Can you build a boat?

I would recommend going to your local bookstore like barnes and noble or borders, and purchasing a book bout fabricating with fiberglass.

http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?z=y&EAN=9781892216168&itm=4

Hi Ashman.

I have built some fiberglass boats a lot of time ago. Digging a hole (negative mold) implies that all the defects in the mold surface will be transferred to the end product.

Depending on the final quality you are searching for, you can use this alternative or doing it as Pro´s do, which is more time consuming and far more expensive...

Pro´s make a Positive mold (ie: inverted hull) using very thin plywood nailed to a frame or (much cheaper and faster) Styrofoam. Once the definitive shape is achieved, you will have to work on it to leave the surface defect free, spray a release agent on it, to get a negative mold in fiberglass.

Defects of inner surface of this mold have to be corrected, after that a release agent is applied to it, the external paint of the hull (here we call it Yelco) is applied to the mold and on top of that you will have to apply layers of wowen fiberglass + fiberglass mat + polyurethane resin.

Problem is that fiber glass is itchy, resin is dirty and polluting, smell of resin can be unbearable...

What about building a steel hull? It´s much faster, cheaper and affordable!

Do not forget to check local regulations from the maritime authority, as usually a lot of paperwork has to be done to get an construction approval!

Good look in this project!

AShman wrote: I am sure there is a way to build a hull of a, lets say a 60' er' If one was to dig a hole that would be the negative

REPLY: if you are from Oakville go down to Port Credit harbor and check out how many DIY boat hulls are under construction at any given time. You are not likely to find much at Oakville Yacht club.

Save yourself some time and trouble and buy one that is for sale. Many DIY project run out of steam and $$$ so the owner sells to whomever wants to pick up the pieces.

Elnav

I think the best thing that all of you guys with apparently too much time at a design desk can do, and I think that your guys in the machine shop that your sending incomplete drawings to will agree is..... 1) Find a job where your not so bored as to send rediculous responces to questions as such, 2) Find a job where you can afford to invest in something other than a repoduction of Tom Sawyers pile of bullshit he took down the Mississippi and 3) get off the crack. Even if you could layup a boat hull in your back yard....Do you really think your wife actually likes the fact everyone with any common sence contiually laughs not only at you but at your entier family. Please stop thing so much, let the pro's do what they do best. Boat building is an art, just like building a feeder bowl...go throw one of those in to your 3d Stress Anaylis modules. Oh by the way I am a degreed mechanical engineer, I have done machine design for a long time. I have also built some dumb shit then I think one day I just got it that in life there are things that you should leave to someone that does it for aliving.

Actually, it was Huck Finn who took a raft down the Mississippi, not Tom Sawyer. So not only are you profane, you're illiterate as well. And they hired you why?

I've built boats in wood and fiberglass. Wood is more fun.

Aye lad, ye could build a boat that way. Just like you could dig the Panama Canal with a tacking hammer and a teaspoon. I'd nay reccommend you do either.

I really enjoy this forum. Some great stuff some not so great. However, Mr Degreed Mechanical Engineer with a foul mouth (guest??), why not back off.

Us poor mortals all learn something from almost anything. Try opening your mind a little, rather than the more visible holes in your oversized head

I agree! This guy may be a millionaire soon. By trying to learn how to do something without formal education(on this subject), he could think of a new way to do things.

Its always nice to hear both sides of a different question!

The only "off the wall" part of this idea is the hole in the ground(inaccesible, too much work, fills with water, etc.). An interesting method of construction is to pretend to design a steel hull, laying out the planar sheets you will need to build a well designed hull with no compound curves. Then convert this plan to available marine plywood and backup any none angular edges with plywood strips and glue, Drill and stitch angular edges with SS wire, Fiberglass all joints inside and out and you've got an empty marine plywood hull to work with. Take it from there!

Just putting it out there.If hull media was able to cure at below freezing temperatures,could a mold be fabricated with ice?

Out of ice? Sure, why not? I don't know about the chemical reactions to cross link the polymers, but if you could get the material to kick then ice would work and getting the hull out of the mold would be rather simple!

A few questions:

The fiberglass mat is supported/strengthened with a resin. Does the catalyst that is used to cure the resin have to be in a warmer environment to work? I used to work in a fiberglass shop, and the curing process would produce a lot of heat; would this affect the ice mold before the resin cured, and change the shape of the mold before the hull was solid? The resin will have a tendency to slump even after you think it has cured, so to retain the shape of the mold the project must sit on the mold for an extended period of time. Brilliant to think of ice as a medium for a mold! Most of the projects I've spoiled occurred when I separated the project from the mold.

Have a great day!

If dirt is your prefered work medium, why not use a mound instead of a hole. If the soil is clay you could even wet and smooth it. It would be easier to release, and could not fill with water.

No matter the way you finally decide to build the hull, you should know that most of these projects finish un concluded: pieces and bits spread all around your backyard, plus a lot of money invested in all kind of useless materials.

Given the case you manage to finish the hull, at this point is where the BIG problem starts: you have to build the interiors of the boat, to do the equipping, and the rigging... you need to have really deep pockets with plenty of money inside, cause banks do not support such projects.

I don´t want to discourage you but, as I have sailed all kind of boats for the last 40 years: the best advise I can give you is to use the money you have for this project in the purchase of the best boat you can afford now. Once you´ve got it: go out sailing, and enjoy it a lot.

In the meantime, save more money and go for an upgrade!

Plan B is to buy a boat that needs restoration (there are thousands of them dumped at most club´s shipyards): if you are handy, you will able to duplicate the money you originally invested in it.

This is probably the best advise. Unless you just have to DIY or want something that's simply unavailable go out and buy a well equiped slightly used boat. Save yourself a bunch of cash and time that way....

There is a method of building a boat hull using fiberglass (as a glue mainly) and wood (plywood) without a mold!

I believe it is called Cold Molded double-diagonal construction.....but the results are in one of the strongest and lightest hulls that you can imagine!! Without building a form of any sort and with minimal finishing at the end....

Wikipedia mentions it....

Actually, the fiberglass is not used as a glue, epoxy is. These boats are often covered in fiberglass cloth (saturated in epoxy), to provide abrasion resistance. Such boats, if very carefully built, can be varnished, with the fiberglass begin transparent when embeded in clear epoxy.

Cold molding is not for the faint of heart. Cold molding can produce some beautiful, strong, light boats. Often the strips used are thickish veneers (1 - 3mm x 100mm wide or so) rather than plywood, but thin Okume ply (3mm or 4mm, and cut into strips 100mm wide) works well too. In either case, you end up with a plywood boat with smooth compound curves. The WEST (Wood Epoxy Saturation Technique) system is the most famous for this type of construction, and it leaves the wood pretty thoroughly encapsulated in epoxy (although not really completely saturated).

Even thin plies don't really compound perfectly (any more than you can wrap strips of paper around a ball without wrinkles), so there are often lots of edges to be sanded away in the final layer (and even in early layers). The frames used to lay the plies against are actually called "molds" and they have to be fairly close together. Typically, there are many stringers holding these together and giving the boat its shape before laminating begins. It's all rather time consuming, but gratifying.

The same is true for strip construction, in which the strips are much narrower, but thicker, and applied lengthwise, side-by-side. Custom canoes and kayaks are made this way, and it produces a beautiful boat that is also quite light. Prior to sanding and fairing, the cross-section of a strip built boat is really a polygon... you make it rounded by planing and sanding. The fact a strip-built canoe can be $12,000 or so (as opposed to $600 for a manufactured boat) gives a sense for the labor required.

An easier method is stitch-and-glue (which ordinarily is also epoxy and/or fiberglass covered). Large plywood panels are used, making construction must faster. Such construction is usually hard-chined, but these hulls can be very nice looking too -- many wood kayaks are made this way.

Any of these wood construction methods will yield a boat that is very durable, and significantly lighter than a typical fiberglass production boat. I have a stitch-and-glue pirogue that I take through class 1-3 rapids, occasionally banging into rocks (and routinely scraping over them), and it holds up just fine.

In small boats, and even in large, building your own can be a way to get a nice boat inexpensively. My pirogue cost me next to nothing to build. A large boat can be a major undertaking, though, generally taking much longer than building your own house by yourself. If I hired someone to build a duplicate of the Windrocket (seen in my little picture) it would cost $50,000... far more than a production boat of the same size (it's only 250 lb).

Ken you are completely correct, my memory is not as good as I hoped!!

It produces probably the strongest hull to weight of all the methods I have seen....

It other good points are if I remember correctly that the epoxy stops seawater penetration to a great degree after local damage and with care, the hull can be made as good as new again!

Ken, other than the fact it is time consuming (and therefore costly if you have to pay the hourly rates!) and mainly for home made boats because of that, are there any other negative aspects that should be considered?

Very few negative aspects. Few things are better for the soul than building a wooden boat. Some people develop a sensitivity to (uncured or partially cured) epoxy, but if you always wear gloves, and avoid breathing in sanding dust, it's very unlikely. Most epoxies are nearly odorless, making them much more pleasant to work with than polyester resins (which can't even come close in resisting water or adhesive effectiveness.)

Why dig yourself in a hole? Why not consider ferro-cemento? The Italian engineer Pier Luigi Nervi built a 400T ship and a cruising ketch in 1942/48.

A St. Lawrence Cement plant is in Mississauga....they might contribute to the project while you would have lots of fun with the structural analysis!

Cheers

I do realise that some successful boats have been built with ferro-concrete, at least its not much worse than steel, but if I ever built me a boat, it would have to be as light and as strong as possible. Even if the time to build was longer.....

I had a friend in the UK about 30 years ago who built a ferro boat in his back yard. His first problem was turning it to be the right side up, he was lucky nobody got killed. He then finished it off over about 2 years.

The next problem was getting the finished hull out of his back garden onto a trailer, it cost him a fortune because he had to hire the biggest drivable crane in the UK at the time, to lift it over his house!

Sheer weight was the problem......he did not even know himself how much it weighed!!! The crane company told him he was crazy........he had some heavy insurance to pay as well....

Also, if I accidentally ran it onto some rocks or even sand with surf, I would want a strong light boat (actually I would want a strong light boat at all times when sailing!). I cannot believe that concrete would handle that as well as a properly built light boat (that might even sail over a lot of obstructions!)

It is a bit like aircraft, heavy and they need more fuel as their displacement is greater or longer masts and bigger sails if a sailing boat. Heavy aircraft (in proportion to their size) have never been good.

Either way, I would prefer that sails be as manageable as possible and of course, they would be cheaper if smaller....as would masts.....and engines.....and fuel.....

During WWII, due to steel shortage a lot of ferro-concrete barges were built in Argentina to transport freight along the rivers. They lasted only 1/10 of what a steel hull lasts. Many sank due to poor impact resistance. The rest are half sunken at the margins of many rivers. Nobody wants to remove them cause it is very expensive, and nothing is to be recovered.

From what I know of ferro-cement construction it's not the best way for an amatuer. The construction requires a good analysis of the structure and the placement of reinforcing materials as well as the thickness of the cement. With the amatuer hulls I've seen you often get an overbuilt, very heavy structure that is better suited to be a barge.

I suppose with the new fiber reinforcing materials cement might be a good choice for a skilled builder, but I'd stick with epoxy and wood, if you'll pardon the pun.

Boat building - regardless of what material - requires very exacting measurements and control of the hull shape. the original query about the feasibility of using a hole in the ground as a form ignores all of these requirements. It also ignores the very real problem of being a rain collector and the lack of shape stability you get with such a hole in the ground. The measures required to properly control these issues will be as great if not greater than using conventional techniques. Just ask any house builder about foundation work.

Which is why I suggested the person go visit a neighbouring port where some DIY boat building projects can be seen.

I have seen friends home build boats in every material including cement, steel, GRP, wood, and epoxy saturated wood, and strip planking. I have worked in boat building yards and am currently employed in a naval achitect office as a designer. I have seen the result of what happens when a hull mold warps. Despite being used by a professional shop s**t happens on occasion. The results can be expensive to fix. I think the original questioner needs to do some additional homework before choosing a particular construction method.

True, the better the tolerances the better the boat, but I'm sure you've been amazed by what people will put up with. Or, as they say, ignorance is bliss.

Still, I think I've found the right combination for the hole-in-the-ground mold idea. This would be a great method for ferrocement construction. Then, when you discover you can't get the concrete out of the hole, at least you have a swimming pool!

...Love the answer ca1ic0cat.

Maybe his wife wants a boat and he wants a swimming pool!

He can build the boat and rename it when the hull is finished....Won't Wifey be pleased?.

You're right, ferro-cement is definitely not the right choice for an amateur. Granted, it's possible (and common) to make boats out of materials far more dense than water... but why pick one with so many things going against it? Almost non-existent tensile strength, no toughness, unpleasant to look at, unpleasant to work with, horribly heavy. I can't imagine ever really feeling safe in a boat that can crack, nor would I want a boat that (for a sailboat) would have such a low ballast to displacement ratio. Suppose you want to bolt something to the hull -- it's easy as pie with most other materials.

Concrete is a pretty good material for things that don't move. It makes no more sense to build a boat out of concrete than to build a car or truck out of concrete -- sure you could drive a concrete car -- but who on earth would ever want to?? Fortunately, the method is virtually never used by amateurs anymore, but even when it was being used occasionally, I always wondered, why anyone would want to work with such a material, when wood is so pleasant to work with, and so naturally suited to something made to move and float.

Having said that, there is a concrete canoe competition among colleges, and the resulting canoes (using very light concrete -- foamed or filled with micro-balloons) are about 80 lbs. That's not light, but not a lot heavier than an old aluminum model. It's a vaguely interesting academic challenge -- although developing new materials (foamed aluminum core with integral alu skins, for example) and methods (fast molding of carbon fiber with optimally oriented strands and core materials that could be quickly molded to shape) would be more productive, I'd think. I'd have to say that taking a material badly suited to the task, and building an overweight canoe out of it would only be half as fun as building a really cool 25 lb canoe, while advancing the state of the art in materials.

Ken, well said. I was being as well mannered as I could, but concrete boats of any sort are just what you said, "an academic exercise", not a serious method for normal usage. I did not want to upset anyone, but all you said was completely true.

Your concrete car illustrated this point very well....I think that a concrete plane would illustrate it also!!

I think it was the great Arthur Piver who said that even conventional hulls, that need to bolt huge wights on the bottom of them, just to stay upright, are completely stupid in design and he was not even talking about F-C construction!

All items in a boat should be to make it stable and to help it float, which is why Piver boats could be half full of water and still float, or even upside down and still float......whereas conventional hulls sink very quickly in such conditions.

He was also someone who advised never to overload any boat, an important point, still often forgotten! He likened boats to aircraft in this respect, he was right!

I personally would say that the Arthur Piver designs are today a little outmoded, but the principles still apply even today. Sadly Arthur is long gone, but the newer construction methods applied to updated Piver deisns would probably result in a very good boat.

I hope we put him off the Blog owner from using the ferro-concrete method of building a boat......!

Andy Germany wrote: I hope we put him off the Blog owner from using the ferro-concrete method of building a boat......!

I don't think the original questioner was thinking of cement but rather fiberglass. Resin is now becoming so expensive that most builders are using cored FRP hulls usin gvarious formulations for the foam in the middle.

The hole in the ground idea doesn't satisfy several prime criteria for hull construction. However as to the problem if how to get the hull out of the ground, that's easy! Use the dirt scooped out to build up a wall around the hole. Line the whole with poly. When the hull is done, fill the hole outside the formed hull with water. If the hull is in fact done correctly, it will float upwards. Properly done the bottom of the hull wil float up close to the original grade. To give it a little more boost, dump in some dirt under the hull but into the water to fil the bottom of the hole unde the hull and incidentally rais the water higher. Once the hull is floated high enough, use a tractor or dozer to push the wall of dirt back into the hole under the boat. End result is a hull sitting almost on top and at near original grade. At that point you simply shore up the hull and complete the construction. The hull should be floated out of the ground before the engines and interior is installed. The light hull will float higher than a finished hull.

Elnav

The foams are not just there to save money on fiberglassing components, they actually improve the strength, the stiffness and provide important heat insulation to stop condensation on the inside of the hull.

Sadly if a boat gets a hole, they suck up seawater......that is why the epoxy resin wood construction is so good, you get almost no seawater in the wood, it is waterproof, also,the physical strength, stiffness of such a hull is weight for weight much better. insulation can be sprayed on easily...on the inside of course!