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Rotten core

Jarod

Member III
Hi All,

I was replacing my nav lights on the bow of the ole E27 last Sunday and encountered some brown slime (formerly balsa wood). I removed all of the hardware from the deck and drilled some exploratory holes beneath from the bow back as far as the vent for the anchor line (approx 2 feet)...the core is wet that far back, but has not delaminated and when i went past the vent i found the core to be bone dry...so not alot of water intrusion in the deck but enough that it needs to be dealt with...i have about 8 holes drilled in the bottom now about 2 inches diameter with my hole saw...and a dryer beneath...the deck is tarped over and now i am looking for advice....i will not peel the top layer off for this amt of dmg so please give me other options....remember the first 16 inches from the bow aft is pretty much a right off...either slime or black completely saturated balsa...
thanks jarod
 

Emerald

Moderator
Have you worked with epoxy? This shouldn't be too bad a project. Basically, cut out from below the section that needs to be replaced, recore, and glass back over. Search this site for things like "core repair", "deck repair", etc., and you'll get some usefule hits. Also, check out the projects section of EpoxyWorks Magazine (from West Systems).

http://www.epoxyworks.com/indexprojects.html

http://www.epoxyworks.com/

You may want to use a core material other than balsa, e.g. Klegcell. Of note, balsa is still a great core material, just have some options.

It doesn't sound like you have a huge area to deal with, but depending on your local sources, check US Composites for your fiber-glass material needs:

http://www.shopmaninc.com/

And finally, here's a link to recoring the step on my mast, which is more or less what you are doing, but you'll be upside down with it falling in your hair, face, etc. :devil:


http://home.comcast.net/~independence31/core/looksbad.html


Good luck!
 

Jarod

Member III
I was wondering if i could not just fill the void with a thin mix epoxy. The area that needs to be filled is probably about twelve inches square in total..not a square but that much area once i have ground out all the rotten stuff. I have channels dug in the core to all of the effected areas and I can get access from above via the stanchion holes and the nav light holes....i would think with a thin enough epoxy it might just flow....is this possible or just wishfull thinking...and if it is possible what is the best flowing epoxy folks have used.

thanks
 

Emerald

Moderator
I know it is tempting to flood it with epoxy, but your description sounds like the balsa core has lost all integrity. If the core was merely wet, and there was no delamination, I would be more enthusiastic about drying it and a penetrating epoxy. Your description of black mung sounds like the core is mush and has lost all integrity. Part of how the balsa works so well is you may recall the description of "end-grain" when reading about deck cores. The balsa fibers in this direction, under compression, are very strong. Balsa also has good water resistance to rot. However, once the grain, fiber of the wood is gone, there isn't anything left to work with. Pure epoxy is brittle - it needs a core, cloth etc. to have true strength. Also, this little triangle area at the tip of your deck probably should be stronger than you might initially think. I am not engineer, but experience fabricating stuff over the years makes my gut feel that the point where the two sides of the hull and the deck come together and the forestay attaches as a stress area, and it should be fixed for maximum strength.

OK, so where are you now? If you really think the balsa is OK, and you don't have delamination, check out something like Smith's Clear Penetrating Epoxy Sealer™, but I think I would call and talk to their techs and describe what you have before going this route. Their website is:

http://www.smithandcompany.org/

Tap around with the handle end of a screwdriver and listen for sound changes. Sharp rap is OK, dull thud is not. Be aware that on most Ericsons, if not all, the areas under cleats, stanchions, etc., have plywood instead of balsa, and you will get a sound change due to the core change - don't get faked out by this, just pay attention to where you are taping.

It may seem intimidating to take the router/saw to the underside of the deck there, but it really isn't that hard - just a little patience and you'll do fine. Once you cut it open from the inside, you will probably find the bad stuff extends a bit further than you expect. Don't be daunted, dig it out, and give it a good sanding on what is now the underside of your deck skin. You'll be surprised how good it feels to get the goo out. If you read through the link to my mast step recore in my prior post, you'll see how I bedded the new core in a thickened epoxy mix, and then it was just cloth on top of that. Really pretty easy once you start working through it. Also, I talked with West Systems, and with proper temperature control on your resins, work area etc., you can work down to 40F, even upper 30's. Here's a link to a .pdf document on their site on cold work:

http://www.westsystem.com/webpages/userinfo/moreinfo/000-915.pdf

I mention this in case you are worried about running out of time due to weather. I did my recore in December on the Chesapeake with these temps during the day, and colder at night.

Other thoughts you may have already considered. Do remove that wood piece from in front of the V-berths that seperates the anchor rhode locker from the cabin and you'll have much better working space. While your at it, you may want to pull the bow pulpit and rebed it, and fill with thickened epoxy the bolt holes and redrill. Remove all cushions, sails etc. from the cabin before you start this. You will have to clean the cabin of fiberglass dust when this is all done. Finally, go for it. Learning how to work with epoxy and core is a great skill to have if you love sailing and maintaining our classic plastic boats :egrin:


One last thought, I have mentioned several brands of products - I have no affiliation with any vendor of anything -have just used these things with success.
 
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CaptnNero

Accelerant
Hi All,

I was replacing my nav lights on the bow of the ole E27 last Sunday and encountered some brown slime (formerly balsa wood). ...

Jarod,

As I recall the water intrusion will not cause rotting unless air also reaches the wet balsa. The brown slime of course is suggestive of that process. So the areas of rotten core versus wet core need to be carefully determined. It sounds like you may be thinking that way already but I just wanted to clarify.
 
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Emerald

Moderator
Neal makes a good point on wet versus rotten. Something I didn't mention above is that for any repair method to work, you will need the core and surrounding areas to be completely dry. Obviously, this is easy if you dig out the old and replace. If you are trying to dry what is there, it might take a very long time to get if really dry.
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Are you guys sure that going at this from the underside of the deck is the best way? I understand that it's nice to keep the deck skin intact if possible, and that this project can be completed from underneath. But I wonder if it wouldn't turn out better if he cut the deck open and retained the cut-out section in one piece, then scraped out the old core, added new and then re-installed the top deck skin, filling in the cracks with epoxy/gelcoat.

My rationale is that working upside-down in the v-berth is not only messy, but it's so uncomfortable that he'll be rushing the work; as well, it will be harder to keep everything in place and avoid voids, etc.

Just my thoughts....good luck, whichever method is chosen1
Frank
 

Glyn Judson

Moderator
Moderator
Core replacement from below.

Frank and all, Go to the Projects section of http://www.ericson31.com/ and then to the Core Delamination Repair subject heading to see how Brian Sokol did the overhead in his E31. I think his method answers your concern about not leaving voids. It also avoids scarring of the nonskid pattern outside as a large benefit. Glyn E31 hull #55, Marina del Rey CA
 

CaptnNero

Accelerant
Neal makes a good point on wet versus rotten. Something I didn't mention above is that for any repair method to work, you will need the core and surrounding areas to be completely dry. Obviously, this is easy if you dig out the old and replace. If you are trying to dry what is there, it might take a very long time to get if really dry.

I read a book on fiberglass repairs but I haven't done anything serious other than rebuilding an anchor locker lid. For wet decks I know there are procedures for drilling from the top and bottom and then flushing with acetone which drives out the water, then letting the acetone dry.

If I were faced with the repair under discussion I would either consult/employ a professional or remove the skin from below as David suggests so that I could see the exact scope of the damage and remove it. Deck repairs are also done from above when it is not practical to work from below. When I removed the bottom skin from that anchor locker lid I was surprised at how much damage there actually was.

Working from below there will be issues with getting the right consistency so the replaced materials hold vertically well until set. I suppose there are procedures to make that eaiser to deal with. I've found that once you get some practice with working with fiberglass it goes very quickly. If this repair can be done from below you won't have to worry about cosmetic issues which I think is the most delicate part of the repair.
 

Emerald

Moderator
Another plus from below is that since there are no cosmetic issues, you can have a nice overlap of the new cloth (over the new core) back on to original fiberglass surrounding the area. While it is possible to do a good butt joint cutting the appropriate bevel (12:1), it is even better if you can overlap onto good solid material and have more surface area for bonding.
 
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