need help with plans

I've seen the material. I inspected a vessel around 8 years ago for a friend (polyester based ferralite) and it had problems. The boat ( A 50 foot sailboat) was just about given away. It had blistered and there were pockets of acidic fluid in contact with the steel core it was eventually sorted and fibreglassed over and is still around. The material I saw on that boat absorbed moisture and hydrolised. I can't get enthused about marine materials that do that.

Metals are only easily bent permanently if you exceed the yield strength. You can design accordingly. Steel boats (as opposed to ships) are not prone to being holed to the extent that it's almost completely unheard of.

Material properties are the absolutes here, nothing magic happens when you form a hull out of a certain material. We design structures around material properties, it's an applied science called engineering.

So some really simple and hopefully eye opening questions for you to ask. What is the SHEAR strength of the material you are advocating? And what is it's STIFFNESS. These are very simple but important material properties.

I'd be interested to know. If the supplier can't tell you then run a mile.

 

Hey Mike- here is a comparison of concrete and the fer-a-lite, notice the bending strength. and this is WITHOUT reinforcement--that point alone sells me not to mention the stuff can be trowelled on by one guy over a period of weeks if necessary.... a coat of epoxy should keep it from soaking up water...


FER-A-LITE DATA

PHYSICAL PROPERTIES COMPARISON

(without wire reinforcing)

Portland Cement------------------------------------------------- FER-A-LITE

bending strength (Modulus of Rupture) 700 psi ------------------ 3600 plus psi



Compression strength 5-10,000 psi ----------------------------------8000 psi



Weight lbs per cu. ft. 144 --------------------------------------------------60

 

Standard plaster with no reinforcing vs ferralight with high tensile steel reinforcing ,mmmmm that's really useful and honest.
There's a lot more to materials than they have given you there:!:

Unfortunately that’s cherry picking numbers that have little real meaning on their own. Do they have a proper material properties data sheet?

You really need to know the stiffness of the material AKA Youngs Modulus(E). For both tension and compression. (You will also find being a plastic that the properties vary with temperature).

You should be provided with the shear strength as well. They are both important properties.

Also consider how it gets on with the mesh will depend on the bond strength to bare steel and the thermal expansion coefficient.

Material properties for elastic materials should also be given for a % change in dimensions and this is used as a practical yield figure.

Finally barrier coats don't stop moisture ingress they just slow it.

 

Hi Mike - I dont think this material is absorbent...ill check, i have a sample coming but concrete is actually tried and proven too. I'm not saying your wrong--i just cant see epoxy allowing moisture or water to penetrate the hull? On a true FC hull- concrete absorbs so little..and then a barrier coat of epoxy literally seals it up...Ive seen quite a few FC boat hulls -ive seen them opened up too but never saw moisture probs unless the work was shoddy...but ill keep it in mind for sure...

 

Another interesting number is the tension properties, (I'm a little unsure of the right word here...) I mean the clean tension/ pull, the material can take in a clean pull, straight out..

That will determine the 0-axis, the cross section where the material will collapse about. Of course, you'll have a steel cage, reinforcement that will help, but salt sea is an unforgiving place, it may not always be there....

Epoxy and correct use of electricity may be enough to give the steel a long and lasting life, but then again... You may only need a neighbour in the boatyard that screws that up...

 

tugboat,

Do a bit of homework on resale values of non "standard" boats......it may just open your eyes.....building a boat from a non standard material immediately limits the saleability (and sometimes sailability too) to certain individuals that have generally no idea of what they are buying....most purchasers listen to other boatbuilders or surveyors and realise that one day the vessel will be sold, limiting the amount of potential purchasers from the start of build is not real smart mate.

 

HI landlubber- appreciate the input--i suppose i should have stated this some time ago since your point has been metioned a few times about resale---

the bottom line for me about resale: I don't really give a crap...i build my boat to enjoy it. i am building it for me -not to turn a profit--if i get ten years out of it and get what i put into it--thats a-ok for me...

cheers

 

tugboat,

I understand, that is your choice, but it would be nice to at least get back what you put in. Unfortunately i am a boatbuilder, I do not see any reason at all why you should build a boat and then loose money on it (but i am very aware that this happens many times)... to each his own, at least you have listened to others opinions and decided to do what you consider best for you.

 

It will absorb moisture it's the nature of the material. Barrier coats work with some materials becasue the water molecules pass through at a greater rate than they pass the barrier. Some materials such as polyester actually 'hold' the water molecules until they are saturated.
FC with pozolanic additive is very impervious to water, more so than polyester. Other materials like wood are quite happy with a certain moisture level. Some materials hydrolise ( water actually breaks the material down) and unfortuantely polyester is in this arena. The side product is acidic which is the opposite to the alkaline conditions that passivate steel.

 

Mike--if this was such a bad product -i.e using polyester resin--no one would have fiberglass boats at all...

and fer-a-lite boats wouldnt have last 30 + years---for info-checkl out the fer-a-lite thread..theres some good info on there--and lots of naysayers..
however im not disregarding what your saying, ill look into it further...

cheers

 

In the port of Hamburg was a FC hulk afloat for more than half a century. Never finished, so, never sailed a mile, but afloat. Finally broke into pieces, just so.

What did that prove?

One can say, the material is very durable.
--yes of course, when not sailed or otherwise stressed, and in fresh water.

One can say it is very weak, when it breaks without any damage from impacts or thelike.
--yes of course, that should not happen, but, hey, it was never finished and never maintained.

And one can say, it proves nothing. There are far older steel boats / hulks around, and they did cross the seas, and did not rust away. But many younger steel boats are long gone.

You see?
Your preconception and stubbornness must just be strong enough, to see only what you want to see, and it is the truth, at least for you!

As I said, go for it, make your own experience, and be happy with it!
Who cares......................

 

"Who cares......................"

...you do you poor bugger, just try to let it go mate, you can lead a horse to water, you cannot make it drink......it is a worry eh. I feel sorry too for what some people do, but we have to respect them for their own decisions if that is what they wish to do, c'est la vie.

 

Very quickly, looking at the test figures Fer a light has an almost identical modulus of rupture to standard ferro cement which is around 62MPa (9000 psi).

Wood is a similar ( some types are better) performer. Steel is around 5 times stronger to yield and 6 1/2 times stronger to rupture.

 

You're missing the point. Engineering data has no relevance in the light of revealed truth. Ask any member of a religious sect.

BTW other than bloody heavy (1.2g/cm3 in my reference book) how does iron bark stack up? Grey iron bark if it matters. They built all the old Sydney wool stores from that stuff, beams 300 x 300 x 9m or longer.

I've been fighting the good fight with a sheet of steel on the bottom of the hull. Its recalcitrance is yielding to brute force and a good technique I picked up from Murielle's web site. The next one should be quicker as I know what to expect (suuuuuure.....)

PDW

 

Peter
Strength to weight wood is hard to beat without going to carbon fibre. Even then wood can have an edge in some areas.

The Eucalypts like steel are great for heavy displacment craft and some like Ironbark are tremendously strong where stresses run in the main fibre direction. But tools blunt very quickly working with those woods so they are hard to laminate.