The Science of Soggy Decks

[colemj]

Mixed balsa/ply decks are not unusual. They are really just balsa cored decks with ply applied in high load spots like traveller tracks and winch mounts. Balsa crushes easily in these spots.

I would recore with balsa before ply. The cost will be the same. Make high load areas solid glass, along with any penetration areas. Coosa is better, of course, but if you cannot source it, balsa is an excellent core material with a bad reputation because it is rarely installed correctly with all penetrations boxed out with solid laminate. For an amateur, balsa is easier to work with and bond to than foam.

The use of acetone and alcohols for drying hulls is rarely done correctly and rarely successful outside of very small areas. One cannot just soak the core with these and wait for it to dry. Acetone and alcohol mix with water and lowers its viscosity and surface tension. This allows it to be transported out of the medium it is caught in. However, the key word is "transported". If you simply soak the core and let the acetone evaporate, most of the water will be left behind. To make this work, one needs vacuum or a large amount of heat (or both) to move the water out of the core.

For non-skid, I have had excellent results (to me) by using cabosil thickened gelcoat and a medium roller to roll on a uniform stippled nonskid. It is inexpensive, looks good and lasts well. I MUCH prefer it over adding sand or "nonskid" additives to paint. The cabosil makes the gelcoat resistant to wear. If it comes out too aggressive, it is easy to just lightly hit it with a sanding board to knock down the sharp points.

On boats with narrow side decks and smallish open areas, I have had good results bonding the old topskin back on. The panels are small enough that it is easy to get them bonded without voids and the smooth wide water runs where cuts are made are easy to get a good flat reglass done in with minimal effort. I always grind the topskin, glass on a layer of thin mat for a transition bond and pot it in corebond or cabosil thickened resin to the similarly prepared core that has already been bonded in the deck. For large open areas, I agree that it is difficult to avoid voids, although corebond helps.

If you are going to cut out ANY part of your deck, do the whole thing - or at least a large part of the area in question. If you don't, you WILL be going back into it in the future. If your only moisture is in the back deck, then replace that whole back deck instead of doing a spot repair. The only exception for me is if you have moisture just around fittings, where I would consider cutting back to dry core, boxing the core out with epoxy and refitting solid glass.

On the other hand, you can live with wet decks. They are not a danger until they become so bad that you cannot walk on them safely. This takes a long time. You will never sell the boat that way, but can pick your time to make the repair.

Mark

[Cheechako]

I doubt with most boats that wet core is a big safety issue. Depends on the boat I'm sure and on the internal structure of the boat. Earlier boats were just built with uncored decks, which tend to flex a little. How thick your outside laminate is makes a difference and how many bulkheads tie the whole structure together. Alot of Taiwan boats tend to have core issues, but then, their outside laminate is really thick anyway! Seems to me Balsa or Airex is easier to work with than plywood. If you are going with ply In the deck, you might as well just use exterior ply; I've been told it's the same glue as marine ply... just the grade of wood is higher on marine ply... so there are no blemishes or voids. Passport used taiwanese ply for their decks using little sqares of it (3"). Their thinking was if they fill between the squares with resin, leaks cant migrate.... Ply will out last your ownership... but balsa etc is just niceer to work with. If you use ply, cut it into squares so it takes the deck contour well. As mentioned, the real problem isnt the balsa.... it's penetrating the deck with hardware fastners...

[GordMay]

Originally Posted by Cheechako

... If you are going with ply In the deck, you might as well just use exterior ply; I've been told it's the same glue as marine ply... just the grade of wood is higher on marine ply... so there are no blemishes or voids. ...

Yes, exterior grade & marine grade plywoods generally use the same adhesives, BUT:
With marine grade, the lowest grade veneer is "B", which means that there will be no serious voids on the surface and interior plies.
It is the voids that cause poor adhesion.
So, marine grade will have good adhesion throughout the lamination.
Also, marine grade can be cut without getting a void in one laminate on a freshly cut edge. The edges will be totally solid.

[minaret]

Originally Posted by Cheechako

I doubt with most boats that wet core is a big safety issue. Depends on the boat I'm sure and on the internal structure of the boat. Earlier boats were just built with uncored decks, which tend to flex a little. How thick your outside laminate is makes a difference and how many bulkheads tie the whole structure together. Alot of Taiwan boats tend to have core issues, but then, their outside laminate is really thick anyway! Seems to me Balsa or Airex is easier to work with than plywood. If you are going with ply In the deck, you might as well just use exterior ply; I've been told it's the same glue as marine ply... just the grade of wood is higher on marine ply... so there are no blemishes or voids. Passport used taiwanese ply for their decks using little sqares of it (3"). Their thinking was if they fill between the squares with resin, leaks cant migrate.... Ply will out last your ownership... but balsa etc is just niceer to work with. If you use ply, cut it into squares so it takes the deck contour well. As mentioned, the real problem isnt the balsa.... it's penetrating the deck with hardware fastners...

I wouldn't say it's not a safety issue at all. I've never seen it happen but I could easily see a sheet traveler, winch, or other piece of deck hardware having a catastrophic failure due to being mounted on rotten core. Injury could easily ensue. I've seen many cases of rotten deck core due to the hardware being under high repeated loads, causing the bedding to fail. Just the sort of thing you don't want to fail is the most likely to fail when mounted on an improperly prepared cored deck. You'd almost certainly notice long before it got bad enough for any such thing to occur, but if you ignore it for long enough I think it could become unsafe. Particularly in the case of ply core, where they may be relying on the ply to provide a lot of the necessary strength for the deck fitting.

[Cheechako]

Yes, exterior grade & marine grade plywoods generally use the same adhesives, BUT:
With marine grade, the lowest grade veneer is "B", which means that there will be no serious voids on the surface and interior plies.
It is the voids that cause poor adhesion.
So, marine grade will have good adhesion throughout the lamination.
Also, marine grade can be cut without getting a void in one laminate on a freshly cut edge. The edges will be totally solid.
Yeah, I just figure that much of a cored deck is "void" by design, so a few voids in the ply really is of no consequence!

Good point Minaret! Important for high load areas to be good for sure! I think it would be rare though, a well fastened fitting would have to pull a chunk of the inner glass, and outer glass away along with the rotten core... Many Genoa tracks on teak capped bulwarks are simply screwed on... and more likely to fail I imagine!

[webejammin]

If you are thinking about how strong your water damaged deck is you better read the posts about the 3 Canadian guys who lost there rigging heading to Hawaii, there forestay pulled out a big chunk of the bow deck out as the mast fell aft with one of them aloft in 20+ seas and gail winds. They started taking on water thru the deck hole and had to be picked up by a big ship that after the crew was off there boat the boat was crushed and sank under the ship.

I hear if you put your boat on the hard in a desert inviroment low low humidity and 100 deg's F for a year or so ( like the Mexican Baha ) it will eventually dry out and you can start repairs.

[justwaiting]

Originally Posted by webejammin

I hear if you put your boat on the hard in a desert inviroment low low humidity and 100 deg's F for a year or so ( like the Mexican Baha ) it will eventually dry out and you can start repairs.

Are you sure that this is such a good idea?

1. what would be the effect of the sun (UV and heat) on the boat and its systems?
2. would the water realy dry out?
3. if the water did dry out it surely would tend to dry from any none seal areas of the deck first, prob where the water entered in the first place. Would this (assuming drying had occoured) make it even harder to determing the causes and location of the problem?
4. if the answer to 2 was yes, wouldnt this give dry rot more time to damage and spread spores through the deck?
5. dont boats that get put on the hard tend to just stay there?
6. wouldnt there be costs associated with hauling/storeing and owning an asset (liability ) that is doing nothing?

i would think that fixing the problem when its full extent can be identifed without resorting to destructional techniques would be less expensive and more effective in the long run. But then there is the question of boat bucks

[webejammin]

Originally Posted by justwaiting

Are you sure that this is such a good idea?

1. what would be the effect of the sun (UV and heat) on the boat and its systems?
2. would the water realy dry out?
3. if the water did dry out it surely would tend to dry from any none seal areas of the deck first, prob where the water entered in the first place. Would this (assuming drying had occoured) make it even harder to determing the causes and location of the problem?
4. if the answer to 2 was yes, wouldnt this give dry rot more time to damage and spread spores through the deck?
5. dont boats that get put on the hard tend to just stay there?
6. wouldnt there be costs associated with hauling/storeing and owning an asset (liability ) that is doing nothing?

i would think that fixing the problem when its full extent can be identifed without resorting to destructional techniques would be less expensive and more effective in the long run. But then there is the question of boat bucks

All I know for sure is that while the boat is on the hard the rigging won't pull out and sink the boat.

[Cheechako]

Originally Posted by webejammin

If you are thinking about how strong your water damaged deck is you better read the posts about the 3 Canadian guys who lost there rigging heading to Hawaii, there forestay pulled out a big chunk of the bow deck out as the mast fell aft with one of them aloft in 20+ seas and gail winds. They started taking on water thru the deck hole and had to be picked up by a big ship that after the crew was off there boat the boat was crushed and sank under the ship.
.

hmmm....... one would have to ask: what is the forestay doing supported by the deck alone??? Or even penetrating the deck for that matter.....

[minaret]

Originally Posted by Cheechako

hmmm....... one would have to ask: what is the forestay doing supported by the deck alone??? Or even penetrating the deck for that matter.....

Agreed. Chainplates are never just attached to a deck. This case would have required both a rotten deck and a rotten bulkhead. But the one can certainly contribute to the other. Especially around through deck chainplates.

[travler37]

Originally Posted by unbusted67

We bought our boat very cheap because the surveyor found moisture in a couple of large swaths in the deck. We are committed to getting it fixed even if it means cutting out sections and replacing them...but I would like to try the cheap and easy way first and try to dry out sections using a heater.

We have very good under deck access to the affected areas and I have been thinking of drilling a few pilot holes to let the moisture out and just slamming it with heat to see if I can get the readings on the meter down. My thought is that if the moisture found its way in there it can probably find it's way out through evaporation.

I would love to hear from anyone who has successfully dried a section of cored deck with just a heater. I would also love to hear from anyone who has been unsuccessful.



On a bit of a side note, I am wondering about the structural integrity of these sections. They are not showing any signs of a moist deck. No thud when you tap it, no squishiness under foot, and when we drilled out a pilot hole with the a hole saw we found the core (I think it is balsa) to be dry to the touch. Still the meter doesn't like it.

the DO NOT LIST
Do NOT TELL anyone
DO NOT smoke
DO NOT TELL
Go to home depot and get 2 grease guns and a assortment of zerk fittings....
get 2 gallons of acetone.
drill 1/8th hols about 1 inch apart in the effected area..top and bottom...
screw zerk fittings to said holes.......
fill one grease gun with acetone and pump said fittings.these are on the bottom.........
let stand for a week........
repeat for top
Start at bottom with first grease gun......fill bottom holes with runny epoxy.Use same zerk fitting for all holes just gorilla tape holes after 3 pumps..............
go and get drunk for the night.......
repeat for top untill iepoxy comes out of hole...
Sand and put new alwgrip over ENTIRE TOPSIDE......MAKE IT LOOK PRETTY......
AND NEVER TELLL
Mark

[Cheechako]

Forget the meter. drill a small hole where you can from below in various places. (hanging lockers etc) remove the balsa from the twisted bit each time you drill. Squeeze the balsa chips between your thumb and fingers. Any moisture come out? I hope you're not tearing up your boat based on a moisture meter. The meter is reading the skin not the balsa.....

[colemj]

Originally Posted by travler37

the DO NOT LIST
Do NOT TELL anyone
DO NOT smoke
DO NOT TELL
Go to home depot and get 2 grease guns and a assortment of zerk fittings....
get 2 gallons of acetone.
drill 1/8th hols about 1 inch apart in the effected area..top and bottom...
screw zerk fittings to said holes.......
fill one grease gun with acetone and pump said fittings.these are on the bottom.........
let stand for a week........
repeat for top
Start at bottom with first grease gun......fill bottom holes with runny epoxy.Use same zerk fitting for all holes just gorilla tape holes after 3 pumps..............
go and get drunk for the night.......
repeat for top untill iepoxy comes out of hole...
Sand and put new alwgrip over ENTIRE TOPSIDE......MAKE IT LOOK PRETTY......
AND NEVER TELLL
Mark

OK, I'll bite - how do you get acetone to stay in a grease gun and inject it under pressure? All grease guns I know of are not sealed for the viscosity of acetone and most of them use cartridges.

Other than that, the rest of what you post is so wrong that I can see why you think you should NEVER TELL.

Mark

[s/v Jedi]

Originally Posted by colemj

OK, I'll bite - how do you get acetone to stay in a grease gun and inject it under pressure? All grease guns I know of are not sealed for the viscosity of acetone and most of them use cartridges.

Other than that, the rest of what you post is so wrong that I can see why you think you should NEVER TELL.

Mark

I also don't get the "get drunk tonight" part... must be a new technique.

ciao!
Nick.

[unbusted67]

Originally Posted by travler37

the DO NOT LIST
Do NOT TELL anyone
DO NOT smoke
DO NOT TELL
Go to home depot and get 2 grease guns and a assortment of zerk fittings....
get 2 gallons of acetone.
drill 1/8th hols about 1 inch apart in the effected area..top and bottom...
screw zerk fittings to said holes.......
fill one grease gun with acetone and pump said fittings.these are on the bottom.........
let stand for a week........
repeat for top
Start at bottom with first grease gun......fill bottom holes with runny epoxy.Use same zerk fitting for all holes just gorilla tape holes after 3 pumps..............
go and get drunk for the night.......
repeat for top untill iepoxy comes out of hole...
Sand and put new alwgrip over ENTIRE TOPSIDE......MAKE IT LOOK PRETTY......
AND NEVER TELLL
Mark

No No, I hear you. Everyone has an opinion about how everything has to be done perfectly. Everything is done with a surveyor and the next buyer in mind and everything has to be practical.

It's annoying.

Sometimes it's just all about getting the boat working to a point to where you can sail it somewhere and go.

I used this analogy the other day with my girlfriend. Say you bought a car from 1983 to drive cross country and it had rust in the hood. Would you throw some bondo on the hood and drive it or would you feel compelled to strip the entire car down and make it like new?

It is very easy, especially for me, to feel like every bit of maintenance has to be geared towards making your boat Bristol and ready for resale.


With that said I am taking everyone's advice and doing this the right way because it is not worth the trouble down the line.