Coosa Board

[BigSmile]

Hi,
I'm looking for any feedback on Coosa Board. Does anyone have experience with it for deck coring, or for rebuilding hatches?

I'm talking to a yard that is using it to re-core decks.

Thanks for any help on my first thread.

[minaret]

Originally Posted by BigSmile

Hi,
I'm looking for any feedback on Coosa Board. Does anyone have experience with it for deck coring, or for rebuilding hatches?

I'm talking to a yard that is using it to re-core decks.

Thanks for any help on my first thread.

I've recored acres of deck with Coosa. It's the bee's knee's. Any specific questions?

[BigSmile]

I've just learned a new expression, "bees knees", fantastic!
Thanks for any guidance.

Questions -
Curves - The deck curves need to be re-made from scratch, meaning what's left on the underside of the deck doesn't contribute to what's needed for the final shape/roll-off to scuppers & across foredeck.
As you know, balsa square sheets form nicely to sailboat deck curves, whereas Coosa board is flat.
Any suggestions for remaking deck profile, and how are curves handled with the Coosa board?

Resins - Any that are better than others in the families of Polyesters & Vinylesters, and Epoxies for use with Coosa board?

Application Resins different on bottom layers under Coosa board versus layers over the top - meaning would you install it with say a vinylester underneath it, let cure, and apply epoxy layers on top of it.
Based on what I've learned from surveyors, and the boat's history (Old core had exposure while open, everything underneath should be well dried by now, but tendency would be to use vinylester versus epoxy on the bottom layer). Using a different resin on top was an idea tossed around, but gives me pause. Are there any material or other properties, that suggest this a bad idea?

Hull penetrations - Tradition of solid fiberglass core for hull penetration areas, like for bowsprit bracket bolts or windlasses, versus Coosa board. What is the recommended method for core in hull penetration areas in conjunction with the use of Coosa board, have it tie into an all glass core area, or go all Coosa?

[minaret]

Originally Posted by BigSmile

I've just learned a new expression, "bees knees", fantastic!
Thanks for any guidance.

Questions -
Curves - The deck curves need to be re-made from scratch, meaning what's left on the underside of the deck doesn't contribute to what's needed for the final shape/roll-off to scuppers & across foredeck.
As you know, balsa square sheets form nicely to sailboat deck curves, whereas Coosa board is flat.
Any suggestions for remaking deck profile, and how are curves handled with the Coosa board?


Coosa bends pretty easy, but of course it depends on core thickness. If it doesn't want to bend easily to your contour, kerf the back side longitudinally on a table saw. Bagging always the preferred method for all cores, but old school methods work OK too.






Resins - Any that are better than others in the families of Polyesters & Vinylesters, and Epoxies for use with Coosa board?





Argh, here we go again! Suffice it to say I suggest you stick with poly. Many others here will shortly show up to refute this!





Application Resins different on bottom layers under Coosa board versus layers over the top - meaning would you install it with say a vinylester underneath it, let cure, and apply epoxy layers on top of it.
Based on what I've learned from surveyors, and the boat's history (Old core had exposure while open, everything underneath should be well dried by now, but tendency would be to use vinylester versus epoxy on the bottom layer). Using a different resin on top was an idea tossed around, but gives me pause. Are there any material or other properties, that suggest this a bad idea?




Use CoreBond for bonding core to the lower skin, if possible. Use the BPO catalyst, if possible.







Hull penetrations - Tradition of solid fiberglass core for hull penetration areas, like for bowsprit bracket bolts or windlasses, versus Coosa board. What is the recommended method for core in hull penetration areas in conjunction with the use of Coosa board, have it tie into an all glass core area, or go all Coosa?

All Coosa is fine for above the waterline only. Deck anulus work is not necessary with Coosa. It is more akin to ply than a foam core. Just resin coat it to seal it. Bare Coosa has been tested after more than two years saltwater immersion at less than 1% absorption.

[BigSmile]

Originally Posted by minaret

All Coosa is fine for above the waterline only. Deck anulus work is not necessary with Coosa. It is more akin to ply than a foam core. Just resin coat it to seal it. Bare Coosa has been tested after more than two years saltwater immersion at less than 1% absorption.

How is it strength-wise? I'm thinking about anchor rode/windlasses, bowsprits.

Not that I'd intend it, but curious why not below the waterline?

"Use CoreBond for bonding core to the lower skin, if possible. Use the BPO catalyst, if possible."

Thanks, found this for Corebond:
http://scottbader-atc.com/pdf.aspx?t=1&id=864
Scott Bader ATC

"Coosa bends pretty easy, but of course it depends on core thickness. If it doesn't want to bend easily to your contour, kerf the back side longitudinally on a table saw."

Present proposal is 3/4" thickness


"...suggest you stick with poly..."

I gather there are newer polyesters with better properties than original construction. Any particular guidance here?

A layer of 1708 (biaxial w/matte) before Coosa board is believed desireable. Also, seems consistent with another thread just found, did I interpret that correctly?

Thank you very much! Awesome to have benefit of your expertise!

[minaret]

Originally Posted by BigSmile

How is it strength-wise? I'm thinking about anchor rode/windlasses, bowsprits.

Not that I'd intend it, but curious why not below the waterline?

"Use CoreBond for bonding core to the lower skin, if possible. Use the BPO catalyst, if possible."

Thanks, found this for Corebond:
http://scottbader-atc.com/pdf.aspx?t=1&id=864
Scott Bader ATC

"Coosa bends pretty easy, but of course it depends on core thickness. If it doesn't want to bend easily to your contour, kerf the back side longitudinally on a table saw."

Present proposal is 3/4" thickness


"...suggest you stick with poly..."

I gather there are newer polyesters with better properties than original construction. Any particular guidance here?

A layer of 1708 (biaxial w/matte) before Coosa board is believed desireable. Also, seems consistent with another thread just found, did I interpret that correctly?

Thank you very much! Awesome to have benefit of your expertise!

Strength wise, Bluewater 24 is comparable to marine ply. But it won't hold a tapped in fastener, so remember that.

It's fine to use below the waterline, but I'd suggest a solid block out for hull penetrations. Because I always do, no matter what the core material.


No way to know if kerfing will be required till you try to bend 3/4" to your deck camber.



Use isotropic poly resin, not ortho.



No glass on the inner skin inside, only core bond.




Good luck!

[BigSmile]

Just looked up found 26 lbs per cu.ft. for the "beefier" bluewater product, other is 20.

Isotropic poly resin, that was the name was searching for.

On the inner skin side, I don't think can get away without laying some inner skin first, given pre-existing skin, or rather lack of pre-existing skin in some areas, and treading on the surface that should not have happened in current condition. Is this a problem for following up with Coosa?

I feel confident this can all be made right, with a proper solution. Thanks for your time and effort to help get there.

[Lojanica]

Coosa!!! Great stuff. Minaret is telling you exactly how to get amazing results.

I can add only one thing and that is I glassed in rot proof wood where I needed to drive screws as that is the only downside it doesn't hold screws.

I usedyellow cedar and/ or aluminum stripswhen I needed a bolt/screw point. Worked great. Vacuum helps alot but not entirely necesssary. I used poly and it worked well.

[BigSmile]

Thanks for all the feedback

What did you use for the non-skid surfaces in your poly solution?

[minaret]

Originally Posted by Lojanica

Coosa!!! Great stuff. Minaret is telling you exactly how to get amazing results.

I can add only one thing and that is I glassed in rot proof wood where I needed to drive screws as that is the only downside it doesn't hold screws.

I usedyellow cedar and/ or aluminum stripswhen I needed a bolt/screw point. Worked great. Vacuum helps alot but not entirely necesssary. I used poly and it worked well.

Alu plate works good for this, but so does bronze. Without the potential for corrosion.

[BigSmile]

Originally Posted by minaret

Strength wise, Bluewater 24 is comparable to marine ply. But it won't hold a tapped in fastener, so remember that.

It's fine to use below the waterline, but I'd suggest a solid block out for hull penetrations. Because I always do, no matter what the core material.


No way to know if kerfing will be required till you try to bend 3/4" to your deck camber.



Use isotropic poly resin, not ortho.



No glass on the inner skin inside, only core bond.




Good luck!

Minaret,
Hope you are still available for some feedback. Thought had a plan for Coosa, but now yard has some time for me, they want to change to Divinycell. Expressed some concerns about curves. We discussed kerfing, and still concern with coosa... it coming apart versus dinvycell already kerfed. Curves don't seem enormous, foredeck is just like a Hans Christian.

Is there ever an issue with getting coosa to flex enough to get it in under the margins on the side deck?

Also, went to a plan for original construction thicknesses, so would not need as thick a coosa board. Original construction was ply...so was following guidance for coosa were ply previously. New recommendation came through yards affiliation with another party, think a former boat builder, maybe go fast boats, but don't have credentials. Also, yard said couldn't vacuum bag.

What considerations might I be missing here? Committed to the repair, but don't want to start half baked on a big ticket project.

Thanks for any guidance.

[minaret]

Originally Posted by BigSmile

Minaret,
Hope you are still available for some feedback. Thought had a plan for Coosa, but now yard has some time for me, they want to change to Divinycell. Expressed some concerns about curves. We discussed kerfing, and still concern with coosa... it coming apart versus dinvycell already kerfed. Curves don't seem enormous, foredeck is just like a Hans Christian.

Is there ever an issue with getting coosa to flex enough to get it in under the margins on the side deck?

Also, went to a plan for original construction thicknesses, so would not need as thick a coosa board. Original construction was ply...so was following guidance for coosa were ply previously. New recommendation came through yards affiliation with another party, think a former boat builder, maybe go fast boats, but don't have credentials. Also, yard said couldn't vacuum bag.

What considerations might I be missing here? Committed to the repair, but don't want to start half baked on a big ticket project.

Thanks for any guidance.

Yeah, I'm around, just got back from a month's cruise.


First concern I'd raise with yard-the Union 36 was designed with ply decks for a reason. They would have been a key portion of the structure of the deck on this boat. If they insist on replacing ply with foam core, they will need to really beef up the laminate schedule on both inner and outer skins to make up for the loss of strength and stiffness.

At this point, they are playing at yacht design, not repair. I try to stick to the original designers intent-occasionally they are just wrong, but for the most part they have done the math and can be relied upon. If you make major structural changes like this, then you too need to do the math. Also, it is not always easy or even possible to go to a thicker layup schedule. Certainly it's more expensive that way too.


Bluewater Coosa was designed as a direct replacement for marine grade ply, structurally speaking. I'd be shocked if they had too much trouble bending this. After all, the original was done in ply by Taiwanese laborers. If the camber is just too much, go to two or even three layers of thinner Coosa, if they are afraid to kerf. Which they shouldn't be-after all the Divinycell is kerfed.



Margins should not be an issue. The normal method is to pattern, cut and fit strips of core material under the margins which extend 1-2" into the area where the upper skin was removed. Bond these margin strips in place first, using wood strips and a mallet to drive them in sideways as far as possible, and lots of core bond to ensure no voids. Sometimes margin strips need a bevel ground into them to match the original and prevent voids at the edge of the deck where it becomes solid glass. After margins are complete and resanded, then you do the rest of the deck.

[BigSmile]

Originally Posted by minaret

Yeah, I'm around, just got back from a month's cruise.


First concern I'd raise with yard-the Union 36 was designed with ply decks for a reason. They would have been a key portion of the structure of the deck on this boat. If they insist on replacing ply with foam core, they will need to really beef up the laminate schedule on both inner and outer skins to make up for the loss of strength and stiffness.

At this point, they are playing at yacht design, not repair. I try to stick to the original designers intent-occasionally they are just wrong, but for the most part they have done the math and can be relied upon. If you make major structural changes like this, then you too need to do the math. Also, it is not always easy or even possible to go to a thicker layup schedule. Certainly it's more expensive that way too.


Bluewater Coosa was designed as a direct replacement for marine grade ply, structurally speaking. I'd be shocked if they had too much trouble bending this. After all, the original was done in ply by Taiwanese laborers. If the camber is just too much, go to two or even three layers of thinner Coosa, if they are afraid to kerf. Which they shouldn't be-after all the Divinycell is kerfed.



Margins should not be an issue. The normal method is to pattern, cut and fit strips of core material under the margins which extend 1-2" into the area where the upper skin was removed. Bond these margin strips in place first, using wood strips and a mallet to drive them in sideways as far as possible, and lots of core bond to ensure no voids. Sometimes margin strips need a bevel ground into them to match the original and prevent voids at the edge of the deck where it becomes solid glass. After margins are complete and resanded, then you do the rest of the deck.

Thank You, as always very helpful! Hope you had a great cruise!

[BigSmile]

Originally Posted by minaret

Yeah, I'm around, just got back from a month's cruise.


First concern I'd raise with yard-the Union 36 was designed with ply decks for a reason. They would have been a key portion of the structure of the deck on this boat. If they insist on replacing ply with foam core, they will need to really beef up the laminate schedule on both inner and outer skins to make up for the loss of strength and stiffness.

At this point, they are playing at yacht design, not repair. I try to stick to the original designers intent-occasionally they are just wrong, but for the most part they have done the math and can be relied upon. If you make major structural changes like this, then you too need to do the math. Also, it is not always easy or even possible to go to a thicker layup schedule. Certainly it's more expensive that way too.


Bluewater Coosa was designed as a direct replacement for marine grade ply, structurally speaking. I'd be shocked if they had too much trouble bending this. After all, the original was done in ply by Taiwanese laborers. If the camber is just too much, go to two or even three layers of thinner Coosa, if they are afraid to kerf. Which they shouldn't be-after all the Divinycell is kerfed.



Margins should not be an issue. The normal method is to pattern, cut and fit strips of core material under the margins which extend 1-2" into the area where the upper skin was removed. Bond these margin strips in place first, using wood strips and a mallet to drive them in sideways as far as possible, and lots of core bond to ensure no voids. Sometimes margin strips need a bevel ground into them to match the original and prevent voids at the edge of the deck where it becomes solid glass. After margins are complete and resanded, then you do the rest of the deck.

Few more questions popped:

How is corebond best applied under the margins?

For the top skin, need to achieve 3/8" thickness for original construction/stiffness:
-I think that comes to 8 layers of the DBM 1708. Is this correct?
-Or 7 layers of DBM 1708 and a top layer of 17oz. woven e-glass alone

-How much different is the rollout with 17oz woven e-glass as the top layer versus for CSM 1.5oz?

How thick typically is gelcoat surface coating 1/16" ? Or better still how thick should it be? (Need to verify an overall height )

Wildcard - Deck patches that patched out prism cutouts are believed to have been done in epoxy. Evidence from inside salon suggests at least one was not done well. Will need to get better inspection on all these points. Also concern they are not compatible with poly. If so, is there a strategy other than cutting out and re-patching in poly?

And, deck hardware mounting thru-holes had tape applied on the interior underside, and were filled with unknown material. Is it possible to distinguish poly from epoxy by visual inspection?
If not, then I guess these would need to be re-done to be sure of new deck treatment in poly. Or?


Thanks again, appreciate your time and input.

[minaret]

Originally Posted by BigSmile

Few more questions popped:

How is corebond best applied under the margins?

Use short strips in the margin. Apply too much core bond quickly into the margin with a 3" putty knife, then drive in the margin piece with a mallet and scrap of ply. This will cause the excess to squeezeout. Collect the excess with putty knife and apply to next section of margin, then drive in next margin piece. You will quickly get a feel for how much core bond is required to not have any voids, or not have a ridiculous amount of squeezeout. It's very simple, the only tricky part is ending up with a fair line on the inboard side. Pattern and dry fit first. Your yard crew should already be good at this stuff.



For the top skin, need to achieve 3/8" thickness for original construction/stiffness:
-I think that comes to 8 layers of the DBM 1708. Is this correct?
-Or 7 layers of DBM 1708 and a top layer of 17oz. woven e-glass alone



Without getting out the manual, which has thicknesses at various resin contents for all weights of fabric, the general rule of thumb is 1/32" per ply for a hand lam. This is for 1708 lay ups, and much simplified, but still generally pretty reliable.



-How much different is the rollout with 17oz woven e-glass as the top layer versus for CSM 1.5oz?


You want to finish with one or two CSM, for numerous reasons. A final peel ply is always wise, as well.





How thick typically is gelcoat surface coating 1/16" ? Or better still how thick should it be? (Need to verify an overall height )





24 mils WFT, 16 mils DFT.





Wildcard - Deck patches that patched out prism cutouts are believed to have been done in epoxy. Evidence from inside salon suggests at least one was not done well. Will need to get better inspection on all these points. Also concern they are not compatible with poly. If so, is there a strategy other than cutting out and re-patching in poly?



Use a tie coat like 545. Better to have a single resin system.




And, deck hardware mounting thru-holes had tape applied on the interior underside, and were filled with unknown material. Is it possible to distinguish poly from epoxy by visual inspection?



Sand or grind and smell the dust. Poly has a distinctive odor.



If not, then I guess these would need to be re-done to be sure of new deck treatment in poly. Or?


Thanks again, appreciate your time and input.

Anytime, always happy to help. Are you doing this job, or is the yard?