Ways to Add 6ft to the BOTTOM of a mast?

[Chotu]

I haven’t got a rigger involved yet, but does anyone know or have experience adding 6ft to the bottom of a mast?

My used mast has a very low gooseneck and is 6ft short of the proper height for this boat.

Since the gooseneck is about 6ft too low and the mast needs another 6ft anyway, I want to add that 6ft at base.

What are some ways to do this? Is there a best way?

The naval architect talked about stepping it on a 2ft box. That’s not enough.

What about a sort of sleeve as strong as the mast itself? What about a splice? The naval architect mentioned the base is a tricky spot to do this stuff because it has a lot of force acting on it.

[Catalier]

I think the sleeve idea could work, just epoxy it on really good.

[Benz]

You could build a very high, rigid tabernacle out of structural aluminum channel. I've seen boats with 6' high steel tabernacles. If you have a step welded at the proper height for the base of the mast to land on, it hardly matters what's underneath so long as it's strong enough to take it. The nice thing about aluminum channel is that you can easily drill and tap all over it for any fittings you might desire, and weld anything anywhere. If there's a chance the whole thing could wobble because there's nothing below to bolt it strongly to, you could design some sort of struts and double them as granny rails.

[Chotu]

Originally Posted by Benz

You could build a very high, rigid tabernacle out of structural aluminum channel. I've seen boats with 6' high steel tabernacles. If you have a step welded at the proper height for the base of the mast to land on, it hardly matters what's underneath so long as it's strong enough to take it. The nice thing about aluminum channel is that you can easily drill and tap all over it for any fittings you might desire, and weld anything anywhere. If there's a chance the whole thing could wobble because there's nothing below to bolt it strongly to, you could design some sort of struts and double them as granny rails.

Oooh!!!!

This is my dream rig anyway. I have always dreamed of having a tabernacle mast so I can get into interesting places.

Worth looking at.

Do you have any examples of 6ft high tabernacles on 65ft rigs?

[Chotu]

Originally Posted by Catalier

I think the sleeve idea could work, just epoxy it on really good.

This is what I was thinking too. Find a very similar if not identical (but larger) cross section and sleeve it.

[Tin Tin]

Sounds heavy and expensive + engineering expertise needed. Why not add six feet to the top of the mast, plenty of masts are sleeved somewhere in the top half, could even have it made of carbon fiber to save weight up high, it is a fast cat after all, isn't it?

[Lake-Effect]

I've seen repaired masts, with a very carefully made internal splice, and precision riveting... but I suspect that for the cost of extending, it would be the same or cheaper to find a used mast of the desired height.

[Chotu]

Originally Posted by Lake-Effect

I've seen repaired masts, with a very carefully made internal splice, and precision riveting... but I suspect that for the cost of extending, it would be the same or cheaper to find a used mast of the desired height.

Huh??? How can it be more expensive to add 6ft to the bottom of the used mast I bought than to go out and buy more masts? This seems way off.

[Chotu]

Originally Posted by Tin Tin

Sounds heavy and expensive + engineering expertise needed. Why not add six feet to the top of the mast, plenty of masts are sleeved somewhere in the top half, could even have it made of carbon fiber to save weight up high, it is a fast cat after all, isn't it?

“Why not add 6ft To the top?”

Please read the original post. It says why right in it.

I hear you on a potentially narrower tapering type top extension being lighter, but it doesn’t fit the parameters.

If the entire non-tapered mast weighs around 400lbs and I’m adding a 10% more section to the bottom, I’m adding 40-50lbs. Doesn’t sound that heavy to me.

That’s half the weight of my anchor. Half the weight of my girlfriend. At what point is weight reduction a diminishing return?

I shaved 250lbs off the windows already. That covers it. My entire engine propulsion system, power head to props and 5.3KW of generator power weighs in at 480lbs.

You’re talking about a carbon (expensive) stick at the top weighing what? 20lbs? I’m looking at 40-50lbs of a similar section of aluminum I can get at a junkyard.

Grand total difference of 20-30lbs.

I’ll take the solution that fits the parameters for 20-30lbs weight penalty any day.

[GRIT]

If you consider bridging the distance with a mount, rather than an extension, you may find you're options are also extended.

A glass mount could be made that's flat sided, wider at the bottom than the top, and blended right into the mast beam.

An aluminum mount could be bade similar to the glass mount, and if it has flat sides, would be easy to mount cleats, turning blocks, etc. It would also be a more simple structure to build, and calculate loads. Basically a compression post. It could have an access hole on the side, so you could get to your mounting bolts, through the deck. I'm just guessing, but say 20" square on the bottom, narrowing to nearly the same dimensions as the mast on the top.

Are you still going with the inside control/winch table?

Cheers.
Paul.

[Tupaia]

Much better to have the splice at the top where it could be supported by a jumper than at the bottom where the forces from the goose-neck are concentrated.


Surely a new complete section would be just as cheap, strip the fittings from the old, replace on the new and flog the old section on.

[Chotu]

Originally Posted by GRIT

If you consider bridging the distance with a mount, rather than an extension, you may find you're options are also extended.

A glass mount could be made that's flat sided, wider at the bottom than the top, and blended right into the mast beam.

An aluminum mount could be bade similar to the glass mount, and if it has flat sides, would be easy to mount cleats, turning blocks, etc. It would also be a more simple structure to build, and calculate loads. Basically a compression post. It could have an access hole on the side, so you could get to your mounting bolts, through the deck. I'm just guessing, but say 20" square on the bottom, narrowing to nearly the same dimensions as the mast on the top.

Are you still going with the inside control/winch table?

Cheers.
Paul.

This is a good idea too.

The naval architect was talking about a 2ft mount. I need a 6ft mount to avoid the complexity of moving the gooseneck.

All lines are to be turned 90 degrees and fed into the sail control table area. Yes.

Flat sides is all good by me too. As you said, easy to mount things to it.

One bit of reasoning I’m struggling with is the gooseneck forces.

So those basically pull the mast out of column athwart ships.

They would be just a couple feet above the join. The join would be getting pulled out of column by the gooseneck. I’m not seeing how the attachment would work. Or would the box be so stiff it wouldn’t bend like a mast does and it would just soak up the gooseneck forces?

[GRIT]

Yes, that's what I meant. The box is an extension of the boat, rather than an extension of the mast. The box, would act like a compression post, but have the lateral stability to replace the coachroof. I don't know if 20" square would accomplish this, but I would think it would be one of the easier methods to accomplish.

I think the sloped sides, as opposed to vertical sides, would add to lateral stability.

Same as the tabernacle idea, but without being functional as a pivot point.

As an addendum, can you put a forward extension to the cabin roof to help stabilize the lateral movement? Like a forward dodger over the forward cockpit?

Cheers.
Paul.

[Lake-Effect]

Originally Posted by Chotu

Huh??? How can it be more expensive to add 6ft to the bottom of the used mast I bought than to go out and buy more masts? This seems way off.

Labour . And where's that extra chunk of mast going to come from? I don't know how insurers would look upon a DIY mast extension.

I still suspect that if you were able to sell or exchange your current mast for a used one of the right size, you'd pay less than if you extended it. Just a guess though.

[Chotu]

Originally Posted by Lake-Effect

Labour . And where's that extra chunk of mast going to come from? I don't know how insurers would look upon a DIY mast extension.

I still suspect that if you were able to sell or exchange your current mast for a used one of the right size, you'd pay less than if you extended it. Just a guess though.

So I have to replace the shrouds (there are 3) anyway and buy a furler or foil at least. I have to put on a bow tube/beam, seagull striker and bowsprit. I have to put chain plates on and build the sail control table as well as route all the lines.

I feel like adding a little whatever to the mast base isn’t a lot of work.

Given a new rig is $65,000, I just can’t see this being too big a deal.

Maybe you’re picturing a pre-built boat?