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

[Chotu]

Originally Posted by Searles

Have been thinking this through, you will external help for this but it’s simple enough, as follows use the lower section of the mast to make a mold of the section you require ,lay up an epoxy carbon new section that will be a perfect replica of the mast ,sleave and fasten ,as you cannot use epoxy you will require sone help ,the new section can be as long and as strong as you wish .⛵️⚓️

That’s what I was thinking.

I’m left with a couple questions such as maybe I can do this in vinylester instead of epoxy.

I also wonder if regular glass can be used and I just take the weight penalty.

With a mold, as you are talking about, I could infuse the project also.

While thinking about this, I’ll keep hunting for aluminum fabricators.

[Searles]

With the compression loading on the mast as a performance cat ,I would stick with carbon and epoxie ,grp with vinalester to me would not cut it .⛵️⚓️

[Sand crab]

I'm just spitballin' here.... I know about your epoxy problem but can you use prepreg carbon fiber? Mold it up dry and rig an oven and cook it.

[rslifkin]

Originally Posted by Chotu

Random question since it’s proving very difficult to find aluminum fabricators that will take on the work. Apparently, they are so busy, they don’t want the job. I’ve tried 8 so far.

Fiberglass stinks in compression, right?

There’s no way I could make the pedestal out of glass is there?


I have a great mold (the mast itself) and could put bulkheads inside the section.

Does the pedestal have to actually match the mast section? Or could you just take some large diameter, heavy wall aluminum (or stainless) tube or pipe and just attach a flat plate at each end to make a pedestal? If it's sufficiently stronger than the mast, you'd basically just be making a mast step spacer.

[zstine]

An aluminum pedestal should be very minimal fabrication. If you can weld, it should be DIY and you don't need a metal shop, just someone who can weld aluminum assuming that you can make some basic pieces. All you need as a mast section, or even rectangular tube, that's at least as stout as your mast, then weld a top and bottom plate to it. some ears or something to locate its' base and the mast step and a few tangs or pads to attach support struts. Support struts can be a simple 'A' frame welded up with plates as mounting pads to bolt to cabin top.
Aluminum is preferable over glass IMO, especially with your condition. But yes it can be glass, just will be heavy and more flexible which should be evaluated. I think you will have an uglier look trying to support FRP post as it may require more struts or stays to keep it in line. Of course higher modulus materials, aka carbon/epoxy, would help with flex and weight but will cost a lot more and there's your epoxy sensitivity... I would DIY it in Aluminum! YOU can do it!

[smj]

No luck at Dons Salvage?

[zstine]

Originally Posted by rslifkin

Does the pedestal have to actually match the mast section? Or could you just take some large diameter, heavy wall aluminum (or stainless) tube or pipe and just attach a flat plate at each end to make a pedestal? If it's sufficiently stronger than the mast, you'd basically just be making a mast step spacer.

yes, this exactly. Just make it a esthetically pleasing and at least as strong as the mast, which is much easier to design in Aluminum since he has the dimensions of the mast already. FRP will require some detailed analysis for compression and flex... don't want the rigging to slacken under load or a buckling issue do to flex of FRP.

[Sand crab]

Originally Posted by rslifkin

Does the pedestal have to actually match the mast section? Or could you just take some large diameter, heavy wall aluminum (or stainless) tube or pipe and just attach a flat plate at each end to make a pedestal? If it's sufficiently stronger than the mast, you'd basically just be making a mast step spacer.

I was thinkin the same thing. or use an internal SS structure and then wrap and then shape foam and glass on the outside to look like your mast section.


Chotu questioned whether glass stinks in compression but those carbon fiber masts sit on a mast base and that's a huge compression load right there and they survive. Also cf masts are spliced all the time. I think Chotu's thought of a pure laminated mast extension really has merit. Fabricate a proper internal splice and glue/rivet it to your old mast.

[rslifkin]

Originally Posted by zstine

yes, this exactly. Just make it a esthetically pleasing and at least as strong as the mast, which is much easier to design in Aluminum since he has the dimensions of the mast already. FRP will require some detailed analysis for compression and flex... don't want the rigging to slacken under load or a buckling issue do to flex of FRP.

Yeah, and if the solution isn't pretty enough, it would be easy enough to build a decorative fiberglass box to enclose it and make it look nice.

[Buzzman]

Originally Posted by Chotu

Random question since it’s proving very difficult to find aluminum fabricators that will take on the work. Apparently, they are so busy, they don’t want the job. I’ve tried 8 so far.

Fiberglass stinks in compression, right?

There’s no way I could make the pedestal out of glass is there?

No. There's NO way with YOUR allergy that YOU could make it out of glass.

But it ought to be feasible for a shop to do it, but it would DEFINITELY require engineering input to the design, specifiying wraps, plys and layers.

Glass is good, but only if engineered properly...

[Chotu]

Originally Posted by Buzzman

No. There's NO way with YOUR allergy that YOU could make it out of glass.

But it ought to be feasible for a shop to do it, but it would DEFINITELY require engineering input to the design, specifiying wraps, plys and layers.

Glass is good, but only if engineered properly...

I agree.

I’m just going to double down on finding an aluminum fabricator.

[Martkimwat]

What you might be able to do is get a section of alloy plate, thicker than the mast thickness, and fabricate it ( curve it) to fit as a sleeve up inside the bottom of the mast, then glass cloth over the alloy to bring it up to the same section as the mast and then paint it to match the mast, especially if the mast is already painted. you would probably need a marine architect or good rigger to confirm it would be man enough for the job. I suspect t the idea of a all glass pedestal of the size you are envisaging would be a disaster waiting to happen unless it had vey substantial side and fore and aft braces. Even a steel support of that height would be challenging. A normal tabernacle still has the mast foot resting at the bottom of the tabernacle for that reason otherwise the forces involved would try and buckle it sideways and to a lesser extent fore and aft. As an example it is quite common to the see on older boats, the glass area under the mast foot, slightly deformed by the down force of the mast and rig, even though it will most likely have been very substantially reinforced. Glass does deform slowly over time if it is under a constant stress, it is after all basically a plastic. it's why a lot of modern glass boats have additional steel reinforcing frames built in to absorb the stresses. I have seen older boats where, despite having the mast positioned over and internal plywood bulkhead, the glass has deformed allowing the mast to sit a bit lower and creating a small depressed area around the mast foot. My Parker 27 mast foot area has sunk about 6mm despite sitting over a combined 18mm bulkhead and the glass centre board box which is full height but is sloped forward so that the daggerboard opening emerges about 100mm forward of the mast foot. I am considering grinding out the area and installing a glassed in 12mm Alloy plate about 200mm x 200mm to spread the load.

[Chotu]

Wow. I didn’t see all of the other responses. All good stuff though. I think the internal pedestal like we are talking about, combined with some sort of fairing that makes it look just like the mast would be perfect.

[Chotu]

Originally Posted by smj

No luck at Dons Salvage?

Haven’t been yet. They don’t know what they have. They said just come look around. Not too handy when it’s six hours of driving to do that.

[Chotu]

Originally Posted by rslifkin

Does the pedestal have to actually match the mast section? Or could you just take some large diameter, heavy wall aluminum (or stainless) tube or pipe and just attach a flat plate at each end to make a pedestal? If it's sufficiently stronger than the mast, you'd basically just be making a mast step spacer.

And that’s basically the entire idea of the pedestal. My drawing back on page 9,534 somewhere is exactly that.

Any random larger mast section with a couple bulkheads in it would work great for this too.