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

[Chotu]

Originally Posted by 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.

Hmmm.

So I could take the 2ft box step the naval architect was talking about, add 4ft and make the base wide enough it can’t move/flex.

Unfortunately I put steps in the middle there so a brow wouldn’t work. It’s the only way to get on the roof.

This is a winner though! Thanks!

[AKA-None]

Wouldn’t a 6 ft tabernacle need to be taller than 6 ft to get the total 6 ft extension you want? You would need part of the existing mast inside of the tabernacle

[rslifkin]

If you go with the mast step on a box idea, maybe build some kind of detachable mast cradle for the top of it? Then when you get to inland cruising, you've already got 1 part of a sturdy system to carry the mast along with you.

[wholybee]

I would not attempt this without an engineer. The mast is under compression, and will tend to bow out. The highest loads are towards the bottom where the gooseneck and boom add additional side loading forces and angles.

If you have a step that is 6 feet high, there are going to be side loads that will tend to knock it out of place. You might need to make the base 6 feet cube and not be a column, or add stays to hold the top of the stand in place. An engineer could determine the loads, based on the rest of the rig, and tell you what it needs to be.

Maybe you would get lucky and be told no problem. But it's to big a risk to the integrity of the boat to not have an engineer actually do the analysis.

[Lake-Effect]

Originally Posted by Chotu

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

Maybe you’re picturing a pre-built boat?

6 ft isn't "a little" - on the mast or on the base. (I am assuming this is a deck-stepped mast.)

I just think that it would likely be better & cheaper to sell your mast that's X long and buy one that's X+6 long, as opposed to the effort and risk of a DIY extension.

^ last word, I won't belabour the point. Best of luck in any case.

[Adelie]

Originally Posted by 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.

Is the mast deck stepped or keel-stepped? I presume deck stepped or you wouldn't be asking.

If you are going to add to the bottom I would weld on a new section, either:
A. A groove weld all around if you can find the same section to splice
or if you can't then
B. Use an oversized section cut an extra 2' long with some vertical slots cut in the sleeve section near the bottom of the overlap. Fillet weld the top of the overlap and plug weld the slots.

Problem with A. is finding the exact same section.
Problem with B. is finding an oversized section that is a tight fit. The boltrope slot for the oversized section will need to be cut out so that will make things slightly easier.

[Cheechako]

Originally Posted by 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.

A sleeve inside, structural epoxy and proper rivets. Rigging companies do this sometimes. Or just butt weld it. The weld is in compression mostly. Not the greatest location 6 foot up from the cabin for an unreinforced butt weld though. .... I'd probably sleeve it anyway. You'll want to move the spreaders too...
Structural epoxy is not epoxy resin, it's thick like paste and very strong and not so brittle.
I dont get it, how in the world can a gooseneck be 6 ft too low.????

[Chotu]

Still reading these while working right now. But I wanted to answer cheekao’s question.

Spreaders don’t need to move. Those would be in the right place already. Just need to buy new shrouds which I am doing anyway.

Then, the reason it is 6 feet too low is that it is from a boat with just about no deck house. And the deck house it has is way down by the water. Mine is up high. Creating a lot more of a bridge deck clearance.

[GreenWave]

Chotu- I have to hand it to you. You always post very intriguing project questions.


Is it possible to move the gooseneck attachment point higher on your current mast and then add to the top? Otherwise, I like the "compression post-like box" addition.

[zstine]

A 6ft box is doable, but it's not going to be cantilevered off the deck. Your going to need struts I'd think... going to be ugly... Consider moving the gooseneck. should be straight forward. Yes, I understand that there are other things that will likely need to move but still likely easier than engineering and building a 6ft tall box to step the mast. That is not a trivial job as it will require deck mods for bending loads and/or strut mounts vice the compression loads the deck was designed for. You can abandon the old gooseneck and just install one higher and move a few other parts. in like 1 day.

Splicing the mast up high is fairly easy and common practice (lower loads than down low), if you can get the same section that is. The internal splice piece can be made by cutting vertical slice(s) in the full section and closing the gap.. Then its just a bunch of screws (at least in my mast). I am assuming you have lower shrouds and not full height shrouds with diamonds..? A splice down low is even better than a box to step it on. Think of the step as a ball joint! MUCH Better to keep it one piece!!

[stormalong]

I didn't see that you answered the question of: Is this keel stepped or deck stepped? If it is keel stepped convert to deck stepped and put a jack post under it.

If you can get a piece of the same extrusion a sleeved joint would work. I would never trust an aluminum weld alone to be strong enough. A mast extrusion is tempered, a weld is not and aluminum welding is not anywhere near as strong as the mast section which is why mast joins are sleeved. A sleeve can be welded and look like the mast is continuous if it is painted and would be plenty strong.

Is the gooseneck welded to the mast? Moving a gooseneck in not a big deal unless it is welded. If it is welded a new gooseneck could be added and the existing one could be the base for a rigid boom vang.

The only issue I see to just moving the gooseneck is the reduction of sail area.

[OS2Dude]

Originally Posted by Chotu

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

Boats with Selden masts usually have a splice 3 or 4 feet above the deck since they ship them in 40' containers. See if you can find any in your marina and look how they're done. I believe Jeanneaus and Beneteaus are that way.

Mast Splicing article/

youTube video on splicing a mast.

[Chotu]

The rig looks like this. Kind of. I don’t think the gooseneck is in the diamond though. But I’ll check it now.

Edit: the gooseneck is welded on and 6” into the lower diamond. So, almost just like this.

[thunderhoof]

I had a Schock 35 mast repaired by the method of splicing together the useful portion of the upper mast with a section of lower mast from another boat. There was about 3 ft of internal splice plates with many rivets. It worked well. Most boats do not use super custom mast sections. There are standard sections available and many mast sections in boatyards everywhere.
I think a more pressing issue is the location of spreaders on the newly stepped mast. I would get expert advice on this issue.

[Lake-Effect]

Originally Posted by thunderhoof

I had a Schock 35 mast repaired by the method of splicing together the useful portion of the upper mast with a section of lower mast from another boat. There was about 3 ft of internal splice plates with many rivets. It worked well.

If you don't mind my asking, roughly how much did the repair cost?