Replacing Traditional Wood Masts with Alloy

[Stumble]

If you are going to seal the wood don't use CPES or any of the thinned epoxies. The solvents leave pin holes as it evaporates and results in a non-waterproof barrier. Even after seven coats it remains water permeable. Just use neat high solids epoxy.

I haven't used it in this application, but I would also think bottom barrier coat would work well here.

[mebccb]

Inspect the spar, either yourself, or professionally. If it's in good shape keep it; it will out last you if properly cared for. Any repair splices/scarfs should have a nib at each end; this reduces the chances of a glued scarf from failing due to tension peel. Nothing better than a tung oil based varnish for sealing wood; painting over the varnish will reduce maintenance from UV degradation.

[Schooner Chandlery]

Originally Posted by Stumble

If you are going to seal the wood don't use CPES or any of the thinned epoxies. The solvents leave pin holes as it evaporates and results in a non-waterproof barrier. Even after seven coats it remains water permeable. Just use neat high solids epoxy.

I haven't used it in this application, but I would also think bottom barrier coat would work well here.

The point isn't waterproofing the wood. Waterproofing is the opposite of what one wishes to have. Permeable is OK but holding water against the wood is not ok.

The benefit of a penetrating sealer is to stabilize the wood so it does not expand and contract so much with changes in humidity that it is exposed to. A surface treatment like epoxy that is insufficiently thinned is no different than using a 2-part paint on the surface that will eventually hold water against the wood under the barrier of the waterproof epoxy or paint.

About 25 years ago a series of studies were done at Purdue University geared towards understanding why brand new wood in historic preservation projects was rotting very quickly. The studies found that applying a lasting penetrating sealer (there are various kinds) preventing the expansion/contraction of the wood prevented breaking down of the surface applied paints and thus the wood was better protected from rot for a longer period by the surface coating of paint, varnish, whatever.

I hope that information is helpful.

Originally Posted by mebccb

Inspect the spar, either yourself, or professionally. If it's in good shape keep it; it will out last you if properly cared for. Any repair splices/scarfs should have a nib at each end; this reduces the chances of a glued scarf from failing due to tension peel. Nothing better than a tung oil based varnish for sealing wood; painting over the varnish will reduce maintenance from UV degradation.

Agree about real varnish then paint over it. It may do essentially the same thing as other sealants that penetrate a bit.

Question--we've used nibs in other repair applications but never in a scarfed joint on a spar. How do you propose to do this? I really can't visualize it and I've observed a professional spar maker/repair business adjacent our rebuild of our boat -- had a first row seat of all their work for many, many months and never saw a nib employed by them so don't know how it would be done. Thanks! if you can explain.

I get tension peel, but the mast is typically in compression. If you use running backstays or adjustable tension back stay to shape the mast, you can end up with tension on the forward surface of it but other than that...???

[Delancey]

I would strongly advise against any kind of shouldered scarf joint, locking or otherwise. Besides being more complicated to make, you simply cannot glue butt joints in wood. Doesn't work. If it did, then finger joints wouldn't exist.

If you have a scarf joint with a shoulder in it you are reducing the effective section area of the spar by the depth of the shoulder.

These types of joints have a place in the world, which is mainly in timber framing styles that predate modern adhesives. They typically feature much shallower tapers and rely on pins or splines to hold them together.

On the joint pictured below the shoulders work to prevent the two pieces from slipping past each other when loaded in compression.

[Delancey]

Here's a more complicated version that resists both pushing and pulling which uses a spline and pins to hold it together. See how shoulders are nearly perpendicular to the grain? Not strong if you are trying to build a mast!

[Pelagic]

The rot I discovered was localized to the areas where the spreaders were thru bolted and clamped. Over the last 33 years, this area had undergone compression stress of clamping and the wearing of original thru bolt holes causing movement.

I just received my Phytosanitary Certificate from Canada to air freight the replacement Douglas Fir (VG Architectural Quality) to Subic
....long slow process of quarantine permits and heat treatment documentation from both countries

Will post photos when I can of the stripped masts but would like to find an agreement on the paint system and manufacturer to re-coat in white , as I will need to import the paint.

[Lokiyawl]

Originally Posted by Pelagic

The rot I discovered was localized to the areas where the spreaders were thru bolted and clamped. Over the last 33 years, this area had undergone compression stress of clamping and the wearing of original thru bolt holes causing movement.

I just received my Phytosanitary Certificate from Canada to air freight the replacement Douglas Fir (VG Architectural Quality) to Subic
....long slow process of quarantine permits and heat treatment documentation from both countries

Will post photos when I can of the stripped masts but would like to find an agreement on the paint system and manufacturer to re-coat in white , as I will need to import the paint.

If you are going to import the paint, I personally would use the Epifanes Werdol primer cut about 30 percent for the first coat, apply and sand until you are happy with the smoothness, then overcoat with the Epifanes single part enamel. You could however just use a good locally available single part oil based paint to get you by until you get back to civilization. More important than the paint is to use a sealant on the fastening holes. The Douglas Fir that you bought has a good rot resistance and is stronger than spruce but does like to check. It glues well, just use straight scarfs at 10:1 or better with a good epoxy and the scarfs will be as strong as a solid pc. of wood. If you are concerned, glue up some scraps at 10:1 and break them to verify..will make you feel better. (grin) Best of luck. James

[Schooner Chandlery]

Originally Posted by Lokiyawl

If you are going to import the paint, I personally would use the Epifanes Werdol primer cut about 30 percent for the first coat, apply and sand until you are happy with the smoothness, then overcoat with the Epifanes single part enamel. You could however just use a good locally available single part oil based paint to get you by until you get back to civilization. More important than the paint is to use a sealant on the fastening holes. The Douglas Fir that you bought has a good rot resistance and is stronger than spruce but does like to check. It glues well, just use straight scarfs at 10:1 or better with a good epoxy and the scarfs will be as strong as a solid pc. of wood. If you are concerned, glue up some scraps at 10:1 and break them to verify..will make you feel better. (grin) Best of luck. James

Agree on all points.


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[Pelagic]

Thanks for the paint recommendation… I believe I can get Epiphanes in Singapore so will check availability.

My masts are made of Douglas fir.

Luckily I have a good finishing carpenter here in Subic to do what I ask, but as a newbie to Wooden Mast Repair, my challenge is to know how far to go with repairs of 33 year old Masts with an obvious history of revealed repairs. This is where I need some advice

1st Photo shows how the Mast is built

2nd Photo the worst Piece at the aft lower spreader down to radar mount that had partial rot in some places.
I will replace as a whole new piece which allowing for a 10:1 scarf is 8 ft X 6” by 1.5”
I purchased 4 pieces of 12ft x 8” x 2” Kiln Dried VG quality Fir handpicked by a carpenter friend in Vancouver, so should have lots of wood to play with.

3rd Photos show Upper Spreader which had a series of patches over the year…. Again I think I should replace with a wide solid Piece
4th Photos shows again the small rot around the upper Spreaders
Next Photos show the detail of the compression pipes I put in in 2007, the first time I pulled the mast.
I will replace all Spreader areas with new wood, but need advice on whether to use compression pipes or another solution
Lastly…How far do I go???…. Slight Discoloration and a small separation at seam.

How do you fix this kind of aging?

[Pelagic]

Opinions about this old repair at my Foremast Head?

[Pelagic]

Originally Posted by Lokiyawl

If you are going to import the paint, I personally would use the Epifanes Werdol primer cut about 30 percent for the first coat, apply and sand until you are happy with the smoothness, then overcoat with the Epifanes single part enamel. You could however just use a good locally available single part oil based paint to get you by until you get back to civilization. More important than the paint is to use a sealant on the fastening holes. The Douglas Fir that you bought has a good rot resistance and is stronger than spruce but does like to check. It glues well, just use straight scarfs at 10:1 or better with a good epoxy and the scarfs will be as strong as a solid pc. of wood. If you are concerned, glue up some scraps at 10:1 and break them to verify..will make you feel better. (grin) Best of luck. James

Thanks James....
Had to import a 2nd batch of Douglas Fir and the second round of import certificates took even longer.

Will start dry firing hardware next week before fumigation and painting

Re painting

I looked at the Data Sheet for Epifanes Werdol primer and it gave no thinner details to cut about 30 percent.

What do you recommend for thinner?

[Schooner Chandlery]

Originally Posted by Pelagic

Opinions about this old repair at my Foremast Head?

Just now saw this, sorry not to reply earlier. If that's an extra hole in there on the upper right side--not OK, but should be properly repaired to fill the void.

If not a hole then read on...

I'm used to seeing a scarfed in repair--the one you show has squared off butt-joints and that's not what I'd expect nor want. Even so, if it's holding and not looking like the wood species is too different than the fir of the spar (you'd probably have no idea about the difference in expansion/contraction properties of an unknown wood species whereas if it is fir to fir repair, you can figure they're going to expand and contract together nicely) then it's probably fine.

Good luck on getting it all together.

[mebccb]

Originally Posted by Schooner Chandlery

The point isn't waterproofing the wood. Waterproofing is the opposite of what one wishes to have. Permeable is OK but holding water against the wood is not ok.

The benefit of a penetrating sealer is to stabilize the wood so it does not expand and contract so much with changes in humidity that it is exposed to. A surface treatment like epoxy that is insufficiently thinned is no different than using a 2-part paint on the surface that will eventually hold water against the wood under the barrier of the waterproof epoxy or paint.

About 25 years ago a series of studies were done at Purdue University geared towards understanding why brand new wood in historic preservation projects was rotting very quickly. The studies found that applying a lasting penetrating sealer (there are various kinds) preventing the expansion/contraction of the wood prevented breaking down of the surface applied paints and thus the wood was better protected from rot for a longer period by the surface coating of paint, varnish, whatever.

I hope that information is helpful.



Agree about real varnish then paint over it. It may do essentially the same thing as other sealants that penetrate a bit.

Question--we've used nibs in other repair applications but never in a scarfed joint on a spar. How do you propose to do this? I really can't visualize it and I've observed a professional spar maker/repair business adjacent our rebuild of our boat -- had a first row seat of all their work for many, many months and never saw a nib employed by them so don't know how it would be done. Thanks! if you can explain.

I get tension peel, but the mast is typically in compression. If you use running backstays or adjustable tension back stay to shape the mast, you can end up with tension on the forward surface of it but other than that...???

Your right, in the fact that a mast would not normally be exposed to bending stresses, and therefore the scarf joint of a mast would not be exposed to tension. However, wood is not a stable material by nature, and tension can build up at the feather edge of a scarf just from wood movement alone. By having a nib at the ends of the scarf you provide a supporting glue joint that is in a different axis, and prevents the scarf from pealing due to wood movement. This principle is also used in designing metal weldments where the end of a weld could be exposed to tremendous localized tension and result a peel type failure.

[Terra Nova]

Originally Posted by mebccb

...a mast would not normally be exposed to bending stresses...

Plain bull.

[mebccb]

Originally Posted by Terra Nova

Plain bull.

Please explain