Glen-L.com

hi ,im using system 3 general and i put 3 layers of it on a small piece of ply with 6 oz fiberglass.i let it cure for 5 days and did a toughness test with a rock,it dented quite easy and with a harder wack went all the way to the fiberglass. are there other epoxys out there that are tougher >harder im mean wanted to use white cedar for my deck and if i used this stuff it would look terrible pretty quick thank you

Resin is only a coating for sealing a surface or to work in conjunction with a fabric to wet that fabric out. Impact resistance is entirely a different animal. Glancing blows and direct blows with a foriegn source such as your rock and how much damage an impact will create depends on several factors. But for the sake of your experiment the core dictates how much dinging takes place. The key is does the laminate seperate in the deflection process which also depends on the quality of your bond in most cases if the glass did not puncture


There are additives for resins that increases its toughness such as graphite or aluminum fibers for glancing blows such as we get when running aground though on pebbled areas. But these products does little to reduce the direct impact and how much damage is done to any and all areas in and around a region. There are associated factors that decides the amount of damage. [I know a lot of words]

thanks lots how many coats do you put on the hull i know most go with 3 ,but 5 cant hurt

I think you are misunderstanding the function of fiberglass over wood in your experiment. A 6oz cloth of fiberglass with 3 layers of epoxy is not applied for the sake of surface impact resistance, but rather for surface wear resistance. Those are two different things. In this case, the fiberglass overlay will add a layer of protection to the wood beneath it from some (not all) scrapes and friction-based wear like dragging over sand, gravel, etc.

I've designed fiberglass structural components and they can have some significant impact resistance, however they are MUCH thicker than 6oz cloth and 3 layers of epoxy. 0.1" thick or greater.. THEN you will see a significant impact resistance from fiberglass.

I would take your same rock test and try it against a thin sheet of steel or aluminum, and give it a good wack like before.. you will see and dent just as well and mark up the surface.

The reason I fiberglass my plywood is to help protect the thin veneer of wood from as much wear as possible, but its not going to save my boat from dents if I run it into a rock.

You have the optoin to add a thicker layer (or multiple layers) of fiberglass cloth.. which will require a lot more epoxy... and add some weight to the hull as well.

_________________
Ian (aka Iggy)
My Malahini Build

Actually thick layers of pure resin is not always the best. The key and general practice is to create a uniform layer of resin across your surface and then go with your alternative coatings. Of course this goes without saying that even an uneven face surface such as fir plywood can be smoothely coated and still not be optimum for shiny topcoats too. This is where you need to deal with fairing the actual core surfaces before you spend a lot of time and money for a lot of materials that should be sanded off to create a slick and continuous surface for your smoothe finish paints.

Hard surface resins are not the best choice for a boat because a boat is constantly flexing. The glass mat, weaves and carbon fiber products that are used provide lateral strength but do provide some increased level of impact resistance but not much. To increase impact resistance to the levels that I beleive your wish to achieve you'll need to use Kevlar cloth/mat/weave with an appropriate filler to provide either flexibility or stiffness.

West Systems line of epoxies and resins are what I've used in the past with excellent results.

_________________
Steve Schefer
Santa Rosa, Ca.

New Years Resoluiton - Never leave something for someone else to do when I should be doing it myself.

This info might be helpful, it is for the West System...click on the "Testing for Damage Tolerance" on the left hand side!


http://www.epoxyworks.com/31/index.html

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Patrick Morais
~ Lo Voltage ~
Ottawa, Ontario, Canada

thanks for the info,i think ill DBL my 6oz