Core decisions on 43 DCMY

[Triskele]

Walt, styrene binder in mat should not be a problem with epoxy. It was a problem with polyester resins and only below the waterline (I presume you are referring to gassing which led to blisters). Since I consider the deck to be a structural element due to the loads from the windlass I used cloth and biaxial fiberglass coated in cabosil. Maybe overkill, but as I said can drive a tank over it. I think I used 10oz cloth and 17 oz biaxial layered between each layer of plywood. Under the top layer of deck glass, I made a batch of thickened epoxy with cabosil and smeared it on the bottom surface of the deck glass. I then rolled in my wetted glass. Once the glass became tacky and started setting up, I put in a wetted layer (glass side) of 1/4" marine plywood and braced it into place. Let it dry and set up for 3 or 4 days depending on my time. Once this is in you can come back in and start the next layers when you have time, but probably no sooner than three days to insure a good solid bond.

BTW...I have loads of pictures I can share, I just can't figure out how to add them to this site. I think I have reached the limit. If you want to PM me with your email address I can send you a few.

[Triskele]

Thanks, i was wondering how the plywood for coring worked for you. I already have my windlass removed (Good automatic) and the bow pulpit. The coring under the teak insets was bad so it is in my workshop ready to be fixed and painted. I have been testing adhesion with PVC material and have good results. Im going to put this in the pulpit for coring becuase its rot proof. I will be over sizing the holes in the foredeck and filling also to prefent warer intrusion. I didnt think this was going to be fun so thanks for the tip on rolling the glass onto pvc pipe. Is West epoxy and slow hardener the way to go as it sounds like time is also an enemy here.

Thanks
Walt Hoover

I used resin from the Epoxy Store in California. I liked it for this application because it was slow to set especially if add 5 to 10% acetone. Also, most epoxies wet out easier and set time regards when mixed with acetone. Can't speak so much for West Systems. The advantages are that you only have to mix out small batches and use what you need, thus less waste, but found it was sometimes harder to work with cause set up faster. The key is to get the stuff out of the pot and onto the glass. Longer it sits in the pot quicker it will start to cook. Trust me you'll have a few hockey puck batches, but that's how you learn. Acetone goes a long way towards controlling this. The other drawback is West is expensive. I have had luck with U.S. Composite and Raka on other projects (repairing hull blisters).

[oscarvan]

I have used this outfit for epoxy in the past.... personal service and decent prices....

http://www.raka.com/epoxy.html

[whoover]

Thanks for the offer Oscar but I think I have a handle on it for now. Since I'm here in the great white north my supplies will be found locally. I have a pretty good local fiberglass supply store nearby and a place called Canada Composites located near the Toronto airport that supplies the aircraft repair industry.

Walt Hoover

[oscarvan]

Ah, didn't realize you were on the other side of the line. Yeah, that can get complicated.

[34Hatt]

Walt, styrene binder in mat should not be a problem with epoxy. It was a problem with polyester resins and only below the waterline (I presume you are referring to gassing which led to blisters). .

The problem is with Mat and Styrene epoxy doesnt break it down which makes it a PITA to wet out and why use it if using Epoxy? Matt is used in polyester resin as the binder aka the stick between different materials suchs as matt first then roven these days everyone uses biaxial stronger and easier to wet out. So then with Biaxial it comes as 1208 or 1708 and the 08 is the amount of mat added in with out styrene so it works with both materials and applies very nice in comparison to the old days old using roven and mat.
Some 1208 and cloth with epoxy and you can fix 95% of everything

My personal like is to use 1208 instead of 1708 and just use a extra layer you may think its more work but its easier due to the fact of it wetting out and conforming easier. It also then is stronger

[whoover]

Thanks for the description of the material. I have been all over the web and could not find any kind of chart with materials and weights of them. After doing price checking I am going to use West epoxy as it is only 50.00 a gallon more than other epoxies. So the plan now is to use 1208 material under the top skin then a layer of marine plywood. Let it cure then repeat until I reach the core thickness which I think is 3/4". This weekend is clean up the cut out area, make a paper pattern of the area and measure up for a stool in the locker to work on.

thanks
Walt Hoover

[jim rosenthal]

Are you set on marine plywood? Coosa board might be better. It is great in this application.

[Cricket]

Yeh, I'm not understanding the use of plywood either, to me it's just a harder version of balsa that will have the same outcome if water gets in.
I would go with Coosa, appropriate thickness so you only have to install 1 layer.
Run it through the table saw if it needs to be scored to be able to bend for the deck crown.


Regarding biax 1208 and 1708 cloth, with epoxy we use 1200 and 1700 which doesn't have the layer of mat.
Just think it's much easier to work with.

It's not like I don't like plywood, have a 32' custom Carolina center console built out of Okume, Meranti with fir stringers all wrapped in epoxy and biax glass.

[whoover]

The plywood is at the suggestion of Scott. The size of the area is such that it will have to be in three sections to fit through the locker door and the joints staggered like bricks on the next layer. All of the edges will be sealed and all of the new mounting holes will be over bored and willed with epoxy. The repair will be kept dry so it should be stronger than the original balsa core and much stronger than what I removed.

Walt Hoover