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Capt. Patrick, I am preping my B28 for an aluminum tank install. I have a couple of questions based on your tank install tips. I am getting a 190 gallon tank fabricated locally from 5052, 1/4 inch thickness. For those interested, cost is $1800.

1. use 4 lb density foam?

2. How do you prep the tank for coal tar? I've read the product info sheet on the ben-moore web site and they do not detail the aluminum prep work.

3. Orginal tank was mainly supported by by stringers. Should I add brackets attached to the stringers or is the foam sufficient? I plan on replacing the orginal ply under the tank with new ply fully glassed. That platform only spans 15 iches to 10 inches across the V. The stringer are 26 inches part.

4. Should I install a cross beam at aft end of the tank (stringer to stringer) to creat a box for foam retention or attach tank to aft engine compartment via fastners/brackets?

Thanks for your help.

Cpt. Pat can give you all the details of the prep, but I just scratched it down with 80 grit sandpaper, wiped with acetone, let it flash off, and then painted on the coal tar.

Its more like tar than epoxy. Avoid getting it in your hair. I was a blond prior to the application.

I would take a hard look at Interprotect from Interlux over the coal tar. It seems like a better coating designed just for our application. Just my 2 cents.

HL, maybe some of the B31 fossils can use the coal tar instead of grecian formula. So no chem etch or primer with coal tar? Any problem areas yet?

The fabricator recommended no coating at all, rather carefull install to ensure no static moisture points. He recommended PVC board supports under the tank. How did you install?

CaptBone--will check out the interlux, I like thier two part interthane products--real tuff stuff.

Thanks

Any protective coating on the tank is a good idea....but the guy that has built several tanks for me in the past tells me that aluminum tanks corrode from the inside long before the outside rots. He claims that water droppets in the fuel will settle on the bottom inside and pit a hole in the aluminum.

He repairs a bunch of them also, shorta the only game in town around here.

Urban legend???

Capt Patrick. Sorry for the first two questions. Your tips section anwers both those questions. Just need help on the structural questions if possible.

Scot, a coast guard report cites a bronze filing left inside the tank as a curprit that cause a hole. Seems like anything is possible when it comes to aluminum corrosion.

Wonder what the opinions are on bonding an aluminum tank. Haven't done any research on that yet.

You are absolutely CRAZY to consider not bonding your tank. Any spark woud be a very bad thing.

That said, when an AL tank is bonded to the rest of the boat it is very low on the galvanic scale. It will plate out to everything else, and it has a limited life.

Peter

Well, I did the coal tar trick on a aux. tank I dropped under the salon floor in place of the Hyena water tank. It sits on a plywood sheet, and the bilge water runs under the plywood. Mine has been in pert near 4 years of hard use and a year on the hard (maybe, not real sure).

Took it out last Summer and looked fine. Coating had a couple rub thru's on the corners from the hold down strap but otherwise was fine. Bottom and sides looked great.

I put that stuff on in a couple coats. It ends up being a considerable coating. Not like paint. More like that rubber tool dip stuff.

I am also replacing my tank right now and had a question about the installation of the new tank. I cut out the plywood bottom during the removal(more like destruction) of the old tank and intend on using coal tar on the new tank. I am up in the air b/w the following options on the reinstall.

1. Foam the new tank in as Capt. Pat has on the building link. If I do this, the new tank would forever be in contact with bilge water since the aft bilge suction is pretty low. If I set the tank high enough to be out of the bilge, it would be smaller and less capacity than the original (not where I want to be). Is the coal tar that good that this is not a problem?
2. Reinstall composite along the bilge where old plywood was, but glass it into fwd bulkhead and wrap it up the aft end of the tank such that the tank is isolated from the bilge.

Any insight is appreciated. Either way, I will coal tar the new tank and foam it in. Thanks in advance for your help.

Matt

Bottom of my tank is contoured to the hull except for the very base which I made flat for aproximately 10-12 inches, so when installed it is several inches off the keel and would allow water to flow underneath. The tank is also sitting on 1/2" strip to keep off hull side. The hull bottom has that water channel which should allow water to flow underneath the tank compartment. With the base of tank cut short and sitting on strips I was able to increas capacity form 160 to 220 gallons. It's foamed in too, for support and to secure.

After much discussion with an aluminum boat fabricator and a local shipwright, I've decide how to install. Both recommended no coating, rather allow air flow around the tank and insolate from any wood structure. I am almost done with my drawings in Visio if anyone wants them. I designed the tank to simplify fabrication, retain same capacity (190) and ease of install. The basic idea is to rest the tank on the stringers via a 2 inch angle welded on the side. The tank is wider to creat an intferenence fit with between the stinger and angle. On the stringer I will glue compressible 3/4" foam on top and inside the stringer for the tank weight and side to side movement. In addition, I will fasten the tank on each stringer at the rear of the tank and the forward bulkhead via tabs. I will keep an inch of clearance between the tank and the bulkhead. Side note: Power boat reports fails any boat with an aluminum tank foam in place.

Rick,

What year is your B28? Mine is a 1975= 165 gals.

Just wondering how you get the extra fuel with basicly the same hull!

'83, it came with a 190. I looked at an older 28 and it seemed like the aft engine bulkhead was more forward than mine. But basically just need to add bigger saddles on sides.

Rick,

Thanks for the reply.