would cost.

I would recommend against fabricating as you have suggested due to concerns about cost and quality control given the length of welding required. That's a lot of welding.

[Delancey]

Regarding repair, ideally you would match species to existing. What and where needs to be repaired?

[zeehag]

my masts are thai cedar. no, i would not dream of changing the design to make aluminum masts.
first, wood is easier to repair cheaper than aluminum.
your boat was designed with wood in mind. remember that.
when you are in boondocks and there isno welder around and your mast has broken(yeah that happens) then how ye gonna sleeve it in woodville?? there is plenty of wood and plenty of glue and clamps in this world, but it is harder to find someone out in wherethehellville to repair aluminum. but there is someone with wood and glue.... go figger.
uh, yes aluminum is trendier, but the freeking price is gonna floor ye.may better keep woood and keep the $50 000 usd for kitty or other more necessary repairs.

[Pelagic]

Thanks Zee......very good point, but I am a pretty conservative sailor as is the rig and sail plan for a motor sailor.....so unlikely I would overstress the masts.

In 2009, I stripped the Mast and saw a few plug repairs that had been routed in to probably shallow depth

Obviously minor, but still something that is an unknown.

Will know in a couple of weeks if some of the hairline cracks I see around fasteners are similar, which is why I am researching an Alloy box structure.

[Delancey]

Water infiltration at fasteners, the cause of a slow death of many an otherwise serviceable wooden mast when undetected.

One of the downsides of painting as opposed to varnishing is that it makes problems harder to detect. Paint can seem like a good idea for reducing maintenance in the short term but is usually a bad idea in the long term because of this.

Others would be well advised to fill over sized holes for fasteners with thickened epoxy to avoid this problem if they have occasion to strip a wood mast and/or stick to varnish. Preferably both.

Usually compression blocks are fitted on the interior of the box section at the spreaders which can complicate repairs if the rot goes all the way through. Otherwise, depending on how bad the rot is you are looking at simply cutting out the bad and replacing with good which isn't so bad.

There is some skilled involved in making the tapered faces of the scarf joints on either end of the patched-in piece. I mentioned 12:1 but would have to check some reference material I don't have handy, to be sure longer scarfs are better.

Prefer to repair with same species as original. If not available seek species with comparable mechanical properties. Wood database below is a good reference.

http://www.wood-database.com/?s=Spruce

[Pelagic]

Great advice Delancy and exactly the research tips I need for Alloy Masts.

As both my masts sit on deck the shape is not critical, but the rectangular section sample you showed is a lot sharper than the rounded corners of my mast.

Aesthetics only I guess, but part of the decision process

[Delancey]

Unfortunately most alloy extrusions of this type are "architectural" and have sharp corners unlike some steel shapes that are available. Not ideal I know.

As long as you stick to the minimum X x Y x Wall Thickness dimensions as a comparable specified mast extrusion you should be safe in terms of strength.

The custom mast extrusion with oval shape/rounded corners will be lighter and slightly weaker. As mentioned the custom mast extrusion will be a lot more expensive. It's all about compromise.

As far as finishing alloy, anodizing would be the first choice and is not uncommon around the world. The trick is to find someone with anodizing baths that are long enough to do a spar.

Alternately I know a very smart guy who has recommended this product. I haven't used it myself, but the guy is pretty damn smart and I would trust his recommendation.

Nyalic®

[Pelagic]

Originally Posted by Delancey

Water infiltration at fasteners, the cause of a slow death of many an otherwise serviceable wooden mast when undetected.

......Usually compression blocks are fitted on the interior of the box action at the spreaders which can complicate repairs if the rot goes all the way through. Otherwise, depending on how bad the rot is you are looking at cutting out the bad and replacing with good which isn't so bad.
.

AMEN to the moisture issue which is my biggest concern.

I would think varnish in the tropics would be a maintenance nightmare which was why I stayed with Awlgrip and used sealant in every screw after painting.
But your point is well taken and I will reconsider varnish if the different coloured plugs are not too upsetting

I was surprised when I stripped the hardware in 2009 that there were no compression Blocks at spreaders.

Instead a clamp around mast system with thru bolts to pin in place.

The holes for the thru bolts had been elongated so I installed compression pipes and a plate system to spread the load (will include photos)

It will be interesting to see if that held up OK.

[Pelagic]

Thanks for all the great advice Delancey, it is midnight here so will need to catch some shut eye and probably dream of falling masts

[Delancey]

I know. Varnish can be a bitch. The decision to paint is a totally understandable one that unfortunately comes with a downside that might not be apparent upfront to some.

Hopefully your precautions were effective and the cracks you see are no big deal. They could just be in the paint and not an indication of other problems. Awlgrip is a hard paint of a type intended for painting metal and not as flexible as some others.

Good luck with your project. Wood is good stuff and unlike other materials it grows on trees. Support responsible forestry management! Let us know how it goes.

[Terra Nova]

Replacing with an aluminum mast will almost certainly provide a measurable and noticeable performance improvement, reduce maintenance, and add value to your boat.

[Lokiyawl]

Originally Posted by Schooner Chandlery

If they're Sitka Spruce and well made they're likely lighter weight than you'd be able to achieve with AL alloy masts. They will last forever if you treat them right (says me, the gal who has 84 year old wood masts (1 Sitka Spruce, 1 Douglas Fir) on her 1931 schooner. The wood is infinitely repairable, too.

That's my 2c worth.
Brenda

Brenda is right that a well built and cared for wooden mast can last a very long time. Basically if you can protect the surface of wood and keep it at a moisture content below what is required for rot to form and progress it doesn't hardly change over time. I have rebuilt a lot of wooden spars over the years and the cause of most of the major problems comes from a lack of drainage through the mast combined with entry points for moisture. Wiring exits need a clam shell cover and exit downward. Varnish is best since you can see a problem developing very early. It is also nice to be able to look at the structure of the spar through the finish. Paint actually provides more actual protection to the wood since it stops the UV damage but with wood this type of damage is only superficial and is right at the surface. The quickest way to rot out a wooden spar is to allow water inside that cannot drain out and apply any type of sheathing or paint the prevents water vapour from passing through. I never use a two part paint on wood for this reason. Sitka Spruce is a good structural wood but you can use other stable woods for repair. A mahogany for example might be weaker per pound but due to the greater density contains more cellulose and is stonger for the same thickness. So you would add weight using mahogany but it could be structurally fine. Just try to select a stable (low expansion and contraction with moisture changes) wood with straight grain that glues well and get it quarter sawn if at all possible. Use long scarfs 10 :1 or more and you should be fine. James