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  #461  
Old 08-08-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by BryceGTX View Post
You are talking about two things here. Million pound forces and impact forces. These are quite different things the way I see it. You are also mixing PSI and forces.

Brent specifically mentions pounding forces from waves, so it might be interesting to determine what these pounding forces might be.

My boat, 20000 lbs, say 10000 kg, drops off a 10 foot wave into a trough. Due to dynamic forces decelerates in about a foot or so. Acceleration of gravity is 9.8 m/s^2. Deceleration is about 100 m/s^2 when it hit the bottom of the wave. So total force is.. you do the math.. 1,000,000 N or 200,000 pounds.

Now I am sure Catalina has significant design margins.. could be a factor of 5. So it seems, it is not very hard to get to 1,000,000 pounds of force.

However, again I must point out that Brents number of millions of pounds is not incorrect. But your interpretation of it seems to be incorrect.
Bryce
Actually BS was saying that his keel could take a 1.8 million PSI impact, go back and read it, if that is not what you get out of it then maybe I am wrong, but it sure looked like that was his contention. Also he is taking the linear shear maximum tensile strength and calling it the tensile strength of his hull. That is entirely incorrect. The way he is calculating it his hull would not only meet but exceed the requirements for an armored hull, but we both know that 3/16 " mild steel is not armor plate. The way that I am getting the KE figure for the impact on a solid substance ( Fukushima Debris and submerged cargo containers have been mentioned repeatedly as the potential impact sources) is a formula used to calculate the impact of a hull on a fixed and solid object such as a bridge. It figures in the weight of the boat, the forward momentum of the boat, the downward momentum of the boat, the weight of the water pushing along in concert with the boat and the duration of the impact as well as a few other little variables. I got the formula from an engineering text that is specifically focussed on just this type of impact on bridges by ships and boats.

The keel of a metal boat is just like the keel of any other boat in the fact that it will have a point at which it must either crumple, crush, bend, break off or stuff itself through the hull. Brent seems to think that this number is above 1.8 million pounds, in fact he seems to now think that it is even above 3.6 million pounds. I am simply trying to help Brent understand that not only would an impact force of significantly less than that hole his hull, it would be sufficient to completely destroyed the entire boat.

I do understand that you can strike a sandbar and survive, I have been on a boat where someone else was driving that struck a sandbar and only caused minor damage to the boat. As you well know the force of the impact and the abrupt stop are what do the damage, and if you are on the boat you get to experience that in a most painfully well demonstrated way. Sand is not a bridge pier, nor is it a floating piece of debris, Fukushima or otherwise, when you impact on sand the impact is spread out in a chain reaction over every single grain of sand for a long way. Hitting a sandbar or other soil type grounding impact is the least damaging type of impact you can have on your boat because the force is transmitted away from your boat through the individual grains of sand. In fact that same type of physics is what helps a fiberglass hull take a beating and still not be holed, the individual strands and the resin create a chain reaction that transmits the impact over a broader area to reduce the strain of a point load. This is what causes the damage to be far more widely spread than just the actual impact site on your FG hull.

Now, if you change that from sand to steel as in a container, or concrete as in a bridge pier, or a submerged log that is bedded hard against the bottom, you get far less kinetic energy being transmitted away from the impact, and more being transmitted to a focussed point. Some of the energy is still transmitted, but not nearly as efficiently, not nearly as much as when you hit a granular surface. In fact what will happen is the force then must needs be transmitted through your hull and eventually you as a passenger on the vessel. The steel corner of a submerged sea container is made specifically to withstand several hundred tons of weight being rested on it and transmitted along its frame to the deck of a ship, it is a very well designed structural point and it will give you a nice big hole if you hit it at hull speed or even lower. You simply cannot get away from that fact. A point loaded impact on that container has so much force behind it that something has to give, and sense BS boats have thin bottoms, some really strange avoidance of stiffeners and frames and other reinforcing they may flex a lot, but they are not flexing that much, and they will get a hole if the impact is just right. Not that any other steel, aluminum, wooden, FG, or composite hull is going to fair any better, every single one of them will get a hole in them if you hit that corner under the right conditions. The thing is BS seems to think that his will not, which kind of irks me a little because his ugly little boats are not going to do any better than someone else's design would do, and yet his boats spend a lot of time grinding on a reef like a stripper on a pole and get no damage.

I may not be an engineer, but I did spend the night at a Holiday Inn Express a time or two, and I can do the math. Your math is good, but it is not going to excuse a point loaded keel impact on concrete from causing damage. Even a military vessel or container ship does not get a pass when striking a solid object. You can even hole an icebreaker hull if you hit something solid enough at the right ( or wrong I guess) angle. Otherwise the Titanic and a lot of other ships would still be sailing, and you do have to admit that there have been a few ships sunk here and there with steel hulls and with other hull materials. To think you can grind on a reef, strike a cargo ship, hit a submerged container, and run aground on rocks without any hull damage is ludicrous, which I do not think you believe at all, though Brent does seem to try to use these things as a selling point for his design.

I think I had a link earlier in the thread to the engineering texts with the formulas in them, and you are more than welcome to present you theory on why the BS design is utterly impervious to all impact damage, but I am going to stand by my assertion that it is not. Also I am not comparing apples and oranges, more like fairy tales and facts, and yes I calculated the impact using force=m*a to get the number in one of those, which is quite valid. I also would not use the entire length of his hull or keel to show an impact on a small point, which is what he wants to do. When you hit that sandbar did you strike the entire keel evenly, or was it perhaps the leading edge that struck first and took the brunt of the impact? I think it would have been the leading edge most likely. If you strike at say the forward leading lower edge of one of the two keels do you think you should get to use the entire length of the keel to calculate the impact, or should you use the keel structure to model how the energy would flow? Since from what I was reading I gather BS keels are filled solid, the structural frame is going to be transmitting that point impact directly to the hull joint along the welded seam about 3/16 " wide but I am not sure how focussed the point would be. I am sure it is not going to be evenly distributed over the entire seam, most likely it would be pulling down at the leading edge and pushing up at the trailing edge about evenly causing an uh oh moment somewhere along the way.

Anyways, nice to have your input, go back and look at the formula in the bridge text and tell me what you think.
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  #462  
Old 08-08-2013
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Re: Pros and cons of steel sailboats

I have a severe allergy to ugly pilot houses. Designing in grp allows me to come up with exactkly the aesthetics I want without being help hostage by the material. Here is the molded house on the 62'er at PSC placed on the boat for the first time this morning. No question that I am very biased towards my own work but I have to say I think this looks great. I drew inspiration for this shape from the designs of Phil Rhodes. The client is very happy. Congrats to Seve Brodie and his crew at PSC in NC for their great work on this project. How can you not like working with a foreman named "Thumper"?
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  #463  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
I have a severe allergy to ugly pilot houses. Designing in grp allows me to come up with exactkly the aesthetics I want without being help hostage by the material. Here is the molded house on the 62'er at PSC placed on the boat for the first time this morning. No question that I am very biased towards my own work but I have to say I think this looks great. I drew inspiration for this shape from the designs of Phil Rhodes. The client is very happy. Congrats to Seve Brodie and his crew at PSC in NC for their great work on this project. How can you not like working with a foreman named "Thumper"?
Bob that is a very nice pilothouse. I think you will not need any benadryl at all for that one.
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Re: Pros and cons of steel sailboats

Thanks guys.
Why is it not called a "hard dodger"?

Simple. Look at the first photo. The agft bulkhead of the cabin trunk wil be extended up to the top of the PH. The oval port will be aft of this bulkhead. The top of the cabin trunk under the PH will be cut away and the PH will be over the aft cabin. There is about 40" over overhang over the cockpit so it is in effect also a hard dodger. The cockpit steps down forward so there is headroom under the overhang. We molded the boat this way so that with future boats we will have the option of having the PH or not having it.
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  #465  
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Re: Pros and cons of steel sailboats

Guess I'm confused. What I thought was my hard dodger extends aft over the cockpit enough to be a great place to perch when on watch and still stay dry and out of the wind. Sit there watching the screen over the companionway with the remote autopilot in my chubby hand and can scan the horizon. Love it. Went back and forth with the builder concerning tinting the glass. It's really two layers with a film between. He wanted it tinted for looks and to prevent a hot house effect in the tropics. I wanted it clear with two hatches over for ventilation and to see the sails. That way we might have a chance to miss the containers ( once saw a car) floating about at night. Like Micky D's got my way. Like the ovals in the back of Bob's-very elegant. ?What are the sight lines like when the pilot house feature is included. Seems just fine left as a hard dodger.Flows beautifully into the rest of deck.
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  #466  
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Re: Pros and cons of steel sailboats

Out:
Thanks I try hard.
The site lines were all worked out on the drawings to the ergonomics of the owner and his considerably shorter wife. Then we built a mock up of the entire aft end of the boat and double checked the site lines. None needed to be adjusted. The drawings were good. What we did adjust was the amount of overhang on the ph. I wanted less and the client wanted more. It turns out when the mockup was completed that he was right and I was wrong. But in this case I was happy to be wrong. We have 43" of overhang.
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  #467  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
I have a severe allergy to ugly pilot houses. Designing in grp allows me to come up with exactkly the aesthetics I want without being help hostage by the material. Here is the molded house on the 62'er at PSC placed on the boat for the first time this morning. No question that I am very biased towards my own work but I have to say I think this looks great. I drew inspiration for this shape from the designs of Phil Rhodes. The client is very happy. Congrats to Seve Brodie and his crew at PSC in NC for their great work on this project. How can you not like working with a foreman named "Thumper"?
I see absolutely nothing in those pilothouses which couldn't be far more easily built in steel. I agree, there is no excuse for uglieness in a sailboat.
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  #468  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by mark2gmtrans View Post
Brent, I hate to tell you but your math is extremely flawed. PSI is pounds per square inch, not linear inch. A36 mild steel, and that is the most common, is 36,000 PSI, linear inches could be twenty miles and it would still be a minimum of 36,000 and a maximum of 80,000 PSI in every single inch of it. The 80K PSI is not likely to happen, it would rarely test out at over 46K PSI and even that would vary greatly from one square inch to the next.

How do you calculate the hull stress loads for your vessels? What are the machinery and static loads that you figure in when you are making your calculations? What is the wave moment that you use for calculations on maximum stress loads? What wave heights? How do you calculate the stiffeners needed in the keel, hull, and deck plating loads? How do you do the hogging and sagging stress calculations on your vessels? Do you understand that your vessels, even at 30' do undergo these stress loads and that the Dynamic Amplification Factor on the steel is not just longitudinal, but it is also a shear load, a buckling load, a bending load and an impact load, even when your hull and keel are not hitting a reef somewhere?

I have an updated copy of a little workbook that you will enjoy here, if the math is too tough on you please consider a tutor, because as a ship designer this little bit of math is a bit important.

http://www.usna.edu/Users/naome/phmi...Spring2009.pdf

The rest of the guys will probably find it a good refresher on some math, and very informative. Especially on page 67 where we find this little paragraph. I think it might be an excellent thing if some people might read this and withdraw claims of absolutely no structural damage having been done to vessel which grind themselves on reefs like strippers on a pole.

Code of Ethics for Engineers
(from National Society of Professional Engineers)
Engineers, in the fulfillment of their professional duties, shall:
1. Hold paramount the safety, health and welfare of the public.
2. Perform services only in areas of their competence.
3. Issue public statements only in an objective and truthful manner.
4. Act for each employer or client as faithful agents or trustees.
5. Avoid deceptive acts.
6. Conduct themselves honorably, responsibly, ethically, and lawfully so as to enhance the honor,
reputation, and usefulness of the profession.
I just did a quick search and found that Texas Steel gives the tensile strength of mild steel at 60,200PSI, roughly what I have been told over a lifetime of steel working. So your Briex-Enron style numbers jugglings are about as credible as your claim that hogging and sagging is even remotely possible in a steel 36 footer, or your fantasy world idea of epoxy paint falling of because it is on too thick.
Your theory that you will never hit a reef if you don't think about it, is equally loony.
1 .Public safety? The Sleavins , and we don't know how many more, would probably all still be alive, had they not been discouraged from choosing a metal hull, by plastic boat salesmens' disinformation.
2. Competence? Not many of any active in this discussion have my proven track record of experience and competence in small steel boatbuilding. Most have zero . But they actively spout disinformation on a subject in which they have demonstrated zero hands on competence, or proven experience. I guess that is why I have zero competition locally in affordable small steel boat building. I hope to train some t youth this coming winter, to help keep the best steel boats affordable here.
3. Truthfull? Like misleading information on the tensile strength of mild steel, along with a lot more misleading numbers juggling Enron style, or claiming paint should be thin so it wont fall off, due to its own weight? Or suggesting that there is even a remote chance of a steel 36 footer hogging or sagging?
My statements are based on experience, decades of boat designing, building and cruising, of things that actually happened , yours on naïve , amateur speculation!
4. My clients can assure anyone that I have always been available to keep in touch and answer any questions they ask me, as well as doing a lot of pro bono consulting , in long hours, answering steel boat questions for anyone, free of any charge, unlike many designers, who charge consulting fees.
5. I don't deceive anyone .I leave that to people with zero steel boat cruising experience and zero experience maintaining and building steel boats , who spout expertise the don't have, like most on this site .
6. The honour of the profession would be best enhanced, if those who don't have the foggiest idea of what they are talking about, would educate themselves on the subject, before giving advice they are unqualified to give, or admit their lack of actual hands on experience on the subject at hand.
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
Out:
Thanks I try hard.
The site lines were all worked out on the drawings to the ergonomics of the owner and his considerably shorter wife. Then we built a mock up of the entire aft end of the boat and double checked the site lines. None needed to be adjusted. The drawings were good. What we did adjust was the amount of overhang on the ph. I wanted less and the client wanted more. It turns out when the mockup was completed that he was right and I was wrong. But in this case I was happy to be wrong. We have 43" of overhang.
With no overhand, a pilot house looks like a Volkswagon beetle, or a bald headed lady. With the right overhang ,it looks like a baldheaded lady with a baseball cap on; much better.
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  #470  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Brent Swain View Post
The honour of the profession would be best enhanced, if those who don't have the foggiest idea of what they are talking about, would educate themselves on the subject, before giving advice they are unqualified to give, or admit their lack of actual hands on experience on the subject at hand.
Brent on steel boats sounds exactly like Mark on diesel engines in boats.

Virtually word for word in fact, except Brent isn't as rude & condescending.

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