Pros and cons of steel sailboats - Page 46 - SailNet Community
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post #451 of 5317 Old 08-07-2013
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Re: Pros and cons of steel sailboats

Bob,

I have to say I am a bit jealous, you braved those salmon infested waters with only the protection offered by your fine choice in Hawaiian flowerdy shirts to protect you from the vicious salmon. As a fellow Hawaiian flowerdy shirt connoisseur I think the choice of the blue shirt was an excellent choice as it offers superior protection in the case of salmon attack.

I know the sailing must have been great, and even if it was on a strange tri hulled thing it was still a day spent enjoying the thrill of risking your life on the waves of the salmon infested waters of the great PNW. I will have to stop by sometime when I get back on the water next year and perhaps we can compare Hawaiian shirts and swap tales of close calls with the terrifying salmon.

It is good to learn from your mistakes, but much better to learn from the mistakes of others...
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post #452 of 5317 Old 08-08-2013
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Re: Pros and cons of steel sailboats

I was in Port Townsend today. Behind a building was some "little" wide flat bottomed 4 or 5 spreader ed rig, name of "Glory" or some such name.......in the front was something I envision came from a BS design. Not sure that thing would sail under its sails ina blinken hurricane! The keel, probably of steel like the rest of the boat appeared to be, had a flat 6" plate going forward! Talk about resistance! Mean while the keel on the other boat other than the bulb that was down at least 8-10' will swag, was all of 2-3" thick! Maybe a foot of hull in the water. The hull on the steely was at least 3-4' down, then maybe 3' of keel............

I know which of those boats would be more fun no matter the sailing I did, excepting when trying to sail on a rocky REEF some where!

Marty

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post #453 of 5317 Old 08-08-2013
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Re: Pros and cons of steel sailboats

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Originally Posted by blt2ski View Post
I was in Port Townsend today. Behind a building was some "little" wide flat bottomed 4 or 5 spreader ed rig, name of "Glory" or some such name.......in the front was something I envision came from a BS design. Not sure that thing would sail under its sails ina blinken hurricane! The keel, probably of steel like the rest of the boat appeared to be, had a flat 6" plate going forward! Talk about resistance! Mean while the keel on the other boat other than the bulb that was down at least 8-10' will swag, was all of 2-3" thick! Maybe a foot of hull in the water. The hull on the steely was at least 3-4' down, then maybe 3' of keel............

I know which of those boats would be more fun no matter the sailing I did, excepting when trying to sail on a rocky REEF some where!

Marty
Marty I think I prefer to try to sail on WATER and not on the reefs. Most likely I will be okay without a BS design.

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post #454 of 5317 Old 08-08-2013
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Re: Pros and cons of steel sailboats

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Originally Posted by blt2ski View Post
I was in Port Townsend today. Behind a building was some "little" wide flat bottomed 4 or 5 spreader ed rig, name of "Glory" or some such name.......in the front was something I envision came from a BS design. Not sure that thing would sail under its sails ina blinken hurricane! The keel, probably of steel like the rest of the boat appeared to be, had a flat 6" plate going forward! Talk about resistance! Mean while the keel on the other boat other than the bulb that was down at least 8-10' will swag, was all of 2-3" thick! Maybe a foot of hull in the water. The hull on the steely was at least 3-4' down, then maybe 3' of keel............

I know which of those boats would be more fun no matter the sailing I did, excepting when trying to sail on a rocky REEF some where!

Marty

I agree, if we would apply BS's logic to cars we would all be driving Sherman tanks.

I been biting my lip reading this thread as I have been involved in a sailboat collision. My little plastic benne was run down behind by a 45 foot Searay which was on plane at the time. over $60,000 damages between both boats but nether boat was holed or sunk. I know first hand how tough plastic boats are.

It can happen


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post #455 of 5317 Old 08-08-2013
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Re: Pros and cons of steel sailboats

mark,

I'll have to take a pic of the boat friday if I am up that way. I have to admit, it was not a "BAD" looking boat. This one looked ok overall. It is what I think one of BS's boats should look like in "orgami" construction. It had a pilot house design. which could be good around this area considering how gray it can be.......BUT, that particular design is not what I would have in mind.

On the other hand, in Port Angelas, was an older Fisher pilot house motor sailor. Even when those came out, I liked the look of them! They looked PNW at its best. Not sure how well they sail per say, but have to be better than that steely I saw today! ALong with way the heck better looking! one I could handle being seen in! or having the best women in ones life's name on the rear!

marty

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Re: Pros and cons of steel sailboats

Bubb,

Forgot about that incident! A few weeks ago, a member of my YC had there barely 4-5 month old Jeanneau 44DS hit at a dock by a big power boat too. Supposedly only caused 20K in damage.........that is the initial estimate, along with losing ANY warranty they had from Jeanneau! That has to add something to the total in some way shape or form. But the boat motored and made it back from BC into the US to the dealers yard where it is out of the water, either still waiting to get repaired, or being repaired as we speak.

From folks that saw the incident, it was scary, surprising the boat held up. As much as folks like to say Jeanneau's, Beneteau's Even Hunter will fall apart, they are stronger than one thinks.

On other fronts, HERE is a race I am doing in two weekends, if anybody can donate to the cause, please do so! any names added to the donation part, will go on an older main sail I am painting pink! One can see the person we are sailing in memory of on that page.

Marty

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Re: Pros and cons of steel sailboats

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Okay, let's address the math here....

First we need know that to figure the force of the impact, we are going to have to calculate the Impulse of Force, which is the force of the impact in PSI in this case over the period (length of time) of the impact. In order to know the force we have to know the weight, the speed and the size of the impact point, and to get the Impulse on that we need to know the duration.

From there it is a simple little calculus problem, and we can get it all done in just a few minutes. So, we figure that the length of one of Brent's keels is about 60 inches long by 6 inches wide at the point of contact. ( I tried to look up some of Brent's designs on sailboatdata.com like I do with Bob's or Roger Long's but I found this photo, and I am just kind of guessing on the actual length, at the end of the story it won't matter.

So we have a weight (per Brent) of 20,000 lbs
A hull impact area of 360 square inches maximum.
We will designate a forward hull speed of 10 knots which is 26.465 per sec
A downward force of 954417 N on the keel, and that is not a full calculation, but there are too few here who would understand the math to make it worth the effort.

So that translates to 214561.47 PSI

Score Fukushima Debris Field 1 BS hull Zero

In other words a full on 10 knot collision would poke a hole in your boat, and that force is the force that would occur along the entire 360 square inches, angle it slightly and it goes way up. I know my math is dirty on this because the formula I used was not the full formula, which gets to be fairly complex because I would have to estimate too many of the numbers. I used

Impact Force(F): 2 m vt

Which is really too simple. The actual formula for calculating keel impact force is longer and more complicated and I would have to calculate too much stuff after a very long day at work.

However for those interested the whole formula is here....

Guide Specifications and Commentary for Vessel Collision Design of Highway ... - Aashto - Google Books
It seems to me you are speaking apples and oranges. Brent is simply giving a calculation that is perfectly correct. His statement is only to give the impression that the keel is strong. And his numbers are correct.

On the other hand, you are providing a trivial collision calculation that is quite far from reality and does not reflect what sailboats do. For instance, my boat is 20,000 lbs. Real-life, I hit a sandbar at about 8 knots, stopped the boat dead. Threw us both head over heels, but did no damage to the keel or the hull.. not even a crack in the keel to hull joint. Your calculations indicate our boat was holed!!!

You are failing to include the dynamic effects of deformation of the boat or the item collided with. Inertial effects are poorly represented.
Bryce
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Re: Pros and cons of steel sailboats

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Brent,

I know you are severely challenged on the math because you just cannot in good conscious be saying that I could exert three million pounds of force on one of your thin skinned little boats and not squish it flat, much less thinking that I could give your hull a three million pound impact and not send the thing to the moon with a GIANT GAPING HOLE IN IT.

Exert a three million PSI impact on the keel and it would probably exit the hull through the deck and land somewhere on Mars.

But, I am happy if you are happy, so if you have people buying your BS boats then go forth be fruitful and multiply.
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

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post #459 of 5317 Old 08-08-2013
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Re: Pros and cons of steel sailboats

"I agree, if we would apply BS's logic to cars we would all be driving Sherman tanks."

Maybe. I was thinking more like NY Checker cabs.
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Re: Pros and cons of steel sailboats

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"I agree, if we would apply BS's logic to cars we would all be driving Sherman tanks."

Maybe. I was thinking more like NY Checker cabs.


My youngest son just got his learners permit. He has visions of a Ferrari as a first car. Dad is thinking Checker cab.


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