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Old 10-07-2016, 17:13   #1
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Construction Acronyms

HI can some one please shed light on all the different construction types?
When I am perusing the classifieds I am presented with all kinds of construction types some of which are self explanatory others are unknown to me.
e.g
Fibreglass
GRP
Epoxy Core
Balsa
Composite
Carbon
Kevlar
duracore, (there seem to be a number of "dura" sub types)
etc, etc,
It would be helpful to know what the differing types are;
Any help gratefully appreciated.
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Old 10-07-2016, 17:28   #2
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Re: Construction Acronyms

GRP = Glass Reinforced Plastic - or fibreglass, composed of the glass fibre fabrics and a resin, also known as solid glass also known as FRP or Fibre reinforced plastic

Then there are cored build methods, where the core provides stiffness and strength and is lighter than an all fibreglass matting and resin boat. Some of the cores are Ply, Western Red Cedar (WRC), Balsa, Foam, and the Duracore/Duflex cores which are a manufactured balso block panel. There are also some other slightly off beat cores like Nidacore which is poly propylene honeycomb. The core should theoretically never see the world, the core is coved in a fabric eg Fibreglass mat or Carbon or kevlar, and then the resin binds this altogether.

There are three main types of resin, Epoxy (the strongest most osmosis resistant and most expensive) Vinylester (very good and strongly osmotic resistant) and polyester, cheap and average, least osmotic resistance.

Strictly speaking all boats other than metal ones and very old plank timber are composite, composite just means "made up of several elements".

Simplistically speaking you start with a core, lay a form of stiffening fabric (glass/kevlar/carbon) and form it all into a unitary structure with a resin (Poly Vinyl Epoxy) .

Wrc boats are strips of timber glued together to form the structure and usually covered with a layer of glass mat and then an epoxy to make the mat structural and adhere it to the timber.

There is a reasonable article here Boat Building Methodsthat summarises it.
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Old 10-07-2016, 17:46   #3
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Re: Construction Acronyms

Hi Factor thanks for the prompt reply. I did know some of that stuff but there definitely seems to be some confusion amongst brokers as to what the different abbreviations are. I actually saw a Snell advertised as GRP when I rang and queried it they said glass reinforced ply!
Anyway thanks again, it will certainly help with figuring out what's what.

What in your opinion is the best construction for a medium sized cruising cat?
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Old 10-07-2016, 20:28   #4
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Re: Construction Acronyms

You are right there are many ways of building boats and the people in the know use acronyms.
Apart form metal and ferro boat construction there is:

Wood
Planked, carvel type
Planked, clinker type
Plywood, with or without a fibreglass/epoxy sheating (as protection for the ply)

Glass Reinforced Plastics (GRP) or Fibreglass Reinforced Plastics (FRP), are generic terms for fibreglass boats. Sometime one sees the “P” (for plastics) referred to as “Polymers”, in fact that is really a better name. Such material has two building ingredients:
- Fibres
- Resins (with additives and hardener)
As far as resin concerns these are the main types but each type will have hundreds of subtypes/brands etc
- Ortho (phthalic) resin, this should not be used for under water use, think blisters
- Iso (phthalic) resin, better than above for marine use
- Vinyl-ester, best of the polyester resin types, no blisters and much stronger
- Epoxy resin
As far as fibres:
- Most common is fibreglass (chopped mat, woven, cloth, Bi axial, tri axial, E glass, S glass and much much more
- Kevlar fibres, very uncommon, and then only used sparingly to help market the boat, OK just a bit cynical here.
- Carbon fibres, the bees knees for owners with deep pockets

Then are there hulls (and decks) that made are out of composite materials. Composite meaning made out of different materials. Often such hulls/decks are said to be cored: ie an outer layer of FRP, then a core, and then again a layer of FRP (or any of the above materials). Such thick construction can be extremely strong and light at the same time.
The following is used as a core:
- Strip planking ie cedar, ie relatively easy for one offs, and home building
- Balsa
- Various kinds of foam
- Various kind of honeycomb material
- Many many other products
There are many brand names. When you know the product in the core, goto their website and find out the properties of such material.

Oops, noted that "Factor" already replied, well, now you have the info twice
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Old 10-07-2016, 21:00   #5
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Re: Construction Acronyms

Thanks Hankonthewater switch Factor very helpful and I greatly appreciate all the info!:
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Old 10-07-2016, 21:05   #6
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Re: Construction Acronyms

Quote:
Originally Posted by ghendoaus View Post
What in your opinion is the best construction for a medium sized cruising cat?
Depends!
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Old 10-07-2016, 21:56   #7
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Re: Construction Acronyms

In the matter of strip planked construction: In this technique, the WRC strip planking is not really similar to what most folks call "cored FRP" construction. In the latter, the core is not particularly strong on its own. It serves mainly to space the two FRP skins apart, which adds greatly to t he panel stiffness.

In the strip plank method, the timber strips, usually edge nailed and epoxy soaked, form a very strong hull on their own. The glass skins are usually only one thin layer applied to each side... more for protection of t he timber than for strength. On our boat, there is considerable extra glass in a few areas, ie the stem, the skeg support area, between keel and keelson and possibly a few more that the builder didn't tell me about!

This is rather different from blocks of balsa or strips of foam, often applied to the outer skin after it has been laid up in a mold.

Cheers,

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Old 10-07-2016, 22:20   #8
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Re: Construction Acronyms

Jim, you're right, that the strip-plank (in the middle) provides strength in its own right, unlike other core constructions. I listed all these together as being 'composite'.
At a contrast I listed also, "plywood with a fibreglass/epoxy sheating as protection".

So for the OP, a strip-plank boat is generally not considered to be a boat with a cored hull, just known as a strip-planked hull.

Most strip-plank boats I have seen the glass/resin skin were 3 to 6 layers of fibreglass. Really strong! BTW, on a used boat it is very hard to figure out how thick the glass skins are unless you find a bolt/skinfitting going through, a bolt/fitting that can be taken out and that area has not been reinforced in any way.

Addit: another term used at times for a cored hull is: sandwich construction.
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Old 10-07-2016, 22:46   #9
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Re: Construction Acronyms

Quote:
Originally Posted by ghendoaus View Post
Hi Factor thanks for the prompt reply. I did know some of that stuff but there definitely seems to be some confusion amongst brokers as to what the different abbreviations are. I actually saw a Snell advertised as GRP when I rang and queried it they said glass reinforced ply!
Anyway thanks again, it will certainly help with figuring out what's what.

What in your opinion is the best construction for a medium sized cruising cat?
There is no one best method. Nomex/carbon prepeg that's autoclaved will build the stiffest lightest platform possible, but will be god awfully expensive. For a cruiser it also buys more load carrying capacity.

Fiberglass over plywood is probably the cheapest, easiest, also pretty fast to build. The downside is they can rot, weigh a lot, are hard to get a lot of stiffness, etc...

Other methods (infusion, planked, hand lay, etc) are all somewhere in between. Different methods make more sense than others depending on the goals of the boat, the pockets of the owner, and the number of boats being built.
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