Core Replacement Material ??

[Will W.]

Hi All
I am in the middle of replacing most of the floor of my CD25; skin and core. I've got the West System repair manual and so the how too's are mostly covered. One thing the manual does not do is recommend one type of core material over another. The three that seem to be available are; Marine grade plywood, Open Cell PVC Foam, and Honeycomb (no mention of what honeycomb is made of). I know of a wood supplier in Annapolis who can get me the wood, but I think you have to buy a whole sheet. I only need about 1/4 sheet. The West System repair manual says that the foam is more expensive, but I wonder if maybe I can buy just the amount I need? This brings me to the reason for this query.
Does anyone know where to get the PVC foam in flat sheets 1/4 inch thick? What should I expect to pay? Finally; does anyone have any opinions about these three core materials? Is one better than the others? I'm guessing that the foam is the easiest to work with in terms of cutting and shaping, is this correct?
As always your help will help me stay sane and do a good job all at the same time.

Will Wheatley
Suzi Q
CD25



willwheatley@starpower.net

[Don Carr]

Will; Defender sells (as do other fg shops) balsa core which is lighter and when resined is as strong as the other materials you mentioned.

FWIW



carrds@us.ibm.com

[Joel]

But shouldn't a goal of the repair also be the prevention of it rotting again should there be any water incursion? The man-made materials sound like they meet the goals of being lightweight and strong with the added benefit of being rot resistant.

Joel Bondy
s/y Pokey II
'73 Ty # 549

[Larry DeMers]

End Grained Balsa, if sealed off with epoxy before installation, will be pretty much impervious to water, lite and strong. The idea is to saturate the ends of the balsa (really the top and bottom of the sheet) and then install it while wet. This does a good job.

Although we used marine ply in our cockpit floor rebuild..at least for the large areas and under the pedestal (which Will does not have to worry about as he has a tiller on the 25D I believe). We used foam cut to shape for the edges of the floor, to allow for the 'gutter' at the margins of the floor. Works great!

Larry DeMers
s/v DeLaMer
Cape Dory 30

But shouldn't a goal of the repair also be the prevention of it rotting again should there be any water incursion? The man-made materials sound like they meet the goals of being lightweight and strong with the added benefit of being rot resistant.

Joel Bondy
s/y Pokey II
'73 Ty # 549

demers@sgi.com

[Greg Phillips2]

Will, I've had quite a bit of experience in boat building using a marine grade pressure treated plywood. It has been used successfully by many major boat manufacturers for years. Its compatible with both polyester and epoxy resins. If you have a boatbuilder in your area perhaps they could sell a partial sheet. Check out the manufacturer's website and related info thru Google by searching xl plywood. The company name is Greenwood Forest Products,www.greenwoodproducts.comxlpanel. If you use a foam core be sure to use a high density type. Greg Phillips

I am in the middle of replacing most of the floor of my CD25; skin and core. I've got the West System repair manual and so the how too's are mostly covered. One thing the manual does not do is recommend one type of core material over another. The three that seem to be available are; Marine grade plywood, Open Cell PVC Foam, and Honeycomb (no mention of what honeycomb is made of). I know of a wood supplier in Annapolis who can get me the wood, but I think you have to buy a whole sheet. I only need about 1/4 sheet. The West System repair manual says that the foam is more expensive, but I wonder if maybe I can buy just the amount I need? This brings me to the reason for this query.
Does anyone know where to get the PVC foam in flat sheets 1/4 inch thick? What should I expect to pay? Finally; does anyone have any opinions about these three core materials? Is one better than the others? I'm guessing that the foam is the easiest to work with in terms of cutting and shaping, is this correct?
As always your help will help me stay sane and do a good job all at the same time.

Will Wheatley
Suzi Q
CD25

2mileyc@digitalexp.com

[Bob B]

I have obtained foam sheets from Coosa Composites out of Birmingham, AL. They are making composite sheets that are reinforced with fiberglass and very strong. Some boat manufacturers are using these as replacements for the plywood that would have been in bulkheads and other framework for battery boxes, cabinet mounts and such. It will not rot but needs to be enclosed by epoxy or polyester resin.
Their address is:
Coosa Composites
105 Pardue Road
Pelham, AL 35124

Phone # 205-663-3225
You may ask for Chap Jackson and tell him that I referred you.

Bob Bundy



BundyR@aol.com

[Will W.]

Interestingly enough to mention here is that the only spot I found in the 2 foot by 4 foot hole I carved that was dry, was a repair that had been done long ago by someone else. It was only about 1 sq. foot and it was a Bi$#& to get out. I had to grind most of it down. So I agree that plywood installed properly will do the job. I was just wondering what the other options were.
Also the core that came out was 3/8 inch thick, not 1/4 as I said previously. Will

End Grained Balsa, if sealed off with epoxy before installation, will be pretty much impervious to water, lite and strong. The idea is to saturate the ends of the balsa (really the top and bottom of the sheet) and then install it while wet. This does a good job.

Although we used marine ply in our cockpit floor rebuild..at least for the large areas and under the pedestal (which Will does not have to worry about as he has a tiller on the 25D I believe). We used foam cut to shape for the edges of the floor, to allow for the 'gutter' at the margins of the floor. Works great!

Larry DeMers
s/v DeLaMer
Cape Dory 30

But shouldn't a goal of the repair also be the prevention of it rotting again should there be any water incursion? The man-made materials sound like they meet the goals of being lightweight and strong with the added benefit of being rot resistant.

Joel Bondy
s/y Pokey II
'73 Ty # 549

willwheatley@starpower.net

[Pete]

Any chance you could post pictures? It would be a great help to those of us considering undertaking similar repairs. Thanks!



peter@zwiefelhofer.com

[Glen Snader]

Will:

Why not go back with Balsa? You need to remember that the problem was not the core material (Balsa, foam, plywood or PVC)but a problem with water entering the core area or a design problem with the lay-up design/workmanship of the fiberglass skins. Any of the above core materials will not hold up to either of these problems. If the core is rotted, the core problem is the resualt of a undetected/repaired water leak. This leak must be found and fixed or there will be a core problem again sometime in the future.

If I were fixing this at my shop, I would use Balsa again. When installed properly, the life of Balsa should be the life of the boat. The laminate for any core should normaly be the same on both sides of the core. Also, The underside of the laminate should also be sealed, normaly with gelcoat. Remember, condensation is water. This needs to be keeped out of the core as well. That is why I always gelcoat the underside of our fiberglass parts. When looking for a core material to use in our 30' trawler/motorsailer, I settled on Balsa for the deck and topsides.

Good luck and e-mail the core companies direct. I am sure that they will be glad to help you and a local boat/fiberglass co. will sell you the core you need if they have it.

Glen Snader
Hobby Marine




glen@hobbymarine.com

[Will W.]

I am taking pictures but I do not have them posted anywhere yet. Larry and I and several others it appears, were thinking of getting a collective site to post this stuff on. Till then I can e-mail you what I got. Anyone interested can e-mail me at my address above with the subject line reading "core repair" and I will respond with the photos as an attachment.
Also glenn thanks for your responce. It seems that balsa core is also slightly more findable than some of the other things I mentioned as well. As far as the source of the problem goes, I had to laugh when I read that I must find the leak. Only because the hole in the cockpit floor was so enormous that I have tripped on it. I tried to ignore it but it just kept reminding me to fix it. Thanks everyone now I go searching for this stuff. I think the material that I wind up using will be the first one I can find easily. I went to Home Depot and asked about a cedar 2 by 4 and the guy looked at me like I had antlers. I found a slightly more knowledgeable person in insulation who told me that he knew the materials I was asking about and I would have to get them from the marine store, Duh.

Will Wheatley
Suzi Q
CD25

Any chance you could post pictures? It would be a great help to those of us considering undertaking similar repairs. Thanks!

willwheatley@starpower.net

[john doyle]

Hi All
I am in the middle of replacing most of the floor of my CD25; skin and core. I've got the West System repair manual and so the how too's are mostly covered. One thing the manual does not do is recommend one type of core material over another. The three that seem to be available are; Marine grade plywood, Open Cell PVC Foam, and Honeycomb (no mention of what honeycomb is made of). I know of a wood supplier in Annapolis who can get me the wood, but I think you have to buy a whole sheet. I only need about 1/4 sheet. The West System repair manual says that the foam is more expensive, but I wonder if maybe I can buy just the amount I need? This brings me to the reason for this query.
Does anyone know where to get the PVC foam in flat sheets 1/4 inch thick? What should I expect to pay? Finally; does anyone have any opinions about these three core materials? Is one better than the others? I'm guessing that the foam is the easiest to work with in terms of cutting and shaping, is this correct?
As always your help will help me stay sane and do a good job all at the same time.

Will Wheatley
Suzi Q
CD25

Found a good web site for this: http://www.rotdoctor.com/zine/rb994reflect.html



redzeplin@yahoo.com