STEEL HULLS with Composite Superstructure / Topsides

paints are made for the areas they are used in.
Had to do a repair to a plastic composite ( French made, French 2 pak repair) I gave them the meteo details here in Singapore and they said wow you are the only place in the world where you will need to do it in a spray booth,
ok great!!

 

I contracted all the coating work to a couple of companies in Brisbane so honestly, have no idea what the equipment was they used. The sq/mt rate was reasonable so equipment efficiency was high.
We did have a ox/acet wire feed unit I used for small highly detailed work like drop pendants or wall sconce lights. For the big works - 100m plus heavy forged balustrade projects I sent out.
I can try contacting the companies if still around for info.

 

I experiment using the affinity of aluminium and epoxy to build a composite (rear engine GT roadster) light weight structure.
Problem that developed was the flexing movement kept braking the bond of glass wrap to aluminium frames so the structure was compromised. I think in a vessel the issue of flex is probably going to be much more critical & destructive to bonding.

 

The problem is most all of the 'resins' used with the FRP portion of boat building ar NOT flexible by their nature. If you did your project with polyester resins its even worst, and if you asked your laminating resin to perform the bonding job as well,.....there was your problem.

I'm not really asking the resin that would make up the composite part to bond to the metal skin of the hull. Rather I would seek out a speciality adhesive to accomplish the 'bonding'. To my best knowledge at this time that would involve either what they term a 'toughened epoxy'. a methacrylate adhesive, or some high-performance polyurethanes. These all possess a certain 'flexability' that will help mantain that bond. Some of them could be to flexabile for certain joints. So a choice has to be made.

 

A few years back I read about an english sports car with and all aluminum frame that had no welds or bolts in it. Everything was held together by adhesives. I believe it was a Lotus and the adhesives were made by a German company. Sports cars always want to flex and I've heard of no problems. I remember reading they were baked in ovens., the frames.

 

The method I used was 1st sand, 2nd acetone clean, 3rd epoxy thinners clean the aluminium then coat with epoxy bond layer before passivity layer activated. That provide the best bond surface for laminating the integrated FRP floor, inner guards and body substrate. The bond of epoxy FRP panels to epoxy pre coated alloy frames was very strong but just couldn't handle the flexing and torque.

I think if the space frame had been stiffer it could have been more successful, but not having a mega dollar corporate R&D budget I think we still did ok for small workshop project. I used the same system for several monolithic architectural forms we created for clients that as static structures worked very well.

 

Toughening Epoxy Adhesives to meet Today's Chlallenges

Just getting the surfaces super clean is not always the answer. There are LOTS of different epoxies, and many of them are brittle in nature. We likely need a 'tougher epoxy'...a more ductile one.
Look at the very opening paragraph of this paper...it summerizes it right up front.
http://uksaa-www.me.ic.ac.uk/mrs.v5.pdf

....just in case they take that weblink down, I've attached the PDF as well

 

Assuming you're only referring to deck framing, just what are you trying to achieve here? I know that's a simplistic question and maybe I've overlooked the answer, but honestly I don't get it.

Is it:

A reduction in labour?

A reduction in build time?

A reduction in material cost?

A reduction in the number of welded joints?

Any deck beam other than steel, on a steel hull, isn't going to be attached as simply and strongly as a welded joint, the beam isn't going to be as strong for the same sectional area.

So where is the gain?

Deck and cabin structures, OK, I understand the logic there. You've already been given the standard methods - a ring beam with waterway on the inside of the hull then a bolted/glued joint allowing for different expansion and contraction rates.

I pre-drilled all my deck beams before I welded up the hull (including deck) then bolted & glued timber strips to them to fit the deckhead lining. If you wanted to lay a non-metallic deck then a variant on this strikes me as the simplest way to go about it. I suppose if your deck material was thick enough and you had careful placement of the transverse & longitudinal bulkheads you might get away with very few transverse deck beams altogether but this is an engineering calculation outside my knowledge base.

All I know is, doing mine the way the designer specified was straightforward and fast.

PDW

 

HPR 25 Toughened Epoxy Resins

I had written directly to
Adhesives Technologies of NZ
http://www.adhesivetechnologies.co.nz/adrseries.html

I got a relpy from

 

Brian
I'm curious too in what you hope to gain from using GRP structural members ? Just what you are trying to achieve ?

Steel framing is simple with a steel hull and steel integral frame and deck beams are the lightest strongest solution you'll get. The problem with dissimilar materials is losing the simple end fixity acheived by welding the ends of structural members to those adjacent .
This reduces the 'bending moment' and member stress by a factor of 4 and for a distributed panel load to 1/8. GRP also has differing E modulus which will severely test any glue bond.
Also I looked t the data sheet for that epoxy and it's quite weak relative to the steel, also it's in the high stress part of the 'beam' the outer skin. I think if you try and use GRP as framing you will increase complexity and weight for a reduction in ultimate strength.

[edit add the following for clarity]
Epoxy Glue UTS 16 Mpa
Steel A36 UTS is around 500 MPa

 

Just might end up adopting some conventional methods, but with all of the great adhesives and non-metal, non-wood products out there these days, we need to consider new methods to employ the if it looks feasible.

I was hoping that more contributors would get a spark of an idea and post it. Sure there will aways be naysayers, but this is like a 'brain storming' sesson for new possibilities. Go ahead and list them, then we will take a closer look down the road as to whether they make sense or not. Don't start off from the negative point of view that something won't work without bring it up for conversation.

Optimistic, Brian

 

The only time I mix materials is in bulkheads where I may use an Al alloy bulkhead bolted to the steel transverese frame to save weight.

But all I can see are negatives to GRP in this application. I can't see any positives, was hoping you had some !

It will be heavier have a brittle failure mode, be prone to burning in a fire and relies on a glue bond that would be severely tested glueing two quite different material properties subject to high stress.
To get that glue bond with ( relative to a weld or a bolted connection ) weak glue you have to have a large face a box or an I beam to get the section modulus. Than SM is much more easily achieved with a simple L frame attached to the hull and its an order of magnitude tougher.

What do you think is wrong with steel framing might be a better question ?

 

So basically you want to revisit the entire 'state of the art' and see if there's a better way of doing things.

However, from my admittedly limited knowledge base, you haven't actually listed any new possibilities. All you've done is listed things that have already been done and found to be less optimal than other ways in use.

Seems to me that you want a steel hull but without any of the steel supporting structure that keep the plate thickness down.

Perhaps you might wish to revisit the origami steel boats thread?

So far your suggestions involve the use of dissimilar materials with dissimilar expansion/contraction rates held together by various compounds whose bonding strength is *substantially* less than a welded joint in steel. Now if I understand you properly you also want to look into using such materials for supporting the hull skin itself.

Why? It's not going to be simpler, it's not going to be cheaper, it's not going to be stronger and it sure as hell isn't going to be faster. All that and you *still* have the same potential rust trap issues along stringers as you do with a conventional welded hull structure.

I still don't understand what you're trying to achieve here.

PDW

 

We had a disaster on one project with Adhesive Technology chocfast product installing twin shaft struts on 4 boats. The containers were incorrectly labelled so mix ratio didn't match the product.

Chockfast poured into the struts boxes then almost boiled as it went off shrinking its mass and pulling everything out of alignment. Took two days to drill & chip out the resign for a second attempt.

My fault for telling worker don't guess always check the instructions.

 

Protruded I-beam Stringers, Bonded in (NO welding)

Okay lets drop back and just look at one type of framing component we might consider fabricating of an alternative material,...lets take the stringer component you brought up, ...the longitudinal stringer.

How many did you have in your boat?

I'm guessing I may utilize 6-10 in my 40-50 foot vessel design. Ordinarily in a metal pleasure boat of this size these these stringers would likely be flat strips of steel welded edgewise to the hull's inner skin surface. (On commercial or military vessels I'm betting they would call for these stringers to be fashioned from L or T-shaped bar for greater strength)

We then proceed to tack weld them into place along their whole length. Next we need to fully weld them along their whole length, and we need to to this in an alternating manner so as to not warp the hull plating. I image if these 'webs' are very thick in section they would require welding on both sides to get a proper fillet with the hull skin without overhanging voids that could not be properly cleaned, then primed, then epoxy coated for a lifetime of rust free performance. Or as Mike Johns has pointed out we might run a bead of special chalk down both sides of each stringer to insure a good waterproof joint.

....NOW....

Contrast these processes with what I might suggest. I'm thinking I can pick out a suitable I-Beam of protruded glass that could be glued down to the hull's skin in the same locations as those metal stringers. I'm guessing this I-Beam of protruded glass would not have to be much 'taller' than 1.5 times that of the steel flat beam stringer., as it now has an extra wide flange set apart from the hull skin to take additional loading. AND I also have a nice wide flange area at the bottom to adhesively bond to the hull's skin.

I'm going to take a wild guess that I can bond my I-Beam stringer into my steel hull in 90% -, maybe 80% less time than it takes me to weld in those metal stringers. And when I finish 'bonding' in the I-beams I have NO more construction time required to clean. and prime, and chalk them as I did with the welded metal ones.

Basically that is one heck of a savings in time when you take into account 6-10 stringers !!

So now you ask are the protruded glass beams strong enough?? I would suggest you look thru the world of protruded and extruded glass beams. I could also double the height of these I-beams if prudent, I could make their flanges beefer, and I could extrude them of glass-filled nylon. Have you ever had any experiences with glass-filled nylon? We used it in numerous cases to make small spherical balls that supported big tall rotating mast,...and a few other spots...extremely durable stuff considering the shock loads these mast balls endured !!

Now I guess you're next question involves 'adhesives' Who would ever consider using adhesives to put a boat together?? Well lets see I think a whole lot of cold-molded vessels have utilized adhesives to bond their internals in, a whole lot of high speed powerboats use adhesives to bond their 'grids in, numerous wooden vessels, and a lot of hi-tech ocean racing boats, and those hi-tech America's Cup catamarans that I am sure use no welding to hold themselves together. Welding is not the only solution, and it is not the fastest method.

It's a brand new world, and there are new paths to consider.