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

[Rumrace]

One of my favourite shipwrecks to take advanced students on was modified by the owner.
While I truly appreciate modifications and even home made Ice Sailers I would not for any reason put a stack of books under a mast. A number of reasons starting with its not within my scope of knowledge.
I bought a boat with the performance mast. The boat was designed by a marine architect with compromise on 3 keels and 2 masts. I did satisfy my modifiers blood by putting Honda Serpentine anodized pulleys and a cool running alt. Upgraded batteries fun stuff.
Sell it buy a boat with a bigger mast.
Welding aluminum even T6 reduces strength by 40%
I have a 40yr old Speedmaster II on a Donzi welded twice and can’t be trusted anymore. It’s cracking around the front bearing Tossing a ZF drive on it.

A good coach roof is designed to spread the load evenly. All kinds of odd materials have failed in this void. Certainly adding a laminate would change the position of the load and cause fractures you may not see. If it were necessary I’d use PA6 (super nylon ) matching pair inside and out sandwiching the roof.
So basically a carbon fibre content puck and matching dimension interior plate. Just go over to DuPont dealer say sell me a barrel of PA6.

[danstanford]

Chotu, perhaps you should refrain from asking advice if you don't want all of it. The other possibility would be to refrain from derogatory replies to the ones you don't like.

[Chotu]

Originally Posted by danstanford

Chotu, perhaps you should refrain from asking advice if you don't want all of it. The other possibility would be to refrain from derogatory replies to the ones you don't like.

I never asked for your type of advice at all.

I get very tired of replies like yours time and time again around every corner on this project. You basically wasted electrons and didn’t offer any actual advice.

I’m always going to push those kinds of wasteful posts out of the conversation in my threads.

There is no room in here for a “can’t do” attitude of fear and failure. These threads are for creativity and adventure.

I asked a simple question of INTERCHANGEABLE material choices. You answered with “get an engineer “. Ridiculous.

My thread history here is littered with posts like you made. Have a look. Every last one of you was wrong in your fears. I moved a 59ft mast 100+ miles with a pickup truck. I built super strong davits. Etc etc. All the while some people posted their fears and “get an engineer “.

The rest of us? We figured out some cool solutions to the problems and then I built the things or moved the mast.

These threads simply aren’t for people who repeatedly post up their own fears of doing things or personal inadequacy.

I’d rather no posts like that detract from the creative process.

It’s for that reason I’m a bit harsh in steering the conversation. Because other than posts like yours, we really have something special here.

Make sense?

[Chotu]

Originally Posted by Rumrace

One of my favourite shipwrecks to take advanced students on was modified by the owner.
While I truly appreciate modifications and even home made Ice Sailers I would not for any reason put a stack of books under a mast. A number of reasons starting with its not within my scope of knowledge.
I bought a boat with the performance mast. The boat was designed by a marine architect with compromise on 3 keels and 2 masts. I did satisfy my modifiers blood by putting Honda Serpentine anodized pulleys and a cool running alt. Upgraded batteries fun stuff.
Sell it buy a boat with a bigger mast.
Welding aluminum even T6 reduces strength by 40%
I have a 40yr old Speedmaster II on a Donzi welded twice and can’t be trusted anymore. It’s cracking around the front bearing Tossing a ZF drive on it.

A good coach roof is designed to spread the load evenly. All kinds of odd materials have failed in this void. Certainly adding a laminate would change the position of the load and cause fractures you may not see. If it were necessary I’d use PA6 (super nylon ) matching pair inside and out sandwiching the roof.
So basically a carbon fibre content puck and matching dimension interior plate. Just go over to DuPont dealer say sell me a barrel of PA6.

Christ. That’s all I can say.

What on earth are you talking about? Not my boat. You’re talking about a completely different boat and offered no advice on the question

[Chotu]

Originally Posted by AKA-None

Not sure about 1/4 maybe 5/16?
I don’t like the bolt approach as you’ll likely need quite a few bolts to make it act as a single component but would make fab easier
I think you’ll need internal stringers at any rate so the plate has minimal flex areas
Just a quick reply while taking a lunch break

I’m with you.

I don’t like the bolts much either which is why I have the 1/2” or so G10 in my list of decisions. Overbuilt for sure, but direct substitution of fiberglass for aluminum involves thicker fiberglass.

I’m also with you on beefing it up a bit.

The mast itself is 3/16” aluminum however, which is why I was thinking 1/4” aluminum originally with L channel along the corners as doublers to bolt through.

[LakeSuperior]

You really don't know what you don't know.

First of all in your OP you asked about alternative construction options, not material choices. The options have large structural implications. Guessing wrong could kill you or worse kill someone else.

Also, different materials are just not equivalent. There are lots of dimensions to consider, strength, weight, corrosion resistance, etc. If they are equivalent, then there is no reason to ask CF the question? Just pick one.

In an earlier thread you were asking CF to help you read blueprints. IMHO, you need to know what your lane is and get help when you are outside that lane.

What you are trying to get from CF for free will be worth what you pay for it. A non-integrated hack of a boat. Pay a naval architect for sorely needed help.

[team karst]

Hey, isn't this your chance to put up a 63' mast so you can cruise the ICW? Sorry, cheap shot..

So, basically two mast steps, some number of feet apart. Obviously, most all in compression. So buckling is the major concern. But, also; when heavy loading occurs during a beam reach, the mast wants to tilt over, probably even offloading altogether the upwind side. So, you may now have a collapse tendency, where the upper wants to fall to port, and this new support wants to fall to starboard. Maybe consider a more serious overlap than just a simple deck step platform at the upper connection. That then, might drive a materials decision. You might not want a inner splice of AL, sitting inside another AL piece (corrosion).

[Chotu]

Originally Posted by LakeSuperior

You really don't know what you don't know.

First of all in your OP you asked about alternative construction options, not material choices. The options have large structural implications. Guessing wrong could kill you or worse kill someone else.

Also, different materials are just not equivalent. There are lots of dimensions to consider, strength, weight, corrosion resistance, etc. If they are equivalent, then there is no reason to ask CF the question? Just pick one.

In an earlier thread you were asking CF to help you read blueprints. IMHO, you need to know what your lane is and get help when you are outside that lane.

What you are trying to get from CF for free will be worth what you pay for it. A non-integrated hack of a boat. Pay a naval architect for sorely needed help.

more trash to take out. Sorry your life is so riddled with fear that you can’t do anything and are stuck doing nothing. You’re on ignore now.

I have NEVER asked anyone to help read my plans. Get checked for memory loss.

[Chotu]

Originally Posted by team karst

Hey, isn't this your chance to put up a 63' mast so you can cruise the ICW? Sorry, cheap shot..

So, basically two mast steps, some number of feet apart. Obviously, most all in compression. So buckling is the major concern. But, also; when heavy loading occurs during a beam reach, the mast wants to tilt over, probably even offloading altogether the upwind side. So, you may now have a collapse tendency, where the upper wants to fall to port, and this new support wants to fall to starboard. Maybe consider a more serious overlap than just a simple deck step platform at the upper connection. That then, might drive a materials decision. You might not want a inner splice of AL, sitting inside another AL piece (corrosion).

Excellent post. Thank you. See? That’s all you other guys had to do. Raise your question. This is a good post. It challenges the idea.

I agree with you about the buckling. It’s a major concern.

The idea to deal with this is to make it a pyramid shape. Albeit a kind of tall one.

The mast base pyramid structure is 26” at the base, heavily through bolted with backing plates, into the original mast step area it sits on.

58” tall, 26” wide. At the top, it’s flat and has a spot for the mast to sit. I should also mention there is a 1/2” thick plate riveted into the bottom of the mast. It has 4 big holes in it. These need to be attached to to hold the mast in place. So pipes have to stick up into these holes.

What do you think?

The pyramid isn’t designed to flex or move in any way. It’s designed to simply raise the mast step point up 58” to match the boat the mast came off. It had a cabin top step. Mine steps on the forward crossbeam at deck level by design. So, it’s too low.

[Breaking Waves]

Originally Posted by Chotu

1) 1/4” aluminum sheet. Welded at a machine shop hopefully before the sun ceases to shine and the solar system goes dark

2) 1/4” aluminum sheet bolted together with extra doublers at the edges

3) 3/8” or 1/2” polyester “G10” sheet. Glassed together at the sides using biax and polyester or vinylester.

4) 3/8” or 1/2” polyester “g10” sheet bolted together with doublers

From a material perspective, bolted aluminum would be my last of these choices (corrosion, paint blistering, complexities of bolt design)

My first choice would be #3 - essentially maintenance-free, and monocoque, and you know from your current coachroof structure a glass design that already works.

Related to #3, I would be curious to ask: How is the coachroof structure that was originally to be the mast step designed/constructed? Is there a ring frame in there, are parts cored, etc. My first and second thoughts would be #1 to try to tie in as best as possible to any structural frames that are there, and #2 to try to replicate the general design and build methodology. I know you are now building a different shape than the coachroof - but if there is a ring frame under the original structure, I would for example replicate that in your new structure.

[Chotu]

Originally Posted by Breaking Waves

From a material perspective, bolted aluminum would be my last of these choices (corrosion, paint blistering, complexities of bolt design)

My first choice would be #3 - essentially maintenance-free, and monocoque, and you know from your current coachroof structure a glass design that already works.

Related to #3, I would be curious to ask: How is the coachroof structure that was originally to be the mast step designed/constructed? Is there a ring frame in there, are parts cored, etc. My first and second thoughts would be #1 to try to tie in as best as possible to any structural frames that are there, and #2 to try to replicate the general design and build methodology. I know you are now building a different shape than the coachroof - but if there is a ring frame under the original structure, I would for example replicate that in your new structure.

I’m with you here. I don’t like the aluminum either.

The mast is not stepped on the coach roof. Ultimately, that’s actually the issue that needs correcting.

The mast I bought is from a catamaran with the same dimensions and righting moment and was stepped on the coach roof.

This pyramid structure is to move my deck stepped mast location up higher to be more like a coach roof stepped location, enabling the rig to fit and to be the correct air draft. Otherwise it was too short.

The designed mast step location couldn’t be more robust. It’s crazy how strong that spot it. It’s a spot at deck level.

I just need a pyramid to bring that spot up 58” so the rig becomes the same as the one in the plans.

[Chotu]

“ What you are trying to get from CF for free will be worth what you pay for it. A non-integrated hack of a boat. Pay a naval architect for sorely needed help.”

You know what I really don’t like about this?

You just called everyone contributing great ideas to the thread worthless and too dumb to contribute anything of value.

You can come after me, but I’ll be damned if you’re going to insult all the thoughtful, intelligent posts our forum members have made. These are friends I’m taking out for a sail on this death trap this winter once the rig is up.

How can you say everyone on the forum has worthless ideas and thoughts?

Clearly, it’s the exact opposite situation. There are excellent ideas everywhere from the members. From you? Well, I’d look in the mirror before condemning the whole forum to being worthless.

[team karst]

I might need a sketch to understand the 4 holes and pipes idea.
The cableway is a minor part of this, but cant be forgotten either. Thinking bottom exit or side exit?

[Breaking Waves]

Originally Posted by Chotu

The designed mast step location couldn’t be more robust. It’s crazy how strong that spot it. It’s a spot at deck level.

I just need a pyramid to bring that spot up 58” so the rig becomes the same as the one in the plans.

ok - I personally would think about using cored side panels, with a box section frame up the inside middle of each of the side panels. (eg essentially internal lateral and fore/aft ring frames inside the pedestal), and - a solid top panels. For looks - from what I have seen of your pictures it looks like your boat is 'all rounded', so I would try hard to make the corners on this thing rounded and not sharp angled.

[ItDepends]

Originally Posted by Chotu

Yes. Exactly. All of the numbers are known.

Every last one.

Only issue with your post applying to my situation as this is a Catamaran. There are no keels to step masts on. Just raising the deck step to match the height the mast was stepped at on the boat the mast came off of. It’s a bit lower location on my boat.

If you are simply raising the height of the mast step and not eliminating any kind of partners, then nothing changes on the rig design. In fact with a shorter unsupported length the mast will be a lot STIFFER than your original design. You might be able to save weight by going down a size on the lower rigging wires.

Some catamarans do have masts stepped on a lower cross beam with partners at the deck level. I used the words "keel stepped" because it was simpler. and I thought more people would understand... even without a keel the design principles are the same. It's of course the presence of the partners that add the stiffness, not the keel itself.

If you have the design specs of the mast, it seems to me the DESIGN of an aluminum box beam to support the mast would be a lot easier. You can get bending moment specs for a standard aluminum box beam. Cut beam to length, weld plates top and bottom, and bingo you have a mast step a few feet higher. If available you could even make it out of a scrap section of mast with bending moments higher than yours. I'll bet there are some scrap masts kicking around Florida right now...

You just have to be sure that the top of the new step has sufficient horizontal support. But again, I am sure you got that...

Anything out of composite materials is more of a design challenge, because they are not standardized. But (again) that is pretty obvious...