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Wet core material

E

edokarura

Member II
The hole into which the latch on my chain locker door rests was cracked open. I took a Dremel tool and cut away the outside and have started digging out (balsa?) wood. At first the stuff that came out was black. More digging brought yellow wood but you could squeeze water out of it. Digging beyond that brings out wood that is lighter in color and does not yield water when squeezed but is obviously still moist.

I know I'm supposed to keep digging until I get to dry wood but the farther back I go the more difficult it will be to pump resin back into the void and fill it completely without drilling holes into the topside and injecting it with a syringe. Plus, I don't know how far back I'm going to have to go.

Soooooo………The questions are……

How much moisture could I safely leave in there? I'm certain it is virtually all fresh water.

If the answer is "zero" then could anyone suggest an effective means of driving out the remaining moisture? I was thinking about putting a phalanx of ceramic heaters beneath it and/or covering it with heating pads.

Thanks in advance. You guys are always a big help.

Ed
"Kinnaree"
1991 E-34
IMG_0105.jpgIMG_0109.jpg
 
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G

Glyn Judson

Moderator
Moderator
Core removal.

Ed, Is there room to remove core from the underside? It wood be a good excuse to buy a Dremel tool, RotoZip or a #3706 Makita Cutout tool. Glyn Judson, E31 hull #55, Marina del Rey CA
 
P

PDX

Member III
edokarura said:
The hole into which the latch on my chain locker door rests was cracked open. I took a Dremel tool and cut away the outside and have started digging out (balsa?) wood. At first the stuff that came out was black. More digging brought yellow wood but you could squeeze water out of it. Digging beyond that brings out wood that is lighter in color and does not yield water when squeezed but is obviously still moist.

I know I'm supposed to keep digging until I get to dry wood but the farther back I go the more difficult it will be to pump resin back into the void and fill it completely without drilling holes into the topside and injecting it with a syringe. Plus, I don't know how far back I'm going to have to go.

Soooooo………The questions are……

How much moisture could I safely leave in there? I'm certain it is virtually all fresh water.

If the answer is "zero" then could anyone suggest an effective means of driving out the remaining moisture? I was thinking about putting a phalanx of ceramic heaters beneath it and/or covering it with heating pads.

Thanks in advance. You guys are always a big help.

Ed
"Kinnaree"
1991 E-34
View attachment 13764View attachment 13765
Click to expand...

You might want to locate a moisture meter to find out how large a problem you are dealing with. This would impact the method I would use.

If its a small area, there are articles on driving out the moisture by drilling holes, heating or letting dry, and then ceiling off the bottom and injecting with thickened epoxy. I believe such can be found in one of Don Casey's books. The finished product will not be as good, or as strong, as a true balsa sandwich, but if the area is small enough maybe you could live with it.

If the affected area is large (as large or larger than the project Davisr describes) I would look for a way to replace the affected core. Ergonomically it would be easier to approach it topside. Maintaining the crown of the deck would be a challenge, especially if the affected area is really large. You might have to do it piecemeal. Approaching underside, the core replacement could be done all at once, but getting in there and working might be a challenge, especially if your anchor locker has no aft access back through the crash bulkhead. Is it large enough for someone to get inside?
 
E

edokarura

Member II
Glyn Judson said:
Ed, Is there room to remove core from the underside? It wood be a good excuse to buy a Dremel tool, RotoZip or a #3706 Makita Cutout tool. Glyn Judson, E31 hull #55, Marina del Rey CA
Click to expand...

Maybe. I'd have to take down the headliner. Got a Dremel. I'll look at those other tools you suggested. Thanks!
 
E

edokarura

Member II
What would you think about filling it with polyester resin mixed with chopped fiberglass?

I want to be able to gelcoat over the holes when I'm done and understand that gelcoat won't stick to epoxy.

When you say that the fix wouldn't be as good as if I put balsa in there I can't really imagine I could notice the difference. Right now we're talking about and area of about 10 square inches. What will I notice? Bowing? Cracking?

Thanks!!!

Ed




PDX said:
You might want to locate a moisture meter to find out how large a problem you are dealing with. This would impact the method I would use.

If its a small area, there are articles on driving out the moisture by drilling holes, heating or letting dry, and then ceiling off the bottom and injecting with thickened epoxy. I believe such can be found in one of Don Casey's books. The finished product will not be as good, or as strong, as a true balsa sandwich, but if the area is small enough maybe you could live with it.

If the affected area is large (as large or larger than the project Davisr describes) I would look for a way to replace the affected core. Ergonomically it would be easier to approach it topside. Maintaining the crown of the deck would be a challenge, especially if the affected area is really large. You might have to do it piecemeal. Approaching underside, the core replacement could be done all at once, but getting in there and working might be a challenge, especially if your anchor locker has no aft access back through the crash bulkhead. Is it large enough for someone to get inside?
Click to expand...
 
M

Macgyro

Amazingly Still Afloat
Blogs Author
Gel coat over epoxy

As far as I know, some types Gel Coat will stick to epoxy, as long as the epoxy is fully cured (around a week or two) and you remove the animie blush (no clue how to spell it). The first coat of gelcoat I applied just melted and slid off. Then I read more about it in the West System user guide and it worked fine after letting the epoxy cure properly. (I think I also had to buy a compatible gel coat)

bayliner damage.jpgbayliner repair.jpg

I think the only drawbacks to using a different wood in the core is different flexing properties which could work at the joints of your repair and the extra weight plywood adds relative to balsa. (I'm going to use plywood to patch an area around my chainplate, so in my opinion, it's not that big a deal)

Good Luck!
Dean




edokarura said:
What would you think about filling it with polyester resin mixed with chopped fiberglass?

I want to be able to gelcoat over the holes when I'm done and understand that gelcoat won't stick to epoxy.

When you say that the fix wouldn't be as good as if I put balsa in there I can't really imagine I could notice the difference. Right now we're talking about and area of about 10 square inches. What will I notice? Bowing? Cracking?

Thanks!!!

Ed
Click to expand...
 
P

PDX

Member III
Macgyro said:
As far as I know, some types Gel Coat will stick to epoxy, as long as the epoxy is fully cured (around a week or two) and you remove the animie blush (no clue how to spell it). The first coat of gelcoat I applied just melted and slid off. Then I read more about it in the West System user guide and it worked fine after letting the epoxy cure properly. (I think I also had to buy a compatible gel coat)

View attachment 13770View attachment 13771

I think the only drawbacks to using a different wood in the core is different flexing properties which could work at the joints of your repair and the extra weight plywood adds relative to balsa. (I'm going to use plywood to patch an area around my chainplate, so in my opinion, it's not that big a deal)

Good Luck!
Dean
Click to expand...


To be clear, when I say, "It won't be as good as the original," I'm not talking about substituting balsa with plywood. Plywood may be heavier but it is stronger. With either core wood you still have a sandwich construction of polyester (or epoxy) resin saturated glass supporting a wood core on both sides. The strength comes from the sandwich layup. There is no sandwich layup if you are injecting resin into voids left by rotted out balsa. Essentially you would have a deck area of solidified resin with remnants of dried out but rotted balsa floating in it. That doesn't mean it would be terrible, just not as strong as the original. I don't know what the loads or stresses are in the rotted area of your deck. If it is supporting a bow roller, stemhead fitting, or cleats, I wouldn't do it without a wood (or foam) core.
 
tenders

tenders

Innocent Bystander
My attempts to inject epoxy into rotted balsa were eventually called out when I had to cut off the top skin for a proper repair. Epoxy injection is a placebo - it might make you feel better but it doesn't stop the problem from getting worse and it doesn't solve any structural issues you may be concerned about. It is in fact a waste of time.

* The epoxy is literally swimming in wet balsa - the balsa took decades to get wet and will not get dry in our lifetimes
* The void is irregularly shaped - the idea that the epoxy is sitting in there like a nice little puck supporting both sides of the skin is pure fallacy. It's a random blob in there.

Also I applaud the gymnastic and physics skills of those who can effect core replacement from below, defying gravity and shoehorning their tools and bodies for long periods of time into tiny areas. But very acceptable outcomes can be achieved from the top with gravity working with you, not against you!
 
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