does extra resin make repair weak?

Joined
Dec 9, 2006
Messages
51
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finnished bulkhead on trophy used a little over two gallons resin and 45-55 square ft. of 3/4 oz. mat made a mix of resin & cloth fiber (cat hair) put it on hull then squished bulkhead down into it before glassing in. while applying multiple layers of matt & resin some areas pooled see pics also some resin ran down bildge will this cause me any problems?
ready to install
4-1/2in deep runs 6-7 ft in bildge
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sbklf

Petty Officer 2nd Class
Joined
Oct 26, 2006
Messages
190
Re: does extra resin make repair weak?

Just enough resin to wet the cloth is strongest. The strength is in the cloth or mat not the resin alone. Resin rich repairs are weak and will crack and break. It might not matter in your situation. I would grind the pooled areas down if another layer of cloth needs to be applied.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: does extra resin make repair weak?

Dana, a bit of extra resin makes the repair stronger. More than that, doesn't affect the strength to any great extent. Extra resin also makes the repair resistant to wear, which is important on a floor or keel. The pictures you supplied show a good amount of resin. I wouldn't change it.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: does extra resin make repair weak?

Resin adds no real strength, it's the glass fibers that do the work and a resin rich layup will not be as strong as one at the correct ratio ( 33 to 40% glass, for hand laminating and 50 to 70% for infusion, or other types of closed molding).

If you were just trying to seal the wood and add a little strength, then a resin rich layup is sort of OK, but resin is brittle, so if it gets stressed or flexes, it may crack much easier.

3/4 oz mat is thin stuff, so you would need 4 + layers to build any strength and it's best to use roving along with it, roving is where you will get most of the strength.
 
Joined
Dec 9, 2006
Messages
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Re: does extra resin make repair weak?

thanks again i figure what i did had to be better than the way it was im getting the hang of it
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: does extra resin make repair weak?

Resin is Styrene monomer. The catalyst MEK Peroxide causes it to polymerize and form polystyrene. This is a relatively clear brittle plastic. In the old days, they used to make those very breakable kids toys from it. At any rate, just as thin glass fibers are more flexible than a pane of glass, thin layers of resin are more flexible than thick layers, so you want a thin layer coating the glass fibers and gluing them together. For maximum strength and flexibility there is an optimum resin to glass ratio. Boat manufacturers know what it is, I don't.
 

mike176

Petty Officer 1st Class
Joined
Feb 18, 2007
Messages
202
Re: does extra resin make repair weak?

the wood is where the real stringth is. I might be wrong but i would think the glass and resin is kinda like the super glue that holds it together and it acts as the sealer to keep the wood from rotting. I would not be worryed at all from those pictures.
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: does extra resin make repair weak?

Kinda of true but not really. Glass is the main structural component.

Take a transom or stringers for instance. While you may think all the strength is in the wood core of the transom or stringers, most of it is in the fiberglass skin. That's why you should use strong glass when repairing high load areas. The wood good simply restores and helps to retain the shape of the glass, ie. the wood core keeps the glass from deforming after/during flexing.

That's why it is extremely importantly, when replacing a transom, to inspect the integrity of the transom skin before installing a new wood core. Most need to be beefed up with a layer or two of biax and also most corners need to be rounded.

Transom repairs I've done for boats with 115+hp engines usually have 1-2 layers of glass wood core, glass, wood core, then 3-4 layers of biaxial glass with a finish layer of 1.5 oz mat to rebuild the inner skin. Mat has very little strength, so woven roven is what you want to use for laminate thickness and strength. But even better, biaxial glasses (like 1708 and 1808) trump woven when it comes to strength.
 
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