Could use a little advice. Aluminum or Fiberglass for this?

[MicHughV]

Chotu,

The thing about sailboats is that everyone has their opinion on what may or may not work best based on their personal experience.

At the end of the day, the final decision, good or bad, right or wrong is yours, and you will have to live with it and nobody else, certainly not nameless and faceless people on this CF as they do not have a dog in this fight and can walk away at any time leaving you holding the pieces and paying all the bills.

Stepping the mast is certainly a big moment, and a tall mast doubly so, and not one that you'd want to screw up for any reason.

As a retired structural engineer, my advice, as always, is to consult with a professional, knowledgeable in these matters, as you do not want this rig to come down for any reason, especially so, while at sea or otherwise underway.

Were it me to give you advice, as would any professional, I'd want, at the very least, to come out and see the boat, the mast, rigging, chainplates, etc, as I'd likely see something that you might not and which could raise an eyebrow. Besides that, I'd want to ensure that whomever is doing any modifications to your mast is qualified to do so.

I've opined on this before, and will restate that the compression loads on the mast will be significant, as will be any compression post underneath the mast. Plus one must consider the bending moment of the mast, twisting action on the mast induced by the sail, tension in the rigging and a host of other things.

Considering the investment of time and money you've sunk into this project, seeking out professional help at this final stage of your build project, would be an insignificant amount of $$ vs. any possible calamity that could ensue if things don't go as planned.

Honestly, you are on the home stretch right now. Many of us have followed your build and trials and tribulations for some time, but this is the time to search out a qualified nautical architect or other qualified professional to see you thru' this last phase.

I understand you will also want to drop the mast from time to time to allow you access to the ICW. This too, should factor into your design decisions.

[MicHughV]

Chotu,

I hope you can open this. If you can, give it a good read.

595-540-E 6.pdf

[MicHughV]

let me try this again.

HINTS AND ADVICE - Selden Mast

[MicHughV]

one more try

https://support.seldenmast.com/files.../595-540-E.pdf

[Chotu]

That’s a good resource. I already do have that. Thank you. I also have the complete rig plan of a sister ship of mine from Selden as well. And of course the rig design in the plans I bought. I also hired a multihull designer/ naval architect before to approve buying this mast and everything. So I’m not sure what you’re getting at. What is left to hire somebody for? Maybe just talking about the plan I have for if I can’t get the metal done? Making the pyramid? Are you saying I need an engineer for that?

You must be getting pretty nervous the sail is coming up on this death trap. Ha ha ha ha ha

It’s funny. I think a lot of people just forget everything that went into this boat. And into this rig. Like I tell the story on here, but it’s not in one place so it gets lost. And then people just assume the worst.

Maybe I should remind everybody at this point.

This is a Kurt Hughes design Catamaran.
It’s vacuum resin infused using epoxy and corecell. By a team of people consisting of people that worked at Hinckley, Catalina, and NASA.
The plans were followed to a T.
Finite element analysis software was used to determine the laminate schedules and to model of the forces throughout the hull.
The rig was from a boat with the same dimensions and same righting moment. The rig was stepped on the deck house on that boat. So I need a little lengthening because mine is stepped on the deck level. Not on the roof. So it’s missing 58 inches. That has to be added.
With the extension, the rig exactly matches the plans and the sister ship.
Before I bought it, The entire rig was analyzed by a prominent multi-specialist naval architect who approved it for use on my boat.

So I really don’t understand why people tell me to hire someone. For what? I already hired everybody.

[Chotu]

I will also add that my composite chain plates were completed by someone who built tartans. Anybody familiar with those boats?

Even my helper at the boat. Doesn’t sound like much right? A helper? My helper was a prominent employee at West Marine. And he does a pretty bang up job on everything too. Plenty of knowledge there.

And that doesn’t even take into account my own approximately 35 years of continuous boat ownership and sailing. All of that experience has gone into this build. Things like no through hulls below the waterline. No metal below the waterline. Kick up rudders. Stuff like that.

I’m kind of over people on the forum thinking of my boat as a piece of crap. It’s definitely not. A lot of care and professional work went into this boat. Just because I noodle out ideas on the forum does not mean that we didn’t do a good job on the boat. I don’t know where you guys come up with that. Every time I open up a thread, it seems like people think I drew this thing up on a napkin and stuck a bunch of Play-Doh and duct tape together.

There has been nothing but professional engineering all the way through the project. I did the davits of my own design with your help, and the windows. Also decided different things like my professionally engineered options of going with metal chain plates or a composite chain plates. These are the things I have discussed on here.

And now I’m just looking at options for the extension. Which isn’t even what I was going through to begin with. I was just asking about material choices. Miraculously during this thread, some metal guys seem to be actually doing some work after about 10 months of trying to get somebody to do work. So I just might have a shot at getting the proper aluminum extension done.

[rslifkin]

If there's anything for an engineer to design, it would just be the raised mast step pyramid (to make sure you build something adequate without having to over-build it and add a bunch of weight or size).

[Chotu]

McHughV. Those posts aren’t really directed at you. Just general sentiment.

[Chotu]

Originally Posted by rslifkin

If there's anything for an engineer to design, it would just be the raised mast step pyramid (to make sure you build something adequate without having to over-build it and add a bunch of weight or size).

Agreed probably. I think. Because you’re right. If I do it it’s going to weigh too much. But I’m just hoping that these metal guys will pull through and be able to do the proper mast extension.

[MicHughV]

I hear ya, Chotu, I hear ya.

As stated above, The mast is not the issue, the mast extension/tabernacle/pyramid, whatever you want to call it, needs careful thought. This is the kind of thing, I tend to mull over in my mind for a few days, to ensure that I think of all the things that could possibly go wrong, prior to settling on a design or material selection.

This is why I, or any professional, would want to come and see the boat to get a visual of the challenge.
This would also give me an opportunity to discuss various things with you and get your feedback and ideas.
That's just how I would go about it.

[carlosproa]

Chotu
If I recall you are somewhere in east south Florida. I wonder since there seem to be so much damage in the west coast of Florida, maybe you can get a hold of part of a mast the will help you back to the extension idea. Since you built your boat exactly as the plans called for, the mast forces are already baked into the construction as long as it is in the same spot. Any deviation fore or aft may not have the same resistance than the calculated point in the design.
Mast extension is a true and tried practice and may even look better than a pirámid
Probably not what you want to hear, but as a former engineer who has not done since the 80’s any finite element analysis, I am leery of a untried design that could have demasting consequences. Better to have an ugly but safe extension if possible.

[AKA-None]

So what’s funny isn’t one has a problem with a deck stepped mast
Or a tabernacle
But all of a sudden if you solidly bolt a mast base to a deck structure it’ll fall over

The riser being proposed is an extension of the deck
Firmly attached to a support structure
Why would it fall over there rather than if it were on the deck itself
The deck structure is not bendy just because you put a riser on it which spreads the load
The mast if firmly attached to said structure isn’t going to fall over anymore than it would if sitting directly on the deck

[s/v Jedi]

Originally Posted by AKA-None

So what’s funny isn’t one has a problem with a deck stepped mast
Or a tabernacle
But all of a sudden if you solidly bolt a mast base to a deck structure it’ll fall over

The riser being proposed is an extension of the deck
Firmly attached to a support structure
Why would it fall over there rather than if it were on the deck itself
The deck structure is not bendy just because you put a riser on it which spreads the load
The mast if firmly attached to said structure isn’t going to fall over anymore than it would if sitting directly on the deck

The difference is that rake and bend will put side forces on the pyramid, while with keel stepped or deck stepped, the mast is contained there.

I felt okay with the pyramid until I read it was gonna be almost 5’ high…

[Chotu]

Originally Posted by AKA-None

So what’s funny isn’t one has a problem with a deck stepped mast
Or a tabernacle
But all of a sudden if you solidly bolt a mast base to a deck structure it’ll fall over

The riser being proposed is an extension of the deck
Firmly attached to a support structure
Why would it fall over there rather than if it were on the deck itself
The deck structure is not bendy just because you put a riser on it which spreads the load
The mast if firmly attached to said structure isn’t going to fall over anymore than it would if sitting directly on the deck

Would love to hear some comments about this post.

It is sitting on the most structurally sound piece of the entire vessel. There is an area where two extremely strong bulkheads come together. They make a T-shape when viewed from above. That’s the very spot that the mast step is located. Yes it’s directly on the T. One of those bulkheads is the main structural bulkhead that holds the boat together. The other one builds the main structural beam off of the main structural bulkhead. There are special laminates fanning out from this area in all directions and dimensions to carry the load. The load, as I illustrated for the metal guy who didn’t grasp it, can be as much as 3 Ford F-150 trucks balanced on the top of the mast.

[Chotu]

Originally Posted by s/v Jedi

The difference is that rake and bend will put side forces on the pyramid, while with keel stepped or deck stepped, the mast is contained there.

I felt okay with the pyramid until I read it was gonna be almost 5’ high…

With a 26” wide base.

So between 4 and 5 units tall, 2 units wide.

The width at the base is really important and why I nicknamed it a pyramid.

That 26” wide base would be through bolted to the deck where the mast step spot is. With monster backing plates, since I’m a big fan of those.