Deck replacement on 1995 AS Explorer 245 - advice needed

[RickK]

Looking good

[msteinkampf]

I cleaned off the tank bottom by applying Goo Gone and carefully scraping with a razor blade. My wife remarked how nice the bottom of the tank looked after I was done, but the adhesive wouldn’t come off in two places. More careful inspection of those areas revealed that this tank had been repaired at some point in the past (Figure). Now it becomes clear why the deck had been cut open.

Tank bottom. Note remaining adhesive (probably polyurethane), and a small aluminum fillet (arrow). The paint color was slightly different in this area.


At this point I figured it would be unwise to proceed without performing a static pressure test on this tank. In most online discussions I read, the boat owner takes the tank (or the boat) to a facility for this testing, but I would strongly encourage anyone reading this to do this test yourself if you have access to an air compressor, if only to be able to confirm that your boatyard is doing the test properly (more about this later). At the very least, I suggest you read the definitive reference on pressure testing and just about all things related to marine fuel systems here (the description of static pressure testing starts on page 100): https://www.uscgboating.org/assets/1/AssetManager/ABYC.1002.01.pdf. If you want to watch a YouTube video about pressure testing, this is the best one I found: https://www.youtube.com/watch?v=QDDDjp-4cZ0&ab_channel=SVCSkallywags. Most of the other videos (and frankly, most of the info I found on online discussion boards) had some significant limitations or errors. Here is the setup I used, which utilizes an inexpensive gauge obtained on Amazon and some brass fittings that I bought at my local hardware store.

My pressure testing apparatus. Note that the ABYC protocol for static pressure testing requires a gauge with a maximum range no greater than three times the test pressure, so for a pressure of 3.5 psi, a 10 psi gauge is the maximum allowed. The minimum test pressure per ABYC is 3 psi; the manufacturer of this tank originally tested it to 4 psi.


I connected my testing apparatus, and after turning my air compressor down to about 10 psi, I slowly inflated the tank to 3.5 psi. I immediately got an unpleasant surprise, as the pressure fell as soon as I closed the pressure valve. One of the fuel line valves was audibly leaking through the lumen of the valve and I couldn’t maintain pressure. I switched the testing line over to the bad valve, and although there was still a slow leak at the valve handle, I found that I could maintain pressure without difficulty. One lesson I learned here was being able to maintain pressure doesn’t rule out the presence of a leak.

A slow leak in the fuel line valve. This fitting will need to be replaced. (The fuel sender hole was sealed with a scrap of aluminum for this test.)


After spraying the entire tank with soapy water, I found another leak, right at the bottom of tank at the stern end.

Another leak.



Reaming out this hole with my pocket knife confirmed that the corrosion had occurred on the inside of the tank, probably from water that had collected at the bottom of the tank when the boat has stored with the bow up.

The hole was more apparent after the corroded area was reamed out.


Next: repair or replace?

[Ulysses485]

My vote would definitely be to replace. It’s a large up front coat but the safety, peace of mind, and longevity that you’ll get out it will far outweigh the potential savings from patching it. If there is internal damage, it will make it nearly impossible to repair from the outside properly. I’m not sure how the poly Moeller tanks hold up in larger deeper vee hulls but might be something to check into. Just my $.02

[msteinkampf]

There are some good reasons why I should replace this tank: (1) Below-deck tanks are hard to service, especially larger ones, and new tanks are less likely to develop problems in the near future than ones that have been repaired; (2) I could have a new tank fabricated a bit narrower than the original, making the deck repair easier; (3) I’m going to have to replace the fuel sender gasket and one of the fuel valves, and there is no telling how much longer the sender will continue to function; (4) the manufacturer of this tank recommends against repairing it (no surprise there).

That being said, I’m going to repair the tank. I’m planning to fix the deck so I can pull the tank out without cutting fiberglass, and I’m going to replumb the bilge drains to minimize the chance of any tank problems in the future. I got the name of a welder from a company that repairs fuel tankers, and he agreed to do the repair. I decided to have him fill in the pitted areas, too. Here is how the repair looked when he was done.

A plate of scrap aluminum has been welded over the hole. Note the rivet in the center of the plate – ouch! The welder claimed he hadn’t noticed that.


The welder drilled out the rivet and filled in the hole while I waited. He then pressure tested his repair by having his assistant hold a rag over the fuel sender hole while he blew air through one of the fuel valves by touching his air compressor hose (with pressure set to 100 psi) to the end of the fuel valve – no fancy testing gear needed! (I repeated the pressure test when I got the tank home.)
 
In preparation for applying PVC strips to the bottom of the tank, I ground down any aluminum fillets that looked like they would be covered by the strips. I then sprayed on some automotive zinc primer followed by some clear lacquer (it’s what I had in my spray can inventory). Here is what it looked like after all this.


Next step: applying the PVC strips.

[msteinkampf]

I had to move the tank from the hot garage to the cool basement because daytime temperatures were exceeding the recommended maximum for application of the 3M 5200. I turned off the basement dehumidifier, since 5200 is moisture-cured and the recommended humidity is at least 50%. Here's how the tank looked after I was done. This task required two 10-ounce cartridges. The blue painter's tape is being used to keep the PVC strips in place while the adhesive sets up.



Twelve hours after application, the 5200 remains sticky and the strips can still be moved a bit, but the tape is holding them in place. The manufacturer lists the tack-free time of 5200 as 48 hours with full cure at 7 days.

[Capt. Bob]

Indeed, 5200 takes a long time to fully cure, even in Florida heat and humidity.

Lookin' good.

[RickK]

Came out great 

[msteinkampf]

With the 5200 curing, it was time to start thinking about how to reinstall the tank. In the photo below, on the left is a piece of cardboard that approximates the cross section of the tank. Note how rubber strips applied to the bulkheads contact the tank all the way down the sides to the lower edges (arrows). The photo on the right shows my son grinding down the aluminum fillets that filled areas of corrosion. Most of the fillets (and areas of corrosion) are on the very bottom of the tank, but one (as indicated by the arrow) is on an edge that was in contact with a rubber bulkhead strip. Clearly, running rubber strips all the way down the bulkheads promotes corrosion near the bottom of the tank where the strips get wet. I won’t be doing that again.

[msteinkampf]

Another issue I am struggling with is how to drain the tank compartment. At present, there is one PVC pipe at the bow end that connects to the anterior bilge compartment, and another pipe at the stern for drainage to the bilge at the transom. I believe Capt. Bob plugged those pipes from inside the tank compartment, but I’ve seen rebuilds where those two pipes were connected so that water from the anterior bilge can drain directly to the transom. Apparently, it takes quite a bit of bow-up angle to get the anterior compartment to drain like that, but one might achieve that angle when the boat is getting up on plane. Since I have removed the tank and the platform that supports it, I could install a connection without much difficulty. What I don’t like about that setup is it leaves the tank compartment itself without any drainage. Ideally, I would like to run a pipe under the tank platform to connect the anterior and posterior bilge compartments and install a second drainpipe at the stern of the tank compartment that I could plug or open as needed. However, I don’t know how to accomplish that. When I run a coat hanger through the pipe at the stern of the tank compartment, it feels like the pipe is about 12 inches long. Any advice about this would be appreciated.

M

[msteinkampf]

I've been putting off trying salvage the fuel compartment non-skid for a while, but with the recent purchase of some Coosa board and the arrival of some supplies from Jamestown Distributors, it was time. A previous owner had glued the nonskid to some plywood with a polyurethane adhesive. After an unsuccessful attempt to soften the adhesive with acetone, I sprung for a pricey can of DeBond (currently $35.70 for a 10 ounce can on Amazon). It does work, but I found that some effort is still needed to get the surfaces to separate - spray the glue with DeBond, exert some traction with a 1x4 board, and repeat until done (see photo below). I used a long piece of 1/8-inch thick steel with the end ground down to a chisel point to help the process along. Most of the DeBond was used up on this. After the gel coat and underlying fiberglass was peeled off, I removed the adhesive with a sharp chisel.

[RickK]

You already know this but you can use the plywood as a template but I would recommend beveling the edges of the coosa at 45 degrees to facilitate bending the 1708 over the edges. That may require cutting the coosa about 1/2" smaller all around. Are you using epoxy?  That would really stiffen this up.

[msteinkampf]

Thanks for the advice. Yes, I'm going to be using epoxy for this part of the project, along with 1/2-inch Coosa Bluewater 20 (I wanted the 26, but my local supplier doesn't carry that grade in 1/2-inch). I plan to dress the edges of the Coosa with a router using a roundover bit and then laminate the board with 1708 to the desired thickness before attaching the nonskid with epoxy.

[rhtrades]

once you have that piece of non-skid all epoxied back in, i strongly recommend glassing over the seams or else they will print thru.  You would have to sand/grind gelcoat around the seams down to the fiberglass of course so that the glass and resin will adhere.     

[RickK]

Thanks for the advice. Yes, I'm going to be using epoxy for this part of the project, along with 1/2-inch Coosa Bluewater 20 (I wanted the 26, but my local supplier doesn't carry that grade in 1/2-inch). I plan to dress the edges of the Coosa with a router using a roundover bit and then laminate the board with 1708 to the desired thickness before attaching the nonskid with epoxy.

I would use a skill saw and tilt the blade to 45 degrees.
Here is an example of my rebuild of a casting deck hatch re-coring. A good tool to have if you're going to be doing a bit of this is a digital scale. Cut and weigh the cloth and divide the weight by 3 to figure out the amount of resin/hardener.
Cut the coosa, bevel it and then rough cut the 1708. Fold up the layers of cloth and weigh them. Mine weighed 49.3 oz but I rounded up to 56 oz since I knew I have other stuff to use the resin on, like make some thickened resin to trowel the backer to the lid.


The do a wet on wet of the lams of cloth

[msteinkampf]

Thanks for the formula. I'm not sure about cutting the Coosa at 45 degrees, though. I want to reinstall the fuel tank compartment hatch to be removable in the future, like Capt Bob's. For that, I was planning to fabricate a lip around the edge of the compartment (using either fiberglass or aluminum) that the hatch would rest on. I don't see how cutting a 45-degree angle on the hatch cover would help with that design.

M