posted 11-06-2003 06:46 PM ET (US)        

No longer being encapsulated, will the foam dry out? Can I get the water to flow to the lowest point and vacuum it out if I hollow out an area for this purpose?

Would it be best to remove the foam and tank? I am leaning toward doing just that. Removal of the foam and tank, pressure testing the tank as well.

What is the best way to remove the foam? Large sections can be removed but how do I remove the residual foam stuck to the hull and tank.

What is the best type of foam to re-install?

posted 11-06-2003 09:46 PM ET (US)            

Lately there has been what I would call a movement to encourage boat builders to NOT use foam to encapsulate aluminum fuel tanks. The publishers of the journal Powerboat Reports have been using their editorial pages to make a case against building boats with aluminum tanks and foam encapsulation.

Their point of view is that use of foam encapsulation serves to retain moisture against the surface of aluminum tanks, and thereby increase the risk of corrosion of the tanks.

On the other hand, there are many, many Boston Whaler boats built with aluminum fuel tanks encapsulated in foam which have not experienced unreasonable rates of failure of the tanks. Any aluminum tank that is 15-20 years old is probably nearing the end of its leak-free lifespan and is due for some repairs or replacement.

How does one remove foam from around a tank? I think physical labor, scraping, etc., is the only way to get it out. Perhaps there is a solvent which could loosen the foam and not deteriorate the laminates. I don't know.

If one has gone to the effort to remove a fuel tank and clean out the fuel tank cavity, would refilling with foam be the best approach?

Were I in that situation I might consider alternatives. I have not seen first-hand how the tank actually sits in the cavity. Perhaps there might be room to support the tank using some stringers. You could make the stringers from a plastic material--say something like Star-board--or even from wood (if the wood were well sealed with several coats of epoxy). The goal would be to leave most of the tank surrounded by air, including the bottom panel, of course.

Inclusion of some plumbing and hoses to de-water the tank compartment might also be prudent. I would plan on using a pump that could self-prime and tolerate a high lift. This would allow the pump to be located outside of the fuel tank cavity itself.

Below I provide a hyperlink to an teaser for an interesting article for sale on the POWERBOAT REPORTS website regarding this topic:

posted 11-07-2003 09:40 AM ET (US)            

One possible thought, lay down / epoxy several starboard stringer into "dados" in the floor foam. Support the foam sidewalls with a box made of marine starboard and backfill with foam against foam. Epoxy and screw filler strips along the inner walls snug to the tank dimensions. Is their a type of liguid to solid type of shock absorbing material that could be used between the starboard and the tank to keep it secure? Attached hold-downs to the floor stringers and around the tank to secure. Haven't thought this out well, but seems reasonable.

Tom Clark, as our resident engineer and jack of construction trades might be able to weigh in on this a bit better. Tom?

posted 11-07-2003 12:03 PM ET (US)            

I don't have time right now for a full blown response. I'll try compose one this weekend. But for now let me point out some stuff we've talked about in the past here in the Forum.

There has actually been a LOT of discussion about fuel tanks and their replacement. A search will yield much useful information for you.

As Jim and Bob have discussed above, foaming in fuel tanks has long been common practice and one which has led to problems. Boston Whaler foamed in their aluminum (and plastic) fuel tanks for years but no longer does so. That should tell you something.

If it were me, I would NOT foam in the tank.

Be aware that your Guardian may have a more robust aluminum tank than what the recreational models received. What year if your Guardian? That may tell us what kind of tank you have. On new Guardians, thicker gauge aluminum and baffles are part of the fuel tank design.

posted 11-07-2003 07:50 PM ET (US)            

I am principally concerned with the waterlogged foam surrounding it.

posted 11-08-2003 07:14 PM ET (US)            

As far as separating the tank from the boat, I stuck a screwdriver into the foam until it bottomed and measured the depth (about 4 inches). I then broke a SAWSZALL metal cutting blade to just shy of the same depth. I mounted the blade into the recip saw and held the blade against the tank as I worked around the perimeter. Worked like a charm. The hardest part will be breaking the adhesive on the bottom of the tank without damaging the tank if you intend to re-use it. Since I was replacing the tank, I simply laid a 2x4 across the floor and used a crowbar under the vent tube, braced on the 2x4. It took me (270-lb.) standing and bouncing on the crowbar for the tank to break free. Didn't really damage the vent fitting much.

The problem with pressure testing the tank becomes plugging all the fittings and measuring the max 3 psi. Had a lot of trouble finding a gauge that had a center range that low. Even a 10 psi gauge is not accurate at that low of a pressure. Much more that 3 psi and you could deform the tank.

Good Luck

posted 11-10-2003 08:43 AM ET (US)            

I think Tom was correct in assuming the tank is a more heavy duty version as it will support my weight without even flexing. Appears quite strong.

posted 11-10-2003 10:41 AM ET (US)            

Since Whaler supposedly is no longer "foaming-in" their below-deck aluminum gas tanks, do we know what new methods they've adopted for securing the tank and supporting the deck surface?

I'm incredibly anxious to learn how they're now doing this, as I'm about to re-install a tank into a Guardian.

Could differences now exist between the Recreational and CGP lines in how the tanks are secured and deck supported?

Thanks.

posted 11-10-2003 01:41 PM ET (US)            

No sign of any moisture at all. So much for removing the foam and tank.....

Change of plans. I am going to pressure test the tank in place. If the tank proves to be sound, I will devise a plan that will allow for inspection of the cavity and access for evacuation of any water that may enter once the floor is re-installed.

I hope :-).

posted 11-10-2003 02:13 PM ET (US)            

How do you know the foam is dry "COMPLETELY"? By this I mean, you have no way of knowing if the core of the foam is saturated unless you cut into it, no?

I'm not trying to sell you on unnecessary work; I just want you to be sure things are as they appear to be. That's not always the case.

jxs226,

Whaler has not foamed in their tanks at least since 1997, maybe longer. The tanks just sit on pads and are bolted down. The newer hulls have the fuel tank cavity in the hull formed much more closely to the shape of the tanks (or vice versa). There is less need for foam to fill the excess void between tank and hull.

Larry,

I do not know how CGP installs their tanks. Why don't you send them an email and ask?

I do know that if they still foam in their tanks it is not simply by using the same foam as is used in the hulls. The problem they used to have is the foam that goes into the hull is much more dense than it would be if it were allowed to expand to its full size.

Whaler Unibond hulls typically have TWICE the volume of foam necessary to fill the hulls, but because it is constrained by the clamped-together steel molds, the foam achieves far greater density and strength.

posted 11-10-2003 02:55 PM ET (US)            

Tom,
I beat you to it :-) I just used a Milwaukee Self Feed drill bit of 2 1/4" in diameter and drilled out several test holes. Essentially removing most of the foam at the transom end of the cavity and in a few other locations.

I just found a small amount of ice (yes , it was cold here last night) at the very bottom of the cavity. So, it is not all gone, but close to it. I would assume, that too will be gone in a short time as this foam was saturated a few days ago.

I must say I am not as optimistic at this point due to another realization... I don't see how this area can be made water tight. The fill hose and vent line chase is such that water will feed into this area no matter how well the seam is sealed. There is a drain from the gas tank cavity that feeds into the bilge area but it is at a height that is even with the top of the tank. Looks as though water was not expected to be absorbed by the foam and that the water entering the tank cavity was expected to flow over the tank/foam and out to the bilge. Well, let me tell you, it doesn't work that way. Water saturates the foam and then excess water vacates the area. Oh boy!

So now what do I do? Re-foam and leave it as it has been for 15 years, or come up with a pump out system that can be utilized to remove the water on demand?

I would rather the pump set up but am concerned with the tank eventually leaking and posing an explosive hazard. :-(

What to do???

posted 11-10-2003 03:22 PM ET (US)            

You've discovered another feature of the Classic Whalers, the bilge area and fuel tank cavity are all connected to some degree. You cannot exclude water from around the fuel tank. This is why the foam is a bad idea. It will get wet.

I'm surprised by what you are reporting. Do I understand you correctly that the foam was formerly totally wet and now is nearly totally dry?! Even the completely wet foam from CSW is still somewhat wet a year later after sitting in my heated basement.

Your foam must have suffered severe cellular damage to be able to take on and then loose all that water.

I think your best bet is to remove the tank, clean things up and reinstall with some extra padding and not use any foam.

posted 11-10-2003 03:49 PM ET (US)            

The only other possibility is to use an explosion proof, self priming pump that can be externally mounted with just the suction hose below the floor.

posted 11-11-2003 12:16 PM ET (US)            

The foam used around the fuel tank is not some other type of foam. It is not intentionally an open cell variety. As I have said, it is the same polyurethane foam used in the hull except that it is free rise and thus not as dense. It is still closed cell foam so if Jason's has absorbed water it is because the cellular structure has broken down.

This should not come as a surprise based on our experience with CSW. We know that closed cell foam can break down and absorb water. Furthermore, and contrary to what has been reported elsewhere, the foam can absorb water without being forced into it by water pressure caused by running a hull at speed with a rupture of the hull skin. Obviously the foam surrounding Jason's fuel tank never had water "jetted" into it, it absorbed it.

Jason,

Where did this Guardian spend most of its life? Did it live in a climate that was subjected to severe freeze/thaw cycles?

Yes, if you do not use foam around your tank there will be water down there, but there already is. As Larry has pointed out, this is a very good reason to keep the drain plugs in and keep the bilge pumped out. I have always recommended keeping the bilge dry. The idea of leaving the plugs out for self-bailing purposes does not appeal to me especially in salt water given that you will effectively be soaking your fuel tank in a flooded compartment, foam or no foam.

You need to think of your fuel tank cavity as part of the bilge. That is what it really is. What about installing a drain tube at the bottom of the rear dam of the fuel tank cavity? That would allow the water from around the fuel tank to drain to the bilge sump and be dealt with by your bilge pump.

posted 11-11-2003 12:38 PM ET (US)            

How to install new tank: Foam it in... It's a tried and true method, and generally you get 15-20 years of good service out of this method. Exactly how often do you repower? Repowering is much more expensive than re-tanking! Few seem to flinch at repowering prices... A new 140gal tank from FMT was quoted at $1400. A pair of 150 4stroke Yamahas was quoted at $20k... Tanks are cheaper than a trailer!

posted 11-11-2003 01:41 PM ET (US)            

I don't think it gets too cold there...

As for considering the tank cavity as part of the bilge, that's fine but it is lower than the bilge and will not empty at least 60% of its' contents being the bilge drain is 8" higher than the lowest part of the gas tank cavity.

posted 11-14-2003 10:48 PM ET (US)            

I don't know If you have already got your fuel tank problems figured out. I have some photos of a pump system that I am using with a hand pump. It seems to work pretty well; both water and gas.

Let me know if you want me to E-mail them to you.

posted 11-18-2003 11:32 PM ET (US)            

I sent the pics last night let me know if they didn't show and I'll try something different.

posted 11-21-2003 06:56 PM ET (US)            

I have posted this a long time ago but will mention again what I did. Let me start by saying there may be better solutions to your problem but this was the solution I chose after much input. I had a 1988 18 guardian with the exact same situiation you mention.
I removed the foam and the tank. I then took the tank and sanded the entire exterior to roughen it and remove any existing corrosion. I then took epoxy and glass cloth and totally encapulated the tank with 2 layers of cloth and epoxy. the tank was put back into the cavity and foamed into place with the 2 part foam. I trimmed the foam even with the tank top and then with sand paper scratched the top of the tank around the perimeter and the sides of the cavity again to roughen them up. I then basiclly glassed the tank into the cavity with cloth and epoxy attempting to create a water tight seal around the perimeter of the tank. This would force any water entering the cavity to just run over the epoxied tank and out the back sump, never enter the actual cavity around the tank. To remove the tank and rework it may be a pain but basiclly I built a glass tank around the aluminum one so there may never be a need to remove it ( I know wish full thinking huh). Take it for what it is worth that is what I did. I have some pics if you would like them.

posted 11-21-2003 08:54 PM ET (US)            

I'm not going to glass the tank as it is a very solid and thick walled container. It is not corroded at all. This is in a Guardian 20" and appears to be a much thicker wall than I have seen before.

I am going to pressure test in place and re-foam if all is well. I will then paint the tank top and exposed foam with an Elastomeric roof paint. This will in effect seal the whole thing as you did and hopefully keep the water out. I also plan on foaming the gas fill and vent lines where they come up from the deck and enter the gunwale. There too it will be waterproofed.

I'll keep an eye on the area through the deck plates and if I see a problem, I'll sell it.... Hahahahahahaha! Just kidding of course. I am pretty confident this will suffice.

The floor is coming along. All plywood has been removed and I will be re-backing it starting tomorrow.

I'll keep you all posted.

posted 01-27-2004 11:40 AM ET (US)            

www.mityvac.com

posted 01-27-2004 03:36 PM ET (US)         

My guess is that a 20 year life span on a tank, or tank cover, was considered the right economic/cost containing decision at the time. Dougherty and others probably figured these same buyers would be buying a new Classic Whaler in the future (the 1990's). But as the ready supply of new models that we liked disappeared, we didn't, and instead decided to keep our existing Classic Whalers, or find used ones. Plus, a newer, younger almost cult following is developing besides, which would include many here, now interested in keeping these boats on the water for many more years. So the whole gas tank design decision making process is now being re-visited, with it's resultant shortcomings.