What to use under stringers

Sure, say for instance the boat is 50 feet, the longitudinals (floor stringers) would be something like 10 inches high and 4 inches wide. They would be made from foam, cut to size and shaped to suit the application. The transvers frames would be exactly the same. I would expect to see 6 to 8 of these in the bottom of the boat running full length and tapering in height from the fwd cabin into basically nothing by the time they reached the bow.. The transverse floors would be about 6 feet apart and fill in the whole of the bottom of the boat. You have to consider tanks and other spec fittings that go into the build, so don't just jump in and do all this form work without carefull considering placement of everything that has to go into the boat.
Tank bases are made to suit the tanks, the longitudinals (stringers) would be set to suit these. Bulkheads are just inserted as per normal, allow 1inch of foam where they touch the topsides and glass into place. It pays to remove some of the ply layers when tabbing in the bulkheads to allow for the plywood veneers that go over the bulkheads to pretty them up.

All of the sub floor framing, ie longitudinals and transverse floors are the grid that is the structural beam of the bottom of the boat, they form the backbone to support all of the other junk we have to add later. The hull spec thickness is determined by this formwork as well, as the closer the frames are to each other , the thinner the hull bottom can be. Generally on a 50 footer the bottom would be about 5/8 to 3/4 inch thick. topsides would be about 1/2 inch.

 

WOW, great LL,
just give me a couple of hours to digest this:

(let me see 0:2:15 in USA means 1600 pm Australia time) am I close?

 

Yep, sorry to keep you out of bed!

 

Anyone can design a boat structure.

It takes an engineer to build one that is light enough to perform well beyond the average boat of similar dimensions and strong enough not to fold in on itself when the going gets tough.

Engineers are little more then practitioners of safe, but light weight construction methods and technique.

Ratrace2, this is a poor venue to gain an understanding of the principles and concepts related to basic marine engineering (or any engineering for that matter). Out of the box thinking is wonderful, as long as it's not much more then blowing air through a soda straw, just to see the bubbles in your drink.

 

Yeah PAR, you are soooo right.

It is difficult for some people to get the basic grasp on what design is all about, it is certainly not making pretty pictures.

It is also very dangerous for people using these sort of web sites to get a real understanding of boats and boatbuilding, unfortunately many writers write articles here on things that they really have had very little practical experience in, they simply copy cat someone elses statements, as if they were fact. The "facts" are then translated in their own minds as being reality, whereas the opposite is often the truth, they are simply opinions, written by an unidentified author that may or may not be "fact" at all.

You of course use your real identity, I use LL simply because I am employed by major yards, and have no right to use their pics or designs in the outside world, so can only talk in limited areas. I do however have 50 years of boatbuilding experience, currently working in China, and seeing many horrendous building practices. Monkey see, monkey do is the way of life here, but also on this web forum, when "facts" are simply copied opinions.

Caveat Emptor, but please, all would be builders, take PARs advice, and get real expert knowledge, not some "armchair admiral" who would not really know what a boat looks like.

 

Par,
You say, "Ratrace2, this is a poor venue to gain an understanding of the principles and concepts related to basic marine engineering (or any engineering for that matter)." I'm going tooooooooo, respectfully, disagree.

Let's look at it from a different perspective; let's say, for example, someone wants to know what makes something "tick". what do we do? we start asking questions, right.

 

LL,
buddy, you are the best in every way. And, I promise, I will get an NA to crunch the numbers and review everything before I do it....

 

Lets put it to the test:

OK, so we have this guy that wants to replace the stingers in his boat; we have another guy that wants to understand the design and engineering of stringers. What is our first step, i.e. "Best practices"...
Par, LL:
What is step one.
What is step two.

 

Well, put that way, you want to replace the stringers. Assuming they are still there, the guess would be to replace them with something that closely resembles the original dimension.

Now to design and understand the engineering of stringers, well, i could say ask PAR, or i could try to answer myself.

We have already gone over the basics of how the longitudinals form the backbone of the boats hull bottom. Engineering wise, the thicker the beam the greater the stiffness implied. So yes 8 inched in moulded depth would be better than 6 inches. But be careful here as the hull bottom may be designed to allow for a certain amount of "bend" in its operation. Not likely however in the real world, we actually try to make them stiff, as flexing is simply another word for slowly breaking up. Any material can only flex a certain number of times, so it is generally not a design input, but in some cases it actually is, hence the caution not to overbuild the bottom.

Now if "you mate who wants to know this" can just chop out the stringers that are there, I would simply replicate them and glass in the new ones.

 

I think the above picture has a pretty graduated blue background.

My point is if you make substitutions, you have to understand the concepts or you could be aiming a loaded pistol at your foot.

It's one thing to make alterations, repairs, upgrades, need advise on rewiring something and another to absorb a specific element of fundamental engineering or yacht dynamics.

In the regard to the latter, this is a poor place to get an education. A useful education requires work on the part of the student. Research, lots of reading, well conducted guidance through the many principles, theories, concepts, history and subtleties of yacht design adn engineering. The web is a great place for a quick grab of undocumented information. In truth, it's not reliable, often flawed and usually not acceptable in a strict discipline for learning engineering related subjects.

In other words, if you want to quickly find out the specific gravity of a cubic foot of cow dung, you could cross reference an on line search enough times, to insure reasonable accuracy. If you want to find out what cows ****, then you're much better off going to a veterinary school and getting an education.

An example is the interest in using aluminum stringers. With an understanding of the materials involved, you'd quickly see the difficulties. My library currently has about 100 different "boat books" as the one how must be obeyed calls the several shelves they occupy. Okay, I've collected many over the years, but I also use many regularly too. These "reference" books are invaluable to me, much like a real library's reference books which can't be taken out.

Ratrace, you need to get a healthy library going. The book store here can offer many titles or you can use these titles and find better deals at used book sellers. With the exception of some books, most can be had very inexpensively at on line re-sellers.

I'm not trying to be coy with you. It's just that persistence in a particular idea, request or concept isn't going to change things for you, only an education (it sucks when you realize you parents we right) in the subject(s) you desire will be helpful. You can self medicate with books, take a class, find some work in a marina or boat shop, but ultimately you'll be happier with knowledge gained though work (bearing your nose into a book is work too), rather then the seemly free ride, many on line experiences can be.

 

Par, you are 100%, totally, on the money, right. So you can be my NA, what's the retainer?

 

Fees and services should be discussed off this venue. Contact me (click on my name) by email.

 

conclusion?

Hey everyone. Was there any agreement on what should be used under the stringers? I know when I riped the engine bear/ stringer combo, out of my boat. There was a material under both. I never did I.D. the stuff. but it appeared to be harder than ( although the same color ) the polyester resin that was infused in the chopped mat crap sprayed on them.

I did notice that there was little or no bond with the wood used for the bearers or stringers. There also seemed to be no need for filler material, for the stringers and bearers were both beveled to match the shape of the hull. So I never found it's real reason for being there.

 

stuff is called "Hull and Deck",,,it almost has fibers in it,,,like that "cat hair" crap. is the only thing we where recommended to use then glass over.,,everything else they tell ya NOT to glass over because it will cause cracks,,(they're right hehe)

 

P.S. ,,,how much "filler" are we talking about?,,,there shouldnt be much anyways,,,,,BIG reason for using foam as stringers,,,it can be shaped QUICKLY.
isnt hard to use a sheet rock scraper,,,,and ya need filler to make radiuses,,,put the foam down,,get it shaped,,,glue it there,,,,then go around and "fill" ya corners to make them easy to glass,,,then glass over,,,,,done.,,,well,,,,maybe,,hehe