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TomY

Alden Forum Moderator
Jun 22, 2004
2,648
Alden 38' Challenger yawl Rockport Harbor
One sweet boat. It's perfect. I lost track about the carbon rig - and I don't care. I'd love a long delightful cruise in that beautiful boat. I'm talking about Thunderhead!
Good taste! THUNDERHEAD would be the perfect cruiser, especially in foul weather. She has a real dog house.

Thunderhead cockpit.jpg
 
Sep 22, 2018
1,869
Hunter 216 Kingston
The lighter wooden mast is a real option.

-Will (Dragonfly)
I'm curious about the logic behind this practice.

I get there is some cosmetic value in running a conduit inside the mast but is there really that much weight savings by the time you add the weight of the glue to the layup? Maybe it's structurally stronger than a single piece??
 
Oct 19, 2017
6,884
O'Day 19 Littleton, NH
I'm curious about the logic behind this practice.

I get there is some cosmetic value in running a conduit inside the mast but is there really that much weight savings by the time you add the weight of the glue to the layup? Maybe it's structurally stronger than a single piece??
You think the weight of the glue might be significant?

For the overall weight of the mast, hollow is stronger, for the actual dimensions, solid is stronger. The loss of strength by removing the core is much less than the loss of weight. There are high end wooden racing oars for sculling shells that are made hollow because their strength to weight ratio makes sense. Wood has excellent compression strength with the grain (on an order of 2000 psi, depending on the type of wood) and even better tensile strength. That means the outer layers that take most of the forces when bending (compression force on the inside of the bend and tension on the outside of the bend), maintain the strength even without the center. I don't know what the strength ranges are for aluminum or carbon fiber, but I'd guess the strength of wood, aluminum and carbon fiber isn't enough to prevent buckling under all circumstances under sail. But I am confident I can build a wooden mast myself. The other materials, I'd have to rely on someone else.

-Will (Dragonfly)
 
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Sep 22, 2018
1,869
Hunter 216 Kingston
You think the weight of the glue might be significant?

For the overall weight of the mast, hollow is stronger, for the actual dimensions, solid is stronger. The loss of strength by removing the core is much less than the loss of weight. There are high end wooden racing oars for sculling shells that are made hollow because their strength to weight ratio makes sense. Wood has excellent compression strength with the grain (on an order of 2000 psi, depending on the type of wood) and even better tensile strength. That means the outer layers that take most of the forces when bending (compression force on the inside of the bend and tension on the outside of the bend), maintain the strength even without the center. I don't know what the strength ranges are for aluminum or carbon fiber, but I'd guess the strength of wood, aluminum and carbon fiber isn't enough to prevent buckling under all circumstances under sail. But I am confident I can build a wooden mast myself. The other materials, I'd have to rely on someone else.

-Will (Dragonfly)
Thanks for your detailed answer however yet again I don’t think I framed my question very well, let me have another go at that ;)

First the glue likely wouldn’t add much but it’s does have some impact on the finished weight.

I’m trying to understand the sailing “value” of a hollow wooden mast has over a solid mast made of the same material. I’m thinking this is more about the “thinking” that lighter is better so do everything you can to save weight.

Hypothetical - wild guess numbers here.
Let’s say a solid mast weighs 100lbs and it’s hollow equivalent is 60lbs so other than some pendulum swing differences up high and a little bit of overall boat weight difference I don’t know of any other advantage.

I do absolutely get the advantage of weight savings in anything that has to move but a mast doesn’t so ?????
 
Last edited:
May 25, 2012
3,809
john alden caravelle 42 sturgeon bay, wis
hollow wood, stika spruce, mast is stonger. 40lbs aloft is huge in my book, but that's just me.
any and all weight above the water line of a sailboat is a huge concern for me.
just like in a cargo ship, the proper placement of all cargo is very important to my sensibilities. cargo includes optional gear, say like a windless. i don't want that weight up on the bow of my 42 footer high above the waterline.
it's just choices on how you want your boat to preform.
remember, i'm the fastest :) hey hey hey
 
May 25, 2012
3,809
john alden caravelle 42 sturgeon bay, wis
thunderhead it appears has no bench seating in the cockpit. hardcore racing/sailing work area. i like it.
 
May 25, 2012
3,809
john alden caravelle 42 sturgeon bay, wis
aeolus's water and fuel tanks are in the keel. very cool placement. i love this feature.
 
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Oct 19, 2017
6,884
O'Day 19 Littleton, NH
Hypothetical - wild guess numbers here.
Let’s say a solid mast weighs 100lbs and it’s hollow equivalent is 60lbs so other than some pendulum swing differences up high and a little bit of overall boat weight difference I don’t know of any other advantage.
I'm just guessing too, but I would say your hypothetical isn't far off.
There is one other advantage I can think of. A sold wood mast on a boat of around 40' means a piece of clear, straight grained wood that was at least 16/4". Not only is that very expensive, as far as a piece of wood, but in lengths very hard to find. Either solid or hollow, it is likely that gluing up would be required and the hollow mast will be nearly as strong and only 2/3rds the price in materials.

-Will (Dragonfly)
 
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TomY

Alden Forum Moderator
Jun 22, 2004
2,648
Alden 38' Challenger yawl Rockport Harbor
thunderhead it appears has no bench seating in the cockpit. hardcore racing/sailing work area. i like it.
She has bench's but they end shy of the bridge deck, Jon. Big wide bench aft too. They only problem I see is it would be a hot cockpit on a real warm day.

How about the mainsheet winch?


Thunderhead cockpit (1 of 1).jpg
 

TomY

Alden Forum Moderator
Jun 22, 2004
2,648
Alden 38' Challenger yawl Rockport Harbor
I'm just guessing too, but I would say your hypothetical isn't far off.
There is one other advantage I can think of. A sold wood mast on a boat of around 40' means a piece of clear, straight grained wood that was at least 16/4". Not only is that very expensive, as far as a piece of wood, but in lengths very hard to find. Either solid or hollow, it is likely that gluing up would be required and the hollow mast will be nearly as strong and only 2/3rds the price in materials.

-Will (Dragonfly)
I've never seen a large spruce mast that wasn't glued up. The base often through the partners are glued up solid. Often the pieces are continuous but often joined with the joints staggered of course. Then after a half century or more many have short sections scarfed in for some repair, even after a full break.

You can nearly read the dates on the imprints the good luck coins left that are often placed at stepping.

Mast base.jpg
 
Sep 22, 2018
1,869
Hunter 216 Kingston
hollow wood, stika spruce, mast is stonger. 40lbs aloft is huge in my book, but that's just me.
any and all weight above the water line of a sailboat is a huge concern for me.
just like in a cargo ship, the proper placement of all cargo is very important to my sensibilities. cargo includes optional gear, say like a windless. i don't want that weight up on the bow of my 42 footer high above the waterline.
it's just choices on how you want your boat to preform.
remember, i'm the fastest :) hey hey hey
I think based on your answer and Will’s I’m getting it now.

I lived in BC for a number of years so had an opportunity to see standing Sitka spruce trees. Most of the specimens I saw were big in diameter, likely larger than most sailboats could/would use as a solid piece. Reduction in diameter I would think should be done in a way to preserve the natural balance of the growth rings. In other words you wouldn't want to slab off 1/4 or 1/2 of the diameter to construct the mast or you would have one side being a lot different than the opposite so the flex wouldn’t be consistent. I might be mistaken but I also have the belief that the centre portion of any tree is not as strong.

In a hollow mast you could manipulate and somewhat control grain direction, consistency and quality. It would be lighter so less weight up high.

Thanks to both of you!
 
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TomY

Alden Forum Moderator
Jun 22, 2004
2,648
Alden 38' Challenger yawl Rockport Harbor
I think based on your answer and Will’s I’m getting it now.

I lived in BC for a number of years so had an opportunity to see standing Sitka spruce trees. Most of the specimens I saw were big in diameter, likely larger than most sailboats could/would use as a solid piece. Reduction in diameter I would think should be done in a way to preserve the natural balance of the growth rings. In other words you wouldn't want to slab off 1/4 or 1/2 of the diameter to construct the mast or you would have one side being a lot different than the opposite so the flex wouldn’t be consistent. I might be mistaken but I also have the belief that the centre portion of any tree is not as strong.

In a hollow mast you could manipulate and somewhat control grain direction, consistency and quality. It would be lighter so less weight up high.

Thanks to both of you!
New spruce spars are regularly built today, especially here. Today it's harder and harder to get clear (knot free) stock, especially in Sitka spruce.

This spar was for a schooner that was built at this yard. It was all hand built of 6 pieces of square stock, glue, lots of clamps and a straight bed of horses. Shaping was largely by eye and hand plane, sanding with long boards, varnishing happened right here as well.

I guesstimate, from the core section of filler that is omitted to make a hollow spar - which would be about a board foot per linear foot - you'd average 2-3 pound a linear foot weight savings in the average hollow, 40' stick vs. solid.

Spar build (1 of 1).jpg
 
Oct 19, 2017
6,884
O'Day 19 Littleton, NH
I worked as an engineer at a local furniture factory. They owned their own lumber mill and brought rough stock into the main factory by the truck loads. Their first step after kiln drying and grading the wood was to rip it all down to 1-1/2" strips, then glue it back up to the desired sizes. With glues stronger than the wood, this allowed internal tensions in the grain some relief and made for more stable parts. They also were able to salvage good wood by cutting out the imperfections.

-Will (Dragonfly)
 
Sep 22, 2018
1,869
Hunter 216 Kingston
I guesstimate, from the core section of filler that is omitted to make a hollow spar - which would be about a board foot per linear foot - you'd average 2-3 pound a linear foot weight savings in the average hollow, 40' stick vs. solid.

View attachment 175937
So 80-120lbs lighter. Any idea of the finished weight of the spar?

I also wonder what the component is inside the cavity. Is it just a conduit or some type of structural enhancement?
 
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TomY

Alden Forum Moderator
Jun 22, 2004
2,648
Alden 38' Challenger yawl Rockport Harbor
So 80-120lbs lighter. Any idea of the finished weight of the spar?

I also wonder what the component is inside the cavity. Is it just a conduit or some type of structural enhancement?
My guess is just the hollow space around the build up which is usually rectangular in section but often oval in shape on the exterior. Having no idea the actual weight of my main mast, I'd guess (again, wildly) from the section that a 40 to 50' spar averages about 2 board feet of Sitka spruce (about 2.5 lbs/bd.ft.) per lineal foot of finished spar. That would make my spar about 200 lbs without the rigging. That alone with the metal fittings/winches, likely adds 30 - 50 lbs.

For years my family rolled the main mast to and from our boat at haul/launch, as I stored it outdoors alongside the boat.
Spar 300 wide 2.jpg


Some wooden spar photos I've taken:

The ancient boats, even if built new like GODSPEED launched in our harbor years ago, are often solid.

Godspeed spars email.jpg


There seems to be no maximum length on some of these old boats. In fact some have had extensions scarfed on to increase sail area. Easy enough to do with wood and the right skills.

Spar Thead.jpg


If spruce spars are cared for they don't seem to have a life span.

Spar work.jpg


At the yard in my harbor, they not only build the spars, they fabricate the fittings.

Adventuress spar details (1 of 1).jpg
 
Sep 22, 2018
1,869
Hunter 216 Kingston
My guess is just the hollow space around the build up which is usually rectangular in section but often oval in shape on the exterior. Having no idea the actual weight of my main mast, I'd guess (again, wildly) from the section that a 40 to 50' spar averages about 2 board feet of Sitka spruce (about 2.5 lbs/bd.ft.) per lineal foot of finished spar. That would make my spar about 200 lbs without the rigging. That alone with the metal fittings/winches, likely adds 30 - 50 lbs.

For years my family rolled the main mast to and from our boat at haul/launch, as I stored it outdoors alongside the boat.
View attachment 175941

Some wooden spar photos I've taken:

The ancient boats, even if built new like GODSPEED launched in our harbor years ago, are often solid.

View attachment 175942

There seems to be no maximum length on some of these old boats. In fact some have had extensions scarfed on to increase sail area. Easy enough to do with wood and the right skills.

View attachment 175943

If spruce spars are cared for they don't seem to have a life span.

View attachment 175944

At the yard in my harbor, they not only build the spars, they fabricate the fittings.

View attachment 175945
Works of art! Thanks for sharing.

I see your mast cart is teenager powered! ;)

The “device” that I was asking about inside the core appears to be man made. There was also something in the video that Will posted where they laid something in the core. If I zoom the photo it looks like this.

13EFCE9D-0FD9-4F4F-932F-9837CD79737C.jpeg
 
Oct 19, 2017
6,884
O'Day 19 Littleton, NH
I couldn't say what that was, just what I would do.
I notice there is a blue something or other that appears to be coming through the side wall and turning into the metal hoop. The metal hoop could be the end of a conduit tube or it could be an eye loop. There is a blue spot on the outside of the opposite wall that roughly matches, so, blue plastic conduit held in place by a metal screw eye?

I would definately install halyard conduits if I were going for internal halyard and certainly electrical conduits. They would make getting past the spreader braces much easier.

-Will (Dragonfly)
 
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