Deck replacement on 1995 AS Explorer 245 - advice needed

[msteinkampf]

Demolition continues with opening up the deck and removing the rotted coring. Removal of the back corners was particularly tricky due the curves. I used the angle grinder and a Dremel tool with cutting blades.


I am hesitant to open up the deck at the helm since it is a small area that is fairly well supported around the edges. I bent a piece of electrical service grounding wire and started scraping out the coring. This area is the most severely rotted, and the material is coming out in shreds.


Here is the deck as open as I'm planning to do it. The coring around the livewell at the stern seems firm; it was isolated from the rest of the deck and apparently did not suffer any water intrusion.




Next step: Grinding off the resin lines and wood bits that are attached to the fiberglass.

[rhtrades]

did you cut out that piece of PVC pipe that connects the forward bilge to aft bilge?   or was it like that already (how it looks now)?   

[msteinkampf]

That’s what the pipes looked like when I removed the tank. I don’t plan to connect them because I want to keep the option of draining the tank compartment to the posterior bilge. I’m going to install plugs in the bilges to keep them from draining into the tank compartment while underway. Any water in the forward bilge will have to be removed by the pump there. There will always be a little water up there (presumably coming from the anchor locker and elsewhere), so I’ll probably pour in a cap of bleach or lemon cleaner occasionally. One day I’ll deal with that water more definitively, but that’s pretty low on the priority list.

M

[rhtrades]

Thanks for the info....keep posting photo's of your progress!

[msteinkampf]

I prepared the fiberglass layers for new coring by sanding down the resin nibs and plywood fragments with a random orbit sander using 60-grit sandpaper. A shop-vac hose attached to the sander did a good job of collecting the fiberglass dust. This picture shows what it looked like after the initial sanding was completed. Note that the outlines of the plywood squares are still visible - this is a very thin layer of wood that is completely imbedded in the resin; in some areas the glass fibers and wood fibers are intermixed. I’m not planning to remove this layer, but I will come back with an oscillating sander and an angle grinder with a flap-sanding wheel to finish off the edges and corners. There is no trace of the edge-grain balsa that was used around the edges of the core.


This is a ¾-inch-thick board laid against the cut line of the deck. My plan is to slip the new core between upper and lower layers of fiberglass, and it looks like I’ll need to use 5/8-inch or even ½-inch-thick material to achieve this. Although it’s hard to accurately measure the thickness of the old core material due to the water damage, it looks like it was nominal ¾-inch plywood, or about 23/32-inch thick.


I took this opportunity to cut some templates out of scrap cardboard. I’m not trying for an exact fit here but rather to get an idea of how much core material I will need to order.


Even though they were in decent shape, I decided to replace the old neoprene strips with PVC molding glued on with 3M 5200. There were some spots where the neoprene adhesive had failed, and that was a potential pathway for moisture to damage the metal in the future. I’m going to spend some time thoroughly cleaning the outside of the tank and touching up the paint with automotive primer or something similar.

[RickK]

My thoughts are that you'll be lamming over and up the sides a little bit to tie everything in securely. With that in mind I'd look for 5/8" and lam the bottom of wood with a layer of 1708 and the top with 2 layers.  You can do a test lam with scrap and set it to check thickness. I think the last upper layer could be an entire 3/4 oz CSM or 2 to tie it all in across the boat.

[msteinkampf]

I like the idea of a dry fit to test the install. I’ll do that after I sand the top layer of the deck.

[rhtrades]

looking great!  I used 5/8 plywood.  just make sure you let that epoxy resin absorb into whatever core you use before you put it down.  Balsa or any wood  will absorb alot so use plenty, let it soak in, then use more. 

I'm redoing my seams at the moment.  I am glassing over them in with long 1" strips.  imo, don't use any masking tape....It becomes very difficult to get off...

[msteinkampf]

Thanks for that tip. In my experience doing gel coat repair, I do use masking tape, but I sand off any gel coat overlying the tape before removing it. What kind of strips and resin are you using to cover the seams?

[rhtrades]

yeah I also use masking tape when gel coating....but I used masking tape to prepare the edges for applying the glass strips and resin.  Once that stuff dries on that masking tape its so hard to get that tape off.  I will have to lightly sand it off.  It would have been better to just wipe off any excess resin that spilled over with acetone and a towel.

I used Total Boat Epoxy Resin and Fast hardner.  5:1 ratio. (no thickener)  I think its pretty good and from what I read, very comparable to West Systems...slightly cheaper too.  For the glass strips, I used "woven" as opposed to "chopped strand"  I think it will definitely work as it appears to have adhered really well....I just have to prepare it now to be gel coated.   

[msteinkampf]

I took the tank home so I could clean and inspect it between trips to the boat shed. I found a few spots of corrosion underneath the rubber strips. This is the deepest one, a bit less than half-way through the metal.




I was planning to fill these in with J-B Weld, which I have on hand and is listed for use on aluminum. Should I be using something else?

[dbiscayne]

before coming up w a way to 'fix' those spots, I'd have the tank pressure tested. Very small amount of pressure is used and it needs to hold pressure to be sure you don't have any pin holes hiding somewhere. In the pic you sent, the furthest right corroded spot looks like it could have some pin holes? Or maybe thats just little black flecks of the neoprene?
If the pressure test passes then move on to protecting these spots. I've used JB Weld to glue a thin strip of anodized aluminum over sore spots, then coal tar epoxy or similar coating. Just be sure the prep gets it hospital clean.
This site has a good read on the different grades of aluminum, and a lot of cool stuff in general.
https://www.aircraftspruce.com/catalog/mepages/aluminfo.php

https://www.aircraftspruce.com/

[rhtrades]

I would just buy a poly tank....avoid any problems down the road.  you do not want to have to cut into that deck again after all that hard work.   

[msteinkampf]

D: That's the best reference I have encountered regarding aluminum alloys. Thanks for that. The black marks are indeed flecks of rubber, there are no pin holes going all the way through the metal. I agree that pressure testing is a good idea. I'm going to repair the pitting, test the tank, and then give it a final coating of ... something. Probably just some zinc primer, which seems to be what was used on it at the factory.

RH: If I can get the tank to pass a pressure test, I think it is worth saving, although I am going to make a final decision about that only I have inspected the tank's interior. I plan to convert the fuel tank compartment lid to one that can be removed without cutting (like Capt Bob's). I haven't been able to find any reference that shows how to do that, so if anyone has one, I would appreciate their sharing it. Seabob said that at the Genmar plant they would occasionally cut the deck to remove a fuel tank and then install cleats before reinstalling the lid, but he didn't provide any details about what they did after that. My guess is they just ground down the gelcoat, applied some glass reinforced filler, and then reapplied gelcoat. I'm going to try to do better than that.

M

[msteinkampf]

Grinding the fiberglass deck pieces continues. I found that a grinding wheel on my 4-inch angle grinder worked well on the underside of the top layer.


I cut some ½-inch – 5/8-inch spacers on my table saw to determine the proper thickness of coring material.


 A spacing of five-eighths of an inch resulted in a good match at the cut lines of the deck.