Pretty much the first write up of the Titan incident I've seen that is not full of unqualified assumptions and uninformed opinion. Well done on a good article!
Phil, to your point about "fixing" objects to CF structures, I do recall when working with CF masts for some sail vessels having to pay particular attention to how fittings were fastened. Example, we had designed a radar mount for these masts that used compression rings to fix them to the mast, so no holes. Great article, and thanks for bringing science [back] to the table.
Re the Titanic diver: You say it yourself:......"the compressive loading is taken primarily in the epoxy polymer matrix. However, I personally doubt that the CF reinforcing goes entirely unloaded when the composite is in compression, and I for one would want to see systematic testing to prove that claim before giving that theory any credence." The strength in compression of that eternally loaded pressure vessel is provided by the epoxy matrix. You can pull but not push on a rope. It is my conclusion, then, that high tensile strength fibers (the rope) do not add to the strength of the composite since they are loaded in the direction of their highest strength, and therefore this material was inappropriate. Also, a leak due to window failure would only equalize pressure and no implosive failure would have taken place.
You've posted this comment on the wrong thread ... but no matter really. Here is the thing, the carbon fibers will, indeed resist compressive loads when they are restrained by the epoxy matrix from deflecting in an Euler-load long-column mode. As well, even if the epoxy/carbon fiber composite is weaker in compression than in tension, it is still "stronger" than steel or titanium per unit weight. BTW, you are not correct about simple pressure equalization occurring with a breach in the pressure hull at that depth -- "An underwater implosion differs from an explosion in that energy is released inward rather than outward. The implosion generates a shock wave that compresses air and water, creating a vacuum bubble that then collapses with great force." (https://www.anews.com.tr/tech/2023/06/24/what-is-an-underwater-implosion-mythbusters-explain-it). Thanks for reading and commenting. Cheers!
We do a substantial number of refits and conversions from inboard I/O to outboards, transoms, stringers, floors and custom work. This work is always very successful financially and otherwise. While I get it that you might not be talking about smaller refits such as these, you did say "all". Possibly one of the big qualifiers is that the vast majority of projects that we do are on boats that we originally built. That one issue takes most of the guess work out of what is going to need to be done. Years back, in my more serious writing days, I wrote an article I stand by today that was titled "Cheaper to Keep Her". If you already own the boat and like it but it needs to be refit, even with substantial redesign, find the right people and do it.
But no matter, really. For the record, I was not speaking there of re-powering, but rather of plans often to completely strip an old yacht and refit or rebuild her pretty much from the keel up.
That said, I still question your claim that repowering or converting form of propulsion power always works out financially. True, if as you say you already own the boat (and likely have insurance coverage), you might be better off than in buying a new or later model used boat. But even in such cases, the issue of market value and insurability works against you. For example, I recently acquired and completely refurbed a 26-foot offshore twin-ourboard cuddy cabin boat that I wanted because she was of a type that is no longer manufactured on the new boat market. I wanted to reach back about 20 years for a usable hull and deck shell, but realized that no matter what I did in the refurb, she would still be treated in the market and by insurance underwriters as a 20 year old boat. So I settled for buying a 2014 instead. And even so, I don't think I will ever recoup even the depreciated value of the refit/refurb costs. I've always said, though, if you want to play, the ya gotta pay. Cheers!
Pretty much the first write up of the Titan incident I've seen that is not full of unqualified assumptions and uninformed opinion. Well done on a good article!
Phil, to your point about "fixing" objects to CF structures, I do recall when working with CF masts for some sail vessels having to pay particular attention to how fittings were fastened. Example, we had designed a radar mount for these masts that used compression rings to fix them to the mast, so no holes. Great article, and thanks for bringing science [back] to the table.
Re the Titanic diver: You say it yourself:......"the compressive loading is taken primarily in the epoxy polymer matrix. However, I personally doubt that the CF reinforcing goes entirely unloaded when the composite is in compression, and I for one would want to see systematic testing to prove that claim before giving that theory any credence." The strength in compression of that eternally loaded pressure vessel is provided by the epoxy matrix. You can pull but not push on a rope. It is my conclusion, then, that high tensile strength fibers (the rope) do not add to the strength of the composite since they are loaded in the direction of their highest strength, and therefore this material was inappropriate. Also, a leak due to window failure would only equalize pressure and no implosive failure would have taken place.
You've posted this comment on the wrong thread ... but no matter really. Here is the thing, the carbon fibers will, indeed resist compressive loads when they are restrained by the epoxy matrix from deflecting in an Euler-load long-column mode. As well, even if the epoxy/carbon fiber composite is weaker in compression than in tension, it is still "stronger" than steel or titanium per unit weight. BTW, you are not correct about simple pressure equalization occurring with a breach in the pressure hull at that depth -- "An underwater implosion differs from an explosion in that energy is released inward rather than outward. The implosion generates a shock wave that compresses air and water, creating a vacuum bubble that then collapses with great force." (https://www.anews.com.tr/tech/2023/06/24/what-is-an-underwater-implosion-mythbusters-explain-it). Thanks for reading and commenting. Cheers!
We do a substantial number of refits and conversions from inboard I/O to outboards, transoms, stringers, floors and custom work. This work is always very successful financially and otherwise. While I get it that you might not be talking about smaller refits such as these, you did say "all". Possibly one of the big qualifiers is that the vast majority of projects that we do are on boats that we originally built. That one issue takes most of the guess work out of what is going to need to be done. Years back, in my more serious writing days, I wrote an article I stand by today that was titled "Cheaper to Keep Her". If you already own the boat and like it but it needs to be refit, even with substantial redesign, find the right people and do it.
Thank you, Ken, for reading and commenting. However, I think you've posted your comment in the wrong thread. Unless I misunderstand, you meant to post it on https://portroyalgroup.substack.com/p/to-convert-or-refit-or-not.
But no matter, really. For the record, I was not speaking there of re-powering, but rather of plans often to completely strip an old yacht and refit or rebuild her pretty much from the keel up.
That said, I still question your claim that repowering or converting form of propulsion power always works out financially. True, if as you say you already own the boat (and likely have insurance coverage), you might be better off than in buying a new or later model used boat. But even in such cases, the issue of market value and insurability works against you. For example, I recently acquired and completely refurbed a 26-foot offshore twin-ourboard cuddy cabin boat that I wanted because she was of a type that is no longer manufactured on the new boat market. I wanted to reach back about 20 years for a usable hull and deck shell, but realized that no matter what I did in the refurb, she would still be treated in the market and by insurance underwriters as a 20 year old boat. So I settled for buying a 2014 instead. And even so, I don't think I will ever recoup even the depreciated value of the refit/refurb costs. I've always said, though, if you want to play, the ya gotta pay. Cheers!