Flybridge Re-Core

[Boatsb]

I just finished helping a friend build stringers out of coosa. I dont think theres a chance they will soak up a bunch of water and fail. Ive also used airex, Baltec, divinci cell and the aforementioned nidacore. All are far better than rotted wood and each has its benefiits and downsides.

FYI a well done balsa core that is not pierced is as strong as anything else Ive used and lighter to boot.

 

[34Hatt]

Guys, we are mixing apples and oranges, perhaps other stuff too here.

Osmosis as used relative to boats describes a couple of chemical phenomenon that causes resins and laminates to deteriorate. There is a lot of good (and bad) information to be had on this subject.

Water intrusion into cores causes wood rot and debonding of the wood core. Intrusion into a debonded foam core will worsen after freezes so even there it is to be avoided.

Water absorption is not the same thing. Most plastics and resins will absorb water, especially nylon and epoxies. I have not looked, but would bet a beer that Coosa and other such foams will too, but as Jim said, not very much. And they will not rot. Some friable foams might start to deteriorate if very wet, but these and not what you will be using for a core.

Bobk

So why does everyone spend thousands of $$$$$ to seal the bottom of their boat with epoxy
Coosa will not allow enough water into it to have freezing be a factor something like Nida core with the voids could but you have to do a shitty job for it to be a factor and if that is the case then all bets are off.

 

[34Hatt]

I just finished helping a friend build stringers out of coosa. I dont think theres a chance they will soak up a bunch of water and fail. Ive also used airex, Baltec, divinci cell and the aforementioned nidacore. All are far better than rotted wood and each has its benefiits and downsides.

FYI a well done balsa core that is not pierced is as strong as anything else Ive used and lighter to boot.

Balsa is one of the best and stronger than most of them and for the money best bang for the buck if done right like you said all you have to do is oversize every hole fill with epoxy then redrill the center out just did all the stuff on my bow during the re-paint.

 

[Boatsb]

Dan it's not the epoxy in fact the epoxy is also semipermiable. The micro plates create the barrier for the water resistant coatings.

Closed cell foams will not absorb water but will take on some moisture. It's like a cigar in a hunidor.

 

[34Hatt]

Dan it's not the epoxy in fact the epoxy is also semipermiable. The micro plates create the barrier for the water resistant coatings.

Closed cell foams will not absorb water but will take on some moisture. It's like a cigar in a hunidor.

Yes I know about thats why west system has a additive but by itself its still better than the fiberglass and polyester that the boat was originally made with! Also you never see a polyester based barrier there is a reason for that.
So my point is don't go get all technical and split hairs when it all is better than original

 

[Boatsb]

The balsa lasted 30 years or more. The Coosa probably will only last 50.

 

[bobk]

So why does everyone spend thousands of $$$$$ to seal the bottom of their boat with epoxy
Coosa will not allow enough water into it to have freezing be a factor something like Nida core with the voids could but you have to do a shitty job for it to be a factor and if that is the case then all bets are off.

I used epoxy paint (1001/1002) to seal my trawler before it was launched when I bought it new about month after it arrived from Taiwan. The damned thing was loaded with blisters after a few years. As a plastics chemist I had serious reservations about using epoxy, but it was the rage. Epoxies absorb and transmit water. Water absorption factors are typically about 6%. Granted, mineral additives are included in the formulation to provide a 'tortuous' path to reduce diffusion transmission rates, but that is just a matter of rates, i.e. how fast it happens.

Years later after letting the blisters ripen, I had the bottom peeled and I rebuilt it myself with vinyl ester which is what the yards on the bay used if they were going to warranty their work. I sold the boat about 15 years after doing the bottom job. It had been to Florida for 6 years and in the water most winters before that. At the time of survey, it had just a few blisters.

A literature search at the time I did the bottom job revealed many other boaters had the same issue with the epoxy paint. Oh, BTW vinyl ester has about 1.4% water absorption if my old memory still serves.

The freezing issue came up when I was working on composite structures for aircraft surfaces. The concern was moisture in the epoxy resin would diffuse into the core and become liquid water and after repeated flight cycles freeze at high altitudes. I moved on to other areas of research before the first non-flight critical components were made from composites and have not followed the issues since then.


Coosa, BTW is a high density foam available in several densities.

Bobk

 

[34Hatt]

I used epoxy paint (1001/1002) to seal my trawler before it was launched when I bought it new about month after it arrived from Taiwan. The damned thing was loaded with blisters after a few years. As a plastics chemist I had serious reservations about using epoxy, but it was the rage. Epoxies absorb and transmit water. Water absorption factors are typically about 6%. Granted, mineral additives are included in the formulation to provide a 'tortuous' path to reduce diffusion transmission rates, but that is just a matter of rates, i.e. how fast it happens.

Years later after letting the blisters ripen, I had the bottom peeled and I rebuilt it myself with vinyl ester which is what the yards on the bay used if they were going to warranty their work. I sold the boat about 15 years after doing the bottom job. It had been to Florida for 6 years and in the water most winters before that. At the time of survey, it had just a few blisters.

A literature search at the time I did the bottom job revealed many other boaters had the same issue with the epoxy paint. Oh, BTW vinyl ester has about 1.4% water absorption if my old memory still serves.

The freezing issue came up when I was working on composite structures for aircraft surfaces. The concern was moisture in the epoxy resin would diffuse into the core and become liquid water and after repeated flight cycles freeze at high altitudes. I moved on to other areas of research before the first non-flight critical components were made from composites and have not followed the issues since then.


Coosa, BTW is a high density foam available in several densities.

Bobk

So you used Epoxy paint and using freezing at high altitudes and you said we were talking about apples and oranges LOL

Marine use Coosa Blue water 26 usually is the one Like the sample I have on the desk next to me because I do use all these products. Anyone that looks into using Coosa will see that so we generally don't spell it out unless they ask.

 

[spartonboat1]

Re: Flybridge Re-Core/ Coosa Notes

I've been away from the coring project, due to other matters. My contacts at a Coosa distributor, Total Plastics, in Grand Rapids, MI (plus many other locations), indicated that price is about $225/sheet of Bluewater 26, the "best" Coosa board. Many may cringe at the price, but I do not, as I plan to "go in" to do the repairs once and never return; 40 years of projects in industry and IT says, going back in is very time consuming and expensive. Best to do it "once".

The bending modulus (of a 1/2" thick panel), specific gravity, water resistance and willingness to adhere to West System and make a good material, IMHO. Coosa HQ says it is supposed to be a close comparison to marine plywood physically. I believe it should have the physical characteristics needed. The Specific Gravity is 50% higher than Balsa, i.e., Balsa is up to 16#'s/cu ft, whereas heaviest Coosa (Blue26) is 27#'s/cut ft.

If I install 2.5 Coosa 4'x8'x1"sheets (actually 5 1/2" thick sheets), this is about 6.75 Cu Ft of Coosa at 26#'s cu ft=175#'s
Balsa comes in at from 8 to 16#'s cu ft, so the weight range of Balsa would be from 54 to 108#'s

The penalty of Coosa over Balsa for my case is 67.5 to 121.5#'s. In a 34k# vessel, I am not sure the top-hamper takes that much of a hit. I have been on a 45 deg roll, one time only, in 12-15' seas when they were trying to broach me, and she did not seem unstable, even at that; she did not snap back, but came back up to vertical steadily. I have read that Hargrave did not like the Flybridges on the 43' MYs, because it was more weight up top than he liked. Guess I am adding a bit more!

The FAQ site for Coosa is:
http://coosacomposites.com/technical-data/faqs

 

[spartonboat1]

Pictures of what I pulled off today, but I won't have more of the deck, until later.

I pulled the pilot's chair (heavy bugger!) and vacuumed off the sheet I cut off.

Chair is ratty, but I will re-finish her with 1990 Hatt paint.

 

[spartonboat1]

Re: Flybridge Re-Core/ Sheet with Hole

Pictures of the sheet of fiberglas pulled off with a hole about 2" dia. Ok, the hole covered a solid stub of epoxy resin and there are two of them behind the bridge chair. Any know what they are for? I have no clue. The rope is so I can lower it away.

 

[spartonboat1]

Couple more panel pics after removed and vacuumed off.

 

[spartonboat1]

Pics with what good wood there was, i.e., not much.

 

[spartonboat1]

Last pics tonight, under the cap's chair.

 

[spartonboat1]

Chair holes.

 

[oscarvan]

Yup, it was time.

 

[Mel Tucker]

Just had Washington Yacht Service (Washington, NC) do the same job on my 1976 43 DC. They used 1/2 inch high density carbon core foam (from Paxton Supply, Wilmington, NC). Pictures attached ( I hope). Mel Tucker

 

[Mel Tucker]

Another picture. Finished. Mel

 

[SEVEN]

Start to finish how long did it take? Cost? What did you replace the core with? Excellent job. If you ever come to California I have a job for you.

 

[Mel Tucker]

Took 40 hours and $2700.00 for job. Used Carbon Foam from Paxton Supply Wilmington NC. Mel