Bought a 1998 Sea Ray Sundancer 270 wide beam with rot...

[drewm3i]

To amend Ted's diagram slightly, I would say only half of the motor mount stringers are rotten. Also, the rot goes a bit further forward on the starboard stringer.

 

[Baylinerchuck]

Just out of curiosity, are the fuel tanks on most boats sandwiched by the stringers, (held in tight)? Would this lead to rot by moisture on the outside of the tank not being able to escape. Since fuel is kept underground its much colder in the summer than ambient, and would cause the tank to condensate. My Chap the tank was tight against the stringer, the thin rubber spacers didn't do much to space it out. How much space between the stinger/ bulkhead and tank is ample? Sorry if I hi-jacked the thread, I try to learn as I go and plenty of these posts stir the cobwebs in my head.......:noidea:

 

[drewm3i]

Just out of curiosity, are the fuel tanks on most boats sandwiched by the stringers, (held in tight)? Would this lead to rot by moisture on the outside of the tank not being able to escape. Since fuel is kept underground its much colder in the summer than ambient, and would cause the tank to condensate. My Chap the tank was tight against the stringer, the thin rubber spacers didn't do much to space it out. How much space between the stinger/ bulkhead and tank is ample? Sorry if I hi-jacked the thread, I try to learn as I go and plenty of these posts stir the cobwebs in my head.......:noidea:

No worries man. Yes I think it is common for tanks to be sandwiched between stringers and I think that is a good design. I think you are overthinking it with the condensation and what not. The bottom line is boats rot because the materials used suck, the glass work is sloppy, BUT MOST IMPORTANTLY because bad owners allow them to get wet beneath decks by keeping water in the bilge, spraying a wooden deck with water, or leaving the boat uncovered. A little condensation is no big deal IMO. Repeated saturation though and standing water with unsealed holes and half-ass glasswork IS.

I have had two mint Chaps. Neither had any semblance of rot. One had excess flex in the wood floor though because the factory forget to put a 2x4 under the deck to support it, which over time led to a crack in the CSM covering the deck and a crack in the plywood. That boat was well built otherwise though, but the deck needed to be supported better.

 

[Baylinerchuck]

I think you are overthinking it with the condensation and what not. The bottom line is boats rot because the materials used suck, the glass work is sloppy, BUT MOST IMPORTANTLY because bad owners allow them to get wet beneath decks by keeping water in the bilge, spraying a wooden deck with water, or leaving the boat uncovered. A little condensation is no big deal IMO. Repeated saturation though and standing water with unsealed holes and half-*** glasswork IS.

LOL, these things come to me after about the second hour of a fiberglass grinding session.....delerium? No, just too much thinking time!! :crazy:

 

[alldodge]

Since you answered I'll comment:
Aluminum fuel tanks can be damaged by water sitting for long terms on the out side. Water doesn't build up from condensation and cause the issue, it's caused by an outside source. Either a leak in the hull or interior system leak.

 

[drewm3i]

Since you answered I'll comment:
Aluminum fuel tanks can be damaged by water sitting for long terms on the out side. Water doesn't build up from condensation and cause the issue, it's caused by an outside source. Either a leak in the hull or interior system leak.

Yup, which is why all boats should have plastic tanks and not aluminum. It would be better to have multiple plastic tanks vs. one aluminum. Plastic lasts forever.

 

[tpenfield]

As far as the fuel tank placement in a boat's structure . . .

You want the fuel tank surrounded by the strongest portions of the structure and that is most often between the main stringers. Sometimes the fuel tanks are surrounded by air gaps, which are supposed to provide room for evaporation to remedy the condensation. Sometimes the tank is foamed in to provide a tight seal and more structural integrity to the tank and boat alike.



I made a slight adjustment to the drawing, based on Drew's comments.





BTW - I am using a new (to me) 3D modeling program called "SketchUp" . . . I think I have most of the boat's structure now included in the model.

 

[drewm3i]

As far as the fuel tank placement in a boat's structure . . .

You want the fuel tank surrounded by the strongest portions of the structure and that is most often between the main stringers. Sometimes the fuel tanks are surrounded by air gaps, which are supposed to provide room for evaporation to remedy the condensation. Sometimes the tank is foamed in to provide a tight seal and more structural integrity to the tank and boat alike.



I made a slight adjustment to the drawing, based on Drew's comments.





BTW - I am using a new (to me) 3D modeling program called "SketchUp" . . . I think I have most of the boat's structure now included in the model.

Wow, I am impressed pal! I'm working on getting a trailer/haul. Do you think 3 stacks of blocks and 6 stands are adequate support the hull while performing surgery on the boat?

 

[tpenfield]

Wow, I am impressed pal! I'm working on getting a trailer/haul. Do you think 3 stacks of blocks and 6 stands are adequate support the hull while performing surgery on the boat?

You are welcome . . . sorry that I can't come see the boat today, but the drawings that Sea Ray sent, plus the pictures you posted are the next best thing to being there. I *think* this would be the way to approach the repair . . .

Here is your boat's structure . . .



I would . . .remove the outdrives, engines, etc.

Remove the panel covering the fuel tank.

Remove the fuel tank . . .

This will then give you an 'inside' view of the bulkhead and the main stringers so you can verify the extend of the damage.

You may have to cut out part of the aft berth base on the starboard side to expose the starboard stringer more thoroughly. This will be more repairable and I don't think you will have to remove the aft berth bulkheads. You probably will need to cover the vinyl wall upholstery, etc. with plastic drop cloth.



You should then be able to remove the culprit bulkhead and cut back the starboard stringer as needed.

You could also 'slice' the top of the engine mount stringers to expose the bad wood, clean them out and prep them for seacast filling. (Keep the tops that you cut off to re-apply them later)



Then, it is a matter of building things back the way that they were. You probably want to take lots of measurements before you do the demolition so that you can reference them as you re-build.

Anyway, that's how I would envision it being done, but I'm sure there will be a few 'gotchas' along the way and other forum members will have ideas as well.

As far as support . . . 3 places (transom, bulkhead, bow) may be enough . . . 4 places along the keel would be better. 6 stands (3 each side) right under the chines should be fine. Just be sure to get everything set and secure before doing any demolition.

 

[Baylinerchuck]

Awesome drawings Ted. What a great resource!! Most impressive!

 

[tpenfield]

FWIW - Here is a quick video of the Sea Ray computer model that I made, plus the model of the suggested repair demolition.

I had not really used the software (SketchUp) much, but it seemed pretty straight forward once I started into it. :thumb:

 

[alldodge]

New toys are fun

 

[drewm3i]

Wow, you are the man! Those are invaluable man!

 

[Roady68]

I wish I could get that information for a 2000 Chaparral Sig 300. There was a leak on the board that the batteries and trim tab mount on. It allowed water to get to foam and now furthest starboard stringer looks wet. No rot. Yet. Everything else is dry. The decking is an easy fix. The stringer, I am not sure what I am going to do.

 

[drewm3i]

I wish I could get that information for a 2000 Chaparral Sig 300. There was a leak on the board that the batteries and trim tab mount on. It allowed water to get to foam and now furthest starboard stringer looks wet. No rot. Yet. Everything else is dry. The decking is an easy fix. The stringer, I am not sure what I am going to do.

Pull the motors and cut into it. Remove the foam and let the stringer dry out. Then reglass, refoam and be on your way. You may only have to pull one motor.

FYI, Roady is a good friend of mine from the Chaparral forum. He also bought a cruiser that needs some love. We have talked a lot about our planned repairs, so he isn't hi-jacking my thread .

 

[tpenfield]

Pull the motors and cut into it. Remove the foam and let the stringer dry out. Then reglass, refoam and be on your way. You may only have to pull one motor.

FYI, Roady is a good friend of mine from the Chaparral forum. He also bought a cruiser that needs some love. We have talked a lot about our planned repairs, so he isn't hi-jacking my thread .

We will help him too :thumb:

 

[drewm3i]

Update: I've secured a rental trailer, place to work, and blockers.

Now I need to start getting tools. Ted and others, can you make a list of what I'll need? I have nothing other than a drill, hole saws, mechanics tool set, vise grips, and electrical wiring stuff. Going to need saws, etc. Most of my tools will probably come from Harbor Freight because I'm cheap .

 

[alldodge]

Oscillating tool with round and straight blades, get two and you don't need to switch blades.
Wood chisels 3/4 and 1.5 inch, the more the merrier
Grinder with some flat flap disc wheels and grinder wheels

Most important
Tyvek suits, booties, hood socks, gloves, full face mask with respirator and gloves, Tape to seal booties and gloves
Shop vac with fine filter and have a water filter feed thru if you can

Sawzal is also a good item

 

[drewm3i]

Oscillating tool with round and straight blades, get two and you don't need to switch blades.
Wood chisels 3/4 and 1.5 inch, the more the merrier
Grinder with some flat flap disc wheels and grinder wheels

Most important
Tyvek suits, booties, hood socks, gloves, full face mask with respirator and gloves, Tape to seal booties and gloves
Shop vac with fine filter and have a water filter feed thru if you can

Sawzal is also a good item

Anything else? Any recommendations for a respirator?

 

[drewm3i]

I'm going to be using epoxy, not poly. Poly is too dangerous and stinky. Don't want nasty smells to linger in my sleeping berth. I also won't have to glass the stringers which will speed everything up...I will just bed them, tab them in with 1708 and then epoxy coat them.