Any one used metal frames inside of glass boats !!

Strange question !!,but have had this concept put to me a couple of times in the last couple of years and a BIG BUT POPS UP !!
Personally i had wondred about the same thing MYSELF some time back .
ok fitting and glassing to the hull could be a problem to be sorted in finding a method that would work but its not impossible !!
Holes any shape !
Slots an shape !
Adhesives that are compatable to stick glass to Aluminium or galvanised steel even!!
Advantages ??? dont know but there could be some somewhere !!
Dis-advantages could be many and varied , who knows its worth a thought !! maybe

 

It is possible, there are many aircraft structures that use alloy frames with composite skins. Since the two materials act very differently under load and in response to temperature changes there are a few issues to consider in the detailed design.

First is that the interface between the two materials must be sealed with something to keep moisture out, and I would suspect that some kind of mechanical fastener would be desirable, as in counter sunk screws (installed wet with sealant) from the outside bolted through the skin into metal flange or a clip or angle. That is how it is done in aircraft.

Not sure I would trust the whole connection to an adhesive with two materials with such different properties.

Why do you want to do that? Wouldn't it be easier to go all metal or all composite?

 

Petros !! Thank you so much for imformation recieved so far . Me i am a person that will look at any possibilities of something new for boats ! The young designer i work with asked me a couple of weeks ago about this very subject so i to wanted to Know if it is feasable or not !!. Personally if you are building in glass then 100% everything else is glass for ever more in the construction . Everytime another material is added theres a problem of some sort so stay with one is much simpler !!
THANK YOU FOR THE INFO !!

 

Several yachts employ metal armatures or skeletal frame works internally, boned to or completely encased in laminate. It's not especially unusual, though not particularly common, as laminate is cheaper from a labor point of view. Since production craft are built to a price point, you don't see this approach much, but customs, semi-customs and racers employ it more often, with obvious advantages.

I think it's silly to marry yourself to a particular material in terms of a yacht. Increasingly so in recent decades, we're finding more and more need for composite structures, which do have to address the issues raised by Petros, but I don't think it's a limiting factor. Quite the contrary in fact. With the exploitation of stronger, stiffer materials, in the resin/fiber matrix, you can have stronger, lighter and more durable structures. If you want simple, great, but there's a lot more to the decisions regarding a particular yacht's design and preformance envelop, then how homogeneous you can keep the structure.

 

As with everything in design, it is cost and/or performance related.

You can design a structure anyway you like...you can make it out of Switz cheese if you like. But, the essential part is knowing where the failure modes are and what drives them. From that what mitigation is done to ensure a structure with longevity.

Once you have done that, so long as it satisfies the SOR, in terms of the performance (does it do what you say it will), of the finished product (whatever it may be) and the cost (is it in your budget), then Bob's you're uncle and Fanny's your aunt!

 

X-Yachts come to mind.

Dino

 

Steel frames/structures in a GRP boat can be problematic I think in extreme temperature changes like going from winter in Europe to the hot tropics due to the different coefficients of expansion of these materials.

When I built steel boats we actually measured boats in early morning (14C) outside and again midday (32C) and it stretched by 30mm on a 38ft boat

 

HI every one !
Thank you for all the interest shown so far .
The thing of exspansion really never crossed my mind but i now understand better it would be a major iissue in places with extreme hot and cold ! i am a die hard composits person and thats where i comfortable at . mixing materials has to many problems i dont want to think about !!

 

Before carbon Composite, metal glass composite was common 25 years ago with race boats. Kiwi Yachts in the US used the system . Many Swans.

As ADHOC stated... Why ? mix materials when modern materials can achieve the same result.

Metal glass has problems. This week I'm repairing a 20 year old Carbon glass boom. The boom has a alloy gooseneck embedded into the carbon glass laminate that is fatigued.

The surface prep when built was sandblasted aluminum , Alodine treatment then epoxy bond. The bonds are still solid but fractures in the alloy and elongated holes need repair. No way to get in and weld the metal components without over heating the laminate. I will have to cut the alloy out then rebuild the laminate. Messy expensive job. I would avoid using metal .

 

It's funny how the engineers haven't any problem with it, but the non-engineers can think of all sorts of excuses to not take advantage of the obvious benefits. Of course anyone can site examples of this and that on either side of the debate, but reality is that metals within laminates, aren't any more problematic than other materials. Each has a set of properties to engineer around, which isn't particularly difficult. I inspected a 50 year old galvanized steel armature and mast step grid, imbedded in a polyester (ortho) laminate from the factory, with no issues a few years ago. It could be done a half a century ago, it still can be. This assembly could have been done a lot lighter with modern materials and resins, but it would also have cost a lot more too.

 

I've successfully used stainless steel tube to reinforce an 8 ft wide radar stand. It replaced a similar construction with galvanized steel that suffered from corrosion and after 10 years looked like it had smallpox. There are holes drilled in the tubes for stainless fasteners that hold alloy tent rails; sea spray intruded there and caused the corrosion.

 

I know steel and as a qualified boilermaker worked 38 years with the stuff. Steel reacts swiftly to temperature changes by either shrinking or stretching. Join up a few lengths of pipe and secure to plinths and see how it pushes plinth over in heat or cold - that's why expansion joints get fitted. Another example, just take a 50mm x 6mm x 6m length of flat bar, place it early morning in the sun and secure both end and go back midday and see how it bend due to expansion.
Short runs of steel this expansion is not noticeable but when one goes into the numbers of boat length is sure is a factor. For example, on a refinery we measured a steam pipe cold (+ - 15C) 9120mm when installing it and at 110C it measured 9160mm! This is the very reason most pipes in this situation are hanging from spring hanger supports to compensate for movement. Note this minimum temp is not even close to cold / freezing situations that may exaggerate the expansion/shrinkage.
Steel building frames are design/engineered to compensate for expansion movement and thus safe.

To place a few small tubes in a little GRP radar arch for support is a silly example due to the pipe used relative short and just bolted on. Same for a steel frame in a hull - can move around. BUT, use steel within a laminate or hull laminated fast to steel frames and stringers, are a recipe for problems. If that steel decides to stretch or shrink, something will give...
Even when building steelboats I always fitted plates on the opposite sides of the hull at the same temperature to prevent the "banana" effect of hull. Much like welding only one side of hull which will have the same result - seen some steel boats done this way and the hull good for scrap. If a steel hull cannot handle such shrinkage, imagine what it will do with a tupperware boat?

BTW, I commissioned the Dix 38 in 1990 and in its original concept was designed to have a GRP deck on steel hull. Traditionally a steel deck takes longer than the hull to build and limited in shape and form. The reason of GRP was speed of manufacture, nice curves, shapes etc can be obtained such as GRP boats. Whilst first hull was under construction I experimented by doing the following;
I built a 10 x 1 meter angle iron frame, laminated a GRP sheet to laminate schedule, then Sikaflex and bolted (toe rail bolt pitch) the sheet to steel frame and left this outside in our hot summer days and cool nights. After a week it was examined and found many cracks in the GRP at bolt holes. Note that Sikaflex do flex for movement and in some little way the bolts can give way. Imagine what would have happened if the GRP was laminated over the steel frame to secure itself as sort of sandwich construction?
Needles to say the Dix 38 has a steel deck after that test piece.

Its not about not an engineer or an engineer, its about common sense and past experiences / results on a subject. Engineers are only as good as their hands-on experiences and many have never dirtied their hands.

 

I put 25 mm stainless tube along both the front and rear edge, not bolted but bent in the right shape and embedded in the laminate. The horizontal parts were cut in the middle and connected with a sleeve allowing some expansion. It also made them easier to make and put in place.

Stainless expands roughly twice as much as steel. Not a problem as long as you are aware of it.

 

You're so right. All the thousands of metal and reinforced plastics structures just must be worthless and dreamed up by inexperienced idiots, with no practical understanding. With all the aircraft falling from the sky and race boats breaking up, once the mid-day sun hits their armatures, it's a wonder they haven't passed a law to prevent these terrible mishaps. Again, the engineering isn't that difficult, nor particularly misunderstood (for many decades now), though the layperson may have philosophical issues with it for what ever rational, it's baseless and the 10's of thousands of composite structures employing very dissimilar materials, are easy testament to to the clear misunderstanding of the engineering by the public.

Case in point, a steel reinforced keel, appendage and possibly mast step(s) are encased in laminate. Unless you're parked over an active underwater volcano, drifting in and out of it's rising column of boiling water, the laminate will isolate the steel from major temperature differentials. The ambient water temperature will never let the steel temperature vary very much (less the volcano mooring thing). Heaven forbid we actually consider attaching lead to this steel, oh and for God's sake surround it or place it in intimate contact with laminate. The electrolysis alone would make it blow up in a few years wouldn't it?

 

Steel and aluminium is just an example !! bulding composite boats has its what you can do and cannot dos as well , i am in total support of what ever you start with is what you carry on with ! all glass and all the same resin people trying to mix carbon and kevlar and glass are asking for problems , Carbon skins on glass boats and kevlar to the other extreme !
Computer analysing and spread sheets by the box load and still we have problems , as mentioned before its knowing the materials you are working with and how to use them and how they lay and the hands on feel of things!. I have in recent timed had a foot in both camps and spent time pouring over plans and drawings and listening to all the office drival and bull crap!, then i shut the door and change hats and roll up my sleeves and its into it . Making things is where the satisfation is , mixing resins ,the smell and feel . I can look at drawings and read laminates for that item and in an instantly see if its going to work or not .
The laminate stack also is another place no one questions and even fewer people really understand .
Can have 10 layers of glass with 4 differant types of glass matts spread throught the schedual and anyone looking woulds shake there heads but unless you have seen the plans and understand the stresses and strains and the whys and where fores its like trying to understand poetry in Chinese writting !! its meaningless !!.
The understanding of things is a personal !! some of us got it and most of us dont ,and those that dont got it usually never will get it ,but the few that do are a treasure !!!
Thank you gental men and i appreciate all your contributions in this thread ,one and all !!


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