Steel-made hull with fiberglass-made radius chine ?

Steel did work for you, that is for sure ! Are you telling me that this was the fist time you built something with steel ? I am impressed ! If I had had your talent I would never considered attaching some odd plastic bandage on the surface of my hull ! I wish you were living in a mild climate like me, or else build indoors, you would have finished and been sailing by now ! Congratulations my friend, I wish the best for your beautiful craft and your nice family. Thank you very much. Please continue to post your work in photos. Many people like me would like to follow the progress and enjoy the birth of this new child of yours.

P.S. I was talking about pipes having the radius of the round turn of the bilge. Even you can not bananize them...

 

xarax

Yes its my first boat i build but id say that im a deasent fabricator. So its not the first time im holding a mig torch in my hands. But its not what i do for a living.

Again and i think anyone that have handson experiance agrees. Its not the radius section thats hard. Most chalenging for me when it comes to hands on welding have been transverse but joints on hull, topsides and deck on flattish areas.

For me its not the wether that makes up the time of building. Im making parts at home in my garage during cold and rainy days. For me its the inflow of money that decides if and when i may get more steel or tools. Me and my wife both work full 40h/week and spending qualitytime time with our daughter. or "entertaining" mother inlaw (80+ years) so no mather if we'd been indoors or warmer climat we'd wouldnt have ben able to build any faster.

-- Per Larsson

 

What bothers be is not the difficulty of welding and fairing the seams of ONE radiused plate, but of the MANY needed for a visually perfect outcome. It seems that, at some places at the turn of the bilge amidships or at the bow, one need to cut, weld and fair as many narrow steel plates as practically possible, every two, or even one, transverse frames. Wynand s perfect hulls are made this way obviously, not to mention the sequent excessive torturing, hammering, grinding and finishing...So you need MANY weldings and fairings, with an unknown outcome till you finish and paint the hull! It is the different angle that the light is reflected upon the finished painted hull that will finally spell the good or bad news, and this has to be postponed till the end of the whole effort! I would have been in a dangerous state of anxiety during all this looooong time period...
If one tries to build a frameless, origami-type hull (as I would like to...), these difficulties would naturally be more, not less. The ideal incarnation of the method would be a hull with transverse seams only between plates laying on the same developable surface, (if you can t avoid getting rid of them altogether by using monolithic long steel plates from the bow to the stern...) Two plastic fairings on top of the chines at the two more round areas of the turn of the bilge didn’t t sound to me such a really bad idea. (That is BEFORE I dared to publish it on this forum... )

 

Light displacement metal hulls would be much easier to construct with the "attached plastic radius chine" method I am thinking about than heavy displacement ones, because the total area of the hull which is to be covered with the plastic "banana" fairings needs to be a very small percentage of the hull s surface. As the boat s displacement becomes lighter, the hull becomes flater through most of it s surface area, so it can be built mostly out of simple curvature developable surfaces, so the plastic fairings that are needed to convert a multichine hull to a radius chine one are reduced in volume. See for example the second and fifth photo at the site of Guy Ribadeau s Shark 50.2 hull: Wouldn t it be tempting to think that one could replace the covering of the small remaining area with two long plastic fairings?
http://www.ribadeau.com/naval/www/index.php?module=articles&action=showart&article=111

 

Xarax

If i would have been very anxious about the radius I’d use a English wheel forming the plates to perfect shape rather than making molds and bolt on grp parts to the hull and thus escaping from future problems.

Now im not that anxious by nature and accepting that my radius aren’t 100% perfect but I can cope with it and besides a very big percentage of it is under water while at rest. The decision will be up to you. If I was to buy a hull/boat I’d run away from a steel hull constructed like that. Remember any metal hull end up with dings and suppressions after a while. If that’s not up to it then id suggest a all grp hull.

But i personally really appreciate when people dare to think outside of the box and upon that dare to stand up and fight for his/her idea! Then you dont need any approval.

-- Per Larsson

 

Actually not... what happens is that steel plating (or sections of tube) , when cut or welded very rarely end up developable.

If you take a flat sheet and cut a piece out of it, this piece will not remain flat but have a double curvature in it. This is caused by the heat-shrinking of the material all along the cut, the border gets shorter than the original circumference. The same happens when you oxy-cut a tube lengthwise, the cut border will shrink and your tube will indeed be bending like a banana towards the open, cut side, and it will have a double curvature.

Another way to get a flat sheet to show a double curve is to bend and twist at the same time. Many boats have lines like that near the forefoot and are often difficult to plate because of this.

This deformation of the originally planar sheet can be quite strong and is often undesirable in classic hardchine construction. Some designs use this as a "feature", letting the sheet get a bit of a "cheek" while tacking them on on first around the border, and then move the stringers out against the sheet to adapt to what is really a double curvature.

And regardless of hard-chine, round chine or radius chine: this happens on ALL parts of your plating, because all of them are welded all around.... So in any case, even the most developable hardchine hull, if you would cut the sheets off along the chines after it's built (silly idea of course ) would never fall apart into really flat panels again, each of them would should double curvature... So the trick is to make use of this behaviour of the material to produce the roundes possible shape with minimal fairing.

As nicely demonstrated by Wynand, radius chine is one way to do that. I remember also a boat that was built by a sort of diagonal strip-planking with long, twisted diagonal strips of sheet metal, and the result was very very fair and very round. Folded orgami hulls also show some double curvature in the ends.

So, I think there are enough methods to arrive at a "round" look and still keep it simple while retaining all the advantages of an all-metal hull.

 

Thank you Yago, very informative as always!

But how on earth or sea could one calculate the amount of double curvature thus induced into the plates in advance ? How you know that, after you cut this or that plate and weld them, they will fit on your frames without any additional torture and hammering? And even before this stage, how you can calculate the width of this or that plate that is needed to have this or that desired double curvature?
Now, the amateur steel boat builder gradually learns that there are too many tricks, many secrets that have, somehow, to be revealed to him by learning, practice, try and error, or even pure luck, before he masters the art. But by the time he does unveil the sacred book, either the hull is finished, loaded with all the mistakes, and then probably abandoned and left to rust somewhere.... or our amateur builder himself would be rusted, bodily and mentaly, because he has spent a significant portion of his remaining life span in vein, and can not now pick a toothpick, not an anchor...
But to return to the point, I was talking about the whole double curvature that the turn of the bilge has, that of course is an order of magnitude greater than the one induced as a, desired or not , by-product of the temperature deformation of plate s borders during cutting or welding. I have said that one can not have these two areas formed in the desired shape by starting with a developable simple curvature surface made of steel, meaning that a one or multi-piece quasi -cylindrical or quasi-conical steel surface would need hard and excessive work to be fairly rounded. But if this surface is made of some flexible plastic material, one could possibly form a mould and then cast a GRP part out of it this and then the part can be attached to the steel hull, effectively converting a multi chine hull into a radius chine one.
The task is not to have an all-metal hull; the task is to have a hull that floats nicely into the sea and sight. If we can achieve that by this method or by any other method, a significant obstacle to amateur steel boat construction would have been lifted.

 

I would of course not pretend to be able to calculate that in advance it is simply that fair radius chine hulls, origame and even round chine hulls have benn built, for real, by amateurs, and that this is possible.

For me, there does not seem to be the need to start a hunt for the "flexible plastic material" that would allow you to get a double curvature (only along the chine!) and still be as strong as the steel right next to it and then to have to solve the technical issues of having to join two different materials. I really can not see how this could be nicer, stronger, simpler and easier than to build a radius chine.

...but then, who knows, maybe you've got something there, please do suprise us

 

Stronger, no, of course not, but you don t really need to be strong if you fasten yourself tightly to a steel hull. And if the plastic bananas decide to detach themselves from this engagement, you can always fill or drill some holes on them and use them as water tanks or flower pots on deck...
Simpler, may be, for an amateur that has not mastered the art of hammering or hasn t ate his breakfast ...
Easier, yes, if you order and buy the plastic parts from the local fibreglass boat builder, as I plan to do...
Nicer, of course, if you compare the result that you may achieve with the ugly waves that you would have generated trying to handle the hills and valleys of this strange environment, the surface of the steel plate.
( I still remember the horror I felt when I tried to weld a bolt to a curved steel pipe of a rocker chair I had designed : the circular curve was turned into a helicoid, i.e. a true space wave....)

 

xarax, I would not know about rocker chairs, but on the half a dozen steel boats that I built myself and the dozens of steel boats I have seen built over the years around me, all by amateurs, there's never been any hammering of plates whatsoever.

As for the "hills and valleys of this strange environment" and other deformations, they typically appear in the flatter, straighter, open areas which you would also have above and below the chine, or on the deck, most often built from thinner plating. The often mentioned hungry horse look appears in the same areas, and is usually caused by the plates welded (tacked) to vertical frames rather than onto floating horizontal stringers... but all of that has nothing to do with the type of chine construction, so if you replace the chine with a perfectly shaped piece of plastic, you have NOT solved the problem of controlling the welding-deformation. The chine (round or radius) is usually NOT a problem area.

I think you imagine the entire process much more complicated than it actually is, and don't want to believe what people with practical hands on experience try to explain...

so, I guess there is only one thing left to do: show us!

 

Thank you Yago,

I really do like people that want to stay young and fresh forever, so they still imagine themselves accordingly...A person that has built half a dozen steel boats is, unfortunately, not an amateur any more! He is probably not very young any more, as a steel boat, build by an amateur, takes years to complete, and this multiplication takes years out of our lives, but of course he can stay very fresh for many more years... Imagine how I feel as I am not young any more, AND I am still an amateur... But I have to say that I am probably the one and only real amateur in this forum! That is, a person who hasn t build a steel boat, (not yet...), and who probably will never build a steel boat, either because he will never be able to finish it or because he will abandon it to rust somewhere as the outcome wouldn t probably look like what he had imagined at all. This is the, sad but true, fate of amateur boat builders from which one seldom escapes, so why do I have to be naive enough to expect that I will? But an amateur steel boat builder loves steel boats, and, I have to point out, most of the times much more than an ex-amateur does, because amateur s love is still fresh, full if imagination , the seams of which are not yet hammered by reality s hard impact, not grinded by time ...Now, I repeat what I have said before to Wynand, and applies to you as well my dear friend: "professionals usually underestimate the difficulties amateurs confront in their first steps creating something . They tend to forget how difficult it was even for them", when they were still amateurs. Because amateur you are, not only when you still don t make any profit from your work and labelled professional, but when you still love your work with the freshness of a novice, when you still inhabit the imagination s realm mainly, not reality s, with all the good and the bad sides of this stage...
That said about the merits or sins of the imagination stage, and as I admire very much what people "with practical hands on experience try to explain" and I always believe in experimental science only, lets return to reality:

I ask you a couple of questions : What is the minimum thickness of steel plates above which one has not to worry about thermal deformations of the plates on a 60 feet frameless hull , deformations visible with naked eye that usually distinguish the men from the boys, the work of amateurs like me from professionals like you? The developable surfaces of such a hull are flattish enough, so will they bend at their ends after cutting and welding and so will they need excessive grinding to be faired? You tell me that if you avoid the contact of the plates with the transverse frames, or if you have no transverse frames whatever as in the case of a frameless origami-type hull, you do not have to worry about the nasty games light often plays with the surface of amateur built steel hulls? Because if one has valleys and hills on the most visible parts of his boat as you say, and if one is condemned to have a keen eye and is able to see these deformations every day, he will try to sell his boat even before it hits the water...

It is the combination of more work that is absorbed there during the construction process with the more dangers that the more seams pose to the final visible outcome that frightens me, for one...Although the whole thing can well be nothing more than a figment of my imagination...

 

I am not a professional, but a amateur builder, although not for the first time ;-) and most of the boats I saw being built were built by first time amateurs. That means: without heavy tooling, and usually welded by non-professional welders.

plate thickness: that depends on the shape and curvature of the hull, but with care you can keep 3mm fair, 4 mm is easy. On my current build, the hull is 3 mm and fair, but the deck is 2 mm and that is NOT easy

But there is no practical minumum thinkness as such that will guarantee deformation free hulls, as you ask, it all depends...

Framing: what structure you have in your boat depends on the designers specs and scantling. He may specify any combination of framing (traverse and / or longitudinal) and plating.

Personally I would avoid having traverse framing directly on the plating as this tends to break the curve, and would prefer "floating" longitudinals carried on traverse frames.

 

How to do this

OK, if your really want to build this thing- this is how to do it.
Make your pieces out of regular resin and fiberglass. Finish the outside are as wanted. This thing has to be strong, have bracing inside like mini-stringer. The pounding of wave will crack if not built tough.

Make sure it fits perfectly against hull and make sure make brace to hold it against hull firmly. Grind off all paint of area where this thing goes. Bare metal. I would grind in a few rough spots in metal to make sure epoxy has something to grab.

You can weld some tabs on hull with a galvanized bolt to attach this thing. Don't drill a hole in hull. I dont think it is necessary if Epoxy holds then you don't need bolt. If Epoxy doesn't hold the bolt is not going to do much.

Fiberglass inside area should also be rough.. Once it looks like everything mates perfectly and only then. Apply a coating of epoxy light coat to metal area and interior surface of part. Wait a 4 hours

Apply epoxy heavy coat to part. Wait a couple hours or until heavy coat is a little less runny. Press parts together and brace them together carefully and with equal pressure. Remove excess and use epoxy to fair around it. Cross your fingers. Let it set for 48 hours


Light Epoxy - 2 part resin, 50/50 + colored Talc. I use talc used in chalk line dispensers to give a little color so I can see what I am doing. Almost like a watery paint consistency, You are using this like primer and a bond

Heavy Epoxy - 2 part resin, 50/50 + colored Talc + at least as much talc as resin by volume. Like a Peanut Butter consistency, You are using this as your glue and filler for gaps

Always mix epoxy first, then color, then talc. I use 5 gallon pail and big drill mixer.

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This will work - I dont know for how long may be 3 years. I would check it every year. I have done this on Aluminum boats for steps. Worked until owner hit rock with step.

If it sounds like a lot of work, it is. Preparation of parts, metal and epoxy are key. If you screw up, you have big mess. Working with epoxy at this level requires practice and knowledge.

I cant help more without a diagram with size and pictures.

 

after over 20 years building in metal, dont advise radious, build a proper, round hull, i,M WILLING TO TALK TO ANYONE, privately, and for free, on any aspect, take a look my gallery

 

"thermal deformations of the plates on a 60 feet frameless"

Danger,Will Robinson, The only 60 feet frameless hull of anything I would go in would have to be piloted by Jesus Christ Personally. A frameless boat would have to be to heavy to be of any use to have the basic strengths of a thinner hull with a basic skeleton.

Sometimes the amateurs smartest decision is to hire a professional. By the way, I am a amateur with 30 years experience. I don't think I could make a profit building boats. I do it for fun.